WorldWideScience

Sample records for energy-resolved photoelectron angular

  1. Coherent Control of Photoelectron Wavepacket Angular Interferograms

    OpenAIRE

    Hockett, Paul; Wollenhaupt, Matthias; Baumert, Thomas

    2015-01-01

    Coherent control over photoelectron wavepackets, via the use of polarization-shaped laser pulses, can be understood as a time and polarization-multiplexed process. In this work, we investigate this multiplexing via computation of the observable photoelectron angular interferograms resulting from multi-photon atomic ionization with polarization-shaped laser pulses. We consider the polarization sensitivity of both the instantaneous and cumulative continuum wavefunction; the nature of the cohere...

  2. Coherent control of photoelectron wavepacket angular interferograms

    International Nuclear Information System (INIS)

    Hockett, P; Wollenhaupt, M; Baumert, T

    2015-01-01

    Coherent control over photoelectron wavepackets, via the use of polarization-shaped laser pulses, can be understood as a time and polarization-multiplexed process, where the final (time-integrated) observable coherently samples all instantaneous states of the light–matter interaction. In this work, we investigate this multiplexing via computation of the observable photoelectron angular interferograms resulting from multi-photon atomic ionization with polarization-shaped laser pulses. We consider the polarization sensitivity of both the instantaneous and cumulative continuum wavefunction; the nature of the coherent control over the resultant photoelectron interferogram is thus explored in detail. Based on this understanding, the use of coherent control with polarization-shaped pulses as a methodology for a highly multiplexed coherent quantum metrology is also investigated, and defined in terms of the information content of the observable. (paper)

  3. Coherent control of photoelectron wavepacket angular interferograms

    Science.gov (United States)

    Hockett, P.; Wollenhaupt, M.; Baumert, T.

    2015-11-01

    Coherent control over photoelectron wavepackets, via the use of polarization-shaped laser pulses, can be understood as a time and polarization-multiplexed process, where the final (time-integrated) observable coherently samples all instantaneous states of the light-matter interaction. In this work, we investigate this multiplexing via computation of the observable photoelectron angular interferograms resulting from multi-photon atomic ionization with polarization-shaped laser pulses. We consider the polarization sensitivity of both the instantaneous and cumulative continuum wavefunction; the nature of the coherent control over the resultant photoelectron interferogram is thus explored in detail. Based on this understanding, the use of coherent control with polarization-shaped pulses as a methodology for a highly multiplexed coherent quantum metrology is also investigated, and defined in terms of the information content of the observable.

  4. Practical scaling law for photoelectron angular distributions

    International Nuclear Information System (INIS)

    Guo Dongsheng; Zhang Jingtao; Xu Zhizhan; Li Xiaofeng; Fu Panming; Freeman, R.R.

    2003-01-01

    A practical scaling law that predicts photoelectron angular distributions (PADs) is derived using angular distribution formulas which explicitly contain spontaneous emission. The scaling law is used to analyze recent PAD measurements in above-threshold ionization, and to predict results of future experiments. Our theoretical and numerical studies show that, in the non-relativistic regime and long-wavelength approximation, the shapes of PADs are determined by only three dimensionless numbers: (1) u p ≡U p /(ℎ/2π)ω, the ponderomotive number (ponderomotive energy in units of laser photon energy); (2) ε b ≡E b /(ℎ/2π)ω, the binding number (atomic binding energy in units of the laser photon energy); (3) j, the absorbed-photon number. The scaling law is shown to be useful in predictions of results from strong-field Kapitza-Dirac effect measurements; specifically, the application of this scaling law to recently reported Kapitza-Dirac diffraction is discussed. Possible experimental tests to verify the scaling law are suggested

  5. Angular distribution of photoelectrons from atomic oxygen, nitrogen, and carbon

    Science.gov (United States)

    Manson, S. T.; Kennedy, D. J.; Starace, A. F.; Dill, D.

    1974-01-01

    The angular distribution of photoelectrons from atomic oxygen is investigated using Hartree-Fock (HF) wave functions. The correct formulation is used to compare HS and HF results. Agreement between these results is good and the HS calculations have been extended to atomic nitrogen and carbon as well.

  6. Photoelectron and ICD electron angular distributions from fixed-in-space neon dimers

    Energy Technology Data Exchange (ETDEWEB)

    Jahnke, T [Institut fuer Kernphysik, J W Goethe-Universitaet Frankfurt am Main, Max-von-Laue-Str. 1, D-60438 Frankfurt (Germany); Czasch, A [Institut fuer Kernphysik, J W Goethe-Universitaet Frankfurt am Main, Max-von-Laue-Str. 1, D-60438 Frankfurt (Germany); Schoeffler, M [Institut fuer Kernphysik, J W Goethe-Universitaet Frankfurt am Main, Max-von-Laue-Str. 1, D-60438 Frankfurt (Germany); Schoessler, S [Institut fuer Kernphysik, J W Goethe-Universitaet Frankfurt am Main, Max-von-Laue-Str. 1, D-60438 Frankfurt (Germany); Kaesz, M [Institut fuer Kernphysik, J W Goethe-Universitaet Frankfurt am Main, Max-von-Laue-Str. 1, D-60438 Frankfurt (Germany); Titze, J [Institut fuer Kernphysik, J W Goethe-Universitaet Frankfurt am Main, Max-von-Laue-Str. 1, D-60438 Frankfurt (Germany); Kreidi, K [Institut fuer Kernphysik, J W Goethe-Universitaet Frankfurt am Main, Max-von-Laue-Str. 1, D-60438 Frankfurt (Germany); Grisenti, R E [Institut fuer Kernphysik, J W Goethe-Universitaet Frankfurt am Main, Max-von-Laue-Str. 1, D-60438 Frankfurt (Germany); Staudte, A [Steacie Institute for Molecular Sciences, 100 Sussex Drive, Ottawa (Canada); Jagutzki, O [Institut fuer Kernphysik, J W Goethe-Universitaet Frankfurt am Main, Max-von-Laue-Str. 1, D-60438 Frankfurt (Germany); Schmidt, L Ph H [Institut fuer Kernphysik, J W Goethe-Universitaet Frankfurt am Main, Max-von-Laue-Str. 1, D-60438 Frankfurt (Germany); Semenov, S K [State University of Aerospace Instrumentation, 190000 St. Petersburg (Russian Federation); Cherepkov, N A [State University of Aerospace Instrumentation, 190000 St. Petersburg (Russian Federation); Schmidt-Boecking, H [Institut fuer Kernphysik, J W Goethe-Universitaet Frankfurt am Main, Max-von-Laue-Str. 1, D-60438 Frankfurt (Germany); Doerner, R [Institut fuer Kernphysik, J W Goethe-Universitaet Frankfurt am Main, Max-von-Laue-Str. 1, D-60438 Frankfurt (Germany)

    2007-07-07

    We report on molecular frame angular distributions of 2s photoelectrons and electrons emitted by interatomic Coulombic decay from neon dimers. We found that the measured angular distribution of the photoelectron strongly depends on the environment of the cluster. The experimental results are in excellent agreement with frozen core Hartree-Fock calculations. The ICD electrons show slight variations in their angular distribution for different kinetic energies.

  7. Time- and energy resolved photoemission electron microscopy-imaging of photoelectron time-of-flight analysis by means of pulsed excitations

    International Nuclear Information System (INIS)

    Oelsner, Andreas; Rohmer, Martin; Schneider, Christian; Bayer, Daniela; Schoenhense, Gerd; Aeschlimann, Martin

    2010-01-01

    The present work enlightens the developments in time- and energy resolved photoemission electron microscopy over the past few years. We describe basic principles of the technique and demonstrate different applications. An energy- and time-filtering photoemission electron microscopy (PEEM) for real-time spectroscopic imaging can be realized either by a retarding field or hemispherical energy analyzer or by using time-of-flight optics with a delay line detector. The latter method has the advantage of no data loss at all as all randomly incoming particles are measured not only by position but also by time. This is of particular interest for pump-probe experiments in the femtosecond and attosecond time scale where space charge processes drastically limit the maximum number of photoemitted electrons per laser pulse. This work focuses particularly on time-of-flight analysis using a novel delay line detector. Time and energy resolved PEEM instruments with delay line detectors enable 4D imaging (x, y, Δt, E Kin ) on a true counting basis. This allows a broad range of applications from real-time observation of dynamic phenomena at surfaces to fs time-of-flight spectro-microscopy and even aberration correction. By now, these time-of-flight analysis instruments achieve intrinsic time resolutions of 108 ps absolute and 13.5 ps relative. Very high permanent measurement speeds of more than 4 million events per second in random detection regimes have been realized using a standard USB2.0 interface. By means of this performance, the time-resolved PEEM technique enables to display evolutions of spatially resolved (<25 nm) and temporal sliced images life on any modern computer. The method allows dynamics investigations of variable electrical, magnetic, and optical near fields at surfaces and great prospects in dynamical adaptive photoelectron optics. For dynamical processes in the ps time scale such as magnetic domain wall movements, the time resolution of the delay line detectors

  8. Multiple scattering theory of photoelectron angular distributions from oriented diatomic molecules

    Energy Technology Data Exchange (ETDEWEB)

    Diez Muino, R.; Rolles, D.; Garcia de Abajo, F.J.; Fadley, C.S.; Van Hove, M.A.

    2001-09-17

    We use multiple scattering photoelectron diffraction (MSPD) theory to calculate the angular patterns of electrons photoemitted from the K shell of CO and N2 gas-phase oriented molecules, as recently measured by several groups.

  9. The calculation of photoelectron angular distributions with jet-like structure from scattering theory

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Jingtao [Laboratory for High Intensity Optics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, PO Box 800-211, Shanghai (China); Zhang Wenqi [Laboratory for High Intensity Optics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, PO Box 800-211, Shanghai (China); Xu Zhizhan [Laboratory for High Intensity Optics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, PO Box 800-211, Shanghai (China); Li Xiaofeng [Laboratory of Optical Physics, Institute of Physics, Chinese Academy of Sciences, Beijing (China); Fu Panming [Laboratory of Optical Physics, Institute of Physics, Chinese Academy of Sciences, Beijing (China); Guo Dongsheng [Department of Physics, Southern University and A and M College, Baton Rouge, LA (United States); Freeman, R R [Department of Applied Science, University of California-Davis, Davis, CA (United States)

    2002-12-14

    Photoelectron angular distributions produced in above-threshold ionization (ATI) are analysed using a nonperturbative scattering theory. The numerical results are in good qualitative agreement with recent measurements. Our study shows that the origin of the jet-like structure arises from the inherent properties of the ATI process and not from the angular momentum of either the initial or the excited states of the atom.

  10. Angular distributions of photoelectrons from resonant two-photon ionization: A graphical approach

    International Nuclear Information System (INIS)

    Chien, R.

    1984-01-01

    The Liouville representation is a formalism that describes quantum mechanical problems by using the space of density operators as kets and the space of observable operators as bras. It is useful for problems with complicated angular momentum coupling because it gives directly the probabilities and expectation values rather than probability amplitudes, so that some of the extended and tedious steps of the angular momentum algebra are eliminated. The graphical representation of angular momentum coupling has proved itself as another way to simplify and clarify calculations; graphical representation helps one to visualize the physics and simplifies and organizes the computations. By combining the graphical method and Liouville representation, we introduce a simple, transparent method to deal with problems of many coupled angular momenta. We use this formalism to derive the analytic expression for the angular distributions of photoelectrons. The angular distributions are represented by diagrams of density matrix and detector operators and a diagram of the transition matrix. The analytic expressions are then obtained from the diagrams by following simple general rules for the graphical reduction. A specific example, angular distributions of photoelectrons from resonant two-photon ionization of alkali atoms with hyperfine interaction, is also given

  11. Angular distribution of photoelectrons from atomic oxygen, nitrogen and carbon. [in upper atmosphere

    Science.gov (United States)

    Manson, S. J.; Kennedy, D. J.; Starace, A. F.; Dill, D.

    1974-01-01

    The angular distributions of photoelectrons from atomic oxygen, nitrogen, and carbon are calculated. Both Hartree-Fock and Hartree-Slater (Herman-Skillman) wave functions are used for oxygen, and the agreement is excellent; thus only Hartree-Slater functions are used for carbon and nitrogen. The pitch-angle distribution of photoelectrons is discussed, and it is shown that previous approximations of energy-independent isotropic or sin squared theta distributions are at odds with the authors' results, which vary with energy. This variation with energy is discussed, as is the reliability of these calculations.

  12. The potentialities of ion beam diagnostics by photoelectrons with an angular asymmetry parameter β0 =-1

    International Nuclear Information System (INIS)

    Artemov, A.S.; Avidzba, A.A.

    1993-01-01

    For the photoelectrons, produced with an angular asymmetry parameter β 0 = -1, by numerical simulation the corresponding 'own' distributions in the space of transverse momenta and energy of the laboratory frame, are obtained. The potentialities of beam diagnostics are considered for the case when information about its parameters is passed to a flux of these electrons as the result of single-photon ionization of ions in a beam or intermediate particles, taking out beam information outside. Alongside to this, relatively small polarization influence of probing photon target on the repetition accuracy of phase space portrait of the beam by photoelectrons, is taking place. (author.). 13 refs.; 9 figs

  13. Molecular frame photoelectron angular distribution for oxygen 1s photoemission from CO2 molecules

    International Nuclear Information System (INIS)

    Saito, N; Ueda, K; De Fanis, A

    2005-01-01

    We have measured photoelectron angular distributions in the molecular frame (MF-PADs) for O 1s photoemission from CO 2 , using photoelectron-O + -CO + coincidence momentum imaging. Results for the molecular axis at 0, 45 and 90 0 to the electric vector of the light are reported. The major features of the MF-PADs are fairly well reproduced by calculations employing a relaxed-core Hartree-Fock approach. Weak asymmetric features are seen through a plane perpendicular to the molecular axis and attributed to symmetry lowering by anti-symmetric stretching motion. (letter to the editor)

  14. Non-dipole angular anisotropy parameters of photoelectrons from semi-filled shell atoms

    Energy Technology Data Exchange (ETDEWEB)

    Amusia, M Ya [Racah Institute of Physics, Hebrew University, Jerusalem 91904 (Israel); Chernysheva, L V [Ioffe Physical-Technical Institute, St-Petersburg 194021 (Russian Federation)

    2006-11-28

    We present the results of calculations of outer and next to outer shell non-dipole angular anisotropy parameters of photoelectrons for semi-filled shell atoms in the Hartree-Fock (HF) one-electron approximation and in the frame of the spin polarized random phase approximation with exchange (SP RPAE) which takes into account inter-electron correlations. We demonstrate for the first time that this characteristic of the photoionization process is essentially sensitive to whether the photoelectron has the same or opposite spin orientation to that of the semi-filled shell.

  15. Non-dipole angular anisotropy parameters of photoelectrons from semi-filled shell atoms

    International Nuclear Information System (INIS)

    Amusia, M Ya; Chernysheva, L V

    2006-01-01

    We present the results of calculations of outer and next to outer shell non-dipole angular anisotropy parameters of photoelectrons for semi-filled shell atoms in the Hartree-Fock (HF) one-electron approximation and in the frame of the spin polarized random phase approximation with exchange (SP RPAE) which takes into account inter-electron correlations. We demonstrate for the first time that this characteristic of the photoionization process is essentially sensitive to whether the photoelectron has the same or opposite spin orientation to that of the semi-filled shell

  16. Calculation of photodetachment cross sections and photoelectron angular distributions of negative ions using density functional theory.

    Science.gov (United States)

    Liu, Yuan; Ning, Chuangang

    2015-10-14

    Recently, the development of photoelectron velocity map imaging makes it much easier to obtain the photoelectron angular distributions (PADs) experimentally. However, explanations of PADs are only qualitative in most cases, and very limited works have been reported on how to calculate PAD of anions. In the present work, we report a method using the density-functional-theory Kohn-Sham orbitals to calculate the photodetachment cross sections and the anisotropy parameter β. The spherical average over all random molecular orientation is calculated analytically. A program which can handle both the Gaussian type orbital and the Slater type orbital has been coded. The testing calculations on Li(-), C(-), O(-), F(-), CH(-), OH(-), NH2 (-), O2 (-), and S2 (-) show that our method is an efficient way to calculate the photodetachment cross section and anisotropy parameter β for anions, thus promising for large systems.

  17. Time-Resolved Photoelectron Angular Distributions from Strong-Field Ionization of Rotating Naphthalene Molecules

    DEFF Research Database (Denmark)

    Hansen, Jonas Lerche; Stapelfeldt, Henrik; Dimitrovski, Darko

    2011-01-01

    A nanosecond laser pulse confines the spatial orientation of naphthalene in 1D or 3D while a femtosecond kick pulse initiates rotation of the molecular plane around the fixed long axis. Time-dependent photoelectron angular distributions (PADs), resulting from ionization by an intense femtosecond...... probe pulse, exhibit pronounced changes as the molecular plane rotates. Enhanced 3D alignment, occurring shortly after the kick pulse, provides strongly improved contrast in molecular-frame PADs. Calculations in the strong-field approximation show that the striking structures observed in the PADs...

  18. Core-Hole Molecular Frame X-Ray Photoelectron Angular Distributions as Molecular Geometry Probes

    Science.gov (United States)

    Trevisan, Cynthia; Williams, Joshua; Menssen, Adrian; Weber, Thorsten; Rescigno, Thomas; McCurdy, Clyde; Landers, Allen

    2014-05-01

    We present experimental and theoretical results for the angular dependence of electrons ejected from the core orbitals of ethane (C2H6) and tetrafluoromethane (CF4) in an effort to understand the origin of the imaging effect by which the molecular frame photoelectron angular distributions (MFPADs) for removing an electron from a 1s orbital effectively image the geometry of a class of molecules. At low energies, our calculations predict the same imaging effect in X2H6 previously found in CH4, H2O and NH3. By contrast, in experiment and calculations CF4 displays an anti-imaging effect, whereby the electron ejected by core photoionization has the tendency to avoid molecular bonds, if averaged over directions of polarization of the incident X-ray beam. Our measurements employ the COLTRIMS method and the calculations were performed with the Complex Kohn Variational method.

  19. Variable Mixed Orbital Character in the Photoelectron Angular Distribution of NO_{2}

    Science.gov (United States)

    Laws, Benjamin A.; Cavanagh, Steven J.; Lewis, Brenton R.; Gibson, Stephen T.

    2017-06-01

    NO_{2} a key component of photochemical smog and an important species in the Earth's atmosphere, is an example of a molecule which exhibits significant mixed orbital character in the HOMO. In photoelectron experiments the geometric properties of the parent anion orbital are reflected in the photoelectron angular distribution (PAD), an area of research that has benefited largely from the ability of velocity-map imaging (VMI) to simultaneously record both the energetic and angular information, with 100% collection efficiency. Photoelectron spectra of NO_{2}^{-}, taken over a range of wavelengths (355nm-520nm) with the ANU's VMI spectrometer, reveal an anomalous jump in the anisotropy parameter near threshold. Consequently, the orbital behavior of NO_{2}^{-} appears to be quite different near threshold compared to detachment at higher photon energies. This surprising effect is due to the Wigner Threshold law, which causes p orbital character to dominate the photodetachment cross-section near threshold, before the mixed s/d orbital character becomes significant at higher electron kinetic energies. By extending recent work on binary character models to form a more general expression, the variable mixed orbital character of NO_{2}^{-} is able to be described. This study provides the first multi-wavelength NO_{2} anisotropy data, which is shown to be in decent agreement with much earlier zero-core model predictions of the anisotropy parameter. K. J. Reed, A. H. Zimmerman, H. C. Andersen, and J. I. Brauman, J. Chem. Phys. 64, 1368, (1976). doi:10.1063/1.432404 D. Khuseynov, C. C. Blackstone, L. M. Culberson, and A. Sanov, J. Chem. Phys. 141, 124312, (2014). doi:10.1063/1.4896241 W. B. Clodius, R. M. Stehman, and S. B. Woo, Phys. Rev. A. 28, 760, (1983). doi:10.1103/PhysRevA.28.760 Research supported by the Australian Research Council Discovery Project Grant DP160102585

  20. Calculation of photodetachment cross sections and photoelectron angular distributions of negative ions using density functional theory

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yuan [Department of Physics, State Key Laboratory of Low-Dimensional Quantum Physics, Tsinghua University, Beijing 100084 (China); Ning, Chuangang, E-mail: ningcg@tsinghua.edu.cn [Department of Physics, State Key Laboratory of Low-Dimensional Quantum Physics, Tsinghua University, Beijing 100084 (China); Collaborative Innovation Center of Quantum Matter, Beijing (China)

    2015-10-14

    Recently, the development of photoelectron velocity map imaging makes it much easier to obtain the photoelectron angular distributions (PADs) experimentally. However, explanations of PADs are only qualitative in most cases, and very limited works have been reported on how to calculate PAD of anions. In the present work, we report a method using the density-functional-theory Kohn-Sham orbitals to calculate the photodetachment cross sections and the anisotropy parameter β. The spherical average over all random molecular orientation is calculated analytically. A program which can handle both the Gaussian type orbital and the Slater type orbital has been coded. The testing calculations on Li{sup −}, C{sup −}, O{sup −}, F{sup −}, CH{sup −}, OH{sup −}, NH{sub 2}{sup −}, O{sub 2}{sup −}, and S{sub 2}{sup −} show that our method is an efficient way to calculate the photodetachment cross section and anisotropy parameter β for anions, thus promising for large systems.

  1. Effects of spin-orbit activated interchannel coupling on dipole photoelectron angular distribution asymmetry parameters

    Energy Technology Data Exchange (ETDEWEB)

    Amusia, M Ya [Racah Institute of Physics, Hebrew University, Jerusalem 91904 (Israel); Baltenkov, A S [Arifov Institute of Electronics, Tashkent 70125 (Uzbekistan); Chernysheva, L V [A F Ioffe Physical-Technical Institute, St. Petersburg 194021 (Russian Federation); Felfli, Z [Center for Theoretical Studies of Physics Systems, Clark Atlanta University, Atlanta, GA 30314 (United States); Manson, S T [Department of Physics and Astronomy, Georgia State University, Atlanta, GA 30303 (United States); Msezane, A Z [Center for Theoretical Studies of Physics Systems, Clark Atlanta University, Atlanta, GA 30314 (United States)

    2004-02-28

    The effects of spin-orbit induced interchannel coupling on the dipole photoelectron angular asymmetry parameter {beta}{sub 3d} for Xe, Cs and Ba are explored using a modified version of the spin-polarized random phase approximation with exchange (SPRPAE) methodology. For Xe, {beta}{sub 3d{sub 5/2}} is modified somewhat by the interchannel coupling in the vicinity of the 3d{sub 3/2} {yields} {epsilon}f shape resonance, and this effect is significantly more pronounced in Cs where the resonance is larger. In Ba, however, where f-wave orbital collapse has occurred, the shape resonance has moved below threshold and the effect of interchannel coupling on {beta}{sub 3d{sub 5/2}} above the 3d{sub 3/2} threshold is negligible. But below the 3d{sub 3/2} threshold, {beta}{sub 3d{sub 5/2}} is dominated by the huge broad 3d{sub 3/2} {yields} 4f resonance.

