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Sample records for radiation photoemission study

  1. Molecular photoemission studies using synchrotron radiation

    International Nuclear Information System (INIS)

    Truesdale, C.M.

    1983-04-01

    The angular distributions of photoelectrons and Auger electrons were measured by electron spectroscopy using synchrotron radiation. The experimental results are compared with theoretical calculations to interpret the electronic behavior of photoionization for molecular systems

  2. Photoemission studies of clean and adsorbate covered metal surfaces using synchrotron and uv radiation sources

    International Nuclear Information System (INIS)

    Apai, G.R. II.

    1977-09-01

    Photoemission energy distribution experiments on clean metal and adsorbate-covered surfaces were performed under ultrahigh vacuum conditions by using x-ray and ultraviolet photon sources in the laboratory as well as continuously-tunable, highly polarized synchrotron radiation obtainable at the Stanford Synchrotron Radiation Laboratory (SSRL). Studies focused on two general areas: cross-section modulation in the photoemission process was studied as a function of photon energy and orbital composition. Sharp decreases in intensity of the valence bands of several transition metals (i.e., Ag, Au, and Pt) are attributed to the radial nodes in the respective wave functions. Adsorbate photoemission studies of CO adsorbed on platinum single crystals have demonstrated a very high spectral sensitivity to the 4sigma and (1π + 5sigma) peaks of CO at photon energies of 150 eV. Angle-resolved photoemission allowed determination of the orientation of CO chemisorbed on a Pt (111) or Ni(111) surface. Prelinimary results at high photon energies (approximately 150 eV) indicated scattering from the substrate which could yield chemisorption site geometries

  3. Photoemission spectroscopy using synchrotron radiation

    International Nuclear Information System (INIS)

    Kobayashi, K.L.I.

    1980-01-01

    It is an epoch making event for photoemission spectroscopy that the light sources of continuous wavelength from vacuum ultra-violet to X-ray region have become available by the advent of synchrotron radiation. Specifically the progress after stable intense light has become obtainable from storage rings is very significant. One of the features of these synchrotron radiation is its extreme polarization of radiating pattern. Though the elementary processes of photoemission out of solids are the basic themes, phenomenalistic 3-stage model is usually applied to the analysis of experiments. In this model, the process of photoemission is considered by dividing into three stages, namely the generation of photoelectrons due to optical transition between electron status -- the transportation of photoelectrons to solid surfaces -- breaking away from the surfaces. The spectrometers, the energy analyzers of photoelectrons, and sample-preparing room used for photoemission spectroscopy are described. Next, energy distribution curves are explained. At the end, photoelectron yield spectroscopy, CFS (constant final energy spectroscopy) and CIS (constant initial energy spectroscopy), Auger yield and interatomic Auger yield, the determination of surface structure by normal emission CIS, and surface EXAFS (extended X-ray absorption fine structure) are described. As seen above, the application specifically to surface physics is promising in the future. (Wakatsuki, Y.)

  4. Interfacial electronic structure of Na deposited on rubrene thin film studied by synchrotron radiation photoemission

    International Nuclear Information System (INIS)

    Wei, Ching-Hsuan; Cheng, Chiu-Ping; Lin, Hong-Cheu; Pi, Tun-Wen

    2015-01-01

    Graphical abstract: - Highlights: • Na deposited on rubrene had undergone three-stage development process via (1) atomic diffusion, (2) atomic incorporation in the surface region, (3) formation of a metallic film. • High resolution core-level photoemission was used to determine the location of the doped Na atoms, which is affiliated at the end position of the tetracene-like backbone. • Na metal was formed on the rubrene thin film. • Ionization potential of the organic molecule regulated with different Na doping concentration could be controllable and favorable in practical applications. - Abstract: The electronic structure of rubrene doped with various concentrations of Na was studied by synchrotron-radiation photoemission. Three stages of development were found with increasing Na concentration; Na penetrating deep into the organic film, followed by development of gap states, and ended with a metallic Na film. The charge transfer from Na to rubrene resulted in a vacuum-level shift. By doping Na into rubrene, we could control the IP of the organic molecule, which is favorable for application in organic semiconductor devices.

  5. Synchrotron radiation photoemission spectrum study on K3C60 film

    Institute of Scientific and Technical Information of China (English)

    李宏年; 徐亚伯; 鲍世宁; 李海洋; 何丕模; 钱海杰; 刘风琴; 奎热西·易卜拉欣

    2000-01-01

    K3C60 single crystal film was prepared on the cleaved (111) surface of C60 single crystal. Synchrotron radiation angle-resolved photoemission spectra were measured at normal emission with sample temperature at - 150K. Up to four subpeaks of LUMO-derived band were observed. These sub-peaks exhibit distinct energy dispersions which resemble in general the theoretical ones calculated for K3C60 at low temperature with the so-called one-dimensional disordered structure. But there is large deviation of experimental sub-band intervals from the theoretical values. This result is meaningful for the studies of the physical properties of alkali-doped C60 solids, e.g. the mechanism for superconductivity.

  6. Synchrotron-radiation photoemission study of CdS/CuInSe2 heterojunction formation

    International Nuclear Information System (INIS)

    Nelson, A.J.; Gebhard, S.; Rockett, A.; Colavita, E.; Engelhardt, M.; Hoechst, H.

    1990-01-01

    Synchrotron-radiation soft-x-ray photoemission spectroscopy was used to investigate the development of the electronic structure at the CdS/CuInSe 2 heterojunction interface. CdS overlayers were deposited in steps on single-crystal p- and n-type CuInSe 2 at 250 degree C. Results indicate that the CdS grows in registry with the substrate, initially in a two-dimensional growth mode followed by three-dimensional island growth as is corroborated by reflection high-energy electron-diffraction analysis. Photoemission measurements were acquired after each growth in order to observe changes in the valence-band electronic structure as well as changes in the In 4d, Se 3d, Cd 4d, and S 2p core lines. The results were used to correlate the interface chemistry with the electronic structure at these interfaces and to directly determine the CdS/CuInSe 2 heterojunction valence-band discontinuity and the consequent heterojunction band diagram. These results show that the Katnani-Margaritondo method is unreliable in determining offsets for heterojunctions where significant Fermi-level pinning may occur and where the local structure and chemistry of the interface depends strongly on the specific heterojunction

  7. Preparation of solid-state samples of a transition metal coordination compound for synchrotron radiation photoemission studies

    CERN Document Server

    Crotti, C; Celestino, T; Fontana, S

    2003-01-01

    The aim of this research was to identify a sample preparation method suitable for the study of transition metal complexes by photoemission spectroscopy with synchrotron radiation as the X-ray source, even in the case where the compound is not evaporable. Solid-phase samples of W(CO) sub 4 (dppe) [dppe=1,2-bis(diphenylphosphino)ethane] were prepared according to different methods and their synchrotron radiation XPS spectra measured. The spectra acquired from samples prepared by spin coating show core level peaks only slightly broader than the spectrum recorded from UHV evaporated samples. Moreover, for these samples the reproducibility of the binding energy values is excellent. The dependence of the spin coating technique on parameters such as solvent and solution concentration, spinning speed and support material was studied. The same preparation method also allowed the acquisition of valence band spectra, the main peaks of which were clearly resolved. The results suggest that use of the spin coating techniqu...

  8. Effect of phase formation on valence band photoemission and photoresonance study of Ti/Ni multilayers using synchrotron radiation

    International Nuclear Information System (INIS)

    Bhatt, Pramod; Chaudhari, S.M.

    2006-01-01

    This paper presents investigation of Ti-Ni alloy phase formation and its effect on valence band (VB) photoemission and photoresonance study of as-deposited as well as annealed Ti/Ni multilayers (MLs) up to 600 deg. C using synchrotron radiation. For this purpose [Ti (50 A)/Ni (50 A)]X 10 ML structures were deposited by using electron-beam evaporation technique under ultra-high vacuum (UHV) conditions. Formation of different phases of Ti-Ni alloy due to annealing treatment has been confirmed by the X-ray diffraction (XRD) technique. The XRD pattern corresponding as-deposited ML sample shows crystalline nature of both Ti and Ni deposited layers, whereas 300 deg. C annealed ML sample show solid-state reaction (SSR) leading to amorphization and subsequent recrystallisation at higher temperatures of annealing (≥400 deg. C) with the formation of TiNi, TiNi 3 and Ti 2 Ni alloy phases. The survey scans corresponding to 400, 500 and 600 deg. C annealed ML sample shows interdiffusion and intermixing of Ni atoms into Ti layers leading to chemical Ti-Ni alloys phase formation at interface. The corresponding recorded VB spectra using synchrotron radiation at 134 eV on as-deposited ML sample with successive sputtering shows alternately photoemission bands due to Ti 3d and Ni 3d, respectively, indicating there is no mixing of the consequent layers and any phase formation at the interface during deposition. However, ML samples annealed at higher temperatures of annealing, particularly at 400, 500 and 600 deg. C show a clear shift in Ni 3d band and its satellite peak position to higher BE side indicates Ti-Ni alloy phase formation. In addition to this, reduction of satellite peak intensity and Ni 3d density of states (DOS) near Fermi level is also observed due to Ti-Ni phase formation with higher annealing temperatures. The variable photon energy VB measurements on as-deposited and ML samples annealed at 400 deg. C confirms existence and BE position of observed Ni 3d satellite

  9. Scanning photoemission microscopy with synchrotron radiation

    Science.gov (United States)

    Ade, Harald W.

    1992-08-01

    Progress in photoemission spectro-microscopy at various synchrotron radiation facilities is reviewed. Microprobe devices such as MAXIMUM at the SRC in Wisconsin, the X1-SPEM at the NSLS at BNL, as well as the ellipsoidal ring mirror microscope at DESY in Hamburg, recorded first images during the last few years. The present status of these devices which achieve their lateral resolution by focusing X-rays to a small spot is the primary focus of this paper, but work representing other approaches to spectro-microscopy is also discussed.

  10. Activation of binary Zr-V non-evaporable getters: synchrotron radiation photoemission study

    International Nuclear Information System (INIS)

    Matolin, V.; Dudr, V.; Fabik, S.; Chab, V.; Masek, K.; Matolinova, I.; Prince, K.C.; Skala, T.; Sutara, F.; Tsud, N.; Veltruska, K.

    2005-01-01

    Zr-V alloy getter films were prepared on stainless steel substrates by magnetron sputtering. The thermal activation behavior of these getters was investigated by synchrotron radiation photoelectron spectroscopy using photon excitation energies of 600, 250 and 73 eV. Depth resolved results were compared to the results of the SIMS profiling. The measurements confirmed the disappearance of the superficial oxide layer covering the air-exposed Zr-V surfaces via its progressive reduction during the thermal activation. The depth sensitive results showed that the activated getter surface is covered by a residual zirconium sub-oxide

  11. Photoemission studies of mixed valent systems

    International Nuclear Information System (INIS)

    Parks, R.D.; Raaen, S.; denBoer, M.L.; Williams, G.P.

    1984-01-01

    Photoemission spectroscopy has been used to study a number of aspects of the mixed valent state (corresponding to non-integral 4f occupation) in rare earth systems. Deep core photoemission (e.g., from 3d or 4d levels) allows the measurement of the 4f occupancy and surface valence shifts, and, as well, the indirect measurement of the effect of solid state environment on the energy of hybridization between 4f electrons and conduction electrons. 4f-Derived photoemission has been used to study surface valance and chemical shifts and to infer the nature of the mixed valent ground state. A combination of 4f-derived photoemission and add-electron spectroscopy provides a measurement of the rf Coulomb correlation energy, an important parameter in the mixed valent problem. A review of these approaches will be presented, with emphasis on Ce-based systems, whose behavior falls outside the usual description of 4f-unstable systems

  12. Photoemission studies of semiconductor nanocrystals

    International Nuclear Information System (INIS)

    Hamad, K.S.; Roth, R.; Alivisatos, A.P.

    1997-01-01

    Semiconductor nanocrystals have been the focus of much attention in the last ten years due predominantly to their size dependent optical properties. Namely, the band gap of nanocrystals exhibits a shift to higher energy with decreasing size due to quantum confinement effects. Research in this field has employed primarily optical techniques to study nanocrystals, and in this respect this system has been investigated extensively. In addition, one is able to synthesize monodisperse, crystalline particles of CdS, CdSe, Si, InP, InAs, as well as CdS/HgS/CdS and CdSe/CdS composites. However, optical spectroscopies have proven ambiguous in determining the degree to which electronic excitations are interior or surface admixtures or giving a complete picture of the density of states. Photoemission is a useful technique for understanding the electronic structure of nanocrystals and the effects of quantum confinement, chemical environments of the nanocrystals, and surface coverages. Of particular interest to the authors is the surface composition and structure of these particles, for they have found that much of the behavior of nanocrystals is governed by their surface. Previously, the authors had performed x-ray photoelectron spectroscopy (XPS) on CdSe nanocrystals. XPS has proven to be a powerful tool in that it allows one to determine the composition of the nanocrystal surface

  13. Growth of metastable fcc Mn thin film on GaAs(001) and its electronic structure studied by photoemission with synchrotron radiation

    International Nuclear Information System (INIS)

    Chen Yan; Dong Guosheng; Zhang Ming

    1995-01-01

    The epitaxial growth of metastable fcc Mn thin films on GaAs(001) surface has been achieved at a substrate temperature of 400 K. The development of the fcc Mn thin films as a function of coverage is studied by photoemission with synchrotron radiation. The electron density of states below the Fermi edge of the fcc Mn phase is measured. A significant difference of the electronic structures is observed between the metastable fcc Mn phase and the thermodynamically stable α-Mn phase. Possible mechanisms are proposed to interpret the experimental result

  14. Thickness-dependent change in the valence band offset of the SiO{sub 2}/Si interface studied using synchrotron-radiation photoemission spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Toyoda, S., E-mail: toyoda.satoshi.4w@kyoto-u.ac.jp; Oshima, M. [Department of Applied Chemistry, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656 (Japan)

    2016-08-28

    We have studied the thickness-dependent change in the valence band offset (VBO) of the SiO{sub 2}/Si(001) interface using synchrotron-radiation photoemission spectroscopy with soft and hard X-rays. The SiO{sub 2}-film thickness (T{sub ox}) and X-ray irradiation time (t{sub irrad}) were systematically parameterized to distinguish between the “intrinsic” T{sub ox} effects in the VBOs and the “extrinsic” differential charging phenomena in SiO{sub 2} films on Si substrates. The results revealed that at a spontaneous time (t{sub irrad} ≈ 5 s) that suppresses the differential charging phenomena as much as possible, the experimental VBO abruptly increases as a function of T{sub ox} and gradually saturates to the traditional VBO value range determined by the internal photoemission and photoconduction measurements. This effect is not attributed to the differential charging phenomena, but rather it is attributed to the “intrinsic” T{sub ox}-dependent change in the VBO. The two possible physical behaviors include electronic polarization and image charge. We have derived the electronic polarization contribution from experimental data by carefully describing the effects of the long-range image charges based on the classical dielectric-screening model.

  15. Optical and photoemission studies of lanthanum hydrides

    International Nuclear Information System (INIS)

    Peterman, D.J.; Peterson, D.T.; Weaver, J.H.

    1980-01-01

    The results of optical absorptivity and photoemission measurements on lanthanum hydrides, LaH/sub x/ (1.98 less than or equal to x less than or equal to 2.89) are reported. The low energy (hν less than or equal to 0.5 eV) optical features in LaH/sub x/ are attributed to the filling of octahedral sites. Higher energy interband absorption involves states within the d-band complex, analogous to other dihydrides. As x increases above 2.0, the optical features change rapidly due to the increase in the number of occupied octahedral sites. Various band structure studies suggest that LaH 3 might be a semiconductor. Photoemission results show that as x increases, the d-derived states at E/sub F/ are drawn down and that for LaH 2 89 only very weak valence band emission is observed. The hydrogen-derived bonding bands are shown centered approx. 5 eV below E/sub F/. Observed chemical shifts in the La 5p/sub 1/2 3/2/ cores are discussed for 1.98 less than or equal to x less than or equal to 2.89

  16. Photoemission studies using laboratory and synchrotron sources

    International Nuclear Information System (INIS)

    Phase, D.M.

    2012-01-01

    Synchrotron radiation sources, providing intense, polarized and stable beams of ultra violet soft and hard X-ray photons, are having great impact on physics, chemistry, biology materials science and other areas research. In particular synchrotron radiation has revolutionized photoelectron spectroscopy by enhancing its capabilities for investigating the electronic properties of solids. The first Indian synchrotron storage ring, Indus- 1 is in operation at RRCAT, Indore. The UGC-DAE CSR with the help of university scientist had designed and developed an angle integrated photoelectron spectroscopy (PES) beamline on this 450 MeV storage ring. A storage ring of this kind is most suitable for investigation in the energy range from few electron volts to around five hundred electron volts. In this lecture we will describe the details of PES beamline and its experimental station. Till date the different university users carried out photoemission measurements on variety of samples. Some of the spectra recorded by users will be presented in order to show the capability of this beamline. In the later part we will report a review of our recent research work carried out on dilute magnetic thin films using this beamline. (author)

  17. Studies of magnetism and exchange scattering in solids using synchrotron radiation and spin polarized photoemission. Final technical report, June 1, 1981-May 31, 1984

    International Nuclear Information System (INIS)

    Rothberg, G.M.

    1984-01-01

    Progress has been made toward developing Spin Polarized EXAFS (SPEXAFS) as a technique for studying magnetism in solids. The first observations have been made of EXAFS by means of photoemission with sufficient data to permit a traditional Fourier-transform analysis of atomic structure. Some of the advantages of photoelectron detection of EXAFS are: (1) vuv light may be used thereby extending greatly the useable range of photon energies; (2) the number of elements that may be studied for surface EXAFS is increased; (3) the possibility exists for measurements that cannot be done in other ways. In addition to its intrinsic interest, this result is crucial to the study of the spin dependence of EXAFS. These measurements were carried out on the vuv storage ring at the National Synchrotron Light Source. Data obtained on the spin dependence of EXAFS in MnF 2 at room temperature tentatively show dependence of the Mn absorber atom phase shift on the exchange interaction within the absorber atom. This effect has not been discussed theoretically. Preliminary observations have been made of the Fano resonance in Mn 3d photoemission at the 3p to 3d threshold

  18. Inner-shell photoemission from atoms and molecules using synchrotron radiation

    International Nuclear Information System (INIS)

    Lindle, D.W.

    1983-12-01

    Photoelectron spectroscopy, in conjunction with synchrotron radiation, has been used to study inner-shell photoemission from atoms and molecules. The time structure of the synchrotron radiation permits the measurements of time-of-flight (TOF) spectra of Auger and photoelectrons, thereby increasing the electron collection efficiency. The double-angle TOF method yielded angle-resolved photoelectron intensities, which were used to determine photoionization cross sections and photoelectron angular distributions in several cases. Comparison to theoretical calculations has been made where possible to help explain observed phenomena in terms of the electronic structure and photoionization dynamics of the systems studied. 154 references, 23 figures, 7 tables

  19. Valence band photoemission studies of clean metals

    International Nuclear Information System (INIS)

    Wehner, P.S.

    1978-04-01

    The application of Angle-Resolved Photoelectron Spectroscopy (ARPES) to crystalline solids and the utilization of such studies to illuminate several questions concerning the detailed electronic structure of such materials, are discussed. Specifically, by construction of a Direct Transition (DT) model and the utilization of energy-dependent angle-resolved normal photoemission in the photon energy range 32 eV < or = hν < or = 200 eV, the bulk band structure of copper is experimentally mapped out along three different directions in the Brillouin Zone; GAMMA to K, GAMMA to L, and GAMMA to X. In addition, various effects which influence the obtainable resolution in vector k-space, namely, thermal disorder, momentum broadening, and band mixing, are discussed and are shown to place severe limitations on the applicability of the DT model. Finally, a model for Angle-Resolved X-ray Photoelectron Spectroscopy (ARXPS) based on the symmetry of the initial-state wavefunctions is presented and compared to experimental results obtained from copper single crystals

  20. Photoemission study of K on graphite

    NARCIS (Netherlands)

    Bennich, P.; Puglia, C.; Brühwiler, P.A.; Nilsson, A.; Sandell, A.; Mårtensson, N.; Rudolf, P.

    1999-01-01

    The physical and electronic structure of the dispersed and (2×2) phases of K/graphite have been characterized by valence and core-level photoemission. Charge transfer from K to graphite is found to occur at all coverages, and includes transfer of charge to the second graphite layer. A rigid band

  1. Experiments recently carried out on the photoemission station at Beijing Synchrotron Radiation Facility

    International Nuclear Information System (INIS)

    Kurash Ibrahim; Wu Ziyu; Qian Haijie; Zhang Jing; Abbas, M.I.; Chen Zhigang; Su Run; Liu Fengqin

    2003-01-01

    With a sustained and steady operation of the photoemission station at Beijing Synchrotron Radiation Facility, users from different research fields have carried out their investigation on the electronic structure of metal surface-interface, metal doped fullerene as well as colossal magneto-resistance materials utilizing different experimental modes provided by the photoemission station. In this paper authors would present some representative experimental results obtained on the station

  2. Synchrotron radiation photoemission study of interface formation between MgO and the atomically clean In{sub 0.53}Ga{sub 0.47}As surface

    Energy Technology Data Exchange (ETDEWEB)

    Chauhan, Lalit; Hughes, Greg [School of Physical Sciences, Dublin City University, Glasnevin Dublin 9 (Ireland)

    2014-02-15

    The evolution of interface formation between MgO and the atomically clean In{sub 0.53}Ga{sub 0.47}As is studied by synchrotron radiation based photoemission. The deposition of MgO in a step wise fashion on the decapped In{sub 0.53}Ga{sub 0.47}As surface at room temperature results in the growth of an ultrathin interfacial oxide layer. Subsequent thermal annealing at 400 C led to the reduction of the As and In oxides and the appearance of a Ga oxide component. The deposition of metallic Mg resulted in the further removal of the interfacial oxide and the out diffusion of In into the overlayer indicating severe disruption of the interface. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  3. Photoemission spectroscopy study of a multi-alkali photocathode

    CERN Document Server

    Ettema, A R H

    2000-01-01

    In this paper a photoemission study of the highest core levels of the elements and the electron escape barrier (work function) in a multi-alkali photocathode are presented. The core levels indicate that the alkali atoms are in an oxidized state and therefore the compound Na sub 2 KSb can be regarded as an ionic semiconductor. The measured escape barrier of the Cs sub 2 O surface layer is determined as 2.3 eV.

  4. Studies of magnetism and exchange scattering in solids using synchroton radiation and spin-polarized photoemission. Progress report, June 1, 1982-May 31, 1983

    International Nuclear Information System (INIS)

    Rothberg, G.M.

    1983-01-01

    Some of the experiments necessary for proving the existence of Spin Polarized EXAFS (SPEXAFS) and for establishing it as a useful techncique for studying magnetism in solids have been carried out at the Stanford Synchrotron Radiation Laboratory (SSRL) and the National Synchrotron Light Source (NSLS). Transmission EXAFS, which does not depend on electron spin, has been measured in several manganese compounds. The 3s photopeaks of Mn 2 + in MnF 2 have been shown to display EXAFS-like oscillations. The pin dependence of these oscillations will next be studied. Observations of the 3p photopeaks of iron metal on a palladium substrate have shown anomalous intensity variations with varying photon energy. This phenomenon will also be studied further. The existence of Cooper minima in the iron 3s and 3p photoabsorption cross sections has been sought, and this investigation will continue

  5. X-ray photoemission analysis of chemically modified TlBr surfaces for improved radiation detectors

    International Nuclear Information System (INIS)

    Nelson, A. J.; Voss, L. F.; Beck, P. R.; Graff, R. T.; Conway, A. M.; Nikolic, R. J.; Payne, S. A.; Lee, J.-S.; Kim, H.; Cirignano, L.; Shah, K.

    2013-01-01

    We subjected device-grade TlBr to various chemical treatments used in room temperature radiation detector fabrication to determine the resulting surface composition and electronic structure. As-polished TlBr was treated separately with HCl, SOCl 2 , Br:MeOH and HF solutions. High-resolution photoemission measurements on the valence band electronic structure and Tl 4f, Br 3d, Cl 2p and S 2p core lines were used to evaluate surface chemistry and shallow heterojunction formation. Surface chemistry and valence band electronic structure were correlated with the goal of optimizing the long-term stability and radiation response

  6. Layer- and lateral-resolved magnetization studies using photoemission electron microscopy

    International Nuclear Information System (INIS)

    Wei, D.H.; Hsu, Y.J.; Lin, C.-C.; Lai, C.-H.; Ou, J.Y.; Wu, J.C.

    2004-01-01

    The magnetic circular dichroism in X-ray absorption is employed to study the element-specific magnetization in a TbFe/Co bilayer system and patterned Ni 80 Fe 20 film. Taking advantage of the energy tunability as well as the penetration power of synchrotron radiation, the magnetization directions of Co and Fe deposited in different layers were examined as a function of Co film thickness. For patterned films, the photoemission electron microscope reveals a clear correlation between the magnetic configurations and geometries of the patterns

  7. Synchrotron photoemission study of (Zn,Co)O films with uniform Co distribution

    DEFF Research Database (Denmark)

    Guziewicz, E.; Lukasiewicz, M. I.; Wachnicki, L.

    2011-01-01

    of foreign phases and metal accumulations as indicated by TEM data. The electronic structure of (Zn,Co)O films was studied by Resonant Photoemission Spectroscopy across the Co3p–Co3d photoionization threshold. We have observed that the resonant enhancement of the photoemission intensity from the Co3d shell...

  8. UV photoemission studies of metal photocathodes for particle accelerators

    International Nuclear Information System (INIS)

    Fischer, J.; Srinivasan-Rao, T.

    1988-01-01

    Photoemission from several metals was studied with 10 ps laser pulses at 266 nm. The yield was linear with energy and with area. Quantum efficiencies (/eta/) were determined (up to 10/sup /minus/3/ e/photons for samarium), and found to vary as (hν-/phi/) 2 . /eta/ also increased with the field. The field assisted efficiencies were calculated for some metals and confirmed by experiment for gold, up to surface fields of /approximately/3/times/10 8 V/m. High charge and current densities, close to 10 5 A/cm 2 from macroscopic areas, were measured or indicated. Results are then related to applications in accelerators. 18 refs., 15 figs., 4 tabs

  9. Atomic nature of the Schottky barrier height formation of the Ag/GaAs(001)-2 × 4 interface: An in-situ synchrotron radiation photoemission study

    International Nuclear Information System (INIS)

    Cheng, Chiu-Ping; Chen, Wan-Sin; Lin, Keng-Yung; Wei, Guo-Jhen; Cheng, Yi-Ting; Lin, Yen-Hsun; Wan, Hsien-Wen; Pi, Tun-Wen; Tung, Raymond T.; Kwo, Jueinai; Hong, Minghwei

    2017-01-01

    Highlights: • The interaction of Ag on a p-type α2 GaAs(001)-2 × 4 surface has been studied. • The dipole formation mechanism of the Ag/GaAs(001)-2 × 4 interface is proposed. • Determination of the SBH prior to metal formation is found. • Inadequacy of the metal-induced gap-state model for explaining the SBH is evident. - Abstract: The Interface of Ag with p-type α2 GaAs(001)-2 × 4 has been studied to further understand the formation mechanism of the Schottky barrier height (SBH). In the initial phase of Ag deposition, high-resolution core-level data show that Ag adatoms effectively passivate the surface As-As dimers without breaking them apart. The Ag(+)-As(−) dipoles are thus generated with a maximal potential energy of 0.26 eV; a SBH of 0.38 eV was measured. Greater Ag coverage causes elemental segregation of As/Ga atoms, reversing the direction of the net dipole. The band bending effect near the interface shows a downward shift of 0.08 eV, and the final SBH is similar to the value as measured at the initial Ag deposition. Both parameters are secured at 0.25 Å of Ag thickness prior to the observation of metallic behavior of Ag. Inadequacy of the metal-induced gap-state model for explaining SBH is evident.

  10. Atomic nature of the Schottky barrier height formation of the Ag/GaAs(001)-2 × 4 interface: An in-situ synchrotron radiation photoemission study

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, Chiu-Ping, E-mail: cpcheng@mail.ncyu.edu.tw [Department of Electrophysics, National Chiayi University, Chiayi, 60004, Taiwan, ROC (China); Chen, Wan-Sin [Department of Electrophysics, National Chiayi University, Chiayi, 60004, Taiwan, ROC (China); National Synchrotron Radiation Research Center, Hsinchu, 30076, Taiwan, ROC (China); Lin, Keng-Yung [Graduate Institute of Applied Physics and Department of Physics, National Taiwan University, Taipei, 10617, Taiwan, ROC (China); Wei, Guo-Jhen; Cheng, Yi-Ting [Department of Electrophysics, National Chiayi University, Chiayi, 60004, Taiwan, ROC (China); Lin, Yen-Hsun; Wan, Hsien-Wen [Graduate Institute of Applied Physics and Department of Physics, National Taiwan University, Taipei, 10617, Taiwan, ROC (China); Pi, Tun-Wen, E-mail: pi@nsrrc.org.tw [National Synchrotron Radiation Research Center, Hsinchu, 30076, Taiwan, ROC (China); Tung, Raymond T. [Department of Physics, Brooklyn College, CUNY, NY 11210 (United States); Kwo, Jueinai, E-mail: raynien@phys.nthu.edu.tw [Department of Physics, National Tsing Hua University, Hsinchu, 30013, Taiwan, ROC (China); Hong, Minghwei, E-mail: mhong@phys.ntu.edu.tw [Graduate Institute of Applied Physics and Department of Physics, National Taiwan University, Taipei, 10617, Taiwan, ROC (China)

    2017-01-30

    Highlights: • The interaction of Ag on a p-type α2 GaAs(001)-2 × 4 surface has been studied. • The dipole formation mechanism of the Ag/GaAs(001)-2 × 4 interface is proposed. • Determination of the SBH prior to metal formation is found. • Inadequacy of the metal-induced gap-state model for explaining the SBH is evident. - Abstract: The Interface of Ag with p-type α2 GaAs(001)-2 × 4 has been studied to further understand the formation mechanism of the Schottky barrier height (SBH). In the initial phase of Ag deposition, high-resolution core-level data show that Ag adatoms effectively passivate the surface As-As dimers without breaking them apart. The Ag(+)-As(−) dipoles are thus generated with a maximal potential energy of 0.26 eV; a SBH of 0.38 eV was measured. Greater Ag coverage causes elemental segregation of As/Ga atoms, reversing the direction of the net dipole. The band bending effect near the interface shows a downward shift of 0.08 eV, and the final SBH is similar to the value as measured at the initial Ag deposition. Both parameters are secured at 0.25 Å of Ag thickness prior to the observation of metallic behavior of Ag. Inadequacy of the metal-induced gap-state model for explaining SBH is evident.

  11. High-energy photoemission studies of oxide interfaces

    Science.gov (United States)

    Claessen, Ralph

    2015-03-01

    The interfaces of complex oxide heterostructures can host novel quantum phases not existing in the bulk of the constituents, with the high-mobility 2D electron system (2DES) in LaAlO3/SrTiO3 (LAO/STO) representing a prominent example. Despite extensive research the origin of the 2DES and its unusual properties - including the supposed coexistence of superconductivity and ferromagnetism - are still a matter of intense debate. Photoelectron spectroscopy, recently extended into the soft (SX-ARPES) and hard (HAXPES) X-ray regime, is a powerful method to provide detailed insight into the electronic structure of these heterostructures and, in particular, of the buried interface. This includes the identification of the orbital character of the 2DES as well as the determination of vital band structure information, such as band alignment, band bending, and even k-resolved band dispersions and Fermi surface topology. Moreover, resonant photoemission at the Ti L-edge reveals the existence of two different species of Ti 3d states, localized and itinerant, which can be distinguished and identified by their different resonance behavior. The role of oxygen vacancies is studied by controlled in-situ oxidation, which allows us to vary the composition from fully stoichiometric to strongly O-deficient. By comparison to free STO surfaces we can thus demonstrate that the metallicity of the heteointerfaces is intrinsic, i . e . it persists even in the absence of O defects. I will discuss our photoemission results on LAO/STO heterostructures in both (100) and (111) orientation as well as on the related system γ-Al2O3/STO(100), which also hosts a 2DES with an even higher mobility. Work in collaboration with J. Mannhart (MPI-FKF, Stuttgart), N. Pryds (TU Denmark), G. Rijnders (U Twente), S. Suga (U Osaka), M. Giorgoi (BESSY, HZB), W. Drube (DESY Photon Science), V.N. Strocov (Swiss Light Source), J. Denlinger (Advanced Light Source, LBNL), and T.-L. Lee (Diamond Light Source). Support by

  12. Photoemission study of Ca-intercalated graphite superconductor CaC6

    International Nuclear Information System (INIS)

    Okazaki, Hiroyuki; Yoshida, Rikiya; Iwai, Keisuke; Noami, Kengo; Muro, Takayuki; Nakamura, Tetsuya; Wakita, Takanori; Muraoka, Yuji; Hirai, Masaaki; Tomioka, Fumiaki; Takano, Yoshihiko; Takenaka, Asami; Toyoda, Masahiro; Oguchi, Tamio; Yokoya, Takayoshi

    2010-01-01

    In this work, we have performed resonant photoemission studies of Ca-intercalated graphite superconductor CaC 6 . Using photon energy of the Ca 2p-3d threshold, the photoemission intensity of the peak at Fermi energy (E F ) is resonantly enhanced. This result provides spectroscopic evidence for the existence of Ca 3d states at E F , and strongly supports that Ca 3d state plays a crucial role for the superconductivity of this material with relatively high T c .

  13. Resonant photoemission study of CeRu4Sb12

    International Nuclear Information System (INIS)

    Ishii, Hiroyoshi; Miyahara, Tsuneaki; Takayama, Yasuhiro; Shiozawa, Hidetsugu; Obu, Kenji; Matsuda, Tatsuma D.; Aoki, Yuji; Sugawara, Hitoshi; Sato, Hideyuki

    2005-01-01

    We have measured the Ce 4d-4f and Ce 3d-4f resonant photoemission spectra of CeRu 4 Sb 12 . The Ce 4f spectra show the spectral features corresponding to a weakly hybridized system. The number of 4f electrons is estimated to be ∼1.0

  14. Photoemission study on the formation of Mo contacts to CuInSe2

    International Nuclear Information System (INIS)

    Nelson, A.J.; Niles, D.W.; Kazmerski, L.L.; Rioux, D.; Patel, R.; Hoechst, H.

    1992-01-01

    Synchrotron radiation soft-x-ray photoemission spectroscopy was used to investigate the development of the electronic structure at the Mo/CuInSe 2 interface. Mo overlayers were e-beam deposited in steps on single-crystal n-type CuInSe 2 at ambient temperature. Photoemission measurements were acquired after each growth in order to observe changes in the valence-band electronic structure as well as changes in the In 4d, Se 3d, and Mo 4d core lines. Photoemission measurements on the valence-band and core lines were also obtained after annealing. The results were used to correlate the interface chemistry with the electronic structure at this interface and to directly determine the maximum possible Schottky barrier height φ b to be ≤0.2 eV at the Mo/CuInSe 2 junction before annealing, thus showing that this contact is essentially ohmic

  15. Rb-intercalated C60 compounds studied by photoemission spectroscopies

    International Nuclear Information System (INIS)

    Brambilla, A.; Giovanelli, L.; Vilmercati, P.; Cattoni, A.; Biagioni, P.; Goldoni, A.; Finazzi, M.; Duo, L.

    2005-01-01

    We report on a combined photoemission and inverse photoemission spectroscopy analysis on Rb x C 60 compounds with different stoichiometries (0-bar x-bar 6). Apart from shifts and broadening of the spectral features associated to the different phase formed, we observe in the RbC 60 phase the presence of the highest occupied molecular orbital (HOMO) shoulder and of its symmetric (with respect to the Fermi level) empty state. According to calculations, the metallicity of this phase and the presence of these electronic states may be taken as a fingerprint of the interplay between electron-electron and electron-phonon interactions in determining the electronic behavior of alkali metal fullerides

  16. Angle-resolved photoemission spectroscopy (ARPES) studies of cuprate superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Palczewski, Ari Deibert [Iowa State Univ., Ames, IA (United States)

    2010-01-01

    This dissertation is comprised of three different angle-resolved photoemission spectroscopy (ARPES) studies on cuprate superconductors. The first study compares the band structure from two different single layer cuprates Tl2Ba2CuO6+δ (Tl2201) Tc, max ≈ 95 K and (Bi 1.35Pb0.85)(Sr1.47La0.38)CuO6+δ (Bi2201) Tc, max ≈ 35 K. The aim of the study was to provide some insight into the reasons why single layer cuprate's maximum transition temperatures are so different. The study found two major differences in the band structure. First, the Fermi surface segments close to (π,0) are more parallel in Tl2201 than in Bi2201. Second, the shadow band usually related to crystal structure is only present in Bi2201, but absent in higher Tc Tl2201. The second study looks at the different ways of doping Bi2Sr2CaCu2O8+δ (Bi2212) in-situ by only changing the post bake-out vacuum conditions and temperature. The aim of the study is to systematically look into the generally overlooked experimental conditions that change the doping of a cleaved sample in ultra high vacuum (UHV) experiments. The study found two major experimental facts. First, in inadequate UHV conditions the carrier concentration of Bi2212 increases with time, due to the absorption of oxygen from CO2/CO molecules, prime contaminants present in UHV systems. Second, in a very clean UHV system at elevated temperatures (above about 200 K), the carrier concentration decreases due to the loss of oxygen atoms from the Bi-O layer. The final study probed the particle-hole symmetry of the pseudogap phase in high temperature superconducting cuprates by looking at the thermally excited bands above the Fermi level. The data showed a particle-hole symmetric pseudogap which symmetrically closes away from the nested FS before the node. The data is

  17. Angle-resolved photoemission spectroscopy (ARPES) studies of cuprate superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Palczewski, Ari Deibert [Iowa State Univ., Ames, IA (United States)

    2010-01-01

    This dissertation is comprised of three different angle-resolved photoemission spectroscopy (ARPES) studies on cuprate superconductors. The first study compares the band structure from two different single layer cuprates Tl2Ba2CuO6+δ (Tl2201) Tc,max ~95 K and (Bi1.35Pb0.85)(Sr1.47La0.38)CuO6+δ (Bi2201) Tc,max 35 K. The aim of the study was to provide some insight into the reasons why single layer cuprate's maximum transition temperatures are so different. The study found two major di erences in the band structure. First, the Fermi surface segments close to ( π,0) are more parallel in Tl2201 than in Bi2201. Second, the shadow band usually related to crystal structure is only present in Bi2201, but absent in higher Tc Tl2201. The second study looks at the different ways of doping Bi2Sr2CaCu2O8+δ (Bi2212) in-situ by only changing the post bake-out vacuum conditions and temperature. The aim of the study is to systematically look into the generally overlooked experimental conditions that change the doping of a cleaved sample in ultra high vacuum (UHV) experiments. The study found two major experimental facts. First, in inadequate UHV conditions the carrier concentration of Bi2212 increases with time, due to the absorption of oxygen from CO2/CO molecules, prime contaminants present in UHV systems. Second, in a very clean UHV system at elevated temperatures (above about 200 K), the carrier concentration decreases due to the loss of oxygen atoms from the Bi-O layer. The final study probed the particle-hole symmetry of the pseudogap phase in high temperature superconducting cuprates by looking at the thermally excited bands above the Fermi level. The data showed a particle-hole symmetric pseudogap which symmetrically closes away from the nested FS before the node. The data is consistent with

  18. a Study on SODIUM(110) and Other Nearly Free Electron Metals Using Angle Resolved Photoemission Spectroscopy.

    Science.gov (United States)

    Lyo, In-Whan

    Electronic properties of the epitaxially grown Na(110) film have been studied using angle resolved ultraviolet photoemission spectroscopy with synchrotron radiation as the light source. Na provides an ideal ground to study the fundamental aspects of the electron-electron interactions in metals, because of its simple Fermi surface and small pseudopotential. The absolute band structure of Na(110) using angle resolved photoemission spectroscopy has been mapped out using the extrema searching method. The advantage of this approach is that the usual assumption of the unoccupied state dispersion is not required. We have found that the dispersion of Na(1l0) is very close to the parabolic band with the effective mass 1.21 M_{rm e} at 90 K. Self-consistent calculations of the self-energy for the homogeneous electron gas have been performed using the Green's function technique within the framework of the GW approximation, in the hope of understanding the narrowing mechanism of the bandwidth observed for all the nearly-free-electron (NFE) metals. Good agreements between the experimental data and our calculated self-energy were obtained not only for our data on k-dependency from Na(l10), but also for the total bandwidth corrections for other NFE metals, only if dielectric functions beyond the random phase approximation were used. Our findings emphasize the importance of the screening by long wavelength plasmons. Off-normal spectra of angle resolved photoemission from Na(110) show strong asymmetry of the bulk peak intensity for the wide range of photon energies. Using a simple analysis, we show this asymmetry has an origin in the interference of the surface Umklapp electrons with the normal electrons. We have also performed the detailed experimental studies of the anomalous Fermi level structure observed in the forbidden gap region of Na. This was claimed by A. W. Overhauser as the evidence of the charge density wave in the alkali metal. The possibility of this hypothesis is

  19. X-ray photoemission study of plutonium metal

    International Nuclear Information System (INIS)

    Baptist, R.

    1982-01-01

    The x-ray induced photoemission from clean pure plutonium metal is described and the results for both core and valence levels are compared with previous measurements on light actinides. It is found that, as in thorium and urnaium, the configuration interaction plays an important role for core levels, in particular for those of the n=5 shell. The experimental valence-band spectrum confirms the existence of 5f states at the Fermi level and is compared with a density of states of FCC Pu derived from a recent relativistic band structure calculation. (author)

  20. Study of Si-N amorphous compounds combining XPS (X photoemission) and EELS (electron energy loss spectra) optical measurements. Internal levels photoemission. Pt. 2

    International Nuclear Information System (INIS)

    Guraya, M.M.; Acolani, H.; Zampieri, G.E.; Silva, J.H. Dias da; Cisneros, J.I.; Cantao, M.; Marques, F.C.

    1990-01-01

    A Si-N non-stoichiometric hydrogenated amorphous compounds study with different N- contents is presented. The shape and shifts of the photoemission peaks corresponding to the N - 1s and Si - 2p internal levels are analyzed. Based on the latter, the homogeneity of the samples and the Si - N bonds charge transfer is discussed. (Author) [es

  1. Ga droplet morphology on GaAs(001) studied by Lloyd's mirror photoemission electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Tang, W X; Jesson, D E; Pavlov, K M; Morgan, M J [School of Physics, Monash University, Victoria 3800 (Australia); Usher, B F [Department of Electronic Engineering, La Trobe University, Victoria 3086 (Australia)

    2009-08-05

    We apply Lloyd's mirror photoemission electron microscopy (PEEM) to study the surface shape of Ga droplets on GaAs(001). An unusual rectangular-based droplet shape is identified and the contact angle is determined in situ. It is shown that quenching does not appreciably affect droplet shape and ex situ measurements of the contact angle by atomic force microscopy are in good agreement with Lloyd's mirror PEEM. Extension of Lloyd's mirror technique to reconstruct general three-dimensional (3D) surface shapes and the potential use of synchrotron radiation to improve vertical resolution is discussed.

  2. Nanoscale spatial analysis of clay minerals containing cesium by synchrotron radiation photoemission electron microscopy

    Science.gov (United States)

    Yoshigoe, Akitaka; Shiwaku, Hideaki; Kobayashi, Toru; Shimoyama, Iwao; Matsumura, Daiju; Tsuji, Takuya; Nishihata, Yasuo; Kogure, Toshihiro; Ohkochi, Takuo; Yasui, Akira; Yaita, Tsuyoshi

    2018-01-01

    A synchrotron radiation photoemission electron microscope (SR-PEEM) was applied to demonstrate the pinpoint analysis of micrometer-sized weathered biotite clay particles with artificially adsorbed cesium (Cs) atoms. Despite the insulating properties of the clay, we observed the spatial distributions of constituent elements (Si, Al, Cs, Mg, and Fe) without charging issues and clarified reciprocal site-correlations among these elements with nanometer resolution. We found that Cs atoms were likely to be adsorbed evenly over the entire particle; however, we identified an occupational conflict between Cs and Mg atoms, implying that Cs sorption involves ion exchange processes. Spatially resolved X-ray absorption spectra (XAS) of the Cs4,5 M-edge region showed Cs to be present in a monocation state (Cs+) as typically observed for Cs compounds. Further pinpoint XAS measurements were also performed at the Fe L2,3-edge to determine the chemical valence of the Fe atoms. The shapes of the spectra were similar to those for Fe2O3, indicating that Fe in the clay was in a 3+ oxidation state. From these observations, we infer that charge compensation facilitates Cs adsorption in the vicinity of a substitution site where Si4+ ions are replaced by Fe3+ ions in SiO4 tetrahedral sheets. Our results demonstrate the utility of SR-PEEM as a tool for spatially resolved chemical analyses of various environmental substances, which is not limited by the poor conductivity of samples.

  3. Photoemission study of Kr 3d→np autoionization resonances

    International Nuclear Information System (INIS)

    Lindle, D.W.; Heimann, P.A.; Ferrett, T.A.; Piancastelli, M.N.; Shirley, D.A.

    1987-01-01

    Resonant photoelectron spectra of Kr have been taken in the photon-energy ranges of the 3d/sub 5/2/→5p,6p and 3d/sub 3/2/→5p excitations. The spectra, which closely resemble normal Kr + 3d/sup -1/ Auger spectra, illustrate the importance of ''spectator'' Auger-like decay for inner-shell resonances, in which the initially excited electron does not participate in the core-hole deexcitation process, except to respond to the change in the atomic potential. Possible assignments for some of the spectator decay channels are discussed based on photoemission intensity measurements at the different 3d resonances. These assignments suggest that shake-up (e.g., 5p→6p) of the ''spectator'' electron during the decay process is not quite as important as previously suspected. The resonance profiles of some of the more intense satellites have been determined over the 3d→np resonances. Very small resonance effects also were observed in the partial cross section for 4p subshell ionization, which produced asymmetric Fano-type profiles. The 4p angular distribution, in contrast, exhibits a pronounced effect in the resonance energy range. The 4p results demonstrate that nonspectator autoionization also is present

  4. Photoemission studies using femtosecond pulses for high brightness electron beams

    International Nuclear Information System (INIS)

    Srinivasan-Rao, T.; Tsang, T.; Fischer, J.

    1990-06-01

    We present the results of a series of experiments where various metal photocathodes are irradiated with ultrashort laser pulses, whose characteristics are: λ = 625 nm, τ = 100 fs, PRR = 89.5 MHz, Hν = 2 eV and average power 25 mW in each of the two beams. The quantum efficiency of the metals range from ∼10 -12 to 10 -8 at a power density of 100 MW/cm 2 at normal incidence. Since all the electrons are emitted due to multiphoton processes, these efficiencies are expected to increase substantially at large intensities. The efficiency at 100 MW/cm 2 has been increased by using p-polarized light at oblique incidence by ∼20x and by mediating the electron emission through surface plasmon excitation by ∼10 3 x. For the low intensities used in these experiments, the electron pulse duration is almost the same as the laser pulse duration for both the bulk and the surface plasmon mediated photoemission. 7 refs., 8 figs., 2 tabs

  5. X-ray photoemission electron microscopy for the study of semiconductor materials

    International Nuclear Information System (INIS)

    Anders, Simone; Stammler, Thomas; Padmore, Howard A.; Terminello, Louis J.; Jankowski, Alan F.; Stoehr, Joachim; Diaz, Javier; Cossy-Favre, Aline; Singh, Sangeet

    1998-01-01

    Photoemission Electron Microscopy using X-rays (X-PEEM) is a novel combination of two established materials analysis techniques--PEEM using UV light, and Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy. This combination allows the study of elemental composition and bonding structure of the sample by NEXAFS spectroscopy with a high spatial resolution given by the microscope. A simple, two lens, 10 kV operation voltage PEEM has been used at the Stanford Synchrotron Radiation Laboratory and at the Advanced Light Source (ALS) in Berkeley to study various problems including materials of interest for the semiconductor industry. In the present paper we give a short overview over the method and the instrument which was used, and describe in detail a number of applications. These applications include the study of the different phases of titanium disilicide, various phases of boron nitride, and the analysis of small particles. A brief outlook is given on possible new fields of application of the PEEM technique, and the development of new PEEM instruments

  6. VUV photoemission studies of candidate Large Hadron Collider vacuum chamber materials

    CERN Document Server

    Cimino, R; Baglin, V

    1999-01-01

    In the context of future accelerators and, in particular, the beam vacuum of the Large Hadron Collider (LHC), a 27 km circumference proton collider to be built at CERN, VUV synchrotron radiation (SR) has been used to study both qualitatively and quantitatively candidate vacuum chamber materials. Emphasis is given to show that angle and energy resolved photoemission is an extremely powerful tool to address important issues relevant to the LHC, such as the emission of electrons that contributes to the creation of an electron cloud which may cause serious beam instabilities and unmanageable heat loads on the cryogenic system. Here we present not only the measured photoelectron yields from the proposed materials, prepared on an industrial scale, but also the energy and in some cases the angular dependence of the emitted electrons when excited with either a white light (WL) spectrum, simulating that in the arcs of the LHC, or monochromatic light in the photon energy range of interest. The effects on the materials ...

  7. VUV photoemission studies of candidate LHC vacuum chamber materials

    CERN Document Server

    Baglin, V; Collins, I R

    1998-01-01

    In the context of future accelerators and, in particular, the beam vacuum of the LargeHadron Collider (LHC), a 27 km circumference proton collider to be built at CERN, VUVsynchrotron radiation (SR) has been used to study both qualitatively and quantitatively candidatevacuum chamber materials. Emphasis is given to show that angle and energy resolvedphotoemission is an extremely powerful tool to address important issues relevant to the LHC, suchas the emission of electrons that contribute to the creation of an electron cloud which may causeserious beam instabilities. Here we present not only the measured photoelectron yields (PY)from the proposed materials, prepared on an industrial scale, but also the energy and, in some cases,the angular dependence of the emitted electrons when excited with either a white light (WL)spectrum, simulating that in the arcs of the LHC or monochromatic light in the photon energy rangeof interest. The effects on the materials examined of WL irradiation and/or ion sputtering,simulati...

  8. Photoemission study of electronic structure of the half-metallic ferromagnet Co₃Sn₂S₂

    OpenAIRE

    Holder, M.; Dedkov, Y.; Kade, A.; Rosner, H.; Schnelle, W.; Leithe-Jasper, A.; Weihrich, R.; Molodtsov, S.

    2009-01-01

    Surface electronic structure of polycrystalline and single-crystalline samples of the half-metallic ferromagnet Co₃Sn₂S₂ was studied by means of angle-resolved and core-level photoemissions. The experiments were performed in temperature regimes both above and below a Curie temperature of 176.9 K. The spectroscopic results are compared to local-spin density approximation band-structure calculations for the bulk samples. It is found that the surface sensitive experimental data are generally rep...

  9. Electronic Structures of Purple Bronze KMo6O17 Studied by X-Ray Photoemission Spectra

    Science.gov (United States)

    Qin, Xiaokui; Wei, Junyin; Shi, Jing; Tian, Mingliang; Chen, Hong; Tian, Decheng

    X-ray photoemission spectroscopy study has been performed for the purple bronze KMo6O17. The structures of conduction band and valence band are analogous to the results of ultraviolet photoemission spectra and are also consistent with the model of Travaglini et al., but the gap between conduction and valence band is insignificant. The shape of asymmetric and broadening line of O-1s is due to unresolved contributions from the many inequivalent oxygen sites in this crystal structure. Mo 3d core-level spectrum reveals that there are two kinds of valence states of Molybdenum (Mo+5 and Mo+6). The calculated average valence state is about +5.6, which is consistent with the expectation value from the composition of this material. The tail of Mo-3d spectrum toward higher binding energy is the consequence of the excitation of electron-hole pairs with singularity index of 0.21.

  10. A photoemission study of Mn grown on GaAs(100)

    International Nuclear Information System (INIS)

    James, D.; Riley, J.; Leckey, R.; Usher, B.; Sieber, N.; Seyller, Th.; Ley, L.

    2002-01-01

    Full text: Metal contacts on semiconductors have been an important area for device manufacture. The possibility of lattice matched growth of magnetic metals on semiconductors was once thought to be a unobtainable goal. More recently it has been found that transition metals can react with the semiconductor substrates, forming another lattice with a more comparable lattice constant, from which epitaxial growth can then proceed. Al grows epitaxially on GaN even with a lattice mismatch greater than 10%. In this instance, Al displaces Ga being driven by a larger heat of formation to produce an AlN buffer layer, on which Al can then grow. This paper investigates the room temperature deposition of Mn onto GaAs(100) at room temperature. The Photoemission study was carried out at the UEL56/2 PGM2 beam line at BESSY II in Berlin, Germany. Synchrotron radiation was used to observe the surface as thin layers of Mn were deposited. The interaction of manganese with the substrate tends to donate electron density to neighbouring atoms, decreasing binding energy. No further segregation of substitutional or interstitial Mn and Ga can be seen from angle dependence data at this temperature, with metallic manganese eventually attenuating the bulk Ga signal to the point where it is indistinguishable from the background. It is concluded that there the metal reacts with the semiconductor surface with some indiffusion as confirmed using SIMS. Previously, the reaction was only thought to have taken place above room temperature. The resulting structure consists of a Ga-As-Mn buffer layer as with the higher temperature depositions

  11. Adsorption of 3,4-ethylenedioxythiophene (EDOT) on noble metal surfaces: A photoemission and X-ray absorption study

    International Nuclear Information System (INIS)

    Pasquali, L.; Terzi, F.; Montecchi, M.; Doyle, B.P.; Lukkari, J.; Zanfrognini, B.; Seeber, R.; Nannarone, S.

    2009-01-01

    The adsorption of 3,4-ethylenedioxythiophene (EDOT) on Au and Pt surfaces is studied by core level and valence band photoemission using synchrotron radiation and by near edge X-ray absorption spectroscopy. To closer simulate real applications, the films are grown from aqueous solution at room temperature and are compared to an 'ideal' film prepared by dosing the molecules from the vapour phase on a clean Au(1 1 1) single crystal. The S 2p, C 1s and O 1s levels show multiple components which are associated to molecular fragmentation. NEXAFS confirms that fragmentation takes place at the surface. Thiophene species as well as alkyl chains and S n species are identified as the most probable fragmentation products.

  12. Deflection gating for time-resolved x-ray magnetic circular dichroism-photoemission electron microscopy using synchrotron radiation

    Science.gov (United States)

    Wiemann, C.; Kaiser, A. M.; Cramm, S.; Schneider, C. M.

    2012-06-01

    In this paper, we present a newly developed gating technique for a time-resolving photoemission microscope. The technique makes use of an electrostatic deflector within the microscope's electron optical system for fast switching between two electron-optical paths, one of which is used for imaging, while the other is blocked by an aperture stop. The system can be operated with a switching time of 20 ns and shows superior dark current rejection. We report on the application of this new gating technique to exploit the time structure in the injection bunch pattern of the synchrotron radiation source BESSY II at Helmholtz-Zentrum Berlin for time-resolved measurements in the picosecond regime.

  13. Experimental studies on the photoemission of gallium arsenide crystals

    International Nuclear Information System (INIS)

    Westermann, M.

    2003-04-01

    In this thesis the study influence of residual gases on the lifetime, the temperature dependence of the quantum yield, and the influence of activation with potassium on both effects for GaAs-photocathodes is described. (HSI)

  14. Recent Progress in Synchrotron Radiation Photoemission Spectroscopy of Solids : Applications of VUV, Soft and Hard X-Ray Radiation

    International Nuclear Information System (INIS)

    Taniguchi, M.

    2004-01-01

    The Hiroshima Synchrotron Radiation Center is a common facility for both research and education in the field of synchrotron radiation science. The operation of the light source was started from March 1998. The storage ring can be operated at 700 MeV with a critical energy of 873 eV. The machine has a racetrack shape with a circumference of 22 m, and has 14 photon beam ports. The maximum operational current is 300 mA, and the beam lifetime is longer than 6 h at 200 mA. Of total 13 beamlines introduced so far, three beamlines are dedicated to photoemission spectroscopy (PES). An available photon-energy range is hν=26-300 eV. A hemispherical photoelectron analyzer is equipped at the end station. Total energy resolution has been achieved to ∼ 15 meV at hν=100 eV. The photon-energy range is hν=4-40 eV and total energy resolution is ∼ 4.5 meV at hν=7 eV. Although total energy resolution has been achieved to ∼25 meV at hν=80 eV, we usually carry out the PES experiments. The PES spectra taken at hν∼7 eV provide information on the conduction band electrons. In order to investigate the bulk-originated electronic structure we started the hard x-ray PES experiments with a total energy resolution of ∼ 270 meV. Thus, we promote the research project with use of light in a wide energy-range (7 eV-6 keV). 1) Unusual energy gap formation in the Kondo semiconductor CeRhAs has attracted much interest for its unusual energy gap formation or metal-to-insulator transition as temperature decreases. The energy gap is assumed to be formed by the temperature dependence of the c-f hybridization. By means of resonant PES, we could observe a energy-gap structure in the Ce 4f states. In order to observe As 4p state and Rh 4d state, we have measured the PES spectra at hν=7.9 eV, 40 eV and 6 keV, respectively, due to the photon-energy dependence of photoionization cross-section. From the spectra at hν=7.9 eV, we could see that the density of states (DOS) near E F decreases with

  15. Photoemission-monitored x-ray standing wave studies of molecular adsorbate surface structure

    International Nuclear Information System (INIS)

    Lee, John Jethro

    2002-01-01

    The influence of non-dipole photoemission terms on the accuracy of photoemission-monitored NIXSW structure determinations has been studied. An experimental survey has been made of values of the incoherent dipole-quadrupole parameter as a function of energy and atomic number for the Is states of elements between carbon and chlorine inclusive. These values are compared with recent theoretical calculations. The contribution of the coherent dipole-quadrupole interference terms, whose form has been theoretically derived recently, has been experimentally measured for Is photoemission from clean Al(111). The coherent dipole-quadrupole effect is found to be small and easily corrected for, while the previously-known incoherent effect is shown to result in tolerable errors in most cases. Adsorption of methyl thiol (CH 3 SH) on Pt(111), followed by annealing to ∼ 220 K is believed to result in the formation of methyl thiolate (-SCH 3 ). Two structural models are consistent with NIXSW data presented here: co-occupation of fcc and hcp sites, and a tilted atop-bonded geometry. On annealing to ∼500 K, complete dissociation occurs, and the remaining S atoms are found to lie in fcc sites, with evidence of partial occupation of a more complex phase. The adsorption of CO, NO and O on Ni(111), and the O+CO and O+NO coadsorbate systems have been investigated with NIXSW. The sites found for O, CO and NO are consistent with previous quantitative structure determinations. In the presence of a precoverage of oxygen, the conclusion of a recent photoelectron diffraction study that the preferred CO site is atop a substrate Ni atom is confirmed. In contrast, NO adsorption onto a (2 x 2)-O precovered surface is found to result in the restructuring of the oxygen layer, with NO adsorbing in the hollow sites, as in the pure-NO layer. Discrepancies in bond lengths between these NIXSW results and previous quantitative determinations are discussed. (author)

  16. Optical study of HgCdTe infrared photodetectors using internal photoemission spectroscopy

    International Nuclear Information System (INIS)

    Lao, Yan-Feng; Unil Perera, A. G.; Wijewarnasuriya, Priyalal S.

    2014-01-01

    We report a study of internal photoemission spectroscopy (IPE) applied to a n-type Hg 1−x Cd x Te/Hg 1−y Cd y Te heterojunction. An exponential line-shape of the absorption tail in HgCdTe is identified by IPE fittings of the near-threshold quantum yield spectra. The reduction of quantum yield (at higher photon energy) below the fitting value is explained as a result of carrier-phonon scatterings. In addition, the obtained bias independence of the IPE threshold indicates a negligible electron barrier at the heterojunction interface

  17. Studies on a laser driven photoemissive high-brightness electron source and novel photocathodes

    International Nuclear Information System (INIS)

    Geng Rongli; Song Jinhu; Yu Jin

    1997-01-01

    A laser driven photoemissive high-brightness electron source at Beijing University is reported. Through a DC accelerating gap of 100 kV voltage, the device is capable of delivering high-brightness electron beam of 35-100 ps pulse duration when irradiated with a mode-locked YAG laser. The geometry of the gun is optimized with the aid of simulation codes EGUN and POISSON. The results of experimental studies on ion implanted photocathode and cesium telluride photocathode are given. The proposed laser driven superconducting RF gun is also discussed

  18. Study of III-V semiconductor band structure by synchrotron photoemission

    International Nuclear Information System (INIS)

    Williams, G.P.; Cerrina, F.; Anderson, J.; Lapeyre, G.J.; Smith, R.J.; Hermanson, J.; Knapp, J.A.

    1982-01-01

    Angle-resolved synchrotron photoemission studies of six III-V semiconductors have been carried out. For emission normal to the (110) plane of these materials, peaks in the experimental spectra were identified with the bands involved in the transitions, and the critical point energies X 3 , X 5 , and Σ 1 /sup min/, were determined. The data indicate that k perpendicular is conserved in the transitions. Comparison of the data with theoretical bands permits an evaluation of k perpendicular associated with the experimentally observed transition, and from this information the bands were plotted out

  19. Photoemission studies of fluorine functionalized porous graphitic carbon

    Science.gov (United States)

    Ganegoda, Hasitha; Jensen, David S.; Olive, Daniel; Cheng, Lidens; Segre, Carlo U.; Linford, Matthew R.; Terry, Jeff

    2012-03-01

    Porous graphitic carbon (PGC) has unique properties desirable for liquid chromatography applications when used as a stationary phase. The polar retention effect on graphite (PREG) allows efficient separation of polar and non-polar solutes. Perfluorinated hydrocarbons however lack polarizabilty and display strong lipo- and hydrophobicity, hence common lipophilic and hydrophilic analytes have low partition coefficiency in fluorinated stationary phases. Attractive interaction between fluorinated stationary phase and fluorinated analytes results in strong retention compared to non-fluorinated analytes. In order to change the selectivities of PGC, it is necessary to develop a bonded PGC stationary phase. In this study, we have synthesized perfluorinated, PGC using hepatadecafluoro-1-iodooctane, under different temperature conditions. Surface functionalization of the raw material was studied using photoelectron spectroscopy (PES). Results indicate the existence of fluorine containing functional groups, -CF, -CF2 along with an intercalated electron donor species. Multiple oxygen functional groups were also observed, likely due to the presence of oxygen in the starting material. These oxygen species may be responsible for significant modifications to planer and tetrahedral carbon ratios.

  20. Photoemission studies of fluorine functionalized porous graphitic carbon

    Energy Technology Data Exchange (ETDEWEB)

    Ganegoda, Hasitha; Olive, Daniel; Cheng, Lidens; Segre, Carlo U.; Terry, Jeff [Department of Physics, Illinois Institute of Technology, Chicago, Illinois 60616 (United States); Jensen, David S.; Linford, Matthew R. [Department of Chemistry and Biochemistry, Brigham Young University, Provo, Utah 84602 (United States)

    2012-03-01

    Porous graphitic carbon (PGC) has unique properties desirable for liquid chromatography applications when used as a stationary phase. The polar retention effect on graphite (PREG) allows efficient separation of polar and non-polar solutes. Perfluorinated hydrocarbons however lack polarizabilty and display strong lipo- and hydrophobicity, hence common lipophilic and hydrophilic analytes have low partition coefficiency in fluorinated stationary phases. Attractive interaction between fluorinated stationary phase and fluorinated analytes results in strong retention compared to non-fluorinated analytes. In order to change the selectivities of PGC, it is necessary to develop a bonded PGC stationary phase. In this study, we have synthesized perfluorinated, PGC using hepatadecafluoro-1-iodooctane, under different temperature conditions. Surface functionalization of the raw material was studied using photoelectron spectroscopy (PES). Results indicate the existence of fluorine containing functional groups, -CF, -CF{sub 2} along with an intercalated electron donor species. Multiple oxygen functional groups were also observed, likely due to the presence of oxygen in the starting material. These oxygen species may be responsible for significant modifications to planer and tetrahedral carbon ratios.

  1. Electronic structure of Mo1-x Re x alloys studied through resonant photoemission spectroscopy

    Science.gov (United States)

    Sundar, Shyam; Banik, Soma; Sharath Chandra, L. S.; Chattopadhyay, M. K.; Ganguli, Tapas; Lodha, G. S.; Pandey, Sudhir K.; Phase, D. M.; Roy, S. B.

    2016-08-01

    We studied the electronic structure of Mo-rich Mo1-x Re x alloys (0≤slant x≤slant 0.4 ) using valence band photoemission spectroscopy in the photon energy range 23-70 eV and density of states calculations. Comparison of the photoemission spectra with the density of states calculations suggests that, with respect to the Fermi level E F, the d states lie mostly in the binding energy range 0 to  -6 eV, whereas s states lie in the binding energy range  -4 to  -10 eV. We observed two resonances in the photoemission spectra of each sample, one at about 35 eV photon energy and the other at about 45 eV photon energy. Our analysis suggests that the resonance at 35 eV photon energy is related to the Mo 4p-5s transition and the resonance at 45 eV photon energy is related to the contribution from both the Mo 4p-4d transition (threshold: 42 eV) and the Re 5p-5d transition (threshold: 46 eV). In the constant initial state plot, the resonance at 35 eV incident photon energy for binding energy features in the range E F (BE  =  0) to  -5 eV becomes progressively less prominent with increasing Re concentration x and vanishes for x  >  0.2. The difference plots obtained by subtracting the valence band photoemission spectrum of Mo from that of Mo1-x Re x alloys, measured at 47 eV photon energy, reveal that the Re d-like states appear near E F when Re is alloyed with Mo. These results indicate that interband s-d interaction, which is weak in Mo, increases with increasing x and influences the nature of the superconductivity in alloys with higher x.

  2. Femtosecond time-resolved two-photon photoemission study of organic semiconductor copper phthalocyanine film

    International Nuclear Information System (INIS)

    Tanaka, A.; Tohoku University; University of Rochester, NY; Yan, L.; Watkins, N.J.; Gao, Y.

    2004-01-01

    Full text: Organic semiconductors are recently attracting much interest from the viewpoints of both device and fundamental physics. These organic semiconductors are considered to be important constituents of the future devices, such as organic light-emitting diode, organic field effect transistor, and organic solid-state injection laser. In order to elucidate their detailed physical properties and to develop the future devices, it is indispensable to understand their excited-state dynamics as well as their electronic structures. The femtosecond time-resolved two-photon photoemission (TR-2PPE) spectroscopy is attracting much interest because of its capability to observe the energy-resolved excited electron dynamics. In this work, we have carried out a TR-2PPE study of the organic semiconductor copper phthalocyanine (CuPc) film. Furthermore, we have investigated the detailed electronic structure of CuPc film using the photoemission (PES) and inverse photoemission (IPES) spectroscopies. From the simultaneous PES and IPES measurements for CuPc film with a thickness of 100 nm, the lowest unoccupied molecular orbital (LUMO), highest occupied molecular orbital, and ionization potential of CuPc film have been directly determined. The observed two-photon photoemission (2PPE) spectrum of the present CuPc film, measured with photon energy of about hv=3.3 eV, exhibits a broad feature. From the energy diagram of CuPc film determined by the PES and IPES measurements, the intermediate state observed in the present 2PPE spectrum of CuPc film corresponds to the energy region between about 0.4 and 1.7 eV above the LUMO energy. From the time-resolved pump-probe measurements, it is found that the relaxation lifetimes of excited states in the present CuPc films are very short (all below 50 fs) and monotonously become faster with increasing excitation energy. We attribute this extremely fast relaxation process of photoexcitation to a rapid internal conversion process. From these results

  3. VUV photoemission studies of candidate Large Hadron Collider vacuum chamber materials

    Directory of Open Access Journals (Sweden)

    R. Cimino

    1999-06-01

    Full Text Available In the context of future accelerators and, in particular, the beam vacuum of the Large Hadron Collider (LHC, a 27 km circumference proton collider to be built at CERN, VUV synchrotron radiation (SR has been used to study both qualitatively and quantitatively candidate vacuum chamber materials. Emphasis is given to show that angle and energy resolved photoemission is an extremely powerful tool to address important issues relevant to the LHC, such as the emission of electrons that contributes to the creation of an electron cloud which may cause serious beam instabilities and unmanageable heat loads on the cryogenic system. Here we present not only the measured photoelectron yields from the proposed materials, prepared on an industrial scale, but also the energy and in some cases the angular dependence of the emitted electrons when excited with either a white light (WL spectrum, simulating that in the arcs of the LHC, or monochromatic light in the photon energy range of interest. The effects on the materials examined of WL irradiation and /or ion sputtering, simulating the SR and ion bombardment expected in the LHC, were investigated. The studied samples exhibited significant modifications, in terms of electron emission, when exposed to the WL spectrum from the BESSY Toroidal Grating Monochromator beam line. Moreover, annealing and ion bombardment also induce substantial changes to the surface thereby indicating that such surfaces would not have a constant electron emission during machine operation. Such characteristics may be an important issue to define the surface properties of the LHC vacuum chamber material and are presented in detail for the various samples analyzed. It should be noted that all the measurements presented here were recorded at room temperature, whereas the majority of the LHC vacuum system will be maintained at temperatures below 20 K. The results cannot therefore be directly applied to these sections of the machine until

  4. Electron Band Alignment at Interfaces of Semiconductors with Insulating Oxides: An Internal Photoemission Study

    Directory of Open Access Journals (Sweden)

    Valeri V. Afanas'ev

    2014-01-01

    Full Text Available Evolution of the electron energy band alignment at interfaces between different semiconductors and wide-gap oxide insulators is examined using the internal photoemission spectroscopy, which is based on observations of optically-induced electron (or hole transitions across the semiconductor/insulator barrier. Interfaces of various semiconductors ranging from the conventional silicon to the high-mobility Ge-based (Ge, Si1-xGex, Ge1-xSnx and AIIIBV group (GaAs, InxGa1-xAs, InAs, GaP, InP, GaSb, InSb materials were studied revealing several general trends in the evolution of band offsets. It is found that in the oxides of metals with cation radii larger than ≈0.7 Å, the oxide valence band top remains nearly at the same energy (±0.2 eV irrespective of the cation sort. Using this result, it becomes possible to predict the interface band alignment between oxides and semiconductors as well as between dissimilar insulating oxides on the basis of the oxide bandgap width which are also affected by crystallization. By contrast, oxides of light elements, for example, Be, Mg, Al, Si, and Sc exhibit significant shifts of the valence band top. General trends in band lineup variations caused by a change in the composition of semiconductor photoemission material are also revealed.

  5. Photoemission spectroscopy study on interfacial energy level alignments in tandem organic light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Ou, Qing-Dong; Li, Chi; Li, Yan-Qing, E-mail: yqli@suda.edu.cn; Tang, Jian-Xin, E-mail: jxtang@suda.edu.cn

    2015-10-01

    Highlights: • The interface energetics of tandem OLEDs is overviewed. • Energy level alignment in CGLs is addressed via photoemission spectroscopy. • The n-type doping effect with cesium compounds is discussed. • Hole injection barrier is dependent on oxygen vacancies in transition metal oxides. • Device lifetime of tandem OLEDs is sensitive to interfacial stability of CGLs. - Abstract: Organic light-emitting diodes (OLEDs) using a tandem structure offer a highly attractive option for the applications of next-generation flat panel displays and solid-state lighting due to the extremely high brightness and efficiency along with the long operational lifetime. In general, reliable information about interface energetics of the charge generation layers (CGLs), which plays the central role in charge generation and carrier injection into the stacked emission units, is highly desirable and advantageous for interface engineering and the performance optimization of tandem OLEDs. In this review, our recent studies on tandem OLEDs are overviewed, especially from interface energetics perspective via photoemission spectroscopy. The electronic structures of various transition metal oxide (TMO)-based CGLs and their role in charge generation process are reviewed, addressing the n-type doping impact of organic layers in CGLs, thermal annealing-induced oxygen vacancy in TMOs, and the interfacial stability of CGLs on the device operational lifetime. The resulting energy level alignments are summarized in correspondence with tandem OLED performance.

  6. A Dust Grain Photoemission Experiment

    Science.gov (United States)

    Venturini, C. C.; Spann, J. F., Jr.; Abbas, M. M.; Comfort, R. H.

    2000-01-01

    A laboratory experiment has been developed at Marshall Space Flight Center to study the interaction of micron-sized particles with plasmas and FUV radiation. The intent is to investigate the conditions under which particles of various compositions and sizes become charged, or discharged, while exposed to an electron beam and/or UV radiation. This experiment uses a unique laboratory where a single charged micron size particle is suspended in a quadrupole trap and then subjected to a controlled environment. Tests are performed using different materials and sizes, ranging from 10 microns to 1 micron, to determine the particle's charge while being subjected to an electron beam and /or UV radiation. The focus of this presentation will be on preliminary results from UV photoemission tests, but past results from electron beam, secondary electron emission tests will also be highlighted. A monochromator is used to spectrally resolve UV in the 120 nm to 300 nm range. This enables photoemission measurements as a function of wavelength. Electron beam tests are conducted using I to 3 micron sized aluminum oxide particles subjected to energies between 100 eV to 3 KeV. It was found that for both positive and negative particles the potential tended toward neutrality over time with possible equilibrium potentials between -0.8 Volts and 0.8 Volts.

  7. Angle-resolved photoemission study of NiO and CoO

    International Nuclear Information System (INIS)

    Shen, Z.X.; Lindberg, P.A.P.; Shih, C.K.; Spicer, W.E.; Lindau, I.

    1989-01-01

    The authors report an angle-resolved photoemission investigation of the electronic structures of NiO and CoO. The lattice effects on the photoemission spectra of these highly correlated materials are important. The magnitudes of dispersions of the oxygen bands agree with band calculations, but the experimental data of the localized 3d bands do not agree with the band calculations

  8. A photoemission study of interfaces between organic semiconductors and Co as well as Al2O3/Co contacts

    NARCIS (Netherlands)

    Grobosch, M.; Schmidt, C.; Naber, W.J.M.; van der Wiel, Wilfred Gerard; Knupfer, M.

    We have studied the energy-level alignment of ex situ, acetone cleaned Co and Al2O3/Co contacts to the organic semiconductors pentacene and rubrene by combined X-ray and ultraviolet photoemission spectroscopy. Our results demonstrate that the work function under these conditions is smaller than in

  9. Reactive molecular beam epitaxial growth and in situ photoemission spectroscopy study of iridate superlattices

    Directory of Open Access Journals (Sweden)

    C. C. Fan

    2017-08-01

    Full Text Available High-quality (001-oriented perovskite [(SrIrO3m/(SrTiO3] superlattices (m=1/2, 1, 2, 3 and ∞ films have been grown on SrTiO3(001 epitaxially using reactive molecular beam epitaxy. Compared to previously reported superlattices synthesized by pulsed laser deposition, our superlattices exhibit superior crystalline, interface and surface structure, which have been confirmed by high-resolution X-ray diffraction, scanning transmission electron microscopy and atomic force microscopy, respectively. The transport measurements confirm a novel insulator-metal transition with the change of dimensionality in these superlattices, and our first systematic in situ photoemission spectroscopy study indicates that the increasing strength of effective correlations induced by reducing dimensionality would be the dominating origin of this transition.

  10. Thermal stability and chemical bonding states of AlOxNy/Si gate stacks revealed by synchrotron radiation photoemission spectroscopy

    International Nuclear Information System (INIS)

    He, G.; Toyoda, S.; Shimogaki, Y.; Oshima, M.

    2010-01-01

    Annealing-temperature dependence of the thermal stability and chemical bonding states of AlO x N y /SiO 2 /Si gate stacks grown by metalorganic chemical vapor deposition (MOCVD) using new chemistry was investigated by synchrotron radiation photoemission spectroscopy (SRPES). Results have confirmed the formation of the AlN and AlNO compounds in the as-deposited samples. Annealing the AlO x N y samples in N 2 ambient in 600-800 deg. C promotes the formation of SiO 2 component. Meanwhile, there is no formation of Al-O-Si and Al-Si binding states, suggesting no interdiffusion of Al with the Si substrate. A thermally induced reaction between Si and AlO x N y to form volatile SiO and Al 2 O is suggested to be responsible for the full disappearance of the Al component that accompanies annealing at annealing temperature of 1000 deg. C. The released N due to the breakage of the Al-N bonding will react with the SiO 2 interfacial layer and lead to the formation of the Si 3 -N-O/Si 2 -N-O components at the top of Si substrate. These results indicate high temperature processing induced evolution of the interfacial chemistry and application range of AlO x N y /Si gate stacks in future CMOS devices.

  11. Real-time monitoring of initial thermal oxidation on Si(001) surfaces by synchrotron radiation photoemission spectroscopy

    CERN Document Server

    Yoshigoe, A; Teraoka, Y

    2003-01-01

    The thermal oxidation of Si(001) surfaces at 860 K, 895 K, 945 K and 1000 K under the O sub 2 pressure of 1 x 10 sup - sup 4 Pa has been investigated by time-resolved photoemission measurements with synchrotron radiation. Based on time evolution analyses by reaction kinetics models, it was found that the oxidation at 860 K, 895 K and 945 K has progressed with the Langmuir adsorption type, whereas the oxidation at 1000 K has showed the character of the two-dimensional island growth involving SiO desorption. The oxidation rates increases with increasing surface temperature in the passive oxidation condition. The time evolution of each Si oxidation state (Si sup n sup + : n = 1, 2, 3, 4) derived from the Si-2p core-level shifts has also been analyzed. The results revealed that the thermal energy contribution to the migration process of the adsorbed oxygen and the emission of the bulk silicon atoms. Thus, the fraction of the Si sup 4 sup + bonding state, i.e. SiO sub 2 structure, was increased. (author)

  12. The interaction of oxygen with TiC(001): Photoemission and first-principles studies

    International Nuclear Information System (INIS)

    Rodriguez, J.A.; Liu, P.; Dvorak, J.; Jirsak, T.; Gomes, J.; Takahashi, Y.; Nakamura, K.

    2004-01-01

    High-resolution photoemission and first-principles density-functional slab calculations were used to study the interaction of oxygen with a TiC(001) surface. Atomic oxygen is present on the TiC(001) substrate after small doses of O 2 at room temperature. A big positive shift (1.5-1.8 eV) was detected for the C 1s core level. These photoemission studies suggest the existence of strong O↔C interactions. A phenomenon corroborated by the results of first-principles calculations, which show a CTiTi hollow as the most stable site for the adsorption of O. Ti and C atoms are involved in the adsorption and dissociation of the O 2 molecule. In general, the bond between O and the TiC(001) surface contains a large degree of ionic character. The carbide→O charge transfer is substantial even at high coverages (>0.5 ML) of oxygen. At 500 K and large doses of O 2 , oxidation of the carbide surface occurs with the removal of C and formation of titanium oxides. There is an activation barrier for the exchange of Ti-C and Ti-O bonds which is overcome only by the formation of C-C or C-O bonds on the surface. The mechanism for the removal of a C atom as CO gas involves a minimum of two O adatoms, and three O adatoms are required for the formation of CO 2 gas. Due to the high stability of TiC, an O adatom alone cannot induce the generation of a C vacancy in a flat TiC(001) surface

  13. High resolution hard X-ray photoemission using synchrotron radiation as an essential tool for characterization of thin solid films

    International Nuclear Information System (INIS)

    Kim, J.J.; Ikenaga, E.; Kobata, M.; Takeuchi, A.; Awaji, M.; Makino, H.; Chen, P.P.; Yamamoto, A.; Matsuoka, T.; Miwa, D.; Nishino, Y.; Yamamoto, T.; Yao, T.; Kobayashi, K.

    2006-01-01

    Recently, we have shown that hard X-ray photoemission spectroscopy using undulator X-rays at SPring-8 is quite feasible with both high resolution and high throughput. Here we report an application of hard X-ray photoemission spectroscopy to the characterization of electronic and chemical states of thin solid films, for which conventional PES is not applicable. As a typical example, we focus on the problem of the scatter in the reported band-gap values for InN. We show that oxygen incorporation into the InN film strongly modifies the valence and plays a crucial role in the band gap problem. The present results demonstrate the powerful applicability of high resolution photoemission spectroscopy with hard X-rays from a synchrotron source

  14. Hard X-ray photoemission spectroscopy

    International Nuclear Information System (INIS)

    Kobayashi, Keisuke

    2009-01-01

    Except in the very early stage of the development of X-ray photoemission spectroscopy (XPS) by Kai Siegbahn and his coworkers, the excitation sources for XPS studies have predominantly been the Al Kα and Mg Kα emission lines. The advent of synchrotron radiation sources opened up the possibility of tuning the excitation photon energy with much higher throughputs for photoemission spectroscopy, however the excitation energy range was limited to the vacuum ultra violet and soft X-ray regions. Over the past 5-6 years, bulk-sensitive hard X-ray photoemission spectroscopy using high-brilliance high-flux X-rays from third generation synchrotron radiation facilities has been developed. This article reviews the history of HXPES covering the period from Kai Siegbahn and his coworkers' pioneering works to the present, and describes the fundamental aspects, instrumentation, applications to solid state physics, applied physics, materials science, and industrial applications of HXPES. Finally, several challenging new developments which have been conducted at SPring-8 by collaborations among several groups are introduced.

  15. Photoemission electron microscopy for the study of ferromagnetic and antiferromagnetic materials

    International Nuclear Information System (INIS)

    Anders, Simone; Scholl, Andreas; Nolting, Frithjof; Padmore, Howard A.; Luening, Jan; Stoehr, Joachim; Scheinfein, Michael

    2000-01-01

    Photoemission electron microscopy (PEEM) is a full field imaging technique where x-ray exited electrons are used to form an image of the sample surface as a function of the x-ray photon energy and polarization. Contrast in PEEM can be due to a number of mechanisms including topographical, work function, elemental, chemical, polarization, x-ray magnetic circular and linear dichroism contrast. This wide range of contrast mechanisms together with the surface sensitivity and high spatial resolution make PEEM a very useful tool for the study of magnetic materials. PEEM-II is a new microscope installed at the bending magnet beamline 7.3.1.1 of the Advanced Light Source. In the present paper we describe the design and features of PEEM-II, and show results of our recent studies. Using PEEM and its elemental specificity, it is possible to investigate the various layers in magnetic multilayer structures independently. The experiments described here include the investigation of the switching behavior of magnetic multilayer structures that are of interest for magnetic RAM applications. The study of antiferromagnetic surfaces and thin films are of great importance for devices based on the effect of exchange bias. To date, studies at high-spatial-resolution of exchange bias systems has been difficult because of the lack of appropriate investigation methods. Here we demonstrate how PEEM has been used to image antiferromagnetic structure on surfaces with high spatial resolution

  16. Photoemission study of the development of the Ti/GaAs(110) interface

    International Nuclear Information System (INIS)

    Ruckman, M.W.; del Giudice, M.; Joyce, J.J.; Weaver, J.H.

    1986-01-01

    Photoemission spectra of the Ga and As 3d core levels, the Ti 3p core levels, and the valence bands have been used to study the formation of the Ti/GaAs(110) interface. These results indicate that a multicomponent interfacial zone forms with reaction initiated at ultralow coverage and a rapid shift of E/sub F/ as the Schottky barrier forms (core-level shift 625 meV). After the onset of reaction, the Ga 3d core level shifts continuously to lower binding energy with increasing coverage (total shift of 1.66 eV by roughly-equal60 A Ti deposition). The As core-level profile indicates immediate reaction, the formation of two Ti: As bonding configurations at low coverage, and the appearance of another which persists to very high Ti coverage (> or =160 A) and is characteristic of a Ti-metal-rich environment. Core-level intensity profiles show preferential out-diffusion of As at every stage of interface formation. Core studies of the evolving Ti 3p emission show gradual convergence to bulk Ti as the overlayer becomes increasingly Ti rich. Likewise, valence-band studies reveal predominantly As-derived states below metal d states at E/sub F/. Comparison to previous results for Cr, V, Ce, and Sm overlayers on GaAs shows parallel trends in interface formation with differences related to the metal overlayer

  17. Electronic properties of novel topological quantum materials studied by angle-resolved photoemission spectroscopy (ARPES)

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Yun [Iowa State Univ., Ames, IA (United States)

    2016-12-17

    The discovery of quantum Hall e ect has motivated the use of topology instead of broken symmetry to classify the states of matter. Quantum spin Hall e ect has been proposed to have a separation of spin currents as an analogue of the charge currents separation in quantum Hall e ect, leading us to the era of topological insulators. Three-dimensional analogue of the Dirac state in graphene has brought us the three-dimensional Dirac states. Materials with three-dimensional Dirac states could potentially be the parent compounds for Weyl semimetals and topological insulators when time-reversal or space inversion symmetry is broken. In addition to the single Dirac point linking the two dispersion cones in the Dirac/Weyl semimetals, Dirac points can form a line in the momentum space, resulting in a topological node line semimetal. These fascinating novel topological quantum materials could provide us platforms for studying the relativistic physics in condensed matter systems and potentially lead to design of new electronic devices that run faster and consume less power than traditional, silicon based transistors. In this thesis, we present the electronic properties of novel topological quantum materials studied by angle-resolved photoemission spectroscopy (ARPES).

  18. A photoemission study of evaporated manganese on gallium arsenide at elevated temperatures

    International Nuclear Information System (INIS)

    James, D.; Tadich, A.; Riley, J.; Leckey, R.; Emtsev, K.; Seyller, T.; Ley, L.

    2004-01-01

    Full text: The interaction between metals and semiconductors has been extensively researched to achieve an understanding of the formation of Schottky barriers and conditions for low resistance electrical connections to devices. The possibility of the use of magnetic materials to generate spin polarised currents, so called spintronics, and has extended this interest to metals that have not traditionally been used for such contacts. Manganese has recently been used as one element in GaAs and ZnSe based devices so its interaction with such surfaces is of interest. An interest that motivates this study is the possibility of lattice-matched growth of transition metal layers on semiconductors. Lattice mismatch initially appeared to inhibit single crystal transition metal growth, but it has been reported that lattice matched growth can occur in some cases. It is thought that reactions at the interface form a buffer layer, which allows for epitaxial growth via a more comparable lattice constant. We report studies of the growth of manganese films on GaAs(100) at several substrate temperatures using angle resolved photoemission, the diffusion of the Mn in the GaAs substrates using SIMS and the morphology of the layers using AFM images

  19. Band alignment in organic devices: Photoemission studies of model oligomers on In2O3

    International Nuclear Information System (INIS)

    Blyth, R. I. R.; Duschek, R.; Koller, G.; Netzer, F. P.; Ramsey, M. G.

    2001-01-01

    The interfaces of In 2 O 3 , a model for indium - tin - oxide (ITO), with benzene, thiophene, and benzaldehyde, models for technologically important organic molecules, are studied using angle resolved ultraviolet photoemission and work function measurements. Band alignment diagrams for hypothetical Al/organic/ITO devices have been drawn, using values determined from this work and previously published studies of these molecules on Al(111). The similarity between the bonding of benzene and thiophene on Al(111) and In 2 O 3 , i.e., largely electrostatic, leads to near identical alignment at both metal and oxide interfaces. This indicates that clean Al and ITO will make a very poor electron/hole injecting pair. We suggest that the apparent efficiency of Al as an electron injecting contact in real devices is due to the presence of oxygen at the Al/organic interface. For benzaldehyde the interaction with In 2 O 3 is largely electrostatic, in contrast to the covalent bonds formed on Al(111). This leads to very different alignment at the Al and oxide interfaces, showing the importance of the particular organic - inorganic interaction in determining band alignment. [copyright] 2001 American Institute of Physics

  20. Soft X-ray photoemission study of organic conductors BEDT-TTF and BEDO-TTF salts

    International Nuclear Information System (INIS)

    Tsunekawa, M.; Sekiyama, A.; Imada, S.; Saita, T.; Maesato, M.; Yamochi, H.; Saito, G.; Suga, S.

    2005-01-01

    We have performed a soft X-ray photoemission (PES) study of quasi-two-dimensional organic conductors BEDT-TTF (ET) and BEDO-TTF (BO) salts. We have clarified the difference in the electronic states between the bulk and surface insulating layers. The difference of the electronic states between ET and BO molecules is also found. On the other hand, the spectral weight in the vicinity of Fermi level is suppressed as reported by the low-energy PES

  1. Photoemission and electron-stimulated desorption studies of H on W(110): Single- versus two-binding-site models

    International Nuclear Information System (INIS)

    Weng, S.

    1982-01-01

    The chemisorption of H on W(110) at room temperature is studied with the use of angle-integrated photoemission and electron-stimulated desorption (ESD). The ESD cross sections of H + are found to be sol low that no significant H + signals with meaningful ion energy distributions are observed. The photoemission results show, however, two types of H adatoms, referred to as β 2 and β 1 states, for this chemisorptive system. Both states are found to appear simultaneously rather than sequentially as suggested by previous studies, and exhibit a simple 1-theta adsorption kinetics with different initial sticking coefficients. The β 2 state induces two binding energy levels at -2.0 and -6.0 eV, respectively, whereas the β 1 state induces a level at -3.8 eV. The work-function change (with a maximum value of -0.45 eV) is found to follow exactly with the intensity of the β 2 state. These results are found to be compatible with the two-binding-site model, inherently suggested by the reflection high-enery electron-diffraction data. However, the results can also be consistent with a single-binding-site model suggested by a recent angle-resolved photoemission and inelastic electron scattering study. A model based on the present results is proposed and critically compared with previous studies. Unresolved problems associated with both single- and two-binding-site models are also discussed

  2. Band alignments in Fe/graphene/Si(001) junctions studied by x-ray photoemission spectroscopy

    Science.gov (United States)

    Le Breton, J.-C.; Tricot, S.; Delhaye, G.; Lépine, B.; Turban, P.; Schieffer, P.

    2016-08-01

    The control of tunnel contact resistance is of primary importance for semiconductor-based spintronic devices. This control is hardly achieved with conventional oxide-based tunnel barriers due to deposition-induced interface states. Manipulation of single 2D atomic crystals (such as graphene sheets) weakly interacting with their substrate might represent an alternative and efficient way to design new heterostructures for a variety of different purposes including spin injection into semiconductors. In the present paper, we study by x-ray photoemission spectroscopy the band alignments and interface chemistry of iron-graphene-hydrogenated passivated silicon (001) surfaces for a low and a high n-doping concentration. We find that the hydrogen passivation of the Si(001) surface remains efficient even with a graphene sheet on the Si(001) surface. For both doping concentrations, the semiconductor is close to flat-band conditions which indicates that the Fermi level is unpinned on the semiconductor side of the Graphene/Si(001):H interface. When iron is deposited on the graphene/Si(001):H structures, the Schottky barrier height remains mainly unaffected by the metallic overlayer with a very low barrier height for electrons, a sought-after property in semiconductor based spintronic devices. Finally, we demonstrate that the graphene layer intercalated between the metal and semiconductor also serves as a protection against iron-silicide formation even at elevated temperatures preventing from the formation of a Si-based magnetic dead layer.

  3. Band alignments in Fe/graphene/Si(001) junctions studied by x-ray photoemission spectroscopy

    International Nuclear Information System (INIS)

    Le Breton, J.-C.; Tricot, S.; Delhaye, G.; Lépine, B.; Turban, P.; Schieffer, P.

    2016-01-01

    The control of tunnel contact resistance is of primary importance for semiconductor-based spintronic devices. This control is hardly achieved with conventional oxide-based tunnel barriers due to deposition-induced interface states. Manipulation of single 2D atomic crystals (such as graphene sheets) weakly interacting with their substrate might represent an alternative and efficient way to design new heterostructures for a variety of different purposes including spin injection into semiconductors. In the present paper, we study by x-ray photoemission spectroscopy the band alignments and interface chemistry of iron–graphene-hydrogenated passivated silicon (001) surfaces for a low and a high n-doping concentration. We find that the hydrogen passivation of the Si(001) surface remains efficient even with a graphene sheet on the Si(001) surface. For both doping concentrations, the semiconductor is close to flat-band conditions which indicates that the Fermi level is unpinned on the semiconductor side of the Graphene/Si(001):H interface. When iron is deposited on the graphene/Si(001):H structures, the Schottky barrier height remains mainly unaffected by the metallic overlayer with a very low barrier height for electrons, a sought-after property in semiconductor based spintronic devices. Finally, we demonstrate that the graphene layer intercalated between the metal and semiconductor also serves as a protection against iron-silicide formation even at elevated temperatures preventing from the formation of a Si-based magnetic dead layer.

  4. High resolution photoemission study of Nd1-xSrxMnO3

    International Nuclear Information System (INIS)

    Togashi, T.; Osawa, H.; Shin, S.; Tanaka, K.; Isozumi, Y.; Iwazumi, T.; Nozawa, S.

    2004-01-01

    Full text:Nd 1-x SrxMnO 3 shows the negative colossal magnetoresistance and various electronic phases. In order to reveal their states, we have performed a high- resolution Mn 2p-3d resonance photoemission (RPES) study of Nd 1-x SrxMnO 3 with an energy resolution of 100 meV at BL25SU in SPring-8. Figure 1 shows the Mn 2p-3d RPES spectra of Nd 1-x SrxMnO 3 . It is found that the spectral line shape in the ground-state phases (GS) at low temperatures is closely related to the shape of MnO 6 octahedra depending on x due to a static Jahn- Teller (JT) effect while the line shape in the paramagnetic insulator (PI) phase near room temperature is qualitatively similar to each other irrespective of x. These results strongly suggest that the dynamical and static JT effects are responsible for the 3d electronic states at high and low temperatures, respectively

  5. Spin-resolved x-ray photoemission studies of ferromagnetic metals

    International Nuclear Information System (INIS)

    Klebanoff, L.E.

    1996-01-01

    Recent spin-resolved x-ray photoelectron spectroscopy (SRXPS) studies of ferromagnetic metals are reviewed. SRXPS studies of metallic Fe, Co, Co 66 Fe 4 Ni 1 B 14 Si 15 , and Ni demonstrate that core-level photoemission, and the itinerant electron response to core-hole creation, are highly spin-dependent. The exchange splitting of the Fe 2p 3/2 level is found to be 0.48±0.05 eV. Lifetime broadening results for the Fe 2p 3/2 N↑ (majority spin) and N↓ (minority spin) components indicate conservation of spin in core-hole filling processes involving the valence band. SRXPS study of the Fe 2p 3/2 peak asymmetry α reveals a dependence of electron endash hole excitation on the spin of the core hole. Spin analysis of the Fe 3s XPS line shape shows it to be a three-component spectrum, rather than the two-component line shape assumed previously. A photon energy dependence of one of the Fe 3s components explains disagreement among previous Fe 3s XPS results. Comparisons of SRXPS from Co metal and Co 66 Fe 4 Ni 1 B 14 Si 15 directly demonstrate the effect of a reduced atomic magnetic moment on the spin dependence of core-level XPS. The behavior of lifetime broadenings for the N↑ and N↓ Co 2p 3/2 components show that the reduced Co magnetic moment found in the Co 66 Fe 4 Ni 1 B 14 Si 15 amorphous glass is due to the transfer of ↑-spin valence electron density to the ↓-spin valence band upon glass formation. SRXPS also allows investigation of spin-dependent core-hole screening processes and satellite production, as demonstrated in SRXPS studies of ferromagnetic Ni. Future directions of SRXPS are also explored. copyright 1996 American Vacuum Society

  6. In situ photoemission spectroscopy using synchrotron radiation for O2 translational kinetic energy induced oxidation processes of partially-oxidized Si(001) surfaces

    International Nuclear Information System (INIS)

    Teraoka, Yuden; Yoshigoe, Akitaka

    2001-01-01

    The influence of translational kinetic energy of incident O 2 molecules for the passive oxidation process of partially-oxidized Si(001) surfaces has been studied by photoemission spectroscopy. The translational kinetic energy of O 2 molecules was controlled up to 3 eV by a supersonic seed beam technique using a high temperature nozzle. Two translational kinetic energy thresholds (1.0 eV and 2.6 eV) were found out in accordance with the first-principles calculation for the oxidation of clean surfaces. Si-2p photoemission spectra measured in representative translational kinetic energies revealed that the translational kinetic energy dependent oxidation of dimers and the second layer (subsurface) backbonds were caused by the direct dissociative chemisorption of O 2 molecules. Moreover, the difference in chemical bonds for oxygen atoms was found out to be as low and high binding energy components in O-1s photoemission spectra. Especially, the low binding energy component increased with increasing the translational kinetic energy that indicates the translational kinetic energy induced oxidation in backbonds. (author)

  7. Chemical bonding in Tl cuprates studied by x-ray photoemission

    International Nuclear Information System (INIS)

    Vasquez, R.P.; Siegal, M.P.; Overmyer, D.L.; Ren, Z.F.; Lao, J.Y.; Wang, J.H.

    1999-01-01

    Epitaxial thin films of the Tl cuprate superconductors Tl 2 Ba 2 CaCu 2 O 8 , Tl 2 Ba 2 Ca 2 Cu 3 O 10 , and Tl 0.78 Bi 0.22 Ba 0.4 Sr 1.6 Ca 2 Cu 3 O 9-δ are studied with x-ray photoemission spectroscopy. These data, together with previous measurements in this lab of Tl 2 Ba 2 CuO 6+δ and TlBa 2 CaCu 2 O 7-δ , comprise a comprehensive data set for a comparative study of Tl cuprates with a range of chemical and electronic properties. In the Cu 2p spectra, a larger energy separation between the satellite and main peaks (E s -E m ) and a lower intensity ratio (I s /I m ) are found to correlate with higher values of T c . Analysis of these spectra within a simple configuration interaction model suggests that higher values of T c are related to low values of the O 2p→Cu 3d charge transfer energy. In the O 1s region, a smaller bond length between Ba and Cu-O planar oxygen is found to correlate with a lower binding energy for the signal associated with Cu-O bonding, most likely resulting from the increased polarization screening by Ba 2+ ions. For samples near optimum doping, maximum T c is observed to occur when the Tl 4f 7/2 binding energy is near 117.9 eV, which is near the middle of the range of values observed for Tl cuprates. Higher Tl 4f 7/2 binding energies, corresponding to formal oxidation states nearer Tl 1+ , are also found to correlate with longer bond lengths between Ba and Tl-O planar oxygen, and with higher binding energies of the O 1s signal associated with Tl-O bonding. copyright 1999 The American Physical Society

  8. Core and valence level photoemission and photoabsorption study of icosahedral Al-Pd-Mn quasicrystals

    International Nuclear Information System (INIS)

    Horn, K; Theis, W; Paggel, J J; Barman, S R; Rotenberg, E; Ebert, Ph; Urban, K

    2006-01-01

    The electronic structure of quasicrystalline Al-Pd-Mn is investigated by means of valence and core level photoelectron spectroscopy. Variations of the photoionization cross section in the constituents' valence electronic levels as a function of photon energy are used to identify contributions from the different atomic species, in particular near the Pd 4d Cooper minimum. Resonant photoemission at the Mn 2p absorption edge shows the contribution of the Mn 3d states to the density of states in a region near the Fermi level. The asymmetry of Pd 3d and Mn 2p core level photoemission lines, and its difference for emission from metallic and quasicrystalline phases, are utilized to infer the contributions of the different constituents to the density of states at the Fermi level

  9. Rb-intercalated C{sub 60} compounds studied by photoemission spectroscopies

    Energy Technology Data Exchange (ETDEWEB)

    Brambilla, A [INFM - Dipartimento di Fisica, Politecnico di Milano, p.za L. da Vinci 32, I-20133 Milan (Italy); Giovanelli, L [Sincrotrone Trieste S.C.p.A., Strada Statale 14, Km 163.5, I-34012 Basovizza, Trieste (Italy); Vilmercati, P [Sincrotrone Trieste S.C.p.A., Strada Statale 14, Km 163.5, I-34012 Basovizza, Trieste (Italy); Cattoni, A [INFM - Dipartimento di Fisica, Politecnico di Milano, p.za L. da Vinci 32, I-20133 Milan (Italy); Biagioni, P [INFM - Dipartimento di Fisica, Politecnico di Milano, p.za L. da Vinci 32, I-20133 Milan (Italy); Goldoni, A [Sincrotrone Trieste S.C.p.A., Strada Statale 14, Km 163.5, I-34012 Basovizza, Trieste (Italy); Finazzi, M [INFM - Dipartimento di Fisica, Politecnico di Milano, p.za L. da Vinci 32, I-20133 Milan (Italy); Duo, L [INFM - Dipartimento di Fisica, Politecnico di Milano, p.za L. da Vinci 32, I-20133 Milan (Italy)

    2005-06-15

    We report on a combined photoemission and inverse photoemission spectroscopy analysis on Rb{sub x}C{sub 60} compounds with different stoichiometries (0-bar x-bar 6). Apart from shifts and broadening of the spectral features associated to the different phase formed, we observe in the RbC{sub 60} phase the presence of the highest occupied molecular orbital (HOMO) shoulder and of its symmetric (with respect to the Fermi level) empty state. According to calculations, the metallicity of this phase and the presence of these electronic states may be taken as a fingerprint of the interplay between electron-electron and electron-phonon interactions in determining the electronic behavior of alkali metal fullerides.

  10. Magnetic dichroism in UV photoemission at off-normal emission: Study of the valence bands

    International Nuclear Information System (INIS)

    Venus, D.; Kuch, W.; Lin, M.; Schneider, C.M.; Ebert, H.; Kirschner, J.

    1997-01-01

    Magnetic dichroism of angle-resolved UV photoemission from fcc Co/Cu(001) thin films has been measured using linearly p-polarized light, and a coplanar geometry where the light and photoelectron wave vectors are antiparallel, and both are perpendicular to the in-plane sample magnetization. This geometry emphasizes information about state dispersion due to the crystalline symmetry. An orderly dispersion of the features in the magnetic dichroism over a wide range of off-normal angles of electron emission is related in detail to the bulk band structure of fcc Co. The measurements confirm the practical utility of magnetic dichroism experiments as a relatively simple complement to spin-resolved photoemission. copyright 1997 The American Physical Society

  11. Dilution effect on the U 5f states in Au matrix: a photoemission spectroscopy study

    Czech Academy of Sciences Publication Activity Database

    Eloirdi, R.; Gouder, T.; Wastin, F.; Huber, F.; Shick, Alexander; Kolorenč, Jindřich

    2011-01-01

    Roč. 84, č. 23 (2011), 235143/1-235143/7 ISSN 1098-0121 R&D Projects: GA ČR(CZ) GAP204/10/0330; GA AV ČR IAA100100912 Institutional research plan: CEZ:AV0Z10100520 Keywords : x-ray photoemission * electronic-structure * photoelectron- spectroscopy * fermion systems Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.691, year: 2011

  12. Electronic structure of Sr2RuO4 studied by angle-resolved photoemission spectroscopy

    International Nuclear Information System (INIS)

    Iwasawa, H.; Aiura, Y.; Saitoh, T.; Yoshida, Y.; Hase, I.; Ikeda, S.I.; Bando, H.; Kubota, M.; Ono, K.

    2007-01-01

    Electronic structure of the monolayer strontium ruthenate Sr 2 RuO 4 was investigated by high-resolution angle-resolved photoemission spectroscopy. We present photon-energy (hν) dependence of the electronic structure near the Fermi level along the ΓM line. The hν dependence has shown a strong spectral weight modulation of the Ru 4d xy and 4d zx bands

  13. Rb-intercalated C60 compounds studied by Inverse Photoemission Spectroscopy

    International Nuclear Information System (INIS)

    Finazzi, M.; Brambilla, A; Biagioni, P.; Cattoni, A.; Duo, L.; Ciccacci, F.; Braicovich, L.; Giovanelli, L.; Goldoni, A.

    2004-01-01

    Full text: Since the discovery of superconductivity in alkali-doped solid C 60 , the electronic structure of the host material (C 60 ) and the doped compounds (A x C 60 , where A is an alkali metal), has been the subject of a considerable amount of work, both theoretical and experimental. The spectroscopic investigations of the alkali-doped C 60 compounds has been mainly focussed on the valence states, while much less information is available on the unoccupied states. In particular, inverse photoemission data on the complete set of stable Rb x C 60 compounds was, so far, still missing. We have performed Inverse Photoemission (IPE) spectroscopy on Rb x C 60 compounds (x = 1, 3, 4, 6). IPE spectra were obtained using a band-pass photon detector (hv = 9.4 eV, FWHM = 0.7 eV) and scanning the kinetic energy of the electrons impinging on the sample. Rb was evaporated on C 60 films (thickness = 6-12 atomic layers) grown in situ on a Cu(100) substrate. The temperature of the substrate was kept equal to T = 100 deg C, which is lower than the C 60 sublimation temperature. The amount of Rb was checked by measuring the intensity of the C1s and Rb3d photoemission lines. After the required amount of Rb had been deposited, the samples were annealed to distillate the desired stable phase

  14. Gas-phase photoemission with soft x-rays: cross sections and angular distributions

    International Nuclear Information System (INIS)

    Shirley, D.A.; Kobrin, P.H.; Truesdale, C.M.; Lindle, D.W.; Ferrett, T.A.; Heimann, P.A.; Becker, U.; Kerkhoff, H.G.; Southworth, S.H.

    1983-09-01

    A summary is presented of typical gas-phase photoemission studies based on synchrotron radiation in the 50-5000 eV range, using beam lines at the Stanford Synchrotron Radiation Laboratory. Three topics are addressed: atomic inner-shell photoelectron cross sections and asymmetries, correlation peaks in rare gases, and core-level shape resonances in molecules

  15. Angle Integrated Photoemission Study of SmO0.85F0.15FeAs

    International Nuclear Information System (INIS)

    Hong-Wei, Ou; Jia-Feng, Zhao; Yan, Zhang; Da-Wei, Shen; Bo, Zhou; Le-Xian, Yang; Cheng, He; Fei, Chen; Min, Xu; Yan, Chen; Dong-Lai, Feng; Tao, Wu; Xian-Hui, Chen

    2008-01-01

    The electronic structure of the new superconductor SmO 1-x F x FeAs (x = 0.15) is studied by angle-integrated photoemission spectroscopy. Our data show a sharp feature very close to the Fermi energy, and a relative flat distribution of the density of states between 0.5eV and 3eV binding energy, which agrees well with the band structure calculations considering an antiferromagnetic ground state. No noticeable gap opening is observed at 12K below the superconducting transition temperature, indicating the existence of large ungapped regions in the Brillouin zone. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  16. Photoemission study of electronic structure of the half-metallic ferromagnet Co3Sn2S2

    Science.gov (United States)

    Holder, M.; Dedkov, Yu. S.; Kade, A.; Rosner, H.; Schnelle, W.; Leithe-Jasper, A.; Weihrich, R.; Molodtsov, S. L.

    2009-05-01

    Surface electronic structure of polycrystalline and single-crystalline samples of the half-metallic ferromagnet Co3Sn2S2 was studied by means of angle-resolved and core-level photoemissions. The experiments were performed in temperature regimes both above and below a Curie temperature of 176.9 K. The spectroscopic results are compared to local-spin density approximation band-structure calculations for the bulk samples. It is found that the surface sensitive experimental data are generally reproduced by the bulk computation suggesting that the theoretically predicted half-metallic properties of Co3Sn2S2 are retained at the surface.

  17. Chemical Bonding in Tl Cuprates Studied by X-Ray Photoemission

    Energy Technology Data Exchange (ETDEWEB)

    Lao, J.Y.; Overmyer, D.L.; Ren, Z.F.; Siegal, M.P.; Vasquez, R.P.; Wang, J.H.

    1999-04-05

    Epitaxial thin films of the Tl cuprate superconductors Tl{sub 2}Ba{sub 2}CaCu{sub 2}O{sub 8}, Tl{sub 2}Ba{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10}, and TL{sub 0.78}Bi{sub 0.22}Ba{sub 0.4}Sr{sub 1.6}Ca{sub 2}Cu{sub 3}O{sub 9{minus}{delta}} are studied with x-ray photoemission spectroscopy. These data, together with previous measurements in this lab of Tl{sub 2}Ba{sub 2}CuO{sub 6+{delta}} and TlBa{sub 2}CaCu{sub 2}O{sub 7{minus}{delta}}, comprise a comprehensive data set for a comparative study of Tl cuprates with a range of chemical and electronic properties. In the Cu 2p spectra, a larger energy separation between the satellite and main peaks (E{sub s}-E{sub m}) and a lower intensity ratio (I{sub s}/I{sub m}) are found to correlate with higher values of T{sub c}. Analysis of these spectra within a simple configuration interaction model suggests that higher values of T{sub c} are related to low values of the O 2p {r_arrow} Cu 3d charge transfer energy. In the O 1s region, a smaller bond length between Ba and Cu-O planar oxygen is found to correlate with a lower binding energy for the signal associated with Cu-O bonding, most likely resulting from the increased polarization screening by Ba{sup 2+} ions. For samples near optimum doping, maximum T{sub c} is observed to occur when the Tl 4f{sub 7/2} binding energy is near 117.9 eV, which is near the middle of the range of values observed for Tl cuprates. Higher Tl 4f{sub 7/2} binding energies, corresponding to formal oxidation states nearer Tl{sup 1+}, are also found to correlate with longer bond lengths between Ba and Tl-O planar oxygen, and with higher binding energies of the O 1s signal associated with Tl-O bonding.

  18. Chemical bonding in Tl cuprates studied by x-ray photoemission

    Energy Technology Data Exchange (ETDEWEB)

    Vasquez, R.P. [Center for Space Microelectronics Technology, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109-8099 (United States); Siegal, M.P.; Overmyer, D.L. [Sandia National Laboratories, Albuquerque, New Mexico 87185-1421 (United States); Ren, Z.F.; Lao, J.Y.; Wang, J.H. [Materials Synthesis Laboratory, Department of Chemistry, State University of New York, Buffalo, New York 14260-3000 (United States)

    1999-08-01

    Epitaxial thin films of the Tl cuprate superconductors Tl{sub 2}Ba{sub 2}CaCu{sub 2}O{sub 8}, Tl{sub 2}Ba{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10}, and Tl{sub 0.78}Bi{sub 0.22}Ba{sub 0.4}Sr{sub 1.6}Ca{sub 2}Cu{sub 3}O{sub 9{minus}{delta}} are studied with x-ray photoemission spectroscopy. These data, together with previous measurements in this lab of Tl{sub 2}Ba{sub 2}CuO{sub 6+{delta}} and TlBa{sub 2}CaCu{sub 2}O{sub 7{minus}{delta}}, comprise a comprehensive data set for a comparative study of Tl cuprates with a range of chemical and electronic properties. In the Cu 2p spectra, a larger energy separation between the satellite and main peaks (E{sub s}{minus}E{sub m}) and a lower intensity ratio (I{sub s}/I{sub m}) are found to correlate with higher values of T{sub c}. Analysis of these spectra within a simple configuration interaction model suggests that higher values of T{sub c} are related to low values of the O&hthinsp;2p{r_arrow}Cu&hthinsp;3d charge transfer energy. In the O&hthinsp;1s region, a smaller bond length between Ba and Cu-O planar oxygen is found to correlate with a lower binding energy for the signal associated with Cu-O bonding, most likely resulting from the increased polarization screening by Ba{sup 2+} ions. For samples near optimum doping, maximum T{sub c} is observed to occur when the Tl 4f{sub 7/2} binding energy is near 117.9 eV, which is near the middle of the range of values observed for Tl cuprates. Higher Tl&hthinsp;4f{sub 7/2} binding energies, corresponding to formal oxidation states nearer Tl{sup 1+}, are also found to correlate with longer bond lengths between Ba and Tl-O planar oxygen, and with higher binding energies of the O&hthinsp;1s signal associated with Tl-O bonding. {copyright} {ital 1999} {ital The American Physical Society}

  19. Hot Electron Photoemission from Plasmonic Nanostructures: The Role of Surface Photoemission and Transition Absorption

    DEFF Research Database (Denmark)

    Babicheva, Viktoriia; Zhukovsky, Sergei; Ikhsanov, Renat Sh

    2015-01-01

    We study mechanisms of photoemission of hot electrons from plasmonic nanoparticles. We analyze the contribution of "transition absorption", i.e., loss of energy of electrons passing through the boundary between different materials, to the surface mechanism of photoemission. We calculate photoemis......We study mechanisms of photoemission of hot electrons from plasmonic nanoparticles. We analyze the contribution of "transition absorption", i.e., loss of energy of electrons passing through the boundary between different materials, to the surface mechanism of photoemission. We calculate...... photoemission rate and transition absorption for nanoparticles surrounded by various media with a broad range of permittivities and show that photoemission rate and transition absorption follow the same dependence on the permittivity. Thus, we conclude that transition absorption is responsible...

  20. Band structure of Heusler compounds studied by photoemission and tunneling spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Arbelo Jorge, Elena

    2011-07-01

    Heusler compounds are key materials for spintronic applications. They have attracted a lot of interest due to their half-metallic properties predicted by band structure calculations. The aim of this work is to evaluate experimentally the validity of the predictions of half metallicity by band structure calculations for two specific Heusler compounds, Co{sub 2}FeAl{sub 0.3}Si{sub 0.7} and Co{sub 2}MnGa. Two different spectroscopy methods for the analysis of the electronic properties were used: Angular Resolved Ultraviolet Photoemission Spectroscopy (ARUPS) and Tunneling Spectroscopy. Heusler compounds are prepared as thin films by RF-sputtering in an ultra high vacuum system. For the characterization of the samples, bulk and surface crystallographic and magnetic properties of Co{sub 2}FeAl{sub 0.3}Si{sub 0.7} and Co{sub 2}MnGa are studied. X-ray and electron diffraction reveal a bulk and surface crossover between two different types of sublattice order (from B2 to L2{sub 1}) with increasing annealing temperature. X-ray magnetic circular dichroism results show that the magnetic properties in the surface and bulk are identical, although the magnetic moments obtained are 5 % below from the theoretically predicted. By ARUPS evidence for the validity of the predicted total bulk density of states (DOS) was demonstrated for both Heusler compounds. Additional ARUPS intensity contributions close to the Fermi energy indicates the presence of a specific surface DOS. Moreover, it is demonstrated that the crystallographic order, controlled by annealing, plays an important role on broadening effects of DOS features. Improving order resulted in better defined ARUPS features. Tunneling magnetoresistance measurements of Co{sub 2}FeAl{sub 0.3}Si{sub 0.7} and Co{sub 2}MnGa based MTJ's result in a Co{sub 2}FeAl{sub 0.3}Si{sub 0.7} spin polarization of 44 %, which is the highest experimentally obtained value for this compound, although it is lower than the 100 % predicted. For Co

  1. Rb-intercalated C{sub 60} compounds studied by Inverse Photoemission Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Finazzi, M; Brambilla, A; Biagioni, P; Cattoni, A; Duo, L; Ciccacci, F; Braicovich, L [INFM and Dip di Fisica del Politecnico di Milano, Milano (Italy); Giovanelli, L; Goldoni, A [ELETTRA Basovizza (Italy)

    2004-07-01

    Full text: Since the discovery of superconductivity in alkali-doped solid C{sub 60}, the electronic structure of the host material (C{sub 60}) and the doped compounds (A{sub x}C{sub 60}, where A is an alkali metal), has been the subject of a considerable amount of work, both theoretical and experimental. The spectroscopic investigations of the alkali-doped C{sub 60} compounds has been mainly focussed on the valence states, while much less information is available on the unoccupied states. In particular, inverse photoemission data on the complete set of stable Rb{sub x}C{sub 60} compounds was, so far, still missing. We have performed Inverse Photoemission (IPE) spectroscopy on Rb{sub x}C{sub 60} compounds (x = 1, 3, 4, 6). IPE spectra were obtained using a band-pass photon detector (hv = 9.4 eV, FWHM = 0.7 eV) and scanning the kinetic energy of the electrons impinging on the sample. Rb was evaporated on C{sub 60} films (thickness = 6-12 atomic layers) grown in situ on a Cu(100) substrate. The temperature of the substrate was kept equal to T = 100 deg C, which is lower than the C{sub 60} sublimation temperature. The amount of Rb was checked by measuring the intensity of the C1s and Rb3d photoemission lines. After the required amount of Rb had been deposited, the samples were annealed to distillate the desired stable phase.

  2. High-resolution photoemission study of Nd1-xSrxMnO3

    International Nuclear Information System (INIS)

    Fujiwara, H.; Sekiyama, A.; Higashiya, A.; Konoike, K.; Tsunekawa, M.; Yamasaki, A.; Irizawa, A.; Imada, S.; Muro, T.; Noda, K.; Kuwahara, H.; Tokura, Y.; Suga, S.

    2005-01-01

    We have performed the bulk sensitive Mn 2p-3d resonant photoemission for Nd 1-x Sr x MnO 3 (x=0.40, 0.47, 0.50, 0.63) in order to reveal the Mn 3d electronic states. We will report the temperature and doping dependence of the Mn 3d spectral functions. The sudden spectral change for x=0.50 across the FM-COI transition shows the strong influence of the charge-ordering on the Mn 3d electronic states

  3. Laser-excited photoemission spectroscopy study of superconducting boron-doped diamond

    Directory of Open Access Journals (Sweden)

    K. Ishizaka, R. Eguchi, S. Tsuda, T. Kiss, T. Shimojima, T. Yokoya, S. Shin, T. Togashi, S. Watanabe, C.-T. Chen, C.Q. Zhang, Y. Takano, M. Nagao, I. Sakaguchi, T. Takenouchi and H. Kawarada

    2006-01-01

    Full Text Available We have investigated the low-energy electronic state of boron-doped diamond thin film by the laser-excited photoemission spectroscopy. A clear Fermi-edge is observed for samples doped above the semiconductor–metal boundary, together with the characteristic structures at 150×n meV possibly due to the strong electron–lattice coupling effect. In addition, for the superconducting sample, we observed a shift of the leading edge below Tc indicative of a superconducting gap opening. We discuss the electron–lattice coupling and the superconductivity in doped diamond.

  4. Photoemission study of the skutterudite compounds CoSb sub 3 and RhSb sub 3

    CERN Document Server

    Ishii, H; Fujimori, A; Nagamoto, Y; Koyanagi, T; Sofo, J O

    2002-01-01

    We have studied the electronic structure of the skutterudite compounds CoSb sub 3 and Co(Sb sub 0 sub . sub 9 sub 6 Te sub 0 sub . sub 0 sub 4) sub 3 by photoemission spectroscopy. Valence-band spectra revealed that a significant amount Sb 5p states are present near the Fermi level and are hybridized with Co 3d states just below it. The spectra are well reproduced by the band-structure calculation, suggesting that the effect of electron correlations is not important. When Te is substituted for Sb and n-type carriers are doped into CoSb sub 3 , the spectra are shifted to higher binding energies as described by the rigid-band model. From this shift and the free-electron model for the conduction and valence bands, we have estimated the band gap of CoSb sub 3 to be 0.03-0.04 eV, consistent with transport measurements. Photoemission spectra of RhSb sub 3 have also been measured and revealed expected similarities to and differences from those of CoSb sub 3. Unusual temperature dependence has been observed for the s...

  5. Introductory photoemission theory

    International Nuclear Information System (INIS)

    Arai, Hiroko; Fujikawa, Takashi

    2010-01-01

    An introductory review is presented on the basis of many-body scattering theory. Some fundamental aspects of photoemission theory are discussed in detail. A few applications are also discussed; photoelectron diffraction, depth distribution function and multi-atom resonant photoemission are also discussed briefly. (author)

  6. Angle-resolved photoemission studies of the superconducting gap symmetry in Fe-based superconductors

    Directory of Open Access Journals (Sweden)

    Y.-B. Huang

    2012-12-01

    Full Text Available The superconducting gap is the fundamental parameter that characterizes the superconducting state, and its symmetry is a direct consequence of the mechanism responsible for Cooper pairing. Here we discuss about angle-resolved photoemission spectroscopy measurements of the superconducting gap in the Fe-based high-temperature superconductors. We show that the superconducting gap is Fermi surface dependent and nodeless with small anisotropy, or more precisely, a function of the momentum location in the Brillouin zone. We show that while this observation seems inconsistent with weak coupling approaches for superconductivity in these materials, it is well supported by strong coupling models and global superconducting gaps. We also suggest that a smaller lifetime of the superconducting Cooper pairs induced by the momentum dependent interband scattering inherent to these materials could affect the residual density of states at low energies, which is critical for a proper evaluation of the superconducting gap.

  7. Study of adsorption states for lubricant molecule using hard X-ray photoemission spectroscopy

    International Nuclear Information System (INIS)

    Ikenaga, E.; Kobata, M.; Kim, J.J.; Wakabayashi, A.; Nishino, Y.; Tamasaku, K.; Sakane, Y.; Ishikawa, T.; Komiya, S.; Kobayashi, K.

    2007-01-01

    The adsorption states for lubricant molecules have been investigated using hard X-ray (hν = 7.95 keV) photoemission spectroscopy (HX-PES). This method has the advantage for the organic molecules to be able to measure damage few. Being aware of the fact that P atoms exist only in cyclotriphosphazene base, we measured the take-off angle dependence of the P1s spectra. Each spectrum consists from two peaks, that is, substrate NiP peak and cyclotriphosphazene P peak. The cyclotriphosphazene P peak rapidly disappears with increasing take-off angle. We have also measured C1s spectra. Combining these experimental results, we have found that the adsorption state of cyclotriphosphazene end group is undergoing

  8. Photoemission study of S adsorption on GaAs (0 0 1)

    International Nuclear Information System (INIS)

    Strasser, T; Kipp, L; Skibowski, M; Schattke, W

    2005-01-01

    Angle-resolved photoemission spectra have been calculated with the one-step model for S/GaAs(0 0 1) and compared with experimental distributions. The data are analysed in terms of the ideal 1 x 1 and, furthermore, of the reconstructed 2 x 6 surface which is assumed to be closest to the experimentally realized structure. Emissions are characterized by electronic structure terms such as energy bands and orbital composition, though partly also by geometric properties. In particular, the determination of the second layer as consisting of Ga atoms has been achieved because of the distinct differences in the theoretical spectra with S-Ga and those with S-As bonds

  9. An Angle Resolved Photoemission Study of a Mott Insulator and Its Evolution to a High Temperature Superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Ronning, Filip

    2002-03-19

    One of the most remarkable facts about the high temperature superconductors is their close proximity to an antiferromagnetically ordered Mott insulating phase. This fact suggests that to understand superconductivity in the cuprates we must first understand the insulating regime. Due to material properties the technique of angle resolved photoemission is ideally suited to study the electronic structure in the cuprates. Thus, a natural starting place to unlocking the secrets of high Tc would appears to be with a photoemission investigation of insulating cuprates. This dissertation presents the results of precisely such a study. In particular, we have focused on the compound Ca{sub 2-x}Na{sub x}CuO{sub 2}Cl{sub 2}. With increasing Na content this system goes from an antiferromagnetic Mott insulator with a Neel transition of 256K to a superconductor with an optimal transition temperature of 28K. At half filling we have found an asymmetry in the integrated spectral weight, which can be related to the occupation probability, n(k). This has led us to identify a d-wave-like dispersion in the insulator, which in turn implies that the high energy pseudogap as seen by photoemission is a remnant property of the insulator. These results are robust features of the insulator which we found in many different compounds and experimental conditions. By adding Na we were able to study the evolution of the electronic structure across the insulator to metal transition. We found that the chemical potential shifts as holes are doped into the system. This picture is in sharp contrast to the case of La{sub 2-x}Sr{sub x}CuO{sub 4} where the chemical potential remains fixed and states are created inside the gap. Furthermore, the low energy excitations (ie the Fermi surface) in metallic Ca{sub 1.9}Na{sub 0.1}CuO{sub 2}Cl{sub 2} is most well described as a Fermi arc, although the high binding energy features reveal the presence of shadow bands. Thus, the results in this dissertation provide a

  10. A study of Al/Si interface by photoemission, Auger electron yield and Auger electron spectroscopies

    International Nuclear Information System (INIS)

    Kobayashi, K.L.I.; Barth, J.; Gerken, F.; Kunz, C.; Deutsches Elektronen-Synchrotron

    1980-06-01

    Photoemission, Auger electron yield and Auger electron spectra were observed for Al/Si(111) interfaces with various Al coverage prepared by successive deposition using a molecular beam source. The Al 3p derived states are introduced at around the top of the valence band by the Al coverage of less than one monolayer. The Al surface layer behaves as a 'metal' and the Fermi level is stabilized in the Al 3p derived states at about 0.3 eV above the top of the valence band of Si. The Schottky barrier height in this stage is about 0.8 eV and further increase in Al coverage does not change the barrier height. A covalent bonding model of the Al/Si interface based on the experimental results is proposed. The present result favors the on-top geometry of Al atoms on Si(111) surface among the geometries used in the pseudopotential calculation by Zhang and Schlueter. (orig.)

  11. Photoemission microscopy study of picosecond magnetodynamics in spin-valve-type thin film elements

    International Nuclear Information System (INIS)

    Schneider, C.M.; Kaiser, A.; Wiemann, C.; Tieg, C.; Cramm, S.

    2010-01-01

    Exploring ultimate time scales of magnetic switching processes is an important issue in spin electronics. In spin valves or magnetic tunnelling junctions magnetic anisotropies and coupling phenomena alter the magnetodynamic response of the entire system. Understanding the role of these interactions is a key to the design of optimized devices. We have employed time-resolved X-ray photoemission microscopy to address the magnetodynamics in spin-valve-type model systems in the ns- and ps-regime. In Co/Cr/Fe(0 0 1) single crystal elements we find a strong influence of the magnetocrystalline anisotropy, which tends to suppress rotation processes. In addition, we observe a dynamic 'decoupling' of the layers. In low-anisotropy FeNi/Cr/FeCo trilayers, the interlayer coupling character determines the dynamic response. Particularly, rotational processes in the FeNi and FeCo layers are temporarily shifted to each other, which can be related to different coercivities of the individual layers. By contrast, the domain wall motion in both layers closely agrees, caused by an enhanced coupling due to the domain wall stray fields. Our examples demonstrate that the detailed magnetodynamics in coupled magnetic layers is quite complex and depends strongly on the timescale under consideration.

  12. A soft x-ray photoemission study of the chemisorption and reaction of diethylsilane on Si(100)

    International Nuclear Information System (INIS)

    Lapiano-Smith, D.A.; Himpsel, F.J.

    1993-06-01

    Soft x-ray synchrotron radiation was utilized as the excitation source in a high-resolution photoemission experiment on chemisorption and subsequent reaction of diethylsilane on the Si(100) surface. We have found that diethylsilane chemisorbs dissociatively to form Si-CH 2 CH 3 surface species on Si(100) following a room temperature exposure. These species are identified by two very sharp peaks observed in the valence band spectra positioned at 17.9 and 14.3 eV binding energy. In addition, C 1s core level spectra, measured following exposures of Si(100) substrates as a function of surface temperature, show that carbon, in some form, exists on the Si surface following exposures at every temperature from room temperature to about 600C. While only -CH 2 CH 3 , ethyl groups are observed on the surface at room temperature, these species appear to partially dehydrogenate at 300C, producing a mixture of -CH 2 CH 3 groups and other intermediate carbonaceous species. At a growth temperature of about 400C the intermixing of elemental carbon with Si begins. At higher temperatures, we observe the continued degradation of diethylsilane to produce a Si + C alloy on the surface at 600C. Results indicate that diethylsilane has potential as a molecular precursor for SiC formation by chemical vapor deposition techniques

  13. Developments in inverse photoemission spectroscopy

    International Nuclear Information System (INIS)

    Sheils, W.; Leckey, R.C.G.; Riley, J.D.

    1996-01-01

    In the 1950's and 1960's, Photoemission Spectroscopy (PES) established itself as the major technique for the study of the occupied electronic energy levels of solids. During this period the field divided into two branches: X-ray Photoemission Spectroscopy (XPS) for photon energies greater than ∼l000eV, and Ultra-violet Photoemission Spectroscopy (UPS) for photon energies below ∼100eV. By the 1970's XPS and UPS had become mature techniques. Like XPS, BIS (at x-ray energies) does not have the momentum-resolving ability of UPS that has contributed much to the understanding of the occupied band structures of solids. BIS moved into a new energy regime in 1977 when Dose employed a Geiger-Mueller tube to obtain density of unoccupied states data from a tantalum sample at a photon energy of ∼9.7eV. At similar energies, the technique has since become known as Inverse Photoemission Spectroscopy (IPS), in acknowledgment of its complementary relationship to UPS and to distinguish it from the higher energy BIS. Drawing on decades of UPS expertise, IPS has quickly moved into areas of interest where UPS has been applied; metals, semiconductors, layer compounds, adsorbates, ferromagnets, and superconductors. At La Trobe University an IPS facility has been constructed. This presentation reports on developments in the experimental and analytical techniques of IPS that have been made there. The results of a study of the unoccupied bulk and surface bands of GaAs are presented

  14. Angle resolved photoemission study of Fermi surfaces and single-particle excitations of quasi-low dimensional materials

    Science.gov (United States)

    Gweon, Gey-Hong

    Using angle resolved photoemission spectroscopy (ARPES) as the main experimental tool and the single particle Green's function as the main theoretical tool, materials of various degrees of low dimensionality and different ground states are studied. The underlying theme of this thesis is that of one dimensional physics, which includes charge density waves (CDW's) and the Luttinger liquid (LL). The LL is the prime example of a lattice non-Fermi liquid (non-FL) and CDW fluctuations also give non-FL behaviors. Non-FL physics is an emerging paradigm of condensed matter physics. It is thought by some researchers that one dimensional LL behavior is a key element in solving the high temperature superconductivity problem. TiTe2 is a quasi-2 dimensional (quasi-2D) Fermi liquid (FL) material very well suited for ARPES lineshape studies. I report ARPES spectra at 300 K which show an unusual behavior of a peak moving through the Fermi energy (EF). I also report a good fit of the ARPES spectra at 25 K obtained by using a causal Green's function proposed by K. Matho. SmTe3 is a quasi-2D CDW material. The near EF ARPES spectra and intensity map reveal rich details of an anisotropic gap and imperfectly nested Fermi surface (FS) for a high temperature CDW. A simple model of imperfect nesting can be constructed from these data and predicts a CDW wavevector in very good agreement with the value known from electron diffraction. NaMo6O17 and KMo 6O17 are also quasi-2D CDW materials. The "hidden nesting" or "hidden 1 dimensionality" picture for the CDW is confirmed very well by our direct image of the FS. K0.3MoO3, the so-called "blue bronze," is a quasi-1 dimensional (quasi-1D) CDW material. Even in its metallic phase above the CDW transition temperature, its photoemission spectra show an anomalously weak intensity at EF and no clear metallic Fermi edge. I compare predictions of an LL model and a CDW fluctuation model regarding these aspects, and find that the LL scenario explains them

  15. Spin-polarized photoemission

    International Nuclear Information System (INIS)

    Johnson, Peter D.

    1997-01-01

    Spin-polarized photoemission has developed into a versatile tool for the study of surface and thin film magnetism. In this review, we examine the methodology of the technique and its application to a number of different problems, including both valence band and core level studies. After a detailed review of spin-polarization measurement techniques and the related experimental requirements we consider in detail studies of the bulk properties both above and below the Curie temperature. This section also includes a discussion of observations relating to unique metastable phases obtained via epitaxial growth. The application of the technique to the study of surfaces, both clean and adsorbate covered, is reviewed. The report then examines, in detail, studies of the spin-polarized electronic structure of thin films and the related interfacial magnetism. Finally, observations of spin-polarized quantum well states in non-magnetic thin films are discussed with particular reference to their mediation of the oscillatory exchange coupling in related magnetic multilayers. (author)

  16. X-ray photoemission spectroscopy (XPS) and extended x-ray absorption fine structure (EXAFS) studies of silicate based glasses

    International Nuclear Information System (INIS)

    Karim, D.; Lam, D.J.

    1979-01-01

    The application of the x-ray photoemission spectroscopy (XPS) technique to study the electronic structure and bonding of heavy metal oxides in alkali- and alkali-earth-silicate glasses had been demonstrated. The bonding characteristics of the iron oxide and uranium oxide in sodium silicate glasses were deduced from the changes in the oxygen 1s levels and the heavy metal core levels. It is reasonable to expect that the effect of leaching on the heavy metal ions can be monitored using the appropriate core levels of these ions. To study the effect of leaching on the glass forming network, the valence band structure of the bridging and nonbridging oxygens in sodium silicate glasses were investigated. The measurement of extended x-ray absorption fine-structure (EXAFS) is a relatively new analytical technique for obtaining short range (<5 A) structural information around atoms of a selected species in both solid and fluid systems. Experiments have recently begun to establish the feasibility of using EXAFS to study the bonding of actinides in silicate glasses. Because of the ability of EXAFS to yield specific structural data even in complex multicomponent systems, it could prove to be an invaluable tool in understanding glass structure

  17. The development of photoemission spectroscopy and its application to the study of semiconductor interfaces Observations on the interplay between basic and applied research (Welch Memorial Lecture)

    Science.gov (United States)

    Spicer, W. E.

    1985-01-01

    A sketch is given of the development of photoemission electron spectroscopy (PES) with emphasis on the author's own experience. Emphasis is placed: (1) on the period between 1958-1970; (2) on the various developments which were required for PES to emerge; and (3) on the strong interactions between applied/fundamental and knowledge/empirically based research. A more detailed discussion is given of the recent (1975-present) application of PES to study the interfaces of III-V semiconductors.

  18. Oxygen stoichiometry of LaTiO{sub 3} thin films studied by in-situ photoemission

    Energy Technology Data Exchange (ETDEWEB)

    Scheiderer, Philipp; Goessmann, Alex; Sing, Michael; Claessen, Ralph [Universitaet Wuerzburg, Physikalisches Institut and Roentgen Center for Complex Material Systems (RCCM), 97074 Wuerzburg (Germany)

    2015-07-01

    As in the famous oxide heterostructure LaAlO{sub 3}/SrTiO{sub 3} (LAO/STO) a two dimensional electron system is found at the interface between the strongly correlated Mott insulator LaTi{sup 3+}O{sub 3} and the band insulator STO. The stabilization of LaTi{sup 3+}O{sub 3} requires strong reducing growth conditions since the thermodynamically stable bulk phase is the oxygen rich La{sub 2}Ti{sup 4+}{sub 2}O{sub 7}. Therefore, we have systematically studied the impact of the oxygen background atmosphere on LaTi{sup 3+}O{sub 3} thin film growth by PLD. Reflection high-energy diffraction intensity oscillations of the specular spot indicate a layer by layer growth mode for thin films, which merges into the formation of islands for thicker films. In-situ photoemission measurements enables us to determine the oxidation state of Ti indicating excess or lack of oxygen present in the prepared samples. Our experiments show that even for films grown in vacuum, strong oxygen excess is present probably due to oxygen out-diffusion from the STO substrate. We find that an LAO buffer layer serves as an effective barrier for this process. The spectral weight of the lower Hubbard band, being a characteristic feature for the Mott insulating phase, is found to scale inversely with the amount of excess oxygen.

  19. Charge-density-wave partial gap opening in quasi-2D KMo 6O 17 purple bronze studied by angle resolved photoemission spectroscopy

    Science.gov (United States)

    Valbuena, M. A.; Avila, J.; Pantin, V.; Drouard, S.; Guyot, H.; Asensio, M. C.

    2006-05-01

    Low dimensional (LD) metallic oxides have been a subject of continuous interest in the last two decades, mainly due to the electronic instabilities that they present at low temperatures. In particular, charge density waves (CDW) instabilities associated with a strong electron-phonon interaction have been found in Molybdenum metallic oxides such as KMo 6O 17 purple bronze. We report an angle resolved photoemission (ARPES) study from room temperature (RT) to T ˜40 K well below the Peierls transition temperature for this material, with CDW transition temperature TCDW ˜120 K. We have focused on photoemission spectra along ΓM high symmetry direction as well as photoemission measurements were taken as a function of temperature at one representative kF point in the Brillouin zone in order to look for the characteristic gap opening after the phase transition. We found out a pseudogap opening and a decrease in the density of states near the Fermi energy, EF, consistent with the partial removal of the nested portions of the Fermi surface (FS) at temperature below the CDW transition. In order to elucidate possible Fermi liquid (FL) or non-Fermi liquid (NFL) behaviour we have compared the ARPES data with that one reported on quasi-1D K 0.3MoO 3 blue bronze.

  20. Charge-density-wave partial gap opening in quasi-2D KMo6O17 purple bronze studied by angle resolved photoemission spectroscopy

    International Nuclear Information System (INIS)

    Valbuena, M.A.; Avila, J.; Pantin, V.; Drouard, S.; Guyot, H.; Asensio, M.C.