  2. Photoelectron angular distributions for states of any mixed character: an experiment-friendly model for atomic, molecular, and cluster anions.

    Science.gov (United States)

    Khuseynov, Dmitry; Blackstone, Christopher C; Culberson, Lori M; Sanov, Andrei

    2014-09-28

    We present a model for laboratory-frame photoelectron angular distributions in direct photodetachment from (in principle) any molecular orbital using linearly polarized light. A transparent mathematical approach is used to generalize the Cooper-Zare central-potential model to anionic states of any mixed character. In the limit of atomic-anion photodetachment, the model reproduces the Cooper-Zare formula. In the case of an initial orbital described as a superposition of s and p-type functions, the model yields the previously obtained s-p mixing formula. The formalism is further advanced using the Hanstorp approximation, whereas the relative scaling of the partial-wave cross-sections is assumed to follow the Wigner threshold law. The resulting model describes the energy dependence of photoelectron anisotropy for any atomic, molecular, or cluster anions, usually without requiring a direct calculation of the transition dipole matrix elements. As a benchmark case, we apply the p-d variant of the model to the experimental results for NO(-) photodetachment and show that the observed anisotropy trend is described well using physically meaningful values of the model parameters. Overall, the presented formalism delivers insight into the photodetachment process and affords a new quantitative strategy for analyzing the photoelectron angular distributions and characterizing mixed-character molecular orbitals using photoelectron imaging spectroscopy of negative ions.

  3. Photoelectron angular distributions from the ionization of xenon Rydberg states by midinfrared radiation

    NARCIS (Netherlands)

    Huismans, Y.; Rouzee, A.; Gijsbertsen, A.; Logman, Pswm; Lepine, F.; Cauchy, C.; Zamith, S.; Stodolna, A. S.; Jungmann, J. H.; Bakker, J. M.; G. Berden,; Redlich, B.; van der Meer, A. F. G.; Schafer, K. J.; Vrakking, M. J. J.

    2013-01-01

    Angle-resolved photoelectron spectra, resulting from the strong-field ionization of atoms or molecules, carry a rich amount of information on ionization pathways, electron dynamics, and the target structure. We have investigated angle-resolved photoelectron spectra arising from the nonresonant

  4. Photoelectron angular distributions from O K shell of oriented CO molecules: A critical comparison between theory and experiment

    Science.gov (United States)

    Ito; Adachi; Hikosaka; Motoki; Soejima; Yagishita; Raseev; Cherepkov

    2000-07-03

    The dynamical information (ten dipole matrix elements and eight phase differences) has been deduced from the measured angular distributions of photoelectrons from O K shell of oriented CO molecules near the ionization threshold in the region of a sigma(*) shape resonance. Light polarization parallel and perpendicular to the molecular axis has been used. An important contribution of six lsigma partial waves with 0

  5. Inner-shell photoelectron angular distributions from fixed-in-space OCS molecules: comparison between experiment and theory

    Energy Technology Data Exchange (ETDEWEB)

    Golovin, A V [Photon Factory, Institute of Materials Structure Science, Tsukuba 305-0801 (Japan); Institute of Physics, St Petersburg State University, 198504 St Petersburg (Russian Federation); Adachi, J [Photon Factory, Institute of Materials Structure Science, Tsukuba 305-0801 (Japan); Graduate School of Science, University of Tokyo, Bunkyo-ku, Tokyo 113-0033 (Japan); Motoki, S [Graduate School of Science, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, (Japan); Takahashi, M [Institute for Molecular Science, Okazaki 444-8585 (Japan); Yagishita, A [Photon Factory, Institute of Materials Structure Science, Tsukuba 305-0801 (Japan); Graduate School of Science, University of Tokyo, Bunkyo-ku, Tokyo 113-0033 (Japan)

    2005-10-28

    Photoelectron angular distributions (PADs) for O 1s, C 1s and S 2p{sub 1/2}, 2p{sub 3/2} ionization of OCS molecules have been measured in shape resonance regions. These PAD results are compared with the results for O 1s and C 1s ionization of CO molecules, and multi-scattering X{alpha} (MSX{alpha}) calculations. The mechanism of the PAD formation both for parallel and perpendicular transitions differs very significantly in these molecules and a step from a two-centre potential (CO) to a three-centre potential (OCS) plays a principal role in electron scattering and the formation of the resulting PAD. For parallel transitions, it is found that for the S 2p and O 1s ionization the photoelectrons are emitted preferentially in a hemisphere directed to the ionized S and O atom, respectively. In OCS O 1s ionization, the S-C fragment plays the role of a strong 'scatterer' for photoelectrons, and in the shape resonance region most intensities of the PADs are concentrated on the region directed to the O atom. The MSX{alpha} calculations for perpendicular transitions reproduce the experimental data, but not so well as in the case of parallel transitions. The results of PAD, calculated with different l{sub max} on different atomic centres, reveal the important role of the d (l = 2) partial wave for the S atom in the partial wave decompositions of photoelectron wavefunctions.

  6. Magnetometry of buried layers—Linear magnetic dichroism and spin detection in angular resolved hard X-ray photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Gloskovskii, Andrei; Stryganyuk, Gregory; Fecher, Gerhard H.; Felser, Claudia; Thiess, Sebastian; Schulz-Ritter, Heiko; Drube, Wolfgang; Berner, Götz; Sing, Michael; Claessen, Ralph; Yamamoto, Masafumi

    2012-01-01

    Highlights: ► Newly commissioned HAXPES instrument at P09 beamline of the PETRA III ring at DESY. ► We report HAXPES studies on buried magnetic nanolayers in a multi-layer sample. ► Linear magnetic dichroism of photoelectrons from buried CoFe–Ir 78 Mn 22 layers. ► Spin-resolved HAXPES measurements on buried magnetic multilayers using Mott detector. - Abstract: The electronic properties of buried magnetic nano-layers were studied using the linear magnetic dichroism in the angular distribution of photoemitted Fe, Co, and Mn 2p electrons from a CoFe–Ir 78 Mn 22 multi-layered sample. The buried layers were probed using hard X-ray photoelectron spectroscopy, HAXPES, at the undulator beamline P09 of the 3rd generation storage ring PETRA III. The results demonstrate that this magnetometry technique can be used as a sensitive element specific probe for magnetic properties suitable for application to buried ferromagnetic and antiferromagnetic magnetic materials and multilayered spintronics devices. Using the same instrument, spin-resolved Fe 2p HAXPES spectra were obtained from the buried layer with good signal quality.

  7. Molecular Frame Photoelectron Angular Distributions for Core Ionization of CF4 and C2H2F2

    Science.gov (United States)

    Trevisan, C. S.; Williams, J. B.; Menssen, A. J.; Rescigno, T. N.; Dorner, R.; McCurdy, C. W.

    2015-05-01

    We present experimental and theoretical results for the angular dependence of electrons ejected from the core orbitals of tetrafluoromethane (CF4) which display a tendency to avoid molecular bonds if averaged over directions of polarization of the incident X-ray beam, in contrast to earlier cases (CH4, H2O and NH3) studied by the same methods. To investigate whether the imaging effect can be used to detect the creation of core holes by photoionization from one of two atoms of the same type in a molecule, we computed and measured MFPADs of difluoroethylene (C2H2F2). Good agreement with the experimentally measured angular distributions show that the MFPADs contain the clear signature of the core-hole origin of the photoelectron, and validate the use of computed MFPADs as promising tools for the interpretation of such experiments. Our measurements employ the COLTRIMS method and the calculations were performed with the Complex Kohn Variational method. Work supported in part by the USDOE, Office of Science, Office of WDTS under the Visiting Faculty Program.

  8. Photoionization of the 4d10 subshell of cadmium: Photoelectron angular distributions and polarization of fluorescence radiation

    Science.gov (United States)

    Theodosiou, Constantine E.; Starace, Anthony F.; Tambe, B. R.; Manson, Steven T.

    1981-07-01

    Relativistic Dirac-Fock calculations are presented for the photoelectron angular distribution asymmetry parameter β corresponding to 4d-subshell photoionization in Cd and for the linear polarization PL of the subsequent fluorescence radiation, for photon energies less than 185 eV. Near threshold, our results for β lie lower than previous relativistic Dirac-Slater and nonrelativistic many-body-perturbation-theory (MBPT) calculations. The agreement with very recent measurements by Heinzmann and Schönhense is very good. Our calculations show that PL(2D52-->2P32)=-0.059 and -0.058 at incident photon energies hν=40.2 and 45.6 eV, respectively. These results lie above the nonrelativistic independent-electron theory absolute maximum of -0.061 for PL, but the agreement with recent measurements lying above this maximum is still not very good. Except for this peaking of PL(2D52-->2P32) above the nonrelativistic theory maximum for 40.2Kelly. We also find that PL(2D32-->2P32)=+ 0.134 at hν=21.2 eV, in excellent agreement with the experimental value of + 0.12+/-0.04 of Caldwell and Zare.

  9. A new technique in the theory of angular distributions in atomic processes: the angular distribution of photoelectrons in single and double photoionization

    Energy Technology Data Exchange (ETDEWEB)

    Manakov, N.L.; Meremianin, A.V. [Voronezhskij Gosudarstvennyj Univ., Voronezh (Russian Federation); Marmo, S.I. [Voronezhskij Gosudarstvennyj Univ., Voronezh (Russian Federation)]|[Palermo Univ. (Italy)

    1996-07-14

    Special reduction formulae for bipolar harmonics with higher ranks of internal spherical functions are derived, which will be useful in problems involving multiple expansions in spherical functions. Together with irreducible tensor operator techniques these results provide a new and effective approach, which enables one to extract the geometrical and dynamical factors from the cross sections of atomic processes with polarized particles with an accurate account of all the polarization effects. The angular distribution of polarized electrons and the circular dichroism in photoionization of polarized atoms with an arbitrary angular momentum J{sub O} are presented in an invariant vector form. A specific circular dichroism, which is caused by the correlation of electron and atom orientations, is discussed. The angular distribution of escaping electrons in double photoionization of unpolarized atom is presented in a simple form. A convenient parametrization is proposed for describing the dependence of the photoprocess cross sections on the polarization state of the photon beam. (Author).

  10. Counterintuitive angular shifts in the photoelectron momentum distribution for atoms in strong few-cycle circularly polarized laser pulses

    DEFF Research Database (Denmark)

    Martiny, Christian; Abu-Samha, Mahmoud; Madsen, Lars Bojer

    2009-01-01

    We solve the three-dimensional time-dependent Schrödinger equation for a three-cycle circularly polarized laser pulse interacting with an atom. The photoelectron momentum distributions show counterintuitive shifts, similar to those observed in a recent experiment (Eckle et al 2008 Science 322 1525...

  11. Valence and inner-valence shell dissociative photoionization of CO in the 26-33 eV range. II. Molecular-frame and recoil-frame photoelectron angular distributions

    DEFF Research Database (Denmark)

    Lebech, M.; Houver, J.C.; Raseev, G.

    2012-01-01

    Experimental and theoretical results for molecular-frame photoemission are presented for inner-valence shell photoionization of the CO molecule induced by linearly and circularly polarized light. The experimental recoil frame photoelectron angular distributions (RFPADs) obtained from dissociative...... for the case of general elliptically polarized light, to obtain the RFPAD rather than the molecular frame photoelectron angular distribution (MFPAD), which would be obtained with the assumption of instantaneous dissociation. We have considered photoionization of CO for the photon energies of 26.0 eV, 29.5 e......V, and 32.5 eV. A comparison of experimental and theoretical RFPADs allows us to identify the ionic states detected in the experimental studies. In addition to previously identified states, we found evidence for the 2 (2)Delta state with an ionization potential of 25.3 eV and (2)Sigma(+) states...

  12. A pulsed, mono-energetic and angular-selective UV photo-electron source for the commissioning of the KATRIN experiment

    Science.gov (United States)

    Behrens, J.; Ranitzsch, P. C.-O.; Beck, M.; Beglarian, A.; Erhard, M.; Groh, S.; Hannen, V.; Kraus, M.; Ortjohann, H.-W.; Rest, O.; Schlösser, K.; Thümmler, T.; Valerius, K.; Wierman, K.; Wilkerson, J. F.; Winzen, D.; Zacher, M.; Weinheimer, C.

    2017-06-01

    The KATRIN experiment aims to determine the neutrino mass scale with a sensitivity of 200 {meV/c^2} (90% C. L.) by a precision measurement of the shape of the tritium β -spectrum in the endpoint region. The energy analysis of the decay electrons is achieved by a MAC-E filter spectrometer. To determine the transmission properties of the KATRIN main spectrometer, a mono-energetic and angular-selective electron source has been developed. In preparation for the second commissioning phase of the main spectrometer, a measurement phase was carried out at the KATRIN monitor spectrometer where the device was operated in a MAC-E filter setup for testing. The results of these measurements are compared with simulations using the particle-tracking software "Kassiopeia", which was developed in the KATRIN collaboration over recent years.

  13. Detectors for Energy-Resolved Fast Neutron Imaging

    OpenAIRE

    Dangendorf, V.; Breskin, A.; Chechik, R.; Feldman, G.; Goldberg, M. B.; Jagutzki, O.; Kersten, C.; Laczko, G.; Mor, I.; Spillman, U.; Vartsky, D.

    2004-01-01

    Two detectors for energy-resolved fast-neutron imaging in pulsed broad-energy neutron beams are presented. The first one is a neutron-counting detector based on a solid neutron converter coupled to a gaseous electron multiplier (GEM). The second is an integrating imaging technique, based on a scintillator for neutron conversion and an optical imaging system with fast framing capability.

  14. Photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Shirley, D.A.

    1976-01-01

    Research activities in photoelectron spectroscopy at Lawrence Radiation Laboratory during 1976 are described. Topics covered include: the orientation of CO on Pt(III) and Ni(III) surfaces from angle-resolved photoemission; photoemission from CO on Pt(III) in the range 40 eV less than or equal to dirac constant ω less than or equal to 150 eV; photoemission studies of electron states at clean surfaces using synchrotron radiation; angle and energy dependent photoemission studies of plasmon loss structure in Al and In; d-orbital directed photoemission from copper; interpretation of angle-resolved x-ray photoemission from valence bands; atomic cross-section effects in soft x-ray photoemission from Ag, Au, and Pt valence bands; x-ray photoelectron spectroscopic studies of the electronic structure of transition metal difluorides; x-ray photoemission investigation of the density of states of B'-NiAl; the electronic structure of SrTiO 3 and some simple related oxides; fluorescence lifetime measurements of np 5 (n+1)S' states in krypton and xenon; Zeeman beats in the resonance fluorescence of the 3P 1 , states in krypton and xenon; lifetime measurements of rare-gas dimers; configuration interaction effects in the atomic photoelectron spectra of Ba, Sm, Eu, and Yb; glow discharge lamps as electron sources for electron impact excitation; electron impact excitation of electron correlation states in Ca, Sr, and Ba; photoelectron spectroscopy of atomic and molecular bismuth; relativistic effects in the uv photoelectron spectra of group VI diatomic molecules; and relative gas-phase acidities and basicities from a proton potential model

  15. Photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Bosch, A.

    1982-01-01

    In this work examples of the various aspects of photoelectron spectroscopy are given. The investigation was started with the development of an angle-resolved spectrometer so that the first chapters deal with angle-resolved ultra-violet photoelectron spectroscopy. To indicate the possibilities and pitfalls of the technique, in chapter II the theory is briefly reviewed. In chapter III the instrument is described. The system is based on the cylindrical mirror deflection analyzer, which is modified and improved for angle-resolved photoelectron spectroscopy. In combination with a position sensitive detector, a spectrometer is developed with which simultaneously several angle-resolved spectra can be recorded. In chapter IV, the results are reported of angle-integrated UPS experiments on dilute alloys. Using the improved energy resolution of the instrument the author was able to study the impurity states more accurately and shows that the photoemission technique has become an important tool in the study of impurities and the interactions involved. XPS and Auger results obtained from dilute alloys are presented in chapter V. It is shown that these systems are especially suited for the study of correlation effects and can provide interesting problems related to the satellite structure and the interaction of the impurity with the host. In chapter VI, the valence bands of ternary alloys are studied with UPS and compared to recent band structure calculation. The core level shifts are analyzed in a simple, thermodynamic scheme. (Auth.)

  16. Computed tomography with energy-resolved detection: a feasibility study

    Science.gov (United States)

    Shikhaliev, Polad M.

    2008-03-01

    The feasibility of computed tomography (CT) with energy-resolved x-ray detection has been investigated. A breast CT design with multi slit multi slice (MSMS) data acquisition was used for this study. The MSMS CT includes linear arrays of photon counting detectors separated by gaps. This CT configuration allows for efficient scatter rejection and 3D data acquisition. The energy-resolved CT images were simulated using a digital breast phantom and the design parameters of the proposed MSMS CT. The phantom had 14 cm diameter and 50/50 adipose/glandular composition, and included carcinoma, adipose, blood, iodine and CaCO3 as contrast elements. The x-ray technique was 90 kVp tube voltage with 660 mR skin exposure. Photon counting, charge (energy) integrating and photon energy weighting CT images were generated. The contrast-to-noise (CNR) improvement with photon energy weighting was quantified. The dual energy subtracted images of CaCO3 and iodine were generated using a single CT scan at a fixed x-ray tube voltage. The x-ray spectrum was electronically split into low- and high-energy parts by a photon counting detector. The CNR of the energy weighting CT images of carcinoma, blood, adipose, iodine, and CaCO3 was higher by a factor of 1.16, 1.20, 1.21, 1.36 and 1.35, respectively, as compared to CT with a conventional charge (energy) integrating detector. Photon energy weighting was applied to CT projections prior to dual energy subtraction and reconstruction. Photon energy weighting improved the CNR in dual energy subtracted CT images of CaCO3 and iodine by a factor of 1.35 and 1.33, respectively. The combination of CNR improvements due to scatter rejection and energy weighting was in the range of 1.71-2 depending on the type of the contrast element. The tilted angle CZT detector was considered as the detector of choice. Experiments were performed to test the effect of the tilting angle on the energy spectrum. Using the CZT detector with 20° tilting angle decreased the

  17. Near threshold studies of photoelectron satellites

    International Nuclear Information System (INIS)

    Heimann, P.A.

    1986-11-01

    Photoelectron spectroscopy and synchrotron radiation have been used to study correlation effects in the rare gases: He, Ne, Ar, Kr, and Xe. Two kinds of time-of-flight electron analyzers were employed to examine photoionization very close to threshold and at higher kinetic energies. Partial cross sections and angular distributions have been measured for a number of photoelectron satellites. The shake-off probability has been determined at some inner-shell resonances. 121 refs., 28 figs., 13 tabs

  18. Optimal ''image-based'' weighting for energy-resolved CT

    International Nuclear Information System (INIS)

    Schmidt, Taly Gilat

    2009-01-01

    This paper investigates a method of reconstructing images from energy-resolved CT data with negligible beam-hardening artifacts and improved contrast-to-nosie ratio (CNR) compared to conventional energy-weighting methods. Conceptually, the investigated method first reconstructs separate images from each energy bin. The final image is a linear combination of the energy-bin images, with the weights chosen to maximize the CNR in the final image. The optimal weight of a particular energy-bin image is derived to be proportional to the contrast-to-noise-variance ratio in that image. The investigated weighting method is referred to as ''image-based'' weighting, although, as will be described, the weights can be calculated and the energy-bin data combined prior to reconstruction. The performance of optimal image-based energy weighting with respect to CNR and beam-hardening artifacts was investigated through simulations and compared to that of energy integrating, photon counting, and previously studied optimal ''projection-based'' energy weighting. Two acquisitions were simulated: dedicated breast CT and a conventional thorax scan. The energy-resolving detector was simulated with five energy bins. Four methods of estimating the optimal weights were investigated, including task-specific and task-independent methods and methods that require a single reconstruction versus multiple reconstructions. Results demonstrated that optimal image-based weighting improved the CNR compared to energy-integrating weighting by factors of 1.15-1.6 depending on the task. Compared to photon-counting weighting, the CNR improvement ranged from 1.0 to 1.3. The CNR improvement factors were comparable to those of projection-based optimal energy weighting. The beam-hardening cupping artifact increased from 5.2% for energy-integrating weighting to 12.8% for optimal projection-based weighting, while optimal image-based weighting reduced the cupping to 0.6%. Overall, optimal image-based energy weighting

  19. Maximum-information photoelectron metrology

    Science.gov (United States)

    Hockett, P.; Lux, C.; Wollenhaupt, M.; Baumert, T.

    2015-07-01

    Photoelectron interferograms, manifested in photoelectron angular distributions (PADs), are high-information, coherent observables. In order to obtain the maximum information from angle-resolved photoionization experiments it is desirable to record the full, three-dimensional (3D), photoelectron momentum distribution. Here we apply tomographic reconstruction techniques to obtain such 3D distributions from multiphoton ionization of potassium atoms, and fully analyze the energy and angular content of the 3D data. The PADs obtained as a function of energy indicate good agreement with previous 2D data and detailed analysis [Hockett et al., Phys. Rev. Lett. 112, 223001 (2014), 10.1103/PhysRevLett.112.223001] concerning the main spectral features, but also indicate unexpected symmetry breaking in certain regions of momentum space, thus revealing additional continuum interferences which cannot otherwise be observed. These observations reflect the presence of additional ionization pathways and, most generally, illustrate the power of maximum-information measurements of coherent observables for quantum metrology of complex systems.

  20. Energy-resolved computed tomography: first experimental results

    International Nuclear Information System (INIS)

    Shikhaliev, Polad M

    2008-01-01

    First experimental results with energy-resolved computed tomography (CT) are reported. The contrast-to-noise ratio (CNR) in CT has been improved with x-ray energy weighting for the first time. Further, x-ray energy weighting improved the CNR in material decomposition CT when applied to CT projections prior to dual-energy subtraction. The existing CT systems use an energy (charge) integrating x-ray detector that provides a signal proportional to the energy of the x-ray photon. Thus, the x-ray photons with lower energies are scored less than those with higher energies. This underestimates contribution of lower energy photons that would provide higher contrast. The highest CNR can be achieved if the x-ray photons are scored by a factor that would increase as the x-ray energy decreases. This could be performed by detecting each x-ray photon separately and measuring its energy. The energy selective CT data could then be saved, and any weighting factor could be applied digitally to a detected x-ray photon. The CT system includes a photon counting detector with linear arrays of pixels made from cadmium zinc telluride (CZT) semiconductor. A cylindrical phantom with 10.2 cm diameter made from tissue-equivalent material was used for CT imaging. The phantom included contrast elements representing calcifications, iodine, adipose and glandular tissue. The x-ray tube voltage was 120 kVp. The energy selective CT data were acquired, and used to generate energy-weighted and material-selective CT images. The energy-weighted and material decomposition CT images were generated using a single CT scan at a fixed x-ray tube voltage. For material decomposition the x-ray spectrum was digitally spilt into low- and high-energy parts and dual-energy subtraction was applied. The x-ray energy weighting resulted in CNR improvement of calcifications and iodine by a factor of 1.40 and 1.63, respectively, as compared to conventional charge integrating CT. The x-ray energy weighting was also applied

  1. 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

  2. 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

  3. Strong eld ionization of naphthalene: angular shifts and molecular potential

    DEFF Research Database (Denmark)

    Dimitrovski, Darko; Maurer, Jochen; Christensen, Lauge

    We analyze the photoelectron momentum distributions from strong eld ionization of xed-in-space naphthalene molecules by circularly polarized laser pulses. By direct comparison between experiment and theory, we show that the angular shifts in the photoelectron momentum distributions are very...

  4. Event Centroiding Applied to Energy-Resolved Neutron Imaging at LANSCE

    Directory of Open Access Journals (Sweden)

    Nicholas P. Borges

    2018-02-01

    Full Text Available The energy-dependence of the neutron cross section provides vastly different contrast mechanisms than polychromatic neutron radiography if neutron energies can be selected for imaging applications. In recent years, energy-resolved neutron imaging (ERNI with epi-thermal neutrons, utilizing neutron absorption resonances for contrast as well as for quantitative density measurements, was pioneered at the Flight Path 5 beam line at LANSCE and continues to be refined. Here we present event centroiding, i.e., the determination of the center-of-gravity of a detection event on an imaging detector to allow sub-pixel spatial resolution and apply it to the many frames collected for energy-resolved neutron imaging at a pulsed neutron source. While event centroiding was demonstrated at thermal neutron sources, it has not been applied to energy-resolved neutron imaging, where the energy resolution requires to be preserved, and we present a quantification of the possible resolution as a function of neutron energy. For the 55 μm pixel size of the detector used for this study, we found a resolution improvement from ~80 μm to ~22 μm using pixel centroiding while fully preserving the energy resolution.

  5. Photoelectron spectrometer for high-resolution angular resolved studies

    International Nuclear Information System (INIS)

    Parr, A.C.; Southworth, S.H.; Dehmer, J.L.; Holland, D.M.P.

    1982-01-01

    We report on a new electron spectrometer system designed for use on storage-ring light sources. The system features a large (76 cm dia. x 92 cm long) triply magnetically shielded vacuum chamber and two 10.2 cm mean radius hemispherical electron-energy analyzers. One of the analyzers is fixed and the other is rotatable through about 150 0 . The chamber is pumped by a cryopump and a turbomolecular pump combination so as to enable experiments with a variety of gases under different conditions. The light detection includes both a direct beam monitor and polarization analyzer. The electron detection is accomplished with either a continuous-channel electron multiplier or with multichannel arrays used as area detectors

  6. Angular Momentum

    Science.gov (United States)

    Shakur, Asif; Sinatra, Taylor

    2013-01-01

    The gyroscope in a smartphone was employed in a physics laboratory setting to verify the conservation of angular momentum and the nonconservation of rotational kinetic energy. As is well-known, smartphones are ubiquitous on college campuses. These devices have a panoply of built-in sensors. This creates a unique opportunity for a new paradigm in…

  7. Imaging Molecular Structure through Femtosecond Photoelectron Diffraction on Aligned and Oriented Gas-Phase Molecules

    DEFF Research Database (Denmark)

    Boll, Rebecca; Rouzee, Arnaud; Adolph, Marcus

    2014-01-01

    This paper gives an account of our progress towards performing femtosecond time-resolved photoelectron diffraction on gas-phase molecules in a pump-probe setup combining optical lasers and an X-ray Free-Electron Laser. We present results of two experiments aimed at measuring photoelectron angular...

  8. Photoelectron spectroscopy and the dipole approximation

    Energy Technology Data Exchange (ETDEWEB)

    Hemmers, O.; Hansen, D.L.; Wang, H. [Univ. of Nevada, Las Vegas, NV (United States)] [and others

    1997-04-01

    Photoelectron spectroscopy is a powerful technique because it directly probes, via the measurement of photoelectron kinetic energies, orbital and band structure in valence and core levels in a wide variety of samples. The technique becomes even more powerful when it is performed in an angle-resolved mode, where photoelectrons are distinguished not only by their kinetic energy, but by their direction of emission as well. Determining the probability of electron ejection as a function of angle probes the different quantum-mechanical channels available to a photoemission process, because it is sensitive to phase differences among the channels. As a result, angle-resolved photoemission has been used successfully for many years to provide stringent tests of the understanding of basic physical processes underlying gas-phase and solid-state interactions with radiation. One mainstay in the application of angle-resolved photoelectron spectroscopy is the well-known electric-dipole approximation for photon interactions. In this simplification, all higher-order terms, such as those due to electric-quadrupole and magnetic-dipole interactions, are neglected. As the photon energy increases, however, effects beyond the dipole approximation become important. To best determine the range of validity of the dipole approximation, photoemission measurements on a simple atomic system, neon, where extra-atomic effects cannot play a role, were performed at BL 8.0. The measurements show that deviations from {open_quotes}dipole{close_quotes} expectations in angle-resolved valence photoemission are observable for photon energies down to at least 0.25 keV, and are quite significant at energies around 1 keV. From these results, it is clear that non-dipole angular-distribution effects may need to be considered in any application of angle-resolved photoelectron spectroscopy that uses x-ray photons of energies as low as a few hundred eV.

  9. Energy-resolved X-ray detectors: the future of diagnostic imaging

    OpenAIRE

    Pacella, Danilo

    2015-01-01

    Danilo Pacella ENEA-Frascati, Rome, Italy Abstract: This paper presents recent progress in the field of X-ray detectors, which could play a role in medical imaging in the near future, with special attention to the new generation of complementary metal-oxide semiconductor (C-MOS) imagers, working in photon counting, that opened the way to the energy-resolved X-ray imaging. A brief description of the detectors used so far in medical imaging (photographic films, imaging plates, flat panel detec...

  10. Anion photoelectron spectroscopy of radicals and clusters

    Energy Technology Data Exchange (ETDEWEB)

    Travis, Taylor R. [Univ. of California, Berkeley, CA (United States)

    1999-12-01

    Anion photoelectron spectroscopy is used to study free radicals and clusters. The low-lying 2Σ and 2π states of C2nH (n = 1--4) have been studied. The anion photoelectron spectra yielded electron affinities, term values, and vibrational frequencies for these combustion and astrophysically relevant species. Photoelectron angular distributions allowed the author to correctly assign the electronic symmetry of the ground and first excited states and to assess the degree of vibronic coupling in C2H and C4H. Other radicals studied include NCN and I3. The author was able to observe the low-lying singlet and triplet states of NCN for the first time. Measurement of the electron affinity of I3 revealed that it has a bound ground state and attachment of an argon atom to this moiety enabled him to resolve the symmetric stretching progression.

  11. Photoelectronic characterization of heterointerfaces.

    Energy Technology Data Exchange (ETDEWEB)

    Brumbach, Michael Todd

    2012-02-01

    In many devices such as solar cells, light emitting diodes, transistors, etc., the performance relies on the electronic structure at interfaces between materials within the device. The objective of this work was to perform robust characterization of hybrid (organic/inorganic) interfaces by tailoring the interfacial region for photoelectron spectroscopy. Self-assembled monolayers (SAM) were utilized to induce dipoles of various magnitudes at the interface. Additionally, SAMs of molecules with varying dipolar characteristics were mixed into spatially organized structures to systematically vary the apparent work function. Polymer thin films were characterized by depositing films of varying thicknesses on numerous substrates with and without interfacial modifications. Hard X-ray photoelectron spectroscopy (HAXPES) was performed to evaluate a buried interface between indium tin oxide (ITO), treated under various conditions, and poly(3-hexylthiophene) (P3HT). Conducting polymer films were found to be sufficiently conducting such that no significant charge redistribution in the polymer films was observed. Consequently, a further departure from uniform substrates was taken whereby electrically disconnected regions of the substrate presented ideally insulating interfacial contacts. In order to accomplish this novel strategy, interdigitated electrodes were used as the substrate. Conducting fingers of one half of the electrodes were electrically grounded while the other set of electrodes were electronically floating. This allowed for the evaluation of substrate charging on photoelectron spectra (SCOPES) in the presence of overlying semiconducting thin films. Such an experiment has never before been reported. This concept was developed out of the previous experiments on interfacial modification and thin film depositions and presents new opportunities for understanding chemical and electronic changes in a multitude of materials and interfaces.

  12. Atomic and molecular photoelectron and Auger-electron-spectroscopy studies using synchrotron radiation

    International Nuclear Information System (INIS)

    Southworth, S.H.

    1982-01-01

    Electron spectroscopy, combined with synchrotron radiation, was used to measure the angular distributions of photoelectrons and Auger electrons from atoms and molecules as functions of photon energy. The branching ratios and partial cross sections were also measured in certain cases. By comparison with theoretical calculations, the experimental results are interpreted in terms of the characteristic electronic structure and ionization dynamics of the atomic or molecular sample. The time structure of the synchrotron radiation source was used to record time-of-flight (TOF) spectra of the ejected electrons. The double-angle-TOF method for the measurement of photoelectron angular distributions is discussed. This technique offers the advantages of increased electron collection efficiency and the elimination of certain systematic errors. An electron spectroscopy study of inner-shell photoexcitation and ionization of Xe, photoelectron angular distributions from H 2 and D 2 , and photoionization cross sections and photoelectron asymmetries of the valence orbitals of NO are reported

  13. Femtosecond x-ray photoelectron diffraction on gas-phase dibromobenzene molecules

    International Nuclear Information System (INIS)

    Rolles, D; Boll, R; Epp, S W; Erk, B; Foucar, L; Hömke, A; Adolph, M; Gorkhover, T; Aquila, A; Chapman, H N; Coppola, N; Delmas, T; Gumprecht, L; Holmegaard, L; Bostedt, C; Bozek, J D; Coffee, R; Decleva, P; Filsinger, F; Johnsson, P

    2014-01-01

    We present time-resolved femtosecond photoelectron momentum images and angular distributions of dissociating, laser-aligned 1,4-dibromobenzene (C 6 H 4 Br 2 ) molecules measured in a near-infrared pump, soft-x-ray probe experiment performed at an x-ray free-electron laser. The observed alignment dependence of the bromine 2p photoelectron angular distributions is compared to density functional theory calculations and interpreted in terms of photoelectron diffraction. While no clear time-dependent effects are observed in the angular distribution of the Br(2p) photoelectrons, other, low-energy electrons show a pronounced dependence on the time delay between the near-infrared laser and the x-ray pulse. (paper)

  14. The Dosepix detector—an energy-resolving photon-counting pixel detector for spectrometric measurements

    CERN Document Server

    Zang, A; Ballabriga, R; Bisello, F; Campbell, M; Celi, J C; Fauler, A; Fiederle, M; Jensch, M; Kochanski, N; Llopart, X; Michel, N; Mollenhauer, U; Ritter, I; Tennert, F; Wölfel, S; Wong, W; Michel, T

    2015-01-01

    The Dosepix detector is a hybrid photon-counting pixel detector based on ideas of the Medipix and Timepix detector family. 1 mm thick cadmium telluride and 300 μm thick silicon were used as sensor material. The pixel matrix of the Dosepix consists of 16 x 16 square pixels with 12 rows of (200 μm)2 and 4 rows of (55 μm)2 sensitive area for the silicon sensor layer and 16 rows of pixels with 220 μm pixel pitch for CdTe. Besides digital energy integration and photon-counting mode, a novel concept of energy binning is included in the pixel electronics, allowing energy-resolved measurements in 16 energy bins within one acquisition. The possibilities of this detector concept range from applications in personal dosimetry and energy-resolved imaging to quality assurance of medical X-ray sources by analysis of the emitted photon spectrum. In this contribution the Dosepix detector, its response to X-rays as well as spectrum measurements with Si and CdTe sensor layer are presented. Furthermore, a first evaluation wa...

  15. Full k-space visualization of photoelectron diffraction

    International Nuclear Information System (INIS)

    Denlinger, J.D.; Rotenberg, E.; Kevan, S.D.; Tonner, B.P.

    1997-01-01

    The development of photoelectron holography has promoted the need for larger photoelectron diffraction data sets in order to improve the quality of real-space reconstructed images (by suppressing transformational artifacts and distortions). The two main experimental and theoretical approaches to holography, the transform of angular distribution patterns for a coarse selection of energies or the transform of energy-scanned profiles for several directions, represent two limits to k-space sampling. The high brightness of third-generation soft x-ray synchrotron sources provides the opportunity to rapidly measure large high-density x-ray photoelectron diffraction (XPD) data sets with approximately uniform k-space sampling. In this abstract, the authors present such a photoelectron data set acquired for Cu 3p emission from Cu(001). Cu(001) is one of the most well-studied systems for understanding photoelectron diffraction structure and for testing photoelectron holography methods. Cu(001) was chosen for this study in part due to the relatively inert and unreconstructed clean surface, and it served to calibrate and fine-tune the operation of a new synchrotron beamline, electron spectrometer and sample goniometer. In addition to Cu, similar open-quotes volumeclose quotes XPD data sets have been acquired for bulk and surface core-level emission from W(110), from reconstructed Si(100) and Si(111) surfaces, and from the adsorbate system of c(2x2) Mn/Ni(100)

  16. Full momentum- and energy-resolved spectral function of a 2D electronic system

    Science.gov (United States)

    Jang, Joonho; Yoo, Heun Mo; Pfeiffer, L. N.; West, K. W.; Baldwin, K. W.; Ashoori, Raymond C.

    2017-11-01

    The single-particle spectral function measures the density of electronic states in a material as a function of both momentum and energy, providing central insights into strongly correlated electron phenomena. Here we demonstrate a high-resolution method for measuring the full momentum- and energy-resolved electronic spectral function of a two-dimensional (2D) electronic system embedded in a semiconductor. The technique remains operational in the presence of large externally applied magnetic fields and functions even for electronic systems with zero electrical conductivity or with zero electron density. Using the technique on a prototypical 2D system, a GaAs quantum well, we uncover signatures of many-body effects involving electron-phonon interactions, plasmons, polarons, and a phonon analog of the vacuum Rabi splitting in atomic systems.

  17. Analysis of electronic models for solar cells including energy resolved defect densities

    Energy Technology Data Exchange (ETDEWEB)

    Glitzky, Annegret

    2010-07-01

    We introduce an electronic model for solar cells including energy resolved defect densities. The resulting drift-diffusion model corresponds to a generalized van Roosbroeck system with additional source terms coupled with ODEs containing space and energy as parameters for all defect densities. The system has to be considered in heterostructures and with mixed boundary conditions from device simulation. We give a weak formulation of the problem. If the boundary data and the sources are compatible with thermodynamic equilibrium the free energy along solutions decays monotonously. In other cases it may be increasing, but we estimate its growth. We establish boundedness and uniqueness results and prove the existence of a weak solution. This is done by considering a regularized problem, showing its solvability and the boundedness of its solutions independent of the regularization level. (orig.)

  18. Investigation of dissimilar metal welds by energy-resolved neutron imaging.

    Science.gov (United States)

    Tremsin, Anton S; Ganguly, Supriyo; Meco, Sonia M; Pardal, Goncalo R; Shinohara, Takenao; Feller, W Bruce

    2016-08-01

    A nondestructive study of the internal structure and compositional gradient of dissimilar metal-alloy welds through energy-resolved neutron imaging is described in this paper. The ability of neutrons to penetrate thick metal objects (up to several cm) provides a unique possibility to examine samples which are opaque to other conventional techniques. The presence of Bragg edges in the measured neutron transmission spectra can be used to characterize the internal residual strain within the samples and some microstructural features, e.g. texture within the grains, while neutron resonance absorption provides the possibility to map the degree of uniformity in mixing of the participating alloys and intermetallic formation within the welds. In addition, voids and other defects can be revealed by the variation of neutron attenuation across the samples. This paper demonstrates the potential of neutron energy-resolved imaging to measure all these characteristics simultaneously in a single experiment with sub-mm spatial resolution. Two dissimilar alloy welds are used in this study: Al autogenously laser welded to steel, and Ti gas metal arc welded (GMAW) to stainless steel using Cu as a filler alloy. The cold metal transfer variant of the GMAW process was used in joining the Ti to the stainless steel in order to minimize the heat input. The distributions of the lattice parameter and texture variation in these welds as well as the presence of voids and defects in the melt region are mapped across the welds. The depth of the thermal front in the Al-steel weld is clearly resolved and could be used to optimize the welding process. A highly textured structure is revealed in the Ti to stainless steel joint where copper was used as a filler wire. The limited diffusion of Ti into the weld region is also verified by the resonance absorption.

  19. Energy-resolved X-ray imaging: Material decomposition methods adapted for spectrometric detectors

    International Nuclear Information System (INIS)

    Potop, Alexandra-Iulia

    2014-01-01

    Scintillator based integrating detectors are used in conventional X-ray imaging systems. The new generation of energy-resolved semiconductor radiation detectors, based on CdTe/CdZnTe, allows counting the number of photons incident on the detector and measure their energy. The LDET laboratory developed pixelated spectrometric detectors for X-ray imaging, associated with a fast readout circuit, which allows working with high fluxes and while maintaining a good energy resolution. With this thesis, we bring our contribution to data processing acquired in radiographic and tomographic modes for material components quantification. Osteodensitometry was chosen as a medical application. Radiographic data was acquired by simulation with a detector which presents imperfections as charge sharing and pile-up. The methods chosen for data processing are based on a material decomposition approach. Basis material decomposition models the linear attenuation coefficient of a material as a linear combination of the attenuations of two basis materials based on the energy related information acquired in each energy bin. Two approaches based on a calibration step were adapted for our application. The first is the polynomial approach used for standard dual energy acquisitions, which was applied for two and three energies acquired with the energy-resolved detector. We searched the optimal configuration of bins. We evaluated the limits of the polynomial approach with a study on the number of channels. To go further and take benefit of the elevated number of bins acquired with the detectors developed in our laboratory, a statistical approach implemented in our laboratory was adapted for the material decomposition method for quantifying mineral content in bone. The two approaches were compared using figures of merit as bias and noise over the lengths of the materials traversed by X-rays. An experimental radiographic validation of the two approaches was done in our laboratory with a

  20. Energy-resolved X-ray detectors: the future of diagnostic imaging

    Directory of Open Access Journals (Sweden)

    Pacella D

    2015-01-01

    Full Text Available Danilo Pacella ENEA-Frascati, Rome, Italy Abstract: This paper presents recent progress in the field of X-ray detectors, which could play a role in medical imaging in the near future, with special attention to the new generation of complementary metal-oxide semiconductor (C-MOS imagers, working in photon counting, that opened the way to the energy-resolved X-ray imaging. A brief description of the detectors used so far in medical imaging (photographic films, imaging plates, flat panel detectors, together with the most relevant imaging quality parameters, shows differences between, and advantages of these new C-MOS imagers. X-ray energy-resolved imaging is very attractive not only for the increase of contrast but even for the capability of detecting the nature and composition of the material or tissue to be investigated. Since the X-ray absorption coefficients of the different parts or organs of the patient (object are strongly dependent on the X-ray photon energy, this multienergy ("colored" X-ray imaging could increase enormously the probing capabilities. While dual-energy imaging is now a reality in medical practice, multienergy is still in its early stage, but a promising research activity. Based on this new technique of color X-ray imaging, the entire scheme of source–object–detector could be revised in the future, optimizing spectrum and detector to the nature and composition of the target to be investigated. In this view, a transition to a set of monoenergetic X-ray lines, suitably chosen in energy and intensity, could be envisaged, instead of the present continuous spectra. Keywords: X-ray detectors, X-ray medical imaging, C-MOS imagers, dual and multienergy CT

  1. Non-destructive Depth Profiling of the Activated Ti-Zr-V Getter by Means of Excitation Energy Resolved Photoelectron Spectroscopy

    Czech Academy of Sciences Publication Activity Database

    Pavluch, J.; Zommer, L.; Mašek, K.; Skála, T.; Šutara, F.; Nehasil, V.; Píš, I.; Polyak, Yaroslav

    2010-01-01

    Roč. 26, č. 2 (2010), s. 209-215 ISSN 0910-6340 Institutional research plan: CEZ:AV0Z40400503 Keywords : non-evaporable getter materials * XPS methods Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.465, year: 2010

  2. X-ray photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Attekum, P.M.T.M. van.

    1979-01-01

    The methods and results of X-ray photoelectron spectroscopy in the study of plasmons, alloys and gold compounds are discussed. After a comprehensive introduction, seven papers by the author, previously published elsewhere, are reprinted and these cover a wide range of the uses of X-ray photoelectron spectroscopy. (W.D.L.)

  3. Optimal ''image-based'' weighting for energy-resolved CT

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt, Taly Gilat [Department of Biomedical Engineering, Marquette University, Milwaukee, Wisconsin 53201 (United States)

    2009-07-15

    This paper investigates a method of reconstructing images from energy-resolved CT data with negligible beam-hardening artifacts and improved contrast-to-nosie ratio (CNR) compared to conventional energy-weighting methods. Conceptually, the investigated method first reconstructs separate images from each energy bin. The final image is a linear combination of the energy-bin images, with the weights chosen to maximize the CNR in the final image. The optimal weight of a particular energy-bin image is derived to be proportional to the contrast-to-noise-variance ratio in that image. The investigated weighting method is referred to as ''image-based'' weighting, although, as will be described, the weights can be calculated and the energy-bin data combined prior to reconstruction. The performance of optimal image-based energy weighting with respect to CNR and beam-hardening artifacts was investigated through simulations and compared to that of energy integrating, photon counting, and previously studied optimal ''projection-based'' energy weighting. Two acquisitions were simulated: dedicated breast CT and a conventional thorax scan. The energy-resolving detector was simulated with five energy bins. Four methods of estimating the optimal weights were investigated, including task-specific and task-independent methods and methods that require a single reconstruction versus multiple reconstructions. Results demonstrated that optimal image-based weighting improved the CNR compared to energy-integrating weighting by factors of 1.15-1.6 depending on the task. Compared to photon-counting weighting, the CNR improvement ranged from 1.0 to 1.3. The CNR improvement factors were comparable to those of projection-based optimal energy weighting. The beam-hardening cupping artifact increased from 5.2% for energy-integrating weighting to 12.8% for optimal projection-based weighting, while optimal image-based weighting reduced the cupping to 0

  4. Stereo photograph of atomic arrangement by circularly-polarized-light two-dimensional photoelectron spectroscopy

    CERN Document Server

    Daimon, H

    2003-01-01

    A stereo photograph of atomic arrangement was obtained for the first time. The stereo photograph was displayed directly on the screen of display-type spherical-mirror analyzer without any computer-aided conversion process. This stereo photography was realized taking advantage of the phenomenon of circular dichroism in photoelectron angular distribution due to the reversal of orbital angular momentum of photoelectrons. The azimuthal shifts of forward focusing peaks in a photoelectron angular distribution pattern taken with left and right helicity light in a special arrangement are the same as the parallaxes in a stereo view of atoms. Hence a stereoscopic recognition of three-dimensional atomic arrangement is possible, when the left eye and the right eye respectively view the two images obtained by left and right helicity light simultaneously.