    2006-01-01

    Low dimensional (LD) metallic oxides have been a subject of continuous interest in the last two decades, mainly due to the electronic instabilities that they present at low temperatures. In particular, charge density waves (CDW) instabilities associated with a strong electron-phonon interaction have been found in Molybdenum metallic oxides such as KMo 6 O 17 purple bronze. We report an angle resolved photoemission (ARPES) study from room temperature (RT) to T ∼40 K well below the Peierls transition temperature for this material, with CDW transition temperature T CDW ∼120 K. We have focused on photoemission spectra along ΓM high symmetry direction as well as photoemission measurements were taken as a function of temperature at one representative k F point in the Brillouin zone in order to look for the characteristic gap opening after the phase transition. We found out a pseudogap opening and a decrease in the density of states near the Fermi energy, E F , consistent with the partial removal of the nested portions of the Fermi surface (FS) at temperature below the CDW transition. In order to elucidate possible Fermi liquid (FL) or non-Fermi liquid (NFL) behaviour we have compared the ARPES data with that one reported on quasi-1D K 0.3 MoO 3 blue bronze

  1. Charge-density-wave partial gap opening in quasi-2D KMo{sub 6}O{sub 17} purple bronze studied by angle resolved photoemission spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Valbuena, M.A. [LURE, Centre Universitaire Paris-Sud, Bat. 209D, B.P. 34, 91898 Orsay Cedex (France); Avila, J. [Instituto de Ciencia de Materiales de Madrid, ICMM - CSIC, 28049 Madrid (Spain); Synchrotron SOLEIL, L' Orme des Merisiers, Saint-Aubin - B.P. 48, 91192 GIF-SUR-YVETTE Cedex (France); Pantin, V. [LURE, Centre Universitaire Paris-Sud, Bat. 209D, B.P. 34, 91898 Orsay Cedex (France); Drouard, S. [LEPES-CENES, B.P. 166x, 38042 Grenoble, Cedex 9 (France); Guyot, H. [LEPES-CENES, B.P. 166x, 38042 Grenoble, Cedex 9 (France); Asensio, M.C. [Instituto de Ciencia de Materiales de Madrid, ICMM - CSIC, 28049 Madrid (Spain) and Synchrotron SOLEIL, L' Orme des Merisiers, Saint-Aubin - B.P. 48, 91192 GIF-SUR-YVETTE Cedex (France)]. E-mail: asensio@synchrotron-soleil.fr

    2006-05-30

    Low dimensional (LD) metallic oxides have been a subject of continuous interest in the last two decades, mainly due to the electronic instabilities that they present at low temperatures. In particular, charge density waves (CDW) instabilities associated with a strong electron-phonon interaction have been found in Molybdenum metallic oxides such as KMo{sub 6}O{sub 17} purple bronze. We report an angle resolved photoemission (ARPES) study from room temperature (RT) to T {approx}40 K well below the Peierls transition temperature for this material, with CDW transition temperature T {sub CDW} {approx}120 K. We have focused on photoemission spectra along {gamma}M high symmetry direction as well as photoemission measurements were taken as a function of temperature at one representative k {sub F} point in the Brillouin zone in order to look for the characteristic gap opening after the phase transition. We found out a pseudogap opening and a decrease in the density of states near the Fermi energy, E {sub F}, consistent with the partial removal of the nested portions of the Fermi surface (FS) at temperature below the CDW transition. In order to elucidate possible Fermi liquid (FL) or non-Fermi liquid (NFL) behaviour we have compared the ARPES data with that one reported on quasi-1D K{sub 0.3}MoO{sub 3} blue bronze.

  2. Local Electronic and Magnetic Structure of Ni below and above TC: A Spin-Resolved Circularly Polarized Resonant Photoemission Study

    NARCIS (Netherlands)

    Sinkovic, B.; Tjeng, L.H.; Brookes, N.B.; Goedkoop, J.B.; Hesper, R.; Pellegrin, E.; Groot, F.M.F. de; Altieri, S.; Hulbert, S.L.; Shekel, E.; Sawatzky, G.A.

    1997-01-01

    We report the measurement of the local Ni 3d spin polarization, not only below but also above the Curie temperature (TC), using the newly developed spin-resolved circularly polarized 2p (L3) resonant photoemission technique. The experiment identifies the presence of 3d8 singlets at high energies

  3. Fourier Transform Photoemission Spectroscopy

    NARCIS (Netherlands)

    Meinders, M.B.J.; Drabe, K.E.; Jonkman, H.T.; Sawatzky, G.A.

    1996-01-01

    It is shown that photoemission spectra can be obtained by exciting the electrons with two phase-correlated wave trains. The phase-correlated wave trains are obtained by sending broad-band ultra-violet light, coming from a deuterium lamp, through a Michelson interferometer. It is possible to

  4. Fourier transform photoemission spectroscopy

    NARCIS (Netherlands)

    Meinders, M.B J; Drabe, K.E.; Jonkman, H.T.; Sawatzky, G.A

    It is shown that photoemission spectra can be obtained by exciting the electrons with two phase-correlated wave trains. The phase-correlated wave trains are obtained by sending broad-band ultra-violet light, coming from a deuterium lamp, through a Michelson interferometer. It is possible to

  5. Internal photoemission study on charge trapping behavior in rapid thermal oxides on strained-Si/SiGe heterolayers

    International Nuclear Information System (INIS)

    Bera, M.K.; Mahata, C.; Bhattacharya, S.; Chakraborty, A.K.; Armstrong, B.M.; Gamble, H.S.; Maiti, C.K.

    2008-01-01

    A comparative study on the nature of defects and their relationship to charge trapping with enhanced photosensitivity has been investigated through magnetic resonance and internal photoemission (IPE) experiments for rapid thermal grown oxides (RTO) on strained-Si/Si 0.8 Ge 0.2 and on co-processed bulk-Si (1 0 0) substrates. Both the band and defect-related electronic states were characterized through EPR, IPE, C-V and I-V measurements under UV-illumination. Surface chemical characterization of as-grown ultrathin oxides (5-7 nm) has been performed using high-resolution XPS. Enhancement in Ge-segregation with increasing oxidation temperature is reported. Comparative studies on interface properties and leakage current behavior of rapid thermal oxides have also been studied through fabricating metal-oxide-semiconductor capacitor structures. A degraded electrical property with increasing oxidation temperature is reported. Constant voltage stressing (CVS) in the range of 5.5-7 V was used to study the breakdown characteristics of different samples. We observe a distinguishably different time-to-breakdown (t bd ) phenomenon for bulk-Si and strained-Si/SiGe samples. Whereas the oxide on bulk-Si shows a typical breakdown behavior, the RTO grown oxide on strained-Si/SiGe samples showed a quasi-or soft-breakdown with lower t bd value. It may be pointed out that quasi-breakdown may be a stronger reliability limiting factor for strained-Si/SiGe devices in the oxide thickness range studied

  6. Electronic properties of metal-organic and organic-organic interfaces studied by photoemission and photoabsorption spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Molodtsova, Olga

    2006-07-01

    In this work systematic studies of the organic semiconductor CuPc have been presented. In general the investigation can be devided in three parts. In the first one we have studied the electronic structure of clean CuPc thin film. The next two parts are devoted to organic-organic and metal-organic interface formation, where one of the interface components is CuPc thin film. The main results of this thesis are: - The electronic structure of the pristine organic semiconductor CuPc has been obtained by a combination of conventional and resonant photoemission, near-edge X-ray absorption, as well as by theoretical ab initio quantum-chemical calculations. The contributions of different atomic species as well as sites of the CuPc molecule to the electronic DOS has been established. A combined experimental and theoretical study of the unoccupied electronic density of states of CuPc was presented. - The electronic properties of the organic heterointerfaces between fullerite and pristine copper phthalocyanine were studied. Both interfaces, CuPc/C{sub 60} and C{sub 60}/CuPc, were found to be non-reactive with pronounced shifts of the vacuum level pointing to the formation of an interfacial dipole mainly at the CuPc side of the heterojunctions. The dipole values are close to the difference of the work functions of the two materials. Important interface parameters and hole-injection barriers were obtained. The sequence of deposition does not influence the electronic properties of the interfaces. - CuPc doped with potassium was studied by means of photoemission and photoabsorption spectroscopy. A detailed analysis of the core-level PE spectra allows one to propose possible lattice sites, which harbor the potassium ions. The films prepared in this thesis showed no finite electronic density of states at the Fermi level. - Two stages of the In/CuPc interface formation have been distinguished. The low-coverage stage is characterized by a strong diffusion of the In atoms into the

  7. Photoemission study of the Poly(3-hexylthiophene)/TiO2 interface and the role of 4-Mercaptopyridine

    Energy Technology Data Exchange (ETDEWEB)

    Calloni, A., E-mail: alberto1.calloni@mail.polimi.it [CNISM and Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo Da Vinci 32, 20133 Milano (Italy); Berti, G.; Ferrari, A.; Brambilla, A.; Bussetti, G. [CNISM and Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo Da Vinci 32, 20133 Milano (Italy); Canesi, E.V.; Petrozza, A. [Center for Nano Science and Technology @ Polimi, Istituto Italiano di Tecnologia, via Pascoli 70/3, 20133 Milano (Italy); Duò, L. [CNISM and Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo Da Vinci 32, 20133 Milano (Italy)

    2014-06-02

    We report on a combined X-ray and UV photoemission spectroscopy study (XPS, UPS) of the interface between Poly(3-hexylthiophene) (P3HT) and mesoporous titanium dioxide (TiO{sub 2}), a key element in the development of hybrid solar cells. We employed the elemental specificity of XPS to directly probe, on the complete P3HT/TiO{sub 2} heterostructure, the changes in the electronic levels alignment at the interface upon the addition of 4-Mercaptopyridine (4-MPy) molecules. We estimate an upper limit of 50 meV to the contribution of 4-MPy to the P3HT/TiO{sub 2} interfacial dipole. In addition, UPS was used to provide a quantitative estimate of the relevant parameters controlling the transfer of charge through the hybrid interface, such as the binding energy of the TiO{sub 2} valence and conduction bands and of the P3HT highest occupied/lowest unoccupied molecular orbitals. In both cases, we confirm that the alignment of P3HT energy levels to those of the substrate is not influenced by the position of the Fermi level inside the TiO{sub 2} band gap. - Highlights: • We studied the electronic structure of the Poly(3-hexylthiophene)/TiO{sub 2} interface. • 4-mercaptopyridine (4-MPy) molecules were used as interface modifiers. • The contribution of 4-MPy to the interfacial dipole is limited to 50 meV. • No pinning of Poly(3-hexylthiophene) energy levels to the Fermi level is observed.

  8. Combined Photoemission Spectroscopy and Electrochemical Study of a Mixture of (Oxy)carbides as Potential Innovative Supports and Electrocatalysts.

    Science.gov (United States)

    Calvillo, Laura; Valero-Vidal, Carlos; Agnoli, Stefano; Sezen, Hikmet; Rüdiger, Celine; Kunze-Liebhäuser, Julia; Granozzi, Gaetano

    2016-08-03

    Active and stable non-noble metal materials, able to substitute Pt as catalyst or to reduce the Pt amount, are vitally important for the extended commercialization of energy conversion technologies, such as fuel cells and electrolyzers. Here, we report a fundamental study of nonstoichiometric tungsten carbide (WxC) and its interaction with titanium oxycarbide (TiOxCy) under electrochemical working conditions. In particular, the electrochemical activity and stability of the WxC/TiOxCy system toward the ethanol electrooxidation reaction (EOR) and hydrogen evolution reaction (HER) are investigated. The chemical changes caused by the applied potential are established by combining photoemission spectroscopy and electrochemistry. WxC is not active toward the ethanol electrooxidation reaction at room temperature but it is highly stable under these conditions thanks to the formation of a passive thin film on the surface, consisting mainly of WO2 and W2O5, which prevents the full oxidation of WxC. In addition, WxC is able to adsorb ethanol, forming ethoxy groups on the surface, which constitutes the first step for the ethanol oxidation. The interaction between WxC and TiOxCy plays an important role in the electrochemical stability of WxC since specific orientations of the substrate are able to stabilize WxC and prevent its corrosion. The beneficial interaction with the substrate and the specific surface chemistry makes tungsten carbide a good electrocatalyst support or cocatalyst for direct ethanol fuel cells. However, WxC is active toward the HER and chemically stable under hydrogen reduction conditions, since no changes in the chemical composition or dissolution of the film are observed. This makes tungsten carbide a good candidate as electrocatalyst support or cocatalyst for the electrochemical production of hydrogen.

  9. Band structure and Fermi surface of UPd2Al3 studied by angle-resolved photoemission spectroscopy

    International Nuclear Information System (INIS)

    Fujimori, Shin-ichi; Saitoh, Yuji; Okane, Tetsuo; Yamagami, Hiroshi; Fujimori, Atsushi; Haga, Yoshinori; Yamamoto, Etsuji; Onuki, Yoshichika

    2007-01-01

    We have observed the band structure and Fermi surfaces of the heavy Fermion superconductor UPd 2 Al 3 by angle-resolved photoemission experiments in the soft X-ray region. We observed renormalized quasi-particle bands in the vicinity of the Fermi level and strongly dispersive bands on the higher binding energy side. Our observation suggests that the structure previously assigned to contributions from localized states in the U 5f spectrum has strong energy dispersions

  10. Studies of Dirac and Weyl fermions by angle resolved photoemission spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Lunan [Iowa State Univ., Ames, IA (United States)

    2016-01-01

    This dissertation consists of three parts. First, we study magnetic domains in Nd2Fe14B single crystals using high resolution magnetic force microscopy (MFM). In addition to the elongated, wavy nano-domains reported by a previous MFM study, we found that the micrometer size, star-shaped fractal pattern is constructed of an elongated network of nano-domains about 20 nm in width, with resolution-limited domain walls thinner than 2 nm. Second, we studied extra Dirac cones of multilayer graphene on SiC surface by ARPES and SPA-LEED. We discovered extra Dirac cones on Fermi surface due to SiC 6 x 6 and graphene 6√ 3 6√ 3 coincidence lattice on both single-layer and three-layer graphene sheets. We interpreted the position and intensity of the Dirac cone replicas, based on the scattering vectors from LEED patterns. We found the positions of replica Dirac cones are determined mostly by the 6 6 SiC superlattice even graphene layers grown thicker. Finally, we studied the electronic structure of MoTe2 by ARPES and experimentally con rmed the prediction of type II Weyl state in this material. By combining the result of Density Functional Theory calculations and Berry curvature calculations with out experimental data, we identi ed Fermi arcs, track states and Weyl points, all features predicted to exist in a type II Weyl semimetal. This material is an excellent playground for studies of exotic Fermions.

  11. Studies on effect of europium concentration on the photoemission of laser ablated Y2O3:Eu based nano-phosphors

    International Nuclear Information System (INIS)

    Nissamudeen, K.M.; Krishnan, Renju R.; Rajan, Geo; Gopchandran, K.G.

    2007-01-01

    Full text: Phosphors are essential materials in display applications. Oxide-based phosphors are likely to emerge as the potential choice for the FED red phosphor. Among those oxide-based phosphors, there has been significant research interest in the development of Y 2 O 3 :Eu thin films as one of the most promising oxide based red phosphor systems. Yttrium oxide mixed with europium exhibit strong UV and cathode-ray-excited luminescence that are useful in lamp and display applications. Dielectric Y 2 O 3 film has recently attracted much attention for its potential application as an electric insulation layer in electroluminescent devices and high-density dynamic random access memory gate dielectrics because of its high band gap (5.8 eV) and large dielectric constant (14 to 18). Another important application of Y 2 O 3 has been in luminescent displays as a host material for rare-earth ions, specifically europium, in order to get emission of red light. In the present study thin films were deposited under a vacuum of 10 -6 mbar on fused amorphous quartz substrates using a Q-switched Nd: YAG laser, 532 nm, pulse width 9 n sec, and repetition frequency of 10 Hz, with sintered Y 2 O 3 pellets having different europium concentration as target material. Attempts were made to understand the effect of europium concentration and annealing process on the photoemission properties of the films. A europium concentration of 8 wt% and an annealing temperature of 1173 K were found to be optimum conditions for maximum photoemission. The dependence of structure and morphology of the films on the photoemission intensity are described with XRD patterns and images obtained from AFM and SEM studies

  12. Photoemission study on electrical dipole at SiO_2/Si and HfO_2/SiO_2 interfaces

    International Nuclear Information System (INIS)

    Fujimura, Nobuyuki; Ohta, Akio; Ikeda, Mitsuhisa; Makihara, Katsunori; Miyazaki, Seiichi

    2017-01-01

    Electrical dipole at SiO_2/Si and HfO_2/SiO_2 interfaces have been investigated by X-ray photoelectron spectroscopy (XPS) under monochromatized Al Kα radiation. From the analysis of the cut-off energy for secondary photoelectrons measured at each thinning step of a dielectric layer by wet-chemical etching, an abrupt potential change caused by electrical dipole at SiO_2/Si and HfO_2/SiO_2 interfaces has been clearly detected. Al-gate MOS capacitors with thermally-grown SiO_2 and a HfO_2/SiO_2 dielectric stack were fabricated to evaluate the Al work function from the flat band voltage shift of capacitance-voltage (C-V) characteristics. Comparing the results of XPS and C-V measurements, we have verified that electrical dipole formed at the interface can be directly measured by photoemission measurements. (author)

  13. Synchronization and Characterization of an Ultra-Short Laser for Photoemission and Electron-Beam Diagnostics Studies at a Radio Frequency Photoinjector

    Energy Technology Data Exchange (ETDEWEB)

    Maxwell, Timothy; Ruan, Jinhao; Piot, Philippe; Lumpkin, Alex

    2012-03-01

    A commercially-available titanium-sapphire laser system has recently been installed at the Fermilab A0 photoinjector laboratory in support of photoemission and electron beam diagnostics studies. The laser system is synchronized to both the 1.3-GHz master oscillator and a 1-Hz signal use to trigger the radiofrequency system and instrumentation acquisition. The synchronization scheme and performance are detailed. Long-term temporal and intensity drifts are identified and actively suppressed to within 1 ps and 1.5%, respectively. Measurement and optimization of the laser's temporal profile are accomplished using frequency-resolved optical gating.

  14. Unusually large chemical potential shift in a degenerate semiconductor: Angle-resolved photoemission study of SnSe and Na-doped SnSe

    Science.gov (United States)

    Maeda, M.; Yamamoto, K.; Mizokawa, T.; Saini, N. L.; Arita, M.; Namatame, H.; Taniguchi, M.; Tan, G.; Zhao, L. D.; Kanatzidis, M. G.

    2018-03-01

    We have studied the electronic structure of SnSe and Na-doped SnSe by means of angle-resolved photoemission spectroscopy. The valence-band top reaches the Fermi level by the Na doping, indicating that Na-doped SnSe can be viewed as a degenerate semiconductor. However, in the Na-doped system, the chemical potential shift with temperature is unexpectedly large and is apparently inconsistent with the degenerate semiconductor picture. The large chemical potential shift and anomalous spectral shape are key ingredients for an understanding of the novel metallic state with the large thermoelectric performance in Na-doped SnSe.

  15. Role of photocurrent in low-temperature photoemission studies of Schottky-barrier formation

    International Nuclear Information System (INIS)

    Hecht, M.H.

    1990-01-01

    Photoelectron spectroscopy is frequently used to study band bending in semiconductors due to charge stored in surface or interface states. This paper examines how such experimental results are modified by photovoltages generated within the band-bending region not only by ambient light sources, but by the incident x rays themselves. Recent experiments which have suggested dopant-dependent and reversible temperature-dependent band bending in the initial stages of formation of the metal-GaAs(110) interface are used as an example. It is shown here that the reported dependence derives from a photovoltaic effect

  16. Photoemission and STM, STS study of Cs/p-GaAs(110)

    International Nuclear Information System (INIS)

    Yamada, T.; Fujii, J.; Mizoguchi, T.

    2001-01-01

    Various stage of adsorbed Cs, i.e., one-dimensional (1D) lines, polygons and coherently c(4x4)-ordered polygons, on cleaved p-GaAs(110) are studied by scanning tunneling microscopy (STM) and scanning tunneling spectroscopies (STS) with an interest in relation to the photo-electron emission. It is understood that only the coherently c(4x4)-ordered Cs polygon surface (Cs coverage of 0.6 ML and 0.7 ML) can emit photo-electrons due to a sufficient reduction of the local work function down to 1.3 eV to get a negative electron affinity state

  17. Comparative study of rare earth hexaborides using high resolution angle-resolved photoemission

    Energy Technology Data Exchange (ETDEWEB)

    Ramankutty, S.V., E-mail: s.v.ramankutty@uva.nl [Van der Waals-Zeeman Institute, Institute of Physics (IoP), University of Amsterdam, Science Park 904, 1098 XH Amsterdam (Netherlands); Jong, N. de; Huang, Y.K.; Zwartsenberg, B. [Van der Waals-Zeeman Institute, Institute of Physics (IoP), University of Amsterdam, Science Park 904, 1098 XH Amsterdam (Netherlands); Massee, F. [Laboratory of Atomic and Solid State Physics, Department of Physics, Cornell University, Ithaca, NY 14853 (United States); Bay, T.V. [Van der Waals-Zeeman Institute, Institute of Physics (IoP), University of Amsterdam, Science Park 904, 1098 XH Amsterdam (Netherlands); Golden, M.S., E-mail: m.s.golden@uva.nl [Van der Waals-Zeeman Institute, Institute of Physics (IoP), University of Amsterdam, Science Park 904, 1098 XH Amsterdam (Netherlands); Frantzeskakis, E., E-mail: e.frantzeskakis@uva.nl [Van der Waals-Zeeman Institute, Institute of Physics (IoP), University of Amsterdam, Science Park 904, 1098 XH Amsterdam (Netherlands)

    2016-04-15

    Highlights: • ARPES electronic structure study of rare-earth (RE) hexaborides SmB{sub 6}, CeB{sub 6} and YbB{sub 6}. • Increasing RE valence Yb[II], Sm[II/III], Ce[III] increases d-band occupancy. • YbB{sub 6} and SmB{sub 6} posses 2D states at E{sub F}, whereas the Fermi surface of CeB{sub 6} is 3D. • ARPES, LEED and STM data prove structural relaxation of the SmB{sub 6}(001) surface. - Abstract: Strong electron correlations in rare earth hexaborides can give rise to a variety of interesting phenomena like ferromagnetism, Kondo hybridization, mixed valence, superconductivity and possibly topological characteristics. The theoretical prediction of topological properties in SmB{sub 6} and YbB{sub 6} has rekindled the scientific interest in the rare earth hexaborides, and high-resolution ARPES has been playing a major role in the debate. The electronic band structure of the hexaborides contains the key to understand the origin of the different phenomena observed, and much can be learned by comparing the experimental data from different rare earth hexaborides. We have performed high-resolution ARPES on the (001) surfaces of YbB{sub 6}, CeB{sub 6} and SmB{sub 6}. On the most basic level, the data show that the differences in the valence of the rare earth element are reflected in the experimental electronic band structure primarily as a rigid shift of the energy position of the metal 5d states with respect to the Fermi level. Although the overall shape of the d-derived Fermi surface contours remains the same, we report differences in the dimensionality of these states between the compounds studied. Moreover, the spectroscopic fingerprint of the 4f states also reveals considerable differences that are related to their coherence and the strength of the d–f hybridization. For the SmB{sub 6} case, we use ARPES in combination with STM imaging and electron diffraction to reveal time dependent changes in the structural symmetry of the highly debated SmB{sub 6

  18. General survey of recent development of photoemission spectroscopy

    International Nuclear Information System (INIS)

    Edamoto, Kazuyuki

    1994-01-01

    On the present state of the recent development of photoemission spectroscopy, by limiting the topics to the development of the spectroscopy proper and the development contributing to the progress of surface science, general explanation is made. As to the development that enabled to heighten spectrum resolution, surface core-level shift and the precise measurement of the Fermi surface of surface level are described, showing the example. Also a number of the developments which enabled the utilization of the light source, of which the wavelength is variable, and which was brought about by synchrotron radiation beam, were mentioned. Besides, spin polarized photoelectron spectroscopy, the development of photoelectron microscope and others are outlined. Photoemission spectroscopy is very useful for analyzing the electron condition of solid surfaces. There are two factors in heightening core level spectrum resolution, namely, heightening the resolution of an electron energy analyzer proper and the utilization of synchrotron radiation as a light source. High resolution core-level spectra, angle-resolved photoemission spectroscopy, and as the light source of which the wavelength is variable, resonance photoemission spectroscopy, constant initial state spectroscopy and soft X-ray photoemission spectroscopy, and as the recently developed spectroscopy, spin polarized photoemission spectroscopy, Auger photoelectron coincidence spectroscopy and photoelectron microscope are explained. (K.I.)

  19. Synchrotron-based photoemission study of electronic structure of the Cs/GaN ultrathin interface

    Science.gov (United States)

    Benemanskaya, G. V.; Kukushkin, S. A.; Dementev, P. A.; Lapushkin, M. N.; Timoshnev, S. N.; Smirnov, D. V.

    2018-03-01

    Electronic structure of the Cs/n-GaN nano-interface has been studied in situ via synchrotron-based photoelectron spectroscopy by excitation in the energy range of 70-400 eV. The GaN sample was grown by an original method of epitaxy of low-defect unstressed nanoscaled films on AlGaN/SiC/Si substrate. Changes in the surface state spectra and in the Ga 3d, Cs 4d, Cs 5p, N 1s core level spectra have been revealed under different cesium coverages. The intrinsic surface states for the clean GaN surface at binding energies of ∼5.0 eV and ∼7.0 eV are attenuated during Cs adsorption. Simultaneously three Cs induced surface states are found to arise. Drastic changes in the surface state spectrum were ascertained and shown to be originated from the local interacting Ga dangling bonds and adsorbed Cs atoms initiating the electron redistribution effect with formation of the semiconductor-like Cs/n-GaN interface.

  20. Photoemission study of metallic iron nanoparticles surface aging in biological fluids. Influence on biomolecules adsorption

    International Nuclear Information System (INIS)

    Canivet, L.; Denayer, F.O.; Champion, Y.; Cenedese, P.; Dubot, P.

    2014-01-01

    Iron nanoparticles (nFe) prepared by vaporization and cryogenic condensation process (10–100 nm) has been exposed to Hank's balanced salt solution (HBSS) and the B-Ali cell growth fluids. These media can be used for cellular growth to study nFe penetration through cell membrane and its induced cytotoxicity. Surface chemistry of nFe exposed to such complex fluids has been characterized as the nanoparticles surface can be strongly changed by adsorption or corrosion processes before reaching intracellular medium. Particle size and surface chemistry have been characterized by scanning electron microscopy (SEM) and high-resolution X-ray photoelectron spectroscopy (HR-XPS). Exposition of nFe particles to growth and differentiation media leads to the formation of an oxy-hydroxide layer containing chlorinated species. We found that the passivated Fe 2 O 3 layer of the bare nFe particles is rapidly transformed into a thicker oxy-hydroxide layer that has a greater ability to adsorb molecular ions or ionic biomolecules like proteins or DNA.

  1. Photoemission study of metallic iron nanoparticles surface aging in biological fluids. Influence on biomolecules adsorption

    Energy Technology Data Exchange (ETDEWEB)

    Canivet, L.; Denayer, F.O. [Université de Lille 2, Droit et Santé, 42 rue P. Duez, 59000 Lille (France); Champion, Y.; Cenedese, P. [CNRS-ICMPE, 2 rue H. Dunant, 94320 Thiais (France); Dubot, P., E-mail: pdubot@icmpe.cnrs.fr [CNRS-ICMPE, 2 rue H. Dunant, 94320 Thiais (France)

    2014-07-01

    Iron nanoparticles (nFe) prepared by vaporization and cryogenic condensation process (10–100 nm) has been exposed to Hank's balanced salt solution (HBSS) and the B-Ali cell growth fluids. These media can be used for cellular growth to study nFe penetration through cell membrane and its induced cytotoxicity. Surface chemistry of nFe exposed to such complex fluids has been characterized as the nanoparticles surface can be strongly changed by adsorption or corrosion processes before reaching intracellular medium. Particle size and surface chemistry have been characterized by scanning electron microscopy (SEM) and high-resolution X-ray photoelectron spectroscopy (HR-XPS). Exposition of nFe particles to growth and differentiation media leads to the formation of an oxy-hydroxide layer containing chlorinated species. We found that the passivated Fe{sub 2}O{sub 3} layer of the bare nFe particles is rapidly transformed into a thicker oxy-hydroxide layer that has a greater ability to adsorb molecular ions or ionic biomolecules like proteins or DNA.

  2. Photoemission Spectroscopy Studies of Methylammonium Lead Iodide Perovskite Thin Films and Interfaces

    Science.gov (United States)

    Thibau, Emmanuel S.

    Organometal halide perovskites have recently emerged as promising materials for fundamentally low-cost, high-performance optoelectronics. In this thesis, we utilize thermal co-evaporation of PbI2 and CH3NH 3 I to fabricate thin films of CH3NH3PbI 3. We first investigate the effect of stoichiometry on some of its structural, optical and electronic properties. Then, we study the energy level alignment of CH3NH3PbI3 with 6 organic semiconductors, revealing good agreement between the data and the theory of vacuum level alignment. Finally, the interface formed between CH3NH 3PbI3 and MoO3 is examined. The findings suggest migration of iodide species into the oxide layer, resulting in deterioration of its chemical and electronic properties. Insertion of an organic interlayer is shown to mitigate these undesirable effects. The results of this work could be of use in device engineering, where knowledge of such interfacial phenomena is of utmost importance in achieving optimized device structures.

  3. Electronic structure of the Ga1-xCrxN studied by high-energy photoemission spectroscopy

    International Nuclear Information System (INIS)

    Kim, J.J.; Makino, H.; Hanada, T.; Cho, M.W.; Yao, T.; Takata, Y.; Nishino, Y.; Tamasaku, K.; Ishikawa, T.; Shin, S.; Kobayashi, K.; Ikenaga, E.; Yabashi, M.; Yamamoto, T.

    2004-01-01

    Full text: It is predicted based on hole-mediated ferromagnetism (FM) that GaMnN may have Curie temperature (Tc) higher than room temperature if doped with high hole concentration (ca 10 20 cm -3 ). The hole-mediated ferromagnetism (FM) can produce reliable estimate of Tc for diluted magnetic semiconductor (DMS) such as GaMnAs due to the shallow Mn-associated energy states in the GaAs system. Since the energy states of doped transition metals exist as a deep level in a wide band semiconductor like GaN and carriers are localized in these states, different mechanisms for magnetism will play a role in GaN rather than the hole-mediated one. This conjecture is partly supported by the recent report of FM in n-type GaN doped with Cr, although the mechanism of the observed FM has not been elucidated yet. In order to get insight into the mechanism of the FM, we have studied the electronic structure of GaN doped with Cr exploiting bulk-sensitive hard X-ray photoemission spectroscopy at a photon energy of 5.95keV at SPring-8. We have observed that Cr-doping does introduce new electronic levels in the band gap and causes some change in the valence band structure. Based on the first principle calculation, the Cr-associated electronic levels in the band gap are assigned to nonbonding and anti-bonding d states, the latter of which pins the Fermi level, while the change of the valence band suggests that the Ga 4s originated states are significantly modified through hybridization with the Cr 3d orbital. The present result evidences that the Ga valence electrons are considerably modified through the interaction with second neighbor Cr atoms. Such hybridization between Ga 4s and Cr 3d may play a significant role in the observed ferromagnetism in Ga 1-x Cr x N

  4. Photoemission study of 5f localization in UPd/sub 3-x/(Pt,Rh)/sub x/

    International Nuclear Information System (INIS)

    Arko, A.J.; Koelling, D.D.; Dunlap, B.D.; Mitchell, A.W.

    1987-10-01

    Photoemission measurements in the two systems UPd/sub 3-x/(Pt,Rh)/sub x/ show that the 5f spectra are consistent with localized 5f electrons (peak in spectral weight is below E/sub F/ for all x within the double hexagonal DO 24 phase) while at both phase transitions the 5f peaks lock in at E/sub F/ consistent with intinerancy. A satellite 5f peak representative of d-screening is observed in both localized and itinerant systems. 17 refs., 3 figs

  5. Photoemission study of the temperature-dependent energy-gap formation in the Kondo semiconductor CeRhAs

    International Nuclear Information System (INIS)

    Shimada, K.; Arita, M.; Takeda, Y.; Namatame, H.; Taniguchi, M.; Higashiguchi, M.; Oguchi, T.; Sasakawa, T.; Suemitsu, T.; Takabatake, T.

    2004-01-01

    Full text: The orthorhombic CeRhAs, known as a Kondo semiconductor, has attracted much interest for its unusual energy-gap formation associated with the successive 1st order phase transitions. In order to elucidate the mechanism of the energy- gap formation, we have done high-resolution temperature-dependent photoemission spectroscopy on the undulator beamlines of a compact electron-storage ring, HiSOR, at Hiroshima University. We have observed directly the energy-gap formation in the Ce 4f states and in the conduction bands. Comparing with the isostructural Kondo semimetal CeRhSb, we discuss the energy gap formation in CeRhAs

  6. Bulk superconducting gap of V{sub 3}Si studied by low-energy ultrahigh-resolution photoemission spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Sato, T., E-mail: t-sato@arpes.phys.tohoku.ac.jp [Department of Physics, Tohoku University, Sendai 980-8578 (Japan); Souma, S. [WPI Research Center, Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Nakayama, K. [Department of Physics, Tohoku University, Sendai 980-8578 (Japan); Sugawara, K. [WPI Research Center, Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Toyota, N. [Department of Physics, Tohoku University, Sendai 980-8578 (Japan); Takahashi, T. [Department of Physics, Tohoku University, Sendai 980-8578 (Japan); WPI Research Center, Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan)

    2016-04-15

    Highlights: • We report ultrahigh-resolution photoemission spectroscopy of A15 compound V{sub 3}Si. • We found a sharp quasiparticle peak due to superconducting-gap opening. • The surface metallic component is negligibly small in the bulk-sensitive measurement. • We show that V{sub 3}Si is a single-gap s-wave superconductor. - Abstract: We have performed low-energy ultrahigh-resolution photoemission spectroscopy (PES) of A15 compound V{sub 3}Si with a xenon-plasma discharge lamp to elucidate the bulk superconducting gap. Below the superconducting transition temperature (T{sub c} = 15.9 K), we found a sharp quasiparticle peak at the Fermi level in the PES spectrum. The gap spectrum is well fitted by a single s-wave superconducting-gap function together with a dip structure at ∼30 meV suggestive of a strong electron-phonon coupling. The anomalous in-gap state previously observed in the PES measurement with high-energy photons is absent or negligibly small in the present bulk-sensitive measurement. The present PES result shows that V{sub 3}Si is a single-gap s-wave superconductor.

  7. Bulk superconducting gap of V_3Si studied by low-energy ultrahigh-resolution photoemission spectroscopy

    International Nuclear Information System (INIS)

    Sato, T.; Souma, S.; Nakayama, K.; Sugawara, K.; Toyota, N.; Takahashi, T.

    2016-01-01

    Highlights: • We report ultrahigh-resolution photoemission spectroscopy of A15 compound V_3Si. • We found a sharp quasiparticle peak due to superconducting-gap opening. • The surface metallic component is negligibly small in the bulk-sensitive measurement. • We show that V_3Si is a single-gap s-wave superconductor. - Abstract: We have performed low-energy ultrahigh-resolution photoemission spectroscopy (PES) of A15 compound V_3Si with a xenon-plasma discharge lamp to elucidate the bulk superconducting gap. Below the superconducting transition temperature (T_c = 15.9 K), we found a sharp quasiparticle peak at the Fermi level in the PES spectrum. The gap spectrum is well fitted by a single s-wave superconducting-gap function together with a dip structure at ∼30 meV suggestive of a strong electron-phonon coupling. The anomalous in-gap state previously observed in the PES measurement with high-energy photons is absent or negligibly small in the present bulk-sensitive measurement. The present PES result shows that V_3Si is a single-gap s-wave superconductor.

  8. A high resolution photoemission study of surface core-level shifts in clean and oxygen-covered Ir(2 1 0) surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Gladys, M.J.; Ermanoski, I.; Jackson, G.; Quinton, J.S.; Rowe, J.E.; Madey, T.E. E-mail: madey@physics.rutgers.edu

    2004-04-01

    High resolution soft X-ray photoemission electron spectroscopy (SXPS), using synchrotron radiation, is employed to investigate 4f core-level features of four differently-prepared Ir(2 1 0) surfaces: clean planar, oxygen-covered planar, oxygen-induced faceted, and clean faceted surfaces. Surface and bulk peak identifications are supported by measurements at different photon energies (thus probing different electron escape depths) and variable emission angles. Iridium 4f{sub 7/2} photoemission spectra are fitted with Doniach-Sunjic lineshapes. The surface components are identified with core levels positioned at lower binding energies than the bulk components, in contrast to previous reports of binding energy inversion on Ir(1 0 0) (1x1) and (5x1) surfaces. For clean planar Ir(2 1 0) three surface Ir 4f{sub 7/2} features are observed with core-level shifts of -765, -529, and -281 meV, with respect to the bulk; these are associated with the first, second and third layers of atoms, respectively, for atomically rough Ir(2 1 0). Adsorption of oxygen onto the planar Ir(2 1 0) surface is found to cause a suppression and shift of the surface features to higher binding energies. Annealing at T{>=}600 K in oxygen produces a faceted surface as verified by low energy electron diffraction (LEED). A comparison of planar and faceted oxygen-covered surfaces reveals minor differences in the normal emission SXPS spectra, while grazing emission spectra exhibit differences. The SXPS spectrum of the clean, faceted Ir(2 1 0) exhibits small differences in comparison to the clean planar case, with surface features having binding energy shifts of -710, -450, and -230 meV.

  9. Electronic structure studies of ferro-pnictide superconductors and their parent compounds using angle-resolved photoemission spectroscopy (ARPES)

    International Nuclear Information System (INIS)

    Setti, Thirupathaiah

    2011-01-01

    The discovery of high temperature superconductivity in the iron pnictide compound LaO 1-x F x FeAs with T c = 26 K as created enormous interest in the high-T c superconductor community. So far, four prototypes of crystal structures have been found in the Fe-pnictide family. All four show a structural deformation followed or accompanied by a magnetic transition from a high temperature paramagnetic conductor to a low temperature antiferromagnetic metal whose transition temperature T N varies between the compounds. Charge carrier doping, isovalent substitution of the As atoms or the application of pressure suppresses the antiferromagnetic spin density wave (SDW) order and leads to a superconducting phase. More recently high Tc superconductivity has been also detected in iron chalchogenides with similar normal state properties. Since superconductivity is instability of the normal state, the study of normal state electronic structure in comparison with superconducting state could reveal important information on the pairing mechanism. Therefore, it is most important to study the electronic structure of these new superconductors, i.e., to determine Fermi surfaces and band dispersions near the Fermi level at the high symmetry points in order to obtain a microscopic understanding of the superconducting properties. Using the technique angle-resolved photoemission spectroscopy (ARPES) one measures the electrons ejected from a sample when photons impinge on it. In this way one can map the Fermi surface which provides useful information regarding the physics behind the Fermi surface topology of high T c superconductors. Furthermore, this technique provides information on the band dispersion, the orbital character of the bands, the effective mass, the coupling to bosonic excitations, and the superconducting gap. This emphasizes the importance of studying the electronic structure of the newly discovered Fe-pnictides using ARPES. In this work we have studied the electronic

  10. Electronic structure studies of ferro-pnictide superconductors and their parent compounds using angle-resolved photoemission spectroscopy (ARPES)

    Energy Technology Data Exchange (ETDEWEB)

    Setti, Thirupathaiah

    2011-07-14

    The discovery of high temperature superconductivity in the iron pnictide compound LaO{sub 1-x}F{sub x}FeAs with T{sub c} = 26 K as created enormous interest in the high-T{sub c} superconductor community. So far, four prototypes of crystal structures have been found in the Fe-pnictide family. All four show a structural deformation followed or accompanied by a magnetic transition from a high temperature paramagnetic conductor to a low temperature antiferromagnetic metal whose transition temperature T{sub N} varies between the compounds. Charge carrier doping, isovalent substitution of the As atoms or the application of pressure suppresses the antiferromagnetic spin density wave (SDW) order and leads to a superconducting phase. More recently high Tc superconductivity has been also detected in iron chalchogenides with similar normal state properties. Since superconductivity is instability of the normal state, the study of normal state electronic structure in comparison with superconducting state could reveal important information on the pairing mechanism. Therefore, it is most important to study the electronic structure of these new superconductors, i.e., to determine Fermi surfaces and band dispersions near the Fermi level at the high symmetry points in order to obtain a microscopic understanding of the superconducting properties. Using the technique angle-resolved photoemission spectroscopy (ARPES) one measures the electrons ejected from a sample when photons impinge on it. In this way one can map the Fermi surface which provides useful information regarding the physics behind the Fermi surface topology of high T{sub c} superconductors. Furthermore, this technique provides information on the band dispersion, the orbital character of the bands, the effective mass, the coupling to bosonic excitations, and the superconducting gap. This emphasizes the importance of studying the electronic structure of the newly discovered Fe-pnictides using ARPES. In this work we have

  11. Ambient pressure photoemission spectroscopy of metal surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Baikie, Iain D., E-mail: iain@kptechnology.ltd.uk; Grain, Angela C.; Sutherland, James; Law, Jamie

    2014-12-30

    Highlights: • Ambient pressure photoemission spectroscopy of metals. • Rastered photon energy scan overcomes inelastic scattering. • Relationship between photoemission threshold and contact potential difference. - Abstract: We describe a novel photoemission technique utilizing a traditional Kelvin probe as a detector of electrons/atmospheric ions ejected from metallic surfaces (Au, Ag, Cu, Fe, Ni, Ti, Zn, Al) illuminated by a deep ultra-violet (DUV) source under ambient pressure. To surmount the limitation of electron scattering in air the incident photon energy is rastered rather than applying a variable retarding electric field as is used with UPS. This arrangement can be applied in several operational modes: using the DUV source to determine the photoemission threshold (Φ) with 30–50 meV resolution and also the Kelvin probe, under dark conditions, to measure contact potential difference (CPD) between the Kelvin probe tip and the metallic sample with an accuracy of 1–3 meV. We have studied the relationship between the photoelectric threshold and CPD of metal surfaces cleaned in ambient conditions. Inclusion of a second spectroscopic visible source was used to confirm a semiconducting oxide, possibly Cu{sub 2}O, via surface photovoltage measurements with the KP. This dual detection system can be easily extended to controlled gas conditions, relative humidity control and sample heating/cooling.

  12. Future directions in standing-wave photoemission

    Energy Technology Data Exchange (ETDEWEB)

    Gray, Alexander X., E-mail: axgray@temple.edu

    2014-08-15

    Highlights: • Probing magnetic properties at the buried interface with SW-MCD. • Probing electronic structure at the buried interface with resonant SW-XPS and SW-HAXPES. • Probing momentum-resolved electronic structure at a buried interface with SWARPES. • Adding depth resolution to photoemission microscopy with standing-wave excitation. • Standing-wave localization, total reflection and waveguide effects. - Abstract: Over the past decade, standing-wave photoemission (SW-XPS) has evolved into a powerful and versatile non-destructive technique for probing element-specific electronic, magnetic, and structural properties of buried layers and interfaces with sub-nanometer depth resolution. In this article, I will discuss several promising future directions in this emergent field stemming from experimental and theoretical studies wherein SW-XPS is combined with other X-ray techniques, such as magnetic circular dichroism (MCD), hard X-ray photoemission spectroscopy (HAXPES), angle-resolved photoemission (ARPES), and photoemission microscopy (PEEM), adding extra dimensions to the measurement and thus widening the scope of scientific and technological questions accessible via the use of standing waves. I will further discuss examples of recently developed methods for X-ray standing-wave data analysis, which yield layer-resolved matrix-element-weighted densities of states at interfaces as well as Ångstrom-level changes in periodicity of synthetic superlattices. Finally, I will explore the possibility of localizing the standing waves near the surface and within a buried layer by the use of aperiodic superlattices, total reflection, and X-ray waveguide effects.

  13. Future directions in standing-wave photoemission

    International Nuclear Information System (INIS)

    Gray, Alexander X.

    2014-01-01

    Highlights: • Probing magnetic properties at the buried interface with SW-MCD. • Probing electronic structure at the buried interface with resonant SW-XPS and SW-HAXPES. • Probing momentum-resolved electronic structure at a buried interface with SWARPES. • Adding depth resolution to photoemission microscopy with standing-wave excitation. • Standing-wave localization, total reflection and waveguide effects. - Abstract: Over the past decade, standing-wave photoemission (SW-XPS) has evolved into a powerful and versatile non-destructive technique for probing element-specific electronic, magnetic, and structural properties of buried layers and interfaces with sub-nanometer depth resolution. In this article, I will discuss several promising future directions in this emergent field stemming from experimental and theoretical studies wherein SW-XPS is combined with other X-ray techniques, such as magnetic circular dichroism (MCD), hard X-ray photoemission spectroscopy (HAXPES), angle-resolved photoemission (ARPES), and photoemission microscopy (PEEM), adding extra dimensions to the measurement and thus widening the scope of scientific and technological questions accessible via the use of standing waves. I will further discuss examples of recently developed methods for X-ray standing-wave data analysis, which yield layer-resolved matrix-element-weighted densities of states at interfaces as well as Ångstrom-level changes in periodicity of synthetic superlattices. Finally, I will explore the possibility of localizing the standing waves near the surface and within a buried layer by the use of aperiodic superlattices, total reflection, and X-ray waveguide effects

  14. Chlorine-induced modifications in the electronic structure of Ag surfaces: a metastable deexcitation spectroscopy and photoemission comparative study

    CERN Document Server

    Pasquali, L; Canepa, M; Staicu-Casagrande, E M; Esaulov, V A

    2003-01-01

    Surface-sensitive spectroscopic techniques, namely metastable deexcitation spectroscopy (MDS) and ultraviolet photoemission (UPS), have been applied to investigate the effects of chlorine chemisorption on the electronic properties (surface density of states and charge density) of Ag(100), Ag(110) and Ag(111) surfaces. Initial stages of chemisorption, up to the formation of a saturated Cl overlayer, have been examined. In particular, MDS permitted us to observe at low Cl gas exposure a progressive depletion of the Ag (5s) charge due to transfer and bonding with Cl atoms. From both MDS and UPS it was possible to observe the development of Cl (3p) bonding and anti-bonding states, the amount of their splitting increasing with coverage. Differences between chemisorption at the three surfaces have been noticed and they have been justified in terms of the different adatom packing and possible formation of small AgCl clusters (especially for the Ag(111) surface).

  15. Electronic structure of the Ga1-xCr xN studied by high-energy photoemission spectroscopy

    International Nuclear Information System (INIS)

    Kim, J.J.; Makino, H.; Yao, T.; Takata, Y.; Kobayashi, K.; Yamamoto, T.; Hanada, T.; Cho, M.W.; Ikenaga, E.; Yabashi, M.; Miwa, D.; Nishino, Y.; Tamasaku, K.; Ishikawa, T.; Shin, S.

    2005-01-01

    Valence band spectra of Ga 1-x Cr x N have been investigated by high-energy photoemission spectroscopy at the photon energy of 5.95 keV. Cr doping does introduce a novel electronic structure in the bandgap and causes some change in valence band structure. Based on the first-principle calculation, Cr-associated electronic levels in the bandgap are assigned to nonbonding and antibonding d states while the change of the valence band suggests that the Ga 4s originated states are significantly modified through hybridization with the Cr 3d orbital. The present result evidences that the Ga valence electrons are considerably modified through the interaction with the second nearest-neighbour Cr atoms

  16. Chlorine-induced modifications in the electronic structure of Ag surfaces: a metastable deexcitation spectroscopy and photoemission comparative study

    International Nuclear Information System (INIS)

    Pasquali, L; Nannarone, S; Canepa, M; Staicu-Casagrande, E M; Esaulov, V A

    2003-01-01

    Surface-sensitive spectroscopic techniques, namely metastable deexcitation spectroscopy (MDS) and ultraviolet photoemission (UPS), have been applied to investigate the effects of chlorine chemisorption on the electronic properties (surface density of states and charge density) of Ag(100), Ag(110) and Ag(111) surfaces. Initial stages of chemisorption, up to the formation of a saturated Cl overlayer, have been examined. In particular, MDS permitted us to observe at low Cl gas exposure a progressive depletion of the Ag (5s) charge due to transfer and bonding with Cl atoms. From both MDS and UPS it was possible to observe the development of Cl (3p) bonding and anti-bonding states, the amount of their splitting increasing with coverage. Differences between chemisorption at the three surfaces have been noticed and they have been justified in terms of the different adatom packing and possible formation of small AgCl clusters (especially for the Ag(111) surface)

  17. Electron attachment rate constant measurement by photoemission electron attachment ion mobility spectrometry (PE-EA-IMS)

    International Nuclear Information System (INIS)

    Su, Desheng; Niu, Wenqi; Liu, Sheng; Shen, Chengyin; Huang, Chaoqun; Wang, Hongmei; Jiang, Haihe; Chu, Yannan

    2012-01-01

    Photoemission electron attachment ion mobility spectrometry (PE-EA-IMS), with a source of photoelectrons induced by vacuum ultraviolet radiation on a metal surface, has been developed to study electron attachment reaction at atmospheric pressure using nitrogen as the buffer gas. Based on the negative ion mobility spectra, the rate constants for electron attachment to tetrachloromethane and chloroform were measured at ambient temperature as a function of the average electron energy in the range from 0.29 to 0.96 eV. The experimental results are in good agreement with the data reported in the literature. - Highlights: ► Photoemission electron attachment ion mobility spectrometry (PE-EA-IMS) was developed to study electron attachment reaction. ► The rate constants of electron attachment to CCl 4 and CHCl 3 were determined. ► The present experimental results are in good agreement with the previously reported data.

  18. Inverse photoemission of uranium oxides

    International Nuclear Information System (INIS)

    Roussel, P.; Morrall, P.; Tull, S.J.

    2009-01-01

    Understanding the itinerant-localised bonding role of the 5f electrons in the light actinides will afford an insight into their unusual physical and chemical properties. In recent years, the combination of core and valance band electron spectroscopies with theoretic modelling have already made significant progress in this area. However, information of the unoccupied density of states is still scarce. When compared to the forward photoemission techniques, measurements of the unoccupied states suffer from significantly less sensitivity and lower resolution. In this paper, we report on our experimental apparatus, which is designed to measure the inverse photoemission spectra of the light actinides. Inverse photoemission spectra of UO 2 and UO 2.2 along with the corresponding core and valance electron spectra are presented in this paper. UO 2 has been reported previously, although through its inclusion here it allows us to compare and contrast results from our experimental apparatus to the previous Bremsstrahlung Isochromat Spectroscopy and Inverse Photoemission Spectroscopy investigations

  19. Crystal structure and X-ray photoemission spectroscopic study of A{sub 2}LaMO{sub 6} [A=Ba, Ca; M=Nb, Ta

    Energy Technology Data Exchange (ETDEWEB)

    Dutta, Alo, E-mail: alo_dutta@yahoo.com [Department of Condensed Matter Physics and Material Sciences, S. N. Bose National Centre for Basic Sciences, Block-JD, Sector-III, Salt Lake, Kolkata 700098 (India); Saha, Sujoy [Department of Physics, Bose Institute, 93/1 Acharya Prafulla Chandra Road, Kolkata 700009 (India); Kumari, Premlata [Department of Chemistry, Government P.G. College, Lansdowne, Pauri-Garhwal 246139 (India); Sinha, T.P. [Department of Physics, Bose Institute, 93/1 Acharya Prafulla Chandra Road, Kolkata 700009 (India); Shannigrahi, Santiranjan [Institute of Materials Research and Engineering, Agency for Science Technology and Research, 3 Research Link, Singapore 117602 (Singapore)

    2015-09-15

    The X-ray photoemission spectroscopic (XPS) study of the double perovskite oxides A{sub 2}LaMO{sub 6} [A=Ba, Ca; M=Nb, Ta] synthesized by the solid-state reaction technique has been carried out to investigate the nature of the chemical state of the constituent ions and the bonding between them. The Rietveld refinement of the X-ray diffraction patterns suggests the monoclinic crystal structure of all the materials at room temperature. The negative and positive chemical shifts of the core level XPS spectrum of O-1s and Nb-3d{sub 3/2}/Ta-4f{sub 5/2} respectively suggest the covalent bonding between Nb/Ta cations and O ion. The change of the bonding strength between the anion and the cations from one material to another has been analyzed. The vibrational property of the materials is investigated using the room temperature Raman spectra. A large covalency of Ta-based compound than Nb compound is confirmed from the relative shifting of the Raman modes of the materials. - Graphical abstract: Crystal structure of two perovskite oxides CLN and CLT is investigated. XPS study confirms the two different co-ordination environments of Ca and covalent bonding between B-site cations and O-ion. - Highlights: • Ordered perovskite structure obtained by Rietveld refinement of XRD patterns. • Study of nature of chemical bonding by X-ray photoemission spectroscopy. • Opposite chemical shift of d-states of Nb/Ta with respect to O. • Covalent bonding between d-states of Nb/Ta and O. • Relative Raman shifts of CLN and CLT substantiate the more covalent character of Ta than Nb.

  20. Temperature-induced valence transition in EuNi2(Si0.20Ge0.80)2 studied by hard X-ray photoemission spectroscopy

    International Nuclear Information System (INIS)

    Yamamoto, Kazuya; Kamakura, Nozomu; Taguchi, Munetaka; Chainani, Ashish; Takata, Yasutaka; Horiba, Koji; Shin, Shik; Ikenaga, Eiji; Mimura, Kojiro; Shiga, Masayuki; Wada, Hirofumi; Namatame, Hirofumi; Taniguchi, Masaki; Awaji, Mitsuhiro; Takeuchi, Akihisa; Nishino, Yoshinori; Miwa, Daigo; Tamasaku, Kenji; Ishikawa, Tetsuya; Kobayashi, Keisuke

    2005-01-01

    The temperature-induced mixed valence transition in EuNi 2 (Si 0.20 Ge 0.80 ) 2 has been investigated by hard X-ray (5940 eV) photoemission spectroscopy (HX-PES) for fractured surfaces, with a probing depth larger than 5 nm. The Eu 3d core-level states are studied below and above the critical valence transition temperature, T v = 80 K. The HX-PES spectra at 40 and 120 K show the mixed valence transition, with clear changes in the divalent and trivalent Eu 3d chemically shifted features. The Eu 3d HX-PES spectra indicate a mean valence of 2.70 ± 0.03 at 40 K which changes to 2.40 ± 0.03 at 120 K, in good accordance with the results of bulk Eu III -edge X-ray absorption spectroscopy measurements

  1. Electronic structure investigation of MoS2 and MoSe2 using angle-resolved photoemission spectroscopy and ab initio band structure studies.

    Science.gov (United States)

    Mahatha, S K; Patel, K D; Menon, Krishnakumar S R

    2012-11-28

    Angle-resolved photoemission spectroscopy (ARPES) and ab initio band structure calculations have been used to study the detailed valence band structure of molybdenite, MoS(2) and MoSe(2). The experimental band structure obtained from ARPES has been found to be in good agreement with the theoretical calculations performed using the linear augmented plane wave (LAPW) method. In going from MoS(2) to MoSe(2), the dispersion of the valence bands decreases along both k(parallel) and k(perpendicular), revealing the increased two-dimensional character which is attributed to the increasing interlayer distance or c/a ratio in these compounds. The width of the valence band and the band gap are also found to decrease, whereas the valence band maxima shift towards the higher binding energy from MoS(2) to MoSe(2).

  2. Plasmon Enhanced Photoemission

    Energy Technology Data Exchange (ETDEWEB)

    Polyakov, Aleksandr [Univ. of California, Berkeley, CA (United States)

    2012-05-08

    Next generation ultrabright light sources will operate at megahertz repetition rates with temporal resolution in the attosecond regime. For an X-Ray Free Electron Laser (FEL) to operate at such repetition rate requires a high quantum efficiency (QE) cathode to produce electron bunches of 300 pC per 1.5 μJ incident laser pulse. Semiconductor photocathodes have sufficient QE in the ultraviolet (UV) and the visible spectrum, however, they produce picosecond electron pulses due to the electron-phonon scattering. On the other hand, metals have two orders of magnitude less QE, but can produce femtosecond pulses, that are required to form the optimum electron distribution for high efficiency FEL operation. In this work, a novel metallic photocathode design is presented, where a set of nano-cavities is introduced on the metal surface to increase its QE to meet the FEL requirements, while maintaining the fast time response. Photoemission can be broken up into three steps: (1) photon absorption, (2) electron transport to the surface, and (3) crossing the metal-vacuum barrier. The first two steps can be improved by making the metal completely absorbing and by localizing the fields closer to the metal surface, thereby reducing the electron travel distance. Both of these effects can be achieved by coupling the incident light to an electron density wave on the metal surface, represented by a quasi-particle, the Surface Plasmon Polariton (SPP). The photoemission then becomes a process where the photon energy is transferred to an SPP and then to an electron. The dispersion relation for the SPP defines the region of energies where such process can occur. For example, for gold, the maximum SPP energy is 2.4 eV, however, the work function is 5.6 eV, therefore, only a fourth order photoemission process is possible. In such process, four photons excite four plasmons that together excite only one electron. The yield of such non-linear process depends strongly on the light intensity. In

  3. Photoemission measurements for low energy x-ray detector applications

    International Nuclear Information System (INIS)

    Day, R.H.

    1981-01-01

    Photoemission has been studied for nearly 100 years as both a means of investigating quantum physics, and as a practical technique for transducing optical/x-ray photons into electrical currents. Numerous x-ray detection schemes, such as streak cameras and x-ray sensitive diodes, exploit this process because of its simplicity, adaptability, and speed. Recent emphasis on diagnostics for low temperature, high density, and short-lived, plasmas for inertial confinement fusion has stimulated interest in x-ray photoemission in the sub-kilovolt regime. In this paper, a review of x-ray photoemission measurements in the 50 eV to 10 keV x-ray region is given and the experimental techniques are reviewed. A semiempirical model of x-ray photoemission is discussed and compared to experimental measurements. Finally, examples of absolutely calibrated instruments are shown

  4. Radiation Studies, Vol.10

    International Nuclear Information System (INIS)

    Nadareishvili, K.; Tsitskishvili, M.; Chankseliani, Z.; Gelashvili, K.; Mtskhoetadze, A.; Oniani, T.; Todua, F.; Vepkhoadze, N.; Zaalishvili, T.

    2002-01-01

    'Radiation studies' - is a periodical edition of Scientific Research Center of Radiobiology and Radiation Ecology of Georgian Academy of Sciences, Problem Council of Radiobiology of Georgian Academy of Sciences and Georgian Academy of Ecological Sciences. The 10th volume of 'Radiation studies' reflects activities of above-mentioned institutions during previous two years and contains 26 articles, from which 17 are within the scope of INIS

  5. Electronic Structure of the Kitaev Material α-RuCl3 Probed by Photoemission and Inverse Photoemission Spectroscopies

    OpenAIRE

    Soobin Sinn; Choong Hyun Kim; Beom Hyun Kim; Kyung Dong Lee; Choong Jae Won; Ji Seop Oh; Moonsup Han; Young Jun Chang; Namjung Hur; Hitoshi Sato; Byeong-Gyu Park; Changyoung Kim; Hyeong-Do Kim; Tae Won Noh

    2016-01-01

    Recently, $\\alpha$-$\\textrm{RuCl}_3$ has attracted much attention as a possible material realization of the honeycomb Kitaev model, which may stabilize a quantum-spin-liquid state. Compared to extensive studies on its magnetic properties, there is still a lack of understanding on its electronic structure, which is strongly related with its Kitaev physics. Here, the electronic structure of $\\alpha$-$\\textrm{RuCl}_3$ is investigated by photoemission (PE) and inverse photoemission (IPE) spectros...

  6. Electronic structure of YbNiX{sub 3} (X =Si, Ge) studied by hard X-ray photoemission spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Sato, Hitoshi; Shimada, Kenya; Namatame, Hirofumi [Hiroshima Synchrotron Radiation Center, Hiroshima University, Kagamiyama 2-313, Higashi-Hiroshima 739-0046 (Japan); Utsumi, Yuki [Max-Planck Institute for Chemical Physics of Solids, 01187 Dresden (Germany); Kodama, Junichi; Nagata, Heisuke [Graduate School of Science, Hiroshima University, Kagamiyama 1-3-1, Higashi-Hiroshima 739-8526 (Japan); Avila, Marcos A.; Ribeiro, Raquel A. [Centro de Ciencias Naturais e Humanas, Universidade Federal do ABC, Santo Andre - SP, 09210-580 (Brazil); Umeo, Kazunori [Cryogenics and Instrumental Analysis Division, N-BARD, Hiroshima University, Higashi-Hiroshima 739-8526 (Japan); Takabatake, Toshiro [Department of Quantum Matter, AdSM, Hiroshima University, Higashi-Hiroshima 739-8530 (Japan); Institute for Advanced Materials Research, Hiroshima University, Higashi-Hiroshima 739-8530 (Japan); Mimura, Kojiro; Motonami, Satoru; Anzai, Hiroaki [Graduate School of Engineering, Osaka Prefecture University, Sakai 599-8531 (Japan); Ueda, Shigenori [Synchrotron X-ray Station at SPring-8, National Institute for Materials Science, Hyogo 679-5148 (Japan); Taniguchi, Masaki [Hiroshima Synchrotron Radiation Center, Hiroshima University, Kagamiyama 2-313, Higashi-Hiroshima 739-0046 (Japan); Graduate School of Science, Hiroshima University, Kagamiyama 1-3-1, Higashi-Hiroshima 739-8526 (Japan)

    2015-06-15

    lectronic structure of the Kondo lattices YbNiX{sub 3} (X =Si, Ge) has been investigated by means of hard x-ray photoemission spectroscopy (HAXPES) with hν = 5.95 keV. From the Yb 3d HAXPES spectra, the Yb valence in YbNiSi{sub 3} is estimated to be ∝ 2.92, which is almost temperature-independent. On the other hand, the valence in YbNiGe{sub 3} is estimated to be 2.48 at 300 K, showing significant valence fluctuation, and gradually decreases to 2.41 at 20 K on cooling. The Ni 2p{sub 3/2} and Yb{sup 3+} 4f peaks exhibit opposite energy shifts amounting to ∝ 0.6 eV between YbNiSi{sub 3} and YbNiGe{sub 3}. We propose a simple model for the electronic structure of YbNiX{sub 3} based on the HAXPES results. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  7. A study of angle-resolved photoemission extended fine structure as applied to the Ni 3p, Cu 3s, and Cu 3p core levels of the respective clean (111) surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Huff, W.R.A.; Moler, E.J.; Kellar, S.A. [Lawrence Berkeley National Lab., CA (United States)] [and others

    1997-04-01

    The first non-s initial state angle-resolved photoemission extended fine structure (ARPEFS) study of clean surfaces for the purpose of further understanding the technique is reported. The surface structure sensitivity of ARPEFS applied to clean surfaces and to arbitrary initial states is studied using normal photoemission data taken from the Ni 3p core levels of a Ni(111) single crystal and the Cu 3s and the Cu 3p core-levels of a Cu(111) single crystal. The Fourier transforms of these clean surface data are dominated by backscattering. Unlike the s initial state data, the p initial state data show a peak in the Fourier transform corresponding to in-plane scattering from the six nearest-neighbors to the emitter. Evidence was seen for single-scattering events from in the same plane as the emitters and double-scattering events. Using a newly developed, multiple-scattering calculation program, ARPEFS data from clean surfaces and from p initial states can be modeled to high precision. Although there are many layers of emitters when measuring photoemission from a clean surface, test calculations show that the ARPEFS signal is dominated by photoemission from atoms in the first two crystal layers. Thus, ARPEFS applied to clean surfaces is sensitive to surface reconstruction. The known contraction of the first two Cu(111) layers is confirmed. The best-fit calculation for clean Ni(111) indicates an expansion of the first two layers. To better understand the ARPEFS technique, the authors studied s and non-s initial state photoemission from clean metal surfaces.

  8. UNCONTROLLED PHOTOMULTIPLIER CURRENT IN PHOTOEMISSION ANALYSIS

    Directory of Open Access Journals (Sweden)

    K. A. Viazava

    2016-01-01

    Full Text Available The dependence of photon energy from energy of photoelectron is base of photoemission radiation analysis. In such photoemission measurements except current of photocathode is always exist a reverse current from the collector of electrons to the photocathode in two-electrode sensors. There are various ways of reverse and uncontrolled current eliminating or reducing their influence. The constructive method is based on creating an electron-optical system of photoelectronic device, which would be a photoelectron energy analyzer. The second method – technological. However, it requires the manufacture of the photocathode and the dynode system in different vacuum chamber with subsequent connection to a single device in vacuum environment without exposure to the atmosphere. The purpose of this article is to determinate the effect of photoemission from photocathode chamber and the first dynode of photomultiplier on energy distribution of the photoelectrons from photocathode. To solve this problem authors obtained calibration curves for measuring pyrometer module ПИФ 4/2 with ФЭУ-114 as a sensor at supply voltage 1350 V and different decelerating voltages. The effect of illumination on the value of modulation coefficient on temperature k(T and wavelength k(λ is shown. In temperature measurements, this effect is evident in fact that at temperatures below 1400 K linear dependence ln k – T-1 is broken. Still this linear dependence is a necessary consequence of the fact that the measured temperature is color temperature. However, this calibration curve can be used to measure low temperature if the target measurements condition and calibration conditions are identical. In wavelength calibration, curve k(λ at λ > 760 nm is two-valued, that doesn’t allow to identify monochromatic radiation by this method and bring in errors in temperature measurements. 

  9. Angle-resolved photoemission study and first-principles calculation of the electronic structure of LaSb2

    International Nuclear Information System (INIS)

    Acatrinei, Alice I; Browne, D; Losovyj, Y B; Young, D P; Moldovan, M; Chan, Julia Y; Sprunger, P T; Kurtz, Richard L

    2003-01-01

    In this work we present valence band studies of LaSb 2 using angle-resolved photoelectron spectroscopy with synchrotron radiation and compare these data with band structure calculations. Valence band spectra reveal that Sb 5p states are dominant near the Fermi level and are hybridized with the La 5d states just below. The calculations show a fair agreement with the experimentally determined valence band spectra, allowing an identification of the observed features. We measured some dispersion for kbar, especially for Sb 5p states; no significant dispersion was found for k || . (letter to the editor)

  10. Nonrelativistic quantum electrodynamic approach to photoemission theory

    International Nuclear Information System (INIS)

    Fujikawa, Takashi; Arai, Hiroko

    2005-01-01

    A new nonrelativistic many-body theory to analyze X-ray photoelectron spectroscopy (XPS) spectra has been developed on the basis of quantum electrodynamic (QED) Keldysh Green's function approach. To obtain XPS current density we calculate electron Green's function g which partly includes electron-photon interactions. We first separate longitudinal and transverse parts of these Green's functions in the Coulomb gauge. The transverse electron selfenergy describes the electron-photon interaction, whereas the longitudinal electron selfenergy describes the electron-electron interaction. We derive the QED Hedin's equation from which we obtain systematic skeleton expansion in the power series of the screened Coulomb interaction W and the photon Green's function D kl . We show the present theory provides a sound theoretical tool to study complicated many-body processes such as the electron propagation damping, intrinsic, extrinsic losses and their interference, and furthermore, resonant photoemission processes. We have also found the importance of the mixed photon Green's functions D 0k and D k0 which have been supposed to be unimportant for the XPS analyses. They, however, directly describe the radiation field screening. In this work, photon field screening effects are discussed in one-step theory, where the electron-photon interaction operator Δ is proved to be replaced by ε -1 Δ beyond linear approximation. Beyond free photon Green's function approximation, photon scatterings from the electron density are incorporated within the present QED theory. These photon field effects can directly describe the microscopic photon field spatial variation specific to near the surface region and nanoparticle systems

  11. Vacuum scanning capillary photoemission microscopy.

    Science.gov (United States)

    Aseyev, S A; Cherkun, A P; Mironov, B N; Petrunin, V V; Chekalin, S V

    2017-08-01

    We demonstrate the use of a conical capillary in a scanning probe microscopy for surface analysis. The probe can measure photoemission from a substrate by transmitting photoelectrons along the capillary as a function of probe position. The technique is demonstrated on a model substrate consisting of a gold reflecting layer on a compact disc which has been illuminated by an unfocused laser beam with a wavelength 400nm, from a femtosecond laser with a beam size of 4mm. A quartz capillary with a 2-µm aperture has been used in the experiments. The period of gold microstructure, shown to be 1.6µ, was measured by the conical probe operating in shear force mode. In shear force regime, the dielectric capillary has been used as a "classical" SPM tip, which provided images reflecting the surface topology. In a photoelectron regime photoelectrons passed through hollow tip and entered a detector. The spatial distribution of the recorded photoelectrons consisted of periodic mountain-valley strips, resembling the surface profile of the sample. Submicron spatial resolution has been achieved. This approach paves the way to study pulsed photodesorption of large organic molecular ions with high spatial and element resolution using the combination of a hollow-tip scanner with time-of-flight technique. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. Radiation carcinogenesis, laboratory studies

    International Nuclear Information System (INIS)

    Shellabarger, C.J.

    1974-01-01

    Laboratory studies on radioinduced carcinogenesis are reviewed. Some topics discussed are: radioinduced neoplasia in relation to life shortening; dose-response relationships; induction of skin tumors in rats by alpha particles and electrons; effects of hormones on tumor response; effects of low LET radiations delivered at low dose-rates; effects of fractionated neutron radiation; interaction of RBE and dose rate effects; and estimates of risks for humans from animal data. (U.S.)

  13. X-ray excited optical luminescence, photoluminescence, photostimulated luminescence and x-ray photoemission spectroscopy studies on BaFBr:Eu

    CERN Document Server

    Subramanian, N; Govinda-Rajan, K; Mohammad-Yousuf; Santanu-Bera; Narasimhan, S V

    1997-01-01

    The results of x-ray excited optical luminescence (XEOL), photoluminescence (PL), photostimulated luminescence (PSL) and x-ray photoemission spectroscopy (XPS) studies on the x-ray storage phosphor BaFBr:Eu are presented in this paper. Analyses of XEOL, PL and PSL spectra reveal features corresponding to the transitions from 4f sup 6 td sup 1 to 4f sup 7 configurations in different site symmetries of Eu sup 2 sup +. Increasing x-ray dose is seen to lead to a red shift in the maximum of the PL excitation spectrum for the 391 nm emission. The XEOL and XPS spectra do not show any signature of Eu sup 3 sup + in the samples studied by us, directly raising doubts about the model of Takahashi et al in which Eu sup 2 sup + is expected to ionize to Eu sup 3 sup + upon x-ray irradiation and remain stable until photostimulation. XEOL and PSL experiments with simultaneous x-ray irradiation and He - Ne laser excitation as well as those with sequential x-ray irradiation and laser stimulation bring out the competition betwe...

  14. Photoemission Experiments for Charge Characteristics of Individual Dust Grains

    Science.gov (United States)

    Abbas, M. M.; Spann, James F., Jr.; Craven, Paul D.; West, E.; Pratico, Jared; Scheianu, D.; Tankosic, D.; Venturini, C. C.; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    Photoemission experiments with UV radiation have been performed to investigate the microphysics and charge characteristics of individual isolated dust grains of various compositions and sizes by using the electrodynamic balance facility at NASA Marshall Space Flight Center. Dust particles of 1 - 100 micrometer diameter are levitated in a vacuum chamber at pressures approx. 10(exp -5) torr and exposed to a collimated beam of UV radiation in the 120-300 nanometers spectral range from a deuterium lamp source with a MgF2 window. A monochromator is used to select the UV radiation wavelength with a spectral resolution of 8 nanometers. The electrodynamic facility permits measurements of the charge and diameters of particles of known composition, and monitoring of photoemission rates with the incident UV radiation. Experiments have been conducted on Al2O3 and silicate particles, and in particular on JSC-1 Mars regolith simulants, to determine the photoelectron yields and surface equilibrium potentials of dust particles when exposed to UV radiation in the 120-250 micrometers spectral range. A brief discussion of the experimental procedure, the results of photoemission experiments, and comparisons with theoretical models will be presented.

  15. High-resolution angle-resolved photoemission studies of high Tc superconductor Bi2Sr2CaCu2O8

    International Nuclear Information System (INIS)

    Liu, Rong.

    1990-01-01

    An angle-resolved photoemission study of the normal and superconducting states in Bi 2 Sr 2 CaCu 2 O 8 was performed. Measurements in the normal state show bands dispersing through the Fermi level from at least 350 meV below E F . The Fermi level crossings are consistant with local-density band calculation, including a point calculated to be of Bi-O character. Additional measurements were made where bands crossed the Fermi level between 100 and 250K, along with measurements on an adjacent Pt foil. The Fermi edges of both materials agree to within the noise. Below the Fermi level, the spectra show correlation effects on the form of an increased effective mass. The shape of the spectra can be explained by a lifetime-broadened photohole and secondary electrons. The effective inverse photohole lifetime is linear in energy. A superconducting gap has been measured at a number of points where there is density at the Fermi level in the normal state. By proper modeling, a gap of 24 meV was obtained for all these points, including points of Cu-O and Bi-O character respectively, according to band calculation. The lack of gap anisotropy in the basal plane suggests that pinning in this material is not d-wave pairing

  16. Photoemission studies of zinc-noble metal alloys: Zn--Cu, Zn--Ag, and Zn--Au films on Ru(001)

    International Nuclear Information System (INIS)

    Rodriguez, J.A.; Hrbek, J.

    1993-01-01

    Zn and the noble metals alloy when coadsorbed on Ru(001). The properties of Zn--Cu, Zn--Ag, and Zn--Au alloys have been studied using core- and valence-level photoemission and temperature programmed desorption. Alloy formation induces only small shifts (-0.2 to -0.3 eV) in the position of the Zn 2p, 3s, and 3d levels. In contrast, the core and valence levels of the noble metals show large shifts toward higher binding energy. For small amounts of Cu, Ag, and Au dissolved in Zn multilayers, the shifts in the core levels of the nobel metals follow the sequence: Cu(2p 3/2 ), 0.8 eV∼Ag(3d 5/2 ), 0.8 eV 7/2 ), 1.4 eV. The magnitude of the shift increases as the Pauling electronegativity of the noble metal increases. However, the sign of the shifts for the Cu(2p 3/2 ), Ag(3d 5/2 ), or Au(4f 7/2 ) levels is not directly determined by the direction of charge transfer within the corresponding Zn-noble metal bond

  17. A novel probe of intrinsic electronic structure: hard X-ray photoemission spectroscopy

    International Nuclear Information System (INIS)

    Takata, Y.; Tamasaku, K.; Nishino, Y.; Miwa, D.; Yabashi, M.; Ikenaga, E.; Horiba, K.; Arita, M.; Shimada, K.; Namatame, H.; Nohira, H.; Hattori, T.; Soedergren, S.; Wannberg, B.; Taniguchi, M.; Shin, S.; Ishikawa, T.; Kobayashi, K.

    2005-01-01

    We have realized hard X-ray (HX) photoemission spectroscopy (PES) with high throughput and high-energy resolution for core level and valence band studies using high-energy and high-brilliance synchrotron radiation at SPring-8. This is a brand new method because large escape depth of high-energy photoelectrons enables us to probe intrinsic bulk states free from surface condition. By use of a newly developed electron energy analyzer and well-focused X-rays, high-energy resolution of 75 meV (E/ΔE 79,000) was realized for 5.95 keV photoelectrons

  18. Giant Cu 2p Resonances in CuO Valence-Band Photoemission

    NARCIS (Netherlands)

    Tjeng, L.H.; Chen, C.T.; Ghijsen, J.; Rudolf, P.; Sette, F.

    1991-01-01

    We report the observation of a giant resonance in the Cu 2p resonant-photoemission spectra of CuO. The study allows the unambiguous identification of the local Cu 3d8 configuration in the valence-band photoemission spectrum, providing conclusive evidence for the charge-transfer nature of the

  19. Energy-resolved photoemission studies of Be-containing surfaces for fusion; Energievariierte Photoemissionsstudien an berylliumhaltigen Oberflaechen fuer die Fusion

    Energy Technology Data Exchange (ETDEWEB)

    Koeppen, Martin

    2013-02-04

    Fusion research aims at the exploitation of the deuterium-tritium reaction for energy production. Next step on the roadmap is the construction of the experimental reactor ITER. The three elements beryllium, carbon and tungsten are to be used as armour materials for the vacuum vessel. After erosion due to plasma processes, these materials are transported and redeposited together with plasma impurities like oxygen from surface oxides. This leads to the formation of compounds by chemical reactions and diffusive processes, induced both by elevated temperatures and implantation of energetic particles. Due to the complexity of the induced surface processes, a method is required which is capable of both qualitative and quantitative analysis of the involved chemical species. X-ray photoelectron spectroscopy (XPS) provides the chemical analysis. Since diffusive processes play an important role in solid-state reactions, a depth-resolved method is required. In this work, energy-resolved XPS using synchrotron radiation with variable photon energies is extended towards a quantitative depth-resolved analysis. For the quantitative analysis a new model is derived which calculates the depth-resolved composition and the respective composition-dependent electron inelastic mean free path in a self-consistent way. Input is the XPS data which is normalized with all parameters influencing the photoelectron intensities. This fully quantitative model is applied to describe the interaction of energetic oxygen ions with the beryllium-tungsten alloy Be{sub 2}W. Oxygen ions from the plasma are able to interact with plasma facing materials. Formation of Be{sub 2}W is to be expected at the first wall and in the divertor region of ITER. Irradiation of this alloy leads to its decompositions. After decomposition, formation of beryllium oxide BeO is preferred compared to formation of tungsten oxides. Heating to 600K leads to chemical reduction of tungsten oxides. Metallic Be acts as reduction agent

  20. Hard X-ray photoemission spectroscopy of transition-metal oxide thin films and interfaces

    International Nuclear Information System (INIS)

    Wadati, H.; Fujimori, A.

    2013-01-01

    Highlights: •Photoemission spectroscopy is a powerful technique to study the electronic structures of transition-metal oxides. •Hard X-ray photoemission spectroscopy (HXPES) is a new type of photoemission spectroscopy which can probe bulk states. •HXPES is very suitable for studying oxide thin films such as the composition dependence and the film thickness dependence. -- Abstract: Photoemission spectroscopy is a powerful experimental technique to study the electronic structures of solids, especially of transition-metal oxides. Recently, hard X-ray photoemission spectroscopy (HXPES) has emerged as a more relevant experimental technique to obtain clear information about bulk states. Here, we describe how HXPES can be conveniently applied to study the interesting subjects on oxide thin films such as the composition dependence and the film thickness dependence of the electronic structures and the interfacial electronic structure of multilayers

  1. Valency and type conversion in CuInSe2 with H2 plasma exposure: A photoemission investigation

    International Nuclear Information System (INIS)

    Nelson, A.J.; Frigo, S.P.; Rosenberg, R.

    1993-01-01

    The effect of H 2 plasma exposure on CuInSe 2 was studied by synchrotron radiation soft-x-ray photoemission spectroscopy. The low-power H 2 plasma was generated with a commercial electron cyclotron resonance plasma source using pure H 2 with the plasma exposure being performed at 200 degree C. In situ photoemission measurements were acquired after each plasma exposure in order to observe changes in the valence-band electronic structure as well as changes in the In 4d and Se 3d core lines. The results were correlated in order to relate changes in surface chemistry to the electronic structure. These measurements indicate that the H 2 plasma exposure type converts the CuInSe 2 surface to an n-type surface as well as converting the In +3 valency state to an In +1 valency state

  2. Simultaneous measurements of photoemission and morphology of various Al alloys during mechanical deformation

    Science.gov (United States)

    Cai, M.; Li, W.; Dickinson, J. T.

    2006-11-01

    We report simultaneous measurements of strain and photoelectron emission from high purity Al (1350), Al-Mg (5052), Al-Mn (3003), Al-Cu (2024), and Al-Mg-Si (6061) alloys under uniaxial tension due to pulsed excimer laser radiation (248nm). The emission of low-energy photoelectrons is sensitive to deformation-induced changes in surface morphology, including the formation of slip lines and slip bands. Alloy composition and surface treatment significantly influence the photoemission during deformation. Surface oxide enhances the signal-to-noise level during photoemission measurement. In the early stage of deformation (strain ⩽0.04), photoemission intensity increases gradually in a nonlinear fashion. While subsequent photoemission increases almost linearly with strain until failure in samples with thin oxide layer (˜31Å), there are two linear segments of photoemission for the samples with oxide of 45Å. The onset of strain localization corresponds to the intersection point of two linear segments, usually at a strain of 0.08-0.20. A constitutive model incorporating microstructure evolution and work hardening during tensile deformation is proposed to qualitatively interpret the growth of the photoemission as a function of strain. Photoemissions from various alloys are interpreted in the light of surface treatment, work function, composition, and microstructural development during deformation.

  3. Extreme regimes of femtosecond photoemission from a copper cathode in a dc electron gun

    Directory of Open Access Journals (Sweden)

    P. L. E. M. Pasmans

    2016-10-01

    Full Text Available The femtosecond photoemission yield from a copper cathode and the emittance of the created electron beams has been studied in a 12  MeV/m, 100 keV dc electron gun over a wide range of laser fluence, from the linear photoemission regime until the onset of image charge limitations and cathode damaging. The measured photoemission curves can be described well with available theory which includes the Schottky effect, second-order photoemission, and image charge limitation. The second-order photoemission can be explained by thermally assisted one-photon photoemission (1PPE and by above-threshold two-photon photoemission (2PPE. Measurements with a fresh cathode suggest that the 2PPE process is dominant. The beam emittance has been measured for the entire range of initial surface charge densities as well. The emittance measurements of space-charge dominated beams can be described well by an envelope equation with generalized perveance. The dc gun produces 0.1 pC bunches with 25 nm rms normalized emittance, corresponding to a normalized brightness usually associated with rf photoguns. In this experimental study the limits of femtosecond photoemission from a copper cathode have been explored and analyzed in great detail, resulting in improved understanding of the underlying mechanisms.

  4. Photoemission electronic states of epitaxially grown magnetite films

    International Nuclear Information System (INIS)

    Zalecki, R.; Kolodziejczyk, A.; Korecki, J.; Spiridis, N.; Zajac, M.; Kozlowski, A.; Kakol, Z.; Antolak, D.

    2007-01-01

    The valence band photoemission spectra of epitaxially grown 300 A single crystalline magnetite films were measured by the angle-resolved ultraviolet photoemission spectroscopy (ARUPS) at 300 K. The samples were grown either on MgO(0 0 1) (B termination) or on (0 0 1) Fe (iron-rich A termination), thus intentionally presenting different surface stoichiometry, i.e. also different surface electronic states. Four main features of the electron photoemission at about -1.0, -3.0, -5.5 and -10.0 eV below a chemical potential show systematic differences for two terminations; this difference depends on the electron outgoing angle. Our studies confirm sensitivity of angle resolved PES technique on subtleties of surface states

  5. Surface and adsorbate structural studies by photoemission in the hν = 50-500 eV range

    International Nuclear Information System (INIS)

    Shirley, D.A.

    1979-08-01

    The present status of photoelectron spectroscopy in the 50-500 eV range is discussed in relation to its application to surface science. Instrumentation aspects of synchrotron radiation sources are reviewed. The direct transition model is shown to be applicable in this range with some limitations. Cooper minima and adsorbate sensitivity enhancement for hν > 100 eV are reviewed. A new effect--condensed phase photoelectron asymmetry--is noted. Finally, photoelectron diffraction - another new effect - is described and evaluated

  6. Simulation and characterization of the crystal growth by photoemission; Simulation et caracterisation de la croissance cristalline par photoemission

    Energy Technology Data Exchange (ETDEWEB)

    Fazouan, N

    1994-05-16

    In this thesis, we argue in favour of photoemission as an in-situ characterization tool for the homo-epitaxial growth of GaAs. The first part, is concerned with the interpretation of the origin of the photoemission oscillations as first observed by J.N. Eckstein and al during MBE growth of GaAs. To study this effect, two approaches have been used. These approaches are based on reaction surface and roughness observations to study the growth mode. They associate the photoemission current with the presence of uncovered gallium adatoms, i.e. those which do not have an arsenic atom above them. The first approach is based on chemical rate theory, whereas the second is based on an atomistic simulation of GaAs homo-epitaxy. This last approach introduces the notion of interlayer migration processes and uses a Monte Carlo technique to look at the temporal evolution of the configuration and hence the morphology. It is shown with these two approaches that the photoemission current has similar characteristics as to those of RHEED, c.g.the same oscillation period. The results obtained have shown the relationship between the photoemission oscillations amplitude and the growth mode which are determined by the mechanisms of absorption and diffusion of gallium atoms and arsenic atoms of molecules. Finally, the study of the effect of the surface reactions shows the importance of these in the case where arsenic is supplied in molecular form (As{sub 2}). The last part concerns the experimental measurements at the threshold photoemission current during epitaxial growth of GaAs by metal-organic vapour phase epitaxy (MOVPE). The objective of this experimental study is to test the good running of the photo-assisted MOVPE low pressure system and to study the possibilities offered by this as an in-situ diagnostic tool for MOVPE. (author). 101 refs., 80 figs., 6 tabs.

  7. Photoemission and low energy electron microscopy study on the formation and nitridation of indium droplets on Si (111)7 × 7 surfaces

    International Nuclear Information System (INIS)

    Qi, B.; Ólafsson, S.; Göthelid, M.; Gislason, H.P.; Agnarsson, B.

    2013-01-01

    The formation and nitridation of indium (In) droplets on Si (111)7 × 7, with regard to In droplet epitaxy growth of InN nanostructures, were studied using a spectroscopic photoemission and low energy electron microscopy, for the In coverages from 0.07 to 2.3 monolayer (ML). The results reveal that the In adatoms formed well-ordered clusters while keeping the Si (111)7 × 7 surface periodicity at 0.07 ML and a single √(3)×√(3) phase at 0.3 ML around 440–470 °C. At 0.82 ML, owing to the presence of structurally defect areas beside the 7 × 7 domains, 3-D In droplets evolved concomitantly with the formation of 4 × 1-In cluster chains, accompanied by a transition in surface electric property from semiconducting to metallic. Further increasing the In to 2.3 ML led to a moderate increase in number density and an appreciable lateral growth of the droplets, as well as the multi-domain In phases. Upon nitridation with NH 3 at ∼ 480 °C, besides the nitridation of the In droplets, the N radicals also dissociated the In-Si bonds to form Si-N. This caused a partial disintegration of the ordered In phase and removal of the In adatoms between the In droplets. - Highlights: ► Formation and nitridation of indium (In) droplets on Si (111) were studied. ► In droplets evolved with the 4 × 1-In cluster chains at 0.82 monolayer (ML). ► In droplets grow in density and lateral size with In coverage increased to 2.3 ML. ► The multi-domain In phases were formed at 2.3 ML. ► Nitridation of In droplets is accompanied by a disintegration of layering In phase

  8. X-ray photo-emission studies of Cu1-xTlxBa2Ca3Cu4O12-y superconductor thin films

    International Nuclear Information System (INIS)

    Khan, Nawazish A.; Mumtaz, M.; Ahadian, M.M.; Iraji-zad, Azam

    2006-01-01

    X-ray photo-emission spectroscopy (XPS) studies of Cu 1-x Tl x Ba 2 Ca 3 Cu 4 O 12-y superconductor thin films have been carried out for understanding the mechanism of superconductivity and to find out the reasons for the increase of zero resistivity critical temperature T c (R = 0) with post-annealing in a nitrogen atmosphere. It is observed from these studies that reduction of charge state of thallium is a source of doping of carriers to the CuO 2 planes. The reduced charge state of thallium (i.e. Tl 1+ ) promotes lower oxygen concentration in the charge reservoir layer, which possibly results in movement of electrons to the conducting CuO 2 planes. The higher density of electrons in the CuO 2 planes optimizes the hole concentration 'n p ' in these planes. The reduced charge state of thallium in the Cu 1-x Tl x Ba 2 O 4-δ charge reservoir layer is also supported by a shift of the Ba 3d 5/2 and Ba 3d 3/2 XPS lines to lower binding energies with post-annealing in nitrogen atmosphere. Moreover, the movement of the valance band spectrum to lower binding energies suggested that the electronic density of states changes in the valance band with the post-annealing in nitrogen, which possibly becomes a source of doping of carriers to the CuO 2 planes. The increased doping of electrons to the CuO 2 planes optimizes the Fermi-vector K F and Fermi-velocity V F of the carriers and increases the T c (R = 0) of final compound

  9. New Developments in Theory of X-ray Photoemission from Solids

    International Nuclear Information System (INIS)

    Fujikawa, Takashi

    2009-01-01

    In this review article we discuss some new developments in photoemission theories. We first discuss basic theoretical framework on the basis of quantum electrodynamics (QED), which allows us to treat radiation field screening from first principle theory. Based on this theoretical framework, recent theoretical developments in x-ray photoemission theories are reviewed, which have rarely been discussed in the previous review articles. Topics selected in this review article are multi-atom resonant photoemission (MARPE), anomalous behavior of the L 23 -edge intensity ratio of 3d transition metals, high-energy photoemission in particular non-dipole effects and recoil exciting phonon around the x-ray absorbing atom, and relativistic and magnetic effects.

  10. 'Reprint of' New Developments in Theory of X-ray Photoemission from Solids

    International Nuclear Information System (INIS)

    Fujikawa, Takashi

    2010-01-01

    In this review article we discuss some new developments in photoemission theories. We first discuss basic theoretical framework on the basis of quantum electrodynamics (QED), which allows us to treat radiation field screening from first principle theory. Based on this theoretical framework, recent theoretical developments in x-ray photoemission theories are reviewed, which have rarely been discussed in the previous review articles. Topics selected in this review article are multi-atom resonant photoemission (MARPE), anomalous behavior of the L 23 -edge intensity ratio of 3d transition metals, high-energy photoemission in particular non-dipole effects and recoil exciting phonon around the x-ray absorbing atom, and relativistic and magnetic effects.

  11. Valence-band and core-level photoemission study of single-crystal Bi2CaSr2Cu2O8 superconductors

    International Nuclear Information System (INIS)

    Shen, Z.; Lindberg, P.A.P.; Wells, B.O.; Mitzi, D.B.; Lindau, I.; Spicer, W.E.; Kapitulnik, A.

    1988-01-01

    High-quality single crystals of Bi 2 CaSr 2 Cu 2 O 8 superconductors have been prepared and cleaved in ultrahigh vacuum. Low-energy electron diffraction measurements show that the surface structure is consistent with the bulk crystal structure. Ultraviolet photoemission and x-ray photoemission experiments were performed on these well-characterized sample surfaces. The valence-band and the core-level spectra obtained from the single-crystal surfaces are in agreement with spectra recorded from polycrystalline samples, justifying earlier results from polycrystalline samples. Cu satellites are observed both in the valence band and Cu 2p core level, signaling the strong correlation among the Cu 3d electrons. The O 1s core-level data exhibit a sharp, single peak at 529-eV binding energy without any clear satellite structures

  12. X-ray photoemission spectroscopy (XPS) study of uranium, neptunium and plutonium oxides in silicate-based glasses

    International Nuclear Information System (INIS)

    Lam, D.J.; Veal, B.W.; Paulikas, A.P.

    1982-11-01

    Using XPS as the principal investigative tool, we are in the process of examining the bonding properties of selected metal oxides added to silicate glass. In this paper, we present results of XPS studies of uranium, neptunium, and plutonium in binary and multicomponent silicate-based glasses. Models are proposed to account for the very diverse bonding properties of 6+ and 4+ actinide ions in the glasses

  13. Florida statewide radiation study

    International Nuclear Information System (INIS)

    Nagda, N.L.; Koontz, M.D.; Fortmann, R.C.; Schoenborn, W.A.; Mehegan, L.L.

    1987-01-01

    Florida phosphate deposits contain higher levels of uranium than most other soils and rocks, thus exposing the population to higher-than-desirable levels of radon and its short-lived daughters. The Florida Legislature ordered a survey of significant land areas where an environmental radiation standard should be applied. Among other things, the study assessed indoor radon in 6,000 homes, soil radon at 3,000 residences, and all data existing prior to the study. The report explains the purpose of the study, how it was designed and conducted, and its results. It concludes with a discussion of radon/radon decay product equilibrium factor, correlation between indoor and soil radon, and preliminary attempts to develop a safe threshold for soil radon below which few elevated indoor levels would be anticipated

  14. The electronic structure of clean and adsorbate-covered Bi2Se3: an angle-resolved photoemission study

    DEFF Research Database (Denmark)

    Bianchi, Marco; Hatch, Richard; Guan, Dandan

    2012-01-01

    Angle-resolved photoelectron spectroscopy is used for a detailed study of the electronic structure of the topological insulator Bi2Se3. Nominally stoichiometric and calcium-doped samples were investigated. The pristine surface shows the topological surface state in the bulk band gap. As time passes....... For a sufficiently strong band bending, additional states appear at the Fermi level. These are interpreted as quantized conduction band states. For large band bendings, these states are found to undergo a strong Rashba splitting. The formation of quantum well states is also observed for the valence band states......, the Dirac point moves to higher binding energies, indicating an increasingly strong downward bending of the bands near the surface. This time-dependent band bending is related to a contamination of the surface and can be accelerated by intentionally exposing the surface to carbon monoxide and other species...

  15. Exploring electronic structure of one-atom thick polycrystalline graphene films: A nano angle resolved photoemission study

    Science.gov (United States)

    Avila, José; Razado, Ivy; Lorcy, Stéphane; Fleurier, Romain; Pichonat, Emmanuelle; Vignaud, Dominique; Wallart, Xavier; Asensio, María C.

    2013-01-01

    The ability to produce large, continuous and defect free films of graphene is presently a major challenge for multiple applications. Even though the scalability of graphene films is closely associated to a manifest polycrystalline character, only a few numbers of experiments have explored so far the electronic structure down to single graphene grains. Here we report a high resolution angle and lateral resolved photoelectron spectroscopy (nano-ARPES) study of one-atom thick graphene films on thin copper foils synthesized by chemical vapor deposition. Our results show the robustness of the Dirac relativistic-like electronic spectrum as a function of the size, shape and orientation of the single-crystal pristine grains in the graphene films investigated. Moreover, by mapping grain by grain the electronic dynamics of this unique Dirac system, we show that the single-grain gap-size is 80% smaller than the multi-grain gap recently reported by classical ARPES. PMID:23942471

  16. Electronic Structure of C60/Zinc Phthalocyanine/V₂O₅ Interfaces Studied Using Photoemission Spectroscopy for Organic Photovoltaic Applications.

    Science.gov (United States)

    Lim, Chang Jin; Park, Min Gyu; Kim, Min Su; Han, Jeong Hwa; Cho, Soohaeng; Cho, Mann-Ho; Yi, Yeonjin; Lee, Hyunbok; Cho, Sang Wan

    2018-02-18

    The interfacial electronic structures of a bilayer of fullerene (C 60 ) and zinc phthalocyanine (ZnPc) grown on vanadium pentoxide (V₂O₅) thin films deposited using radio frequency sputtering under various conditions were studied using X-ray and ultraviolet photoelectron spectroscopy. The energy difference between the highest occupied molecular orbital (HOMO) level of the ZnPc layer and the lowest unoccupied molecular orbital (LUMO) level of the C 60 layer was determined and compared with that grown on an indium tin oxide (ITO) substrate. The energy difference of a heterojunction on all V₂O₅ was found to be 1.3~1.4 eV, while that on ITO was 1.1 eV. This difference could be due to the higher binding energy of the HOMO of ZnPc on V₂O₅ than that on ITO regardless of work functions of the substrates. We also determined the complete energy level diagrams of C 60 /ZnPc on V₂O₅ and ITO.

  17. Angle-resolved photoemission extended fine structure: Multiple layers of emitters and multiple initial states

    International Nuclear Information System (INIS)

    Huff, W.R.A.; Kellar, S.A.; Moler, E.J.; California Univ., Berkeley, CA; Chen, Y.; Wu, H.; Shirley, D.A.; Hussain, Z.

    1995-01-01

    Recently, angle-resolved photoemission extended fine structure (ARPEFS) has been applied to experimental systems involving multiple layers of emitters and non-s core-level photoemission in an effort to broaden the utility of the technique. Most of the previous systems have been comprised of atomic or molecular overlayers adsorbed onto a single-crystal, metal surface and the photoemission data were taken from an s atomic core-level in the overlayer. For such a system, the acquired ARPEFS data is dominated by the p o final state wave backscattering from the substrate atoms and is well understood. In this study, we investigate ARPEFS as a surface-region structure determination technique when applied to experimental systems comprised of multiple layers of photoemitters and arbitrary initial state core-level photoemission. Understanding the data acquired from multiple layers of photoemitters is useful for studying multilayer interfaces, ''buried'' surfaces, and clean crystals in ultra- high vacuum. The ability to apply ARPEFS to arbitrary initial state core-level photoemission obviously opens up many systems to analysis. Efforts have been ongoing to understand such data in depth. We present clean Cu(111) 3s, 3p, and 3d core-level, normal photoemission data taken on a high resolution soft x-ray beamline 9.3.2 at the Advanced Light Source in Berkeley, California and clean Ni(111) 3p normal photoemission data taken at the National Synchrotron Light Source in Upton, New York, USA

  18. Instrument developments for inverse photoemission

    International Nuclear Information System (INIS)

    Brenac, A.

    1987-02-01

    Experimental developments principally concerning electron sources for inverse photoemission are presented. The specifications of the electron beam are derived from experiment requirements, taking into account the limitations encountered (space charge divergence). For a wave vector resolution of 0.2 A -1 , the maximum current is 25 microA at 20 eV. The design of a gun providing such a beam in the range 5 to 50 eV is presented. Angle-resolved inverse photoemission experiments show angular effects at 30 eV. For an energy of 10 eV, angular effects should be stronger, but the low efficiency of the spectrometer in this range makes the experiments difficult. The total energy resolution of 0.3 eV is the result mainly of electron energy spread, as expected. The electron sources are based on field effect electron emission from a cathode consisting of a large number of microtips. The emission arises from a few atomic cells for each tip. The ultimate theoretical energy spread is 0.1 eV. This value is not attained because of an interface resistance problem. A partial solution of this problem allows measurement of an energy spread of 0.9 eV for a current of 100 microA emitted at 60 eV. These cathodes have a further advantage in that emission can occur at a low temperature [fr

  19. Angle-resolved-photoemission study of Bi2Sr2CaCu2O8+δ: Metallicity of the Bi-O plane

    International Nuclear Information System (INIS)

    Wells, B.O.; Shen, Z.; Dessau, D.S.; Spicer, W.E.; Olson, C.G.; Mitzi, D.B.; Kapitulnik, A.; List, R.S.; Arko, A.

    1990-01-01

    We have performed high-resolution angle-resolved-photoemission experiments on Bi 2 Sr 2 CaCu 2 O 8+δ single crystals with different annealing histories. By depositing a small amount of Au on the surface, we were able to distinguish electronic states associated with the Bi-O surface layer. We found that the Bi-O atomic surface layer is metallic and superconducting for samples that were high-temperature annealed in oxygen but not for as-grown samples. The Cu-O plane is found to be superconducting in all samples

  20. Quantification of plasmon excitations in core-level photoemission

    International Nuclear Information System (INIS)

    Yubero, F.; Tougaard, S.

    2005-01-01

    Calculation of photoelectron spectra (PES) based on our previous dielectric response model [A. C. Simonsen et al. Phys. Rev. B 56, 1612 (1997)] for electronic excitations in PES are compared with recently reported experimental data. It is found that the dielectric description of electron energy losses in photoemission reproduces quantitatively the angular dependence of the surface and bulk electron losses observed experimentally for the Al2s photoemission spectra of Al(111), excited with MgKα radiation. The model also allows to calculate the separate intrinsic and extrinsic effects in photoemission. Thus, the extrinsic losses account for more than 95% of the total surface excitations. Regarding the bulk excitations, both extrinsic and intrinsic contributions vary significantly with emission angle. The intrinsic contribution represents ∼35% of the intensity at the bulk plasmon position at normal emission while only 18% at 80 deg. glancing emission. The calculations presented here can easily be used to interpret PES spectra of other materials in terms of intrinsic and extrinsic effects, if their dielectric properties are known

  1. Photoemission for f-electron materials

    International Nuclear Information System (INIS)

    Huang, Youngsea.

    1989-01-01

    The dissertation investigates the interpretation of photoemission from f-electron materials. The authors also discuss unusual room temperature solid-state reactions in Yb-Cu films that they discovered. They show the importance of considering the entire system in the photoemission process and that photoemission actually measures the energy difference between total energies of the initial state and the final excited state of the whole system. They point out misconceptions in the current interpretation of photoemission from mixed valent materials. Their results on Yb-Cu system and other high-resolution photoemission measurements on mixed valent Yb-based materials show that the 4f feature is not pinned at the Fermi level though there is a 4f 14 (6s5d) 2 and 4f 13 (6s5d) 3 configuration degeneracy in the ground state. They suggest that this non-pinning is a general phenomenon due to the fact that the final state is not completely relaxed in the photoemission process. They discuss the current competing models of photoemission from Ce-based materials and show problems with their interpretations. As 4f electrons are more itinerant for Ce and Yb, they give a delocalized-localized kind of interpretation for 4f levels of Ce based materials. They employ the Ce-Yb analogy (electron-hole inversion and thereby an energy scale inversion) with the impurity model to photoemission from Yb-based materials and point out contradictory results on YbAl 3 in the literature. In their results on the Yb-Cu system, where the Yb valence varies from ∼3 to ∼2.2, they do not observe the Kondo resonance within the limits of their experimental resolution. They suggest that to date no Kondo resonance has been observed, and speculate either that the impurity model is inadequate for Yb-based materials or that photoemission is unable to detect a Kondo resonance

  2. Direct surface magnetometry with photoemission magnetic x-ray dichroism

    Energy Technology Data Exchange (ETDEWEB)

    Tobin, J.G.; Goodman, K.W. [Lawrence Berkeley National Lab., CA (United States); Schumann, F.O. [Pennsylvania State Univ., University Park, PA (United States)] [and others

    1997-04-01

    Element specific surface magnetometry remains a central goal of synchrotron radiation based studies of nanomagnetic structures. One appealing possibility is the combination of x-ray absorption dichroism measurements and the theoretical framework provided by the {open_quotes}sum rules.{close_quotes} Unfortunately, sum rule analysis are hampered by several limitations including delocalization of the final state, multi-electronic phenomena and the presence of surface dipoles. An alternative experiment, Magnetic X-Ray Dichroism in Photoelectron Spectroscopy, holds out promise based upon its elemental specificity, surface sensitivity and high resolution. Computational simulations by Tamura et al. demonstrated the relationship between exchange and spin orbit splittings and experimental data of linear and circular dichroisms. Now the authors have developed an analytical framework which allows for the direct extraction of core level exchange splittings from circular and linear dichroic photoemission data. By extending a model initially proposed by Venus, it is possible to show a linear relation between normalized dichroism peaks in the experimental data and the underlying exchange splitting. Since it is reasonable to expect that exchange splittings and magnetic moments track together, this measurement thus becomes a powerful new tool for direct surface magnetometry, without recourse to time consuming and difficult spectral simulations. The theoretical derivation will be supported by high resolution linear and circular dichroism data collected at the Spectromicroscopy Facility of the Advanced Light Source.

  3. Photoemission using femtosecond laser pulses

    International Nuclear Information System (INIS)

    Srinivasan-Rao, T.; Tsang, T.; Fischer, J.

    1991-10-01

    Successful operation of short wavelength FEL requires an electron bunch of current >100 A and normalized emittance < 1 mm-mrad. Recent experiments show that RF guns with photocathodes as the electron source may be the ideal candidate for achieving these parameters. To reduce the emittance growth due to space charge and RF dynamics effects, the gun may have to operate at high field gradient (hence at high RF frequency) and a spot size small compared to the aperture. This may necessitate the laser pulse duration to be in the subpicosecond regime to reduce the energy spread. We will present the behavior of metal photocathodes upon irradiation with femtosecond laser beams, comparison of linear and nonlinear photoemission, and scalability to high currents. Theoretical estimate of the intrinsic emittance at the photocathode in the presence of the anomalous heating of the electrons, and the tolerance on the surface roughness of the cathode material will be discussed

  4. Combination of lasers and synchrotron radiation in studies of atomic photoionization

    International Nuclear Information System (INIS)

    Meyer, M.

    2009-01-01

    Recent experiments using the combination of conventional lasers and synchrotron radiation are presented and discussed. The controlled laser-manipulation of atoms prior to ionization by the synchrotron radiation provides an ideal experimental basis for detailed investigations of atomic photoionization. Due to the recent advances in high-resolution electron spectroscopy, it has become possible to analyze the J-resolved fine structure of the final ionic states in the photoionization of laser-excited atoms enabling thereby the determination of the specific influence of the outer electron to the ionization from inner subshells. Especially, the analysis of photoemission satellites and their relative intensities bring out directly the importance of electron correlations. Furthermore, it is shown through some examples of experiments using linearly and circularly polarized radiations, how the study of magnetic dichroisms in the photoionization opens the access to a complete description of the photoionization process, in particular to the determination of partial photoionization cross-sections.

  5. Angle Resolved Photoemission Spectroscopy Studies of the Mott Insulator to Superconductor Evolution in Ca2-xNaxCuO2Cl2

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Kyle Michael

    2005-09-02

    It is widely believed that many of the exotic physical properties of the high-T{sub c} cuprate superconductors arise from the proximity of these materials to the strongly correlated, antiferromagnetic Mott insulating state. Therefore, one of the fundamental questions in the field of high-temperature superconductivity is to understand the insulator-to-superconductor transition and precisely how the electronic structure of Mott insulator evolves as the first holes are doped into the system. This dissertation presents high-resolution, doping dependent angle-resolved photoemission (ARPES) studies of the cuprate superconductor Ca{sub 2-x}Na{sub x}CuO{sub 2}Cl{sub 2}, spanning from the undoped parent Mott insulator to a high-temperature superconductor with a T{sub c} of 22 K. A phenomenological model is proposed to explain how the spectral lineshape, the quasiparticle band dispersion, and the chemical potential all progress with doping in a logical and self-consistent framework. This model is based on Franck-Condon broadening observed in polaronic systems where strong electron-boson interactions cause the quasiparticle residue, Z, to be vanishingly small. Comparisons of the low-lying states to different electronic states in the valence band strongly suggest that the coupling of the photohole to the lattice (i.e. lattice polaron formation) is the dominant broadening mechanism for the lower Hubbard band states. Combining this polaronic framework with high-resolution ARPES measurements finally provides a resolution to the long-standing controversy over the behavior of the chemical potential in the high-T{sub c} cuprates. This scenario arises from replacing the conventional Fermi liquid quasiparticle interpretation of the features in the Mott insulator by a Franck-Condon model, allowing the reassignment of the position of the quasiparticle pole. As a function of hole doping, the chemical potential shifts smoothly into the valence band while spectral weight is transferred

  6. The impact of inverse photoemission spectroscopy measurements on regioregular poly(3-hexylthiophene) films

    International Nuclear Information System (INIS)

    Li, Zhi; Schlaf, Rudy; Sun, Siqi; Li, Xiao

    2014-01-01

    Inverse photoemission spectroscopy (IPES) enables the characterization of the density of states of unoccupied energy states above the Fermi level. However, due to the relatively high electron currents required to achieve useful signal to noise ratios, sample damage is a concern. Regioregular poly(3-hexylthiophene) (rr-P3HT) was used to systematically study the influence of electron radiation during IPES measurements on a prototypical conductive polymer. A series of IPES measurements exposing the samples to a range of electron fluxes was performed. An analysis of the electronic structure and the morphology showed that significant changes occurred in the investigated samples depending on the electron flux. X-ray diffraction results revealed that the root cause of the spectral changes is most likely related to crystallization of the film in an edge-on orientation. This was confirmed by Raman spectroscopy where both the C-C and C=C stretch modes shifted to lower frequencies after 5 IPES scans indicating a more ordered molecular structure. The observation of these stretch modes even after exposure to higher electron flux indicates that the main chemical structure of the P3HT molecules remains mostly intact during the IPES measurements. The absence of significant changes in C 1s and S 2p photoemission core level lines also confirmed this conclusion

  7. Coherent and incoherent processes in resonant photoemission

    Energy Technology Data Exchange (ETDEWEB)

    Magnuson, M.; Karis, O.; Weinelt, M. [Uppsala Univ. (Sweden)] [and others

    1997-04-01

    In this contribution the authors present the distinction between coherent and incoherent processes in resonant photoemission. As a first step they determine whether an autoionization process is photoemission-like or Auger-like. The discussion is based on measurements for a weakly bonded adsorption system, Ar/Pt(111). This type of system is well adapted to investigate these effects since it yields distinctly shifted spectral features depending on the nature of the process. After this, the question of resonance photoemission in metallic systems is addressed. This is done in connection with measurements at the 2p edges for Ni metal. Ni has been one of the prototype systems for resonant photoemission. The resonances have been discussed in connection with the strong correlation and d-band localization effects in this system. Based on the results some general comments about the appearance of resonant effects in metallic systems are made.

  8. Zen and the art of dichroic photoemission

    Energy Technology Data Exchange (ETDEWEB)

    Laan, Gerrit van der, E-mail: gerrit.vanderlaan@diamond.ac.uk

    2015-04-15

    Highlights: • General theory for angle and spin dependence of dichroic core-level photoemission. • Fundamental spectra give correlation between spin and orbital moments. • Interference term between emission channels results in MLDAD and CDAD. • Core-hole polarization is probed by resonant photoemission. - Abstract: The discovery of magnetic dichroism in photoemission is celebrating its 25th anniversary this year. Here a review of the underlying general theory for the angular and spin dependence of dichroic core-level photoemission is presented using both a single-particle model and a many-body approach. The established methods of angular momentum coupling offer an elegant and powerful way to analyse the magnetic dichroism and spin polarization in photoemission from core and localized valence levels. In the presence of core-valence interactions one can distinguish different fundamental spectra, which via sum rules are related to physical properties described by coupled tensor operators for spin and orbital moments. By separating the angular dependence from the physical information, different geometries can be distinguished to measure the magnetic circular dichroism (MCD), linear dichroism (LD), circular dichroism in the angular dependence (CDAD), and magnetic linear dichroism in the angular dependence (MLDAD). Various ways to probe the core-hole polarization are discussed, such as using the angular dependence, moment analysis of the spectral distribution, and resonant photoemission decay.

  9. Development of high current electron source using photoemission from metals with ultrashort laser pulses

    International Nuclear Information System (INIS)

    Tsang, T.; Srinivasan-Rao, T.; Fischer, J.

    1990-10-01

    We summarize the studies of photoemission from metal photocathodes using picosecond pulses in the UV (4.66 eV) wavelength and femtosecond laser pulses in the visible (2 eV) wavelengths. To achieve high current density yield from metal photocathodes, multiphoton photoemission using femtosecond laser pulses are suggested. Electron yield improvement incorporating surface photoemission and surface plasmon resonance in metals and metal films are demonstrated. We examine the possibility of the nonlinear photoemission process overtaking the linear process, and identity some possible complexity. To extract the large amount of electrons free of space charge, a pulsed high voltage is designed; the results of the preliminary test are presented. Finally, for the first time, the width of the electron temporal profiles are measured, utilizing the nonlinear photoelectric effect, to below 100 fsec time regime. The results indicated that the electron pulse duration follows the laser pulses and are not limited by the material. 8 refs., 15 figs

  10. Quantitative analysis of valence photoemission spectra and quasiparticle excitations at chromophore-semiconductor interfaces.

    Science.gov (United States)

    Patrick, Christopher E; Giustino, Feliciano

    2012-09-14

    Investigating quasiparticle excitations of molecules on surfaces through photoemission spectroscopy forms a major part of nanotechnology research. Resolving spectral features at these interfaces requires a comprehensive theory of electron removal and addition processes in molecules and solids which captures the complex interplay of image charges, thermal effects, and configurational disorder. Here, we develop such a theory and calculate the quasiparticle energy-level alignment and the valence photoemission spectrum for the prototype biomimetic solar cell interface between anatase TiO(2) and the N3 chromophore. By directly matching our calculated photoemission spectrum to experimental data, we clarify the atomistic origin of the chromophore peak at low binding energy. This case study sets a new standard in the interpretation of photoemission spectroscopy at complex chromophore-semiconductor interfaces.

  11. Effects of strain on the electronic structure, superconductivity, and nematicity in FeSe studied by angle-resolved photoemission spectroscopy

    Science.gov (United States)

    Phan, G. N.; Nakayama, K.; Sugawara, K.; Sato, T.; Urata, T.; Tanabe, Y.; Tanigaki, K.; Nabeshima, F.; Imai, Y.; Maeda, A.; Takahashi, T.

    2017-06-01

    One of central issues in iron-based superconductors is the role of structural change to the superconducting transition temperature (Tc). It was found in FeSe that the lattice strain leads to a drastic increase in Tc, accompanied by suppression of nematic order. By angle-resolved photoemission spectroscopy on tensile- or compressive-strained and strain-free FeSe, we experimentally show that the in-plane strain causes a marked change in the energy overlap (Δ Eh -e ) between the hole and electron pockets in the normal state. The change in Δ Eh -e modifies the Fermi-surface volume, leading to a change in Tc. Furthermore, the strength of nematicity is also found to be characterized by Δ Eh -e . These results suggest that the key to understanding the phase diagram is the fermiology and interactions linked to the semimetallic band overlap.

  12. New type of in-gap states at a spinel/perovskite interface: combined resonant soft x-ray photoemission spectroscopy and first-principles study.

    Science.gov (United States)

    Borisov, Vladislav; Schuetz, Philipp; Pfaff, Florian; Scheiderer, Philipp; Dudy, Lenart; Zapf, Michael; Gabel, Judith; Christensen, Dennis Valbjorn; Chen, Yunzhong; Pryds, Nini; Strocov, Vladimir; Rogalev, Victor; Schlueter, Christoph; Lee, Tien-Lin; Jeschke, Harald O.; Valenti, Roser; Sing, Michael; Claessen, Ralph

    Oxygen vacancies in oxide heterostructures create a plethora of electronic phenomena not observed in the stoichiometric systems. In this talk we will discuss the presence of a new type of in-gap states at the spinel/perovskite γ-Al2O3/SrTiO3 interface, as observed in soft x-ray resonant photoemission spectroscopy. Based on ab initio calculations and crystal-field analysis of different atomic environments, we identify the origin of this behavior and we argue on the possible origin of the extraordinarily high electron mobility measured in this heterostructure. This work was financially supported by the Deutsche Forschungsgemeinschaft SFB/TR 49 and SFB 1170.

  13. High-resolution photoemission study of Ce1-x La x RhAs: A collapse of the energy gap in the Kondo semiconductor

    International Nuclear Information System (INIS)

    Shimada, K.; Higashiguchi, M.; Fujimori, S.-I.; Saitoh, Y.; Fujimori, A.; Namatame, H.; Taniguchi, M.; Sasakawa, T.; Takabatake, T.

    2006-01-01

    High-resolution resonance-photoemission spectroscopy has been performed on the Ce 1- x La x RhAs (0≤x≤0.05) single crystal to elucidate a collapse of the energy gap in the Kondo semiconductor CeRhAs by La substitution. With increasing x, the spectral intensity of the Ce4f 1 derived states near the Fermi level decreases and new 4f derived spectral feature appears at a higher binding energy. The Rh4d-derived states, on the other hand, are not significantly changed by the substitution. New 4f-derived states have incoherent nature, which is responsible for the collapse of the semiconducting state for x>∼0.02

  14. Studying uses of radiation

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1969-07-01

    Among the events this year which have demonstrated the efforts of the Agency and the Food and Agriculture Organization of the United Nations to increase the knowledge of nuclear techniques have been two six-week courses held in association with national atomic energy organizations. In Italy the use of radiation to induce beneficial mutations in plans was the subject, and in India stress was on ways of preserving food, in addition to the sterilization of biomedical products. (author)

  15. Polarity effects in the x-ray photoemission of ZnO and other wurtzite semiconductors

    International Nuclear Information System (INIS)

    Allen, M. W.; Zemlyanov, D. Y.; Waterhouse, G. I. N.; Metson, J. B.; Veal, T. D.; McConville, C. F.; Durbin, S. M.

    2011-01-01

    Significant polarity-related effects were observed in the near-surface atomic composition and valence band electronic structure of ZnO single crystals, investigated by x-ray photoemission spectroscopy using both Al K α (1486.6 eV) and synchrotron radiation (150 to 1486 eV). In particular, photoemission from the lowest binding energy valence band states was found to be significantly more intense on the Zn-polar face compared to the O-polar face. This is a consistent effect that can be used as a simple, nondestructive indicator of crystallographic polarity in ZnO and other wurtzite semiconductors.

  16. Calculations of Photoemission from Rutile

    Science.gov (United States)

    Hjalmarson, Harold; Schultz, Peter; Moore, Chris

    2015-03-01

    Photoemission is a well-known mechanism for release of electrons from a surface during electrical breakdown of a gas such as air. During air breakdown, UV photons, which are emitted from the highly excited gas molecules, are absorbed in the surfaces such as the cathode and the anode. These absorbed photons create energetic electrons, and a small portion of these electrons reach the surface. Those that overcome the potential energy barrier at the surface tend to be emitted. In this talk, the Boltzmann equation that describes these phenomena is formulated. A Monte Carlo probabilistic method is used to obtain the rate of electron emission as a function of photon energy. The role of bandstructure effects will be discussed. This bandstructure information is obtained by using a density-functional theory (DFT) method. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  17. Simple theoretical analysis of the photoemission from quantum confined effective mass superlattices of optoelectronic materials

    Directory of Open Access Journals (Sweden)

    Debashis De

    2011-07-01

    Full Text Available The photoemission from quantum wires and dots of effective mass superlattices of optoelectronic materials was investigated on the basis of newly formulated electron energy spectra, in the presence of external light waves, which controls the transport properties of ultra-small electronic devices under intense radiation. The effect of magnetic quantization on the photoemission from the aforementioned superlattices, together with quantum well superlattices under magnetic quantization, has also been investigated in this regard. It appears, taking HgTe/Hg1−xCdxTe and InxGa1−xAs/InP effective mass superlattices, that the photoemission from these quantized structures is enhanced with increasing photon energy in quantized steps and shows oscillatory dependences with the increasing carrier concentration. In addition, the photoemission decreases with increasing light intensity and wavelength as well as with increasing thickness exhibiting oscillatory spikes. The strong dependence of the photoemission on the light intensity reflects the direct signature of light waves on the carrier energy spectra. The content of this paper finds six different applications in the fields of low dimensional systems in general.

  18. Low-temperature catalyst activator: mechanism of dense carbon nanotube forest growth studied using synchrotron radiation

    Directory of Open Access Journals (Sweden)

    Akito Takashima

    2014-07-01

    Full Text Available The mechanism of the one-order-of-magnitude increase in the density of vertically aligned carbon nanotubes (CNTs achieved by a recently developed thermal chemical vapor deposition process was studied using synchrotron radiation spectroscopic techniques. In the developed process, a Ti film is used as the underlayer for an Fe catalyst film. A characteristic point of this process is that C2H2 feeding for the catalyst starts at a low temperature of 450°C, whereas conventional feeding temperatures are ∼800°C. Photoemission spectroscopy using soft and hard X-rays revealed that the Ti underlayer reduced the initially oxidized Fe layer at 450°C. A photoemission intensity analysis also suggested that the oxidized Ti layer at 450°C behaved as a support for nanoparticle formation of the reduced Fe, which is required for dense CNT growth. In fact, a CNT growth experiment, where the catalyst chemical state was monitored in situ by X-ray absorption spectroscopy, showed that the reduced Fe yielded a CNT forest at 450°C. Contrarily, an Fe layer without the Ti underlayer did not yield such a CNT forest at 450°C. Photoemission electron microscopy showed that catalyst annealing at the conventional feeding temperature of 800°C caused excess catalyst agglomeration, which should lead to sparse CNTs. In conclusion, in the developed growth process, the low-temperature catalyst activation by the Ti underlayer before the excess Fe agglomeration realised the CNT densification.

  19. Study on radiation hazard

    International Nuclear Information System (INIS)

    Yang, Rong-Chan

    1981-01-01

    A series of experiments were designed to know the influence of the teeth on the radiation hazard for mandible. The right mandible of adult dogs were irradiated by means of an x-radiation generator (total dose was 3000 R and 6000 R). Radiation hazards for the soft tissue revealed a significant difference between the dentulous and edentulous mandibles, macroscopically. The gingiva of irradiated dentulous mandible showed an ulceration after the irradiation. Necrosis of the alveolar mucosa, buccal mucosa and skin followed an ulceration, and eventually exposure of the alveolar bone of mandible occurred. The pathologic condition progressed rapidly and a loosening and an exfoliation of the teeth or a pathologic fracture of the mandible occurred eventually. In the edentulous mandible (6000 R irradiated group) an ulceration of the skin developed as the first disturbance. The tissue necrosis progressed from the skin to the buccal mucosa and gingiva. Eventually an exposure of the alveolar bone occurred but no pathologic fracture was seen in the edentulous mandible. No specific pathologic findings were seen in the 3000 R irradiated edentulous mandible. The early roentgenological findings in the irradiated dentulous mandible were resorption of the alveolar crest and widening of the periodontal membrane space. Another changes of bone were osteoporosis and cortical bone destruction. In the edentulous mandible (6000 R irradiated group) pathologic bone condition occurred later than in the dentulous mandible, and osteosclerosis and cortical bone destruction were also seen. Periosteal reaction was found roentgenologically in the 6000 R irradiated dentulous and edentulous mandibles. No roentgenological findings were seen in the 3000 R irradiated edentulous mandible. (J.P.N.)

  20. X-ray photoemission electron microscopy, a tool for the investigation of complex magnetic structures

    International Nuclear Information System (INIS)

    Scholl, Andreas; Ohldag, Hendrik; Nolting, Frithjof; Stohr, Joachim; Padmore, Howard A.

    2001-01-01

    X-ray Photoemission Electron Microscopy unites the chemical specificity and magnetic sensitivity of soft x-ray absorption techniques with the high spatial resolution of electron microscopy. The discussed instrument possesses a spatial resolution of better than 50 nm and is located at a bending magnet beamline at the Advanced Light Source, providing linearly and circularly polarized radiation between 250 and 1300 eV. We will present examples which demonstrate the power of this technique applied to problems in the field of thin film magnetism. The chemical and elemental specificity is of particular importance for the study of magnetic exchange coupling because it allows separating the signal of the different layers and interfaces in complex multi-layered structures

  1. Photoemission from valence bands of transition metal-phthalocyanines

    International Nuclear Information System (INIS)

    Shang, Ming-Hui; Nagaosa, Mayumi; Nagamatsu, Shin-ichi; Hosoumi, Shunsuke; Kera, Satoshi; Fujikawa, Takashi; Ueno, Nobuo

    2011-01-01

    Research highlights: → The HOMO mainly comes from the carbon atoms of Pc rings and the central metal atoms almost have no contribution on the highest occupied molecular orbital (HOMO: a 1u ) distribution of CoPc as well as NiPc. → Influence by central metal atom on the photoemission intensities from the HOMO of two single molecule systems is negligible for the major. → The modification of the distribution for π-orbital upon adsorption as well as the scattering effects of the central metal on the photoemission intensities are negligible for the major. - Abstract: Angular dependencies of ultraviolet photoelectron spectrum of transition metal-phthalocyanines (TM-Pcs), NiPc and CoPc, have been studied by using multiple-scattering theory to explore the electronic structure of the organometallic complexes influenced by central metal atom. The calculated angular distributions of photoelectrons for the highest occupied molecular orbital (HOMO: a 1u ) from the two single systems are nearly the same and represent well the experimental results obtained for the well-ordered monolayer on the highly oriented pyrolytic graphite substrate. The central metal atoms almost have no contribution on the HOMO distribution, which mainly comes from the carbon atoms of Pc ring. Moreover, the modification of the distribution for π orbital upon adsorption as well as the scattering effects of the central metal on the photoemission intensities are negligible for the major.

  2. Bulk sensitive hard x-ray photoemission electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Patt, M., E-mail: m.patt@fz-juelich.de; Wiemann, C. [Peter Grünberg Institute (PGI-6) and JARA-FIT, Research Center Jülich, D-52425 Jülich (Germany); Weber, N.; Escher, M.; Merkel, M. [Focus GmbH, Neukirchner Str. 2, D-65510 Hünstetten (Germany); Gloskovskii, A.; Drube, W. [DESY Photon Science, Deutsches Elektronen-Synchrotron, D-22603 Hamburg (Germany); Schneider, C. M. [Peter Grünberg Institute (PGI-6) and JARA-FIT, Research Center Jülich, D-52425 Jülich (Germany); Fakultät f. Physik and Center for Nanointegration Duisburg-Essen (CeNIDE), Universität Duisburg-Essen, D-47048 Duisburg (Germany)

    2014-11-15

    Hard x-ray photoelectron spectroscopy (HAXPES) has now matured into a well-established technique as a bulk sensitive probe of the electronic structure due to the larger escape depth of the highly energetic electrons. In order to enable HAXPES studies with high lateral resolution, we have set up a dedicated energy-filtered hard x-ray photoemission electron microscope (HAXPEEM) working with electron kinetic energies up to 10 keV. It is based on the NanoESCA design and also preserves the performance of the instrument in the low and medium energy range. In this way, spectromicroscopy can be performed from threshold to hard x-ray photoemission. The high potential of the HAXPEEM approach for the investigation of buried layers and structures has been shown already on a layered and structured SrTiO{sub 3} sample. Here, we present results of experiments with test structures to elaborate the imaging and spectroscopic performance of the instrument and show the capabilities of the method to image bulk properties. Additionally, we introduce a method to determine the effective attenuation length of photoelectrons in a direct photoemission experiment.

  3. A fermi liquid electric structure and the nature of the carriers in high-T/sub c/ cuprates: A photoemission study

    Energy Technology Data Exchange (ETDEWEB)

    Arko, A.J.; List, R.S.; Bartlett, R.J.; Cheong, S.W.; Fisk, Z.; Thompson, J.D.; Olson, C.G.; Yang, A.B.; Liu, R.; Gu, C.; Veal, B.W.; Liu, J.Z.; Paulikas, A.P.; Vandervoort, K.; Claus, H.; Campuzano, J.C.; Schirber, J.E.; Shinn, N.D.

    1989-01-01

    We have performed angle-integrated and angle-resolved photoemission measurements at 20 K on well-characterized single crystals of high-T/sub c/ cuprates (both 1:2:3-type and 2:2:1:2-type) cleaved in situ, and find a relatively large, resolution limited Fermi edge which shows large amplitude variations with photon energy, indicative of band structure final state effects. The lineshapes of the spectra of the 1:2:3 materials as a function of photon energy are well reproduced by band structure predictions, indicating a correct mix of 2p and 3d orbitals on the calculations, while the energy positions of the peaks agree with calculated bands only to within /approx/0.5 eV. This may yet prove to reflect the effects of Coulomb correlation. We nevertheless conclude that a Fermi liquid approach to conductivity is appropriate. Angle-resolved data, while still incomplete, suggest agreement with the Fermi surface predicted by the LDA calculations. A BCS-like energy gap is observed in the 2:2:1:2 materials, whose magnitude is twice the weak coupling BCS value (i.e., 2/Delta/ = 7 KT/sub c/). 49 refs., 11 figs.

  4. Photoemission Studies of Si Quantum Dots with Ge Core: Dots formation, Intermixing at Si-clad/Ge-core interface and Quantum Confinement Effect

    Directory of Open Access Journals (Sweden)

    Yudi Darma

    2008-03-01

    Full Text Available Spherical Si nanocrystallites with Ge core (~20nm in average dot diameter have been prepared by controlling selective growth conditions of low-pressure chemical vapor deposition (LPCVD on ultrathin SiO2 using alternately pure SiH4 and 5% GeH4 diluted with He. XPS results confirm the highly selective growth of Ge on the pregrown Si dots and subsequently complete coverage by Si selective growth on Ge/Si dots. Compositional mixing and the crystallinity of Si dots with Ge core as a function of annealing temperature in the range of 550-800oC has been evaluated by XPS analysis and confirms the diffusion of Ge atoms from Ge core towards the Si clad accompanied by formation of GeOx at the Si clad surface. The first subband energy at the valence band of Si dot with Ge core has been measured as an energy shift at the top of the valence band density of state using XPS. The systematic shift of the valence band maximum towards higher binding energy with progressive deposition in the dot formation indicate the charging effect of dots and SiO2 layer by photoemission during measurements.

  5. Theoretical and experimental study of resonant 3d X-ray photoemission and resonant L3M45M45 Auger transition of PdO

    International Nuclear Information System (INIS)

    Uozumi, Takayuki; Kotani, Akio

    2000-01-01

    The observed 3d X-ray photoemission spectra (XPS), resonant 3dXPS (RXPS) at the L 3 edge and resonant L 3 M 45 M 45 Auger electron spectra (RAES) of 4d transition metal oxide PdO are successfully analyzed by means of an impurity Anderson model. The importance of Pd 4d-O 2p hybridization effect is especially emphasized in the interpretation of observed spectra. It causes charge transfer satellites in 3dXPS and L 3 M 45 M 45 RAES and mainly determines the structure of resonance enhancements in 3dRXPS. From the analysis of spectra, 4d-2p charge transfer energy Δ, 4d correlation energy U dd and 4d-2p transfer integral pdσ are estimated to be 5.5 eV, 4.5 eV and 2.1 eV, respectively. The character of the insulating energy gap PdO is also theoretically investigated: PdO is classified as an intermediate-type insulator due to the strong 4d-2p hybridization. (author)

  6. Hard x-ray photoemission study of the temperature-induced valence transition system EuNi2(Si1-xGex) 2

    Science.gov (United States)

    Ichiki, Katsuya; Mimura, Kojiro; Anzai, Hiroaki; Uozumi, Takayuki; Sato, Hitoshi; Utsumi, Yuki; Ueda, Shigenori; Mitsuda, Akihiro; Wada, Hirofumi; Taguchi, Yukihiro; Shimada, Kenya; Namatame, Hirofumi; Taniguchi, Masaki

    2017-07-01

    We investigated the bulk-derived electronic structure of the temperature-induced valence transition system EuNi2(Si1 -xGex )2 (x =0.70 , 0.79, and 0.82) by means of hard x-ray photoemission spectroscopy (HAXPES). The HAXPES spectra clearly show distinct temperature dependencies in the spectral intensities of the Eu2 + and Eu3 +3 d components. For x =0.70 , the changes in the Eu2 + and Eu3 +3 d spectral components with temperature reflect a continuous valence transition, whereas the sudden changes for x =0.79 and 0.82 reflect first-order valence transitions. The Eu 3 d spectral shapes for all x and particularly the drastic changes in the Eu3 +3 d feature with temperature are validated by a theoretical calculation based on the single-impurity Anderson model (SIAM). SIAM analysis reveals that the valence transition for each x is controlled by the c -f hybridization strength and the charge-transfer energy. Furthermore, the c -f hybridization strength governs the valence transition of this system, which is either first order or continuous, consistent with Kondo volume collapse.

  7. Fermi liquid character in the photoemission/inverse photoemission spectra of highly correlated electron systems

    International Nuclear Information System (INIS)

    Riseborough, P.S.

    1990-01-01

    We calculate the photoemission/inverse photoemission spectrum for an N-fold degenerate Hubbard model, in the 1/N approximation. The spectra are broadened, and for sufficiently large Coulomb interaction strengths the spectra show satellites both in the photoemission and the brehmstrahlung isochromat spectroscopy portions of the spectra. The intensity of the spectra at the fermi level are equal to the noninteracting values, in accordance with Luttinger's theorem. We show that this can result in a temperature-dependent peak at the Fermi level; the width of the peak is governed by the quasi-particle lifetime. We relate the temperature dependent peak to the Fermi-liquid properties

  8. Experimental radiation carcinogenesis is studies at NIRS

    International Nuclear Information System (INIS)

    Sado, Toshihiko

    1992-01-01

    Experimental radiation carcinogenesis studies conducted during the past decade at NIRS are briefly reviewed. They include the following: 1) Age dependency of susceptibility to radiation carcinogenesis. 2) Radiation-induced myeloid leukemia. 3) Mechanism of fractionated X-irradiation (FX) induced thymic lymphomas. 4) Significance of radiation-induced immunosuppression in radiation carcinogenesis in vivo. 5) Other ongoing studies. (author)

  9. Immunohistological studies in radiation proctitis

    International Nuclear Information System (INIS)

    Honke, Yoshifumi; Katsuta, Shizutomo; Haruma, Ken

    1985-01-01

    Immunohistological studies of radiation proctitis were performed in comparison with those in control subjects, with special reference to the number of immunoglobulin bearing cells in the rectal mucosa. The results obtained were as follows: 1) The rates of distribution of immunoglobulin bearing cells were 16.9% in IgG, 71.7% in IgA, and 11.4% in IgM in control subjects. 2) The number of IgG bearing cells in acute and late radiation proctitis markedly decreased in comparison with those in control subjects. 3) The number of IgA bearing cells in the patients with acute radiation proctitis decreased slightly and recovere 1 in late phase. 4) The number of IgM bearing cells markedly decreased in 11 Gy to 30 Gy radiation group with acute phase. 5) No significant difference could be found in the number of immunoglobulin bearing cells in late radiation proctitis with and without rectal bleeding. 6) Serum immunoglobulin levels of patients with acute radiation proctitis decreased and were well correlated with change the number of immunoglobulin bearing cells. (author)

  10. A photoemission study of the effectiveness of nickel, manganese, and cobalt based corrosion barriers for silicon photo-anodes during water oxidation

    Energy Technology Data Exchange (ETDEWEB)

    O' Connor, Robert; Bogan, Justin; McCoy, Anthony; Byrne, Conor; Hughes, Greg [School of Physical Sciences, Dublin City University, Dublin 9 (Ireland)

    2016-05-21

    Silicon is an attractive material for solar water splitting applications due to its abundance and its capacity to absorb a large fraction of incident solar radiation. However, it has not received as much attention as other materials due to its tendency to oxidize very quickly in aqueous environments, particularly when it is employed as the anode where it drives the oxygen evolution reaction. In recent years, several works have appeared in the literature examining the suitability of thin transition metal oxide films grown on top of the silicon to act as a corrosion barrier. The film should be transparent to solar radiation, allow hole transport from the silicon surface to the electrolyte, and stop the diffusion of oxygen from the electrolyte back to the silicon. In this work, we compare Mn-oxide, Co-oxide, and Ni-oxide thin films grown using physical vapor deposition in order to evaluate which material offers the best combination of photocurrent and corrosion protection. In addition to the electrochemical data, we also present a detailed before-and-after study of the surface chemistry of the films using x-ray photoelectron spectroscopy. This approach allows for a comprehensive analysis of the mechanisms by which the corrosion barriers protect the underlying silicon, and how they degrade during the water oxidation reaction.

  11. A New Spin on Photoemission Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Jozwiak, Chris [Univ. of California, Berkeley, CA (United States)

    2008-12-01

    The electronic spin degree of freedom is of general fundamental importance to all matter. Understanding its complex roles and behavior in the solid state, particularly in highly correlated and magnetic materials, has grown increasingly desirable as technology demands advanced devices and materials based on ever stricter comprehension and control of the electron spin. However, direct and efficient spin dependent probes of electronic structure are currently lacking. Angle Resolved Photoemission Spectroscopy (ARPES) has become one of the most successful experimental tools for elucidating solid state electronic structures, bolstered by-continual breakthroughs in efficient instrumentation. In contrast, spin-resolved photoemission spectroscopy has lagged behind due to a lack of similar instrumental advances. The power of photoemission spectroscopy and the pertinence of electronic spin in the current research climate combine to make breakthroughs in Spin and Angle Resolved Photoemission Spectroscopy (SARPES) a high priority . This thesis details the development of a unique instrument for efficient SARPES and represents a radical departure from conventional methods. A custom designed spin polarimeter based on low energy exchange scattering is developed, with projected efficiency gains of two orders of magnitude over current state-of-the-art polarimeters. For energy analysis, the popular hemispherical analyzer is eschewed for a custom Time-of-Flight (TOF) analyzer offering an additional order of magnitude gain in efficiency. The combined instrument signifies the breakthrough needed to perform the high resolution SARPES experiments necessary for untangling the complex spin-dependent electronic structures central to today's condensed matter physics.

  12. Direct angle resolved photoemission spectroscopy and ...

    Indian Academy of Sciences (India)

    Since 1997 we systematically perform direct angle resolved photoemission spectroscopy (ARPES) on in-situ grown thin (< 30 nm) cuprate films. Specifically, we probe low-energy electronic structure and properties of high-c superconductors (HTSC) under different degrees of epitaxial (compressive vs. tensile) strain.

  13. Parametric studies on automotive radiators

    International Nuclear Information System (INIS)

    Oliet, C.; Oliva, A.; Castro, J.; Perez-Segarra, C.D.

    2007-01-01

    This paper presents a set of parametric studies performed on automotive radiators by means of a detailed rating and design heat exchanger model developed by the authors. This numerical tool has been previously verified and validated using a wide experimental data bank. A first part of the analysis focuses on the influence of working conditions on both fluids (mass flows, inlet temperatures) and the impact of the selected coolant fluid. Following these studies, the influence of some geometrical parameters is analysed (fin pitch, louver angle) as well as the importance of coolant flow lay-out on the radiator global performance. This work provides an overall behaviour report of automobile radiators working at usual range of operating conditions, while significant knowledge-based design conclusions have also been reported. The results show the utility of this numerical model as a rating and design tool for heat exchangers manufacturers, being a reasonable compromise between classic ε - NTU methods and CFD

  14. Theory of pump–probe ultrafast photoemission and X-ray absorption spectra

    Energy Technology Data Exchange (ETDEWEB)

    Fujikawa, Takashi, E-mail: tfujikawa@faculty.chiba-u.jp; Niki, Kaori

    2016-01-15

    Highlights: • Pump–probe ultrafast XAFS and XPS spectra are theoretically studied. • Keldysh Green's function theory is applied. • Important many-body effects are explicitly included. - Abstract: Keldysh Green's function approach is extensively used in order to derive practical formulas to analyze pump–probe ultrafast photoemission and X-ray absorption spectra. Here the pump pulse is strong enough whereas the probe X-ray pulse can be treated by use of a perturbation theory. We expand full Green's function in terms of renormalized Green's function without the interaction between electrons and probe pulse. The present theoretical formulas allow us to handle the intrinsic and extrinsic losses, and furthermore resonant effects in X-ray Absorption Fine Structures (XAFS). To understand the radiation field screening in XPS spectra, we have to use more sophisticated theoretical approach. In the ultrafast XPS and XAFS analyses the intrinsic and extrinsic loss effects can interfere as well. In the XAFS studies careful analyses are necessary to handle extrinsic losses in terms of damped photoelectron propagation. The nonequilibrium dynamics after the pump pulse irradiation is well described by use of the time-dependent Dyson orbitals. Well above the edge threshold, ultrafast photoelectron diffraction and extended X-ray absorption fine structure (EXAFS) provide us with transient structural change after the laser pump excitations. In addition to these slow processes, the rapid oscillation in time plays an important role related to pump electronic excitations. Near threshold detailed information could be obtained for the combined electronic and structural dynamics. In particular high-energy photoemission and EXAFS are not so influenced by the details of excited states by pump pulse. Random-Phase Approximation (RPA)-boson approach is introduced to derive some practical formulas for time-dependent intrinsic amplitudes.