  5. ERICA: an energy resolving photon counting readout ASIC for X-ray in-line cameras

    Science.gov (United States)

    Macias-Montero, J.-G.; Sarraj, M.; Chmeissani, M.; Moore, T.; Casanova, R.; Martinez, R.; Puigdengoles, C.; Prats, X.; Kolstein, M.

    2016-12-01

    We present ERICA (Energy Resolving Inline X-ray Camera) a photon-counting readout ASIC, with 6 energy bins. The ASIC is composed of a matrix of 8 × 20 pixels controlled by a global digital controller and biased with 7 independent digital to analog converters (DACs) and a band-gap current reference. The pixel analog front-end includes a charge sensitive amplifier with 16 mV/ke- gain and dynamic range of 45 ke-. ERICA has programmable pulse width, an adjustable constant current feedback resistor, a linear test pulse generator, and six discriminators with 6-bit local threshold adjustment. The pixel digital back-end includes the digital controller, 8 counters of 8-bit depth, half-full buffer flag for any of the 8 counters, a 74-bit shadow/shift register, a 74-bit configuration latch, and charge sharing compensation processing to perform the energy classification and counting operations of every detected photon in 1 μ s. The pixel size is 330 μm × 330 μm and its average consumption is 150 μW. Implemented in TSMC 0.25 μm CMOS process, the ASIC pixel's equivalent noise charge (ENC) is 90 e- RMS connected to a 1 mm thickness matching CdTe detector biased at -300 V with a total leakage current of 20 nA.

  6. Energy-resolved X-ray radiography with controlled-drift detectors at Sincrotrone Trieste

    Energy Technology Data Exchange (ETDEWEB)

    Castoldi, A. E-mail: andrea.castoldi@polimi.it; Galimberti, A.; Guazzoni, C.; Rehak, P.; Strueder, L.; Menk, R.H

    2003-09-01

    The Controlled-Drift Detector (CDD) is a fully depleted silicon detector that allows 2-D position sensing and energy spectroscopy of X-rays in the range 1-20 keV with excellent time resolution. Its distinctive feature is the simultaneous readout of the charge packets stored in the detector by means of a uniform electrostatic field leading to readout times of few microseconds. The advantage of this readout mechanism is twofold: (i) a higher frame rate/better time resolution with respect to the charge-coupled device which represents the reference X-ray spectroscopic imager and (ii) a lower contribution of the thermal noise due to a shorter integration time, leading to an excellent energy resolution also at room temperature. In this work we present the first experimental characterization of the CDD with synchrotron light in the range 8-30 keV carried out at Sincrotrone Trieste. Two-dimensional energy-resolved radiographic images carried out at a frame frequency up to 100 kHz are shown. Application of the CDD to elemental absorption contrast imaging is also presented.

  7. Novel energy resolving x-ray pinhole camera on Alcator C-Moda)

    Science.gov (United States)

    Pablant, N. A.; Delgado-Aparicio, L.; Bitter, M.; Brandstetter, S.; Eikenberry, E.; Ellis, R.; Hill, K. W.; Hofer, P.; Schneebeli, M.

    2012-10-01

    A new energy resolving x-ray pinhole camera has been recently installed on Alcator C-Mod. This diagnostic is capable of 1D or 2D imaging with a spatial resolution of ≈1 cm, an energy resolution of ≈1 keV in the range of 3.5-15 keV and a maximum time resolution of 5 ms. A novel use of a Pilatus 2 hybrid-pixel x-ray detector [P. Kraft et al., J. Synchrotron Rad. 16, 368 (2009), 10.1107/S0909049509009911] is employed in which the lower energy threshold of individual pixels is adjusted, allowing regions of a single detector to be sensitive to different x-ray energy ranges. Development of this new detector calibration technique was done as a collaboration between PPPL and Dectris Ltd. The calibration procedure is described, and the energy resolution of the detector is characterized. Initial data from this installation on Alcator C-Mod is presented. This diagnostic provides line-integrated measurements of impurity emission which can be used to determine impurity concentrations as well as the electron energy distribution.

  8. Photoelectron spectroscopy principles and applications

    CERN Document Server

    Hüfner, Stefan

    1995-01-01

    Photoelectron Spectroscopy presents an up-to-date introduction to the field by treating comprehensively the electronic structures of atoms, molecules, solids and surfaces Brief descriptions are given of inverse photoemission, spin-polarized photoemission and photoelectron diffraction Experimental aspects are considered throughout the book, and the results are carefully interpreted by theory A wealth of measured data is presented in the form of tables for easy use by experimentalists

  9. Subcycle interference dynamics of time-resolved photoelectron holography with midinfrared laser pulses

    International Nuclear Information System (INIS)

    Bian Xuebin; Yuan, Kai-Jun; Bandrauk, Andre D.; Huismans, Y.; Smirnova, O.; Vrakking, M. J. J.

    2011-01-01

    Time-resolved photoelectron holography from atoms using midinfrared laser pulses is investigated by solving the corresponding time-dependent Schroedinger equation (TDSE) and a classical model, respectively. The numerical simulation of the photoelectron angular distribution of Xe irradiated with a low-frequency free-electron laser source agrees well with the experimental results. Different types of subcycle interferometric structures are predicted by the classical model. Furthermore with the TDSE model it is demonstrated that the holographic pattern is sensitive to the shape of the atomic orbitals. This is a step toward imaging by means of photoelectron holography.

  10. Quantitative material decomposition using spectral computed tomography with an energy-resolved photon-counting detector

    International Nuclear Information System (INIS)

    Lee, Seungwan; Choi, Yu-Na; Kim, Hee-Joung

    2014-01-01

    Dual-energy computed tomography (CT) techniques have been used to decompose materials and characterize tissues according to their physical and chemical compositions. However, these techniques are hampered by the limitations of conventional x-ray detectors operated in charge integrating mode. Energy-resolved photon-counting detectors provide spectral information from polychromatic x-rays using multiple energy thresholds. These detectors allow simultaneous acquisition of data in different energy ranges without spectral overlap, resulting in more efficient material decomposition and quantification for dual-energy CT. In this study, a pre-reconstruction dual-energy CT technique based on volume conservation was proposed for three-material decomposition. The technique was combined with iterative reconstruction algorithms by using a ray-driven projector in order to improve the quality of decomposition images and reduce radiation dose. A spectral CT system equipped with a CZT-based photon-counting detector was used to implement the proposed dual-energy CT technique. We obtained dual-energy images of calibration and three-material phantoms consisting of low atomic number materials from the optimal energy bins determined by Monte Carlo simulations. The material decomposition process was accomplished by both the proposed and post-reconstruction dual-energy CT techniques. Linear regression and normalized root-mean-square error (NRMSE) analyses were performed to evaluate the quantitative accuracy of decomposition images. The calibration accuracy of the proposed dual-energy CT technique was higher than that of the post-reconstruction dual-energy CT technique, with fitted slopes of 0.97–1.01 and NRMSEs of 0.20–4.50% for all basis materials. In the three-material phantom study, the proposed dual-energy CT technique decreased the NRMSEs of measured volume fractions by factors of 0.17–0.28 compared to the post-reconstruction dual-energy CT technique. It was concluded that the

  11. Recent trends in spin-resolved photoelectron spectroscopy

    Science.gov (United States)

    Okuda, Taichi

    2017-12-01

    Since the discovery of the Rashba effect on crystal surfaces and also the discovery of topological insulators, spin- and angle-resolved photoelectron spectroscopy (SARPES) has become more and more important, as the technique can measure directly the electronic band structure of materials with spin resolution. In the same way that the discovery of high-Tc superconductors promoted the development of high-resolution angle-resolved photoelectron spectroscopy, the discovery of this new class of materials has stimulated the development of new SARPES apparatus with new functions and higher resolution, such as spin vector analysis, ten times higher energy and angular resolution than conventional SARPES, multichannel spin detection, and so on. In addition, the utilization of vacuum ultra violet lasers also opens a pathway to the realization of novel SARPES measurements. In this review, such recent trends in SARPES techniques and measurements will be overviewed.

  12. Angular Accelerating White Light

    CSIR Research Space (South Africa)

    Dudley, Angela L

    2015-08-01

    Full Text Available angular acceleration during propagation which is achieved by superpositions of Bessel beams with non-canonical phase functions. They demonstrate these angular accelerating fields by modulating the phase and amplitude of a supercontinuum source with the use...

  13. Professional AngularJS

    CERN Document Server

    Karpov, Valeri

    2015-01-01

    A comprehensive guide to AngularJS, Google's open-source client-side framework for app development. Most of the existing guides to AngularJS struggle to provide simple and understandable explanations for more advanced concepts. As a result, some developers who understand all the basic concepts of AngularJS struggle when it comes to building more complex real-world applications. Professional AngularJS provides a thorough understanding of AngularJS, covering everything from basic concepts, such as directives and data binding, to more advanced concepts like transclusion, build systems, and auto

  14. Synchrotron-based photoelectron microscopy

    International Nuclear Information System (INIS)

    Barinov, Alexei; Dudin, Pavel; Gregoratti, Luca; Locatelli, Andrea; Onur Mentes, Tevfik; Angel Nino, Miquel; Kiskinova, Maya

    2009-01-01

    The paper is a brief overview of the operation principles and the potentials of the scanning photoelectron microscopes (SPEM) and X-ray photoemission electron microscopes (XPEEM) operating at synchrotron facilities. Selected results will illustrate the impact of high spatial resolution for micro-characterization of the surface composition and electronic structure, a key issue for analysis of technologically relevant materials and for fundamental understanding of many unexplored surface phenomena.

  15. Time relative single-photon (photoelectron) method

    International Nuclear Information System (INIS)

    Luo Binqiao

    1988-01-01

    A single-photon (photoelectron) measuring system is designed. It researches various problems in single-photon (photoelectron) method. The electronic resolving time is less than 25 ps. The resolving time of single-photon (photoelectron) measuring system is 25 to 65 ps

  16. Angular correlation methods

    International Nuclear Information System (INIS)

    Ferguson, A.J.

    1974-01-01

    An outline of the theory of angular correlations is presented, and the difference between the modern density matrix method and the traditional wave function method is stressed. Comments are offered on particular angular correlation theoretical techniques. A brief discussion is given of recent studies of gamma ray angular correlations of reaction products recoiling with high velocity into vacuum. Two methods for optimization to obtain the most accurate expansion coefficients of the correlation are discussed. (1 figure, 53 references) (U.S.)

  17. Angle-resolved photoelectron cross section of CF4

    International Nuclear Information System (INIS)

    Carlson, T.A.; Fahlman, A.; Svensson, W.A.; Krause, M.O.; Whitley, T.A.; Grimm, F.A.; Piancastelli, M.N.; Taylor, J.W.

    1984-01-01

    Partial photoelectron cross sections sigma and angular distribution parameters β were obtained for the first five valence orbitals in CF 4 : 1t 1 , 4t 2 , 1e, 3t 2 , and 4a 1 , as a function of photon energy from 17 to 70 eV. These data were taken with the aid of angle-resolved photoelectron spectroscopy and synchrotron radiation. The results were compared with earlier data on CCl 4 . Substantial differences were found. These are explained partly in terms of the absence of a Cooper minimum with a fluorine compound as opposed to the presence of a Cooper minimum with chlorine compounds and partly in terms of the position of shape resonances. Data on CF 4 were also compared with recent calculations of Stephens et al., who used the multiple-scattering Xα method. Structure in the photoelectron spectrum of CF 4 lying on the low energy side of the third band was identified as due to autoionization and evidence is given as to its specific nature

  18. Strong Circular Dichroism in Photoelectron Diffraction from Nonchiral, Nonmagnetic Material—Direct Observation of Rotational Motion of Electrons

    Science.gov (United States)

    Daimon, Hiroshi; Nakatani, Takeshi; Imada, Shin; Suga, Shigemasa; Kagoshima, Yasushi; Miyahara, Tsuneaki

    1993-10-01

    Strong circular dichroism is found in 2-dimensional angular distribution patterns of the Si 2p photoelectrons from the Si(001) surface, which has no chirality and magnetism. The forward focusing peaks in the pattern rotate clockwise or counterclockwise when the helicity of the incident circularly polarized light is reversed. These rotations of the pattern are explained by rotational motion of photoelectrons around the nuclei. This is the first direct observation of the rotational motion of the electrons and clarifies the correspondence between the classical and the quantum mechanical ideas of angular momentum.

  19. Angular Acceleration without Torque?

    Science.gov (United States)

    Kaufman, Richard D.

    2012-01-01

    Hardly. Just as Robert Johns qualitatively describes angular acceleration by an internal force in his article "Acceleration Without Force?" here we will extend the discussion to consider angular acceleration by an internal torque. As we will see, this internal torque is due to an internal force acting at a distance from an instantaneous center.

  20. Rotations and angular momentum

    International Nuclear Information System (INIS)

    Nyborg, P.; Froyland, J.

    1979-01-01

    This paper is devoted to the analysis of rotational invariance and the properties of angular momentum in quantum mechanics. In particular, the problem of addition of angular momenta is treated in detail, and tables of Clebsch-Gordan coefficients are included

  1. Imaging photoelectron circular dichroism of chiral molecules by femtosecond multiphoton coincidence detection

    Energy Technology Data Exchange (ETDEWEB)

    Lehmann, C. Stefan; Ram, N. Bhargava; Janssen, Maurice H. M., E-mail: m.h.m.janssen@vu.nl [LaserLaB Amsterdam, VU University Amsterdam, De Boelelaan 1081, 1081 HV Amsterdam (Netherlands); Powis, Ivan [School of Chemistry, University of Nottingham, Nottingham NG7 2RD (United Kingdom)

    2013-12-21

    Here, we provide a detailed account of novel experiments employing electron-ion coincidence imaging to discriminate chiral molecules. The full three-dimensional angular scattering distribution of electrons is measured after photoexcitation with either left or right circular polarized light. The experiment is performed using a simplified photoelectron-photoion coincidence imaging setup employing only a single particle imaging detector. Results are reported applying this technique to enantiomers of the chiral molecule camphor after three-photon ionization by circularly polarized femtosecond laser pulses at 400 nm and 380 nm. The electron-ion coincidence imaging provides the photoelectron spectrum of mass-selected ions that are observed in the time-of-flight mass spectra. The coincident photoelectron spectra of the parent camphor ion and the various fragment ions are the same, so it can be concluded that fragmentation of camphor happens after ionization. We discuss the forward-backward asymmetry in the photoelectron angular distribution which is expressed in Legendre polynomials with moments up to order six. Furthermore, we present a method, similar to one-photon electron circular dichroism, to quantify the strength of the chiral electron asymmetry in a single parameter. The circular dichroism in the photoelectron angular distribution of camphor is measured to be 8% at 400 nm. The electron circular dichroism using femtosecond multiphoton excitation is of opposite sign and about 60% larger than the electron dichroism observed before in near-threshold one-photon ionization with synchrotron excitation. We interpret our multiphoton ionization as being resonant at the two-photon level with the 3s and 3p Rydberg states of camphor. Theoretical calculations are presented that model the photoelectron angular distribution from a prealigned camphor molecule using density functional theory and continuum multiple scattering X alpha photoelectron scattering calculations

  2. Near gap excitation of a CDW amplitude mode by time-resolved photoelectron spectroscopy

    Science.gov (United States)

    Leuenberger, Dominik; Yang, Shuolong; Sobota, Jonathan; Giraldo, Paula; Kirchmann, Patrick; Fisher, Ian; Shen, Zhi-Xun

    2014-03-01

    We present time-, angle- and energy-resolved photoelectron spectroscopy data from the light rear-earth tritelluride compound CeTe3. An in-plane Peierls distortion in the tellurium slabs leads to the formation of an incommensurate Charge Density Wave (CDW), accompanied by a CDW gap at the Fermi level. Ultrafast optical laser excitation and subsequent relaxation by means of electron-phonon coupling can coherently excite a periodic modulation of the CDW band position and the gap size in rear-earth tritellurides. In this work, the use of tuneable near infrared laser pulses allows for optical excitation slightly above and below the measured gap value of 570 meV. The smaller excitation phase space not only leads to cleaner amplitude mode signal but also helps to pin down the optical transitions, which are the driving mechanisms for the transient CDW phase transition. Financial support by the Swiss National Science Foundation is duly acknowledged.

  3. Femtosecond photoelectron point projection microscope

    International Nuclear Information System (INIS)

    Quinonez, Erik; Handali, Jonathan; Barwick, Brett

    2013-01-01

    By utilizing a nanometer ultrafast electron source in a point projection microscope we demonstrate that images of nanoparticles with spatial resolutions of the order of 100 nanometers can be obtained. The duration of the emission process of the photoemitted electrons used to make images is shown to be of the order of 100 fs using an autocorrelation technique. The compact geometry of this photoelectron point projection microscope does not preclude its use as a simple ultrafast electron microscope, and we use simple analytic models to estimate temporal resolutions that can be expected when using it as a pump-probe ultrafast electron microscope. These models show a significant increase in temporal resolution when comparing to ultrafast electron microscopes based on conventional designs. We also model the microscopes spectroscopic abilities to capture ultrafast phenomena such as the photon induced near field effect

  4. Materials characterization by photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Nascente, P.A.P.

    2010-01-01

    Low energy electrons are suitable for investigating surfaces due to their low mean free path in solids, which correspond to a few atomic layers (0.5 to 3.0 nm), and could be used in one of the following ways: incident electrons cause the emission of backscattered and secondary electrons and the electrons are excited by irradiated photons. The first case includes the emission of Auger electrons, while photoemission corresponds to the second case. X-ray photoelectron spectroscopy (XPS) is one of the most used surface analysis techniques since it is able to identify not only the surface constituents but also their chemical states. XPS can be employed in several areas of science and engineering, but in this report it will be presented only few examples of its use in the characterization of metallic materials, with an emphasis on thin films of noble and transition metals. (author)

  5. Quark Orbital Angular Momentum

    Directory of Open Access Journals (Sweden)

    Burkardt Matthias

    2015-01-01

    Full Text Available Definitions of orbital angular momentum based on Wigner distributions are used as a framework to discuss the connection between the Ji definition of the quark orbital angular momentum and that of Jaffe and Manohar. We find that the difference between these two definitions can be interpreted as the change in the quark orbital angular momentum as it leaves the target in a DIS experiment. The mechanism responsible for that change is similar to the mechanism that causes transverse single-spin asymmetries in semi-inclusive deep-inelastic scattering.

  6. Optical Angular Momentum

    International Nuclear Information System (INIS)

    Arimondo, Ennio

    2004-01-01

    For many years the Institute of Physics has published books on hot topics based on a collection of reprints from different journals, including some remarks by the editors of each volume. The book on Optical Angular Momentum, edited by L Allen, S M Barnett and M J Padgett, is a recent addition to the series. It reproduces forty four papers originally published in different journals and in a few cases it provides direct access to works not easily accessible to a web navigator. The collection covers nearly a hundred years of progress in physics, starting from an historic 1909 paper by Poynting, and ending with a 2002 paper by Padgett, Barnett and coworkers on the measurement of the orbital angular momentum of a single photon. The field of optical angular momentum has expanded greatly, creating an interdisciplinary attraction for researchers operating in quantum optics, atomic physics, solid state physics, biophysics and quantum information theory. The development of laser optics, especially the control of single mode sources, has made possible the specific design of optical radiation modes with a high degree of control on the light angular momentum. The editors of this book are important figures in the field of angular momentum, having contributed to key progress in the area. L Allen published an historical paper in 1999, he and M J Padgett (together with M Babiker) produced few years ago a long review article which is today still the most complete basic introduction to the angular momentum of light, while S M Barnett has contributed several high quality papers to the progress of this area of physics. The editors' choice provides an excellent overview to all readers, with papers classified into eight different topics, covering the basic principles of the light and spin and orbital angular momentum, the laboratory tools for creating laser beams carrying orbital angular momentum, the optical forces and torques created by laser beams carrying angular momentum on

  7. Molecular-Frame 3D Photoelectron Momentum Distributions by Tomographic Reconstruction

    DEFF Research Database (Denmark)

    Maurer, Jochen; Dimitrovski, Darko; Christensen, Lauge

    2012-01-01

    Naphthalene molecules are fixed in space by a laser field and rotated, in 2° steps, over 180°. For each orientation, they are ionized by an intense, circularly polarized femtosecond laser pulse, and the 2D projection of the photoelectron momentum distribution is recorded. The molecular-frame 3D...... momentum distribution is obtained by tomographic reconstruction from all 90 projections. It reveals an anisotropic electron distribution, angularly shifted in the polarization plane, that is not accessible by the 2D momentum images. Our theoretical analysis shows that the magnitude of the angular shift...

  8. Isotopically resolved photoelectron imaging unravels complex atomic autoionization dynamics by two-color resonant ionization.

    Science.gov (United States)

    O'Keeffe, P; Gryzlova, E V; Cubaynes, D; Garcia, G A; Nahon, L; Grum-Grzhimailo, A N; Meyer, M

    2013-12-13

    Angle-resolved electron spectroscopy in coincidence with high-resolution mass spectroscopy has been applied to study two-color resonant photoionization in atomic xenon. Separation of different isotopes enabled us to extract results for the electronic dynamics free from depolarization effects, which are generally introduced by the coupling of the electronic and nuclear angular momenta. The concerted experimental and theoretical analysis of the photoelectron angular distributions in the region of an autoionizing resonance emphasizes the strong sensitivity of the observed structures to the fine details of the treatment of the underlying dynamics.

  9. a near ambient pressure UV photoelectron spectroscopy

    Indian Academy of Sciences (India)

    Manoj Kumar Ghosalya

    2018-03-02

    Mar 2, 2018 ... VB photoelectron spectroscopy with low energy photons is an important tool to access mostly sur- face specific electronic changes. Indeed, near ambient pressure (NAP) ultraviolet photoelectron spectroscopy. (NAP-UPS) is fully relevant to explore silver-oxygen interaction, since Ag 4d and O 2p orbitals ...

  10. Ar 3p photoelectron sideband spectra in two-color XUV + NIR laser fields

    Science.gov (United States)

    Minemoto, Shinichirou; Shimada, Hiroyuki; Komatsu, Kazma; Komatsubara, Wataru; Majima, Takuya; Mizuno, Tomoya; Owada, Shigeki; Sakai, Hirofumi; Togashi, Tadashi; Yoshida, Shintaro; Yabashi, Makina; Yagishita, Akira

    2018-04-01

    We performed photoelectron spectroscopy using femtosecond XUV pulses from a free-electron laser and femtosecond near-infrared pulses from a synchronized laser, and succeeded in measuring Ar 3p photoelectron sideband spectra due to the two-color above-threshold ionization. In our calculations of the first-order time-dependent perturbation theoretical model based on the strong field approximation, the photoelectron sideband spectra and their angular distributions are well reproduced by considering the timing jitter between the XUV and the NIR pulses, showing that the timing jitter in our experiments was distributed over the width of {1.0}+0.4-0.2 ps. The present approach can be used as a method to evaluate the timing jitter inevitable in FEL experiments.