  15. Surface type conversion of CuInSe2 with H2S plasma exposure: A photoemission investigation

    International Nuclear Information System (INIS)

    Nelson, A.J.; Frigo, S.P.; Rosenberg, R.

    1995-01-01

    Surface type conversion of CuInSe 2 by H 2 S plasma exposure was studied by synchrotron radiation soft x-ray photoemission spectroscopy. The low power H 2 S plasma was generated with a commercial electron cyclotron resonance plasma source using pure H 2 S with the plasma exposure being performed at 400 degree C. In situ photoemission measurements were acquired after each plasma exposure in order to observe changes in the valence band electronic structure as well as changes in the In 4d and Se 3d core lines. The results were correlated in order to relate changes in surface chemistry to the electronic structure. These measurements indicate that the H 2 S plasma exposure type converts the n-type CuInSe 2 surface to a p-type surface at this elevated temperature and that the magnitude of the band bending is 0.5 eV, resulting in a homojunction interface. copyright 1995 American Vacuum Society

  16. Workstations studies and radiation protection

    International Nuclear Information System (INIS)

    Lahaye, T.; Donadille, L.; Rehel, J.L.; Paquet, F.; Beneli, C.; Cordoliani, Y.S.; Vrigneaud, J.M.; Gauron, C.; Petrequin, A.; Frison, D.; Jeannin, B.; Charles, D.; Carballeda, G.; Crouail, P.; Valot, C.

    2006-01-01

    This day on the workstations studies for the workers follow-up, was organised by the research and health section. Devoted to the company doctors, for the competent persons in radiation protection, for the engineers of safety, it presented examples of methodologies and applications in the medical, industrial domain and the research, so contributing to a better understanding and an application of regulatory measures. The analysis of the workstation has to allow a reduction of the exposures and the risks and lead to the optimization of the medical follow-up. The agenda of this day included the different subjects as follow: evolution of the regulation in matter of demarcation of the regulated zones where the measures of workers protection are strengthened; presentation of the I.R.S.N. guide of help to the realization of a workstation study; implementation of a workstation study: case of radiology; the workstation studies in the research area; Is it necessary to impose the operational dosimetry in the services of radiodiagnostic? The experience feedback of a competent person in radiation protection (P.C.R.) in a hospital environment; radiation protection: elaboration of a good practices guide in medical field; the activities file in nuclear power plant: an evaluation tool of risks for the prevention. Methodological presentation and examples; insulated workstation study; the experience feedback of a provider; Contribution of the ergonomics to the determiners characterization in the ionizing radiation exposure situations;The workstations studies for the internal contamination in the fuel cycle facilities and the consideration of the results in the medical follow-up; R.E.L.I.R. necessity of workstation studies; the consideration of the human factor. (N.C.)

  17. UV photoemission from metal cathodes for picosecond power switches

    International Nuclear Information System (INIS)

    Fischer, J.; Srinivasan-RAo, T.; Tsang, T.

    1989-01-01

    Results are reported of photoemission studies using laser pulses of 10 ps duration and 4.66 eV photon energy on metal cathodes. These included thin wires, flat surfaces and an yttrium cathode with a grainy surface. The measurements of current density and quantum efficiency under low and high surface fields indicate that field assisted efficiencies exceeding 0.1% and current densities exceeding 10 5 A/cm 2 are obtainable. The results are compared to the requirements of switch power applications. 24 refs., 13 figs., 1 tab

  18. Pseudogap behavior of RuP probed by photoemission spectroscopy

    OpenAIRE

    Sato, K.; Ootsuki, D.; Wakisaka, Y.; Saini, N. L.; Mizokawa, T.; Arita, M.; Anzai, H.; Namatame, H.; Taniguchi, M.; Hirai, D.; Takagi, H.

    2012-01-01

    We have studied the electronic structure of RuP and related Ru pnictides using photoemission spectroscopy. Ru 3d core-level and valence-band spectra of RuP show that the Ru valence is +3 with t_{2g}^5 configuration. The photoemisson spectral weight near the Fermi level is moderately suppressed in the pseudogap phase of RuP, consistent with the pseudogap opening of 2\\Delta/k_BT_c ~ 3 (gap size \\Delta ~ 50 meV and transition temperature T_c ~ 330 K). The Ru 3d peak remains sharp in the pseudoga...

  19. New developments in laser-based photoemission spectroscopy and its scientific applications: a key issues review

    Science.gov (United States)

    Zhou, Xingjiang; He, Shaolong; Liu, Guodong; Zhao, Lin; Yu, Li; Zhang, Wentao

    2018-06-01

    The significant progress in angle-resolved photoemission spectroscopy (ARPES) in last three decades has elevated it from a traditional band mapping tool to a precise probe of many-body interactions and dynamics of quasiparticles in complex quantum systems. The recent developments of deep ultraviolet (DUV, including ultraviolet and vacuum ultraviolet) laser-based ARPES have further pushed this technique to a new level. In this paper, we review some latest developments in DUV laser-based photoemission systems, including the super-high energy and momentum resolution ARPES, the spin-resolved ARPES, the time-of-flight ARPES, and the time-resolved ARPES. We also highlight some scientific applications in the study of electronic structure in unconventional superconductors and topological materials using these state-of-the-art DUV laser-based ARPES. Finally we provide our perspectives on the future directions in the development of laser-based photoemission systems.

  20. Angle-resolved photoemission extended fine structure

    International Nuclear Information System (INIS)

    Barton, J.J.

    1985-03-01

    Measurements of the Angle-Resolved Photoemission Extended Fine Structure (ARPEFS) from the S(1s) core level of a c(2 x 2)S/Ni(001) are analyzed to determine the spacing between the S overlayer and the first and second Ni layers. ARPEFS is a type of photoelectron diffraction measurement in which the photoelectron kinetic energy is swept typically from 100 to 600 eV. By using this wide range of intermediate energies we add high precision and theoretical simplification to the advantages of the photoelectron diffraction technique for determining surface structures. We report developments in the theory of photoelectron scattering in the intermediate energy range, measurement of the experimental photoemission spectra, their reduction to ARPEFS, and the surface structure determination from the ARPEFS by combined Fourier and multiple-scattering analyses. 202 refs., 67 figs., 2 tabs

  1. X-ray photoemission studies of Zn doped Cu1-xTl xBa2Ca2Cu 3-yZn yO10-δ (y = 0, 2.65) superconductors

    International Nuclear Information System (INIS)

    Khan, Nawazish A.; Mumtaz, M.; Ahadian, M.M.; Iraji-zad, Azam

    2007-01-01

    The X-ray photoemission (XPS) measurements of Cu 1-x Tl x Ba 2 Ca 2 Cu 3-y Zn y O 10-δ (y = 0, 2.65) superconductors have been performed and compared. These studies revealed that the charge state of thallium in the Cu 0.5 Tl 0.5 Ba 2 O 4-δ charge reservoir layer in Zn doped samples is Tl 1+ , while it is a mix of Tl 1+ and Tl 2+ in Zn free samples. The binding energy of Ba atoms in the Zn doped samples is shifted to higher energy, which when considered along with the presence of Tl 1+ suggested that it more efficiently directed the carriers to ZnO 2 and CuO 2 planes. The evidence of improved inter-plane coupling witnessed in X-ray diffraction is also confirmed by XPS measurements of Ca atoms in the Zn doped samples. The shift of the valance band spectrum in these Zn doped samples to higher energies suggested that the electrons at the top edge of the valance band were tied to a higher binding energy (relative to samples without Zn doping), which most likely resulted in a much lower energy state of the system in the superconducting state. The stronger superconducting state arising out of these effects is witnessed in the form of increased T c (R 0), J c and the extent of diamagnetism in the final compound

  2. orbital selective correlation reduce in collapse tetragonal phase of CaFe2(As0.935P0.065)2 and electronic structure reconstruction studied by angel resolved photoemission spectroscopy

    Science.gov (United States)

    Zeng, Lingkun

    We performed an angle-resolved photoemission spectroscopy (ARPES) study of the CaFe2(As0.935P0.065)2 in the collapse tetragonal(CT) phase and uncollapse tetragonal(UCT) phase. We find in the CT phase the electronic correlation dramatically reduces respective to UCT phase. Meanwhile, the reduction of correlation in CT phase show an orbital selective effect: correlation in dxy reduces the most, and then dxz/yz, while the one in dz2-r2 almost keeps the same. In CT phase, almost all bands sink downwards to higher binding energy, leading to the hole like bands around Brillouin zone(BZ) center sink below EF compared with UCT phase. However, the electron pocket around Brillouin Zone(BZ) corner(M) in UCT phase, forms a hole pocket around BZ center(Z point) in CT phase. Moreover, the dxy exhibits larger movement down to higher binding energy, resulting in farther away from dyz/xz and closer to dxy.We propose the electron filling ,namely high spin state in UCT phase to low spin state in CT phase(due to competing between crystal structure field and Hund's coupling), other than the Fermi surface nesting might be responsible for the absent of magnetic ordering.

  3. Ultraviolet photoemission spectroscopy of hydrogen complex deactivation on InP:Zn(1 0 0) surfaces

    International Nuclear Information System (INIS)

    Williams, M.D.; Williams, S.C.; Yasharahla, S.A.; Jallow, N.

    2007-01-01

    Ultraviolet photoemission spectroscopy is used to study the kinetics of the H-Zn complex deactivation in Zn doped InP(1 0 0). Hydrogen injected into the material electronically passivates the local carrier concentration. Reverse-biased anneals of the InP under ultra-high vacuum show a dramatic change in the work function of the material with increasing temperature. Spectral features are also shown to be sensitive to sample temperature. To our knowledge, we show the first view of hydrogen retrapping at the surface using photoemission spectroscopy. A simple photoelectron threshold energy analysis shows the state of charge compensation of the material

  4. Photoemission in nanosecond and picosecond regimes obtained from macro and micro cathodes

    International Nuclear Information System (INIS)

    Boussoukaya, M.; Bergeret, H.; Chehab, R.; Leblond, B.; Franco, M.

    1987-03-01

    For Lasertron studies at LAL, results obtained from tests on different photocathodes are given below. Using respectively two Nd: YAG lasers (a nanosecond one and a picosecond one) we have determined the level and the intensity of pulsed photoemission and the photoelectric yield in UV, green and infrared lights. We obtained a total current of more than 1 A with nanosecond width from a single W needle, and photoconversion yield of more than 1 was reached in green and UV lights. In classical pulsed photoemission, obtained photoconversion yield from LaB 6 photocathode was of about 10 -3 in higher fields

  5. Photoemission starting of induction rf-driven multicusp ion sources

    International Nuclear Information System (INIS)

    Pickard, D.S.; Leung, K.N.; Perkins, L.T.; Ponce, D.M.; Young, A.T.

    1996-01-01

    It has been demonstrated that pulsed and continuous wave, rf-driven hydrogen discharges can be started with photoemission. The extracted H - current from a photoemission-started plasma has been investigated and does not differ significantly from that of a filament-started plasma. The minimum pressure for photoemissive starting was found to be higher than that of filament starting, 17 mTorr compared to 7 mTorr, respectively, in this particular configuration. copyright 1996 American Institute of Physics

  6. Atomic physics research with synchrotron radiation

    International Nuclear Information System (INIS)

    Crasemann, B.; Wuilleumier, F.

    1985-01-01

    This chapter discusses applications of synchrotron light in atomic and molecular physics. Use of the radiation from storage rings has expanded and lent access to new areas of absorption and photoemission spectroscopy and scattering experiments. Techniques applied in connection with synchrotron radiation are discussed including absorption spectroscopy, photoelectron spectroscopy, fluorescence spectroscopy and X-ray scattering. Problem areas that are being studied by the techniques mentioned above are discussed. Synchrotron radiation has provided the means for measuring the threshold-excitation and interference effects that signal the breakdown of the two-step model of atomic excitation/deexcitation. Synchrotron radiation provides more means of excited-state photoionization measurements

  7. Radiation toxicity studies in dogs

    International Nuclear Information System (INIS)

    Fritz, T.E.; Carnes, B.A.; Duggal, K.

    1985-01-01

    These studies provide data that identify tissue sensitivities, target organs, disease processes, life shortening values, and mortality rates that result from continuous and terminated exposures to whole-body radiations and relate them to various total doses and dose rates. The data from protracted exposures given at rates between 3.8 and 26.3 cGys per day show that the life shortening and numbers of fatal tumors are determined by total dose when the irradiation is terminated at total doses between 450 and 3000 cGys. 4 refs

  8. Experimental investigation of nondipole effects in photoemission at the advanced light source

    International Nuclear Information System (INIS)

    Guillemin, Renaud; Hemmers, Oliver; Lindle, Dennis W.; Manson, Steven T.

    2005-01-01

    Breakdowns in the dipole approximation in the soft-X-ray photon-energy range (hν<5keV) were first observed 30 years ago and have been studied theoretically for many years. However, only recently their significance at low energies has been appreciated when advances in gas-phase-photoemission experiments using synchrotron radiation began to highlight numerous examples of significant nondipole effects at photon energies as low as tens of eV. In a previous publication [Hemmers et al., 2004a. Radiat. Phys. Chem. 70, 123-147], we presented a description of the recent advances made in the investigation of nondipole effects in photoionization from an experimental perspective. In this article, we report the results obtained by the X-ray atomic and molecular spectroscopy (XAMS) group at the Advanced Light Source, over the last 10 years, on the limits of the dipole approximation, probed by angle-resolved photoelectron spectroscopy for atoms and molecules in gas phase

  9. Electronic Structure of the Kitaev Material α-RuCl3 Probed by Photoemission and Inverse Photoemission Spectroscopies

    Science.gov (United States)

    Sinn, Soobin; Kim, Choong Hyun; Kim, Beom Hyun; Lee, Kyung Dong; Won, Choong Jae; Oh, Ji Seop; Han, Moonsup; Chang, Young Jun; Hur, Namjung; Sato, Hitoshi; Park, Byeong-Gyu; Kim, Changyoung; Kim, Hyeong-Do; Noh, Tae Won

    2016-12-01

    Recently, α-RuCl3 has attracted much attention as a possible material to realize the honeycomb Kitaev model of a quantum-spin-liquid state. Although the magnetic properties of α-RuCl3 have been extensively studied, its electronic structure, which is strongly related to its Kitaev physics, is poorly understood. Here, the electronic structure of α-RuCl3 was investigated by photoemission (PE) and inverse-photoemission (IPE) spectroscopies. The band gap was directly measured from the PE and IPE spectra and was found to be 1.9 eV, much larger than previously estimated values. Local density approximation (LDA) calculations showed that the on-site Coulomb interaction U could open the band gap without spin-orbit coupling (SOC). However, the SOC should also be incorporated to reproduce the proper gap size, indicating that the interplay between U and SOC plays an essential role. Several features of the PE and IPE spectra could not be explained by the results of LDA calculations. To explain such discrepancies, we performed configuration-interaction calculations for a RuCl63- cluster. The experimental data and calculations demonstrated that the 4d compound α-RuCl3 is a Jeff = 1/2 Mott insulator rather than a quasimolecular-orbital insulator. Our study also provides important physical parameters required for verifying the proposed Kitaev physics in α-RuCl3.

  10. Resonant photoemission study on La0.7Ca0.3MnO3 using Indus-1 synchrotron source

    International Nuclear Information System (INIS)

    Sagdeo, P.R.; Choudhary, R.J.; Phase, D.M.

    2008-01-01

    The electronic valance band structure of pulsed laser deposited La 0.7 Ca 0.3 MnO 3 thin film has been investigated by resonant photoelectron spectroscopy using CSR beamline (BL-2) on Indus-1 synchrotron radiation source. The valance band spectra were measured at room temperature with the photon energy ranging from 40 eV to 60 eV. The contribution of Mn-3d to the valance band was determined using resonant photo-electron intensity near Mn3p-3d threshold. (author)

  11. International workshop on the 'Physics of interfaces by synchrotron radiation and other high energy probes'

    International Nuclear Information System (INIS)

    Krummacher, S.; Gudat, W.

    1986-05-01

    The present 'book of abstracts' consists of the abstracts of 23 lectures, held at the international workshop on the 'Physics of interfaces by synchrotron radiation and other high energy probes', April 1986, Bad Honnef, FRG. The subjects are: The use of photoemission in the study of interfaces and adsorbates, EEL spectroscopy applications, spin polarization, photoionization processes and EXAFS. (BHO)

  12. Gas-phase photoemission with soft x-rays: Cross sections and angular distributions

    International Nuclear Information System (INIS)

    Shirley, D.A.; Kobrin, P.H.; Truesdale, C.M.; Lindle, D.W.; Ferrett, T.A.; Heimann, P.A.; Becker, U.; Kerkhoff, H.G.; Southworth, S.H.

    1983-01-01

    A summary is presented of typical gas-phase photoemission studies based on synchrotron radiation in the 50-5000 eV range, using beam lines at the Stanford Synchrotron Radiation Laboratory. Three topics are addressed: atomic inner-shell photoelectron cross sections and asymmetries, correlation peaks in rare gases, and core-level shape resonances in molecules. Photoelectron cross-section σ(n iota) and asymmetry-parameter β(n iota) studies in mercury vapor at photon energies up to 270 eV (up to 600 eV for β/sub 4f/) extend coverage of these parameters to n≤5 and iota≤3. Comparison with Dirac-Slater and relativistic random-phase approximation calculations reveals systematic discrepancies. For example, distinct Cooper minima in σ(n iota) are observed but not predicted, while predicted β(n iota) values are typically too high. Correlation satellites have been studied for the K shells of helium (hν = 68-90 eV), neon (hν = 870-960 eV) and argon (hν = 3200-3320 eV). In helium the n=2 satellite peak was shown to have mainly 2p character at threshold, and its asymmetry was measured through the autoionizing resonance region. Tentative evidence was obtained that the neon satellites are less intense near threshold than in the high-energy limit, and that their intensities stay constant or decrease with increasing energy near threshold. A new satellite was observed in argon at 24.6 eV which appears to increase in intensity with energy. Molecular core-level shape resonances were observed for the first time by photoemission, yielding σ(hν) and β(hν) for core levels from 180 eV binding energy (S 2p in SF/sub 6/ and OCS) through C 1s in CO, CO/sub 2/ and CF/sub 4/, N 1s in N/sub 2/ and NO, and O 1s in CO and CO/sub 2/ to 2490 eV (S 1s in SF/sub 6/). Several conclusions can be drawn about the photoelectron and Auger cross sections and asymmetry parameters

  13. Multiplet splitting of x-ray photoemission spectra core levels in magnetic metals

    International Nuclear Information System (INIS)

    Kowalczyk, S.P.; McFeely, F.R.; Ley, L.; Shirley, D.A.

    1975-01-01

    The results of high resolution x-ray photoemission studies of the multiplet splitting of the 3s core levels in the 3d transition metals and the 4s, 5s and 4d core levels in the lanthanide metals are reported

  14. Angle-resolved photoemission spectroscopy of liquid water at 29.5 eV.

    Science.gov (United States)

    Nishitani, Junichi; West, Christopher W; Suzuki, Toshinori

    2017-07-01

    Angle-resolved photoemission spectroscopy of liquid water was performed using extreme ultraviolet radiation at 29.5 eV and a time-of-flight photoelectron spectrometer. SiC/Mg coated mirrors were employed to select the single-order 19th harmonic from laser high harmonics, which provided a constant photon flux for different laser polarizations. The instrument was tested by measuring photoemission anisotropy for rare gases and water molecules and applied to a microjet of an aqueous NaI solution. The solute concentration was adjusted to eliminate an electric field gradient around the microjet. The observed photoelectron spectra were analyzed considering contributions from liquid water, water vapor, and an isotropic background. The anisotropy parameters of the valence bands (1 b 1 , 3 a 1 , and 1 b 2 ) of liquid water are considerably smaller than those of gaseous water, which is primarily attributed to electron scattering in liquid water.

  15. Angle-resolved photoemission spectroscopy of liquid water at 29.5 eV

    Directory of Open Access Journals (Sweden)

    Junichi Nishitani

    2017-07-01

    Full Text Available Angle-resolved photoemission spectroscopy of liquid water was performed using extreme ultraviolet radiation at 29.5 eV and a time-of-flight photoelectron spectrometer. SiC/Mg coated mirrors were employed to select the single-order 19th harmonic from laser high harmonics, which provided a constant photon flux for different laser polarizations. The instrument was tested by measuring photoemission anisotropy for rare gases and water molecules and applied to a microjet of an aqueous NaI solution. The solute concentration was adjusted to eliminate an electric field gradient around the microjet. The observed photoelectron spectra were analyzed considering contributions from liquid water, water vapor, and an isotropic background. The anisotropy parameters of the valence bands (1b1, 3a1, and 1b2 of liquid water are considerably smaller than those of gaseous water, which is primarily attributed to electron scattering in liquid water.

  16. Photoemission investigation of the ZnSe/CdTe heterojunction band discontinuity

    International Nuclear Information System (INIS)

    Nelson, A.J.

    1995-01-01

    Synchrotron radiation soft x-ray photoemission spectroscopy and reflection high-energy electron diffraction were used to investigate the structural and electronic properties at the ZnSe/CdTe(100) heterojunction interface. ZnSe overlayers were sequentially grown in steps on p-type CdTe(100) single crystals at 200 degree C. In situ photoemission measurements were acquired after each growth in order to observe changes in the valence band electronic structure as well as changes in the Cd 4d, Zn 3d, and Te 4d core lines. The results were used to correlate the interfacial chemistry with the electronic structure and to directly determine the ZnSe/CdTe heterojunction valence band discontinuity and the consequent heterojunction band diagram. Results of these measurements reveal that the valence band offset is ΔE v =0.20 eV. copyright 1995 American Institute of Physics

  17. Study of biological effect of radiation

    International Nuclear Information System (INIS)

    Li Guisheng

    1992-01-01

    The some progress on the study of biological effect for protract exposure to low dose rate radiation is reported, and it is indicated that the potential risk of this exposure for the human health and the importance of the routine monitoring of radiation dose for various nuclear installations. The potential exposure to the low dose rate radiation would attract people's extra attention

  18. Radiation studies in the antiproton source

    International Nuclear Information System (INIS)

    Church, M.

    1990-01-01

    Experiment E760 has a lead glass (Pb-G) calorimeter situated in the antiproton source tunnel in the accumulator ring at location A50. This location is exposed to radiation from several sources during antiproton stacking operations. A series of radiation studies has been performed over the last two years to determine the sources of this radiation and as a result, some shielding has been installed in the antiproton source in order to protect the lead glass from radiation damage

  19. Experimental Study on radiation myelopathy

    International Nuclear Information System (INIS)

    Kaneko, Itsuo; Matsushima, Hideno; Yamada, Teruyo

    1979-01-01

    Experimental radiation myelopathy was carried out useing rats. This studies were done refering the effect to skin, the body weight, the status of the paralysis and the capillary densities of the cervical cords. The quadriplegia was seen on the animals which were irradiated over 4000 rad. The vacuoal degeneration was observed on the cervical cords which were irradiated over 4000 rad. The capillary densities of gray matter and white matter decreased finally in proportions to the irradiation dose. The vacuoal degeneration was recognized on the cervical cord in which the capillary density decreased to under 70 per cent of normal density. Decrease of the capillary density is seemed to be the one of the cause of the paralysis. (author)

  20. Vacuum scanning capillary photoemission microscopy

    DEFF Research Database (Denmark)

    Aseyev, S.A.; Cherkun, A P; Mironov, B N

    2017-01-01

    of a gold reflecting layer on a compact disc which has been illuminated by an unfocused laser beam with a wavelength 400nm, from a femtosecond laser with a beam size of 4mm. A quartz capillary with a 2-µm aperture has been used in the experiments. The period of gold microstructure, shown to be 1.6µ...... distribution of the recorded photoelectrons consisted of periodic mountain-valley strips, resembling the surface profile of the sample. Submicron spatial resolution has been achieved. This approach paves the way to study pulsed photodesorption of large organic molecular ions with high spatial and element...

  1. Photoemission and photoionization time delays and rates

    Science.gov (United States)

    Gallmann, L.; Jordan, I.; Wörner, H. J.; Castiglioni, L.; Hengsberger, M.; Osterwalder, J.; Arrell, C. A.; Chergui, M.; Liberatore, E.; Rothlisberger, U.; Keller, U.

    2017-01-01

    Ionization and, in particular, ionization through the interaction with light play an important role in fundamental processes in physics, chemistry, and biology. In recent years, we have seen tremendous advances in our ability to measure the dynamics of photo-induced ionization in various systems in the gas, liquid, or solid phase. In this review, we will define the parameters used for quantifying these dynamics. We give a brief overview of some of the most important ionization processes and how to resolve the associated time delays and rates. With regard to time delays, we ask the question: how long does it take to remove an electron from an atom, molecule, or solid? With regard to rates, we ask the question: how many electrons are emitted in a given unit of time? We present state-of-the-art results on ionization and photoemission time delays and rates. Our review starts with the simplest physical systems: the attosecond dynamics of single-photon and tunnel ionization of atoms in the gas phase. We then extend the discussion to molecular gases and ionization of liquid targets. Finally, we present the measurements of ionization delays in femto- and attosecond photoemission from the solid–vacuum interface. PMID:29308414

  2. Photoemission and photoionization time delays and rates

    Directory of Open Access Journals (Sweden)

    L. Gallmann

    2017-11-01

    Full Text Available Ionization and, in particular, ionization through the interaction with light play an important role in fundamental processes in physics, chemistry, and biology. In recent years, we have seen tremendous advances in our ability to measure the dynamics of photo-induced ionization in various systems in the gas, liquid, or solid phase. In this review, we will define the parameters used for quantifying these dynamics. We give a brief overview of some of the most important ionization processes and how to resolve the associated time delays and rates. With regard to time delays, we ask the question: how long does it take to remove an electron from an atom, molecule, or solid? With regard to rates, we ask the question: how many electrons are emitted in a given unit of time? We present state-of-the-art results on ionization and photoemission time delays and rates. Our review starts with the simplest physical systems: the attosecond dynamics of single-photon and tunnel ionization of atoms in the gas phase. We then extend the discussion to molecular gases and ionization of liquid targets. Finally, we present the measurements of ionization delays in femto- and attosecond photoemission from the solid–vacuum interface.

  3. Metal/silicon Interfaces and Their Oxidation Behavior - Photoemission Spectroscopy Analysis.

    Science.gov (United States)

    Yeh, Jyh-Jye

    Synchrotron radiation photoemission spectroscopy was used to study Ni/Si and Au/Si interface properties on the atomic scale at room temperature, after high temperature annealing and after oxygen exposures. Room temperature studies of metal/Si interfaces provide background for an understanding of the interface structure after elevated temperature annealing. Oxidation studies of Si surfaces covered with metal overlayers yield insight about the effect of metal atoms in the Si oxidation mechanisms and are useful in the identification of subtle differences in bonding relations between atoms at the metal/Si interfaces. Core level and valence band spectra with variable surface sensitivities were used to study the interactions between metal, Si, and oxygen for metal coverages and oxide thickness in the monolayer region. Interface morphology at the initial stage of metal/Si interface formation and after oxidation was modeled on the basis of the evolutions of metal and Si signals at different probing depths in the photoemission experiment. Both Ni/Si and Au/Si interfaces formed at room temperature have a diffusive region at the interface. This is composed of a layer of metal-Si alloy, formed by Si outdiffusion into the metal overlayer, above a layer of interstitial metal atoms in the Si substrate. Different atomic structures of these two regions at Ni/Si interface can account for the two different growth orientations of epitaxial Ni disilicides on the Si(111) surface after thermal annealing. Annealing the Au/Si interface at high temperature depletes all the Au atoms except for one monolayer of Au on the Si(111) surface. These phenomena are attributed to differences in the metal-Si chemical bonding relations associated with specific atomic structures. After oxygen exposures, both the Ni disilicide surface and Au covered Si surfaces (with different coverages and surface orderings) show silicon in higher oxidation states, in comparison to oxidized silicon on a clean surface

  4. Studies on application of radiation and radioisotopes

    International Nuclear Information System (INIS)

    Kim, Jae Rok; Lee, Ji Bok; Lee, Yeong Iil; Jin, Joon Ha; Beon, Myeong Uh; Park, Kyeong Bae; Han, Heon Soo; Jeong, Yong Sam; Uh, Jong Seop; Kang, Kyeong Cheol; Cho, Han Ok; Song, Hui Seop; Yoon, Byeong Mok; Jeon, Byeong Jin; Park, Hong Sik; Kim, Jae Seong; Jeong, Un Soo; Baek, Sam Tae; Cho, Seong Won; Jeon, Yeong Keon; Kim, Joon Yeon; Kwon, Joong Ho; Kim, Ki Yeop; Yang, Jae Seung; No, Yeong Chang; Lee, Yeong Keun; Shin, Byeong Cheol; Park, Sang Joon; Hong, Kwang Pyo; Cho, Seung Yeon; Kang, Iil Joon; Cho, Seong Ki; Jeong, Yeong Joo; Park, Chun Deuk; Lee, Yeong Koo; Seo, Chun Ha; Han, Kwang Hui; Shin, Hyeon Young; Kim, Jong Kuk; Park, Soon Chul; Shin, In Cheol; Lee, Sang Jae; Lee, Ki Un; Lim, Yong Taek; Park, Eung Uh; Kim, Dong Soo; Jeon, Sang Soo

    1993-05-01

    With the completion of construction of KMRR, the facility and technology of radiation application will be greatly improved. This study was performed as follows; (1) Studies on the production and application of radioisotopes. (2) The development of radiation processing technology. (3) The application of Irradiation techniques for food preservation and process improvement. (4) Studies on the radiation application for the development of genetic resources (5) Development of the radioisotope (RI) production facilities for Korea Multipurpose Research Reactor (KMRR)

  5. Photoemission and the electronic properties of heavy fermions -- limitations of the Kondo model

    International Nuclear Information System (INIS)

    Joyce, J.J.; Arko, A.J.; Andrews, A.B.

    1993-01-01

    The electronic properties of Yb-based heavy fermions have been investigated by means of high resolution synchrotron radiation photoemission and compared with predictions of the Kondo model. The Yb heavy fermion photoemission spectra show massive disagreement with the Kondo model predictions (as calculated within the Gunnarsson-Schonhammer computational method). Moreover, the Yb heavy fermion photoemission spectra give very strong indications of core-like characteristics and compare favorable to purely divalent Yb metal and core-like Lu 4f levels. The heavy fermions YbCu 2 Si 2 , YbAgCu 4 and YbAl 3 were measured and shown to have lineshapes much broader and deeper in binding energy than predicted by the Kondo model. The lineshape of the bulk component of the 4f emission for these three heavy fermion materials was compared with that from Yb metal and the Lu 4f levels in LuAl 3 , the heavy fermion materials show no substantive spectroscopic differences from simple 4f levels observed in Yb metal and LuAl 3 . Also, the variation with temperature of the 4f fineshape was measured for Yb metal and clearly demonstrates that phonon broadening plays a major role in 4f level lineshape analysis and must be accounted for before considerations of correlated electron resonance effects are presumed to be at work

  6. Liquid droplet radiator performance studies

    Science.gov (United States)

    Mattick, A. T.; Hertzberg, A.

    By making use of droplets rather than solid surfaces to radiate waste heat in space, the liquid droplet radiator (LDR) achieves a radiating area/mass much larger than that of conventional radiators which use fins or heat pipes. The lightweight potential of the LDR is shown to be limited primarily by the radiative properties of the droplets. The requirement that the LDR heat transfer fluid have a very low vapor pressure limits the choice of fluids to relatively few—several liquid metals and Dow 705 silicone fluid are the only suitable candidates so far identified. An experimental determination of the emittance of submillimeter droplets of Dow 705 fluid indicates than an LDR using this fluid at temperatures of 275-335 K would be ⋍ 10 times lighter than the lightest solid surface radiators. Although several liquid metals appear to offer excellent performance in LDR applications at temperatures between 200 K and 975 K, experimental determination of liquid metal emissivities is needed for a conclusive assessment.

  7. Directional uv photoemission from (100) and (110) molybdenum surfaces

    DEFF Research Database (Denmark)

    Cinti, R. C.; Khoury, E. Al; Chakraverty, B. K.

    1976-01-01

    A study of the (100) and (110) molybdenum surfaces by directional photoemission spectroscopy is presented. Energy distribution spectra formed by photoelectrons emitted normal to the surfaces have been measured for photon energies between 10.2 and 21.2 eV. The results are discussed in terms of cal......-transition and surface-emission processes. Two extra structures are interpreted in terms of surface states or resonances: on the (100) surface, 0.5 eV below EF; on the (110) surface, 4.5 eV below EF in the s-d hybridization gap....... of calculated band structure within the framework of the K∥-conservation assumption. A good agreement is found between the main features of the experimental spectra and the emission expected from the band structure along the corresponding symmetry line in the Brillouin zone, assuming essentially direct...

  8. Microlens Array Laser Transverse Shaping Technique for Photoemission Electron Source

    Energy Technology Data Exchange (ETDEWEB)

    Halavanau, A. [Northern Illinois Univ., DeKalb, IL (United States); Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Ha, G. [Argonne National Lab. (ANL), Argonne, IL (United States); Pohang Univ. of Science and Technology (POSTECH) (Korea, Republic of); Qiang, G. [Argonne National Lab. (ANL), Argonne, IL (United States); Tsinghua Univ., Beijing (China); Gai, W. [Argonne National Lab. (ANL), Argonne, IL (United States); Power, J. [Argonne National Lab. (ANL), Argonne, IL (United States); Piot, P. [Northern Illinois Univ., DeKalb, IL (United States); Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Wisniewski, E. [Argonne National Lab. (ANL), Argonne, IL (United States); Edstrom, D. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Ruan, J. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Santucci, J. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)

    2016-09-06

    A common issue encountered in photoemission electron sources used in electron accelerators is distortion of the laser spot due to non ideal conditions at all stages of the amplification. Such a laser spot at the cathode may produce asymmetric charged beams that will result in degradation of the beam quality due to space charge at early stages of acceleration and fail to optimally utilize the cathode surface. In this note we study the possibility of using microlens arrays to dramatically improve the transverse uniformity of the drive laser pulse on UV photocathodes at both Fermilab Accelerator Science \\& Technology (FAST) facility and Argonne Wakefield Accelerator (AWA). In particular, we discuss the experimental characterization of the homogeneity and periodic patterned formation at the photocathode. Finally, we compare the experimental results with the paraxial analysis, ray tracing and wavefront propagation software.

  9. Large Band Gap of alpha-RuCl3 Probed by Photoemission and Inverse Photoemission Spectroscopy

    Science.gov (United States)

    Sinn, Soobin; Kim, Choong Hyun; Sandilands, Luke; Lee, Kyungdong; Won, Choongjae; Oh, Ji Seop; Han, Moonsup; Chang, Young Jun; Hur, Namjung; Sato, Hitoshi; Park, Byeong-Gyu; Kim, Changyoung; Kim, Hyeong-Do; Noh, Tae Won

    The Kitaev honeycomb lattice model has attracted great attention because of its possibility to stabilize a quantum spin liquid ground state. Recently, it was proposed that alpha-RuCl3 is its material realization and the first 4 d relativistic Mott insulator from an optical spectrum and LDA + U + SO calculations. Here, we present photoemission and inverse photoemission spectra of alpha-RuCl3. The observed band gap is about 1.8 eV, which suggests that the previously assigned optical gap of 0.3 eV is misinterpreted, and that the strong peak at about 1.2 eV in the optical spectrum may be associated with an actual optical gap. Assuming a strong excitonic effect of 0.6 eV in the optical spectrum, all the structures except for the peak at 0.3 eV are consistent with our electronic spectra. When compared with LDA + U + SO calculations, the value of U should be considerably larger than the previous one, which implies that the spin-orbit coupling is not a necessary ingredient for the insulating mechanism of alpha-RuCl3. We also present angle-resolved photoemission spectra to be compared with LDA + U + SO and LDA +DMFT calculations.

  10. Efficient photoemission from robust ferroelectric ceramics

    International Nuclear Information System (INIS)

    Boscolo, I.; Castellano, M.; Catani, L.; Ferrario, M.; Tazzioli, F.; Giannessi, L.

    1999-01-01

    Experimental results on photoemission by ferroelectric ceramic disks, with a possible interpretation, are present. Two types of lead zirconate titanate lanthanum doped, PLZT, ceramics have been used for tests. 25 ps light pulses of 532 and 355 nm were used for excitation. The intensity ranged within the interval 0.1-3 GW/cm 2. The upper limit of the intensity was established by the damage threshold tested by the onset of ion emission. At low value of the intensity the yield was comparable at the two wavelengths. At the highest intensity of green light the emitted charge was 1 nC per 10 mm 2, but it was limited by the space charge effect. In fact, the applied field was only 20 kV/cm, allowed both by the mechanical design of the apparatus and the poor vacuum, 10 - 4 mbar. No surface processing was required. The measurement of the electron pulse length under way

  11. Timing analysis of two-electron photoemission

    International Nuclear Information System (INIS)

    Kheifets, A S; Ivanov, I A; Bray, Igor

    2011-01-01

    We predict a significant delay of two-electron photoemission from the helium atom after absorption of an attosecond XUV pulse. We establish this delay by solving the time-dependent Schroedinger equation and by subsequently tracing the field-free evolution of the two-electron wave packet. This delay can also be related to the energy derivative of the phase of the complex double-photoionization (DPI) amplitude which we evaluate by using the convergent close-coupling method. Our observations indicate that future attosecond time delay measurements on DPI of He can provide information on the absolute quantum phase and elucidate various mechanisms of this strongly correlated ionization process. (fast track communication)

  12. Electronic Structure of C60/Zinc Phthalocyanine/V2O5 Interfaces Studied Using Photoemission Spectroscopy for Organic Photovoltaic Applications

    Directory of Open Access Journals (Sweden)

    Chang Jin Lim

    2018-02-01

    Full Text Available The interfacial electronic structures of a bilayer of fullerene (C60 and zinc phthalocyanine (ZnPc grown on vanadium pentoxide (V2O5 thin films deposited using radio frequency sputtering under various conditions were studied using X-ray and ultraviolet photoelectron spectroscopy. The energy difference between the highest occupied molecular orbital (HOMO level of the ZnPc layer and the lowest unoccupied molecular orbital (LUMO level of the C60 layer was determined and compared with that grown on an indium tin oxide (ITO substrate. The energy difference of a heterojunction on all V2O5 was found to be 1.3~1.4 eV, while that on ITO was 1.1 eV. This difference could be due to the higher binding energy of the HOMO of ZnPc on V2O5 than that on ITO regardless of work functions of the substrates. We also determined the complete energy level diagrams of C60/ZnPc on V2O5 and ITO.

  13. Studies on education for radiation and courses of study (2009)

    International Nuclear Information System (INIS)

    Sakuraba, Kazuhiro; Nakamura, Hideo; Ukai, Mitsuko

    2009-01-01

    The Courses of Study are provided as the standards for educational courses in all schools in Japan. The new Courses of Study have been started this year. In this research, we revealed the ways how to teach radiation using the Courses of Study (2009). Education for radiation was first opened for the third grade of secondary school children. The contents in terms of radiation education in this Courses of Study (2009) are the characterization and application of radiation. To promote this new study courses, the knowledge about radiation of young man and woman were also studied. We concluded it is necessary to start radiation education from elementary school. Furthermore to apply the Courses of Study effectively, we need the comments on radiation education from the researcher of radiation. After the comments, teachers are able to make precise educational materials for their own children. (author)

  14. Photoemission of Single Dust Grains for Heliospheric Conditions

    Science.gov (United States)

    Spann, James F., Jr.; Venturini, Catherine C.; Abbas, Mian M.; Comfort, Richard H.

    2000-01-01

    Initial results of an experiment to measure the photoemission of single dust grains as a function of far ultraviolet wavelengths are presented. Coulombic forces dominate the interaction of the dust grains in the heliosphere. Knowledge of the charge state of dust grains, whether in a dusty plasma (Debye length grains is primarily determined by primary electron and ion collisions, secondary electron emission and photoemission due to ultraviolet sunlight. We have established a unique experimental technique to measure the photoemission of individual micron-sized dust grains in vacuum. This technique resolves difficulties associated with statistical measurements of dust grain ensembles and non-static dust beams. The photoemission yield of Aluminum Oxide 3-micron grains For wavelengths from 120-300 nm with a spectral resolution of 1 nm FWHM is reported. Results are compared to interplanetary conditions.

  15. Statistical trend of radiation chemical studies

    International Nuclear Information System (INIS)

    Yoshida, Hiroshi

    1980-01-01

    In the field of radiation chemistry, over 1,000 reports are published year after year. Attempt has been made to review the trends in this field for more than five years, by looking through the lists of papers statistically. As for the period from 1974 to 1978, Annual Cumulation with Keyword and Author Indexes in the Biweekly List of Papers on Radiation Chemistry was referred to. For 1979, because of the unavailability of the Cumulation, Chemical Abstracts Search by Japan Information Center of Science and Technology was referred to. The contents are as follows: how far radiation chemistry is studied, what the trends of radiation chemistry is in recent years, who contributes to the advance of radiation chemistry, and where, the trend radiation chemistry takes in 1979. (J.P.N.)

  16. Epidemiological studies on radiation workers in Korea

    International Nuclear Information System (INIS)

    Soo Yong Choi; Hai Won Chung

    2007-01-01

    Complete text of publication follows. Objectives: The aim of this study is to analyze the occupational exposure for external radiation and to evaluate radiation effects on Korean radiation workers. Methods: The National Dose Registry contains radiation exposure records for all monitored radiation workers since its creation in 1983. We are carrying out epidemiological survey for radiation workers. The items of information included personal identification, employment and dose data. The frequencies of various types of chromosome aberrations in radiation workers were compared with controls. The data were analyzed according to year, sex, age, duration of occupation, exposure dose, etc. using SPSS statistical package(version 15.0). The goodness-of-fit test for Poisson assumption and dispersion test for detecting heterogeneity for Poisson distribution were done with chromosomal aberrations among study subjects. Results: The total number of workers registered from 1983 to 2005 was 61,610. The number of workers steadily increased and the accumulated dose somewhat increased. The collective annual dose of radiation workers was 345.823 man Sv and the mean annual dose was 1.34mSv. The frequencies of chromosome aberrations in 102 workers were compared with those in 42 controls. The frequencies of all types of chromosome aberrations in the exposed subjects were higher than those in the control group. Poisson regression analysis showed that there was significant association of chromosome aberrations with radiation dose, duration of work, age and alcohol intake. We started to survey radiation workers in order to evaluate radiation effects, collected epidemiological data for 9,157 workers at present and analyzed their lifetime radiation exposure doses. Follow-up is carrying out using the Korean Mortality Data, Cancer Registry and individual investigation. Among study patients, 11 of 38 deaths were identified with cancer. Conclusions: The data on occupational doses shows that

  17. Study of detectors in beta radiation fields

    International Nuclear Information System (INIS)

    Albuquerque, M. da P.P.; Xavier, M.; Caldas, L.V.E.

    1987-01-01

    Several commercial detectors used with gamma or X radiation are studied. Their sensibility and energetic dependence are analysed in exposures of beta radiation fields. A comparative evaluation with the reference detector (the extrapolation chamber) is presented. (M.A.C.) [pt

  18. Absence of photoemission from the Fermi level in potassium intercalated picene and coronene films: structure, polaron, or correlation physics?

    Science.gov (United States)

    Mahns, Benjamin; Roth, Friedrich; Knupfer, Martin

    2012-04-07

    The electronic structure of potassium intercalated picene and coronene films has been studied using photoemission spectroscopy. Picene has additionally been intercalated using sodium. Upon alkali metal addition core level as well as valence band photoemission data signal a filling of previously unoccupied states of the two molecular materials due to charge transfer from potassium. In contrast to the observation of superconductivity in K(x)picene and K(x)coronene (x ~ 3), none of the films studied shows emission from the Fermi level, i.e., we find no indication for a metallic ground state. Several reasons for this observation are discussed.

  19. Photoemission spectroscopy of the charge-ordering transition in Pr0.5Sr0.5MnO3

    International Nuclear Information System (INIS)

    Chainani, A.; Kumigashira, H.; Takahashi, T.; Tomioka, Y.; Kuwahara, H.; Tokura, Y.

    1996-01-01

    In this paper, the electronic structure of the magnetite Pr 0.5 Sr 0.5 MnO 3 across the charge ordering transition is studied using temperature-dependent photoemission spectroscopy. Ultra-violet photoemission spectroscopy have been performed as a function of temperature (25-300K) to investigate the changes in the single-particle density of states across the metal-nonmetal and the para-ferro transitions

  20. Epidemiological studies in high background radiation areas

    International Nuclear Information System (INIS)

    Akiba, Suminori

    2012-01-01

    Below the doses of 100-200 mSv of radiation exposure, no acute health effect is observed, and the late health effects such as cancer are yet unclear. The problems making the risk evaluation of low dose radiation exposure difficult are the fact that the magnitude of expected health effects are small even if the risk is assumed to increase in proportion to radiation doses. As a result, studies need to be large particular when dealing with rare disease such as cancer. In addition, the expected health effects are so small that they can easily be masked by lifestyles and environmental factors including smoking. This paper will discuss cancer risk possibly associated with low-dose and low-dose rate radiation exposure, describing epidemiological studies on the residents in the high-background radiation areas. (author)

  1. Electrospray deposition of fullerenes in ultra-high vacuum: in situ scanning tunneling microscopy and photoemission spectroscopy

    International Nuclear Information System (INIS)

    Satterley, Christopher J; Perdigao, LuIs M A; Saywell, Alex; Magnano, Graziano; Rienzo, Anna; Mayor, Louise C; Dhanak, Vinod R; Beton, Peter H; O'Shea, James N

    2007-01-01

    Electrospray deposition of fullerenes on gold has been successfully observed by in situ room temperature scanning tunneling microscopy and photoemission spectroscopy. Step-edge decoration and hexagonal close-packed islands with a periodicity of 1 nm are observed at low and multilayer coverages respectively, in agreement with thermal evaporation studies. Photoemission spectroscopy shows that fullerenes are being deposited in high purity and are coupling to the gold surface as for thermal evaporation. These results open a new route for the deposition of thermally labile molecules under ultra-high vacuum conditions for a range of high resolution surface science techniques

  2. Radiation and environment - impact studies awareness

    International Nuclear Information System (INIS)

    Boniface Ekechukwu; Mohd. Zohadie Bardaie

    2005-01-01

    Radiation, which is simply defined as energy, that travels in the form of waves or particles has both positive and negative effects on humans. This has necessitated a careful study on how to create awareness on the 'two-edge sword'. Since radiation cannot be removed from our environment we, however, reduce our risks by controlling our exposure to it through various ways. Understanding radiation and radioactivity will help us make informed decisions about our exposure. Many difference types of radiation have range of energy that form electromagnetic spectrum. Their sources include nuclear power plants, nuclear weapons, and medicine. Others include, microwaves, radar, electrical power lines, cellular phones, and sunlight' and so on. However, the radiation used in nuclear power, nuclear weapons, and medicine has enough energy to break chemical bonds, and is referred to as 'ionizing radiation', which is dangerous to life. Because of this negative effect of radiation there is common fear and myths related to radiation, radioactivity, uranium mining and milling, and the nuclear industry. This radiation education and energy-environmental education attempt to dispel the common fears and myths relating to them in so far as there is perfect protection from harmful exposure and abuse. The design of an integrated unit of study radiation and environmental energy uses arts of language, life skills, skill designs, social studies and mathematical skills in creating understanding and abilities necessary to do scientific inquiry by the students without abuse or danger. The education unit is designed to assess materials for, factual information and appropriate language and identification of potential bias in environmental education materials and evaluate materials in perspective of cultural and ethnic upbringing. (author)

  3. Study of the gamma radiation of ionium

    Energy Technology Data Exchange (ETDEWEB)

    Curie, I

    1949-12-01

    A Geiger counter study has been made of the ..gamma.. radiation of ionium. Eleven quanta of the L radiation of radium were observed for every hundred ..cap alpha.. disintegrations, and three ..gamma.. rays were found with energies of 68, 140, and 240 keV at a rate of 0.85, 0.33, 0.05 quanta, respectively, for 100 disintegrations. It is noted that the radiation spectrum of ionium as a whole is difficult to interpret. In the course of this work, the author calculated the efficiency of a thin-walled aluminum counter, both for the L radiation of radium and for ..gamma.. rays of 68 keV. The author also measured, for soft radiation, the ratio between the efficiency of a thin-walled aluminum counter and that of a similar counter lined with 0.11 mm of lead.

  4. Photoionization of atoms and small molecules using synchrotron radiation

    International Nuclear Information System (INIS)

    Ferrett, T.A.

    1986-11-01

    The combination of synchrotron radiation and time-of-flight electron spectroscopy has been used to study the photoionization dynamics of atoms (Li) and small molecules (SF 6 , SiF 4 , and SO 2 ). Partial cross sections and angular distribution asymmetry parameters have been measured for Auger electrons and photoelectrons as functions of photon energy. Emphasis is on the basic understanding of electron correlation and resonant effects as manifested in the photoemission spectra for these systems. 254 refs., 46 figs., 10 tabs

  5. Occupational radiation exposure and mortality study

    International Nuclear Information System (INIS)

    Coppock, E.; Dobson, D.; Fair, M.

    1992-06-01

    An epidemiological cohort study of some 300,000 Canadians enrolled in the National Dose Registry (NDR) is being undertaken to determine if there is excess cancer or other causes of mortality among those workers who are occupationally exposed to low levels of ionizing radiation. The results of this study may provide better understanding of the dose-response relationship for low doses of ionizing radiation and aid in the verification of risk estimates for radiation-induced cancer mortality. The Department of National Health and Welfare (DNHW) is responsible for the Registry; this study is being carried out by the Bureau of Radiation and Medical Devices (BRMD) with financial assistance and co-operation of various agencies including Statistics Canada and the Atomic Energy Control Board

  6. Development of a high-resolution soft x-ray (30--1500 eV) beamline at the Advanced Light Source and its use for the study of angle-resolved photoemission extended fine structure

    International Nuclear Information System (INIS)

    Huff, W.R.A.

    1996-02-01

    ALS Bending magnet beamline 9.3.2 is for high resolution spectroscopy, with circularly polarized light. Fixed included-angle SGM uses three gratings for 30--1500 eV photons; circular polarization is produced by an aperture for selecting the beam above or below the horizontal plane. Photocurrent from upper and lower jaws of entrance slit sets a piezoelectric drive feedback loop on the vertically deflecting mirror for stable beam. End station has a movable platform. With photomeission data from Stanford, structure of c(2x2)P/Fe(100) was determined using angle-resolved photoemission extended fine structure (ARPEFS). Multiple-scattering spherical-wave (MSSW) calculations indicate that P atoms adsorb in fourfold hollow sites 1.02A above the first Fe layer. Self-consistent-field Xα scattered wave calculation confirm that the Fe 1 -Fe 2 space is contracted for S/Fe but not for P/Fe; comparison is made to atomic N and O on Fe(100). Final-state effects on ARPEFS curves used literature data from the S 1s and 2p core levels of c(2x2)S/Ni(001); a generalized Ramsauer-Townsend splitting is present in the 1s but not 2p data. An approximate method for analyzing ARPEFS data from a non-s initial state using only the higher-ell partial wave was tested successfully. ARPEFS data from clean surfaces were collected normal to Ni(111) (3p core levels) and 5 degree off-normal from Cu(111)(3s, 3p). Fourier transforms (FT) resemble adsorbate systems, showing backscattering signals from atoms up to 4 layers below emitters. 3p FTs show scattering from 6 nearest neighbors in the same crystal layer as the emitters. MSSW calulation indicate that Cu 3p photoemission is mostly d-wave. FTs also indicate double-scattering and single-scattering from laterally distant atoms; calculations indicate that the signal is dominated by photoemission from the first 2 crystal layers

  7. Study on external beam radiation therapy

    International Nuclear Information System (INIS)

    Kim, Mi Sook; Yoo, Seoung Yul; Yoo, Hyung Jun; Ji, Young Hoon; Lee, Dong Han; Lee, Dong Hoon; Choi, Mun Sik; Yoo, Dae Heon; Lee, Hyo Nam; Kim, Kyeoung Jung

    1999-04-01

    To develop the therapy technique which promote accuracy and convenience in external radiation therapy, to obtain the development of clinical treatment methods for the global competition. The contents of the R and D were 1. structure, process and outcome analysis in radiation therapy department. 2. Development of multimodality treatment in radiation therapy 3. Development of computation using networking techniques 4. Development of quality assurance (QA) system in radiation therapy 5. Development of radiotherapy tools 6. Development of intraoperative radiation therapy (IORT) tools. The results of the R and D were 1. completion of survey and analysis about Korea radiation therapy status 2. Performing QA analysis about ICR on cervix cancer 3. Trial of multicenter randomized study on lung cancers 4. Setting up inter-departmental LAN using MS NT server and Notes program 5. Development of ionization chamber and dose-rate meter for QA in linear accelerator 6. Development on optimized radiation distribution algorithm for multiple slice 7. Implementation on 3 dimensional volume surface algorithm and 8. Implementation on adaptor and cone for IORT

  8. Study on external beam radiation therapy

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Mi Sook; Yoo, Seoung Yul; Yoo, Hyung Jun; Ji, Young Hoon; Lee, Dong Han; Lee, Dong Hoon; Choi, Mun Sik; Yoo, Dae Heon; Lee, Hyo Nam; Kim, Kyeoung Jung

    1999-04-01

    To develop the therapy technique which promote accuracy and convenience in external radiation therapy, to obtain the development of clinical treatment methods for the global competition. The contents of the R and D were 1. structure, process and outcome analysis in radiation therapy department. 2. Development of multimodality treatment in radiation therapy 3. Development of computation using networking techniques 4. Development of quality assurance (QA) system in radiation therapy 5. Development of radiotherapy tools 6. Development of intraoperative radiation therapy (IORT) tools. The results of the R and D were 1. completion of survey and analysis about Korea radiation therapy status 2. Performing QA analysis about ICR on cervix cancer 3. Trial of multicenter randomized study on lung cancers 4. Setting up inter-departmental LAN using MS NT server and Notes program 5. Development of ionization chamber and dose-rate meter for QA in linear accelerator 6. Development on optimized radiation distribution algorithm for multiple slice 7. Implementation on 3 dimensional volume surface algorithm and 8. Implementation on adaptor and cone for IORT.

  9. A radiation measurement study on cellular phone

    International Nuclear Information System (INIS)

    Mohd Yusof Mohd Ali; Rozaimah Abd Rahim; Roha Tukimin; Khairol Nizam Mohamed; Mohd Amirul Nizam Mohamad Thari; Ahmad Fadzli Ahmad Sanusi

    2007-01-01

    This paper will explain the radiation level produced by various selected cellular phone from various models and brands available in the market. The result obtained from this study will also recommend whether a cellular phone is safe for public usage or it might cause any effect on public health. Finally, a database of radiation measurement level produced by selected various cellular phone will also be developed and exhibited in this paper. (Author)

  10. Relaxation and cross section effects in valence band photoemission spectroscopy

    International Nuclear Information System (INIS)

    McFeely, F.R.

    1976-09-01

    Various problems relating to the interpretation of valence band x-ray photoemission (XPS) spectra of solids are discussed. The experiments and calculations reported herein deal with the following questions: (1) To what extent do many-body effects manifest themselves in an XPS valence band spectrum, and thus invalidate a direct comparison between the photoemission energy distribution, I(E), and the density of states, N(E), calculated on the basis of ground-state one-electron theory. (2) The effect of the binding-energy-dependent photoemission cross section on I(E) at XPS energies. (3) In favorable cases indicated by (1) and (2) we examine the effect of the interaction of the crystal field with the apparent spin-orbit splittings of core levels observed in XPS spectra. (4) The use of tight binding band structure calculations to parameterize the electronic band structure from XPS and other data is described. (5) The use of high energy angle-resolved photoemission on oriented single crystals to gain orbital symmetry information is discussed. (6) The evolution of the shape of the photoemission energy distribution (of polycrystalline Cu) as a function of photon energy from 50 less than or equal h ω less than or equal 175 is discussed

  11. Electronic structure of the gold/Bi2Sr2CaCu2O8 and gold/EuBa2Cu3O7-δ interfaces as studied by photoemission spectroscopy

    International Nuclear Information System (INIS)

    Dessau, D.S.; Shen, Z.; Wells, B.O.; Spicer, W.E.; List, R.S.; Arko, A.J.; Bartlett, R.J.; Fisk, Z.; Cheong, S.; Mitzi, D.B.; Kapitulnik, A.; Schirber, J.E.

    1990-01-01

    High-resolution photoemission has been used to probe the electronic structure of the gold/Bi 2 Sr 2 CaCu 2 O 8 and gold/EuBa 2 Cu 3 O 7-δ interface formed by a low-temperature (20 K) gold evaporation on cleaved high quality single crystals. We find that the metallicity of the EuBa 2 Cu 3 O 7-δ substrate in the near surface region (∼5 A) is essentially destroyed by the gold deposition, while the near surface region of Bi 2 Sr 2 CaCu 2 O 8 remains metallic. This has potentially wide ranging consequences for the applicability of the different types of superconductors in real devices

  12. Radiation transformation studies: are they relevant to radiation protection problems?

    International Nuclear Information System (INIS)

    Seymour, C.B.; Mothersill, C.

    1988-01-01

    Because of the difficulties of studying radio-carcinogenesis in humans, several in vitro systems are utilised. These cell transformation systems are reviewed, with particular emphasis on their relevance to human radiological protection problems. Most available systems use rodent fibroblasts. These are discussed in detail. Attention is drawn to certain artefacts which can cause problems with interpretation of such data. The relevance of these systems is questionable because of species differences, particularly concerning life span and because most human tumours are derived from epithelial cells. New epithelial culture systems and three-dimensional tissue culture methods becoming available are discussed in the light of their potential for addressing radiation protection problems. (author)

  13. DC photoemission electron guns as ERL sources

    International Nuclear Information System (INIS)

    Sinclair, Charles K.

    2006-01-01

    Very-high-voltage DC electron guns, delivering moderate duration bunches from photoemission cathodes, and followed by conventional drift bunching and acceleration, offer a practical solution for an ERL injector. In a variant of this scheme, a DC gun is placed in close proximity to a superconducting RF accelerator cavity, with few or no active elements between the gun and cavity. The principal technical challenge with such electron guns arises from field emission from the cathode electrode and its support structure. Field emission may result in voltage breakdown across the cathode-anode gap, or a punch-through failure of the insulator holding off the cathode potential, as well as lesser though still serious problems. Various means to mitigate these problems are described. The operational lifetime of high quantum efficiency photocathodes in these guns is determined by the vacuum conditions, through phenomena such as chemical poisoning and ion back-bombardment. Minimization of the field strength on electrode structures pushes high-voltage DC guns toward large dimensions and, correspondingly, large outgassing loads, but it is also true that these guns offer many opportunities for achieving excellent vacuum conditions. Good solutions to vacuum problems that had previously limited cathode lifetime have been demonstrated in recent years. Designs for DC guns presently in use and planned for the near future will be described. The parameters necessary for a 100 mA average current, very-high-voltage DC gun with a photocathode operational lifetime greater than 100 h appear to be within reach, but have yet to be demonstrated. A 1 A average current source with good cathode operational lifetime will require developments beyond the present state-of-the-art

  14. Radiation: Rational use of diagnostic imaging studies in pediatrics

    International Nuclear Information System (INIS)

    Gentile, Fernando

    2008-01-01

    The objectives of this paper are to recognize the biological effects of radiation; explain the action of ionizing radiation on the cell; list the main sources of ionizing radiation; to indicate imaging studies considering the danger of radiation; select the method of imaging saving radiation; rational use of imaging studies without repeating exams. [es

  15. Spectroscopic imaging, diffraction, and holography with x-ray photoemission

    International Nuclear Information System (INIS)

    1992-02-01

    X-ray probes are capable of determining the spatial structure of an atom in a specific chemical state, over length scales from about a micron all the way down to atomic resolution. Examples of these probes include photoemission microscopy, energy-dependent photoemission diffraction, photoelectron holography, and X-ray absorption microspectroscopy. Although the method of image formation, chemical-state sensitivity, and length scales can be very different, these X-ray techniques share a common goal of combining a capability for structure determination with chemical-state specificity. This workshop will address recent advances in holographic, diffraction, and direct imaging techniques using X-ray photoemission on both theoretical and experimental fronts. A particular emphasis will be on novel structure determinations with atomic resolution using photoelectrons

  16. Spectroscopic imaging, diffraction, and holography with x-ray photoemission

    Energy Technology Data Exchange (ETDEWEB)

    1992-02-01

    X-ray probes are capable of determining the spatial structure of an atom in a specific chemical state, over length scales from about a micron all the way down to atomic resolution. Examples of these probes include photoemission microscopy, energy-dependent photoemission diffraction, photoelectron holography, and X-ray absorption microspectroscopy. Although the method of image formation, chemical-state sensitivity, and length scales can be very different, these X-ray techniques share a common goal of combining a capability for structure determination with chemical-state specificity. This workshop will address recent advances in holographic, diffraction, and direct imaging techniques using X-ray photoemission on both theoretical and experimental fronts. A particular emphasis will be on novel structure determinations with atomic resolution using photoelectrons.

  17. Einstein's photoemission emission from heavily-doped quantized structures

    CERN Document Server

    Ghatak, Kamakhya Prasad

    2015-01-01

    This monograph solely investigates the Einstein's Photoemission(EP) from Heavily Doped(HD) Quantized Structures on the basis of newly formulated electron dispersion laws. The materials considered are quantized structures of HD non-linear optical, III-V, II-VI, Ge, Te, Platinum Antimonide, stressed materials, GaP, Gallium Antimonide, II-V, Bismuth Telluride together with various types of HD superlattices and their Quantized counterparts respectively. The EP in HD opto-electronic materials and their nanostructures is studied in the presence of strong light waves and intense electric fields  that control the studies of such quantum effect devices. The suggestions for the experimental determinations of different important physical quantities in HD 2D and 3D materials  and the importance of measurement of band gap in HD optoelectronic materials under intense built-in electric field in nano devices and strong external photo excitation (for measuring   physical properties in the presence of intense light waves w...

  18. Study on radiation-inducible genes

    International Nuclear Information System (INIS)

    Lim, Sang Yong; Kim, Dong Ho; Joe, Min Ho; Song, Hyu Npa

    2012-01-01

    Transcription of previously identified radiation-inducible genes, uscA and cyoA, was examined responding to radiation. The putative promoter regions of both genes were cloned into pRS415 vector containing lacZ, and the core promoter region necessary for radiation response were determined through promoter deletion method. To investigate the role of uscA, which is assumed to be small RNA related with radiation response, a deletion mutant strain of uscA was constructed. However, uscA deletion did not affect bacterial survival against radiation exposure. The use of bacteria as anticancer agents has attracted interest. In this study, we tried to develop tumor targeting bacteria in which the radiation-inducible promoter activate a transgene encoding a cytotoxic protein. For outward secretion of anticancer protein produced inside bacteria, the N-terminal 140 amino acid of SspH1 was found to function as a secretion signal peptide. To create an attenuated tumor-targeting bacteria, Salmonella ptsI mutant strain was constructed, and we found that its virulence decreased. Finally, the tumor-targeting ability of ptsI mutant was verified by the use of in-vivo imaging analysis

  19. Study on radiation-inducible genes

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Sang Yong; Kim, Dong Ho; Joe, Min Ho; Song, Hyu Npa

    2012-01-15

    Transcription of previously identified radiation-inducible genes, uscA and cyoA, was examined responding to radiation. The putative promoter regions of both genes were cloned into pRS415 vector containing lacZ, and the core promoter region necessary for radiation response were determined through promoter deletion method. To investigate the role of uscA, which is assumed to be small RNA related with radiation response, a deletion mutant strain of uscA was constructed. However, uscA deletion did not affect bacterial survival against radiation exposure. The use of bacteria as anticancer agents has attracted interest. In this study, we tried to develop tumor targeting bacteria in which the radiation-inducible promoter activate a transgene encoding a cytotoxic protein. For outward secretion of anticancer protein produced inside bacteria, the N-terminal 140 amino acid of SspH1 was found to function as a secretion signal peptide. To create an attenuated tumor-targeting bacteria, Salmonella ptsI mutant strain was constructed, and we found that its virulence decreased. Finally, the tumor-targeting ability of ptsI mutant was verified by the use of in-vivo imaging analysis.

  20. Time-resolved photoemission micro-spectrometer using higher-order harmonics of Ti:sapphire laser

    International Nuclear Information System (INIS)

    Azuma, J.; Kamada, M.; Kondo, Y.

    2004-01-01

    Full text: A new photoemission spectrometer is under construction for the photoemission microscopy and the time-resolved pump- probe experiment. The higher order harmonics of the Ti:sapphire laser is used as the light source of the VUV region in this system. Because the fundamental laser is focused tightly into the rare gas jet to generate the higher order harmonics, the spot size of the laser, in other words, the spot size of the VUV light source is smaller than a few tens of micrometer. This smallness of the spot size has advantage for the microscopy. In order to compensate the low flux of the laser harmonics, a multilayer-coated schwaltzshild optics was designed. The multilayers play also as the monochromatic filter. The spatial resolution of this schwaltzshild system is found to be less than 1 micrometer by the ray-tracing calculations. A main chamber of the system is equipped with a time-of-flight energy analyzer to improve the efficiency of the electron detection. The main chamber and the gas chamber are separated by a differential pumping chamber and a thin Al foil. The system is designed for the study of the clean surface. It will be capable to perform the sub-micron photoemission microscopy and the femto-second pump-probe photoemission study for the various photo-excited dynamics on clean surfaces

  1. Radiation-induced heart injury. Radiopathological study

    Energy Technology Data Exchange (ETDEWEB)

    Suzuki, Y; Niibe, H [Gunma Univ., Maebashi (Japan). School of Medicine

    1975-11-01

    In order to identify radiation-induced heart injury and to differentiate it from heart disease, an attempt was made to clarify post-irradiation heart injury by investigating the histological changes which occur during the interval between the irradiation and the time of demonstrable histological changes. A study was made of 83 autopsies in which most of the primary neoplasms were breast cancers, lung cancers and mediastinal tumors. In 43 of these autopsies the heart had been irradiated. Sixty eight dd-strain mice were also used for microautoradiographic study. Histological changes in the heart were observed in 27 of the 43 cases receiving irradiation. The limit of the tolerance dose to the heart for indicating histological changes was 1220 ret in humans. The latent period without histological changes was 2.7 months after initiation of radiation therapy. Greater heart injury was observed after re-irradiation or after the combined therapy of radiation and chemotherapy especially mitomycin (MMC). The histological findings after treatment with MMC were similar to those of radiation-induced heart injury. Results of the study indicate that the damage is secondary to radiation-induced changes of the vascula connective tissue.

  2. Clinical and experimental studies on radiation proctitis

    International Nuclear Information System (INIS)

    Honke, Yoshifumi

    1988-01-01

    Clinical and experimental studies were performed to clarify the mechanism of developing radiation proctitis. The results were as follows; (1) In the clinical study with 38 uterine cervix cancer patients, who received radiotherapy, diarrhea was observed in 44.7% at the acute stage, while rectal bleeding in 36.7% about 1 year after radiation. However, no clinical correlation was observed between diarrhea and rectal bleeding. (2) Colon fiberscopic examination revealed little change at the acute stage. However, erosion, ulcer and remarkable redness were found at the late stage. By the magnified fiberscope, unit degeneration was found in 72.8% at the acute stage. (3) Concerning the histopathological changes, edema and inflammatory change were observed immediately after irradiation. Fibrosis was observed in 83.3% at the late stage. (4) The number of the immunoglobulin containing cells decreased by radiation. However, its recovered as time passed after radiation. (5) In experimental study with rats by microangiography, there were ramarkable changes of the small vessels, such as bending, tortuosity and capillary hyperplasia at the acute stage. However, these changes returned to normal soon. At the late stage, decreased number of blood vessels were observed. The above results indicated that rectal bleeding after exposure to radiation are developed by secondary circulation abnormality caused by fibrosis of the perivascular tissues. (author) 52 refs

  3. Angle-resolved photoemission spectroscopy with quantum gas microscopes

    Science.gov (United States)

    Bohrdt, A.; Greif, D.; Demler, E.; Knap, M.; Grusdt, F.