  11. UV lamp for photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Cardoso, M.J.B.; Landers, R.; Sundaram, V.S.

    1983-01-01

    An UV lamp and a differential pumping system which enables to couple the lamp to an ultra-high vacuum chamber (10 -9 torr) without using windows, are described. The differential between the pressure inside the discharge chamber and the one in de UHV region, which is of 10 8 -10 9 , is achieved with two pumping states separated by pyrex capillaries having an internal diameter of 0.6 mm. In the first stage, a mechanical pump (10 -3 torr) is used; in the second stage, a diffusor pump with a cryogenic trap (N 2 liq - 10 -7 torr) is employed. The lamp produces, when used with high purity He, narrow lines almost clear at 21.2 eV and 40.8 eV, depending on the discharge chamber pressure, thus eliminating the need of a monochromator. As a high voltage source (3 KV), a commercial unit with a good current control was used, ensuring UV beam stability - an essential characteristic for this lamp if it is employed for photoelectron excitation of crystalline samples. (C.L.B.) [pt

  12. Analytic quantum-interference conditions in Coulomb corrected photoelectron holography

    Science.gov (United States)

    Maxwell, A. S.; Al-Jawahiry, A.; Lai, X. Y.; Figueira de Morisson Faria, C.

    2018-02-01

    We provide approximate analytic expressions for above-threshold ionization (ATI) transition probabilities and photoelectron angular distributions. These analytic expressions are more general than those existing in the literature and include the residual binding potential in the electron continuum propagation. They successfully reproduce the ATI side lobes and specific holographic structures such as the near-threshold fan-shaped pattern and the spider-like structure that extends up to relatively high photoelectron energies. We compare such expressions with the Coulomb quantum orbit strong-field approximation (CQSFA) and the full solution of the time-dependent Schrödinger equation for different driving-field frequencies and intensities, and provide an in-depth analysis of the physical mechanisms behind specific holographic structures. Our results shed additional light on what aspects of the CQSFA must be prioritized in order to obtain the key holographic features, and highlight the importance of forward scattered trajectories. Furthermore, we find that the holographic patterns change considerably for different field parameters, even if the Keldysh parameter is kept roughly the same.

  13. Fission fragment angular momentum

    International Nuclear Information System (INIS)

    Frenne, D. De

    1991-01-01

    Most of the energy released in fission is converted into translational kinetic energy of the fragments. The remaining excitation energy will be distributed among neutrons and gammas. An important parameter characterizing the scission configuration is the primary angular momentum of the nascent fragments. Neutron emission is not expected to decrease the spin of the fragments by more than one unit of angular momentum and is as such of less importance in the determination of the initial fragment spins. Gamma emission is a suitable tool in studying initial fragment spins because the emission time, number, energy, and multipolarity of the gammas strongly depend on the value of the primary angular momentum. The main conclusions of experiments on gamma emission were that the initial angular momentum of the fragments is large compared to the ground state spin and oriented perpendicular to the fission axis. Most of the recent information concerning initial fragment spin distributions comes from the measurement of isomeric ratios for isomeric pairs produced in fission. Although in nearly every mass chain isomers are known, only a small number are suitable for initial fission fragment spin studies. Yield and half-life considerations strongly limit the number of candidates. This has the advantage that the behavior of a specific isomeric pair can be investigated for a number of fissioning systems at different excitation energies of the fragments and fissioning nuclei. Because most of the recent information on primary angular momenta comes from measurements of isomeric ratios, the global deexcitation process of the fragments and the calculation of the initial fragment spin distribution from measured isomeric ratios are discussed here. The most important results on primary angular momentum determinations are reviewed and some theoretical approaches are given. 45 refs., 7 figs., 2 tabs

  14. Energy dependence of angular momentum transfer in post-collision interaction. Classical view

    Science.gov (United States)

    Gerchikov, L.; Sheinerman, S.

    2018-03-01

    A classical approach to the description of angular momentum transfer between the Auger electron and photoelectron in post-collision interaction is worked out. The results of the classical approach coincide with the quantum mechanical ones at the photoionization threshold. Besides, the approach developed provides a description of angular momentum transfer beyond the photoionization threshold. In particular, it is suitable in the energy region of comparable velocities of two emitted electrons.

  15. Development of a Schottky CdTe Medipix3RX hybrid photon counting detector with spatial and energy resolving capabilities

    Energy Technology Data Exchange (ETDEWEB)

    Gimenez, E.N., E-mail: Eva.Gimenez@diamond.ac.uk [Diamond Light Source, Harwell Campus, Oxforshire OX11 0DE (United Kingdom); Astromskas, V. [University of Surrey (United Kingdom); Horswell, I.; Omar, D.; Spiers, J.; Tartoni, N. [Diamond Light Source, Harwell Campus, Oxforshire OX11 0DE (United Kingdom)

    2016-07-11

    A multichip CdTe-Medipix3RX detector system was developed in order to bring the advantages of photon-counting detectors to applications in the hard X-ray range of energies. The detector head consisted of 2×2 Medipix3RX ASICs bump-bonded to a 28 mm×28 mm e{sup −} collection Schottky contact CdTe sensor. Schottky CdTe sensors undergo performance degrading polarization which increases with temperature, flux and the longer the HV is applied. Keeping the temperature stable and periodically refreshing the high voltage bias supply was used to minimize the polarization and achieve a stable and reproducible detector response. This leads to good quality images and successful results on the energy resolving capabilities of the system. - Highlights: • A high atomic number (CdTe sensor based) photon-counting detector was developed. • Polarization effects affected the image were minimized by regularly refreshing the bias voltage and stabilizing the temperature. • Good spatial resolution and image quality was achieved following this procedure.

  16. A new cross-detection method for improved energy-resolving photon counting under pulse pile-up

    Science.gov (United States)

    Lee, Daehee; Lim, Kyung Taek; Park, Kyungjin; Lee, Changyeop; Cho, Gyuseong

    2017-09-01

    In recent, photon counting detectors (PCDs) have been replacing the energy-integrating detectors in many medical imaging applications due to the formers' high resolution, low noise, and high efficiency. Under a high flux X-ray exposure, however, a superimposition of pulses, i.e., pulse pile-up, frequently occurs due to the finite output pulse width, causing distortions in the energy spectrum as a consequence. Therefore, pulse pile-up is considered as a major constraint in using PCDs for high flux X-ray applications. In this study, a new photon counting method is proposed to minimize degradations in PCD performance due to pulse pile-up. The proposed circuit was incorporated into a pixel with a size of 200 × 200 μm2. It was fabricated by using a 1-poly 6-metal 0 . 18 μm complementary metal-oxide-semiconductor (CMOS) process and had a power consumption of 7 . 8 μW / pixel. From the result, it was shown that the maximum count rate of the proposed circuit was increased by a factor of 4.7 when compared to that of the conventional circuit at the same pulse width of 700 ns. This implies that the energy spectrum obtained by the proposed circuit is 4.7 times more resistant to distortions than the conventional energy-resolving circuit does under higher X-ray fluxes.

  17. Development of wide-band, time and energy resolving, optical photon detectors with application to imaging astronomy

    International Nuclear Information System (INIS)

    Miller, A.J.; Cabrera, B.; Romani, R.W.; Figueroa-Feliciano, E.; Nam, S.W.; Clarke, R.M.

    2000-01-01

    Superconducting transition edge sensors (TESs) are showing promise for the wide-band spectroscopy of individual photons from the mid-infrared (IR), through the optical, and into the near ultraviolet (UV). Our TES sensors are ∼20 μm square, 40 nm thick tungsten (W) films with a transition temperature of about 80 mK. We typically attain an energy resolution of 0.15 eV FWHM over the optical range with relative timing resolution of 100 ns. Single photon events with sub-microsecond risetimes and few microsecond falltimes have been achieved allowing count rates in excess of 30 kHz per pixel. Additionally, tungsten is approximately 50% absorptive in the optical (dropping to 10% in the IR) giving these devices an intrinsically high quantum efficiency. These combined traits make our detectors attractive for fast spectrophotometers and photon-starved applications such as wide-band, time and energy resolved astronomical observations. We present recent results from our work toward the fabrication and testing of the first TES optical photon imaging arrays

  18. Polarization Effects in Attosecond Photoelectron Spectroscopy

    DEFF Research Database (Denmark)

    Baggesen, Jan Conrad; Madsen, Lars Bojer

    2010-01-01

    following the field instead. We show that polarization effects may lead to an apparent temporal shift that needs to be properly accounted for in the analysis. The effect may be isolated and studied by angle-resolved photoelectron spectroscopy from oriented polar molecules. We also show that polarization...... effects will lead to an apparent temporal shift of 50 as between photoelectrons from a 2p and 1s state in atomic hydrogen....

  19. Is CO Carbon KVV Auger Electron Emission Affected by the Photoelectron?

    International Nuclear Information System (INIS)

    Pruemper, G.; Fukuzawa, H.; Sakai, K.; Ueda, K.; Rolles, D.; Prince, K. C.; Harries, J. R.; Tamenori, Y.; Berrah, N.

    2008-01-01

    Angular distributions (ADs) of O + fragments from C 1s photoexcited CO detected in coincidence with carbon KVV Auger electrons emitted in the horizontal direction were measured at photon energies of 298, 305, 320, and 450 eV. At 450 eV, the ADs are polarization-independent and coincide with the molecular-frame Auger electron angular distribution. All measured ADs can be rationalized as a product of the same molecular-frame Auger electron angular distribution and the axial selectivity in the photoionization process. Thus the interaction between the photoelectron and the Auger electron for the normal Auger decay of CO can be neglected, and the two-step model is a good approximation

  20. Non-contact measurement of partial gas pressure and distribution of elemental composition using energy-resolved neutron imaging

    Science.gov (United States)

    Tremsin, A. S.; Losko, A. S.; Vogel, S. C.; Byler, D. D.; McClellan, K. J.; Bourke, M. A. M.; Vallerga, J. V.

    2017-01-01

    Neutron resonance absorption imaging is a non-destructive technique that can characterize the elemental composition of a sample by measuring nuclear resonances in the spectrum of a transmitted beam. Recent developments in pixelated time-of-flight imaging detectors coupled with pulsed neutron sources pose new opportunities for energy-resolved imaging. In this paper we demonstrate non-contact measurements of the partial pressure of xenon and krypton gases encapsulated in a steel pipe while simultaneously passing the neutron beam through high-Z materials. The configuration was chosen as a proof of principle demonstration of the potential to make non-destructive measurement of gas composition in nuclear fuel rods. The pressure measured from neutron transmission spectra (˜739 ± 98 kPa and ˜751 ± 154 kPa for two Xe resonances) is in relatively good agreement with the pressure value of ˜758 ± 21 kPa measured by a pressure gauge. This type of imaging has been performed previously for solids with a spatial resolution of ˜ 100 μm. In the present study it is demonstrated that the high penetration capability of epithermal neutrons enables quantitative mapping of gases encapsulate within high-Z materials such as steel, tungsten, urania and others. This technique may be beneficial for the non-destructive testing of bulk composition of objects (such as spent nuclear fuel assemblies and others) containing various elements opaque to other more conventional imaging techniques. The ability to image the gaseous substances concealed within solid materials also allows non-destructive leak testing of various containers and ultimately measurement of gas partial pressures with sub-mm spatial resolution.

  1. Calorimetric low-temperature detectors on semiconductor base for the energy-resolving detection of heavy ions

    International Nuclear Information System (INIS)

    Kienlin, A. von.

    1994-01-01

    In the framework of this thesis for the first time calorimetric low-temperature detectors for the energy-resolving detection of heavy ions were developed and successfully applied. Constructed were two different detector types, which work both with a semiconductor thermistor. The temperature increasement effected by a particle incidence is read out. In the first detector type the thermistor was simutaneously used as absorber. The thickness of the germanium crystals was sufficient in order to stop the studied heavy ions completely. In the second type, a composed calorimeter, a sapphire crystal, which was glued on a germanium thermistor, served as absorber for the incident heavy ions. The working point of the calorimeter lies in the temperature range (1.2-4.2 K), which is reachable with a pumped 4 He cryostat. The temperatur increasement of the calorimeter amounts after the incidence of a single α particle about 20-30 μK and that after a heavy ion incidence up to some mK. An absolute energy resolution of 400-500 keV was reached. In nine beam times the calorimeters were irradiated by heavy ions ( 20 Ne, 40 Ar, 136 Xe, 208 Pb, 209 Bi) of different energies (3.6 MeV/nucleon< E<12.5 MeV/nucleon) elastically scattered from gold foils. In the pulse height spectra of the first detector type relatively broad, complex-structurated line shapes were observed. By systematic measurements dependences of the complex line structures on operational parameters of the detector, the detector temperature, and the position of the incident particle could be detected. Together with the results of further experiments a possible interpretation of these phenomena is presented. Contrarily to the complex line structures of the pure germanium thermistor the line shapes in the pulse height spectra, which were taken up in a composite germanium/sapphire calorimeter, are narrow and Gauss-shaped

  2. Non-contact measurement of partial gas pressure and distribution of elemental composition using energy-resolved neutron imaging

    Directory of Open Access Journals (Sweden)

    A. S. Tremsin

    2017-01-01

    Full Text Available Neutron resonance absorption imaging is a non-destructive technique that can characterize the elemental composition of a sample by measuring nuclear resonances in the spectrum of a transmitted beam. Recent developments in pixelated time-of-flight imaging detectors coupled with pulsed neutron sources pose new opportunities for energy-resolved imaging. In this paper we demonstrate non-contact measurements of the partial pressure of xenon and krypton gases encapsulated in a steel pipe while simultaneously passing the neutron beam through high-Z materials. The configuration was chosen as a proof of principle demonstration of the potential to make non-destructive measurement of gas composition in nuclear fuel rods. The pressure measured from neutron transmission spectra (∼739 ± 98 kPa and ∼751 ± 154 kPa for two Xe resonances is in relatively good agreement with the pressure value of ∼758 ± 21 kPa measured by a pressure gauge. This type of imaging has been performed previously for solids with a spatial resolution of ∼ 100 μm. In the present study it is demonstrated that the high penetration capability of epithermal neutrons enables quantitative mapping of gases encapsulate within high-Z materials such as steel, tungsten, urania and others. This technique may be beneficial for the non-destructive testing of bulk composition of objects (such as spent nuclear fuel assemblies and others containing various elements opaque to other more conventional imaging techniques. The ability to image the gaseous substances concealed within solid materials also allows non-destructive leak testing of various containers and ultimately measurement of gas partial pressures with sub-mm spatial resolution.

  3. Angular momentum projected semiclassics

    International Nuclear Information System (INIS)

    Hasse, R.W.

    1986-10-01

    By using angular momentum projected plane waves as wave functions, we derive semiclassical expressions for the single-particle propagator, the partition function, the nonlocal density matrix, the single-particle density and the one particle- one hole level density for fixed angular momentum and fixed z-component or summed over the z-components. Other quantities can be deduced from the propagator. In coordinate space (r, r') the relevant quantities depend on vertical stroker - r 3 vertical stroke instead of vertical stroker - r'vertical stroke and in Wigner space (R, P) they become proportional to the angular momentum constraints δ(vertical strokeRxPvertical stroke/ℎ - l) and δ((RxP) z /ℎ - m). As applications we calculate the single-particle and one particle- one hole level densities for harmonic oscillator and Hill-Wheeler box potentials and the imaginary part of the optical potential and its volume integral with an underlying harmonic oscillator potential and a zero range two-body interaction. (orig.)

  4. Angular Momentum in Fission

    Science.gov (United States)

    Gönnenwein, F.; Bunakov, V.; Dorvaux, O.; Gagarski, A.; Guseva, I.; Hanappe, F.; Kadmensky, S.; von Kalben, J.; Khlebnikov, S.; Kinnard, V.; Kopatch, Yu.; Mutterer, M.; Nesvizhevsky, V.; Petrov, G.; Prokhorova, E.; Rubchenya, V.; Sillanpää, M.; Simpson, G.; Sokolov, V.; Soldner, T.; Stuttgé, L.; Tiourine, G.; Trzaska, W.; Tsekhanovich, I.; Wagemans, C.; Wollersheim, H.-J.; Zavarukhina, T.; Zimmer, O.

    2008-04-01

    Three novel experiments in spontaneous and thermal neutron induced fission all with a bearing on angular momentum in fission are reviewed. In the first experiment it was observed that, in the reaction 235U(n, f) with incident polarized cold neutrons, the nucleus undergoing scission is rotating. This was inferred from the shift in angular distributions of ternary particles being dependent on the orientation of neutron spin. In the second study the properties of the angular momentum of spherical fission fragments was investigated. Current theories trace the spin of fragments to their deformations allowing for collective rotational vibrations at scission. However, in particular the spherical 132Te isotope exhibits a large spin at variance with theory. Exploiting the specific properties of cold deformed fission it could be proven that, for 132Te, single particle excitations instead of collective modes are responsible for the large spin observed. In a third project a pilot study was exploring the possibility to search for an evaporation of neutrons from fragments being anisotropic in their own cm-system. Due to fragment spin this anisotropy is claimed since decades to exist. It was so far never observed. A scheme has been devised and tested were triple coincidences between a fragment and two neutrons are evaluated in a way to bring the cm-anisotropy into the foreground while getting rid of the kinematical anisotropy in the lab-system due to evaporation from moving fragments. The test was run for spontaneous fission of 252Cf.

  5. Photoelectron angular distributions from polar molecules probed by intense femtosecond lasers

    DEFF Research Database (Denmark)

    Abu-Samha, Mahmoud; Madsen, Lars Bojer

    2010-01-01

    -active-electron and frozen-nuclei approximations. Our analysis shows that for the HF and LiF molecules, anisotropies in the molecular potential and the probed orbital lead to enhanced ionization during laser half cycles with the field pointing antiparallel to the permanent dipole of the dipole term in a multipolar expansion...

  6. Prototype of an angular-selective photoelectron calibration source for the KATRIN experiment

    Czech Academy of Sciences Publication Activity Database

    Valerius, K.; Hein, H.; Baumeister, H.; Beck, M.; Bokeloh, K.; Bonn, J.; Gluck, F.; Ortjohann, H.W.; Ostrick, B.; Zbořil, Miroslav; Weinheimer, Ch.

    2011-01-01

    Roč. 6, - (2011), P01002/1-P01002/11 ISSN 1748-0221 R&D Projects: GA MŠk LA318; GA MŠk LC07050 Institutional research plan: CEZ:AV0Z10480505 Keywords : Spectrometers * Photoemission * Detector alignment and calibration methods (lasers, sources, particle-beams) Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 1.869, year: 2011

  7. Photoelectron spectroscopic and microspectroscopic probes of ferroelectrics

    Science.gov (United States)

    Tǎnase, Liviu C.; Abramiuc, Laura E.; Teodorescu, Cristian M.

    2017-12-01

    This contribution is a review of recent aspects connected with photoelectron spectroscopy of free ferroelectric surfaces, metals interfaced with these surfaces, graphene-like layers together with some exemplifications concerning molecular adsorption, dissociations and desorptions occurring from ferroelectrics. Standard photoelectron spectroscopy is used nowadays in correlation with other characterization techniques, such as piezoresponse force microscopy, high resolution transmission electron spectroscopy, and ferroelectric hysteresis cycles. In this work we will concentrate mainly on photoelectron spectroscopy and spectro-microscopy characterization of ferroelectric thin films, starting from atomically clean ferroelectric surfaces of lead zirco-titanate, then going towards heterostructures using this material in combination with graphene-like carbon layers or with metals. Concepts involving charge accumulation and depolarization near surface will be revisited by taking into account the newest findings in this area.

  8. Performance of the SRRC scanning photoelectron microscope

    CERN Document Server

    Hong, I H; Yin, G C; Wei, D H; Juang, J M; Dann, T E; Klauser, R; Chuang, T J; Chen, C T; Tsang, K L

    2001-01-01

    A scanning photoelectron microscope has been constructed at SRRC. This SPEM system consists primarily of a Fresnel zone plate (ZP) with an order-selection aperture, a flexure scanning stage, a hemispherical electron analyzer, and sample/ZP insertion system. The flexure stage is used to scan the sample. A hemispherical analyzer with Omni V lens and a 16-channel multichannel detector (MCD) is used to collect photoelectrons. A set of 16 photoelectron images at different kinetic energies can be simultaneously acquired in one single scan. The data acquisition system is designed to collect up to 32 images concurrently, including 16 MCD signals, total electron yield and transmitted photon flux. The design and some initial test results of this SPEM station are presented and discussed.

  9. Performance of the SRRC scanning photoelectron microscope

    International Nuclear Information System (INIS)

    Hong, I.-H.; Lee, T.-H.; Yin, G.-C.; Wei, D.-H.; Juang, J.-M.; Dann, T.-E.; Klauser, R.; Chuang, T.J.; Chen, C.T.; Tsang, K.-L.

    2001-01-01

    A scanning photoelectron microscope has been constructed at SRRC. This SPEM system consists primarily of a Fresnel zone plate (ZP) with an order-selection aperture, a flexure scanning stage, a hemispherical electron analyzer, and sample/ZP insertion system. The flexure stage is used to scan the sample. A hemispherical analyzer with Omni V lens and a 16-channel multichannel detector (MCD) is used to collect photoelectrons. A set of 16 photoelectron images at different kinetic energies can be simultaneously acquired in one single scan. The data acquisition system is designed to collect up to 32 images concurrently, including 16 MCD signals, total electron yield and transmitted photon flux. The design and some initial test results of this SPEM station are presented and discussed

  10. Optical angular momentum and atoms.

    Science.gov (United States)

    Franke-Arnold, Sonja

    2017-02-28

    Any coherent interaction of light and atoms needs to conserve energy, linear momentum and angular momentum. What happens to an atom's angular momentum if it encounters light that carries orbital angular momentum (OAM)? This is a particularly intriguing question as the angular momentum of atoms is quantized, incorporating the intrinsic spin angular momentum of the individual electrons as well as the OAM associated with their spatial distribution. In addition, a mechanical angular momentum can arise from the rotation of the entire atom, which for very cold atoms is also quantized. Atoms therefore allow us to probe and access the quantum properties of light's OAM, aiding our fundamental understanding of light-matter interactions, and moreover, allowing us to construct OAM-based applications, including quantum memories, frequency converters for shaped light and OAM-based sensors.This article is part of the themed issue 'Optical orbital angular momentum'. © 2017 The Author(s).

  11. AngularJS directives

    CERN Document Server

    Vanston, Alex

    2013-01-01

    This book uses a practical, step-by-step approach, starting with how to build directives from the ground up before moving on to creating web applications comprised of multiple modules all working together to provide the best user experience possible.This book is intended for intermediate JavaScript developers who are looking to enhance their understanding of single-page web application development with a focus on AngularJS and the JavaScript MVC frameworks.It is expected that readers will understand basic JavaScript patterns and idioms and can recognize JSON formatted data.

  12. Calculated characteristics of multichannel photoelectron multipliers

    International Nuclear Information System (INIS)

    Vasil'chenko, V.G.; Dajkovskij, A.G.; Milova, N.V.; Rakhmatov, V.E.; Rykalin, V.I.

    1990-01-01

    Structural features and main calculated characteristics of some modifications of position-sensitive two-coordinate multichannel photoelectron multipliers (PEM) with plate-type multiplying systems are described. The presented PEM structures are free from direct optical and ion feedbacks, provide coordinate resolution ≅ 1 mm with efficiency of photoelectron detection ≅ 90%. Capabilities for using silicon field-effect photocathodes, providing electron extraction into vacuum, as well as prospects of using multichannel multiplying systems for readout of the data from solid detectors are considered

  13. Angular Distribution of GRBs

    Directory of Open Access Journals (Sweden)

    L. G. Balázs

    2012-01-01

    Full Text Available We studied the complete randomness of the angular distribution of BATSE gamma-ray bursts (GRBs. Based on their durations and peak fluxes, we divided the BATSE sample into 5 subsamples (short1, short2, intermediate, long1, long2 and studied the angular distributions separately. We used three methods to search for non-randomness in the subsamples: Voronoi tesselation, minimal spanning tree, and multifractal spectra. To study any non-randomness in the subsamples we defined 13 test-variables (9 from Voronoi tesselation, 3 from the minimal spanning tree and one from the multifractal spectrum. We made Monte Carlo simulations taking into account the BATSE’s sky-exposure function. We tested therandomness by introducing squared Euclidean distances in the parameter space of the test-variables. We recognized that the short1, short2 groups deviate significantly (99.90%, 99.98% from the fully random case in the distribution of the squared Euclidean distances but this is not true for the long samples. In the intermediate group, the squared Euclidean distances also give significant deviation (98.51%.

  14. Polarity of wurtzite crystals by photoelectron diffraction

    Czech Academy of Sciences Publication Activity Database

    Bartoš, Igor; Romanyuk, Olexandr

    2014-01-01

    Roč. 315, OCT (2014), s. 506-509 ISSN 0169-4332 Grant - others:AVČR(CZ) M100101201 Institutional support: RVO:68378271 Keywords : wurtzite semiconductors * surface polarity * X-ray photoelectron diffraction * XPD Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.711, year: 2014 http://www.sciencedirect.com/science/article/pii/S016943321400066X

  15. Photoelectron Spectroscopy in Advanced Placement Chemistry

    Science.gov (United States)

    Benigna, James

    2014-01-01

    Photoelectron spectroscopy (PES) is a new addition to the Advanced Placement (AP) Chemistry curriculum. This article explains the rationale for its inclusion, an overview of how the PES instrument records data, how the data can be analyzed, and how to include PES data in the course. Sample assessment items and analysis are included, as well as…

  16. Threshold photoelectron spectroscopy of acetaldehyde and acrolein

    International Nuclear Information System (INIS)

    Yencha, Andrew J.; Siggel-King, Michele R.F.; King, George C.; Malins, Andrew E.R.; Eypper, Marie

    2013-01-01

    Highlights: •High-resolution threshold photoelectron spectrum of acetaldehyde. •High-resolution threshold photoelectron spectrum of acrolein. •High-resolution total photoion yield spectrum of acetaldehyde. •High-resolution total photoion yield spectrum of acrolein. •Determination of vertical ionization potentials in acetaldehyde and acrolein. -- Abstract: High-resolution (6 meV and 12 meV) threshold photoelectron (TPE) spectra of acetaldehyde and acrolein (2-propenal) have been recorded over the valence binding energy region 10–20 eV, employing synchrotron radiation and a penetrating-field electron spectrometer. These TPE spectra are presented here for the first time. All of the band structures observed in the TPE spectra replicate those found in their conventional HeI photoelectron (PE) spectra. However, the relative band intensities are found to be dramatically different in the two types of spectra that are attributed to the different dominant operative formation mechanisms. In addition, some band shapes and their vertical ionization potentials are found to differ in the two types of spectra that are associated with the autoionization of Rydberg states in the two molecules

  17. Classical ultraviolet photoelectron spectroscopy of polymers

    International Nuclear Information System (INIS)

    Salaneck, W.R.

    2009-01-01

    Although X-ray photoelectron spectroscopy of polymers was well established by Clark and coworkers in the 1970s, ultraviolet photoelectron spectroscopy of polymer films, was developed later. Previous to the 1970s, the first attempts to use ultraviolet light on polymer films took the form of appearance potential (valence band edge) measurements. Only some years later could the full valence band region of thin polymer films, including insulating polymers, semiconducting polymers and electrically conducting polymers. The development of what might be termed 'classical ultraviolet photoelectron spectroscopy' of polymer films may be loosely based upon a variety of issues, including adapting thin polymer film technology to ultra high vacuum studies, the widespread use of helium resonance lamps for studies of solid surfaces, the combined advent of practical and sufficient theoretical-computational methods. The advent of, and the use of, easily available synchrotron radiation for multi-photon spectroscopies, nominally in the area of the near UV, is not included in the term 'classical'. At the same time, electrically conducting polymers were discovered, leading to applications of the corresponding semiconducting polymers, which added technologically driven emphasis to this development of ultraviolet photoelectron spectroscopy for polymer materials. This paper traces a limited number of highlights in the evolution of ultraviolet photoelectron spectroscopy of polymers, from the 1970s through to 2008. Also, since this issue is dedicated to Prof. Kazuhiko Seki, who has been a friend and competitor for over two decades, the author relies on some of Prof. Seki's earlier research, unpublished, on who-did-what-first. Prof. Seki's own contributions to the field, however, are discussed in other articles in this issue.

  18. Oscillatory behavior of the valence photoionization properties of N2 and O2 due to coherent photoelectron emission from two sites

    Science.gov (United States)

    Viefhaus, Jens; Ilchen, Markus; Deinert, Sascha; Glaser, Leif; Scholz, Frank; Walter, Peter; Braune, Markus; Meißner, André; Tribedi, Lokesh; Becker, Uwe

    2012-11-01

    Coherent two-center photoelectron emission has been predicted for all electron subshells. So far, however, is has been only proven for the innermost 1s-subshell only. We present first results for the valence photoionization of N2 and O2 showing oscillatory behavior in both, the partial cross section σ and the angular distribution asymmetry parameter β.

  19. Photoelectron yields of scintillation counters with embedded wavelength-shifting fibers read out with silicon photomultipliers

    Energy Technology Data Exchange (ETDEWEB)

    Artikov, Akram; Baranov, Vladimir; Blazey, Gerald C.; Chen, Ningshun; Chokheli, Davit; Davydov, Yuri; Dukes, E. Craig; Dychkant, Alexsander; Ehrlich, Ralf; Francis, Kurt; Frank, M. J.; Glagolev, Vladimir; Group, Craig; Hansen, Sten; Magill, Stephen; Oksuzian, Yuri; Pla-Dalmau, Anna; Rubinov, Paul; Simonenko, Aleksandr; Song, Enhao; Stetzler, Steven; Wu, Yongyi; Uzunyan, Sergey; Zutshi, Vishnu

    2018-05-01

    Photoelectron yields of extruded scintillation counters with titanium dioxide coating and embedded wavelength shifting fibers read out by silicon photomultipliers have been measured at the Fermilab Test Beam Facility using 120\\,GeV protons. The yields were measured as a function of transverse, longitudinal, and angular positions for a variety of scintillator compositions and reflective coating mixtures, fiber diameters, and photosensor sizes. Timing performance was also studied. These studies were carried out by the Cosmic Ray Veto Group of the Mu2e collaboration as part of their R\\&D program.

  20. Depth-profiling using X-ray photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Pijolat, M.; Hollinger, G.

    1980-12-01

    The possibilities of X-ray photoelectron spectroscopy (or ESCA) for depth-profiling into shallow depths (approximately 10-100 A) have been studied. The method of ion-sputtering removal has first been investigated in order to improve its depth-resolution (approximately 50-150 A). A procedure which eliminates the effects due to the resolution function of the instrumental probe (analysed depth approximately 50 A) has been settled; but it is not yet sufficient, and the sputter - broadening due to the ion-induced damages must be taken into account (broadening function approximately 50 A for approximately 150 A removal). Because of serious difficulties in estimating the broadening function an alternative is to develop non destructive methods, so a new method based on the dependence of the analysed depth with the electron emission angle is presented. The extraction of the concentration profile from angular distribution experiments is achieved, in the framework of a flat-layer model, by minimizing the difference between theoretical and experimental relative intensities. The applicability and limitations of the method are discussed on the basis of computer simulation results. The depth probed is of the order of 3 lambda (lambda being the value of the inelastic mean free path, typically 10-20 A) and the depth-resolution is of the order of lambda/3 [fr

  1. Polarization and dipole effects in hard X-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Novak, M. [Universite Libre de Bruxelles, Service de Metrologie Nucleaire (CP 165/84), 50 av. F. D. Roosevelt, B-1050 Brussels (Belgium); Pauly, N., E-mail: nipauly@ulb.ac.be [Universite Libre de Bruxelles, Service de Metrologie Nucleaire (CP 165/84), 50 av. F. D. Roosevelt, B-1050 Brussels (Belgium); Dubus, A. [Universite Libre de Bruxelles, Service de Metrologie Nucleaire (CP 165/84), 50 av. F. D. Roosevelt, B-1050 Brussels (Belgium)

    2012-03-15

    Highlights: Black-Right-Pointing-Pointer X-rays are unpolarized or linearly polarized. Black-Right-Pointing-Pointer A difference of polarization implies a variation in path travelled by the photoelectrons. Black-Right-Pointing-Pointer We show the influence of the polarization on the partial intensity distributions. Black-Right-Pointing-Pointer We also point out the influence of the dipole approximation. Black-Right-Pointing-Pointer We use Monte Carlo simulations. - Abstract: Hard X-ray photoelectron spectroscopy (HXPS) using X-rays in the 1.5-15 keV energy range generated by synchrotron sources becomes an increasingly important analysis technique due to its potential for bulk sensitive measurements. However, besides their high energy, another characteristic of photons generated by synchrotron sources is their linear polarization while X-rays from Al K{alpha} or Mg K{alpha} for instance are unpolarized. This difference implies a possible variation in total path travelled by the photoelectrons generated by the X-rays inside the medium and consequently a modification of the resulting spectrum shape. We show the influence of the polarization on the partial intensity distributions, namely the number of electrons escaping after n inelastic scattering events, for photoelectron with energies of 0.5, 1, 2, 3, 4 and 5 keV and originating from Si 1s{sub 1/2}, Cu 1s{sub 1/2}, Cu 2p{sub 3/2}, Au 4d{sub 3/2} and Au 4f{sub 7/2} subshells. Moreover, we point out the influence of the dipole approximation leading to an underestimation of the partial intensity distributions due to the neglect of the forward-backward asymmetry of the angular photoelectron distribution.

  2. Ultrafast Internal Conversion of Aromatic Molecules Studied by Photoelectron Spectroscopy using Sub-20 fs Laser Pulses

    Directory of Open Access Journals (Sweden)

    Toshinori Suzuki

    2014-02-01

    Full Text Available This article describes our recent experimental studies on internal conversion via a conical intersection using photoelectron spectroscopy. Ultrafast S2(ππ*–S1(nπ* internal conversion in pyrazine is observed in real time using sub-20 fs deep ultraviolet pulses (264 and 198 nm. While the photoelectron kinetic energy distribution does not exhibit a clear signature of internal conversion, the photoelectron angular anisotropy unambiguously reveals the sudden change of electron configuration upon internal conversion. An explanation is presented as to why these two observables have different sensitivities to internal conversion. The 198 nm probe photon energy is insufficient for covering the entire Franck-Condon envelopes upon photoionization from S2/S1 to D1/D0. A vacuum ultraviolet free electron laser (SCSS producing 161 nm radiation is employed to solve this problem, while its pulse-to-pulse timing jitter limits the time resolution to about 1 ps. The S2–S1 internal conversion is revisited using the sub-20 fs 159 nm pulse created by filamentation four-wave mixing. Conical intersections between D1(π−1 and D0(n−1 and also between the Rydberg state with a D1 ion core and that with a D0 ion core of pyrazine are studied by He(I photoelectron spectroscopy, pulsed field ionization photoelectron spectroscopy and one-color resonance-enhanced multiphoton ionization spectroscopy. Finally, ultrafast S2(ππ*–S1(ππ* internal conversion in benzene and toluene are compared with pyrazine.

  3. Ultraviolet photoelectron spectroscopy of transient species

    International Nuclear Information System (INIS)

    Leeuw, D.M. de.

    1979-01-01

    Transient species are studied in the isolation of the gas phase using ultraviolet photoelectron spectroscopy (PES). A description of the equipment used and a discussion of some theoretical topics, which play a role in the interpretation of PE spectra, are given. Koopmans' theorem, Hartree-Fock-Slater (HFS) calculations and the sum rule are discussed. A versatile ultraviolet PE spectrometer, designed specifically for this purpose, has been built and the construction and performance of this instrument are described. (Auth.)

  4. Photoelectronic Sensor with Gold Nanoparticle Plasmon Antenna

    Science.gov (United States)

    2016-07-20

    result will open new doors for ultra-small biosensor chips integrated with multi-functional solid-state devices. 15. SUBJECT TERMS Photoelectronic Sensor...detected with the hybrid device. This result will open new doors for ultra-small biosensor chips integrated with multi-functional solid-state devices...been applied for high-sensitivity biosensors . The frequency and intensity of surface Plasmon absorption bands are sensitive to the type of material

  5. Angular integrals in d dimensions

    International Nuclear Information System (INIS)

    Somogyi, Gabor

    2011-01-01

    We discuss the evaluation of certain d dimensional angular integrals which arise in perturbative field theory calculations. We find that the angular integral with n denominators can be computed in terms of a certain special function, the so-called H-function of several variables. We also present several illustrative examples of the general result and briefly consider some applications. (orig.)

  6. Angular-domain scattering interferometry.

    Science.gov (United States)

    Shipp, Dustin W; Qian, Ruobing; Berger, Andrew J

    2013-11-15

    We present an angular-scattering optical method that is capable of measuring the mean size of scatterers in static ensembles within a field of view less than 20 μm in diameter. Using interferometry, the method overcomes the inability of intensity-based models to tolerate the large speckle grains associated with such small illumination areas. By first estimating each scatterer's location, the method can model between-scatterer interference as well as traditional single-particle Mie scattering. Direct angular-domain measurements provide finer angular resolution than digitally transformed image-plane recordings. This increases sensitivity to size-dependent scattering features, enabling more robust size estimates. The sensitivity of these angular-scattering measurements to various sizes of polystyrene beads is demonstrated. Interferometry also allows recovery of the full complex scattered field, including a size-dependent phase profile in the angular-scattering pattern.

  7. X-ray Photoelectron Spectroscopy Database (Version 4.1)

    Science.gov (United States)

    SRD 20 X-ray Photoelectron Spectroscopy Database (Version 4.1) (Web, free access)   The NIST XPS Database gives access to energies of many photoelectron and Auger-electron spectral lines. The database contains over 22,000 line positions, chemical shifts, doublet splittings, and energy separations of photoelectron and Auger-electron lines.

  8. Non-Destructive Study of Bulk Crystallinity and Elemental Composition of Natural Gold Single Crystal Samples by Energy-Resolved Neutron Imaging

    Science.gov (United States)

    Tremsin, Anton S.; Rakovan, John; Shinohara, Takenao; Kockelmann, Winfried; Losko, Adrian S.; Vogel, Sven C.

    2017-01-01

    Energy-resolved neutron imaging enables non-destructive analyses of bulk structure and elemental composition, which can be resolved with high spatial resolution at bright pulsed spallation neutron sources due to recent developments and improvements of neutron counting detectors. This technique, suitable for many applications, is demonstrated here with a specific study of ~5–10 mm thick natural gold samples. Through the analysis of neutron absorption resonances the spatial distribution of palladium (with average elemental concentration of ~0.4 atom% and ~5 atom%) is mapped within the gold samples. At the same time, the analysis of coherent neutron scattering in the thermal and cold energy regimes reveals which samples have a single-crystalline bulk structure through the entire sample volume. A spatially resolved analysis is possible because neutron transmission spectra are measured simultaneously on each detector pixel in the epithermal, thermal and cold energy ranges. With a pixel size of 55 μm and a detector-area of 512 by 512 pixels, a total of 262,144 neutron transmission spectra are measured concurrently. The results of our experiments indicate that high resolution energy-resolved neutron imaging is a very attractive analytical technique in cases where other conventional non-destructive methods are ineffective due to sample opacity. PMID:28102285

  9. AngularJS testing cookbook

    CERN Document Server

    Bailey, Simon

    2015-01-01

    This book is intended for developers who have an understanding of the basic principles behind both AngularJS and test-driven development. You, as a developer, are interested in eliminating the fear related to either introducing tests to an existing codebase or starting out testing on a fresh AngularJS application. If you're a team leader or part of a QA team with the responsibility of ensuring full test coverage of an application, then this book is ideal for you to comprehend the full testing scope required by your developers. Whether you're new to or are well versed with AngularJS, this book

  10. Time-resolved photoelectron imaging of excited state relaxation dynamics in phenol, catechol, resorcinol, and hydroquinone.

    Science.gov (United States)

    Livingstone, Ruth A; Thompson, James O F; Iljina, Marija; Donaldson, Ross J; Sussman, Benjamin J; Paterson, Martin J; Townsend, Dave

    2012-11-14

    Time-resolved photoelectron imaging was used to investigate the dynamical evolution of the initially prepared S(1) (ππ*) excited state of phenol (hydroxybenzene), catechol (1,2-dihydroxybenzene), resorcinol (1,3-dihydroxybenzene), and hydroquinone (1,4-dihydroxybenzene) following excitation at 267 nm. Our analysis was supported by ab initio calculations at the coupled-cluster and CASSCF levels of theory. In all cases, we observe rapid (<1 ps) intramolecular vibrational redistribution on the S(1) potential surface. In catechol, the overall S(1) state lifetime was observed to be 12.1 ps, which is 1-2 orders of magnitude shorter than in the other three molecules studied. This may be attributed to differences in the H atom tunnelling rate under the barrier formed by a conical intersection between the S(1) state and the close lying S(2) (πσ*) state, which is dissociative along the O-H stretching coordinate. Further evidence of this S(1)/S(2) interaction is also seen in the time-dependent anisotropy of the photoelectron angular distributions we have observed. Our data analysis was assisted by a matrix inversion method for processing photoelectron images that is significantly faster than most other previously reported approaches and is extremely quick and easy to implement.

  11. X-Ray photoelectron Spectroscopy Applications

    Energy Technology Data Exchange (ETDEWEB)

    Engelhard, Mark H.; Droubay, Timothy C.; Du, Yingge

    2017-01-03

    With capability for obtaining quantitative elemental composition, chemical and electronic state, and overlayer thickness information from the top ~10 nm of a sample surface, X-ray Photoelectron Spectroscopy (XPS) or Electron Spectroscopy for Chemical Analysis (ESCA) is a versatile and widely used technique for analyzing surfaces. The technique is applied to a host of materials, from insulators to conductors in virtually every scientific field and sub-discipline. More recently, XPS has been extended under in-situ and operando conditions. Following a brief introduction to XPS principles and instrument components, this article exemplifies widely ranging XPS applications in material and life sciences.

  12. Lidar Orbital Angular Momentum Sensor

    Data.gov (United States)

    National Aeronautics and Space Administration — The recognition in recent decades that electromagnetic fields have angular momentum (AM) in the form of not only polarization (or spin AM) but also orbital (OAM) has...

  13. Angular momentum from tidal torques

    International Nuclear Information System (INIS)

    Barnes, J.; Efstathiou, G.; Cambridge Univ., England)

    1987-01-01

    The origin of the angular momentum of bound objects in large N-body simulations is studied using three sets of models. One model with white-noise initial conditions is analyzed as well as two in which the initial conditions have more power on large scales, as predicted in models with cold dark matter. The growth and distribution of angular momentum in individual objects is studied and it is found that the specific angular momentum distribution of bound clumps increases in a near linear fashion with radius while the orientation of the angular momentum in the inner high-density regions is often poorly correlated with that of the outer parts. It is also found that the dimensionless spin parameter is insensitive to the initial perturbation spectrum and has a median value of about 0.05. 61 references

  14. Plasmons with orbital angular momentum

    International Nuclear Information System (INIS)

    Mendonca, J. T.; Ali, S.; Thide, B.

    2009-01-01

    Electron plasma waves carrying orbital angular momentum are investigated in an unmagnetized collisionless plasma composed of inertial electrons and static ions. For this purpose, the usual plasmon dispersion relation is employed to derive an approximate paraxial equation. The latter is analyzed with a Gaussian beam solution. For a finite angular momentum associated with the plasmon, Laguerre-Gaussian (LG) solutions are employed for solving the electrostatic potential problem which gives approximate solution and is valid for plasmon beams in the paraxial approximation. The LG potential determines the electric field components and energy flux of plasmons with finite angular momentum. Numerical illustrations show that the radial and angular mode numbers strongly modify the profiles of the LG potential.

  15. Rectilinear Graphs and Angular Resolution

    NARCIS (Netherlands)

    Bodlaender, H.L.; Tel, G.

    2003-01-01

    In this note we show that a planar graph with angular resolution at least π/2 can be drawn with all angles an integer multiple of π/2, that is, in a rectilinear manner. Moreover, we show that for d ≠ 4, d › 2, having an angular resolution of 2π/d does not imply that the graph can be drawn with all

  16. Carbon K-shell photoionization of CO: Molecular frame angular distributions of normal and conjugate shakeup satellites

    International Nuclear Information System (INIS)

    Jahnke, T.; Titze, J.; Foucar, L.; Wallauer, R.; Osipov, T.; Benis, E.P.; Jagutzki, O.; Arnold, W.; Czasch, A.; Staudte, A.; Schoeffler, M.; Alnaser, A.; Weber, T.; Prior, M.H.; Schmidt-Boecking, H.; Doerner, R.

    2011-01-01

    We have measured the molecular frame angular distributions of photoelectrons emitted from the Carbon K-shell of fixed-in-space CO molecules for the case of simultaneous excitation of the remaining molecular ion. Normal and conjugate shakeup states are observed. Photoelectrons belonging to normal Σ-satellite lines show an angular distribution resembling that observed for the main photoline at the same electron energy. Surprisingly a similar shape is found for conjugate shakeup states with Π-symmetry. In our data we identify shake rather than electron scattering (PEVE) as the mechanism producing the conjugate lines. The angular distributions clearly show the presence of a Σ shape resonance for all of the satellite lines.

  17. Digital fast pulse shape and height analysis on cadmium-zinc-telluride arrays for high-flux energy-resolved X-ray imaging.