    2018-03-01

    Quantum gas microscopes are a promising tool to study interacting quantum many-body systems and bridge the gap between theoretical models and real materials. So far, they were limited to measurements of instantaneous correlation functions of the form 〈O ̂(t ) 〉 , even though extensions to frequency-resolved response functions 〈O ̂(t ) O ̂(0 ) 〉 would provide important information about the elementary excitations in a many-body system. For example, single-particle spectral functions, which are usually measured using photoemission experiments in electron systems, contain direct information about fractionalization and the quasiparticle excitation spectrum. Here, we propose a measurement scheme to experimentally access the momentum and energy-resolved spectral function in a quantum gas microscope with currently available techniques. As an example for possible applications, we numerically calculate the spectrum of a single hole excitation in one-dimensional t -J models with isotropic and anisotropic antiferromagnetic couplings. A sharp asymmetry in the distribution of spectral weight appears when a hole is created in an isotropic Heisenberg spin chain. This effect slowly vanishes for anisotropic spin interactions and disappears completely in the case of pure Ising interactions. The asymmetry strongly depends on the total magnetization of the spin chain, which can be tuned in experiments with quantum gas microscopes. An intuitive picture for the observed behavior is provided by a slave-fermion mean-field theory. The key properties of the spectra are visible at currently accessible temperatures.

  4. Exploring the magnetic and organic microstructures with photoemission electron microscope

    International Nuclear Information System (INIS)

    Wei, D.H.; Chan, Yuet-Loy; Hsu, Yao-Jane

    2012-01-01

    Highlights: ► PEEM with polarized photon enables additional image contrasts and physical insights. ► XMCD-based images reveal the shape-dependent domains in Ni80Fe20 microstructures. ► XLD-based images confirm the success of molecular orientation controls. ► The two interfaces in Co–Pn–Co structures are magnetically and chemically different. -- Abstract: We present photoemission electron microscopy (PEEM) studies on geometrically constrained ferromagnetic, organic, and organics–ferromagnet hybrid structures. Powered by an elliptically polarized undulator, the PEEM at Taiwan Light Source (TLS) is capable of recording polarization enhanced X-ray images and has been employed to examine the domain configurations in a lithographically patterned permalloy film as well as the orientations of pentacene molecules adsorbed on self-assembled monolayers (SAMs) modified gold surfaces. In addition, magnetic images acquired on cobalt/pentacene and pentacene/cobalt bilayers reveal that in hybrid structures the order of thin film deposition can lead to distinct domain configurations. Spectroscopic evidence further suggests that there is significant orbital hybridization at the interface where metallic cobalt was deposited directly on organic pentacene.

  5. Exploring the magnetic and organic microstructures with photoemission electron microscope

    Energy Technology Data Exchange (ETDEWEB)

    Wei, D.H., E-mail: dhw@nsrrc.org.tw [National Synchrotron Radiation Research Center, Hsinchu Science Park, 30076 Hsinchu, Taiwan (China); Chan, Yuet-Loy; Hsu, Yao-Jane [National Synchrotron Radiation Research Center, Hsinchu Science Park, 30076 Hsinchu, Taiwan (China)

    2012-10-15

    Highlights: Black-Right-Pointing-Pointer PEEM with polarized photon enables additional image contrasts and physical insights. Black-Right-Pointing-Pointer XMCD-based images reveal the shape-dependent domains in Ni80Fe20 microstructures. Black-Right-Pointing-Pointer XLD-based images confirm the success of molecular orientation controls. Black-Right-Pointing-Pointer The two interfaces in Co-Pn-Co structures are magnetically and chemically different. -- Abstract: We present photoemission electron microscopy (PEEM) studies on geometrically constrained ferromagnetic, organic, and organics-ferromagnet hybrid structures. Powered by an elliptically polarized undulator, the PEEM at Taiwan Light Source (TLS) is capable of recording polarization enhanced X-ray images and has been employed to examine the domain configurations in a lithographically patterned permalloy film as well as the orientations of pentacene molecules adsorbed on self-assembled monolayers (SAMs) modified gold surfaces. In addition, magnetic images acquired on cobalt/pentacene and pentacene/cobalt bilayers reveal that in hybrid structures the order of thin film deposition can lead to distinct domain configurations. Spectroscopic evidence further suggests that there is significant orbital hybridization at the interface where metallic cobalt was deposited directly on organic pentacene.

  6. Correlation, temperature and disorder: Recent developments in the one-step description of angle-resolved photoemission

    Science.gov (United States)

    Braun, Jürgen; Minár, Ján; Ebert, Hubert

    2018-04-01

    Various apparative developments extended the potential of angle-resolved photoemission spectroscopy tremendously during the last two decades. Modern experimental arrangements consisting of new photon sources, analyzers and detectors supply not only extremely high angle and energy resolution but also spin resolution. This provides an adequate platform to study in detail new materials like low-dimensional magnetic structures, Rashba systems, topological insulator materials or high TC superconductors. The interest in such systems has grown enormously not only because of their technological relevance but even more because of exciting new physics. Furthermore, the use of photon energies from few eV up to several keV makes this experimental technique a rather unique tool to investigate the electronic properties of solids and surfaces. The following article reviews the corresponding recent theoretical developments in the field of angle-resolved photoemission with a special emphasis on correlation effects, temperature and relativistic aspects. The most successful theoretical approach to deal with angle-resolved photoemission is the so-called spectral function or one-step formulation of the photoemission process. Nowadays, the one-step model allows for photocurrent calculations for photon energies ranging from a few eV to more than 10 keV, to deal with arbitrarily ordered and disordered systems, to account for finite temperatures, and considering in addition strong correlation effects within the dynamical mean-field theory or similar advanced approaches.

  7. Principle and application of low energy inverse photoemission spectroscopy: A new method for measuring unoccupied states of organic semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Yoshida, Hiroyuki, E-mail: hyoshida@chiba-u.jp

    2015-10-01

    Highlights: • Principle of low energy inverse photoemission spectroscopy is described. • Instruments including electron sources and photon detectors are shown. • Recent results about organic devices and fundamental studies are reviewed. • Electron affinities of typical organic semiconductors are compiled. - Abstract: Information about the unoccupied states is crucial to both fundamental and applied physics of organic semiconductors. However, there were no available experimental methods that meet the requirement of such research. In this review, we describe a new experimental method to examine the unoccupied states, called low-energy inverse photoemission spectroscopy (LEIPS). An electron having the kinetic energy lower than the damage threshold of organic molecules is introduced to a sample film, and an emitted photon in the near-ultraviolet range is detected with high resolution and sensitivity. Unlike the previous inverse photoemission spectroscopy, the sample damage is negligible and the overall resolution is a factor of two improved to 0.25 eV. Using LEIPS, electron affinity of organic semiconductor can be determined with the same precision as photoemission spectroscopy for ionization energy. The instruments including an electron source and photon detectors as well as application to organic semiconductors are presented.

  8. Principle and application of low energy inverse photoemission spectroscopy: A new method for measuring unoccupied states of organic semiconductors

    International Nuclear Information System (INIS)

    Yoshida, Hiroyuki

    2015-01-01

    Highlights: • Principle of low energy inverse photoemission spectroscopy is described. • Instruments including electron sources and photon detectors are shown. • Recent results about organic devices and fundamental studies are reviewed. • Electron affinities of typical organic semiconductors are compiled. - Abstract: Information about the unoccupied states is crucial to both fundamental and applied physics of organic semiconductors. However, there were no available experimental methods that meet the requirement of such research. In this review, we describe a new experimental method to examine the unoccupied states, called low-energy inverse photoemission spectroscopy (LEIPS). An electron having the kinetic energy lower than the damage threshold of organic molecules is introduced to a sample film, and an emitted photon in the near-ultraviolet range is detected with high resolution and sensitivity. Unlike the previous inverse photoemission spectroscopy, the sample damage is negligible and the overall resolution is a factor of two improved to 0.25 eV. Using LEIPS, electron affinity of organic semiconductor can be determined with the same precision as photoemission spectroscopy for ionization energy. The instruments including an electron source and photon detectors as well as application to organic semiconductors are presented.

  9. Cobalt-60 radiation leukemogenesis studies

    International Nuclear Information System (INIS)

    Kawakami, T.G.; Cain, G.R.; Taylor, N.J.; Shifrine, M.; Goldman, M.

    1985-01-01

    Canine myeloblastic leukemia cells are not metabolically a homogeneous population. Isotopic ( 3 H-thymidine) and immunofluorescent labelling of blastic leukemia cells for DNA synthesis indicated that active DNA synthesis occurred in small populations (10-30%) while the remaining cells were at maturation arrest. This characteristic of reduced DNA synthesis is common to granulocytic, monocytic and megakaryoblastic leukemia. Based on allo-transplantation studies, malignancy of leukemic cells is a constitutive property of the cells. A protein factor produced by the leukemic cell is responsible for maturation arrest. Based on SDS-polyacrylamide gel electrophoresis, the maturation arrest factor consist of several peptides. Long-term cultures of leukemic cells have been established. Molecular studies for malignant transformation are now underway. 3 figures, 2 tables

  10. Study on radiation-inducible genes

    International Nuclear Information System (INIS)

    Lim, Sang Yong; Kim, Dong Ho; Joe, Min Ho; Park, Hae Jun; Song, Hyu Npa

    2012-01-01

    Radiation-inducible genes of E. coli, which is a model strain for bacterial study, and Salmonella, which is a typical strain for pathogenic bacteria were compared through omic analysis. Heat shock response genes and prophage genes were induced by radiation in Salmonella, not in E. coli. Among prophage genes tested, STM2628 showed the highest activation by radiation, and approximately 1 kb promoter region was turned out to be necessary for radiation response. To screen an artificial promoter showing activation by 2 Gy, the high-throughput screening method using fluorescent MUG substrate was established. The use of bacteria as anticancer agents has attracted interest. In this study, we tried to develop tumor targeting bacteria in which the radiation-inducible promoter activate a transgene encoding a cytotoxic protein. To do this, a tumor-targeting hfq Salmonella mutant strain was constructed, and we found that its virulence decreased. For outward secretion of anticancer protein produced inside bacteria, the signal peptide of SspH1 was determined and the signal peptide was proven to be able to secrete an anticancer protein. Tumor xenograft mouse model was secured, which can be used for efficiency evaluation of bacterial tumor therapy

  11. Study on radiation-inducible genes

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Sang Yong; Kim, Dong Ho; Joe, Min Ho; Park, Hae Jun; Song, Hyu Npa

    2012-01-15

    Radiation-inducible genes of E. coli, which is a model strain for bacterial study, and Salmonella, which is a typical strain for pathogenic bacteria were compared through omic analysis. Heat shock response genes and prophage genes were induced by radiation in Salmonella, not in E. coli. Among prophage genes tested, STM2628 showed the highest activation by radiation, and approximately 1 kb promoter region was turned out to be necessary for radiation response. To screen an artificial promoter showing activation by 2 Gy, the high-throughput screening method using fluorescent MUG substrate was established. The use of bacteria as anticancer agents has attracted interest. In this study, we tried to develop tumor targeting bacteria in which the radiation-inducible promoter activate a transgene encoding a cytotoxic protein. To do this, a tumor-targeting hfq Salmonella mutant strain was constructed, and we found that its virulence decreased. For outward secretion of anticancer protein produced inside bacteria, the signal peptide of SspH1 was determined and the signal peptide was proven to be able to secrete an anticancer protein. Tumor xenograft mouse model was secured, which can be used for efficiency evaluation of bacterial tumor therapy.

  12. Prompt radiation activation analysis, (1) Theoretical study

    International Nuclear Information System (INIS)

    EL Barouni, A. M.; Araddad, S. Y.; Mosbah, D. S.; Elfakhri, S. M.; Rateb, J. M.; Benghzail, M. A.

    2004-01-01

    The measurement of the prompt γ following neutron capture in the reaction has been extensively developed. In this method the gamma-ray intensity is depended only upon the radiative capture cross-section and not upon the half-life of the product nucleus. The prompt gamma-ray activation analysis method stems from the radiative capture process which results in the decay of the compound nucleus by the emission of characteristic gamma radiation, either as a single photon with kinetic energy equal to the excitation energy less the recoil energy or, more likely, by a cascade of two or more photons with the same energy. The equations and the computer program required to calculate the yield, the intensity and the K χ emission probability per disintegration, are given in this study.(author)

  13. Photoelectron emission as a tool to assess dose of electron radiation received by ZrO2:PbS films

    International Nuclear Information System (INIS)

    Krumpane, Diana; Dekhtyar, Yury; Surkova, Indra; Romanova, Marina

    2013-01-01

    PbS nano dots embedded in ZrO 2 thin film matrix (ZrO 2 :PbS films) were studied for application in nanodosimetry of electron radiation used in radiation therapy. ZrO 2 :PbS films were irradiated with 9 MeV electron radiation with doses 3, 7 and 10 Gy using medical linear accelerator. Detection of the dosimetric signal was made by measuring and comparing photoelectron emission current from ZrO 2 :PbS films before and after irradiation. It was found that electron radiation decreased intensity of photoemission current from the films. Derivatives of the photoemission spectra were calculated and maximums at photon energies 5.65 and 5.75 eV were observed. Amplitude of these maximums decreased after irradiation with electrons. Good linear correlation was found between the relative decrease of the intensity of these maximums and dose of electron radiation. Observed changes in photoemission spectra from ZrO 2 :PbS films under influence of electron radiation suggested that the films may be considered to be effective material for electron radiation dosimetry. Photoelectron emission is a tool that allows to read the signal from such dosimeter. (authors)

  14. Radiation damage studies of nuclear structural materials

    International Nuclear Information System (INIS)

    Barat, P.

    2012-01-01

    Maximum utilization of fuel in nuclear reactors is one of the important aspects for operating them economically. The main hindrance to achieve this higher burnups of nuclear fuel for the nuclear reactors is the possibility of the failure of the metallic core components during their operation. Thus, the study of the cause of the possibility of failure of these metallic structural materials of nuclear reactors during full power operation due to radiation damage, suffered inside the reactor core, is an important field of studies bearing the basic to industrial scientific views.The variation of the microstructure of the metallic core components of the nuclear reactors due to radiation damage causes enormous variation in the structure and mechanical properties. A firm understanding of this variation of the mechanical properties with the variation of microstructure will serve as a guide for creating new, more radiation-tolerant materials. In our centre we have irradiated structural materials of Indian nuclear reactors by charged particles from accelerator to generate radiation damage and studied the some aspects of the variation of microstructure by X-ray diffraction studies. Results achieved in this regards, will be presented. (author)

  15. Time-resolved magnetic imaging in an aberration-corrected, energy-filtered photoemission electron microscope

    International Nuclear Information System (INIS)

    Nickel, F.; Gottlob, D.M.; Krug, I.P.; Doganay, H.; Cramm, S.; Kaiser, A.M.; Lin, G.; Makarov, D.; Schmidt, O.G.

    2013-01-01

    We report on the implementation and usage of a synchrotron-based time-resolving operation mode in an aberration-corrected, energy-filtered photoemission electron microscope. The setup consists of a new type of sample holder, which enables fast magnetization reversal of the sample by sub-ns pulses of up to 10 mT. Within the sample holder current pulses are generated by a fast avalanche photo diode and transformed into magnetic fields by means of a microstrip line. For more efficient use of the synchrotron time structure, we developed an electrostatic deflection gating mechanism capable of beam blanking within a few nanoseconds. This allows us to operate the setup in the hybrid bunch mode of the storage ring facility, selecting one or several bright singular light pulses which are temporally well-separated from the normal high-intensity multibunch pulse pattern. - Highlights: • A new time-resolving operation mode in photoemission electron microscopy is shown. • Our setup works within an energy-filtered, aberration-corrected PEEM. • A new gating system for bunch selection using synchrotron radiation is developed. • An alternative magnetic excitation system is developed. • First tr-imaging using an energy-filtered, aberration-corrected PEEM is shown

  16. Practical Photoemission Characterization Of Molecular Films And Related Interfaces

    International Nuclear Information System (INIS)

    Ivanco, J.

    2013-01-01

    Even though the term ‘organic electronics’ evokes rather organic devices, a significant part of its scope deals with physical properties of ‘active elements’ such as organic films and interfaces. Examination of the film growth and the evolution of the interface formation are particularly needful for the understanding a mechanism controlling their final properties. Performing such experiments in an ultra-high vacuum allows both to ‘stretch’ the time scale for pseudo real-time observations and to control properties of the probed systems on the atomic level. Photoemission technique probes directly electronic and chemical structure and it has thereby established among major tools employed in the field.This review primarily focuses to electronic properties of oligomeric molecular films and their interfaces examined by photoemission. Yet, it does not aspire after a complete overview on the topic; it rather aims to otherwise standard issues encountered at the photoemission characterization and analysis of the organic materials, though requiring to consider particularities of molecular films in terms of the growth, electronic properties, and their characterization and analysis. In particular, the fundamental electronic parameters of molecular films such as the work function, the ionization energy, and the interfacial energy level alignment, and their interplay, will be pursued with considering often neglected influence of the molecular orientation. Further, the implication on the band bending in molecular films based on photoemission characterization, and a model on the driving mechanism for the interfacial energy level alignment will be addressed. (author)

  17. Theory of angle-resolved photoemission from the cuprate superconductors

    International Nuclear Information System (INIS)

    Hedegard, P.; Pedersen, M.B.

    1990-01-01

    We show that the photoemission spectrum for an RVB state with bosonic spins and fermionic charges consists of a peak on top of a broad background. The 'Fermi surface' corresponds to hole pockets around certain k-vectors. The theoretical predictions are compared with the available experimental data, and with the results obtained by other approaches. (orig.)

  18. SiO mass spectrometry and Si-2p photoemission spectroscopy for the study of oxidation reaction dynamics of Si(001) surface by supersonic O sub 2 molecular beams under 1000K

    CERN Document Server

    Teraoka, Y; Moritani, K

    2003-01-01

    The Si sup 1 sup 8 O desorption yield was measured in the Si(001) surface temperature region from 900K to 1300K at the sup 1 sup 8 O sub 2 incident energies of 0.7eV, 2.2eV and 3.3eV. The Si sup 1 sup 8 O desorption yield in a surface temperature region higher than 1000K increased with increasing incident energy, indicating the incident-energy-induced oxidation and the variation of angular distribution of Si sup 1 sup 8 O desorption. Inversely, the Si sup 1 sup 8 O desorption yield decreased with increasing incident energy in the region from 900K to 1000K, indicating the coexistence of the passive and the active oxidation. In order to clarify the reaction mechanisms of the later phenomenon, real-time in-situ Si-2p photoemission spectroscopy has been performed. The obtained Si-2p spectra showed the variation of the oxide-nuclei quality from the sub-oxide-rich structure to the SiO sub 2 -rich structure. The formation of the SiO sub 2 structure suppresses the SiO desorption due to the enhanced O sub 2 sticking a...

  19. Dosimetry studies during breast cancer radiation treatment

    International Nuclear Information System (INIS)

    Ahmed, M. O. M.

    2005-06-01

    Previous studies indicated that breast cancer is wildly spread especially in women as compared to men. It is increased after an age of thirty five years in women so it is important to study the effect of exposure to the radiation on the intact breast during the treatment of the breast suffering from cancer. In this work the scattered doses for the intact breast during the treatment of the breast suffering from cancer were measured and also the probability of inducing cancer in it is also discussed. The study was performed for a group of patients composed of twenty five females. Also the backscattered doses to the intact breast were measured for thirteen female patients. During the treatment using gamma rays from Co-60 source the two tangential fields (lateral and medial) were selected for the measurements. The results of exposure to gamma radiation for the lateral and medial fields showed that the mean scattered and backscattered doses to the intact breast were (241.26 cGY,47.49 cGY) and (371.6 cGY,385.4 cGY), respectively. Beside that the somatic risk of induced cancer to the intact breast was found to be (6 .1X10 -3 ,1.2X10 -3 ) and (9.29X10 -3 , 9.63X10 -3 ), respectively. From the results obtained it was concluded that the intact breast received small amounts of radiation doses which may lead to breast cancer for the healthy breast. The recommendations from the present study are to take care of radiation protection to the patient, and also to take care of the patient treatment conditions like temperature, pressure and humidity during the radiation exposure.(Author)

  20. Photoemission study of absorption mechanisms in Bi2.0Sr1.8Ca0.8La0.3Cu2.1O8+δ, BaBiO3, and Nd1.85Ce0.15CuO4

    International Nuclear Information System (INIS)

    Lindberg, P.A.P.; Shen, Z.; Wells, B.O.; Dessau, D.S.; Ellis, W.P.; Borg, A.; Kang, J.; Mitzi, D.B.; Lindau, I.

    1989-01-01

    Photoemission measurements in the constant-final-state (absorption) mode were performed on three different classes of high-temperature superconductors Bi 2.0 Sr 1.8 Ca 0.8 La 0.3 Cu 2.1 O 8+δ , BaBiO 3 , and Nd 1.85 Ce 0.15 CuO 4 using synchrotron radiation from 20 to 200 eV. Absorption signals from all elements but Ce are identified. The results firmly show that the Bi 6s electrons are more delocalized in BaBiO 3 than in Bi 2.0 Sr 1.8 Ca 0.8 La 0.3 Cu 2.1 O 8+δ , in agreement with the results of band-structure calculations. Differences in the absorption signals due to O and Bi excitations between BaBiO 3 and Bi 2.0 Sr 1.8 Ca 0.8 La 0.3 Cu 2.1 O 8+δ are discussed. Delayed absorption onsets attributed to giant resonances (Ba 4d→4f, La 4d→4f, and Nd 4d→4f transitions) are also reported

  1. European studies on occupational radiation exposure - ESOREX

    International Nuclear Information System (INIS)

    Petrova, K.; Frasch, G.

    2005-01-01

    Full text: The ESOREX project was initiated by the European Commission in 1997. The objectives of this European study are: to provide the European Commission and the national competent radiation protection authorities with reliable information on how personal radiation monitoring, reporting and recording of dosimetric results is organized in European countries; to collect reliable and directly comparable data on individual and collective radiation exposure in all occupational sectors where radiation workers are employed. The information about the monitoring of occupational radiation exposure, the levels of individual personal doses of workers in the different work sectors, the changes and trends of these doses over a period of several years and the international comparison of these data are useful information for many stakeholders. The survey consists of two parts. Part I surveys how radiation protection monitoring, recording and reporting is arranged within each of the 30 European countries. Part II collects doses from occupational exposure of classified workers in the participating countries. For each country, information is provided on the number of workers in defined work categories and how annual individual personal doses are distributed. The summary and the conclusions provide tentative recommendations for harmonizing modifications of some of the national monitoring, reporting and recording arrangements. In all ESOREX studies a beneficial, effective and extensive information base about thirty European states has been created. The studies resulted in country reports describing the legislative, administrative, organizational and technical aspects of the national dose monitoring and recording systems for occupationally radiation exposed workers. These reports are standardized, i.e. they have as far as possible an internationally comparable structure. The dose distributions of the radiation workers and the annual average and collective doses in the various work

  2. Study on radiation-responsive epigenomes

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jin Hong; Chung, Byung Yeop; Lee, Seung Sik; Moon, Yu Ran; Lee, Min Hee; Kim, Ji Hong [KAERI, Daejeon (Korea, Republic of)

    2011-01-15

    The purpose of this project is development of world-class headspring techniques of biological science for application of plant genomes/epigenomes through study on radiation- responsive epigenomes and improvement of the national competitiveness in the field of fundamental technology for biological science and industry. Research scope includes 1) Investigation of radiation-responsive epigenomes and elucidation of their relation with phenotypes, 2) Elucidation of interaction and transcription control of epigenomes and epigenetic regulators using ionizing radiation (IR), 3) Investigation of epigenome-mediated traits in plant development, differentiation and antioxidant defense using IR, and 4) Development of application techniques of radiation-responsive epigenomes for eco-monitoring and molecular breeding. Main results are as follow: Setup of conditions for chromatin immunoprecipitation in irradiated plants: investigation of aberrations in DNA methylation after treatment with different IR: elucidation of responses of epigenetic regulators to gamma rays (GR): investigation of aberrations in GR-responsive epigenetic regulators at different developmental stages: elucidation of interactive aberrations of epigenomes and epigenetic regulators after treatment of GR: comparison of functional genomes after treatment of GR or H{sub 2}O{sub 2}: elucidation of relation of epigenomes with GR-induced delay in senescence: elucidation of relation of epigenomes with GR-induced aberrations in pigment metabolism: comparison of antioxidant defense in epigenetic mutants: investigation of senescence-associated changes in epigenomes: investigation of senescence-associated changes in epigenetic regulators: comparison of aberrations in epigenomes at different dose of GR for mutation.

  3. Study on radiation-responsive epigenomes

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jin Hong; Lee, Seung Sik; Bae, Hyung Woo; Kim, Ji Hong; Kim, Ji Eun; Cho, Eun Ju; Lee, Min Hee; Moon, Yu Ran [KAERI, Daejeon (Korea, Republic of)

    2012-01-15

    The purpose of this project is development of world-class headspring techniques of biological science for application of plant genomes/epigenomes through study on radiation- responsive epigenomes and improvement of the national competitiveness in the field of fundamental technology for biological science and industry. Research scope includes 1) Investigation of radiation-responsive epigenomes and elucidation of their relation with phenotypes, 2) Elucidation of interaction and transcription control of epigenomes and epigenetic regulators using IR, 3) Investigation of epigenome-mediated traits in plant development, differentiation and antioxidant defense using IR, and 4) Development of application techniques of radiation-responsive epigenomes for eco-monitoring and molecular breeding. Main results are as follow: practical application of ChIP in GR-treated Arabidopsis using anti-histone antibodies: mapping of DNA methylomes associated with GR-responsive transcriptomes: setup of methylated DNA quantification using HPLC: elucidation of aberrations in epigenetic regulation induced by low-dose GR using gamma phytotron: comparison of gene expression of histone-modifying enzymes after treatment of GR: elucidation of transcriptomes and physiological alterations associated with delayed senescence of drd1-6 mutant: comparison of gene expression of DNA methylation-related enzymes in GR-treated rice callus and Arabidopsis: investigation of germination capacity, low-temperature, salinity and drought stress-resistance in drd1-6 epigenetic mutant: investigation of aberrations in DNA methylation depending on dose rates of gamma radiation

  4. Study on radiation-responsive epigenomes

    International Nuclear Information System (INIS)

    Kim, Jin Hong; Lee, Seung Sik; Bae, Hyung Woo; Kim, Ji Hong; Kim, Ji Eun; Cho, Eun Ju; Lee, Min Hee; Moon, Yu Ran

    2012-01-01

    The purpose of this project is development of world-class headspring techniques of biological science for application of plant genomes/epigenomes through study on radiation- responsive epigenomes and improvement of the national competitiveness in the field of fundamental technology for biological science and industry. Research scope includes 1) Investigation of radiation-responsive epigenomes and elucidation of their relation with phenotypes, 2) Elucidation of interaction and transcription control of epigenomes and epigenetic regulators using IR, 3) Investigation of epigenome-mediated traits in plant development, differentiation and antioxidant defense using IR, and 4) Development of application techniques of radiation-responsive epigenomes for eco-monitoring and molecular breeding. Main results are as follow: practical application of ChIP in GR-treated Arabidopsis using anti-histone antibodies: mapping of DNA methylomes associated with GR-responsive transcriptomes: setup of methylated DNA quantification using HPLC: elucidation of aberrations in epigenetic regulation induced by low-dose GR using gamma phytotron: comparison of gene expression of histone-modifying enzymes after treatment of GR: elucidation of transcriptomes and physiological alterations associated with delayed senescence of drd1-6 mutant: comparison of gene expression of DNA methylation-related enzymes in GR-treated rice callus and Arabidopsis: investigation of germination capacity, low-temperature, salinity and drought stress-resistance in drd1-6 epigenetic mutant: investigation of aberrations in DNA methylation depending on dose rates of gamma radiation

  5. Study on radiation-responsive epigenomes

    International Nuclear Information System (INIS)

    Kim, Jin Hong; Chung, Byung Yeop; Lee, Seung Sik; Moon, Yu Ran; Lee, Min Hee; Kim, Ji Hong

    2011-01-01

    The purpose of this project is development of world-class headspring techniques of biological science for application of plant genomes/epigenomes through study on radiation- responsive epigenomes and improvement of the national competitiveness in the field of fundamental technology for biological science and industry. Research scope includes 1) Investigation of radiation-responsive epigenomes and elucidation of their relation with phenotypes, 2) Elucidation of interaction and transcription control of epigenomes and epigenetic regulators using ionizing radiation (IR), 3) Investigation of epigenome-mediated traits in plant development, differentiation and antioxidant defense using IR, and 4) Development of application techniques of radiation-responsive epigenomes for eco-monitoring and molecular breeding. Main results are as follow: Setup of conditions for chromatin immunoprecipitation in irradiated plants: investigation of aberrations in DNA methylation after treatment with different IR: elucidation of responses of epigenetic regulators to gamma rays (GR): investigation of aberrations in GR-responsive epigenetic regulators at different developmental stages: elucidation of interactive aberrations of epigenomes and epigenetic regulators after treatment of GR: comparison of functional genomes after treatment of GR or H 2 O 2 : elucidation of relation of epigenomes with GR-induced delay in senescence: elucidation of relation of epigenomes with GR-induced aberrations in pigment metabolism: comparison of antioxidant defense in epigenetic mutants: investigation of senescence-associated changes in epigenomes: investigation of senescence-associated changes in epigenetic regulators: comparison of aberrations in epigenomes at different dose of GR for mutation

  6. Vacancy formation in MoO3: hybrid density functional theory and photoemission experiments

    KAUST Repository

    Salawu, Omotayo Akande

    2016-09-29

    Molybdenum oxide (MoO3) is an important material that is being considered for numerous technological applications, including catalysis and electrochromism. In the present study, we apply hybrid density functional theory to investigate O and Mo vacancies in the orthorhombic phase. We determine the vacancy formation energies of different defect sites as functions of the electron chemical potential, addressing different charge states. In addition, we investigate the consequences of defects for the material properties. Ultraviolet photoemission spectroscopy is employed to study the valence band of stoichiometric and O defective MoO3. We show that O vacancies result in occupied in-gap states.

  7. Vacancy formation in MoO3: hybrid density functional theory and photoemission experiments

    KAUST Repository

    Salawu, Omotayo Akande; Chroneos, Alexander; Vasilopoulou, Maria; Kennou, Stella; Schwingenschlö gl, Udo

    2016-01-01

    Molybdenum oxide (MoO3) is an important material that is being considered for numerous technological applications, including catalysis and electrochromism. In the present study, we apply hybrid density functional theory to investigate O and Mo vacancies in the orthorhombic phase. We determine the vacancy formation energies of different defect sites as functions of the electron chemical potential, addressing different charge states. In addition, we investigate the consequences of defects for the material properties. Ultraviolet photoemission spectroscopy is employed to study the valence band of stoichiometric and O defective MoO3. We show that O vacancies result in occupied in-gap states.

  8. Studies on radiation-induced graft polymerization

    International Nuclear Information System (INIS)

    Omichi, Hideki

    1978-09-01

    Radiation-induced graft polymerization is used extensively to improve physical properties of polymers, but few processes are now commercialized. The reason for this is partly inadequate basic research on the reaction and partly the difficulty in developing the grafting process with large radiation source. Firstly, new techniques are proposed of studying kinetics of the graft polymerization in heterogeneous system. Based on the grafting yield, the molecular weight of graft chains, and the amount of radicals given by ESR and activation analysis, kinetic parameters are obtained and the reaction mechanism of grafting process is discussed. Secondly, the development of grafting process of poly (vinyl chloride)-butadiene is described. By study of the reaction, process design, construction and operation of the pilot plant, and economic analysis of the process, this process with 60 Co gamma ray sources is shown to be industrially promising. (author)

  9. A radiopharmacological study without human radiation exposure

    International Nuclear Information System (INIS)

    Loew, D.; Graul, E.H.; Kunkel, R.

    1984-01-01

    The development, study and control of new drugs today is hardly conceivable without nuclear medicine studies. Nuclear physicians on ethical commissions bear great responsibility in the planning and execution of such studies. In order to protect subjects and patients those nuclear techniques are therefore to be welcome which do not include exposure to radiation. Nuclear techniques used in in-vitro diagnostics (RIA) and the determination of naturally occurring nuclides incorporated in the human body belong to this category. With the aid of a clinico-pharmacological study of a new combination of diuretics it is shown that both methods supply valuable pharmacodynamic evidence. (orig.) [de

  10. High-intensity xenon plasma discharge lamp for bulk-sensitive high-resolution photoemission spectroscopy.

    Science.gov (United States)

    Souma, S; Sato, T; Takahashi, T; Baltzer, P

    2007-12-01

    We have developed a highly brilliant xenon (Xe) discharge lamp operated by microwave-induced electron cyclotron resonance (ECR) for ultrahigh-resolution bulk-sensitive photoemission spectroscopy (PES). We observed at least eight strong radiation lines from neutral or singly ionized Xe atoms in the energy region of 8.4-10.7 eV. The photon flux of the strongest Xe I resonance line at 8.437 eV is comparable to that of the He Ialpha line (21.218 eV) from the He-ECR discharge lamp. Stable operation for more than 300 h is achieved by efficient air-cooling of a ceramic tube in the resonance cavity. The high bulk sensitivity and high-energy resolution of PES using the Xe lines are demonstrated for some typical materials.

  11. Electronic structure of superconducting Bi2212 crystal by angle resolved ultra violet photoemission

    International Nuclear Information System (INIS)

    Saini, N.L.; Shrivastava, P.; Garg, K.B.

    1993-01-01

    The electronic structure of a high quality superconducting Bi 2 Sr 2 CaCu 2 Osub(8+δ) (Bi2212) single crystal is studied by angle resolved ultra violet photoemission (ARUPS) using He I (21.2 eV). Our results appear to show two bands crossing the Fermi level in ΓX direction of the Brillouin zone as reported by Takahashi et al. The bands at higher binding energy do not show any appreciable dispersion. The nature of the states near the Fermi level is discussed and the observed band structure is compared with the band structure calculations. (author)

  12. Induced photoemission from driven nonadiabatic dynamics in an avoided crossing system

    Energy Technology Data Exchange (ETDEWEB)

    Arasaki, Yasuki; Mizuno, Yuta; Takatsuka, Kazuo, E-mail: kaztak@mns2.c.u-tokyo.ac.jp [Department of Basic Science, Graduate School of Arts and Sciences, The University of Tokyo, Komaba, 153-8902 Tokyo (Japan); Scheit, Simona [Department of Basic Science, Graduate School of Arts and Sciences, The University of Tokyo, Komaba, 153-8902 Tokyo (Japan); Theoretische Chemie, Universität Heidelberg, Im Neuneheimer Feld 229, 69120 Heidelberg (Germany)

    2014-12-21

    When vibrational dynamics on an ionic state (large dipole moment) is coupled to that on a neutral state (small dipole moment) such as at an avoided crossing in the alkali halide system, the population transfer between the states cause oscillation of the molecular dipole, leading to dipole emission. Such dynamics may be driven by an external field. We study how the coupled wavepacket dynamics is affected by the parameters (intensity, frequency) of the driving field with the aim of making use of the photoemission as an alternative detection scheme of femtosecond and subfemtosecond vibrational and electronic dynamics or as a characteristic optical source.

  13. Bogoliubov Angle, Particle-Hole Mixture and Angular Resolved Photoemission Spectroscopy in Superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Balatsky, A.

    2010-05-04

    Superconducting excitations - Bogoliubov quasiparticles - are the quantum mechanical mixture of negatively charged electron (-e) and positively charged hole (+e). We propose a new observable for Angular Resolved Photoemission Spectroscopy (ARPES) studies that is the manifestation of the particle-hole entanglement of the superconducting quasiparticles. We call this observable a Bogoliubov angle. This angle measures the relative weight of particle and hole amplitude in the superconducting (Bogoliubov) quasiparticle. We show how this quantity can be measured by comparing the ratio of spectral intensities at positive and negative energies.

  14. Study of radiation-destroyed wood

    International Nuclear Information System (INIS)

    Klimentov, A.S.; Shakhanova, R.K.; Stepanova, I.N.; Vysotskaya, I.F.

    1986-01-01

    The change in carbohydrate composition of aspen wood exposed to electron beam radiation (0.5 MeV, dose rates of 0-0.56 MGy) is studied. It has been found that the water-soluble polysaccharide content grows from 0.47 up to 8.54 %, and that of the non-hydrolyzed polysaccharides decreases from 49.4 down to 36.1 %. The polysaccharide total content of aspen wood goes down from 61.28 to 56.82 % with the radiation dose increasing. Consequently, the xylose, arabinose, and ramnose percentage of wood hydrolyzates increases correspondingly from 11.9 up to 15.44, from 0.66 up to 0.90, and from 0.21 up to 0.38

  15. A synchrotron radiation study of strontium titanate

    International Nuclear Information System (INIS)

    Maslen, E.N.; Spadaccini, N.; Ito, T.; Marumo, F.; Satow, Y.

    1995-01-01

    Electron deformation densities Δρ for SrTiO 3 have been determined from diffraction data measured using focused synchrotron radiation with λ = 0.7000 (2) A at the Photon Factory, KEK, Japan. Corrections for secondary extinction were estimated from the variation of diffraction intensity with path length, and checked from the λ-dependence of the strong intensities indicated by measurements using a weaker parallel beam with λ = 0.5000 (2) A. The 0.7 A study is more precise than earlier analyses with Mo Kα radiation. The difference density near the Ti nucleus is mildly anisotropic, and the Δρ topography is similar to those for closed-shell atoms in related perovskite structures. (orig.)

  16. Studies on chronic effect on radiation

    International Nuclear Information System (INIS)

    Yun, T.K.; Kang, T.U.; Yun, Y.S.; Chung, I.Y.; Koh, J. W.; Kim, J.W.; Ryu, Y.W.

    1983-01-01

    This experiment was carried out to evaluate the chronic harzard of Co-60 low dose irradiation on ICR mice. There is now considerable evidence from human studies that age, both at exposure to radiation and at observation for risk, can be a major determinant of radiation induced cancer risk. For this reason, ICR mice at different ages as specified below were exposed to 60 m rads/week, 500 m rads/biweek of whole body Co-60 radiation at a dose rate of 3.6 rads/min. ICR mice were irradiated during pregnant period and each period from the 1st week to the 3rd week to the 52nd week, from the 6th week to the 52nd week and from the 22nd week to the 52nd week after the birth. All the experimental mice were autopsied immediately after sacrificed at the 52nd week. And all of their major organs were examined grossly and weighed. After fixation histo-pathological preparations were made for microscopical study. Blood cells-W.B.C., R.B.C., Hb-from eye's vein were counted by hemocytometer and hemometer. (Author)

  17. Epidemiological studies of radiation workers: preliminary communication

    International Nuclear Information System (INIS)

    Schofield, G.B.

    1982-01-01

    British Nuclear Fuels Limited has embarked on a study of the mortality data among those of its workforce who were employed prior to 1 January 1976. The study covers a total population of about 41000 current and ex-employees, but is initially concerned with a radiation worker cohort of 7500 at the Sellafield establishment where the highest radiation doses are received. Tracing of the health status of ex-employees has been undertaken using the services provided by the Office of Population Censuses and Surveys (OPCS) and the Department of Health and Social Security (DHSS) and it is expected that ultimately the level of trace will be better than 97%. Mortality data not specifically related to radiation workers are included and relate to male deaths among serving staff and pensioners during the years 1962-1978. Those observed deaths (O) are compared on an age standardized basis with those expected (E) from the general population, the ratio O/E being about 1 for all cancers and less than 1 for non-cancer deaths. This pattern is consistent with the well known 'healthy worker' effect seen in industry. (author)

  18. Studying Radiation Tolerant ICs for LHC

    CERN Multimedia

    Faccio, F; Snoeys, W; Campbell, M; Casas-cubillos, J; Gomes, P

    2002-01-01

    %title\\\\ \\\\In the recent years, intensive work has been carried out on the development of custom ICs for the readout electronics for LHC experiments. As far as radiation hardness is concerned, attention has been focussed on high total dose applications, mainly for the tracker systems. The dose foreseen in this inner region is estimated to be higher than 1~Mrad/year. In the framework of R&D projects (RD-9 and RD-20) and in the ATLAS and CMS experiments, the study of different radiation hard processes has been pursued and good contacts with the manufacturers have been established. The results of these studies have been discussed during the Microelectronics User Group (MUG) rad-hard meetings, and now some HEP groups are working to develop radiation hard ICs for the LHC experiments on some of the available rad-hard processes.\\\\ \\\\In addition, a lot of the standard commercial electronic components and ASICs which are planned to be installed near the LHC machine and in the detectors will receive total doses in ...

  19. Light source for synchrotron radiation x-ray topography study at Beijing Synchrotron Radiation Laboratory (BSRL)

    International Nuclear Information System (INIS)

    Zhao Jiyong; Jiang Jianhua; Tian Yulian

    1992-01-01

    Characteristics of the synchrotron radiation source for X-ray topography study at Beijing Synchrotron Radiation Laboratory (BSRL) is described, local geometrical resolution of topographies is discussed, and the diffracting intensities of white beam topography is given

  20. Physiological and genetics studies of highly radiation-resistant bacteria

    International Nuclear Information System (INIS)

    Keller, L.C.

    1981-01-01

    The phenomenon of radiation resistance was studied using micrococci and Moraxella-Acinetobacter capable of surviving very high doses of gamma radiation which were isolated from foods. Physiological age, or growth phase, was found to be an important factor in making comparisons of radiation-resistance among different bacteria and their mutants. Radiation-resistant bacteria were highly resistant to the lethal effect of nitrosoguanidine used for mutagenesis. Studies of relative resistance of radiation-resistant bacteria, radiation-sensitive mutants, and nonradiation-resistant bacteria to killing by different chemical mutagens did not reveal a correlation between the traits of radiation resistance and mutagen resistance among different strains. Comparisons of plasmid profiles of radiation-resistant bacteria and selected radiation-sensitive mutants suggested the possibility that plasmids may carry genes involved in radiation resistance

  1. Study on radiation-responsive epigenomes

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Seung Sik; Lee, Seung Sik; Chung, Byung Yeoup; and others

    2013-01-15

    The purpose of this project is development of world-class head spring techniques of biological science for application of plant genomes/epigenomes through study on radiation-responsive epigenomes and improvement of the national competitiveness in the field of fundamental technology for biological science and industry. Research scope includes 1) Investigation of radiation-responsive epigenomes and elucidation of their relation with phenotypes, 2) Elucidation of interaction and transcription control of epigenomes and epigenetic regulators using IR, 3) Investigation of epigenome-mediated traits in plant development, differentiation and antioxidant defense using IR, and 4) Development of application techniques of radiation-responsive epigenomes for eco-monitoring and molecular breeding. Main results are as follow: investigation of the expression level of histone-modifying enzymes by IR; elucidation of the structural and functional changes of chaperone protein by IR; development of transgenic plant (DRD1-6); investigation of transcription control of epigenetic regulators by IR; investigation of relevance between DNA methylation and miRNA; comparison of gene expression in wild type and cmt mutant from Arabidopsis using gene chip; investigation control of epigenetic regulators in drd1-6 mutant by drought stress; development of transgenic plant using epigenetic regulators.

  2. Cell kinetic studies on radiation induced leukemogenesis

    International Nuclear Information System (INIS)

    Nakao, Isamu; Suzuki, Gen; Imai, Yasufumi; Kawase, Yoshiko; Nose, Masako; Hirashima, Kunitake; Bessho, Masami

    1989-01-01

    The purpose of this study was threefold: (1) to determine the clonal origin of radiation-induced thymic lymphoma in mice with cellular mosaicism for phosphoglycerate kinase; (2) to determine the incidence and latent period of myeloid leukemia and thymic lymphoma induced by whole-body exposure to median doses (3.0 Gy or less) in RFM/MsNrs-2 mice; and (3) to examine the influence of human recombinant interleukin-2 (hrIL-2). Thymic lymphoma was of a single cell origin. The incidence of radiation-induced myeloid leukemia and thymic lymphoma in RFM mice increased in a dose dependent fashion. Mean latent periods of both myeloid leukemia and thymic lymphoma after irradiation became shorter in proportion to radiation doses. When hrIL-2 was injected to RFM mice receiving 3.0 Gy, mean survivals were shorter in thymoma-bearing mice than the control mice. This suggested that hrIL-2 shortens the promotion step of thymoma. Administration of hrIL-2 failed to alter the incidence of myeloid leukemia or the mean survival of mice having myeloid leukemia, indicating that the protocol of hrIL-2 administration was not so sufficient as to alter the myeloid leukemogenesis. (Namekawa, K)

  3. Thermal and Field Enhanced Photoemission Comparison of Theory to Experiment

    CERN Document Server

    Lynn-Jensen, Kevin

    2004-01-01

    Photocathodes are a critical component of high-gain FEL’s and the analysis of their emission is complex. Relating their performance under laboratory conditions to conditions of an rf photoinjector is difficult. Useful models must account for cathode surface conditions and material properties, as well as drive laser parameters. We have developed a time-dependent model accounting for the effects of laser heating and thermal propagation on photoemission. It accounts for surface conditions (coating, field enhancement, reflectivity), laser parameters (duration, intensity, wavelength), and material characteristics (reflectivity, laser penetration depth, scattering rates) to predict current distribution and quantum efficiency. The applicatIon will focus on photoemission from metals and, in particular, dispenser photocathodes: the later introduces complications such as coverage non-uniformity and field enhancement. The performance of experimentally characterized photocathodes will be extrapolated to 0.1 - 1 nC bunch...

  4. Core-level photoemission revealing the Mott transition

    International Nuclear Information System (INIS)

    Kim, Hyeong-Do; Noh, Han-Jin; Kim, K.H.; Oh, S.-J.

    2005-01-01

    Ru 3d core-level X-ray photoemission spectra of various ruthenates are examined. They show in general two-peak structures, which can be assigned as the screened and unscreened peaks. The screened peak is absent in a Mott insulator, but develops into a main peak as the correlation strength becomes weak. This spectral behavior is well explained by the dynamical mean-field theory calculation for the single-band Hubbard model with the on-site core-hole potential using the exact diagonalization method. The new mechanism of the core-level photoemission satellite can be utilized to reveal the Mott transition phenomenon in various strongly correlated electron systems

  5. Viscometric studies of chitosan radiation degradation

    International Nuclear Information System (INIS)

    Rapado, M.; Ceausoglu, I.; Hunkeler, D.

    2001-01-01

    The paper presents the preliminary results, related to the viscometric studies on chitosan gamma radiation degradation. To follow the effects on the processes of chitosan transformations caused by irradiation in vacuum irradiated solutions changes of viscosity, and viscosity average molecular weight were measured The influence of absorbed dose on the chitosan molecular weight was studied using the Mark-Houwink-Sakurada equation. Various relationships for the for the determination of the intrinsic viscosity were made vias the Huggins, Kramer and Schulz- Blaschke models. The distinct decrease of intrinsic viscosity indicates that the main change scission was the dominating process

  6. Photoemission and the origin of high temperature superconductivity

    International Nuclear Information System (INIS)

    Norman, M. R.; Randeria, M.; Janko, B.; Campuzano, J. C.

    2000-01-01

    The condensation energy can be shown to be a moment of the change in the occupied part of the spectral function when going from the normal to the superconducting state. As a consequence, there is a one to one correspondence between the energy gain associated with forming the superconducting ground state, and the dramatic changes seen in angle resolved photoemission spectra. Some implications this observation has are offered

  7. Radiation dose measurement in gastrointestinal studies

    International Nuclear Information System (INIS)

    Sulieman, A.; Elzaki, M.; Kappas, C.; Theodorou, K.

    2011-01-01

    Barium studies investigations (barium swallow, barium meal and barium enema) are the basic routine radiological examination, where barium sulphate suspension is introduced to enhance image contrast of gastrointestinal tracts. The aim of this study was to quantify the patients' radiation doses during barium studies and to estimate the organ equivalent dose and effective dose with those procedures. A total of 33 investigations of barium studies were measured by using thermoluminescence dosemeters. The result showed that the patient entrance surface doses were 12.6±10, 44.5±49 and 35.7±50 mGy for barium swallow, barium meal, follow through and enema, respectively. Effective doses were 0.2, 0.35 and 1.4 mSv per procedure for barium swallow, meal and enema respectively. Radiation doses were comparable with the previous studies. A written protocol for each procedure will reduce the inter-operator variations and will help to reduce unnecessary exposure. (authors)

  8. Methodologic assessment of radiation epidemiology studies

    International Nuclear Information System (INIS)

    Beebe, G.W.

    1983-01-01

    Epidemiologic studies of the late effects of ionizing radiation have utilized the entire spectrum of situations in which man has been exposed. These studies have provided insights into the dependence of human effects upon not only dose to target tissues but also other dimensions of exposure, host characteristics, and time following exposure. Over the past three decades studies have progressed from the mere identification of effects to their measurement. Because investigators of human effects have no control over the exposure situation, validity must be sought in the consistency of findings among independent studies and with accepted biologic principles. Because exposure may be confounded with factors that are hidden from view, bias may enter into any study of human exposure. Avoidance of bias and attainment of sufficient power to detect relationships that are real are methodologic challenges. Many methodologic issues, e.g., those associated with the definition and measurement of specific end-points, or with the selection of appropriate controls, permeate epidemiologic work in all fields. Others, especially those concerned with the measurement of exposure, the patterning of events in time after exposure, and the prediction of events beyond the scope of existing observations give radiation epidemiology its distinctive character

  9. Tetragonal and collapsed-tetragonal phases of CaFe2As2 : A view from angle-resolved photoemission and dynamical mean-field theory

    Science.gov (United States)

    van Roekeghem, Ambroise; Richard, Pierre; Shi, Xun; Wu, Shangfei; Zeng, Lingkun; Saparov, Bayrammurad; Ohtsubo, Yoshiyuki; Qian, Tian; Sefat, Athena S.; Biermann, Silke; Ding, Hong

    2016-06-01

    We present a study of the tetragonal to collapsed-tetragonal transition of CaFe2As2 using angle-resolved photoemission spectroscopy and dynamical mean field theory-based electronic structure calculations. We observe that the collapsed-tetragonal phase exhibits reduced correlations and a higher coherence temperature due to the stronger Fe-As hybridization. Furthermore, a comparison of measured photoemission spectra and theoretical spectral functions shows that momentum-dependent corrections to the density functional band structure are essential for the description of low-energy quasiparticle dispersions. We introduce those using the recently proposed combined "screened exchange + dynamical mean field theory" scheme.

  10. Evidence of the nature of core-level photoemission satellites using angle-resolved photoemission extended fine structure

    Energy Technology Data Exchange (ETDEWEB)

    Moler, E.J.; Kellar, S.A.; Huff, W.R.A. [Lawrence Berkeley National Lab., CA (United States)] [and others

    1997-04-01

    The authors present a unique method of experimentally determining the angular momentum and intrinsic/extrinsic origin of core-level photoemission satellites by examining the satellite diffraction pattern in the Angle Resolved Photoemission Extended Fine Structure (ARPEFS) mode. They show for the first time that satellite peaks not associated with chemically differentiated atomic species display an ARPEFS intensity oscillation. They present ARPEFS data for the carbon 1s from ({radical}3x{radical}3)R30 CO/Cu(111) and p2mg(2xl)CO/Ni(110), nitrogen 1s from c(2x2) N{sub 2}/Ni(100), cobalt 1s from p(1x1)Co/Cu(100), and nickel 3p from clean nickel (111). The satellite peaks and tails of the Doniach-Sunjic line shapes in all cases exhibit ARPEFS curves which indicate an angular momentum identical to the main peak and are of an intrinsic nature.

  11. Evidence of the nature of core-level photoemission satellites using angle-resolved photoemission extended fine structure

    International Nuclear Information System (INIS)

    Moler, E.J.; Kellar, S.A.; Huff, W.R.A.

    1997-01-01

    The authors present a unique method of experimentally determining the angular momentum and intrinsic/extrinsic origin of core-level photoemission satellites by examining the satellite diffraction pattern in the Angle Resolved Photoemission Extended Fine Structure (ARPEFS) mode. They show for the first time that satellite peaks not associated with chemically differentiated atomic species display an ARPEFS intensity oscillation. They present ARPEFS data for the carbon 1s from (√3x√3)R30 CO/Cu(111) and p2mg(2xl)CO/Ni(110), nitrogen 1s from c(2x2) N 2 /Ni(100), cobalt 1s from p(1x1)Co/Cu(100), and nickel 3p from clean nickel (111). The satellite peaks and tails of the Doniach-Sunjic line shapes in all cases exhibit ARPEFS curves which indicate an angular momentum identical to the main peak and are of an intrinsic nature

  12. Study of the radiative pion decay

    International Nuclear Information System (INIS)

    Chen, Chuan-Hung; Geng, Chao-Qiang; Lih, Chong-Chung

    2011-01-01

    We study the radiative pion decay of π + →e + ν e γ in the light-front quark model. We also summarize the result in the chiral perturbation theory. The vector and axial-vector hadronic form factors (F V,A ) for the π→γ transition are evaluated in the whole allowed momentum transfer. In terms of these momentum dependent form factors, we calculate the decay branching ratio and compare our results with the experimental data and other theoretical predictions in the literature. We also constrain the possible size of the tensor interaction in the light-front quark model.

  13. The BNFL radiation-mortality study

    International Nuclear Information System (INIS)

    Clough, E.A.; Schofield, G.B.

    1982-01-01

    An overview of an epidemiological study of BNFL employees and pensioners is presented. Overall, mortality patterns are similar to those in the general population. Non-cancer deaths among serving staff are significantly below those expected from national statistics due to the healthy worker effect; pensioners are more comparable to the national population. A similar pattern is found for lung malignancy. Observed deaths due to other cancers among serving staff and pensioners approximate closely to expectation; most are due to leukaemia but there is no evidence of any increased incidence at Sellafield where radiation exposures are higher than at other BNFL sites. (U.K.)

  14. Neutron radiation damage studies on silicon detectors

    International Nuclear Information System (INIS)

    Li, Zheng; Chen, W.; Kraner, H.W.

    1990-10-01

    Effects of neutron radiation on electrical properties of Si detectors have been studied. At high neutron fluence (Φ n ≥ 10 12 n/cm 2 ), C-V characteristics of detectors with high resistivities (ρ ≥ 1 kΩ-cm) become frequency dependent. A two-trap level model describing this frequency dependent effect is proposed. Room temperature anneal of neutron damaged (at LN 2 temperature) detectors shows three anneal stages, while only two anneal stages were observed in elevated temperature anneal. 19 refs., 14 figs

  15. Study of radiation detectors response in standard X, gamma and beta radiation standard beams

    International Nuclear Information System (INIS)

    Nonato, Fernanda Beatrice Conceicao

    2010-01-01

    The response of 76 Geiger-Mueller detectors, 4 semiconductor detectors and 34 ionization chambers were studied. Many of them were calibrated with gamma radiation beams ( 37 Cs and 60 Co), and some of them were tested in beta radiation ( 90 Sr+ 9' 0Y e 204 Tl) and X radiation (N-60, N-80, N-100, N-150) beams. For all three types of radiation, the calibration factors of the instruments were obtained, and the energy and angular dependences were studied. For beta and gamma radiation, the angular dependence was studied for incident radiation angles of 0 deg and +- 45 deg. The curves of the response of the instruments were obtained over an angle interval of 0 deg to +- 90 deg, for gamma, beta and X radiations. The calibration factors obtained for beta radiation were compared to those obtained for gamma radiation. For gamma radiation, 24 of the 66 tested Geiger-Mueller detectors presented results for the energy dependence according to international recommendation of ISO 4037-2 and 56 were in accordance with the Brazilian ABNT 10011 recommendation. The ionization chambers and semiconductors were in accordance to national and international recommendations. All instruments showed angular dependence less than 40%. For beta radiation, the instruments showed unsatisfactory results for the energy dependence and angular dependence. For X radiation, the ionization chambers presented results for energy dependence according to the national recommendation, and the angular dependence was less than 40%. (author)

  16. Development of soft x-ray time-resolved photoemission spectroscopy system with a two-dimensional angle-resolved time-of-flight analyzer at SPring-8 BL07LSU

    Energy Technology Data Exchange (ETDEWEB)

    Ogawa, Manami; Yamamoto, Susumu; Nakamura, Fumitaka; Yukawa, Ryu; Fukushima, Akiko; Harasawa, Ayumi; Kakizaki, Akito; Matsuda, Iwao [Institute for Solid State Physics, University of Tokyo, 5-1-5 Kashiwanoha, Chiba 277-8581 (Japan); Kousa, Yuka; Kondoh, Hiroshi [Department of Chemistry, Keio University, Yokohama 223-8522 (Japan); Tanaka, Yoshihito [RIKEN/SPring-8 Center, 1-1-1, Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148 (Japan)

    2012-02-15

    We have developed a soft x-ray time-resolved photoemission spectroscopy system using synchrotron radiation (SR) at SPring-8 BL07LSU and an ultrashort pulse laser system. Two-dimensional angle-resolved measurements were performed with a time-of-flight-type analyzer. The photoemission spectroscopy system is synchronized to light pulses of SR and laser using a time control unit. The performance of the instrument is demonstrated by mapping the band structure of a Si(111) crystal over the surface Brillouin zones and observing relaxation of the surface photo-voltage effect using the pump (laser) and probe (SR) method.

  17. High-sensitivity ultraviolet photoemission spectroscopy technique for direct detection of gap states in organic thin films

    Energy Technology Data Exchange (ETDEWEB)

    Bussolotti, Fabio, E-mail: fabio@ims.ac.jp

    2015-10-01

    Highlights: • Density of gap states in organic thin film was detected by photoemission spectroscopy. • Inert gas exposure affects the density of gap states in organic thin films. • Density of gap states controls the energy level alignment at the organic/inorganic and organic/organic interfaces. - Abstract: We developed ultrahigh sensitivity, low-background ultraviolet photoemission spectroscopy (UPS) technique which does not introduce detectable radiation damages into organic materials. The UPS allows to detect density of states of the order of ∼10{sup 16} states eV{sup −1} cm{sup −3} even for radiation-sensitive organic films, this results being comparable to electrical measurements of charge trapping centers. In this review we introduce the method of ultrahigh sensitivity photoemission measurement and we present some results on the energy distribution of gap states in pentacene (Pn) films deposited on SiO{sub 2} and Au(1 1 1) substrate. For Pn/SiO{sub 2} thin film the results show that exposure to inert gas (N{sub 2} and Ar) atmosphere produces a sharp rise in gap states from 10{sup 16} to 10{sup 18} states eV{sup −1} cm{sup −3} and pushes the Fermi level closer to the valence band (0.15–0.17 eV), as does exposure to O{sub 2} (0.20 eV), while no such gas-induced effects are observed for Pn/Au(1 1 1) system. The results demonstrate that these gap states originate from small imperfections in the Pn packing structure, which are induced by gas penetration into the film through the Pn crystal grain boundaries. Similar results were obtained for CuPc/F{sub 16}CuPc thin films, a prototypical example of donor/acceptor interface for photovoltaic application.

  18. Soft X-ray angle-resolved photoemission spectroscopy of heavily boron-doped superconducting diamond films

    Directory of Open Access Journals (Sweden)

    T. Yokoya, T. Nakamura, T. Matushita, T. Muro, H. Okazaki, M. Arita, K. Shimada, H. Namatame, M. Taniguchi, Y. Takano, M. Nagao, T. Takenouchi, H. Kawarada and T. Oguchi

    2006-01-01

    Full Text Available We have performed soft X-ray angle-resolved photoemission spectroscopy (SXARPES of microwave plasma-assisted chemical vapor deposition diamond films with different B concentrations in order to study the origin of the metallic behavior of superconducting diamond. SXARPES results clearly show valence band dispersions with a bandwidth of ~23 eV and with a top of the valence band at gamma point in the Brillouin zone, which are consistent with the calculated valence band dispersions of pure diamond. Boron concentration-dependent band dispersions near the Fermi level (EF exhibit a systematic shift of EF, indicating depopulation of electrons due to hole doping. These SXARPES results indicate that diamond bands retain for heavy boron doping and holes in the diamond band are responsible for the metallic states leading to superconductivity at low temperature. A high-resolution photoemission spectroscopy spectrum near EF of a heavily boron-doped diamond superconductor is also presented.

  19. Method to map one-dimensional electronic wave function by using multiple Brillouin zone angle resolved photoemission

    Directory of Open Access Journals (Sweden)

    Dong-Wook Lee

    2010-10-01

    Full Text Available Angle resolved photoemission spectroscopy (ARPES is a powerful tool to investigate electronic structures in solids and has been widely used in studying various materials. The electronic structure information by ARPES is obtained in the momentum space. However, in the case of one-dimensional system, we here show that we extract the real space information from ARPES data taken over multiple Brillouin zones (BZs. Intensities in the multiple BZs are proportional to the photoemission matrix element which contains information on the coefficient of the Bloch wave function. It is shown that the Bloch wave function coefficients can be extracted from ARPES data, which allows us to construct the real space wave function. As a test, we use ARPES data from proto-typical one-dimensional system SrCuO2 and construct the real space wave function.

  20. Study on Earth Radiation Budget mission scenarios

    Energy Technology Data Exchange (ETDEWEB)

    Dlhopolsky, R; Hollmann, R; Mueller, J; Stuhlmann, R [GKSS-Forschungszentrum Geesthacht GmbH (Germany). Inst. fuer Atmosphaerenphysik

    1998-12-31

    The goal of this study is to study optimized satellite configurations for observation of the radiation balance of the earth. We present a literature survey of earth radiation budget missions and instruments. We develop a parametric tool to simulate realistic multiple satellite mission scenarios. This tool is a modular computer program which models satellite orbits and scanning operation. We use Meteosat data sampled at three hour intervals as a database to simulate atmospheric scenes. Input variables are satellite equatorial crossing time and instrument characteristics. Regional, zonal and global monthly averages of shortwave and longwave fluxes for an ideal observing system and several realistic satellite scenarios are produced. Comparisons show that the three satellite combinations which have equatorial crossing times at midmorning, noon and midafternoon provide the best shortwave monitoring. Crossing times near sunrise and sunset should be avoided for the shortwave. Longwave diurnal models are necessary over and surfaces and cloudy regions, if there are only two measurements made during daylight hours. We have found in the shortwave inversion comparison that at least 15% of the monthly regional errors can be attributed to the shortwave anisotropic models used. (orig.) 68 refs.

  1. Study on Earth Radiation Budget mission scenarios

    Energy Technology Data Exchange (ETDEWEB)

    Dlhopolsky, R.; Hollmann, R.; Mueller, J.; Stuhlmann, R. [GKSS-Forschungszentrum Geesthacht GmbH (Germany). Inst. fuer Atmosphaerenphysik

    1997-12-31

    The goal of this study is to study optimized satellite configurations for observation of the radiation balance of the earth. We present a literature survey of earth radiation budget missions and instruments. We develop a parametric tool to simulate realistic multiple satellite mission scenarios. This tool is a modular computer program which models satellite orbits and scanning operation. We use Meteosat data sampled at three hour intervals as a database to simulate atmospheric scenes. Input variables are satellite equatorial crossing time and instrument characteristics. Regional, zonal and global monthly averages of shortwave and longwave fluxes for an ideal observing system and several realistic satellite scenarios are produced. Comparisons show that the three satellite combinations which have equatorial crossing times at midmorning, noon and midafternoon provide the best shortwave monitoring. Crossing times near sunrise and sunset should be avoided for the shortwave. Longwave diurnal models are necessary over and surfaces and cloudy regions, if there are only two measurements made during daylight hours. We have found in the shortwave inversion comparison that at least 15% of the monthly regional errors can be attributed to the shortwave anisotropic models used. (orig.) 68 refs.

  2. Study of catalytic phenomena in radiation chemistry

    International Nuclear Information System (INIS)

    Dran, J.C.

    1965-01-01

    Two phenomena have been studied: the action of γ rays from radio-cobalt on the adsorption and catalytic properties of ZnO and NiO in. relationship with the heterogeneous oxidation of CO, and the homogeneous catalysis by OsO 4 of the oxidation of various aqueous phase solutes by the same radiation. The prior irradiation of ZnO and of NiO does not modify their catalytic activity but generally increases the adsorption energy of -the gases CO and O 2 . The influence of the radiations appears to be connected with the presence of traces of water on ZnO and of an excess of oxygen on NiO. Osmium tetroxide which is not degraded by irradiation in acid solution, accelerates the radiolytic oxidation of certain compounds (Te IV , Pt 11 , As 111 ) in the presence of oxygen, as a result of its sensitizing effect on the oxidation by H 2 O 2 . In the case of phosphites on the other hand, OsO 4 has a protecting action under certain conditions of acidity and may suppress entirely the chain reaction which characterizes the oxidation of this solute byγ rays. A general mechanism is proposed for these phenomena. The rate constant for the OsO 4 + HO 2 reaction is calculated to be 5.7 x 10 5 l.mol -1 . sec -1 . (author) [fr

  3. Studies on radiation injury of the kidney

    International Nuclear Information System (INIS)

    Kamiya, Akio

    1982-01-01

    According to many experimental reports on the radiation renal injuries, the influences of irradiation were observed not only in the irradiated kidney, but also in the contralateral kidney. However, its mechanism has not yet been demonstrated clearly. In order to clarify the mechanism of development of pathophysiological changes seen on the kidney of non-irradiated side, a study was made of function and pathological condition of a remaining kidney after the enucleation of ir radiated side kidney after irradiation. Twenty-eitht rabbits were divided into 4 groups. A: 14 rabbits were irradiated on their left kidney with 60 Co- gamma ray 50 Gy doses. B: 6 rabbits were nephrectomized of their left kidney on the first day after 50 Gy irradiation. C: 4 rabbits were nephrectomized of their left kidney on the eighth day after 50 Gy irradiation. D: 4 rabbits were simple nephrectomized. The results suggest that changes on the irradiated side of kidney bring about effect to the contra-lateral kidney at an early stage after the irradiation. (J.P.N.)

  4. Epidemiological studies of radiation risks (NRPB Association)

    International Nuclear Information System (INIS)

    Muirhead, C.R.; Kellerer, A.M.; Chmelevsky, D.

    1993-01-01

    Objectives of project are: to analyse data on populations exposed to high doses of radiation, such as the Japanese atomic bomb survivors and groups of uranium miners; to examine data on populations exposed at low doses and methods for analysing such data; to perform preparatory work for the compilation of 'probability of causation' tables that are specific to EC countries and that also cover radon daughter exposures; to study the incidence and mortality from thyroid cancer in a cohort with medical exposures to 131 I; to study cancer incidence and mortality among Swedish patients given radiotherapy for skin haemangioma in childhood; and to examine the incidence of second tumours among Italian patients given radiotherapy for cancer of the head, neck, breast, endometrium, uterine cervix or thyroid. Results of the six contributions for the reporting period are presented. (R.P.) 4 refs

  5. Characterizing the effects of regolith surface roughness on photoemission from surfaces in space

    Science.gov (United States)

    Dove, A.; Horanyi, M.; Wang, X.

    2017-12-01

    Surfaces of airless bodies and spacecraft in space are exposed to a variety of charging environments. A balance of currents due to plasma bombardment, photoemission, electron and ion emission and collection, and secondary electron emission determines the surface's charge. Photoelectron emission is the dominant charging process on sunlit surfaces in the inner solar system due to the intense solar UV radiation. This can result in a net positive surface potential, with a cloud of photoelectrons immediately above the surface, called the photoelectron sheath. Conversely, the unlit side of the body will charge negatively due the collection of the fast-moving solar wind electrons. The interaction of charged dust grains with these positively and negatively charged surfaces, and within the photoelectron and plasma sheaths may explain the occurrence of dust lofting, levitation and transport above the lunar surface. The surface potential of exposed objects is also dependent on the material properties of their surfaces. Composition and particle size primarily affect the quantum efficiency of photoelectron generation; however, surface roughness can also control the charging process. In order to characterize these effects, we have conducted laboratory experiments to examine the role of surface roughness in generating photoelectrons in dedicated laboratory experiments using solid and dusty surfaces of the same composition (CeO2), and initial comparisons with JSC-1 lunar simulant. Using Langmuir probe measurements, we explore the measured potentials above insulating surfaces exposed to UV and an electric field, and we show that the photoemission current from a dusty surface is largely reduced due to its higher surface roughness, which causes a significant fraction of the emitted photoelectrons to be re-absorbed within the surface. We will discuss these results in context of similar situations on planetary surfaces.

  6. Visualizing electron dynamics in organic materials: Charge transport through molecules and angular resolved photoemission

    Science.gov (United States)

    Kümmel, Stephan

    Being able to visualize the dynamics of electrons in organic materials is a fascinating perspective. Simulations based on time-dependent density functional theory allow to realize this hope, as they visualize the flow of charge through molecular structures in real-space and real-time. We here present results on two fundamental processes: Photoemission from organic semiconductor molecules and charge transport through molecular structures. In the first part we demonstrate that angular resolved photoemission intensities - from both theory and experiment - can often be interpreted as a visualization of molecular orbitals. However, counter-intuitive quantum-mechanical electron dynamics such as emission perpendicular to the direction of the electrical field can substantially alter the picture, adding surprising features to the molecular orbital interpretation. In a second study we calculate the flow of charge through conjugated molecules. The calculations show in real time how breaks in the conjugation can lead to a local buildup of charge and the formation of local electrical dipoles. These can interact with neighboring molecular chains. As a consequence, collections of ''molecular electrical wires'' can show distinctly different characteristics than ''classical electrical wires''. German Science Foundation GRK 1640.