    Science.gov (United States)

    Abbene, Leonardo; Principato, Fabio; Gerardi, Gaetano; Bettelli, Manuele; Seller, Paul; Veale, Matthew C; Zambelli, Nicola; Benassi, Giacomo; Zappettini, Andrea

    2018-01-01

    Cadmium-zinc-telluride (CZT) arrays with photon-counting and energy-resolving capabilities are widely proposed for next-generation X-ray imaging systems. This work presents the performance of a 2 mm-thick CZT pixel detector, with pixel pitches of 500 and 250 µm, dc coupled to a fast and low-noise ASIC (PIXIE ASIC), characterized only by the preamplifier stage. A custom 16-channel digital readout electronics was used, able to digitize and process continuously the signals from each output ASIC channel. The digital system performs on-line fast pulse shape and height analysis, with a low dead-time and reasonable energy resolution at both low and high fluxes. The spectroscopic response of the system to photon energies below ( 109 Cd source) and above ( 241 Am source) the K-shell absorption energy of the CZT material was investigated, with particular attention to the mitigation of charge sharing and pile-up. The detector allows high bias voltage operation (>5000 V cm -1 ) and good energy resolution at moderate cooling (3.5% and 5% FWHM at 59.5 keV for the 500 and 250 µm arrays, respectively) by using fast pulse shaping with a low dead-time (300 ns). Charge-sharing investigations were performed using a fine time coincidence analysis (TCA), with very short coincidence time windows up to 10 ns. For the 500 µm pitch array (250 µm pitch array), sharing percentages of 36% (52%) and 60% (82%) at 22.1 and 59.5 keV, respectively, were measured. The potential of the pulse shape analysis technique for charge-sharing detection for corner/border pixels and at high rate conditions (250 kcps pixel -1 ), where the TCA fails, is also shown. Measurements demonstrated that significant amounts of charge are lost for interactions occurring in the volume of the inter-pixel gap. This charge loss must be accounted for in the correction of shared events. These activities are within the framework of an international collaboration on the development of energy-resolved

  18. Graphene Membranes for Atmospheric Pressure Photoelectron Spectroscopy.

    Science.gov (United States)

    Weatherup, Robert S; Eren, Baran; Hao, Yibo; Bluhm, Hendrik; Salmeron, Miquel B

    2016-05-05

    Atmospheric pressure X-ray photoelectron spectroscopy (XPS) is demonstrated using single-layer graphene membranes as photoelectron-transparent barriers that sustain pressure differences in excess of 6 orders of magnitude. The graphene serves as a support for catalyst nanoparticles under atmospheric pressure reaction conditions (up to 1.5 bar), where XPS allows the oxidation state of Cu nanoparticles and gas phase species to be simultaneously probed. We thereby observe that the Cu(2+) oxidation state is stable in O2 (1 bar) but is spontaneously reduced under vacuum. We further demonstrate the detection of various gas-phase species (Ar, CO, CO2, N2, O2) in the pressure range 10-1500 mbar including species with low photoionization cross sections (He, H2). Pressure-dependent changes in the apparent binding energies of gas-phase species are observed, attributable to changes in work function of the metal-coated grids supporting the graphene. We expect atmospheric pressure XPS based on this graphene membrane approach to be a valuable tool for studying nanoparticle catalysis.

  19. Photoelectron spectroscopy bulk and surface electronic structures

    CERN Document Server

    Suga, Shigemasa

    2014-01-01

    Photoelectron spectroscopy is now becoming more and more required to investigate electronic structures of various solid materials in the bulk, on surfaces as well as at buried interfaces. The energy resolution was much improved in the last decade down to 1 meV in the low photon energy region. Now this technique is available from a few eV up to 10 keV by use of lasers, electron cyclotron resonance lamps in addition to synchrotron radiation and X-ray tubes. High resolution angle resolved photoelectron spectroscopy (ARPES) is now widely applied to band mapping of materials. It attracts a wide attention from both fundamental science and material engineering. Studies of the dynamics of excited states are feasible by time of flight spectroscopy with fully utilizing the pulse structures of synchrotron radiation as well as lasers including the free electron lasers (FEL). Spin resolved studies also made dramatic progress by using higher efficiency spin detectors and two dimensional spin detectors. Polarization depend...

  20. Uncertainty principle for angular position and angular momentum

    International Nuclear Information System (INIS)

    Franke-Arnold, Sonja; Barnett, Stephen M; Yao, Eric; Leach, Jonathan; Courtial, Johannes; Padgett, Miles

    2004-01-01

    The uncertainty principle places fundamental limits on the accuracy with which we are able to measure the values of different physical quantities (Heisenberg 1949 The Physical Principles of the Quantum Theory (New York: Dover); Robertson 1929 Phys. Rev. 34 127). This has profound effects not only on the microscopic but also on the macroscopic level of physical systems. The most familiar form of the uncertainty principle relates the uncertainties in position and linear momentum. Other manifestations include those relating uncertainty in energy to uncertainty in time duration, phase of an electromagnetic field to photon number and angular position to angular momentum (Vaccaro and Pegg 1990 J. Mod. Opt. 37 17; Barnett and Pegg 1990 Phys. Rev. A 41 3427). In this paper, we report the first observation of the last of these uncertainty relations and derive the associated states that satisfy the equality in the uncertainty relation. We confirm the form of these states by detailed measurement of the angular momentum of a light beam after passage through an appropriate angular aperture. The angular uncertainty principle applies to all physical systems and is particularly important for systems with cylindrical symmetry

  1. Instant AngularJS starter

    CERN Document Server

    Menard, Dan

    2013-01-01

    Get to grips with a new technology, understand what it is and what it can do for you, and then get to work with the most important features and tasks. This book is written in an easytoread style, with a strong emphasis on realworld, practical examples. Stepbystep explanations are provided for performing important tasks.This book is for web developers familiar with JavascriptIt doesn't cover the history of AngularJS, and it's not a pitch to convince you that AngularJS is the best framework on the entire web. It's a guide to help you learn everything you need to know about AngularJS in as few pa

  2. Automated Angular Momentum Recoupling Algebra

    Science.gov (United States)

    Williams, H. T.; Silbar, Richard R.

    1992-04-01

    We present a set of heuristic rules for algebraic solution of angular momentum recoupling problems. The general problem reduces to that of finding an optimal path from one binary tree (representing the angular momentum coupling scheme for the reduced matrix element) to another (representing the sub-integrals and spin sums to be done). The method lends itself to implementation on a microcomputer, and we have developed such an implementation using a dialect of LISP. We describe both how our code, called RACAH, works and how it appears to the user. We illustrate the use of RACAH for several transition and scattering amplitude matrix elements occurring in atomic, nuclear, and particle physics.

  3. Wavelength dependent photoelectron circular dichroism of limonene studied by femtosecond multiphoton laser ionization and electron-ion coincidence imaging

    Science.gov (United States)

    Rafiee Fanood, Mohammad M.; Janssen, Maurice H. M.; Powis, Ivan

    2016-09-01

    Enantiomers of the monoterpene limonene have been investigated by (2 + 1) resonance enhanced multiphoton ionization and photoelectron circular dichroism employing tuneable, circularly polarized femtosecond laser pulses. Electron imaging detection provides 3D momentum measurement while electron-ion coincidence detection can be used to mass-tag individual electrons. Additional filtering, by accepting only parent ion tagged electrons, can be then used to provide discrimination against higher energy dissociative ionization mechanisms where more than three photons are absorbed to better delineate the two photon resonant, one photon ionization pathway. The promotion of different vibrational levels and, tentatively, different electronic ion core configurations in the intermediate Rydberg states can be achieved with different laser excitation wavelengths (420 nm, 412 nm, and 392 nm), in turn producing different state distributions in the resulting cations. Strong chiral asymmetries in the lab frame photoelectron angular distributions are quantified, and a comparison made with a single photon (synchrotron radiation) measurement at an equivalent photon energy.

  4. Non-dipole effects in spin polarization of photoelectrons from 3d electrons of Xe, Cs and Ba

    Energy Technology Data Exchange (ETDEWEB)

    Amusia, M Ya [Racah Institute of Physics, Hebrew University, Jerusalem 91904 (Israel); Cherepkov, N A [State University of Aerospace Instrumentation, St. Petersburg 190000 (Russian Federation); Chernysheva, L V [A F Ioffe Physical-Technical Institute, St. Petersburg 194021 (Russian Federation); Felfli, Z [Department of Physics and Center for Theoretical Studies of Physical Systems, Clark Atlanta University, Atlanta GA 30314 (United States); Msezane, A Z [Department of Physics and Center for Theoretical Studies of Physical Systems, Clark Atlanta University, Atlanta GA 30314 (United States)

    2005-04-28

    The non-dipole contribution to spin polarization of photoelectrons from Xe, Cs and Ba 3d{sub 5/2} and 3d{sub 3/2} levels is calculated. The calculation is carried out within the framework of a modified version of the spin-polarized random phase approximation with exchange. The effects of relaxation of excited electrons due to the 3d-vacancy creation are also accounted for. It is demonstrated that the parameters that characterize the photoelectron angular distribution as functions of the incoming photon energy, although being predictably small, acquire additional peculiarities when the interaction between electrons that belong to the 3d{sub 5/2} and 3d{sub 3/2} components of the spin-orbit doublet is taken into account.

  5. Advances in threshold photoelectron spectroscopy (TPES) and threshold photoelectron photoion coincidence (TPEPICO).

    Science.gov (United States)

    Baer, Tomas; Tuckett, Richard P

    2017-04-12

    The history and evolution of molecular threshold photoelectron spectroscopy and threshold photoelectron photoion coincidence spectroscopy (TPEPICO) over the last fifty years are reviewed. Emphasis is placed on instrumentation and the extraction of dynamical information about energy selected ion dissociation, not on the detailed spectroscopy of certain molecules. Three important advances have expanded greatly the power of the technique, and permitted its implementation on modern synchrotron radiation beamlines. The use of velocity focusing of threshold electrons onto an imaging detector in the 1990s simultaneously improved the sensitivity and electron energy resolution, and also facilitated the subtraction of hot electron background in both threshold electron spectroscopy and TPEPICO studies. The development of multi-start multi-stop collection detectors for both electrons and ions in the 2000s permitted the use of the full intensity of modern synchrotron radiation thereby greatly improving the signal-to-noise ratio. Finally, recent developments involving imaging electrons in a range of energies as well as ions onto separate position-sensitive detectors has further improved the collection sensitivity so that low density samples found in a variety of studies can be investigated. As a result, photoelectron photoion coincidence spectroscopy is now well positioned to address a range of challenging problems that include the quantitative determination of compositions of isomer mixtures, and the detection and spectroscopy of free radicals produced in pyrolysis or discharge sources as well as in combustion studies.

  6. X-Ray photoelectron spectroscopic investigation of phenosafranine ...

    Indian Academy of Sciences (India)

    The phenosafranine adsorbed onto the micro and mesoporous materials prepared by ion exchange method and interaction of the dye with host materials were studied by X-ray photoelectron spectroscopy to elucidate the influence of the host matrix on the binding energy of N 1s orbital. Core level N 1s X-ray photoelectron ...

  7. Spectroscopy of transient neutral species via negative ion photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Weaver, A.

    1991-12-01

    Negative ion photoelectron spectroscopy has been used to study two types of transient neutral species: bound free radicals (NO{sub 2} and NO{sub 3}) and unstable neutral species ((IHI) and (FH{sub 2})). The negative ion time-of-flight photoelectron spectrometer used for these experiments is described in detail.

  8. Spectroscopy of transient neutral species via negative ion photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Weaver, Alexandra [Univ. of California, Berkeley, CA (United States)

    1991-12-01

    Negative ion photoelectron spectroscopy has been used to study two types of transient neutral species: bound free radicals (NO2 and NO3) and unstable neutral species ([IHI] and [FH2]). The negative ion time-of-flight photoelectron spectrometer used for these experiments is described in detail.

  9. Tagging multiphoton ionization events by two-dimensional photoelectron spectroscopy

    NARCIS (Netherlands)

    de Groot, Mattijs; Broos, Jaap; Buma, Wybren Jan

    2007-01-01

    Two-dimensional photoelectron spectroscopy has been used to supply process-specific labels to multiphoton ionization events. Employing these tags, the authors can construct excitation and photoelectron spectra along predefined excitation routes in the neutral manifold and ionization routes to the

  10. Photoelectron backscattering from silicon anodes of hybrid photodetector tubes

    CERN Document Server

    D'Ambrosio, C

    2000-01-01

    The impact of photoelectron backscattering on spectral distributions measured with hybrid photodetector tubes has been calculated. The calculations are based on the backscattering coefficient mu , the average number of photoelectrons N/sub phel/ emitted from the photocathode, and on the distribution of the fractional photoelectron energy q absorbed in silicon during the backscattering process. We obtained the following results: the average number of absorbed (measured) photoelectrons N/sub meas/ in the silicon anode amounts to ~88% of the incident N/sub phel/. Photoelectron- and gamma-absorption peaks are broadened by a factor 1.043 due to backscattering. As an example, for photomultiplier tubes, this broadening can amount to an average factor of 1.18 due to statistic and gain fluctuations on the dynode chain. (15 refs).

  11. Photoelectron spectrometer for attosecond spectroscopy of liquids and gases.

    Science.gov (United States)

    Jordan, I; Huppert, M; Brown, M A; van Bokhoven, J A; Wörner, H J

    2015-12-01

    A new apparatus for attosecond time-resolved photoelectron spectroscopy of liquids and gases is described. It combines a liquid microjet source with a magnetic-bottle photoelectron spectrometer and an actively stabilized attosecond beamline. The photoelectron spectrometer permits venting and pumping of the interaction chamber without affecting the low pressure in the flight tube. This pressure separation has been realized through a sliding skimmer plate, which effectively seals the flight tube in its closed position and functions as a differential pumping stage in its open position. A high-harmonic photon spectrometer, attached to the photoelectron spectrometer, exit port is used to acquire photon spectra for calibration purposes. Attosecond pulse trains have been used to record photoelectron spectra of noble gases, water in the gas and liquid states as well as solvated species. RABBIT scans demonstrate the attosecond resolution of this setup.

  12. Ionization, photoelectron dynamics and elastic scattering in relativistic, ultra-strong field

    Science.gov (United States)

    Luo, Sui

    wave-function spread. A relativistic rescattering enhancement occurs at 2 x 1018 W/cm2, commensurate with relativistic motion of a classical electron in a single field cycle. The good comparison between the results with available experiments suggests the theory approach is well suited to modeling scattering in the ultrastrong intensity regime. We investigate the elastic scattering process as it changes from strong to ultrastrong fields with the photoelectron angular distributions from Ne, Ar, and Xe. Noble gas species with Hartree-Fock scattering potentials show a reduction in elastic rescattering with the increasing energy of ultrastrong fields. It is found that as one increases the returning photoelectron energy, rescattering becomes the dominating mechanism behind the yield distribution as the emission angle for all the species extends from 0° to 90°. The relativistic effects and the magnetic field do not change the angular distribution until one is well into the Gamma r "1 regime where the Lorentz defection significantly reduces the yield. As we proceed to the highest energy, the angular emission range narrows as the mechanism changes over to backscattering into narrow angles along the electric field.

  13. Threshold photoelectron spectroscopy of the imidogen radical

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, Gustavo A., E-mail: gustavo.garcia@synchrotron-soleil.fr [Synchrotron SOLEIL, L’Orme des Merisiers, St. Aubin, BP 48, 91192 Gif sur Yvette (France); Gans, Bérenger [Institut des Sciences Moléculaires d’Orsay, Univ Paris-Sud, CNRS, Bât 210, Univ Paris-Sud, 91405 Orsay Cedex (France); Tang, Xiaofeng [Synchrotron SOLEIL, L’Orme des Merisiers, St. Aubin, BP 48, 91192 Gif sur Yvette (France); Ward, Michael; Batut, Sébastien [PC2A, Université de Lille 1, UMR CNRS-USTL 8522, Cité Scientifique Bât. C11, F-59655 Villeneuve d’Ascq (France); Nahon, Laurent [Synchrotron SOLEIL, L’Orme des Merisiers, St. Aubin, BP 48, 91192 Gif sur Yvette (France); Fittschen, Christa [PC2A, Université de Lille 1, UMR CNRS-USTL 8522, Cité Scientifique Bât. C11, F-59655 Villeneuve d’Ascq (France); Loison, Jean-Christophe [ISM, Université de Bordeaux, CNRS, 351 cours de la Libération, 33405 Talence Cedex (France)

    2015-08-15

    We present the threshold photoelectron spectroscopy of the imidogen radical (NH) recorded in the photon energy region up to 1 eV above its first ionization threshold. The radical was produced by reaction of NH{sub 3} and F in a microwave discharge flow-tube and photoionized using vacuum ultraviolet (VUV) synchrotron radiation. A double imaging coincidence spectrometer was used to record mass-selected spectra and avoid contributions from the byproducts present in the reactor and background gas. The energy region includes the ground X{sup +2}Π and first electronically excited a{sup +4}Σ{sup −} states of NH{sup +}. Strong adiabatic transitions and weak vibrational progressions up to v{sup +} = 2 are observed for both electronic states. The rotational profile seen in the origin band has been modeled using existing neutral and cationic spectroscopic constants leading to a precise determination of the adiabatic ionization energy at 13.480 ± 0.002 eV.

  14. Laser photoelectron spectrometry of Sc- and Y-

    International Nuclear Information System (INIS)

    Feigerle, C.S.; Herman, Z.; Lineberger, W.C.

    1981-01-01

    The photoelectron spectra of Sc - and Y - have been obtained in a crossed ion- and laser-beam experiment. Analysis of the Sc - spectrum yields two bound terms of 3d4s 2 4p configuration ( 1 D 0 and 3 D 0 ), with EA(Sc) = 0.189 +- 0.020 eV and an excited-state binding energy of 0.042 +- 0.020 eV. Similarly, the (4d5s 2 5p) 1 D 0 ground state of Y - is bound by 0.308 +- 0.012 eV and a (4d5s 2 5p) 3 D 0 excited term is bound by 0.165 +- 0.025 eV. With the determination of the bound electronic configuration of Sc - as 3d4s 2 4p, the order of filling of electron shells of the first transition series negative ions is found to be 4s 2 ep, 3d4s 2 4p, the order of filling of electron shells of the first transition series negative ions is found to be 4s 2 4p, 3d4s 2 4p, followed by 3dsup(k) 4s 2 (k = 3, 4, ..., 10). (orig.)

  15. MOCCA: A 4k-Pixel Molecule Camera for the Position- and Energy-Resolving Detection of Neutral Molecule Fragments at CSR

    Science.gov (United States)

    Gamer, L.; Schulz, D.; Enss, C.; Fleischmann, A.; Gastaldo, L.; Kempf, S.; Krantz, C.; Novotný, O.; Schwalm, D.; Wolf, A.

    2016-08-01

    We present the design of MOCCA, a large-area particle detector that is developed for the position- and energy-resolving detection of neutral molecule fragments produced in electron-ion interactions at the Cryogenic Storage Ring at the Max Planck Institute for Nuclear Physics in Heidelberg. The detector is based on metallic magnetic calorimeters and consists of 4096 particle absorbers covering a total detection area of 44.8 mathrm {mm} × 44.8 mathrm {mm}. Groups of four absorbers are thermally coupled to a common paramagnetic temperature sensor where the strength of the thermal link is different for each absorber. This allows attributing a detector event within this group to the corresponding absorber by discriminating the signal rise times. A novel readout scheme further allows reading out all 1024 temperature sensors that are arranged in a 32 × 32 square array using only 16+16 current-sensing superconducting quantum interference devices. Numerical calculations taking into account a simplified detector model predict an energy resolution of Δ E_mathrm {FWHM} le 80 mathrm {eV} for all pixels of this detector.

  16. Dose optimization for dual-energy contrast-enhanced digital mammography based on an energy-resolved photon-counting detector: A Monte Carlo simulation study

    Science.gov (United States)

    Lee, Youngjin; Lee, Seungwan; Kang, Sooncheol; Eom, Jisoo

    2017-03-01

    Dual-energy contrast-enhanced digital mammography (CEDM) has been used to decompose breast images and improve diagnostic accuracy for tumor detection. However, this technique causes an increase of radiation dose and an inaccuracy in material decomposition due to the limitations of conventional X-ray detectors. In this study, we simulated the dual-energy CEDM with an energy-resolved photon-counting detector (ERPCD) for reducing radiation dose and improving the quantitative accuracy of material decomposition images. The ERPCD-based dual-energy CEDM was compared to the conventional dual-energy CEDM in terms of radiation dose and quantitative accuracy. The correlation between radiation dose and image quality was also evaluated for optimizing the ERPCD-based dual-energy CEDM technique. The results showed that the material decomposition errors of the ERPCD-based dual-energy CEDM were 0.56-0.67 times lower than those of the conventional dual-energy CEDM. The imaging performance of the proposed technique was optimized at the radiation dose of 1.09 mGy, which is a half of the MGD for a single view mammogram. It can be concluded that the ERPCD-based dual-energy CEDM with an optimal exposure level is able to improve the quality of material decomposition images as well as reduce radiation dose.

  17. Scanning photoelectron microscope for nanoscale three-dimensional spatial-resolved electron spectroscopy for chemical analysis.

    Science.gov (United States)

    Horiba, K; Nakamura, Y; Nagamura, N; Toyoda, S; Kumigashira, H; Oshima, M; Amemiya, K; Senba, Y; Ohashi, H

    2011-11-01

    In order to achieve nondestructive observation of the three-dimensional spatially resolved electronic structure of solids, we have developed a scanning photoelectron microscope system with the capability of depth profiling in electron spectroscopy for chemical analysis (ESCA). We call this system 3D nano-ESCA. For focusing the x-ray, a Fresnel zone plate with a diameter of 200 μm and an outermost zone width of 35 nm is used. In order to obtain the angular dependence of the photoelectron spectra for the depth-profile analysis without rotating the sample, we adopted a modified VG Scienta R3000 analyzer with an acceptance angle of 60° as a high-resolution angle-resolved electron spectrometer. The system has been installed at the University-of-Tokyo Materials Science Outstation beamline, BL07LSU, at SPring-8. From the results of the line-scan profiles of the poly-Si/high-k gate patterns, we achieved a total spatial resolution better than 70 nm. The capability of our system for pinpoint depth-profile analysis and high-resolution chemical state analysis is demonstrated. © 2011 American Institute of Physics

  18. An optimized photoelectron track reconstruction method for photoelectric X-ray polarimeters

    Science.gov (United States)

    Kitaguchi, Takao; Black, Kevin; Enoto, Teruaki; Fukazawa, Yasushi; Hayato, Asami; Hill, Joanne E.; Iwakiri, Wataru B.; Jahoda, Keith; Kaaret, Philip; McCurdy, Ross; Mizuno, Tsunefumi; Nakano, Toshio; Tamagawa, Toru

    2018-02-01

    We present a data processing algorithm for angular reconstruction and event selection applied to 2-D photoelectron track images from X-ray polarimeters. The method reconstructs the initial emission angle of a photoelectron from the initial portion of the track, which is obtained by continuously cutting a track until the image moments or number of pixels fall below tunable thresholds. In addition, event selection which rejects round tracks quantified with eccentricity and circularity is performed so that polarimetry sensitivity considering a trade-off between the modulation factor and signal acceptance is maximized. The modulation factors with applying track selection are 26 . 6 ± 0 . 4, 46 . 1 ± 0 . 4, 62 . 3 ± 0 . 4, and 61 . 8 ± 0 . 3% at 2.7, 4.5, 6.4, and 8.0 keV, respectively, using the same data previously analyzed by Iwakiri et al. (2016), where the corresponding numbers are 26 . 9 ± 0 . 4, 43 . 4 ± 0 . 4, 54 . 4 ± 0 . 3, and 59 . 1 ± 0 . 3%. The method improves polarimeter sensitivity by 5%-10% at the high energy end of the band previously presented (Iwakiri et al. 2016).