  7. Rotatable spin-polarized electron source for inverse-photoemission experiments

    International Nuclear Information System (INIS)

    Stolwijk, S. D.; Wortelen, H.; Schmidt, A. B.; Donath, M.

    2014-01-01

    We present a ROtatable Spin-polarized Electron source (ROSE) for the use in spin- and angle-resolved inverse-photoemission (SR-IPE) experiments. A key feature of the ROSE is a variable direction of the transversal electron beam polarization. As a result, the inverse-photoemission experiment becomes sensitive to two orthogonal in-plane polarization directions, and, for nonnormal electron incidence, to the out-of-plane polarization component. We characterize the ROSE and test its performance on the basis of SR-IPE experiments. Measurements on magnetized Ni films on W(110) serve as a reference to demonstrate the variable spin sensitivity. Moreover, investigations of the unoccupied spin-dependent surface electronic structure of Tl/Si(111) highlight the capability to analyze complex phenomena like spin rotations in momentum space. Essentially, the ROSE opens the way to further studies on complex spin-dependent effects in the field of surface magnetism and spin-orbit interaction at surfaces

  8. Space-charge effects in high-energy photoemission

    Energy Technology Data Exchange (ETDEWEB)

    Verna, Adriano, E-mail: adriano.verna@uniroma3.it [Dipartimento di Scienze, Università degli Studi Roma Tre, Via della Vasca Navale 84, I-00146 Roma (Italy); CNISM Unità di Roma Tre, Via della Vasca Navale 84, I-00146 Roma (Italy); Greco, Giorgia [Dipartimento di Scienze, Università degli Studi Roma Tre, Via della Vasca Navale 84, I-00146 Roma (Italy); Lollobrigida, Valerio [Dipartimento di Scienze, Università degli Studi Roma Tre, Via della Vasca Navale 84, I-00146 Roma (Italy); Scuola Dottorale in Matematica e Fisica, Università Roma Tre, Via della Vasca Navale 84, I-00146 Roma (Italy); Offi, Francesco; Stefani, Giovanni [Dipartimento di Scienze, Università degli Studi Roma Tre, Via della Vasca Navale 84, I-00146 Roma (Italy); CNISM Unità di Roma Tre, Via della Vasca Navale 84, I-00146 Roma (Italy)

    2016-05-15

    Highlights: • N-body simulations of interacting photoelectrons in hard X-ray experiments. • Secondary electrons have a pivotal role in determining the energy broadening. • Space charge has negligible effects on the photoelectron momentum distribution. • A simple model provides the characteristic time for energy-broadening mechanism. • The feasibility of time-resolved high-energy experiments with FELs is discussed. - Abstract: Pump-and-probe photoelectron spectroscopy (PES) with femtosecond pulsed sources opens new perspectives in the investigation of the ultrafast dynamics of physical and chemical processes at the surfaces and interfaces of solids. Nevertheless, for very intense photon pulses a large number of photoelectrons are simultaneously emitted and their mutual Coulomb repulsion is sufficiently strong to significantly modify their trajectory and kinetic energy. This phenomenon, referred as space-charge effect, determines a broadening and shift in energy for the typical PES structures and a dramatic loss of energy resolution. In this article we examine the effects of space charge in PES with a particular focus on time-resolved hard X-ray (∼10 keV) experiments. The trajectory of the electrons photoemitted from pure Cu in a hard X-ray PES experiment has been reproduced through N-body simulations and the broadening of the photoemission core-level peaks has been monitored as a function of various parameters (photons per pulse, linear dimension of the photon spot, photon energy). The energy broadening results directly proportional to the number N of electrons emitted per pulse (mainly represented by secondary electrons) and inversely proportional to the linear dimension a of the photon spot on the sample surface, in agreement with the literature data about ultraviolet and soft X-ray experiments. The evolution in time of the energy broadening during the flight of the photoelectrons is also studied. Despite its detrimental consequences on the energy

  9. Radiation chemical studies on the treatment of waste water

    International Nuclear Information System (INIS)

    Sakumoto, Akihisa; Miyata, Teijiro; Arai, Michimasa; Arai, Hidehiko

    1982-10-01

    The radiation induced reaction in aqueous solution was studied to develope the radiation treatment as a new technique for waste water and to elevate the effectiveness of radiation. The effectiveness of radiation was enhanced by combination of radiation induced reaction with conventional methods such as biological treatment and coagulation treatment. The synergistic effect of radiation and ozone was studied by using phenol and ethylene glycol. The chain reaction was observed in the radiation induced oxidation. The combination of radiation and ozone is considered to be one of the most useful method. In this report, the mechanism of each reaction and the applicability of the reaction to the treatment of waste water are discussed. (author)

  10. Final state selection in the 4p photoemission of Rb by combining laser spectroscopy with soft-x-ray photoionization

    International Nuclear Information System (INIS)

    Schulz, J.; Tchaplyguine, M.; Rander, T.; Bergersen, H.; Lindblad, A.; Oehrwall, G.; Svensson, S.; Heinaesmaeki, S.; Sankari, R.; Osmekhin, S.; Aksela, S.; Aksela, H.

    2005-01-01

    Fine structure resolved 4p photoemission studies have been performed on free rubidium atoms in the ground state and after excitation into the [Kr]5p 2 P 1/2 and 2 P 3/2 states. The 4p 5 5p final states have been excited in the 4p 6 5s→4p 5 5p conjugate shakeup process from ground state atoms as well as by direct photoemission from laser excited atoms. The relative intensities differ considerably in these three excitation schemes. The differences in the laser excited spectra could be described well using calculations based on the pure jK-coupling scheme. Thereby it was possible to specify the character of the various final states. Furthermore it has been possible to resolve two of the final states whose energy separation is smaller than the experimental resolution by selectively exciting them in a two step scheme, where the laser selects the spin-orbit coupling in the intermediate state and determines the final state coupling after x-ray photoemission

  11. Electronic properties of Nd2−xCexCuO4+δ: A hard X-ray photoemission investigation

    International Nuclear Information System (INIS)

    Guarino, A.; Panaccione, G.; Offi, F.; Monaco, G.; Fondacaro, A.; Torelli, P.; Fittipaldi, R.; Vecchione, A.; Pace, S.; Nigro, A.

    2016-01-01

    Highlights: • We grow and characterize Nd 2−x Ce x CuO 4+δ samples as thin film and single crystal. • We study the Cu 2p levels of our samples by hard X-ray photoemission spectroscopy. • We investigate bulk features of the Nd 2−x Ce x CuO 4+δ samples. • Signature of the bulk response is correlated with the crystallinity of the samples. - Abstract: Cu 2p core levels spectra measured by X-ray photoemission spectroscopy of selected as-grown Nd 2−x Ce x CuO 4+δ samples are presented and discussed. The presence of a satellite peak in the 2p core level of Nd 2−x Ce x CuO 4+δ single crystal by hard X-ray photoemission is confirmed in all non-superconducting samples, films and single crystals investigated in this work. The comparison of the spectral features of the different samples suggests that the presence and the intensity of this satellite peak is not related to the electric transport properties, but to the texture characteristics.

  12. Background radiation study of Offa industrial area of Kwara State ...

    African Journals Online (AJOL)

    A study of the external background radiation in Offa industrial area of Kwara State is hereby reported. An in-situ measurement using two Digilert radiation monitors at five different stations were carried out. A mean exposure rate of 0.0132mR/hr, which represents 20% elevation from the standard background radiation, was ...

  13. Various aspects of lyoluminescence studies in radiation research

    International Nuclear Information System (INIS)

    Kundu, H.K.

    1992-01-01

    Lyoluminescence is the emission of light during the dissolution of irradiated organic and inorganic solids in suitable solvents. This phenomenon has attracted interdisciplinary research involving radiation physics, radiation chemistry and physical chemistry. This paper presents an overall view of the various aspects of lyoluminescence studies in the field of radiation research. (author). 14 refs

  14. Studies of radiation and chemical toxicity. Progress report

    International Nuclear Information System (INIS)

    1986-01-01

    Annual report for the Studies of Radiation and Chemical Toxicity Program at the University of Rochester is presented. Progress is reported on four projects: Neurobehavorial Toxicity of Organometallic Fuel Additives, Mechanisms of Permanent and Delayed Pathologic Effects of Ionizing Radiation, Solid State Radiation Chemistry of the DNA Backbone, and Pulmonary Biochemistry

  15. Radiation Chemistry Studies on Chemotherapeutic Agents

    DEFF Research Database (Denmark)

    Gohn, M.; Getoff, N.; Bjergbakke, Erling

    1977-01-01

    Adrenalin has been studied as a model radiation protective agent by means of pulse radiolysis in aqueous solutions. The rate constants for the reactions of adrenalin with e–aq and OH were determined : k(e–aq+ adr—NH+2)= 7.5 × 108 dm3 mol–1 s–1, k(e–aq+ adr—NH)= 2.5 × 108 dm3 mol–1 s–1, and k......(OH + adr)= 2.2 × 1010 dm3 mol–1 s–1(pH = 9.2). e–aq attacks the amino group by splitting off methylamine, whereas OH and O–aq lead to the formation of the corresponding adducts of the cyclohexadienyl type. OH radicals can also abstract an electron from an O– group at pH > 8....

  16. Radiation chemistry studies on chemotherapeutic agents

    International Nuclear Information System (INIS)

    Gohn, M.; Getoff, N.; Bjergbakke, E.

    1977-01-01

    Adrenalin has been studied as a model radiation protective agent by means of pulse radiolysis in aqueous solutions. The rate constants for the reactions of adrenalin with e - sub(aq) and OH were determined: k(e - sub(aq) + adr -NH + 2 ) = 7.5 x 10 8 dm 3 mol -1 s -1 , k(e - sub(aq) + adr - NH) = 2.5 x 10 8 dm 3 mol -1 s -1 , and k(OH + adr) = 2.2 x 10 -10 dm 3 mol -1 s -1 (pH = 9.2). e - sub(aq) attacks the amino group by splitting off methylamine, whereas OH and O - sub(aq) lead to the formation of the corresponding adducts of the cyclohexadienyl type. OH radicals can also abstract an electron from an 0 - group at pH > 8. (author)

  17. Postgraduate studies in radiation biology in Europe

    International Nuclear Information System (INIS)

    Trott, K.R.; Lohmann, P.H.M.; Zeeland, A.A. van; Natarajan, A.T.; Schibilla, H.; Chadwick, K.; Kellerer, A.M.; Steinhaeusler, F.

    1998-01-01

    The present system of radiobiological research in universities and research centres is no longer able to train radiobiologists who have a comprehensive understanding of the entire field of radiation biology including both 'classical' and molecular radiation biology. However, such experts are needed in view of the role radiation protection plays in our societies. No single institution in Europe could now run a 1-year, full-time course which covers all aspects of the radiobiological basis of radiation protection. Therefore, a cooperative action of several universities from different EU member states has been developed and is described herein. (orig.)

  18. Ionizing radiation effects on floating gates

    International Nuclear Information System (INIS)

    Cellere, G.; Paccagnella, A.; Visconti, A.; Bonanomi, M.

    2004-01-01

    Floating gate (FG) memories, and in particular Flash, are the dominant among modern nonvolatile memory technologies. Their performance under ionizing radiation was traditionally studied for the use in space, but has become of general interest in recent years. We are showing results on the charge loss from programmed FG arrays after 10 keV x-rays exposure. Exposure to ionizing radiation results in progressive discharge of the FG. More advanced devices, featuring smaller FG, are less sensitive to ionizing radiation that older ones. The reason is identified in the photoemission of electrons from FG, since at high doses it dominates over charge loss deriving from electron/hole pairs generation in the oxides

  19. Study of the environmental radiation in Zacatecas City

    International Nuclear Information System (INIS)

    Quirino, L.L.; Mireles, F.; Davila, J.I.; Rios, C.; Lugo, J.F.; Pinedo, J.L.; Lopez, H.; Garcia, M.L.; Soriano, J.M.

    2000-01-01

    A study of detection of environmental radiation in the inner of an office is presented and a comparison of the results is made when the facilities are closed or aired. The used method is based on radiation detection by means of Geiger-Mueller RM 60 and RM 70 detectors with the aid of a personal computer which provides a detection method of radiation in real time. The used method in this study is suggested to detect the variation of radiation in closed or aired environments and as a surveillance system of radiation levels. The obtained results are discussed and they are compared with those obtained in another places. (Author)

  20. Development of high-energy resolution inverse photoemission technique

    International Nuclear Information System (INIS)

    Asakura, D.; Fujii, Y.; Mizokawa, T.

    2005-01-01

    We developed a new inverse photoemission (IPES) machine based on a new idea to improve the energy resolution: off-plane Eagle mounting of the optical system in combination with dispersion matching between incoming electron and outgoing photon. In order to achieve dispersion matching, we have employed a parallel plate electron source and have investigated whether the electron beam is obtained as expected. In this paper, we present the principle and design of the new IPES method and report the current status of the high-energy resolution IPES machine

  1. Study of material properties using channeling radiation

    International Nuclear Information System (INIS)

    Pantell, R.H.; Kephart, J.O.; Klein, R.K.; Park, H.; Berman, B.L.; Datz, S.

    1986-01-01

    A possible application for channeling radiation is for investigating the properties of crystals in which the channeling occurs. In this paper we present some general considerations concerning channeling radiation as a measurement technique, and then we proceed to describe several specific examples

  2. SUM-RULES FOR MAGNETIC DICHROISM IN RARE-EARTH 4F-PHOTOEMISSION

    NARCIS (Netherlands)

    THOLE, BT; VANDERLAAN, G

    1993-01-01

    We present new sum rules for magnetic dichroism in spin polarized photoemission from partly filled shells which give the expectation values of the orbital and spin magnetic moments and their correlations in the ground state. We apply this to the 4f photoemission of rare earths, where the

  3. Iron 1s X-ray photoemission of Fe2O3

    NARCIS (Netherlands)

    Miedema, P. S.; Borgatti, F.; Offi, F.; Panaccione, G.; de Groot, F. M. F.

    We present the Is X-ray photoemission spectrum of alpha-Fe2O3 in comparison with its 2p photoemission spectrum. We show that in case of transition metal oxides, because the 1s core hole is not affected by core hole spin-orbit coupling and almost not affected by core-valence multiplet effects, the Fe

  4. Deep space test bed for radiation studies

    International Nuclear Information System (INIS)

    Adams, James H.; Adcock, Leonard; Apple, Jeffery; Christl, Mark; Cleveand, William; Cox, Mark; Dietz, Kurt; Ferguson, Cynthia; Fountain, Walt; Ghita, Bogdan; Kuznetsov, Evgeny; Milton, Martha; Myers, Jeremy; O'Brien, Sue; Seaquist, Jim; Smith, Edward A.; Smith, Guy; Warden, Lance; Watts, John

    2007-01-01

    The Deep Space Test-Bed (DSTB) Facility is designed to investigate the effects of galactic cosmic rays on crews and systems during missions to the Moon or Mars. To gain access to the interplanetary ionizing radiation environment the DSTB uses high-altitude polar balloon flights. The DSTB provides a platform for measurements to validate the radiation transport codes that are used by NASA to calculate the radiation environment within crewed space systems. It is also designed to support other exploration related investigations such as measuring the shielding effectiveness of candidate spacecraft and habitat materials, testing new radiation monitoring instrumentation, flight avionics and investigating the biological effects of deep space radiation. We describe the work completed thus far in the development of the DSTB and its current status

  5. Studies on application of radiation and radioisotope. Studies on radiation processing

    Energy Technology Data Exchange (ETDEWEB)

    Nho, Young Chang; Jin, J. H.; Kim, K. Y.; Lee, Y. K.; Lee, M. Z.; Jung, S. H.; Park, S. C.; Na, B. Z.; Kim, J. H.; Park, J. S.; Kwon, O. H.

    1997-09-01

    An attempt was made to synthesize adsorbent by radiation grafting of monomers onto polypropylene fabric, and then introducing functional groups such as cation-exchange and anion-exchange. The capacities of the synthesized adsorbents having the cationic and anionic exchange groups were evaluated by determining the degree to adsorb the basic and acidic gas, respectively. Software for RTD analysis was made to analyze data from radiotracer experiments. A pilot plant for practicing tracer experiments was designed and constructed, and experimental procedures for several tracer techniques were established. Radiation source holder, detector collimator, driver unit and software to control them were designed and constructed for column scanning technique. Basic studies for sea sand movement were performed and some tracer experiments were executed to support local industry as well as to gain field experiences. Cellulosic agricultural waste was observed by SEM for structural changes and analysed by thermal gravity analysis and water holding capacity test for the physical characteristics as a function of radiation dose. The number and kind of microorganisms in cellulosic agricultural waste were determined and sterilized by the reasonable radiation dose. The optimal fermentable microorganism is evaluated by the fermentation experiments of various useful strains. (author). 20 refs., 4 tabs., 39 figs.

  6. Studies on application of radiation and radioisotope. Studies on radiation processing

    International Nuclear Information System (INIS)

    Nho, Young Chang; Jin, J. H.; Kim, K. Y.; Lee, Y. K.; Lee, M. Z.; Jung, S. H.; Park, S. C.; Na, B. Z.; Kim, J. H.; Park, J. S.; Kwon, O. H.

    1997-09-01

    An attempt was made to synthesize adsorbent by radiation grafting of monomers onto polypropylene fabric, and then introducing functional groups such as cation-exchange and anion-exchange. The capacities of the synthesized adsorbents having the cationic and anionic exchange groups were evaluated by determining the degree to adsorb the basic and acidic gas, respectively. Software for RTD analysis was made to analyze data from radiotracer experiments. A pilot plant for practicing tracer experiments was designed and constructed, and experimental procedures for several tracer techniques were established. Radiation source holder, detector collimator, driver unit and software to control them were designed and constructed for column scanning technique. Basic studies for sea sand movement were performed and some tracer experiments were executed to support local industry as well as to gain field experiences. Cellulosic agricultural waste was observed by SEM for structural changes and analysed by thermal gravity analysis and water holding capacity test for the physical characteristics as a function of radiation dose. The number and kind of microorganisms in cellulosic agricultural waste were determined and sterilized by the reasonable radiation dose. The optimal fermentable microorganism is evaluated by the fermentation experiments of various useful strains. (author). 20 refs., 4 tabs., 39 figs

  7. Study of solar radiation prediction and modeling of relationships between solar radiation and meteorological variables

    International Nuclear Information System (INIS)

    Sun, Huaiwei; Zhao, Na; Zeng, Xiaofan; Yan, Dong

    2015-01-01

    Highlights: • We investigate relationships between solar radiation and meteorological variables. • A strong relationship exists between solar radiation and sunshine duration. • Daily global radiation can be estimated accurately with ARMAX–GARCH models. • MGARCH model was applied to investigate time-varying relationships. - Abstract: The traditional approaches that employ the correlations between solar radiation and other measured meteorological variables are commonly utilized in studies. It is important to investigate the time-varying relationships between meteorological variables and solar radiation to determine which variables have the strongest correlations with solar radiation. In this study, the nonlinear autoregressive moving average with exogenous variable–generalized autoregressive conditional heteroscedasticity (ARMAX–GARCH) and multivariate GARCH (MGARCH) time-series approaches were applied to investigate the associations between solar radiation and several meteorological variables. For these investigations, the long-term daily global solar radiation series measured at three stations from January 1, 2004 until December 31, 2007 were used in this study. Stronger relationships were observed to exist between global solar radiation and sunshine duration than between solar radiation and temperature difference. The results show that 82–88% of the temporal variations of the global solar radiation were captured by the sunshine-duration-based ARMAX–GARCH models and 55–68% of daily variations were captured by the temperature-difference-based ARMAX–GARCH models. The advantages of the ARMAX–GARCH models were also confirmed by comparison of Auto-Regressive and Moving Average (ARMA) and neutral network (ANN) models in the estimation of daily global solar radiation. The strong heteroscedastic persistency of the global solar radiation series was revealed by the AutoRegressive Conditional Heteroscedasticity (ARCH) and Generalized Auto

  8. Radiation

    International Nuclear Information System (INIS)

    Winther, J.F.; Ulbak, K.; Dreyer, L.; Pukkala, E.; Oesterlind, A.

    1997-01-01

    Exposure to solar and ionizing radiation increases the risk for cancer in humans. Some 5% of solar radiation is within the ultraviolet spectrum and may cause both malignant melanoma and non-melanocytic skin cancer; the latter is regarded as a benign disease and is accordingly not included in our estimation of avoidable cancers. Under the assumption that the rate of occurrence of malignant melanoma of the buttocks of both men and women and of the scalp of women would apply to all parts of the body in people completely unexposed to solar radiation, it was estimated that approximately 95% of all malignant melanomas arising in the Nordic populations around the year 2000 will be due to exposure to natural ultraviolet radiation, equivalent to an annual number of about 4700 cases, with 2100 in men and 2600 in women, or some 4% of all cancers notified. Exposure to ionizing radiation in the Nordic countries occurs at an average effective dose per capita per year of about 3 mSv (Iceland, 1.1 mSv) from natural sources, and about 1 mSv from man-made sources. While the natural sources are primarily radon in indoor air, natural radionuclides in food, cosmic radiation and gamma radiation from soil and building materials, the man-made sources are dominated by the diagnostic and therapeutic use of ionizing radiation. On the basis of measured levels of radon in Nordic dwellings and associated risk estimates for lung cancer derived from well-conducted epidemiological studies, we estimated that about 180 cases of lung cancer (1% of all lung cancer cases) per year could be avoided in the Nordic countries around the year 2000 if indoor exposure to radon were eliminated, and that an additional 720 cases (6%) could be avoided annually if either radon or tobacco smoking were eliminated. Similarly, it was estimated that the exposure of the Nordic populations to natural sources of ionizing radiation other than radon and to medical sources will each give rise to an annual total of 2120

  9. Angle-resolved photoemission spectroscopy with 9-eV photon-energy pulses generated in a gas-filled hollow-core photonic crystal fiber

    OpenAIRE

    Bromberger, H.; Ermolov, A.; Belli, F.; Liu, H.; Calegari, F.; Chavez-Cervantes, M.; Li, M. T.; Lin, C. T.; Abdolvand, A.; Russell, P. St. J.; Cavalleri, A.; Travers, J. C.; Gierz, I.

    2015-01-01

    A recently developed source of ultraviolet radiation, based on optical soliton propagation in a gas-filled hollow-core photonic crystal fiber, is applied here to angle-resolved photoemission spectroscopy (ARPES). Near-infrared femtosecond pulses of only few {\\mu}J energy generate vacuum ultraviolet (VUV) radiation between 5.5 and 9 eV inside the gas-filled fiber. These pulses are used to measure the band structure of the topological insulator Bi2Se3 with a signal to noise ratio comparable to ...

  10. Recent studies on UV radiation in Brazil

    Science.gov (United States)

    Correa, M. P.; Ceballos, J. C.; Moregula, A.; Okuno, E.; Fausto, A.; Mol, A.; Santos, J. C.

    2009-04-01

    This presentation shows a summary of UV index measurements performed in the last years in Southeastern (SE) and Northeastern (NE) Brazilian regions. Brazil has an area of 8.5 million km2 distributed between latitudes 5˚ N and 35˚ S and longitudes 5˚ W and 75˚ W. SE is the most important economic pole of South America and the NE coast is an important tourist region. This large area has a great diversity of climatic, atmospheric and geographical conditions in addition to very diverse social and cultural habits. Non-melanoma skin cancer (NMSC) is an epidemiological health problem with more than 120,000 new cases each year. The most of these cases are found in the South and Southeast regions, with about 70 new NMSC per 100,000 inhabitants. Solar Light UV501 biometers are installed in the SE cities of São Paulo (23.6˚ S, 46.7˚ W, 865 m ASL), Itajubá/Minas Gerais (22.4˚ S; 45.5˚ W, 846 m ASL) and the NE city of Ilhéus/Bahia (14.8˚ S; 39.3˚ W; 54 m ASL). First measurements began in 2005 in São Paulo city, while Itajubá and Ilhéus have regular measurements from the beginning of 2008. Other studies related to the UV radiation modeling and interactions with atmosphere components, as ozone, aerosols and clouds, have also been performed. For example: a) UVI modelling calculations performed by a multiple-scattering spectral models; b) studies on the aerosol radiative properties based on satellite (MODIS/Terra-Aqua) and ground-based (Aeronet) observation; c) ozone content variability from satellite (OMI/Aura) and ground-based (Microtops ozonometer) measurements; d) behavioral profile of the population, as regarding habits of solar exposure and sun protection measures. Results show that more than 75% of the measurements conducted in the summer (outside noon) can be classified as upper than high UVI according to World Health Organization (WHO) recommended categories: Low (UVI UV radiation levels to have a population very exposed during its

  11. Radiation

    International Nuclear Information System (INIS)

    2013-01-01

    The chapter one presents the composition of matter and atomic theory; matter structure; transitions; origin of radiation; radioactivity; nuclear radiation; interactions in decay processes; radiation produced by the interaction of radiation with matter

  12. Studies on the strategies of minimizing radiation damage

    Energy Technology Data Exchange (ETDEWEB)

    Chung, Hee Yong; Sohn, Young Sook

    1998-04-01

    We studied on the strategies of minimizing radiation damage in animal system. To this end we studied following areas of research (1) mechanisms involved in bone marrow damage after total body irradiation, (2) extraction of components that are useful in protecting hematopoietic system from radiation damage, (3) cell therapy approach in restoring the damaged tissue, (4) development of radioprotective chemical reagent, and (5) epidemiological study on the population that had been exposed to radiation.

  13. Studies on the strategies of minimizing radiation damage

    International Nuclear Information System (INIS)

    Chung, Hee Yong; Sohn, Young Sook

    1998-04-01

    We studied on the strategies of minimizing radiation damage in animal system. To this end we studied following areas of research 1) mechanisms involved in bone marrow damage after total body irradiation, 2) extraction of components that are useful in protecting hematopoietic system from radiation damage, 3) cell therapy approach in restoring the damaged tissue, 4) development of radioprotective chemical reagent, and 5) epidemiological study on the population that had been exposed to radiation

  14. Photoemission spectroscopy of surfaces and adsorbates

    International Nuclear Information System (INIS)

    Chiang, T.C.; Kaindl, G.; Himpsel, F.J.; Eastman, D.E.

    1982-01-01

    Core level photoelectron spectroscopy is providing new information concerning the electronic properties of adsorbates and surfaces. Several examples will be discussed, including studies of adsorbed rare gas submonolayers and multilayers as well as clean metal surfaces. For rare gas multilayers adsorbed on metal surfaces, the photoelectrons and Auger electrons exhibit well-resolved increases in kinetic energy with decreasing distance between the excited atom and the substrate, allowing a direct labeling of the layers. These energy shifts are mainly due to the substrate screening effects, and can be described well by an image-charge model. For a Kr/Xe bilayer system prepared by first coating a Pd substrate with a monolayer of Kr and then overcoating with a layer of Xe, a thermally activated layer inversion process is observed when the temperature is raised, with Xe coming in direct contact with the substrate. For rare gas submonolayers adsorbed on the Al(111) surface, coverage-dependent core level shift and work function measurements provide information about the adatom spatial distributions, polarizabilities, and dipole moments for the ground and excited states. We have also studied the 2p core level shifts for a clean Al(001) surface relative to the bulk. The shifts have a large contribution from the initial-state effects

  15. Radiation protection in well logging: case studies in the Sudan

    International Nuclear Information System (INIS)

    Eltayeb, B. A.

    2010-12-01

    This study is performed to improve radiation protection level in well logging include tow case studies in Sudan (Lost or misplaced sources). General review of radiation and radiation protection basic concept is highlighted discussed. Also preview of well logging practice and source of radiation use in well logging, safety of radiation sources, storage and manage of not use sources (weak sources) and protection of worker and potential exposure for public and worker, investigations in cause of lost or misplaced sources in well. Assessment was made in well logging using checklist prepared in accordance with the International Atomic Energy Agency IAEA basic safety standard, International Committee for Radiological Protection ICRP and safety in transport of radiation sources. The checklist includes all requirement of radiation protection. It is found that all requirement was present except the delay of calibration of radiation detectors, the movement of radiation sources form storage to base of manipulated area need adequate care for shielding and safe transport and personal monitoring service must be provide in Sudan. Investigation was made in cause of lose of nine radiation source in well it is found that all those sources were loss in different depth in the well and with deferent location and there was no risk because there was no contamination of fluids which caused by damage of loss sources. Some recommendations were stated that, if implemented could improve the status of radiation protection in well logging. (Author)

  16. Core Flight Executive Software Radiation Mitigation Study

    Data.gov (United States)

    National Aeronautics and Space Administration — The reliability of SmallSat / CubeSat missions may be increased by using software radiation mitigation for single event upsets (SEUs). Implementing protection in...

  17. Study of prochlorperazine (Stemetil) in radiation sickness

    International Nuclear Information System (INIS)

    Dutta, A.K.

    1976-01-01

    The incidence of radiation sickness and the efficacy of prochlorperazine in alleviating it among the patients under radiotherapy have been investigated. 116 patients from those under radiotherapy were randomly chosen. 38% of this sample developed radiation sickness symptoms (nausea and vomiting). The onset of symptoms occurred in the earlier periods of radiotherapy. The younger and older group were more susceptible to side effects of radiation. Prochlorperazine was administered immediately after the onset of symptoms of radiation sickness in the dose schedule of 10 mg twice daily for adults and was continued for 5 to 10 days after the alleviation of the symptoms. This was found to be effective in all patients. (M.G.B.)

  18. Simulation study of transverse optical klystron radiation

    International Nuclear Information System (INIS)

    Xu Hongliang; Diao Caozheng; Liu Jinying; He Duohui; Jia Qika; Wang Xiangqi

    1997-01-01

    The radiation from a transverse optical klystron (TOK) is calculated by far field approximation equation and numerical integration, in which the effects of electron-beam emittance and energy spread are considered. Accurate electron-beam profiles have been experimentally determined and modeled by the Monte Carlo method. The calculated spectra illustrate the emittance of Hefei storage ring imposes on the spontaneous radiation of TOK

  19. Study of radiation-induced chromosomal aberrations

    International Nuclear Information System (INIS)

    Wolfring, E.

    2004-06-01

    A method for determining chromosomal aberrations was established for the purpose of examining the relative biological effectiveness (RBE) of photon radiation with respect to mammary epithelium cells. Cells were exposed to 25 kV X-radiation and to 200 kV X-radiation for comparison and the resulting concentrations of chromosomal aberrations were compared. The RBE M value for radiation-induced fragmentation was found to be 4.2 ± 2.4, while the RBE M value for radiation-induced generation of dicentric chromosomes was found to be 0.5 ± 0.5. In addition to the evaluation of chromosomal aberrations the number of cell cycles undergone by the cells was monitored by means of BrDU staining. As expected, the proportion of cells which underwent more than one cell cycle following exposure to 5 Gy was very low in both cases, amounting to 1.9% (25 kV) and 3.2 (200 kV). Non-radiated cells yielded control values of 26.0% and 12.6%, suggesting variations in external conditions from day to day

  20. Studies on application of radiation and radioisotopes -Studies on radiation processing-

    International Nuclear Information System (INIS)

    Jin, Joon Hah; Yoon, Byung Mok; Kim, Kee Yub; Noh, Yung Chang; Lee, Yung Keun; Lee, Myun Joo; Park, Soon Chul; Nah, Bong Joo; Kim, Jae Hoh; Byun, Hyung Jik

    1995-07-01

    Using γ-ray and electron beam, acrylic acid was grafted on polyethylene film in the presence of additives such as acid and metallic salts. The effect of metal salts and acid on the graft yield was evaluated. The graft mechanism and the physical property of grafted films were also examined. Radiation sensitivities of pathogenic microbes in waste sludges were determined to get theoretical radiation dose for disinfection. Experimental radiation dose for disinfection was investigated using real activated and digestive sludge. Feasibility of the method was studied from the experimental results. Virgin, waste and regenerated activated carbon were irradiated with electron beam with and without steam. Micropore distribution, BET surface area and sorption capacity were measured before and after irradiation. The residence time distributions of flue gas in the irradiation chamber of an electron beam flue gas treatment plant to study the effect of baffles were measured. The flow rates of gaseous material in the propylene production plant were measured to identify the origin of it's malfunction. The equipment for column scanning were designed for production. 45 figs, 10 tabs, 30 refs. (Author)

  1. Studies on application of radiation and radioisotopes -Studies on radiation processing-

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Joon Hah; Yoon, Byung Mok; Kim, Kee Yub; Noh, Yung Chang; Lee, Yung Keun; Lee, Myun Joo; Park, Soon Chul; Nah, Bong Joo; Kim, Jae Hoh; Byun, Hyung Jik [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

    1995-07-01

    Using {gamma}-ray and electron beam, acrylic acid was grafted on polyethylene film in the presence of additives such as acid and metallic salts. The effect of metal salts and acid on the graft yield was evaluated. The graft mechanism and the physical property of grafted films were also examined. Radiation sensitivities of pathogenic microbes in waste sludges were determined to get theoretical radiation dose for disinfection. Experimental radiation dose for disinfection was investigated using real activated and digestive sludge. Feasibility of the method was studied from the experimental results. Virgin, waste and regenerated activated carbon were irradiated with electron beam with and without steam. Micropore distribution, BET surface area and sorption capacity were measured before and after irradiation. The residence time distributions of flue gas in the irradiation chamber of an electron beam flue gas treatment plant to study the effect of baffles were measured. The flow rates of gaseous material in the propylene production plant were measured to identify the origin of it`s malfunction. The equipment for column scanning were designed for production. 45 figs, 10 tabs, 30 refs. (Author).

  2. Radiation studies on the microflora in a High-level radiation environment

    International Nuclear Information System (INIS)

    Zahiera, T.S.

    1988-01-01

    Radiation sensitivities of microflora in the air environment of the irradiation room of the 60 CO industrial irradiation facility of NCRRT was studied. The isolated microflora was identified to be the Gram positive micrococci, and the gram positive bacilli: coagulans and laterosporous. The study of the dose-survival counts dependence of the colonies showed the existance of the combination of at least two groups of micro-organisms with different sensitivities to radiation. The value of the radiation resistant group was found to be 2.2 10kGy. A method is presented to estimate the amount of each group in the initial culture. A study of the dependence of radiation lethality on the dose rate of radiation on the aerobic dry microbes showed no significant effect in the dose-rate range from 330 down to 44 Gy.min

  3. Epidemiological studies on radiation carcinogenesis in human populations following acute exposure: nuclear explosions and medical radiation

    International Nuclear Information System (INIS)

    Fabrikant, J.I.

    1981-05-01

    The current knowledge of the carcinogenic effect of radiation in man is considered. The discussion is restricted to dose-incidence data in humans, particularly to certain of those epidemiological studies of human populations that are used most frequently for risk estimation for low-dose radiation carcinogenesis in man. Emphasis is placed solely on those surveys concerned with nuclear explosions and medical exposures

  4. Magnetic x-ray linear dichroism in resonant and non-resonant Gd 4f photoemission

    Energy Technology Data Exchange (ETDEWEB)

    Mishra, S.; Gammon, W.J.; Pappas, D.P. [Virginia Commonwealth Univ., Richmond, VA (United States)] [and others

    1997-04-01

    The enhancement of the magnetic linear dichroism in resonant 4f photoemission (MLDRPE) is studied from a 50 monolayer film of Gd/Y(0001). The ALS at beamline 7.0.1 provided the source of linearly polarized x-rays used in this study. The polarized light was incident at an angle of 30 degrees relative to the film plane, and the sample magnetization was perpendicular to the photon polarization. The linear dichroism of the 4f core levels is measured as the photon energy is tuned through the 4d-4f resonance. The authors find that the MLDRPE asymmetry is strongest at the resonance. Near the threshold the asymmetry has several features which are out of phase with the fine structure of the total yield.

  5. Magnetic x-ray linear dichroism in resonant and non-resonant Gd 4f photoemission

    International Nuclear Information System (INIS)

    Mishra, S.; Gammon, W.J.; Pappas, D.P.

    1997-01-01

    The enhancement of the magnetic linear dichroism in resonant 4f photoemission (MLDRPE) is studied from a 50 monolayer film of Gd/Y(0001). The ALS at beamline 7.0.1 provided the source of linearly polarized x-rays used in this study. The polarized light was incident at an angle of 30 degrees relative to the film plane, and the sample magnetization was perpendicular to the photon polarization. The linear dichroism of the 4f core levels is measured as the photon energy is tuned through the 4d-4f resonance. The authors find that the MLDRPE asymmetry is strongest at the resonance. Near the threshold the asymmetry has several features which are out of phase with the fine structure of the total yield

  6. Soft x-ray photoemission investigation of the oxidation of CuInSe/sub 2/ thin films

    International Nuclear Information System (INIS)

    Zurcher, P.; Nelson, A.J.; Johnson, P.; Lapeyre, G.J.; Noufi, R.

    1987-01-01

    CuInSe/sub 2/ films are used as absorber layers in heterojunction thin film solar cells. It has been demonstrated that, depending on the stoichiometry, oxygen annealing can make CuInSe/sub 2/ films more p-type or even convert n-type films into p-type while subsequent reduction with hydrazine will reverse such processes. Using synchrotron radiation soft x-ray photoemission spectroscopy, the authors found associated with the hydrazine reduced films an In1+ state that converts into In3+ under the influence of oxygen at elevated sample temperatures. The samples investigated were grown in a way that the top several thousand Angstroms are increasingly Cu-poor and In-rich. It is this region which is sampled by the surface sensitive technique of photoemission. The Cu-poor/In-rich top regions will most likely have a large number of intrinsic In on Cu-site defects leaving the In in a 1+ state. All the oxidation and reduction results and the associated changes in majority carrier concentrations and type conversions can be understood in terms of oxygem/In/sub Cu/-defect interactions

  7. Radiation effects on video imagers

    International Nuclear Information System (INIS)

    Yates, G.J.; Bujnosek, J.J.; Jaramillo, S.A.; Walton, R.B.; Martinez, T.M.; Black, J.P.

    1985-01-01

    Radiation sensitivity of several photoconductive, photoemissive, and solid state silicon-based video imagers was measured by analyzing stored photocharge induced by irradiation with continuous and pulsed sources of high energy photons and neutrons. Transient effects as functions of absorbed dose, dose rate, fluences, and ionizing particle energy are presented

  8. Studies on radiation stability of polymers

    International Nuclear Information System (INIS)

    Jiazhen Sun; Xiaoguang Zhong

    1999-01-01

    Fluoropolyimide (FPI) is crosslinked by gamma-irradiation at high temperature. After crosslinking, the glass transition temperature is increased with increasing dose. High temperature tensile strength is also increased with increasing dose. The high temperature water resistance property is improved markedly. XPS results show that the fluoro-atom in the CF 3 group is decreased during radiation crosslinking of PFI, so the crosslinking reaction of PFI is thought to proceed through defluorination. Likewise, certain common polyolefins, such as polytetrafluoroethylene, which undergo primarily chain scission when irradiated at room temperature, can be crosslinked by irradiation at high temperature. This dramatically improves their subsequent radiation resistance. We have also been able to achieve improved radiation resistance by irradiation of certain blends of a predominantly scissioning polymer with a predominantly crosslinking polymer. (author)

  9. Studies and Development of Radiation Processed Nanomaterials

    Energy Technology Data Exchange (ETDEWEB)

    Varshney, Lalit; Sabharwal, Sunil; Francis, Sanju; Biswal, Jayashree [Radiation Technology Development Section, Bhabha Atomic Research Centre, Mumbai (India)

    2009-07-01

    Nanotechnology is the emerging technology that deals with processing, manipulating and manufacturing devices and products at the microscopic scale of molecules or atoms with structures smaller than 100 nanometers. Realizing its potential, Government of India spending on R&D in nanotechnology has gone up by an order of magnitude in last 5 years through various national and international programs. High energy gamma radiation and electron beams could be a useful tool to create innovative and newer nano-materials for various applications in medical field for treatment and detection purposes. Considering its certain advantage for producing nano-materials, radiation technology will play a crucial role in development of such materials. Research and development in the area of nano--particles on polymer films, hydrogels, silica particles and their nano-clusters using radiation technology could be a possible route for development of new functional nano-materials. (author)

  10. Studies and Development of Radiation Processed Nanomaterials

    International Nuclear Information System (INIS)

    Varshney, Lalit; Sabharwal, Sunil; Francis, Sanju; Biswal, Jayashree

    2009-01-01

    Nanotechnology is the emerging technology that deals with processing, manipulating and manufacturing devices and products at the microscopic scale of molecules or atoms with structures smaller than 100 nanometers. Realizing its potential, Government of India spending on R&D in nanotechnology has gone up by an order of magnitude in last 5 years through various national and international programs. High energy gamma radiation and electron beams could be a useful tool to create innovative and newer nano-materials for various applications in medical field for treatment and detection purposes. Considering its certain advantage for producing nano-materials, radiation technology will play a crucial role in development of such materials. Research and development in the area of nano--particles on polymer films, hydrogels, silica particles and their nano-clusters using radiation technology could be a possible route for development of new functional nano-materials. (author)

  11. A study of Monte Carlo radiative transfer through fractal clouds

    Energy Technology Data Exchange (ETDEWEB)

    Gautier, C.; Lavallec, D.; O`Hirok, W.; Ricchiazzi, P. [Univ. of California, Santa Barbara, CA (United States)] [and others

    1996-04-01

    An understanding of radiation transport (RT) through clouds is fundamental to studies of the earth`s radiation budget and climate dynamics. The transmission through horizontally homogeneous clouds has been studied thoroughly using accurate, discreet ordinates radiative transfer models. However, the applicability of these results to general problems of global radiation budget is limited by the plane parallel assumption and the fact that real clouds fields show variability, both vertically and horizontally, on all size scales. To understand how radiation interacts with realistic clouds, we have used a Monte Carlo radiative transfer model to compute the details of the photon-cloud interaction on synthetic cloud fields. Synthetic cloud fields, generated by a cascade model, reproduce the scaling behavior, as well as the cloud variability observed and estimated from cloud satellite data.

  12. Studies on the genetic effects of radiation

    International Nuclear Information System (INIS)

    Cheong, Kyu Hoi; Cheong, Hae Won; Cheon, Kwi Cheong; Kim, Chae Sung

    1985-01-01

    To investigate genetic damage of radiation in mammalian male germ cell, sperm head counts, frequency of sperm with abnormal head shape, fertility, activity of LDH-X, and the induction of unscheduled DNA synthesis in testis were measured periodically after irradiation. Sperm head counts and activities of LDH-X in testes were gradually reduced by increased radiation dose and with the passing of the time after irradiation. Frequency occurrence of sperm of abnormal head shape, sterile period, and the induction of unscheduled DNA synthesis were increased. (Author)

  13. Pilot study for natural radiation survey

    International Nuclear Information System (INIS)

    Brown, L.; Driscoll, C.M.H.; Green, B.M.R.; Miles, J.C.H.

    1983-01-01

    NRPB's national survey of natural radiation exposure in homes commenced in 1982 and will run until 1984. A pilot survey was undertaken in over 100 homes for one year, using passive thermoluminescent dosemeters to measure external radiation from terrestrial and cosmic sources and passive radon dosemeters to measure the radon-222 gas concentration. A preliminary analysis of the results obtained from the pilot survey is given. The main value of the pilot survey was in providing experience and various administrative and scientific procedures have been simplified or automated for the national survey. (U.K.)

  14. Magnetic dichroism in photoemission: a new element-specific magnetometer with atomic-layer resolution

    International Nuclear Information System (INIS)

    Starke, K.; Arenholz, E.; Kaindl, G.

    1998-01-01

    Full text: Magnetic coupling in layered metallic structures has become a key issue in thin-film magnetism since the observation of oscillatory exchange coupling across non-ferromagnetic spacer layers. Although this phenomenon was discovered in rare earths (RE) superlattices, mostly transition-metal systems have been studied and are now applied in data-storage industry. An understanding of the coupling mechanisms has been reached after a fabrication of high-quality interfaces became possible. It allowed, in particular, the experimental finding of induced ferromagnetic order in 'nonmagnetic' atomic layers near an interface, using element-specific probes such as magnetic circular dichroism in x-ray absorption. - In layered RE systems, by contrast, the well known intermiscibility has prevented a preparation of atomically sharp interfaces, and all RE superlattices studied so far showed interdiffusion zones of several atomic layers. In the present overview, we report the first fabrication of atomically flat heteromagnetic RE interfaces, their structural characterization and their magnetic analysis using magnetic dichroism in photoemission (MDPE). This new tool gives access to the magnetization of individual atomic layers near interfaces in favourite cases. Merits of MDPE as a magnetometer are demonstrated at the example of Eu/Gd(0001), where chemical shifts of core-level photoemission lines allow to spectroscopically separate up to four different atomic layers. The high surface sensitivity of MDPE, together with the well known dependence of the core-level binding energies on the coordination number of the photo emitting atom, opens the door to future site-specific studies of magnetism in sub-monolayer systems such as 'nanowires'

  15. Mechanistic studies of neoplastic cell transformation by ionizing radiation

    International Nuclear Information System (INIS)

    Yang, T.C.; Craise, L.M.; Tobias, C.A.

    1982-01-01

    As part of the Biology and Medicine heavy-ion radiation program, we are systematically investigating the potential carcinogenic and mutagenic effects of high- and low-linear energy transfer (LET) radiation at the cellular level. From these studies, we anticipate additional insight into the molecular and cellular mechanisms of radiation carcinogenesis. Such results should provide quantitative information useful for assessing the undesirable biological effects of cosmic rays in space. Some of our recent experimental results are presented here

  16. Atomic photoelectron-spectroscopy studies using synchrotron radiation

    International Nuclear Information System (INIS)

    Kobrin, P.H.

    1983-02-01

    Photoelectron spectroscopy combined with tunable synchrotron radiation has been used to study the photoionization process in several atomic systems. The time structure of the synchrotron radiation source at the Stanford Synchrotron Radiation Laboratory (SSRL) was used to record time-of-flight (TOF) photoelectron spectra of gaseous Cd, Hg, Ne, Ar, Ba, and Mn. The use of two TOF analyzers made possible the measurement of photoelectron angular distributions as well as branching ratios and partial cross sections

  17. General theoretical description of angle-resolved photoemission spectroscopy of van der Waals structures

    Science.gov (United States)

    Amorim, B.

    2018-04-01

    We develop a general theory to model the angle-resolved photoemission spectroscopy (ARPES) of commensurate and incommensurate van der Waals (vdW) structures, formed by lattice mismatched and/or misaligned stacked layers of two-dimensional materials. The present theory is based on a tight-binding description of the structure and the concept of generalized umklapp processes, going beyond previous descriptions of ARPES in incommensurate vdW structures, which are based on continuous, low-energy models, being limited to structures with small lattice mismatch/misalignment. As applications of the general formalism, we study the ARPES bands and constant energy maps for two structures: twisted bilayer graphene and twisted bilayer MoS2. The present theory should be useful in correctly interpreting experimental results of ARPES of vdW structures and other systems displaying competition between different periodicities, such as two-dimensional materials weakly coupled to a substrate and materials with density wave phases.

  18. Schottky barrier measurements on individual GaAs nanowires by X-ray photoemission microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Di Mario, Lorenzo [IMM-CNR, via del Fosso del Cavaliere 100, 00133 Rome (Italy); Turchini, Stefano, E-mail: stefano.turchini@cnr.it [ISM-CNR, via del Fosso del Cavaliere 100, 00133 Rome (Italy); Zamborlini, Giovanni; Feyer, Vitaly [Peter Grünberg Institute (PGI-6) and JARA-FIT, Research Center Jülich, 52425 Jülich (Germany); Tian, Lin [IMM-CNR, via del Fosso del Cavaliere 100, 00133 Rome (Italy); Schneider, Claus M. [Peter Grünberg Institute (PGI-6) and JARA-FIT, Research Center Jülich, 52425 Jülich (Germany); Fakultät für Physik and Center for Nanointegration Duisburg-Essen (CENIDE), Universität Duisburg-Essen, D-47048 Duisburg (Germany); Rubini, Silvia [IOM-CNR, TASC Laboratory, Basovizza 34149, Trieste (Italy); Martelli, Faustino, E-mail: faustino.martelli@cnr.it [IMM-CNR, via del Fosso del Cavaliere 100, 00133 Rome (Italy)

    2016-11-15

    Highlights: • The Schottky barrier at the interface between Cu and GaAs nanowires was measured. • Individual nanowires were investigated by X-ray Photoemission Microscopy. • The Schottky barrier at different positions along the nanowire was evaluated. - Abstract: We present measurements of the Schottky barrier height on individual GaAs nanowires by means of x-ray photoelectron emission microscopy (XPEEM). Values of 0.73 and 0.51 eV, averaged over the entire wires, were measured on Cu-covered n-doped and p-doped GaAs nanowires, respectively, in agreement with results obtained on bulk material. Our measurements show that XPEEM can become a feasible and reliable investigation tool of interface formation at the nanoscale and pave the way towards the study of size-dependent effects on semiconductor-based structures.

  19. An aberration corrected photoemission electron microscope at the advanced light source

    International Nuclear Information System (INIS)

    Feng, J.; MacDowell, A.A.; Duarte, R.; Doran, A.; Forest, E.; Kelez, N.; Marcus, M.; Munson, D.; Padmore, H.; Petermann, K.; Raoux, S.; Robin, D.; Scholl, A.; Schlueter, R.; Schmid, P.; Stohr, J.; Wan, W.; Wei, D.H.; Wu, Y.

    2003-01-01

    Design of a new aberration corrected Photoemission electron microscope PEEM3 at the Advanced Light Source is outlined. PEEM3 will be installed on an elliptically polarized undulator beamline and will be used for the study of complex materials at high spatial and spectral resolution. The critical components of PEEM3 are the electron mirror aberration corrector and aberration-free magnetic beam separator. The models to calculate the optical properties of the electron mirror are discussed. The goal of the PEEM3 project is to achieve the highest possible transmission of the system at resolutions comparable to our present PEEM2 system (50 nm) and to enable significantly higher resolution, albeit at the sacrifice of intensity. We have left open the possibility to add an energy filter at a later date, if it becomes necessary driven by scientific need to improve the resolution further

  20. Interband quasiparticle scattering in superconducting LiFeAs reconciles photoemission and tunneling measurements.

    Science.gov (United States)

    Hess, Christian; Sykora, Steffen; Hänke, Torben; Schlegel, Ronny; Baumann, Danny; Zabolotnyy, Volodymyr B; Harnagea, Luminita; Wurmehl, Sabine; van den Brink, Jeroen; Büchner, Bernd

    2013-01-04

    Several angle-resolved photoemission spectroscopy (ARPES) studies reveal a poorly nested Fermi surface of LiFeAs, far away from a spin density wave instability, and clear-cut superconducting gap anisotropies. On the other hand a very different, more nested Fermi surface and dissimilar gap anisotropies have been obtained from quasiparticle interference (QPI) data, which were interpreted as arising from intraband scattering within holelike bands. Here we show that this ARPES-QPI paradox is completely resolved by interband scattering between the holelike bands. The resolution follows from an excellent agreement between experimental quasiparticle scattering data and T-matrix QPI calculations (based on experimental band structure data), which allows disentangling interband and intraband scattering processes.

  1. Short-period oscillations in photoemission from thin films of Cr(100)

    Science.gov (United States)

    Vyalikh, Denis V.; Zahn, Peter; Richter, Manuel; Dedkov, Yu. S.; Molodtsov, S. L.

    2005-07-01

    Angle-resolved photoemission (PE) study of thin films of Cr grown on Fe(100) reveals thickness-dependent short-period oscillations of the PE intensity close to the Fermi energy at k‖˜0 . The oscillations are assigned to quantum-well states (QWS) caused by the nesting between the Fermi-surface sheets around the Γ and the X points in the Brillouin zone of antiferromagnetic Cr. The experimental data are confirmed by density-functional calculations applying a screened Korringa-Kohn-Rostoker Green’s function method. The period of the experimentally observed QWS oscillations amounts to about 2.6 monolayers and is larger than the fundamental 2-monolayer period of antiferromagnetic coupling in Cr.

  2. An experimental study on radiation hepatitis

    International Nuclear Information System (INIS)

    Kang, Ik Won; Park, Charn Il; Kim, Chu Wan

    1981-01-01

    The effect of radiation on the liver should be of unusual interest in as much as there are two highly specialized kinds of epithelium besides an important endothelial system and vascular and fibrous elements to compare. But there are several difficulties in the way of a knowledge of the sensitivity and reaction of the liver to radiation. Perhaps the most important is the regenerative ability of the liver cells. It has been assumed that the liver as an organ is relatively resistant to radiation injury. Yet there are reports of necorsis of the liver in man resulting from doses of radiation which have not caused a skin reaction or any demonstrable effect on the stomach. The author made an experiment to elucidate more clearly the changes in serum enzymes and histopathology of rat's liver following irradiation to the liver with a single dose of 2,000 rads. The results obtained are as follows: 1. Serum SGOT activities were significantly elevated, 1 and 2 weeks after irradiation, and normalized after 4 weeks. 2. Serum SGPT activities were significantly elevated 2 weeks after irradiation, and normalized after 4 weeks. 3. Alakline phosphatase activity were significantly elevated 1, 2 and 4 weeks after irradiation, and normalized after 8 weeks. 4. Histopathologic changes were focal necrosis, inflammatory cell infiltrations, loss of intracytoplasmic glycogen particles, and vacuolar degenerations of hepatocytes. It appeared marked 2 weeks after irradiation, restored after 4 weeks, and normalized after 8 weeks

  3. Treatment of radiation enteritis: a comparison study

    International Nuclear Information System (INIS)

    Loiudice, T.A.; Lang, J.A.

    1983-01-01

    Twenty-four patients with severe radiation injury to the small bowel seen over a 4-year period were randomized to four treatment groups: 1) methylprednisolone 80 mg intravenously plus Vivonex-HN, 2 L/day po, 2) methylprednisolone 80 mg intravenously plus total parenteral nutrition, 2.5 L/day, 3) total parenteral nutrition, 2.5 L/day, and 4) Vivonex-HN, 2 L/day po. Patients received nothing by mouth except water in groups II and III, and only Vivonex-HN in groups I and IV. Patients were treated for 8-wk periods. Improvement was gauged by overall nutritional assessment measurements, nitrogen balance data and by radiological and clinical parameters. No significant difference between groups I, II, III, and IV could be found for age, sex, mean radiation dosage, time of onset after radiation therapy, or initial nutritional assessment data. Differences statistically could be found between groups II and III and I and IV regarding nutritional assessment data, nitrogen balance, radiographic and clinical parameters after therapy, with marked improvement noted in groups II and III. We conclude that a treatment regimen consisting of total parenteral nutrition and bowel rest is beneficial in the treatment of radiation enteritis. Methylprednisolone appears to enhance this effect and indeed, may be responsible for a longer lasting response

  4. An experimental study on radiation hepatitis

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Ik Won; Park, Charn Il; Kim, Chu Wan [College of Medicine, Seoul National University, Seoul (Korea, Republic of)

    1981-09-15

    The effect of radiation on the liver should be of unusual interest in as much as there are two highly specialized kinds of epithelium besides an important endothelial system and vascular and fibrous elements to compare. But there are several difficulties in the way of a knowledge of the sensitivity and reaction of the liver to radiation. Perhaps the most important is the regenerative ability of the liver cells. It has been assumed that the liver as an organ is relatively resistant to radiation injury. Yet there are reports of necorsis of the liver in man resulting from doses of radiation which have not caused a skin reaction or any demonstrable effect on the stomach. The author made an experiment to elucidate more clearly the changes in serum enzymes and histopathology of rat's liver following irradiation to the liver with a single dose of 2,000 rads. The results obtained are as follows: 1. Serum SGOT activities were significantly elevated, 1 and 2 weeks after irradiation, and normalized after 4 weeks. 2. Serum SGPT activities were significantly elevated 2 weeks after irradiation, and normalized after 4 weeks. 3. Alakline phosphatase activity were significantly elevated 1, 2 and 4 weeks after irradiation, and normalized after 8 weeks. 4. Histopathologic changes were focal necrosis, inflammatory cell infiltrations, loss of intracytoplasmic glycogen particles, and vacuolar degenerations of hepatocytes. It appeared marked 2 weeks after irradiation, restored after 4 weeks, and normalized after 8 weeks.

  5. Safety of natural radiation exposure. A meta-analysis of epidemiological studies on natural radiation

    International Nuclear Information System (INIS)

    Osaki, S.

    2000-01-01

    People have been exposed every time and everywhere to natural radiation and ''intuitively'' know the safety of this radiation exposure. On the other hand the theory of no threshold value on radiological carcinogenesis is known widely, and many people feel danger with even a smallest dose of radiation exposure. The safety of natural radiation exposure can be used for the risk communication with the public. For this communication, the safety of natural radiation exposure should be proved ''scientifically''. Safety is often discussed scientifically as the risks of the mortality from many practices, and the absolute risks of safe practices on the public are 1E-5 to 1E-6. The risks based on the difference of natural radiation exposure on carcinogenesis have been analyzed by epidemiological studies. Much of the epidemiological studies have been focused on the relationship between radiation doses and cancer mortalities, and their results have been described as relative risks or correlation factors. In respect to the safety, however, absolute risks are necessary for the discussion. Cancer mortalities depend not only on radiation exposure, but also on ethnic groups, sexes, ages, social classes, foods, smoking, environmental chemicals, medical radiation, etc. In order to control these confounding factors, the data are collected from restricted groups or/and localities, but any these ecological studies can not perfectly compensate the confounding factors. So positive or negative values of relative risks or the meaningful correlation factors can not be confirmed that their values are derived originally from the difference of their exposure doses. The absolute risks on these epidemiological studies are also affected by many factors containing radiation exposure. The absolute risk or the upper value of the confidence limit obtained from the epidemiological study which is well regulated confounding factors is possible to be a maximum risk on the difference of the exposure doses

  6. Study of the response of radiation protection monitors in terms of H*(10) in X radiation

    International Nuclear Information System (INIS)

    Nonato, Fernanda B.C.; Carvalho, Valdir S.; Vivolo, Vitor; Caldas, Linda V.E.

    2009-01-01

    The ambient dose equivalent, H * (10), is an operational quantity recommended by the International Commission of radiation Units and Measurements Report 39 for measurements in area monitoring. However, most of the monitoring instruments used in radiation protection in Brazil still use the old quantities exposure rate and absorbed dose rate. Therefore, it is necessary to study how to change the operational quantity to H * (10). In this work, the response of radiation protection monitoring detectors was studied in terms of H * (10) for different energies using standard X-rays (narrow beams) at the Calibration Laboratory of IPEN. (author)

  7. Observation and resonant x-ray optical interpretation of multi-atom resonant photoemission effects in O 1s emission from NiO

    International Nuclear Information System (INIS)

    Mannella, N.; Yang, S.-H.; Mun, B.S.; Garcia de Abajo, F.J.; Kay, A.W.; Sell, B.C.; Watanabe, M.; Ohldag, H.; Arenholz, E.; Young, A.T.; Hussain, Z.; Van Hove, M.A.; Fadley, C.S.

    2006-01-01

    We present experimental and theoretical results for the variation of the O 1s intensity from a NiO(001) surface as the excitation energy is varied through the Ni 2p1/2,3/2 absorption resonances, and as the incidence angle of the radiation is varied from grazing to larger values. For grazing incidence, a strong multi-atom resonant photoemission(MARPE) effect is seen on the O 1s intensity as the Ni 2p resonances are crossed, but its magnitude decreases rapidly as the incidence angle is increased. Resonant x-ray optical (RXRO) calculations are found to predict these effects very well, although the experimental effects are found to decrease at higher incidence angles faster than those in theory. The potential influence of photoelectron diffraction effects on such measurements are also considered, including experimental data with azimuthal-angle variation and corresponding multiple-scattering-diffraction calculations, but we conclude that they do not vary beyond what is expected on the basis of the change in photoelectron kinetic energy. Varying from linear polarization to circular polarization is found to enhance these effects in NiO considerably, although the reasons are not clear. We also discuss the relationship of these measurements to other related interatomic resonance experiments and theoretical developments, and make some suggestions for future studies in this area

  8. Effects of radiation on photographic film. A study

    International Nuclear Information System (INIS)

    Dutton, D.M.

    1971-01-01

    This study of the effects of radiation on photographic film is related to the Nevada Test Site's underground nuclear testing program, which has been active since implementation of the Limited Test Ban Treaty of 1963. Residual radioactivity, which has accidentally been released on several tests, adversely affects the photographic film used in test data acquisition. The report defines this problem in terms of radiation-caused image degradation, radiation/matter interactions, types of radiation released by accidental venting, and the photographic effects of gamma and x radiation. Techniques and experimental findings are documented that may be useful in recovering information from radiation-fogged film. Techniques discussed include processing methods, shielding, image enhancement techniques, and operational handling of potentially irradiated film. (U.S.)

  9. Radiation disinfestation studies on sun dried fish

    International Nuclear Information System (INIS)

    Ahmed, M.; Bhuiya, A.D.; Alam, M.S.; Huda, S.M.S.

    1989-01-01

    A large quantity of dried fish is lost in Bangladesh due to infestation by earwigs, hide beetles and copra beetles in storage godowns. The most destructive pest is the hide beetle, Dermestes maculatus Deg. Earwigs of different developmental stages were exposed to 0.10, 0.20 or 0.30 kGy of gamma rays for disinfestation. There was apparent damage to the control but all treated samples were in good condition and no live insect was observed 3 weeks after starting the experiment. Disinfestation studies of dried mackerel showed that eggs, larval and pupal stages of hide beetles could be inactivated at a dose of 0.20 kGy. A dose of 0.30 kGy killed all adults 2 weeks after irradiation. In the packaging studies, dried mackerel was packed in polythene pouches of different thicknesses. Two controls were maintained, i.e. dried fish with no treatment, control, and dried fish disinfested with heat at 60 deg. C, disinfested control. In experiments with 50 μm thick polythene pouches, the dried fish of irradiation treatments with 0.10 to 1.0 kGy doses and the controls had around 20% moisture content with the exception of disinfested controls which had 13% moisture content. All irradiated samples were free from insect damage. There was heavy damage in the controls due to insects. However, all these treated fish had heavy fungal growth with the exception of the disinfested control. Similar results were obtained with pouches made of 75 μm thick polythene irradiated at doses of 0.50, 1.0, 2.0 and 4.0 kGy. In the final experiments pouches were made of 50, 75 and 100 μm thick polythene and exposed to similar radiation as in the previous experiment. In all the treatments, moisture content was reduced to 13%. heavy insect damage was observed in the control, while all the treated samples were in excellent condition after 5 months of storage. (author). 20 refs, 2 figs, 5 tabs

  10. Photoemission from solids: the transition from solid-state to atomic physics

    International Nuclear Information System (INIS)

    Shirley, D.A.

    1980-08-01

    As the photon energy is increased, photoemission from solids undergoes a slow transition from solid-state to atomic behavior. However, throughout the energy range hν = 10 to 1000 eV or higher both types of phenomena are present. Thus angle-resolved photoemission can only be understood quantitatively if each experimenter recognizes the presence of band-structure, photoelectron diffraction, and photoelectron asymmetry effects. The quest for this understanding will build some interesting bridges between solid-state and atomic physics and should also yield important new insights about the phenomena associated with photoemission

  11. Electric field stimulation setup for photoemission electron microscopes.

    Science.gov (United States)

    Buzzi, M; Vaz, C A F; Raabe, J; Nolting, F

    2015-08-01

    Manipulating magnetisation by the application of an electric field in magnetoelectric multiferroics represents a timely issue due to the potential applications in low power electronics and the novel physics involved. Thanks to its element sensitivity and high spatial resolution, X-ray photoemission electron microscopy is a uniquely suited technique for the investigation of magnetoelectric coupling in multiferroic materials. In this work, we present a setup that allows for the application of in situ electric and magnetic fields while the sample is analysed in the microscope. As an example of the performances of the setup, we present measurements on Ni/Pb(Mg(0.66)Nb(0.33))O3-PbTiO3 and La(0.7)Sr(0.3)MnO3/PMN-PT artificial multiferroic nanostructures.

  12. Angle-resolved photoemission spectroscopy on iron-chalcogenide superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Maletz, Janek; Zabolotnyy, Volodymyr; Evtushinsky, Daniil; Thirupathaiah, Setti; Wolter-Giraud, Anja; Harnagea, Luminita; Kordyuk, Alexander; Borisenko, Sergey [IFW Dresden (Germany); Yaresko, Alexander [MPI-FKF, Stuttgart (Germany); Vasiliev, Alexander [Moscow State University (Russian Federation); Chareev, Dimitri [RAS, Chernogolovka (Russian Federation); Rienks, Emile [Helmholtz-Zentrum Berlin (Germany); Buechner, Bernd [IFW Dresden (Germany); TU Dresden (Germany); Shermadini, Zurab; Luetkens, Hubertus; Sedlak, Kamil; Khasanov, Rustem; Amato, Alex; Krzton-Maziopa, Anna; Conder, Kazimierz; Pomjakushina, Ekaterina [Paul Scherrer Institute (Switzerland); Klauss, Hans-Henning [TU Dresden (Germany)

    2014-07-01

    The electronic structure of the iron chalcogenide superconductors FeSe{sub 1-x} and Rb{sub 0.77}Fe{sub 1.61}Se{sub 2} was investigated by high-resolution angle-resolved photoemission spectroscopy (ARPES). The results were compared to DFT calculations and μSR measurements. Both compounds share ''cigar-shaped'' Fermi surface sheets in their electronic structure, that can be found in almost all iron-pnictide superconductors. These features originate from a strong interplay of two hole- and electron-like bands in the Brillouin zone center, leading to a pronounced singularity in the density of states just below the Fermi level. This facilitates the coupling to a bosonic mode responsible for superconductivity.

  13. Photoemission characteristics of thin GaAs-based heterojunction photocathodes

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Cheng; Zhang, Yijun, E-mail: zhangyijun423@126.com; Qian, Yunsheng [Institute of Electronic Engineering and Optoelectronic Technology, Nanjing University of Science and Technology, Nanjing 210094 (China); Shi, Feng [Science and Technology on Low-Light-Level Night Vision Laboratory, Xi' an 710065 (China); Zou, Jijun [Engineering Research Center of Nuclear Technology Application (East China Institute of Technology), Ministry of Education, Nanchang 330013 (China); Zeng, Yugang [Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China)

    2015-01-14

    To better understand the different photoemission mechanism of thin heterojunction photocathodes, the quantum efficiency models of reflection-mode and transmission-mode GaAs-based heterojunction photocathodes are revised based on one-dimensional continuity equations, wherein photoelectrons generated from both the emission layer and buffer layer are taken into account. By comparison of simulated results between the revised and conventional models, it is found that the electron contribution from the buffer layer to shortwave quantum efficiency is closely related to some factors, such as the thicknesses of emission layer and buffer layer and the interface recombination velocity. Besides, the experimental quantum efficiency data of reflection-mode and transmission-mode AlGaAs/GaAs photocathodes are well fitted to the revised models, which confirm the applicability of the revised quantum efficiency models.

  14. Widespread spin polarization effects in photoemission from topological insulators

    Energy Technology Data Exchange (ETDEWEB)

    Jozwiak, C.; Chen, Y. L.; Fedorov, A. V.; Analytis, J. G.; Rotundu, C. R.; Schmid, A. K.; Denlinger, J. D.; Chuang, Y.-D.; Lee, D.-H.; Fisher, I. R.; Birgeneau, R. J.; Shen, Z.-X.; Hussain, Z.; Lanzara, A.

    2011-06-22

    High-resolution spin- and angle-resolved photoemission spectroscopy (spin-ARPES) was performed on the three-dimensional topological insulator Bi{sub 2}Se{sub 3} using a recently developed high-efficiency spectrometer. The topological surface state's helical spin structure is observed, in agreement with theoretical prediction. Spin textures of both chiralities, at energies above and below the Dirac point, are observed, and the spin structure is found to persist at room temperature. The measurements reveal additional unexpected spin polarization effects, which also originate from the spin-orbit interaction, but are well differentiated from topological physics by contrasting momentum and photon energy and polarization dependencies. These observations demonstrate significant deviations of photoelectron and quasiparticle spin polarizations. Our findings illustrate the inherent complexity of spin-resolved ARPES and demonstrate key considerations for interpreting experimental results.

  15. Energy band dispersion in photoemission spectra of argon clusters

    International Nuclear Information System (INIS)

    Foerstel, Marko; Mucke, Melanie; Arion, Tiberiu; Lischke, Toralf; Barth, Silko; Ulrich, Volker; Ohrwall, Gunnar; Bjoerneholm, Olle; Hergenhahn, Uwe; Bradshaw, Alex M.

    2011-01-01

    Using photoemission we have investigated free argon clusters from a supersonic nozzle expansion in the photon energy range from threshold up to 28 eV. Measurements were performed both at high resolution with a hemispherical electrostatic energy analyser and at lower resolution with a magnetic bottle device. The latter experiments were performed for various mean cluster sizes. In addition to the ∼1.5 eV broad 3p-derived valence band seen in previous work, there is a sharper feature at ∼15 eV binding energy. Surprisingly for non-oriented clusters, this peak shifts smoothly in binding energy over the narrow photon energy range 15.5-17.7 eV, indicating energy band dispersion. The onset of this bulk band-like behaviour could be determined from the cluster size dependence.

  16. The applications of microdosimetry in radiation biology study

    International Nuclear Information System (INIS)

    Kim, Eunhee

    2002-01-01

    To understand the mechanisms by which the ionizing radiation causes these damages, the spatial patterns of interaction and energy deposition by radiations should be explained in cellular level. All the descriptions of the physical process of radiation interaction and energy transfer in cellular or microscopic scale constitute the field of microdosimetry. The underlying motivations of microdosimetry study range from the efficient control of the radiation protection measures to the improvement of the diagnostic and therapeutic effectiveness in medical applications of radiation. The major quantity in the conventional radiation dosimetry or the macroscopic dosimetry is the 'absorbed dose' defined as the mean value of the possible energy depositions per unit mass of the target. With the microscopic targets such as cells and subcellular organelles, the average quantity can not represent the radiation actions on the targets any more because of the inhomogeneous and stochastic nature in radiation interaction with matter. The essence of microdosimetry is to study the fluctuation of energy deposition in a microscopic volume and its deviation from the mean value attributed to the inherent randomness of radiation interactions with matter

  17. The study of the radiation protection of propolis to the radiation effects in mice

    Energy Technology Data Exchange (ETDEWEB)

    Gu, Y.H.; Suzuki, Ikukatsu; Hasegawa, Takeo; Muto, H. [Suzuka Univ. of Medical Science, Mie (Japan); Yanagisawa, Takaharu; Iwasa, Toshihiro; Bamen, K.

    2000-05-01

    The profit which radiation brought to the Homo sapiens is very big. But, radiation has even harmful parameter for the human besides one case. After effect on man to the radiation is thought about, the individual of which sensibility is the highest is a fetus. Therefore, even an effects to this fetus is grasped precisely, and protection criterion and resource are decided from the viewpoint of the protection of radiation as well. If it does so, a child and maturitas aren't so difficult as in the protection of radiation and the managerial side. It was examined about control group, propolis administration chisels for medical use group, 1.5 Gy independent exposure group and propolis pluse 1.5 Gy group in this study. It was examined about the protection of radiation of propolis which to malformation, fetal death, arrested development, and so on in the organogenesis (8 days post conception) being done when sensibility is the highest against the teratogenesis. Preimplantation death rate was compared with the control group and the sham control group, and statistical significant difference wasn't recognized by a 1.5 Gy radiation independent exposure group, propolis administration 1.5 Gy radiation exposure group. As for the embryonic death rate, propolis was administered, and obviously embryonic death rate was poorer than the 1.5 Gy independent exposure group, and significant difference was recognized by a 1.5 Gy radiation exposure group (p<0.001). It has a 1.5 Gy radiation exposure group made clear by this research fetal death rate propolis administer more only 1.5 Gy exposure fetal death rate development low (p<0.001). Fetal death rate wasn't recognized by propolis administration group (Sham control). As for the teratogenesis rate, propolis was administered, and the teratogenesis rate of the 1.5 Gy radiation exposure group was higher than the 1.5 Gy radiation independent exposure group. But, this is thought anamorphosis appear by propolis administration so

  18. The study of the radiation protection of propolis to the radiation effects in mice

    International Nuclear Information System (INIS)

    Gu, Y.H.; Suzuki, Ikukatsu; Hasegawa, Takeo; Muto, H.; Yanagisawa, Takaharu; Iwasa, Toshihiro; Bamen, K.

    2000-01-01

    The profit which radiation brought to the Homo sapiens is very big. But, radiation has even harmful parameter for the human besides one case. After effect on man to the radiation is thought about, the individual of which sensibility is the highest is a fetus. Therefore, even an effects to this fetus is grasped precisely, and protection criterion and resource are decided from the viewpoint of the protection of radiation as well. If it does so, a child and maturitas aren't so difficult as in the protection of radiation and the managerial side. It was examined about control group, propolis administration chisels for medical use group, 1.5 Gy independent exposure group and propolis pluse 1.5 Gy group in this study. It was examined about the protection of radiation of propolis which to malformation, fetal death, arrested development, and so on in the organogenesis (8 days post conception) being done when sensibility is the highest against the teratogenesis. Preimplantation death rate was compared with the control group and the sham control group, and statistical significant difference wasn't recognized by a 1.5 Gy radiation independent exposure group, propolis administration 1.5 Gy radiation exposure group. As for the embryonic death rate, propolis was administered, and obviously embryonic death rate was poorer than the 1.5 Gy independent exposure group, and significant difference was recognized by a 1.5 Gy radiation exposure group (p<0.001). It has a 1.5 Gy radiation exposure group made clear by this research fetal death rate propolis administer more only 1.5 Gy exposure fetal death rate development low (p<0.001). Fetal death rate wasn't recognized by propolis administration group (Sham control). As for the teratogenesis rate, propolis was administered, and the teratogenesis rate of the 1.5 Gy radiation exposure group was higher than the 1.5 Gy radiation independent exposure group. But, this is thought anamorphosis appear by propolis administration so long as there was

  19. Electronic structure investigation of atomic layer deposition ruthenium(oxide) thin films using photoemission spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Schaefer, Michael, E-mail: mvschaefer@mail.usf.edu, E-mail: schlaf@mail.usf.edu [Department of Physics, University of South Florida, Tampa, Florida 33620 (United States); Schlaf, Rudy, E-mail: mvschaefer@mail.usf.edu, E-mail: schlaf@mail.usf.edu [Department of Electrical Engineering, University of South Florida, Tampa, Florida 33620 (United States)

    2015-08-14

    Analyzing and manipulating the electronic band line-up of interfaces in novel micro- and nanoelectronic devices is important to achieve further advancement in this field. Such band alignment modifications can be achieved by introducing thin conformal interfacial dipole layers. Atomic layer deposition (ALD), enabling angstrom-precise control over thin film thickness, is an ideal technique for this challenge. Ruthenium (Ru{sup 0}) and its oxide (RuO{sub 2}) have gained interest in the past decade as interfacial dipole layers because of their favorable properties like metal-equivalent work functions, conductivity, etc. In this study, initial results of the electronic structure investigation of ALD Ru{sup 0} and RuO{sub 2} films via photoemission spectroscopy are presented. These experiments give insight into the band alignment, growth behavior, surface structure termination, and dipole formation. The experiments were performed in an integrated vacuum system attached to a home-built, stop-flow type ALD reactor without exposing the samples to the ambient in between deposition and analysis. Bis(ethylcyclopentadienyl)ruthenium(II) was used as precursor and oxygen as reactant. The analysis chamber was outfitted with X-ray photoemission spectroscopy (LIXPS, XPS). The determined growth modes are consistent with a strong growth inhibition situation with a maximum average growth rate of 0.21 Å/cycle for RuO{sub 2} and 0.04 Å/cycle for Ru.{sup 0} An interface dipole of up to −0.93 eV was observed, supporting the assumption of a strongly physisorbed interface. A separate experiment where the surface of a RuO film was sputtered suggests that the surface is terminated by an intermediate, stable, non-stoichiometric RuO{sub 2}/OH compound whose surface is saturated with hydroxyl groups.

  20. Electronic structure investigation of atomic layer deposition ruthenium(oxide) thin films using photoemission spectroscopy

    Science.gov (United States)

    Schaefer, Michael; Schlaf, Rudy

    2015-08-01

    Analyzing and manipulating the electronic band line-up of interfaces in novel micro- and nanoelectronic devices is important to achieve further advancement in this field. Such band alignment modifications can be achieved by introducing thin conformal interfacial dipole layers. Atomic layer deposition (ALD), enabling angstrom-precise control over thin film thickness, is an ideal technique for this challenge. Ruthenium (Ru0) and its oxide (RuO2) have gained interest in the past decade as interfacial dipole layers because of their favorable properties like metal-equivalent work functions, conductivity, etc. In this study, initial results of the electronic structure investigation of ALD Ru0 and RuO2 films via photoemission spectroscopy are presented. These experiments give insight into the band alignment, growth behavior, surface structure termination, and dipole formation. The experiments were performed in an integrated vacuum system attached to a home-built, stop-flow type ALD reactor without exposing the samples to the ambient in between deposition and analysis. Bis(ethylcyclopentadienyl)ruthenium(II) was used as precursor and oxygen as reactant. The analysis chamber was outfitted with X-ray photoemission spectroscopy (LIXPS, XPS). The determined growth modes are consistent with a strong growth inhibition situation with a maximum average growth rate of 0.21 Å/cycle for RuO2 and 0.04 Å/cycle for Ru.0 An interface dipole of up to -0.93 eV was observed, supporting the assumption of a strongly physisorbed interface. A separate experiment where the surface of a RuO film was sputtered suggests that the surface is terminated by an intermediate, stable, non-stoichiometric RuO2/OH compound whose surface is saturated with hydroxyl groups.

  1. Electronic structure investigation of atomic layer deposition ruthenium(oxide) thin films using photoemission spectroscopy

    International Nuclear Information System (INIS)

    Schaefer, Michael; Schlaf, Rudy

    2015-01-01

    Analyzing and manipulating the electronic band line-up of interfaces in novel micro- and nanoelectronic devices is important to achieve further advancement in this field. Such band alignment modifications can be achieved by introducing thin conformal interfacial dipole layers. Atomic layer deposition (ALD), enabling angstrom-precise control over thin film thickness, is an ideal technique for this challenge. Ruthenium (Ru 0 ) and its oxide (RuO 2 ) have gained interest in the past decade as interfacial dipole layers because of their favorable properties like metal-equivalent work functions, conductivity, etc. In this study, initial results of the electronic structure investigation of ALD Ru 0 and RuO 2 films via photoemission spectroscopy are presented. These experiments give insight into the band alignment, growth behavior, surface structure termination, and dipole formation. The experiments were performed in an integrated vacuum system attached to a home-built, stop-flow type ALD reactor without exposing the samples to the ambient in between deposition and analysis. Bis(ethylcyclopentadienyl)ruthenium(II) was used as precursor and oxygen as reactant. The analysis chamber was outfitted with X-ray photoemission spectroscopy (LIXPS, XPS). The determined growth modes are consistent with a strong growth inhibition situation with a maximum average growth rate of 0.21 Å/cycle for RuO 2 and 0.04 Å/cycle for Ru. 0 An interface dipole of up to −0.93 eV was observed, supporting the assumption of a strongly physisorbed interface. A separate experiment where the surface of a RuO film was sputtered suggests that the surface is terminated by an intermediate, stable, non-stoichiometric RuO 2 /OH compound whose surface is saturated with hydroxyl groups

  2. Studies on chemical protectors against radiation, 31

    International Nuclear Information System (INIS)

    Sato, Yushi; Ohta, Setsuko; Shinoda, Masato

    1990-01-01

    Protective effects of Aloe arborescens (AA) on mouse skin injury induced by soft X-irradiation were examined. The mechanisms on radiation protection by measuring scavenge activity of activated oxygen, protective effects of nucleic acid, induction of antioxidative protein and so on were further investigated. Consequently a significant protective effect of skin injury was observed in AA S6-3-b. As the mechanisms of radiation protection in AA, the following matters were found. AA S6-3-b showed scavenge activity of hydroxyl radicals generated by Haber-Weiss reaction. AA S6-3-b suppressed the changes of activity in superoxide dismutase and gluthathione peroxidase at 7d after soft X-irradiation. Metallothionein was induced in the skin and liver against normal mice at 24 h after administration of AA S6-3-b. (author)

  3. Gamma radiation in ceramic capacitors: a study for space missions

    Science.gov (United States)

    dos Santos Ferreira, Eduardo; Sarango Souza, Juliana

    2017-10-01

    We studied the real time effects of the gamma radiation in ceramic capacitors, in order to evaluate the effects of cosmic radiation on these devices. Space missions have electronic circuits with various types of devices, many studies have been done on semiconductor devices exposed to gamma radiation, but almost no studies for passive components, in particular ceramic capacitors. Commercially sold ceramic capacitors were exposed to gamma radiation, and the capacitance was measured before and after exposure. The results clearly show that the capacitance decreases with exposure to gamma radiation. We confirmed this observation in a real time capacitance measurement, obtained using a data logging system developed by us using the open source Arduino platform.

  4. Study of effects of radiation on silicone prostheses

    International Nuclear Information System (INIS)

    Shedbalkar, A.R.; Devata, A.; Padanilam, T.

    1980-01-01

    Radiation effects on silicone gel and dose distribution of radiation through mammary prostheses were studied. Silicone gel behaves like tissue. Half value thickness for silicone gel and water are almost the same. Linear absorption coefficient for silicone gel and water are comparable

  5. Study of genomic instability induced by low dose ionizing radiation

    International Nuclear Information System (INIS)

    Seoane, A.; Crudeli, C.; Dulout, F.

    2006-01-01

    The crews of commercial flights and services staff of radiology and radiotherapy from hospitals are exposed to low doses of ionizing radiation. Genomic instability includes those adverse effects observed in cells, several generations after the exposure occurred. The purpose of this study was to analyze the occurrence of genomic instability by very low doses of ionizing radiation [es

  6. Studies on chemical protectors against radiation, 18

    International Nuclear Information System (INIS)

    Shinoda, Masato; Ohta, Setsuko; Hayase, Yukitoshi

    1978-01-01

    Radiation protective effect of S,2-aminomethylisothiuronium bromide hydrobromide and 2-mercaptoethylamine hydrochloride was tested on mice irradiated with soft x-ray of 70 kVp, using life-prolongation effect as an index. These compounds showed a marked effect on mice irradiated with 11000--13000 R, using a 10 mm acrylate filter. This method seemed to be usable as a potency testing for chemical radioprotectors. (auth.)

  7. Epidemiological studies on radiation carcinogenesis in human populations following acute exposure: nuclear explosions and medical radiation

    International Nuclear Information System (INIS)

    Fabrikant, J.I.

    1981-01-01

    The present review provides an understanding of our current knowledge of the carcinogenic effect of low-dose radiation in man, and surveys the epidemiological studies of human populations exposed to nuclear explosions and medical radiation. Discussion centers on the contributions of quantitative epidemiology to present knowledge, the reliability of the dose-incidence data, and those relevant epidemiological studies that provide the most useful information for risk estimation of cancer induction in man. Reference is made to dose-incidence relationships from laboratory animal experiments where they may obtain, for problems and difficulties in extrapolation from data obtained at high doses to low doses, and from animal data to the human situation. The paper describes the methods of application of such epidemiological data for estimation of excess risk of radiation-induced cancer in exposed human populations and discusses the strengths and limitations of epidemiology in guiding radiation protection philosophy and public health policy

  8. Theory of photoemission and inverse-photoemission spectra of highly correlated electron systems: A weak-coupling 1/N expansion

    International Nuclear Information System (INIS)

    Riseborough, P.S.

    1989-01-01

    An N-fold-degenerate Hubbard model is examined in the weak-coupling regime. The one-electron Green's function is calculated from a systematic expansion of the irreducible self-energy in powers of 1/N. To lowest order in the expansion, one obtains a trivial mean-field theory. In the next leading order in 1/N, one finds that the dynamics are dominated by bosonlike collective excitations. The resulting expansion has the characteristics of the standard weak-coupling field theory, except the inclusion of the 1/N factors extends the regime of applicability to include Stoner-like enhancement factors which can be N times larger. The joint valence-band photoemission and inverse-photoemission spectrum is given by the trace of the imaginary part of the one-electron Green's function. The electronic spectrum has been calculated by truncating the series expansion for the self-energy in the lowest nontrivial order of 1/N. For small values of the Coulomb interaction between the electrons, the spectrum reduces to the form obtained by calculating the self-energy to second order in the Coulomb interaction. The spectra shows a narrowing of the band in the vicinity of the Fermi level and long high-energy band tails. When the boson spectrum softens, indicating the vicinity of a phase transition, the electronic spectrum shows the appearance of satellites. The results are compared with experimental observations of anomalies in the electronic spectra of uranium-based systems. The relation between the electronic spectrum and the thermodynamic mass enhancements is also discussed

  9. Study of the initial processes of radiation effects using synchrotron radiation

    International Nuclear Information System (INIS)

    Kobayashi, Katsumi

    1990-01-01

    Necessity for the research of production mechanisms of molecular damages in biological system and usefulness of monochromatic soft X-ray in these studies are described. Synchrotron radiation are introduced as a strong light source with continuous spectrum. Practically, it is the only light source in soft X-ray and vacuum UV region. Development of irradiation apparatus for radiation biology and recent results using various biological systems are reviewed. (author)

  10. Photoionization studies of atoms and molecules using synchrotron radiation

    International Nuclear Information System (INIS)

    Lindle, D.W.

    1988-01-01

    Photoionization studies of free atoms and molecules have undergone considerable development in the past decade, in large part due to the use of synchrotron radiation. The tunability of synchrotron radiation has permitted the study of photoionization processes near valence-and core-level ionization thresholds for atoms and molecules throught the Periodic Table. A general illustration of these types of study will be presented, with emphasis on a few of the more promising new directions in atomic and molecular physics being pursued with synchrotron radiation. (author) [pt

  11. ANL/WSU radiation damage studies

    International Nuclear Information System (INIS)

    Jankowski, D.; Lopiano, D.; Proudfoot, J.; Underwood, D.; Miles, L.; Neidiger, J.; Tripard, G.

    1993-01-01

    We report preliminary results for the radiation hardness of (polystryrene) plastic scintillator stacks using a spectrum of energy hardened neutrons from a MARK-III TRIGA reactor. The total dose ranged from 100 KRad to 3MRad. The corresponding fluence was 3.8 x 10 13 to 3.8 x 10 14 (n/cm/cm) with the gamma contribution on the order 2--3% (of fluence). The measurements used Li-6, Li-7 Thermo-luminescence dosimeters. Radiochromic/GaF- Chromic film, and activated foils simultaneously allowing an inter-comparison of these various methods of dosimetry

  12. Study of radiation effects on semiconductor devices

    International Nuclear Information System (INIS)

    Kuboyama, Satoshi; Shindou, Hiroyuki; Ikeda, Naomi; Iwata, Yoshiyuki; Murakami, Takeshi

    2004-01-01

    Fine structure of the recent semiconductor devices has made them more sensitive to the space radiation environment with trapped high-energy protons and heavy ions. A new failure mode caused by bulk damage had been reported on such devices with small structure, and its effect on commercial synchronous dynamic random access memory (SDRAMs) was analyzed from the irradiation test results performed at Heavy ion Medical Accelerator in Chiba (HIMAC). Single event upset (SEU) data of static random access memory (SRAMs) were also collected to establish the method of estimating the proton-induced SEU rate from the results of heavy ion irradiation tests. (authors)

  13. Nuclear and radiation studies and environmental concerns

    International Nuclear Information System (INIS)

    McEwan, A.C.

    1998-01-01

    Over the three days 22-24 September 1998 a Science Forum was convened under the general heading of 'Nuclear technology in relation to water resources and the aquatic environment' at the International Atomic Energy Agency, Vienna. Some points of interest, or points of more particular relevance to radiation protection, are noted from the five sessions of the Forum: Session 1: water resources; Session 2: sea transport of radioactive and nuclear materials; Session 3: monitoring radioactivity in the aquatic environment; Session 4: nuclear technology in relation to waste resources and the aquatic environment, Session 5: impact assessment. (author)

  14. Theory of tunneling and photoemission spectroscopy for high-temperature superconductors

    International Nuclear Information System (INIS)

    Kouznetsov, K.; Coffey, L.

    1996-01-01

    A comprehensive analysis is presented of the tunneling conductance and angle-resolved photoemission spectra in high-temperature superconductors. It is shown that unexplained features of the tunneling and photoemission spectra such as broad backgrounds, dips, and asymmetry of the tunneling conductance can arise in a model of spin-fluctuation mediated inelastic tunneling. Effects of directionality in tunneling play an important role in determining the behavior of the tunneling conductance. copyright 1996 The American Physical Society

  15. Many-body effects in X-ray photoemission spectroscopy and electronic properties of solids

    International Nuclear Information System (INIS)

    Kohiki, S.

    1999-01-01

    Photoemission from a solid is evidently a many-body process since the motion of each electron cannot be independent of the motions of other electrons. In this article we review the reported many-body effects in X-ray photoemission such as extra-atomic relaxation energy, charge transfer satellite and energy loss structure which are informative in relation to the characteristics of solids. (Copyright (c) 1999 Elsevier Science B.V., Amsterdam. All rights reserved.)

  16. View of environmental radiation effects from the study of radiation biology in C. elegans

    International Nuclear Information System (INIS)

    Sakashita, Tetsuya

    2011-01-01

    Caenorhabditis (C.) elegans is a non-parasitic soil nematode and is well-known as a unique model organism, because of its complete cell-lineage, nervous network and genome sequences. Also, C. elegans can be easily manipulated in the laboratory. These advantages make C. elegans as a good in vivo model system in the field of radiation biology. Radiation effects in C. elegans have been studied for three decades. Here, I briefly review the current knowledge of the biological effects of ionizing irradiation in C. elegans with a scope of environmental radiation effects. Firstly, basic information of C. elegans as a model organism is described. Secondly, historical view is reported on the study of radiation biology in C. elegans. Thirdly, our research on learning behavior is presented. Finally, an opinion of the use of C. elegans for environmental radiation protection is referred. I believe that C. elegans may be a good promising in vivo model system in the field of environmental radiation biology. (author)

  17. Study on technology for minimizing radiation risk

    International Nuclear Information System (INIS)

    Lee, Jeong Ho; Kim, In Gyu; Kim, Jin Kyu; Lee, Kang Suk; Kim, Kug Chan; Chun, Ki Chung.

    1997-01-01

    Apoptosis, also called programmed cell death to discriminate it from necrosis, is characterized by : chromatin condensation, apoptotic body formation, fragmentation of DNA into oligonucleosome sized pieces, swelling and progressive cell degradation. We examined morphological and biochemical changes of T-lymphocytes following gamma irradiation exposure. The results are followings. 1) Murine lymphocytes have several characteristics : The irradiated cells undergo morphological and biochemical changes characteristic of apoptosis, causing growth delay. (0.01, 0.1, 1.0 Gy) 2) The onset of DNA fragmentation in cells occurs after one more cell divisions. 3) DNA fragmentation in cells occurs in all irradiated group (0.1, 1.0, 2.0, 4.0 Gy, 24 hours following gamma radiation exposure) 4) Apoptotic bodies were detected by confocal microscope with ease when compared with electron microscope. For the developing technology for minimizing radiation damage, the following experimental works have been done. 1) Establishment of experimental system for pre-screening of radioprotectants - Screening of protective substances using TSH bioindicator - Efficacy test of some radioprotective materials 2) TSH bioindicator system can make a scientific role in screening unknown materials for their possible radioprotective effect. (author). 42 refs., 3 tabs., 9 figs

  18. Study on technology for minimizing radiation risk

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jeong Ho; Kim, In Gyu; Kim, Jin Kyu; Lee, Kang Suk; Kim, Kug Chan; Chun, Ki Chung

    1997-01-01

    Apoptosis, also called programmed cell death to discriminate it from necrosis, is characterized by : chromatin condensation, apoptotic body formation, fragmentation of DNA into oligonucleosome sized pieces, swelling and progressive cell degradation. We examined morphological and biochemical changes of T-lymphocytes following gamma irradiation exposure. The results are followings. (1) Murine lymphocytes have several characteristics : The irradiated cells undergo morphological and biochemical changes characteristic of apoptosis, causing growth delay. (0.01, 0.1, 1.0 Gy) (2) The onset of DNA fragmentation in cells occurs after one more cell divisions. (3) DNA fragmentation in cells occurs in all irradiated group (0.1, 1.0, 2.0, 4.0 Gy, 24 hours following gamma radiation exposure) (4) Apoptotic bodies were detected by confocal microscope with ease when compared with electron microscope. For the developing technology for minimizing radiation damage, the following experimental works have been done. (1) Establishment of experimental system for pre-screening of radioprotectants - Screening of protective substances using TSH bioindicator - Efficacy test of some radioprotective materials (2) TSH bioindicator system can make a scientific role in screening unknown materials for their possible radioprotective effect. (author). 42 refs., 3 tabs., 9 figs.

  19. [The study of transpiration influence on plant infrared radiation character].

    Science.gov (United States)

    Ling, Jun; Zhang, Shuan-Qin; Pan, Jia-Liang; Lian, Chang-Chun; Yang, Hui

    2012-07-01

    Studying vegetation infrared radiation character is the base of developing infrared camouflage and concealment technology of ground military target. Accurate fusion of target and background can be achieved by simulating formation mechanism of vegetation infrared radiation character. Leaf transpiration is characteristic physiological mechanism of vegetation and one of the main factors that influence its infrared radiation character. In the present paper, physical model of leaf energy balance is set up. Based on this model the influence of plant transpiration on leaf temperature is analyzed and calculated. The daily periodic variation of transpiration, leaf temperature and infrared radiation character of typical plants such as camphor tree and holly is actually measured with porometer and infrared thermal imaging system. By contrasting plant leaf with dryness leaf, experimental data indicates that plant transpiration can regulate leaf energy balance effectively and control leaf temperature in a reasonable range and suppress deep range variation of leaf infrared radiation character.

  20. Bulk electronic structures of n-type superconductor Nd1.85Ce0.15CuO4 probed by high energy angle-resolved photoemission spectroscopy

    International Nuclear Information System (INIS)

    Tsunekawa, M.; Sekiyama, A.; Kasai, S.; Yamasaki, A.; Fujiwara, H.; Sing, M.; Shigemoto, A.; Imada, S.; Onose, Y.; Tokura, Y.; Muro, T.; Suga, S.

    2005-01-01

    We report on a high-energy angle-resolved photoemission (ARPES) study of the n-type high-T C cuprate, Nd 1.85 Ce 0.15 CuO 4 (NCCO). Our bulk sensitive results suggest a hole-like Fermi surface as seen by the so far reported low-energy ARPES studies. The soft X-ray Cu 2p core-level photoemission spectra show clear polar-angle dependence, suggesting the difference in electron states between the bulk and surface

  1. Mechanisms of interaction of radiation with matter

    International Nuclear Information System (INIS)

    Geacintov, N.E.; Pope, M.

    1991-01-01

    The combustion of fossil fuels gives rise to airborne particulates containing deposits of mutagenic and carcinogenic polynuclear aromatic (PNA) compounds. Part 1, results of detailed studies on the mechanisms of photoionization and photoemission of electrons from solid pyrene and nitropyrene derivatives, are described. A new time-resolved picosecond double-pulse laser technique is described for studying the mechanisms of photoemission in organic solids. Reactions of PNA radical cations at organic solid/aqueous electrolyte interfaces, are described in Part 2. The mechanisms of reactions of mutagenic metabolites of benzo[a]pyrene with nucleic acids is discussed in Part 3; it is shown that photoinduced electron transfer occurs from the nucleic acids to the PNA moieties giving rise to short-lived exciplexes with significant charge-transfer character. A new project on the effects of ionizing radiation (electrons, neutrons and gammas) on deoxyoligonucleotides of defined base sequence using high resolution gel electrophoresis is described in Part 4 of this report. 102 refs., 35 figs., 5 tabs

  2. Study of electromagnetic radiation pollution in Jalandhar city, India

    Science.gov (United States)

    Basandrai, D.; Dhami, A. K.; Bedi, R. K.; Khan, S. A.

    2017-07-01

    Environment pollution from electromagnetic radiations emitted from cell phone towers is a new kind of health hazard, which has increase the public concern regarding the health implications of electromagnetic radiations on humans and animals. Long term consequences of these radiations are still unknown. So it become important to measure and maps the electromagnetic radiation level to analyze potential risk. The present study has been taken to estimate the RF pollution by measuring radiation power densities level near school, hospitals and old age home of Jalandhar City, India. The radiation exposure was measured using a handheld portable electrosmog meter. Results were compared with the safety guidelines issued by ICNIRP (International commission on non ionizing radiation protection) and Bio-initiative report, 2012. It has been found that the radiation exposure level in terms of power densities and corresponding specific absorption rate (SAR) are much below than ICNIRP guidelines for all schools, hospitals and old age home. But in the case of 3 schools, the results are quite alarming where the power density and SAR was found to be 79.6% and 4%, respectively higher in comparisons with safe biological limit.

  3. A basic study of intraoperative radiation on the stomach

    International Nuclear Information System (INIS)

    Aoki, Tetsuya

    1978-01-01

    In a basic study of intraoperative radiation on the stomach, adult dogs were laparotomized, and radiated on the stomach and gastroduodenal anastomosed part with an electron beam to 1,000 - 4,000 rads to observed its effects on hematologic and histologic findings. 1) No leukopenia occurred with the radiation, but secondary effects such as anemia and hypoproteinemia were noted. 2) On the gastric wall, the mucosa was most severely effected by the radiation, presenting such changes as erosion, atrophy, disappearance of glandular tissue, and fibrosis with the lapse of time. 3) The radiation on the stomach to 3,000 rads was followed by ulceration in one month, by the start of repair of the ulceration in three months, and by its healing in eight months. Histologic examination disclosed no evident damages to the blood vessels by the radiation. 4) Delayed healing of the anastomosed part was noted as an effect of the radiation on this part. 5) The findings in this experiment appear to suggest that the single tolerable dose of electron beam radiation on the stomach and the gastroduodenal anastomosed part should be 3,000 rads. (author)

  4. Difference in Understanding of the Need for Using Radiation in Various Fields between Students Majoring in Radiation and Non-Radiation Related Studies

    Energy Technology Data Exchange (ETDEWEB)

    Han, Eun Ok [Dept. of Radiological Tecknology, Daegu Health College, Daegu (Korea, Republic of)

    2011-12-15

    As a way of improving social receptivity of using radiation, this study looked into the difference of understanding the need of using radiation in various fields between students majoring in radiation and non-radiation related studies, who will influence public opinion in the long term. This study also provides data needed for developing efficient strategies for projects promoting the public's awareness of using radiation. Of the students in the 79 schools sampled, 24%(177) were in 4 year colleges and 146 were junior colleges in educational statistics service (http://cesi.kedi.re.kr) In November 2010 1,945 students were selected as a sample, and they were given surveys on the need of using radiation in different fields. As a result, both between students majoring in radiation and non-radiation related studies showed a high level of understanding the need for radiation in the medical field and showed a low level of understanding of the need for radiation in the agricultural field. In all 6 fields of radiation use, students majoring in radiation related studies showed higher levels of understanding for the need to use radiation than students majoring in radiation and non-radiation related studies. In each field, male students and those who have experience medical radiation and relevant education had higher level of understanding. This shows we need to improve the understanding of the cases of female students and those who have not had experiences with medical radiation and to provide relevant education through various kinds of information. The characteristics of the groups that are shown in the results of this study are considered to be helpful for efficiently for project promoting the public's awareness of using radiation.

  5. Difference in Understanding of the Need for Using Radiation in Various Fields between Students Majoring in Radiation and Non-Radiation Related Studies

    International Nuclear Information System (INIS)

    Han, Eun Ok

    2011-01-01

    As a way of improving social receptivity of using radiation, this study looked into the difference of understanding the need of using radiation in various fields between students majoring in radiation and non-radiation related studies, who will influence public opinion in the long term. This study also provides data needed for developing efficient strategies for projects promoting the public's awareness of using radiation. Of the students in the 79 schools sampled, 24%(177) were in 4 year colleges and 146 were junior colleges in educational statistics service (http://cesi.kedi.re.kr) In November 2010 1,945 students were selected as a sample, and they were given surveys on the need of using radiation in different fields. As a result, both between students majoring in radiation and non-radiation related studies showed a high level of understanding the need for radiation in the medical field and showed a low level of understanding of the need for radiation in the agricultural field. In all 6 fields of radiation use, students majoring in radiation related studies showed higher levels of understanding for the need to use radiation than students majoring in radiation and non-radiation related studies. In each field, male students and those who have experience medical radiation and relevant education had higher level of understanding. This shows we need to improve the understanding of the cases of female students and those who have not had experiences with medical radiation and to provide relevant education through various kinds of information. The characteristics of the groups that are shown in the results of this study are considered to be helpful for efficiently for project promoting the public's awareness of using radiation.

  6. Techno-economic benefits of radiation curing: a comparison studies

    Energy Technology Data Exchange (ETDEWEB)

    French, D [Universal Wood Inc., Lousville (United States)

    1994-12-31

    In comparing radiation cure versus conventional heat cure systems, the factors are considered in this studies i.e. environmental laws - includes the future regulations concerning volatile organic emissions and waste disposal may weigh heavily in the decision.

  7. Positron annihilation and perturbed angular correlation studies of radiation damage

    International Nuclear Information System (INIS)

    Zhu Jiazheng; Li Anli; Xu Yongjun; Wang Zhiqiang; Zhou Dongmei; Zheng Yongnan; Zhu Shengyun; Iwata, T.

    2002-01-01

    The positron annihilation and perturbed angular correlation techniques have been employed to study radiation damage in Si and Nb. The results obtained by the positron annihilation are consistent with those given by the perturbed angular correlation

  8. Epidemiological studies of some populations exposed to ionizing radiation

    International Nuclear Information System (INIS)

    Weeks, J.L.

    1985-08-01

    During 1984 September 19 and 20, a meeting was held at the Whiteshell Nuclear Research Establishment, Pinawa, Manitoba to discuss current epidemiological studies of populations exposed to low levels of ionizing radiation. Twelve representatives from three countries attended the meeting and eleven papers were extensively discussed. The majority of these papers described studies of populations occupationally exposed to radiation. The report contains summaries of the papers presented and of the discussions that took place

  9. Studies on five cases of radiation enterocolitis

    Energy Technology Data Exchange (ETDEWEB)

    Yasunaga, Akira; Shibata, Okihiko; Kubo, Hironobu; Tomonari, Kazuhide; Hadama, Tetsuo; Uchida, Yuzou; Shirabe, Joji (Oita Medical Coll. (Japan))

    1990-05-01

    Five patients with radiation enterocolitis who were surgically treated are reported. The 5 patients had received irradiation therapy more than 5,000 rad for ginecologic malignancies. The period for the onset of symptoms of irradiation enteritis ranged from 8 months to 20 years however, 3 of them developed the symptoms within one year after irradiation therapy. Emergency surgery was carried out for bowel obstruction in 3 cases and for intestinal perforation in 2 cases. Bowel resection and primary anastomosis were performed by a one-step approach in 4 of them. Transient colostomy as preventive measure was added in 2 cases. It is very important for the one-step approach to resect the intestine at the healthy part far from the lesion of irradiation enteritis and to add a transient colostomy to prevent anastomolic insufficiency. Furthermore, suture material should be used less tissue reactive one. (author).

  10. Studies on five cases of radiation enterocolitis

    International Nuclear Information System (INIS)

    Yasunaga, Akira; Shibata, Okihiko; Kubo, Hironobu; Tomonari, Kazuhide; Hadama, Tetsuo; Uchida, Yuzou; Shirabe, Joji

    1990-01-01

    Five patients with radiation enterocolitis who were surgically treated are reported. The 5 patients had received irradiation therapy more than 5,000 rad for ginecologic malignancies. The period for the onset of symptoms of irradiation enteritis ranged from 8 months to 20 years however, 3 of them developed the symptoms within one year after irradiation therapy. Emergency surgery was carried out for bowel obstruction in 3 cases and for intestinal perforation in 2 cases. Bowel resection and primary anastomosis were performed by a one-step approach in 4 of them. Transient colostomy as preventive measure was added in 2 cases. It is very important for the one-step approach to resect the intestine at the healthy part far from the lesion of irradiation enteritis and to add a transient colostomy to prevent anastomolic insufficiency. Furthermore, suture material should be used less tissue reactive one. (author)

  11. A study on the radiation and environmental safety -Development of radiation protection and measurement technology-

    Energy Technology Data Exchange (ETDEWEB)

    Jang, See Yung; Lee, Tae Yung; Lee, Hyung Sub; Kim, Jan Ryul; Kim, Chang Kyung; Kim, Bong Hwan; Yoon, Kyung Soo; Jung, Kyung Kee; Jung, Duk Yun; Lee, Bong Jae; Chul, Yoon Suk; Lee, Kee Chang; Yoon, Yu Chang; Jung, Rae Ik; Lee, Sang Yoon; Han, Yung Dae; Kim, Jong Soo, I; Kim, Jong Soo, II; Suh, Kyung Won [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of); Kim, Jong Kyung [Han Yang Univ., Seoul (Korea, Republic of)

    1995-07-01

    Reference X- and neutron radiation fields have been established and evaluated to support the national radiation protection programme under which performance evaluation test for domestic personal dosimetry will be implemented by the ministerial ordinance 1992-15, and to provide a basic technical support in radiation protection dosimetry. Personal dose evaluation algorithm has been developed with the KAERI reference radiation fields which comply well with those in the new ANSI N13.11(1993) to evaluate accurate personal dose equivalents. A personal internal dosimetry algorithm which can estimate the intakes of radionuclides from the results of whole body direct bioassay and the resulting internal doses has been also developed and evaluated to be equally excellent compared with those being used in foreign countries. A BOMAB phantom for precise WBC calibration has also designed, fabricated and test-evaluated. A principal method for estimating the cost for radiation protection which is important in performing a cost-benefit analysis for the radiation protection optimization study based on the ALARA principle has been preliminarily investigated and suggested. 49 figs, 67 tabs, 50 refs. (Author).

  12. Acute radiation proctitis. A clinical, histopathological and histochemical study

    International Nuclear Information System (INIS)

    Hovdenak, Nils

    2004-01-01

    The aim of the study is: 1) A sequential description of the clinical course of acute radiation proctitis during pelvic RT. 2) A sequential description of the rectal mucosal histopathology during pelvic RT as a possible substrate for clinical toxicity. 3) To assess the mucosal protease activity during RT as a possible explanation of the observed tissue changes. 4) To assess the efficacy of prophylactic sucralfate in acute radiation proctitis a randomised study was initiated and carried out together with a meta-analysis of previously available data. 5) Most studies on clinical acute toxicity in pelvic RT use either the RTOG/EORTC score system or focus on diarrhoea/stool frequency. A more differentiated and sensitive recording was developed and tested to pick up symptoms escaping the commonly used scores. 6) Study the relation between histopathological findings and the clinical picture. 4 papers presenting various studies are included. The titles are: 1) Acute radiation proctitis: a sequential clinicopathologic study during pelvic radiotherapy. 2) Clinical significance of increased gelatinolytic activity in the rectal mucosa during external beam radiation therapy of prostate cancer. 3) Profiles and time course of acute radiation toxicity symptoms during conformal radiotherapy for cancer of the prostate. 4) Sucralfate does not ameliorate acute radiation proctitis. Some future prospects are discussed

  13. Acute radiation proctitis. A clinical, histopathological and histochemical study

    Energy Technology Data Exchange (ETDEWEB)

    Hovdenak, Nils

    2004-07-01

    The aim of the study is: 1) A sequential description of the clinical course of acute radiation proctitis during pelvic RT. 2) A sequential description of the rectal mucosal histopathology during pelvic RT as a possible substrate for clinical toxicity. 3) To assess the mucosal protease activity during RT as a possible explanation of the observed tissue changes. 4) To assess the efficacy of prophylactic sucralfate in acute radiation proctitis a randomised study was initiated and carried out together with a meta-analysis of previously available data. 5) Most studies on clinical acute toxicity in pelvic RT use either the RTOG/EORTC score system or focus on diarrhoea/stool frequency. A more differentiated and sensitive recording was developed and tested to pick up symptoms escaping the commonly used scores. 6) Study the relation between histopathological findings and the clinical picture. 4 papers presenting various studies are included. The titles are: 1) Acute radiation proctitis: a sequential clinicopathologic study during pelvic radiotherapy. 2) Clinical significance of increased gelatinolytic activity in the rectal mucosa during external beam radiation therapy of prostate cancer. 3) Profiles and time course of acute radiation toxicity symptoms during conformal radiotherapy for cancer of the prostate. 4) Sucralfate does not ameliorate acute radiation proctitis. Some future prospects are discussed.

  14. A Monte Carlo study of radiation trapping effects

    International Nuclear Information System (INIS)

    Wang, J.B.; Williams, J.F.; Carter, C.J.

    1997-01-01

    A Monte Carlo simulation of radiative transfer in an atomic beam is carried out to investigate the effects of radiation trapping on electron-atom collision experiments. The collisionally excited atom is represented by a simple electric dipole, for which the emission intensity distribution is well known. The spatial distribution, frequency and free path of this and the sequential dipoles were determined by a computer random generator according to the probabilities given by quantum theory. By altering the atomic number density at the target site, the pressure dependence of the observed atomic lifetime, the angular intensity distribution and polarisation of the radiation field is studied. 7 refs., 5 figs

  15. Monochromatization of synchrotron radiation for studies in photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Murty, P.S.

    1981-01-01

    Synchrotron radiation provides a tunable photon source which bridges the wavelength gap between HeI and AlKsub(α) radiation sources in photoelectron spectroscopy. The essential component for using synchrotron radiation is a monochromator. Some design features of the monochromators fabricated at Stanford, U.S.A., and Orsay, France, are described. The Stanford monochromator is a silicon crystal monochromator yielding 8 keV X-ray beam and is used with SPEAR storage ring facility, while the Orsay monochromator is a grazing incidence grating monochromator used for UPS studies. (M.G.B.)

  16. High-resolution, hard x-ray photoemission investigation of BaFe2As2: Moderate influence of the surface and evidence for a low degree of Fe 3d-As 4p hybridization of electronic states near the Fermi energy

    NARCIS (Netherlands)

    de Jong, S.; Huang, Y.; Huisman, R.; Massee, F.; Thirupathaiah, R.; Gorgoi, M.; Schaefers, F.; Follath, F.; Goedkoop, J.B.; Golden, M.S.

    2009-01-01

    Photoemission data taken with hard x-ray radiation on cleaved single crystals of the barium parent compound of the MFe2As2 pnictide high-temperature superconductor family are presented. Making use of the increased bulk sensitivity upon hard x-ray excitation, and comparing the results to data taken

  17. The first symposium of Research Center for Radiation Safety, NIRS. Perspective of future studies of radiation safety

    International Nuclear Information System (INIS)

    Shimo, Michikuni

    2002-03-01

    This paper summarizes presentations given in the title symposium, held at the Conference Room of National Institute of Radiological Sciences (NIRS) on November 29 and 30, 2001. Contained are Introductory remarks: Basic presentations concerning exposure dose in man; Environmental levels of radiation and radioactivity, environmental radon level and exposure dose, and radiation levels in the specific environment (like in the aircraft): Special lecture (biological effects given by space environment) concerning various needs for studies of radiation safety; Requirement for open investigations, from the view of utilization, research and development of atomic energy, from the clinical aspect, and from the epidemiological aspect: Special lecture (safety in utilization of atomic energy and radiation-Activities of Nuclear Safety Commission of Japan) concerning present state and perspective of studies of radiation safety; Safety of radiation and studies of biological effects of radiation-perspective, and radiation protection and radiation safety studies: Studies in the Research Center for Radiation Safety; Summary of studies in the center, studies of the biological effects of neutron beam, carcinogenesis by radiation and living environmental factors-complicated effects, and studies of hereditary effects: Panel discussion (future direction of studies of radiation safety for the purpose of the center's direction): and concluding remarks. (N.I.)

  18. Binomial vs poisson statistics in radiation studies

    International Nuclear Information System (INIS)

    Foster, J.; Kouris, K.; Spyrou, N.M.; Matthews, I.P.; Welsh National School of Medicine, Cardiff

    1983-01-01

    The processes of radioactive decay, decay and growth of radioactive species in a radioactive chain, prompt emission(s) from nuclear reactions, conventional activation and cyclic activation are discussed with respect to their underlying statistical density function. By considering the transformation(s) that each nucleus may undergo it is shown that all these processes are fundamentally binomial. Formally, when the number of experiments N is large and the probability of success p is close to zero, the binomial is closely approximated by the Poisson density function. In radiation and nuclear physics, N is always large: each experiment can be conceived of as the observation of the fate of each of the N nuclei initially present. Whether p, the probability that a given nucleus undergoes a prescribed transformation, is close to zero depends on the process and nuclide(s) concerned. Hence, although a binomial description is always valid, the Poisson approximation is not always adequate. Therefore further clarification is provided as to when the binomial distribution must be used in the statistical treatment of detected events. (orig.)

  19. Radiation Damage Studies of Silicon Photomultipliers

    CERN Document Server

    Bohn, P; Hazen, E.; Heering, A.; Rohlf, J.; Freeman, J.; Los, Sergey V.; Cascio, E.; Kuleshov, S.; Musienko, Y.; Piemonte, C.

    2008-01-01

    We report on the measurement of the radiation hardness of silicon photomultipliers (SiPMs) manufactured by Fondazione Bruno Kessler in Italy (1 mm$^2$ and 6.2 mm$^2$), Center of Perspective Technology and Apparatus in Russia (1 mm$^2$ and 4.4 mm$^2$), and Hamamatsu Corporation in Japan (1 mm$^2$). The SiPMs were irradiated using a beam of 212 MeV protons at Massachusetts General Hospital, receiving fluences of up to $3 \\times 10^{10}$ protons per cm$^2$ with the SiPMs at operating voltage. Leakage currents were read continuously during the irradiation. The delivery of the protons was paused periodically to record scope traces in response to calibrated light pulses to monitor the gains, photon detection efficiencies, and dark counts of the SiPMs. The leakage current and dark noise are found to increase with fluence. Te leakage current is found to be proportional to the mean square deviation of the noise distribution, indicating the dark counts are due to increased random individual pixel activation, while SiPM...

  20. Carbon nano tubes -Buckypaper- radiation studies for medical physics application

    Energy Technology Data Exchange (ETDEWEB)

    Alanazi, A.; Alkhorayef, M.; Dalton, A.; Bradley, D. A. [University of Surrey, Department of Physics, College for Nuclear and Radiation Physics, Guildford, Surrey GR2 7XH (United Kingdom); Alzimami, K. [King Saud University, Department of Radiological Sciences, P. O. Box 10219, Riyadh 11433 (Saudi Arabia); Abuhadi, N., E-mail: a.alanazi@surrey.ac.uk [Jazan University, Faculty of Medical Applied Sciences, Diagnostic Radiology Department, P. O. Box 114, Jazan (Saudi Arabia)

    2015-10-15

    Radiation dosimetry underpins safe and effective clinical applications of radiation. Many materials have been used to measure the radiation dose deposited in human tissue, their radiation response requiring the application of correction factors to account for various influencing factors, including sensitivity to dose and energy dependence. In regard to the latter, account needs to be taken of difference from the effective atomic number of human tissue, soft or calcified. Graphite ion chambers and semiconductor diode detectors have been used to make measurements in phantoms but these active devices represent a clear disadvantage when considered for in vivo dosimetry. In both circumstances, dosimeters with atomic number similar to human tissue are needed. Carbon nano tubes have properties that potentially meet the demand, requiring low voltage in active devices and an atomic number similar to adipose tissue. In this study, single-wall carbon nano tubes buckypaper has been used to measure the beta particle dose deposited from a strontium-90 source, the medium displaying thermoluminescence at potentially useful sensitivity. As an example, the samples show a clear response for a dose of 2 Gy. This finding suggests that carbon nano tubes can be used as a passive dosimeter specifically for the high levels of radiation exposures used in radiation therapy. Furthermore, the finding points towards further potential applications such as for space radiation measurements, not least because the medium satisfies a demand for light but strong materials of minimal capacitance. (Author)

  1. Carbon nano tubes -Buckypaper- radiation studies for medical physics application

    International Nuclear Information System (INIS)

    Alanazi, A.; Alkhorayef, M.; Dalton, A.; Bradley, D. A.; Alzimami, K.; Abuhadi, N.

    2015-10-01

    Radiation dosimetry underpins safe and effective clinical applications of radiation. Many materials have been used to measure the radiation dose deposited in human tissue, their radiation response requiring the application of correction factors to account for various influencing factors, including sensitivity to dose and energy dependence. In regard to the latter, account needs to be taken of difference from the effective atomic number of human tissue, soft or calcified. Graphite ion chambers and semiconductor diode detectors have been used to make measurements in phantoms but these active devices represent a clear disadvantage when considered for in vivo dosimetry. In both circumstances, dosimeters with atomic number similar to human tissue are needed. Carbon nano tubes have properties that potentially meet the demand, requiring low voltage in active devices and an atomic number similar to adipose tissue. In this study, single-wall carbon nano tubes buckypaper has been used to measure the beta particle dose deposited from a strontium-90 source, the medium displaying thermoluminescence at potentially useful sensitivity. As an example, the samples show a clear response for a dose of 2 Gy. This finding suggests that carbon nano tubes can be used as a passive dosimeter specifically for the high levels of radiation exposures used in radiation therapy. Furthermore, the finding points towards further potential applications such as for space radiation measurements, not least because the medium satisfies a demand for light but strong materials of minimal capacitance. (Author)

  2. Radiation physics in medicine and veterinary medicine studies

    International Nuclear Information System (INIS)

    Popovic, D.; Djuric, G.

    2000-01-01

    Medical and veterinary medicine staff and specialists represent an important decision making group in national administration and institutions dealing with radiation protection and environmental protection matters in general. Still, their education in physics, especially in radiation physics is fragmentary and loose, both from technical and theoretical point of view. Within medicine and veterinary medicine studies as well as within other biomedical sciences (biology, pharmacology, biotechnology) radiation physics is usually incorporated in the first year curricula as a part of general physics or biophysics course. Some segments of radiation physics mainly as a technical base for different instrumentation methods and techniques could be also found within different graduate and post-graduate courses of radiology, physical therapy, radiation hygiene, environmental protection, etc. But the traditional approach in presenting the matter and inflexibility of the educational system strongly confront the growing public concern for the environmental problems dealing with radiation and demands for better informing and technical education for those involved in informing and administration. This paper considers some of these problems presenting a new approach in education in radiation physics for medical and veterinary medicine students based on education through student projects and work in the field, as well as on the strong collaboration among administration, universities and professional societies on the national and international level. (author)

  3. The Study of External Radiation Dose for Radiation Worker at PRSG-BATAN Serpong

    International Nuclear Information System (INIS)

    Sunarningsih; Mashudi; A Lilik W; Yosep S

    2012-01-01

    The study of External radiation dose for radiation worker at PRSG-BATAN Serpong has been carried out. The sample is taken from the System Reactor division (BSR), Operation Reactor division, (BOR) Safety division UPN, UJM and head of PRSG by setting Thermoluminescence Dosemeter (TLD) on the chest, then is detected by a tool TLD reader model 6600. The aim of this study is to evaluate the occupational exposure dose that has been accepted by the radiation worker for the last five years. The result in average doses at BSR is 0,99 mSv, BOR is 3,27 mSv, at BK is 0,69 mSv and UPN + UJM + head of PRSG is 0,03 mSv. The result highest doses at BSR is 6,58 mSv, BOR is 28,94 mSv, BK is 4,24 mSv, and UPN UJM Head of PRSG is 0,52 mSv. Dose interval radiation worker at PRSG BATAN ttd - 28,98 mSv. To overall the external personal dose acceptant for radiation worker at PRSG BATAN one below maximum permissible dose acceptant that allowed by BAPETEN, that is 20 mSv in average every year during five years. (author)

  4. Development of radiation protection and measurement technology -A study on the radiation and environmental safety-

    International Nuclear Information System (INIS)

    Chang, Si Young; Seo, Kyeong Won; Yoon, Seok Cheol; Lee, Tae Yeong; Kim, Bong Hwan; Chung, Deok Yeon; Lee, Ki Chang; Kim, Jong Soo; Yoon, Yeo Chang; Kim, Jang Ryeol; Lee, Sang Yoon

    1994-07-01

    Reference radiation fields which can meet the national and international standard and criteria such as the ANSI N13.11 have been designed, produced and evaluated to maintain the national traceability and reliability of the radiation measurement and to provide precise calibration of the various radiation measuring instruments as well as standard irradiation of the personal dosimeters for the performance evaluation. Existing dose calculation algorithm has been improved to correctly evaluate the shallow dose from the β(Ti-204) + γ(Cs-137) mixed radiation exposure by applying the TLD response correction function newly derived in this study. A mathematical algorithm to calculate the internal dose from inhalation of the uranium isotopes has been developed on the basis of the ICRP-30 respiratory tract model. Detailed performance analysis of the KAERI lung counter has been carried out to participate in the intercomparison of lung dosimetry. A preliminary and basic study on the quantitative method of optimal dose reduction based on the ALARA concept has been performed to technically support and strengthen the national radiation protection infrastructure. (Author)

  5. The Fermi surface and band folding in La{sub 2-x}Sr{sub x}CuO{sub 4}, probed by angle-resolved photoemission

    Energy Technology Data Exchange (ETDEWEB)

    Razzoli, E; Radovic, M; Patthey, L; Shi, M [Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland); Sassa, Y; Chang, J [Laboratory for Neutron Scattering, Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland); Drachuck, G; Keren, A; Shay, M [Department of Physics, Technion-Israel Institute of Technology, Haifa 32000 (Israel); Maansson, M; Mesot, J [Laboratory for Synchrotron and Neutron Spectroscopy, EPF Lausanne, CH-1015 Lausanne (Switzerland); Berntsen, M H; Tjernberg, O [Materials Physics, KTH Royal Institute of Technology, S-16440 Kista (Sweden); Pailhes, S [CEA, CNRS, CE Saclay, Laboratoire Leon Brillouin, F-91191 Gif Sur Yvette (France); Momono, N [Department of Applied Sciences, Muroran Institute of Technology, Muroran 050-8585 (Japan); Oda, M; Ido, M [Department of Physics, Hokkaido University, Sapporo 060-0810 (Japan); Lipscombe, O J; Hayden, S M, E-mail: ming.shi@psi.c [H H Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL (United Kingdom)

    2010-12-15

    A systematic angle-resolved photoemission study of the electronic structure of La{sub 2-x}Sr{sub x}CuO{sub 4} in a wide doping range is presented in this paper. In addition to the main energy band, we observed a weaker additional band, the ({pi}, {pi}) folded band, which shows unusual doping dependence. The appearance of the folded band suggests that a Fermi surface reconstruction is doping dependent and could already occur at zero magnetic field.

  6. Theory of temperature dependent photoemission spectrum of heavy fermion semiconductors

    International Nuclear Information System (INIS)

    Riseborough, P.S.

    1998-01-01

    The heavy fermion semiconductors are a class of strongly correlated materials, that at high temperatures show properties similar to those of heavy fermion materials, but at low temperatures show a cross-over into a semi-conducting state. The low temperature insulating state is characterized by an anomalously small energy gap, varying between 10 and 100 K. The smallness of the gap is attributed to the result of a many-body renormalization, and is temperature dependent. The temperature dependence of the electronic spectral density of states is calculated, using the Anderson lattice model at half filling. The spectrum is calculated to second order in 1/N, where N is the degeneracy of the 'f' orbitals, using a slave boson technique. The system is an indirect gap semi-conductor, with an extremely temperature dependent electronic spectral density A(k, ω). The indirect gap is subject to a temperature dependent many-body renormalization, and leads to a sharp temperature dependent structure in the angle resolved photo-emission spectrum at the indirect threshold. The theoretical predictions are compared with experimental observations on FeSi. (Copyright (1998) World Scientific Publishing Co. Pte. Ltd)

  7. Radiation-induced cancers in the rat, an experimental study

    International Nuclear Information System (INIS)

    Morin, M.; Lafuma, J.

    1990-01-01

    Radiation carcinogenesis at low doses raises a major radiological protection problem; we have attempted to deal with it through animal investigations involving over 3,000 rats. For various radiation types, dose-effect relationships as well as possible synergies with endogenous or exogenous chemical factors were studied. The chief problem being the possibility of extrapolation to man, a comparison was made between man and rat with the only human data available from radon inhalation in uranium miners [fr

  8. Studies on flame retardancy of radiation crosslinked PE foam

    International Nuclear Information System (INIS)

    Yang Huili; Yao Zhanhai; Xu Jun

    1996-01-01

    CPE, DBDPO and Sb 2 O 3 were used as flame-retardant of PE foam. Effect of CPE on PE foam under radiation and it's flame-retardancy were studied. The result showed that CPE can enhance radiation cross-linking of PE, and trinary of addition being made of CPE, DBDPO and Sb 2 O 3 made oxygen index of PE foam achieve over 30, and self-extinguish, it did not influence manufacture and mechanical properties of PE foam

  9. Radiation-induced cancers in the rat, an experimental study

    International Nuclear Information System (INIS)

    Morin, M.; Lafuma, J.

    1988-09-01

    Radiation carcinogenesis at low doses raises a major radiological protection problem; we have attempted to deal with it through animal investigations involving over 3,000 rats. For various radiation types, dose-effect relationships as well as possible synergies with endogenous or exogenous chemical factors were studied. The chief problem being the possibility of extrapolation to man, a comparison was made between man and rat with the only human data available from radon inhalation in uranium miners [fr

  10. Transition to intermediate valence state and x-ray photoemission in Sm/sub 1-x/Gd/sub x/S

    International Nuclear Information System (INIS)

    Campagna, M.; Chui, S.T.; Wertheim, G.K.; Tosatti, E.

    1976-01-01

    We report a systematic x-ray photoemission study of the alloys Sm 1 /sub -//subx/Gd/subx/S for 0 2+ → Sm 3+ photoemission line shape using a model which has some similarities with the Jaccarino-Walker model for magnetic alloys. It assumes the existence of only two different kinds of Sm 2+ ions in Sm 1 /sub -//subx/Gd/subx/S for x approximately-less-than 16%. We discuss possible reasons for the fact that Gd does not show the usual clustering effects known to occur in many substitutional rare-earth alloys. Lattice-constant measurements for various substituents further illustrate the importance of electronic effects in the phase transition

  11. Radiation dose to the patient in radionuclide studies

    International Nuclear Information System (INIS)

    Roedler, H.D.

    1981-01-01

    In medical radionuclide studies, the radiation risk has to be considered in addition to the general risk of administering a pharmaceutical. As radiation exposure is an essential factor in radiation risk estimation, some aspects of internal dose calculation, including radiation risk assessments, are treated. The formalism of current internal dose calculation is presented. The input data, especially the residence time and the absorbed dose per transformation, their origin and accuracy are discussed. Results of internal dose calculations for the ten most frequently used radionuclide studies are presented as somatically effective dose equivalents. The accuracy of internal dose calculation is treated in detail by considering the biokinetics of the radiopharmaceutical, the phantoms used for dose calculations, the absorbed dose per transformation, the administered activity, and the transfer of the dose, calculated for a phantom, to the patient. The internal dose calculated for a reference phantom may be assumed to be in accordance with the actual patient dose within a range described by a factor of about two to three. Finally, risk estimates for nuclear medicine procedures are quantified, being generally of sixth order. The radiation risk from the radioiodine test is comparably higher, but probably lower than calculated according to the UNSCEAR risk coefficients. However, further studies are needed to confirm these preliminary results and to improve the quantification of the radiation risk from the medical use of radionuclides. (author)

  12. Growth and photoemission spectroscopic studies of ultrathin noble ...

    Indian Academy of Sciences (India)

    2015-05-24

    May 24, 2015 ... Growth of Cu, Ag and Au thin films on graphite(0 0 0 1)surface and possible ... als on HOPG, MoTe2, WTe2, WSe2 [5,14,15] and on single-crystalline ..... but with opposite sign, and as a result Ag grows epitaxially even at RT, ...

  13. Photoemission studies of amorphous silicon induced by P + ion implantation

    Science.gov (United States)

    Petö, G.; Kanski, J.

    1995-12-01

    An amorphous Si layer was formed on a Si (1 0 0) surface by P + implantation at 80 keV. This layer was investigated by means of photoelectron spectroscopy. The resulting spectra are different from earlier spectra on amorphous Si prepared by e-gun evaporation or cathode sputtering. The differences consist of a decreased intensity in the spectral region corresponding to p-states, and appearace of new states at higher binding energy. Qualitativity similar results have been reported for Sb implanted amorphous Ge and the modification seems to be due to the changed short range order.

  14. X-Ray Photoemission Study of the Oxidation of Hafnium

    International Nuclear Information System (INIS)

    Chourasia, R.; Hickman, J.L.; Miller, R.L.; Nixon, G.A.; Seabolt, M.A.

    2011-01-01

    About 20 angstrom of hafnium were deposited on silicon substrates using the electron beam evaporation technique. Two types of samples were investigated. In one type, the substrate was kept at the ambient temperature. After the deposition, the substrate temperature was increased to 100, 200, and 300 degree C. In the other type, the substrate temperature was held fixed at some value during the deposition. For this type, the substrate temperatures used were 100, 200, 300, 400, 500, 550, and 600 degree C. The samples were characterized in situ by the technique of X-ray photoelectron spectroscopy. No trace of elemental hafnium is observed in the deposited overlayer. Also, there is no evidence of any chemical reactivity between the overlayer and the silicon substrate over the temperature range used. The hafnium overlayer shows a mixture of the dioxide and the suboxide. The ratio of the suboxide to dioxide is observed to be more in the first type of samples. The spectral data indicate that hafnium has a strong affinity for oxygen. The overlayer gets completely oxidized to form HfO 2 at substrate temperature around 300 degree C for the first type of samples and at substrate temperature greater than 550 degree C for the second type

  15. X-Ray Photoemission Study of the Oxidation of Hafnium

    Directory of Open Access Journals (Sweden)

    A. R. Chourasia

    2009-01-01

    Full Text Available About 20 Å of hafnium were deposited on silicon substrates using the electron beam evaporation technique. Two types of samples were investigated. In one type, the substrate was kept at the ambient temperature. After the deposition, the substrate temperature was increased to 100, 200, and 300∘C. In the other type, the substrate temperature was held fixed at some value during the deposition. For this type, the substrate temperatures used were 100, 200, 300, 400, 500, 550, and 600∘C. The samples were characterized in situ by the technique of X-ray photoelectron spectroscopy. No trace of elemental hafnium is observed in the deposited overlayer. Also, there is no evidence of any chemical reactivity between the overlayer and the silicon substrate over the temperature range used. The hafnium overlayer shows a mixture of the dioxide and the suboxide. The ratio of the suboxide to dioxide is observed to be more in the first type of samples. The spectral data indicate that hafnium has a strong affinity for oxygen. The overlayer gets completely oxidized to form HfO2 at substrate temperature around 300∘C for the first type of samples and at substrate temperature greater than 550∘C for the second type.

  16. Final state effects in photoemission studies of Fermi surfaces

    International Nuclear Information System (INIS)

    Kurtz, Richard L; Browne, Dana A; Mankey, Gary J

    2007-01-01

    Photoelectron spectroscopy is one of the most important methods for extracting information about the Fermi surface (FS) of materials. An electron photoexcited from the FS is emitted from the crystal conserving the parallel momentum, k parallel , while the perpendicular momentum k perpendicular is reduced due to the surface potential barrier. A simple interpretation of the process assumes the final state is free-electron-like allowing one to 'map' the detected photoelectron back to its initial k momentum. There are multiple final state effects that can complicate the interpretation of photoelectron data and these effects are reviewed here. These can involve both energy and k broadening, which can give rise to shadow or ghost FS contours, scattering and final state diffraction effects that modify intensities, and matrix element effects which reflect the symmetries of the states involved and can be highly dependent on photon polarization. These matrix elements result in contours of photoelectron intensity that follow the dispersion in k-space of the initial state, the FS, and the final state. Locations where intensities go to zero due to matrix element and symmetry effects can result in gaps where FS contours 'disappear'. Recognition that these effects can play a significant role in determining the measured angular distributions is crucial in developing an informed model of where the FS contours actually lie in relation to measured intensity contours

  17. Radiation sensitization studies by silymarin on HCT-15 cells

    International Nuclear Information System (INIS)

    Lal, Mitu; Gupta, Damodar; Arora, R.

    2014-01-01

    Radiotherapy has been widely used for treatment of human cancers. However, cancer cells develop radioresistant phenotypes following multiple exposures to the treatment agent that decrease the efficacy of radiotherapy. Here it was investigated that the radiation sensitization effects of silymarin found in colon cancer. The aim of this study was to investigate mechanisms involved in radiation sensitization growth inhibitory effect of silymarin in combination with radiation, in Human colon carcinoma (HCT-15). The human colon carcinoma was utilized and SRB-assay was performed to study anti-proliferative effect of silymarin in combination with gamma radiation (2 Gy) appropriate radiation dose was optimized and confirmed by clonogenic assay. Microscopic analysis was done by staining with Hoechst-33342, DAPI, Propidium iodide to confirm the presence of apoptosis. Nitric oxide production, changes in lipid peroxidation, Cell cycle analysis were carried out and mitochondrial membrane potential was measured by uptake of cationic dye JC-1 by using flow cytometer. Silymarin in combination with radiation (2 Gy) inhibited 70% ± 5% population growth of HCT-15 cells in time and dose dependent manner. Pre treatment of cells with silymarin for 30 min before radiation was found to be most effective for radiation sensitization. There was 25% increase in levels of nitric oxide as compare to control, whereas 2.5 fold change in lipid peroxidation with respect to control. IR-induced apoptosis in HCT-15 cell line was significantly enhanced by silymarin, as reflected by viability, DNA fragmentation, and mitochondrial dysfunction. Additionally, silymarin in combination with IR is found to be effective in sensitization of HCT-15 cells. In vivo studies on development of tumor and sensitization aspects needs to done in future. (author)

  18. Studies of workers exposed to low doses of external radiation

    International Nuclear Information System (INIS)

    Gilbert, E.S.

    1991-04-01

    Currently, several epidemiologic studies of workers who have been exposed occupationally to low levels of radiation are being conducted, and include studies of workers in the United States, Great Britain, and Canada involved in the production of both defense materials and nuclear power. This paper focuses on studies that evaluate the possible adverse effects resulting from external exposure to radiation. The radiation risk estimates that have been used to establish radiation protection standards for workers and others have been obtained mainly from studies of persons exposed at high doses and dose rates. However, questions remain with regard to the extrapolation process that has been necessary for estimating low-level radiation risks. Occupational studies provide a direct assessment of risk based on data on persons exposed at the actual levels of interest. If current risk estimates are correct, these studies have very little chance of detecting risk, but can still be used to provide useful upper limits on risks. The studies are also adequate to detect serious underestimation of risks. 36 refs., 3 figs., 3 tabs

  19. Photoemission and photo-field-emission from photocathodes with arrays of silicon tips under continuous and pulsed lasers action

    International Nuclear Information System (INIS)

    Laguna, M.

    1995-11-01

    The electron machines's development and improvement go through the discovery of new electron sources of high brightness. After reminding the interests in studying silicon cathodes with array of tips as electron sources, I describe, in the three steps model, the main phenomenological features related to photoemission and photoemission and photo-field-emission from a semi-conductor. the experimental set-ups used for the measurements reported in chapter four, five and six are described in chapter three. In chapter three. In chapter four several aspects of photo-field-emission in continuous and nanosecond regimes, studied on the Clermont-Ferrand's test bench are tackled. We have measured quantum efficacies of 0.4 percent in the red (1.96 eV). Temporal responses in the nanoseconds range (10 ns) were observed with the Nd: YLF laser. With the laser impinging at an oblique angle we obtained ratios of photocurrent to dark current of the order of twenty. The issue of the high energy extracted photocurrent saturation is addressed and I give a preliminary explanation. In collaboration with the L.A.L. (Laboratoire de l'Accelerateur Lineaire) some tests with shortened pulsed laser beam (Nd: YAG laser 35 ps) were performed. Satisfactory response times have been obtained within the limitation of the scope (400 ps). (authors). 101 refs. 93 figs., 27 tabs., 3 photos., 1 append

  20. Study of collagen metabolism after β radiation injury

    International Nuclear Information System (INIS)

    Zhou Yinghui; Xulan; Wu Shiliang; Zhang Xueguang; Chen Liesong

    2000-01-01

    Objective: To investigate the change of collagen metabolism and it's regulation after β radiation. Method: The animal model of β radiation injury was established by the β radiation produced by the linear accelerator; and irradiated NIH 3T3 cells were studied. In the experiment the contents of total collagen, collagen type I and type III were measured. The activity of MMPs-1 was tested. The contents of TGF-β 1 , IL-6 were also detected. Results: After exposure to β radiation, little change was found in the content of total collagen, but the content of collagen I decreased and the content of collagen III, MMPs-1 activity increased; the expression of TGF-β 1 , IL-6 increased. Conclusion: The changes in the metabolism of collagen play an important role in the irradiated injury of the skin; TGF-β 1 and IL-6 may be essential in the regulation of the collagen metabolism