  19. On Dunkl angular momenta algebra

    Energy Technology Data Exchange (ETDEWEB)

    Feigin, Misha [School of Mathematics and Statistics, University of Glasgow,15 University Gardens, Glasgow G12 8QW (United Kingdom); Hakobyan, Tigran [Yerevan State University,1 Alex Manoogian, 0025 Yerevan (Armenia); Tomsk Polytechnic University,Lenin Ave. 30, 634050 Tomsk (Russian Federation)

    2015-11-17

    We consider the quantum angular momentum generators, deformed by means of the Dunkl operators. Together with the reflection operators they generate a subalgebra in the rational Cherednik algebra associated with a finite real reflection group. We find all the defining relations of the algebra, which appear to be quadratic, and we show that the algebra is of Poincaré-Birkhoff-Witt (PBW) type. We show that this algebra contains the angular part of the Calogero-Moser Hamiltonian and that together with constants it generates the centre of the algebra. We also consider the gl(N) version of the subalgebra of the rational Cherednik algebra and show that it is a non-homogeneous quadratic algebra of PBW type as well. In this case the central generator can be identified with the usual Calogero-Moser Hamiltonian associated with the Coxeter group in the harmonic confinement.

  20. Phonons with orbital angular momentum

    International Nuclear Information System (INIS)

    Ayub, M. K.; Ali, S.; Mendonca, J. T.

    2011-01-01

    Ion accoustic waves or phonon modes are studied with orbital angular momentum (OAM) in an unmagnetized collissionless uniform plasma, whose constituents are the Boltzmann electrons and inertial ions. For this purpose, we have employed the fluid equations to obtain a paraxial equation in terms of ion density perturbations and discussed its Gaussian beam and Laguerre-Gauss (LG) beam solutions. Furthermore, an approximate solution for the electrostatic potential problem is presented, allowing to express the components of the electric field in terms of LG potential perturbations. The energy flux due to phonons is also calculated and the corresponding OAM is derived. Numerically, it is shown that the parameters such as azimuthal angle, radial and angular mode numbers, and beam waist, strongly modify the profiles of the phonon LG potential. The present results should be helpful in understanding the phonon mode excitations produced by Brillouin backscattering of laser beams in a uniform plasma.

  1. Angular momentum in QGP holography

    Directory of Open Access Journals (Sweden)

    Brett McInnes

    2014-10-01

    Full Text Available The quark chemical potential is one of the fundamental parameters describing the quark–gluon plasma produced by sufficiently energetic heavy-ion collisions. It is not large at the extremely high temperatures probed by the LHC, but it plays a key role in discussions of the beam energy scan programmes at the RHIC and other facilities. On the other hand, collisions at such energies typically (that is, in peripheral collisions give rise to very high values of the angular momentum density. Here we explain that holographic estimates of the quark chemical potential of a rotating sample of plasma can be very considerably improved by taking the angular momentum into account.

  2. Bimolecular reaction dynamics from photoelectron spectroscopy of negative ions

    International Nuclear Information System (INIS)

    Bradforth, S.E.

    1992-11-01

    The transition state region of a neutral bimolecular reaction may be experimentally investigated by photoelectron spectroscopy of an appropriate negative ion. The photoelectron spectrum provides information on the spectroscopy and dynamics of the short lived transition state and may be used to develop model potential energy surfaces that are semi-quantitative in this important region. The principles of bound → bound negative ion photoelectron spectroscopy are illustrated by way of an example: a full analysis of the photoelectron bands of CN - , NCO - and NCS - . Transition state photoelectron spectra are presented for the following systems Br + HI, Cl + HI, F + HI, F + CH 3 0H,F + C 2 H 5 OH,F + OH and F + H 2 . A time dependent framework for the simulation and interpretation of the bound → free transition state photoelectron spectra is subsequently developed and applied to the hydrogen transfer reactions Br + HI, F + OH → O( 3 P, 1 D) + HF and F + H 2 . The theoretical approach for the simulations is a fully quantum-mechanical wave packet propagation on a collinear model reaction potential surface. The connection between the wavepacket time evolution and the photoelectron spectrum is given by the time autocorrelation function. For the benchmark F + H 2 system, comparisons with three-dimensional quantum calculations are made

  3. AngularJS test-driven development

    CERN Document Server

    Chaplin, Tim

    2015-01-01

    This book is for developers who want to learn about AngularJS development by applying testing techniques. You are assumed to have a basic knowledge and understanding of HTML, JavaScript, and AngularJS.

  4. Angular Momentum of Topologically Structured Darkness.

    Science.gov (United States)

    Alperin, Samuel N; Siemens, Mark E

    2017-11-17

    We theoretically analyze and experimentally measure the extrinsic angular momentum contribution of topologically structured darkness found within fractional vortex beams, and show that this structured darkness can be explained by evanescent waves at phase discontinuities in the generating optic. We also demonstrate the first direct measurement of the intrinsic orbital angular momentum of light with both intrinsic and extrinsic angular momentum, and explain why the total orbital angular momenta of fractional vortices do not match the winding number of their generating phases.

  5. Photoelectron spectroscopy of boron aluminum hydride cluster anions

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Haopeng; Zhang, Xinxing; Ko, Yeon Jae; Gantefoer, Gerd; Bowen, Kit H., E-mail: kbowen@jhu.edu, E-mail: kiran@mcneese.edu [Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218 (United States); Li, Xiang [Center for Space Science and Technology, University of Maryland–Baltimore County, Baltimore, Maryland 21250 (United States); Kiran, Boggavarapu, E-mail: kbowen@jhu.edu, E-mail: kiran@mcneese.edu [Department of Chemistry and Physics, McNeese State University, Lake Charles, Louisiana 70609 (United States); Kandalam, Anil K. [Department of Physics, West Chester University, West Chester, Pennsylvania 19383 (United States)

    2014-04-28

    Boron aluminum hydride clusters are studied through a synergetic combination of anion photoelectron spectroscopy and density functional theory based calculations. Boron aluminum hydride cluster anions, B{sub x}Al{sub y}H{sub z}{sup −}, were generated in a pulsed arc cluster ionization source and identified by time-of-flight mass spectrometry. After mass selection, their photoelectron spectra were measured by a magnetic bottle-type electron energy analyzer. The resultant photoelectron spectra as well as calculations on a selected series of stoichiometries reveal significant geometrical changes upon substitution of aluminum atoms by boron atoms.

  6. Photoelectron spectroscopy of boron aluminum hydride cluster anions.

    Science.gov (United States)

    Wang, Haopeng; Zhang, Xinxing; Ko, Yeon Jae; Gantefoer, Gerd; Bowen, Kit H; Li, Xiang; Kiran, Boggavarapu; Kandalam, Anil K

    2014-04-28

    Boron aluminum hydride clusters are studied through a synergetic combination of anion photoelectron spectroscopy and density functional theory based calculations. Boron aluminum hydride cluster anions, BxAlyHz(-), were generated in a pulsed arc cluster ionization source and identified by time-of-flight mass spectrometry. After mass selection, their photoelectron spectra were measured by a magnetic bottle-type electron energy analyzer. The resultant photoelectron spectra as well as calculations on a selected series of stoichiometries reveal significant geometrical changes upon substitution of aluminum atoms by boron atoms.

  7. AngularJS web application development

    CERN Document Server

    Darwin, Peter Bacon

    2013-01-01

    The book will be a step-by-step guide showing the readers how to build a complete web app with AngularJSJavaScript developers who want to learn AngularJS for developing web apps. Knowledge of JavaScript and HTML is expected. No knowledge of AngularJS is required.

  8. Communication: angular momentum alignment and fluorescence polarization of alkali atoms photodetached from helium nanodroplets.

    Science.gov (United States)

    Hernando, Alberto; Beswick, J Alberto; Halberstadt, Nadine

    2013-12-14

    The theory of photofragments angular momentum polarization is applied to the photodetachment of an electronically excited alkali atom from a helium nanocluster (N = 200). The alignment of the electronic angular momentum of the bare excited alkali atoms produced is calculated quantum mechanically by solving the excited states coupled equations with potentials determined by density functional theory (DFT). Pronounced oscillations as a function of excitation energy are predicted for the case of Na@(He)200, in marked contrast with the absorption cross-section and angular distribution of the ejected atoms which are smooth functions of the energy. These oscillations are due to quantum interference between different coherently excited photodetachment pathways. Experimentally, these oscillations should be reflected in the fluorescence polarization and polarization-resolved photoelectron yield of the ejected atoms, which are proportional to the electronic angular momentum alignment. In addition, this result is much more general than the test case of NaHe200 studied here. It should be observable for larger droplets, for higher excited electronic states, and for other alkali as well as for alkali-earth atoms. Detection of these oscillations would show that the widely used pseudo-diatomic model can be valid beyond the prediction of absorption spectra and could help in interpreting parts of the dynamics, as already hinted by some experimental results on angular anisotropy of bare alkali fragments.

  9. Dose optimization for dual-energy contrast-enhanced digital mammography based on an energy-resolved photon-counting detector: A Monte Carlo simulation study

    International Nuclear Information System (INIS)

    Lee, Youngjin; Lee, Seungwan; Kang, Sooncheol; Eom, Jisoo

    2017-01-01

    Dual-energy contrast-enhanced digital mammography (CEDM) has been used to decompose breast images and improve diagnostic accuracy for tumor detection. However, this technique causes an increase of radiation dose and an inaccuracy in material decomposition due to the limitations of conventional X-ray detectors. In this study, we simulated the dual-energy CEDM with an energy-resolved photon-counting detector (ERPCD) for reducing radiation dose and improving the quantitative accuracy of material decomposition images. The ERPCD-based dual-energy CEDM was compared to the conventional dual-energy CEDM in terms of radiation dose and quantitative accuracy. The correlation between radiation dose and image quality was also evaluated for optimizing the ERPCD-based dual-energy CEDM technique. The results showed that the material decomposition errors of the ERPCD-based dual-energy CEDM were 0.56–0.67 times lower than those of the conventional dual-energy CEDM. The imaging performance of the proposed technique was optimized at the radiation dose of 1.09 mGy, which is a half of the MGD for a single view mammogram. It can be concluded that the ERPCD-based dual-energy CEDM with an optimal exposure level is able to improve the quality of material decomposition images as well as reduce radiation dose. - Highlights: • Dual-energy mammography based on a photon-counting detector was simulated. • Radiation dose and image quality were evaluated for optimizing the proposed technique. • The proposed technique reduced radiation dose as well as improved image quality. • The proposed technique was optimized at the radiation dose of 1.09 mGy.

  10. The Electron-Phonon Interaction as Studied by Photoelectron Spectroscopy

    International Nuclear Information System (INIS)

    Lynch, D.W.

    2004-01-01

    With recent advances in energy and angle resolution, the effects of electron-phonon interactions are manifest in many valence-band photoelectron spectra (PES) for states near the Fermi level in metals

  11. Optical angular momentum in classical electrodynamics

    Science.gov (United States)

    Mansuripur, Masud

    2017-06-01

    Invoking Maxwell’s classical equations in conjunction with expressions for the electromagnetic (EM) energy, momentum, force, and torque, we use a few simple examples to demonstrate the nature of the EM angular momentum. The energy and the angular momentum of an EM field will be shown to have an intimate relationship; a source radiating EM angular momentum will, of necessity, pick up an equal but opposite amount of mechanical angular momentum; and the spin and orbital angular momenta of the EM field, when absorbed by a small particle, will be seen to elicit different responses from the particle.

  12. Dependency injection with AngularJS

    CERN Document Server

    Knol, Alex

    2013-01-01

    This book is a practical, hands-on approach to using dependency injection and implementing test-driven development using AngularJS. Dependency Injection with AngularJS is aimed at developers who are aware of AngularJS but need to get started with using it in real life applications. Also, developers who want to get into test-driven development with AngularJS can use this book as practical guide. Even if you know about dependency injection, it can serve as a good reference on how it is used within AngularJS. Readers are expected to have some experience with JavaScript.

  13. Repeatable intensity calibration of an X-ray photoelectron spectrometer

    International Nuclear Information System (INIS)

    Seah, M.P.; Spencer, S.J.

    2006-01-01

    Ten years ago, NPL developed an infrastructure for calibrating the intensity response functions of electron spectrometers for Auger electron and for X-ray photoelectron spectroscopies. Two software systems were developed: one for Auger electron spectrometers or for Auger electron and X-ray photoelectron spectrometers combined, and one for X-ray photoelectron spectrometers on their own; the latter being applied if no suitable electron gun is available. The system for Auger electron and X-ray photoelectron spectrometers combined has been used regularly to calibrate the Metrology Spectrometer II at NPL and experience shows that this gives an instrumental intensity consistency of 0.4% over 10 years. Evaluations have not previously been reported at this level. The system for Auger electron and X-ray photoelectron spectrometers combined is used here in preference to the system solely for X-ray photoelectron spectrometers since it is more robust to the sample condition and can be used over a wider energy range. These issues, and how observed variations in the instrument intensity response may arise, are explained

  14. ChromAIX2: A large area, high count-rate energy-resolving photon counting ASIC for a Spectral CT Prototype

    Science.gov (United States)

    Steadman, Roger; Herrmann, Christoph; Livne, Amir

    2017-08-01

    Spectral CT based on energy-resolving photon counting detectors is expected to deliver additional diagnostic value at a lower dose than current state-of-the-art CT [1]. The capability of simultaneously providing a number of spectrally distinct measurements not only allows distinguishing between photo-electric and Compton interactions but also discriminating contrast agents that exhibit a K-edge discontinuity in the absorption spectrum, referred to as K-edge Imaging [2]. Such detectors are based on direct converting sensors (e.g. CdTe or CdZnTe) and high-rate photon counting electronics. To support the development of Spectral CT and show the feasibility of obtaining rates exceeding 10 Mcps/pixel (Poissonian observed count-rate), the ChromAIX ASIC has been previously reported showing 13.5 Mcps/pixel (150 Mcps/mm2 incident) [3]. The ChromAIX has been improved to offer the possibility of a large area coverage detector, and increased overall performance. The new ASIC is called ChromAIX2, and delivers count-rates exceeding 15 Mcps/pixel with an rms-noise performance of approximately 260 e-. It has an isotropic pixel pitch of 500 μm in an array of 22×32 pixels and is tile-able on three of its sides. The pixel topology consists of a two stage amplifier (CSA and Shaper) and a number of test features allowing to thoroughly characterize the ASIC without a sensor. A total of 5 independent thresholds are also available within each pixel, allowing to acquire 5 spectrally distinct measurements simultaneously. The ASIC also incorporates a baseline restorer to eliminate excess currents induced by the sensor (e.g. dark current and low frequency drifts) which would otherwise cause an energy estimation error. In this paper we report on the inherent electrical performance of the ChromAXI2 as well as measurements obtained with CZT (CdZnTe)/CdTe sensors and X-rays and radioactive sources.

  15. Angular Positioning Sensor for Space Mechanisms

    Science.gov (United States)

    Steiner, Nicolas; Chapuis, Dominique

    2013-09-01

    Angular position sensors are used on various rotating mechanisms such as solar array drive mechanisms, antenna pointing mechanisms, scientific instruments, motors or actuators.Now a days, potentiometers and encoders are mainly used for angular measurement purposes. Both of them have their own pros and cons.As alternative, Ruag Space Switzerland Nyon (RSSN) is developing and qualifying two innovative technologies of angular position sensors which offer easy implementation, medium to very high lifetime and high flexibility with regards to the output signal shape/type.The Brushed angular position sensor uses space qualified processes which are already flying on RSSN's sliprings for many years. A large variety of output signal shape can be implemented to fulfill customer requirements (digital, analog, customized, etc.).The contactless angular position sensor consists in a new radiation hard Application Specific Integrated Circuit (ASIC) based on the Hall effect and providing the angular position without complex processing algorithm.

  16. Oral candidiasis and angular cheilitis.

    Science.gov (United States)

    Sharon, Victoria; Fazel, Nasim

    2010-01-01

    Candidiasis, an often encountered oral disease, has been increasing in frequency. Most commonly caused by the overgrowth of Candida albicans, oral candidiasis can be divided into several categories including acute and chronic forms, and angular cheilitis. Risk factors for the development of oral candidiasis include immunosuppression, wearing of dentures, pharmacotherapeutics, smoking, infancy and old age, endocrine dysfunction, and decreased salivation. Oral candidiasis may be asymptomatic. More frequently, however, it is physically uncomfortable, and the patient may complain of burning mouth, dysgeusia, dysphagia, anorexia, and weight loss, leading to nutritional deficiency and impaired quality of life. A plethora of antifungal treatments are available. The overall prognosis of oral candidiasis is good, and rarely is the condition life threatening with invasive or recalcitrant disease.

  17. Tracking ultrafast relaxation dynamics of furan by femtosecond photoelectron imaging

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yuzhu, E-mail: yuzhu.liu@gmail.com [School of Physics and Optoelectronic Engineering, Nanjing University of Information Science and Technology, Nanjing 210044 (China); Knopp, Gregor [Paul Scherrer Institute, Villigen 5232 (Switzerland); Qin, Chaochao [Department of Physics, Henan Normal University, Xinxiang 453007 (China); Gerber, Thomas [Paul Scherrer Institute, Villigen 5232 (Switzerland)

    2015-01-13

    Graphical abstract: - Highlights: • Relaxation dynamics of furan are tracked by femtosecond photoelectron imaging. • The mechanism for ultrafast formation of α-carbene and β-carbene is proposed. • Ultrafast internal conversion from S{sub 2} to S{sub 1} is observed. • The transient characteristics of the fragment ions are obtained. • Single-color multi-photon ionization dynamics at 800 nm are also studied. - Abstract: Ultrafast internal conversion dynamics of furan has been studied by femtosecond photoelectron imaging (PEI) coupled with photofragmentation (PF) spectroscopy. Photoelectron imaging of single-color multi-photon ionization and two-color pump–probe ionization are obtained and analyzed. Photoelectron bands are assigned to the related states. The time evolution of the photoelectron signal by pump–probe ionization can be well described by a biexponential decay: two rapid relaxation pathways with time constants of ∼15 fs and 85 (±11) fs. The rapid relaxation is ascribed to the ultrafast internal conversion (IC) from the S{sub 2} state to the vibrationally hot S{sub 1} state. The second relaxation process is attributed to the redistributions and depopulation of secondarily populated high vibronic S{sub 1} state and the formation of α-carbene and β-carbene by H immigration. Additionally, the transient characteristics of the fragment ions are also measured and discussed as a complementary understanding.

  18. Tracking ultrafast relaxation dynamics of furan by femtosecond photoelectron imaging

    International Nuclear Information System (INIS)

    Liu, Yuzhu; Knopp, Gregor; Qin, Chaochao; Gerber, Thomas

    2015-01-01

    Graphical abstract: - Highlights: • Relaxation dynamics of furan are tracked by femtosecond photoelectron imaging. • The mechanism for ultrafast formation of α-carbene and β-carbene is proposed. • Ultrafast internal conversion from S 2 to S 1 is observed. • The transient characteristics of the fragment ions are obtained. • Single-color multi-photon ionization dynamics at 800 nm are also studied. - Abstract: Ultrafast internal conversion dynamics of furan has been studied by femtosecond photoelectron imaging (PEI) coupled with photofragmentation (PF) spectroscopy. Photoelectron imaging of single-color multi-photon ionization and two-color pump–probe ionization are obtained and analyzed. Photoelectron bands are assigned to the related states. The time evolution of the photoelectron signal by pump–probe ionization can be well described by a biexponential decay: two rapid relaxation pathways with time constants of ∼15 fs and 85 (±11) fs. The rapid relaxation is ascribed to the ultrafast internal conversion (IC) from the S 2 state to the vibrationally hot S 1 state. The second relaxation process is attributed to the redistributions and depopulation of secondarily populated high vibronic S 1 state and the formation of α-carbene and β-carbene by H immigration. Additionally, the transient characteristics of the fragment ions are also measured and discussed as a complementary understanding

  19. Management of angular cheilitis for children

    Directory of Open Access Journals (Sweden)

    Fajriani Fajriani

    2016-06-01

    Full Text Available Angular cheilitis is one type of oral soft tissue disease that can occur in both children and adults, the condition is characterized by cracks and inflammation in both corners of the mouth. Although this disease does not cause severe disruption but quite disturbing activity and also one's physical appearance. Angular cheilitis light will disappear on their own over time.Severe conditions that can cause pain and bleading. aims to give feedback on peers about managment angular cheilitis in children.

  20. Transverse and longitudinal angular momenta of light

    Energy Technology Data Exchange (ETDEWEB)

    Bliokh, Konstantin Y., E-mail: k.bliokh@gmail.com [Center for Emergent Matter Science, RIKEN, Wako-shi, Saitama 351-0198 (Japan); Nonlinear Physics Centre, RSPhysE, The Australian National University, Canberra, ACT 0200 (Australia); Nori, Franco [Center for Emergent Matter Science, RIKEN, Wako-shi, Saitama 351-0198 (Japan); Physics Department, University of Michigan, Ann Arbor, MI 48109-1040 (United States)

    2015-08-26

    We review basic physics and novel types of optical angular momentum. We start with a theoretical overview of momentum and angular momentum properties of generic optical fields, and discuss methods for their experimental measurements. In particular, we describe the well-known longitudinal (i.e., aligned with the mean momentum) spin and orbital angular momenta in polarized vortex beams. Then, we focus on the transverse (i.e., orthogonal to the mean momentum) spin and orbital angular momenta, which were recently actively discussed in theory and observed in experiments. First, the recently-discovered transverse spin  angular momenta appear in various structured fields: evanescent waves, interference fields, and focused beams. We show that there are several kinds of transverse spin angular momentum, which differ strongly in their origins and physical properties. We describe extraordinary features of the transverse optical spins and overview recent experiments. In particular, the helicity-independent transverse spin inherent in edge evanescent waves offers robust spin–direction coupling at optical interfaces (the quantum spin Hall effect of light). Second, we overview the transverse orbital angular momenta of light, which can be both extrinsic and intrinsic. These two types of the transverse orbital angular momentum are produced by spatial shifts of the optical beams (e.g., in the spin Hall effect of light) and their Lorentz boosts, respectively. Our review is underpinned by a unified theory of the angular momentum of light based on the canonical momentum and spin densities, which avoids complications associated with the separation of spin and orbital angular momenta in the Poynting picture. It allows us to construct a comprehensive classification of all known optical angular momenta based on their key parameters and main physical properties.

  1. Interatomic scattering in energy dependent photoelectron spectra of Ar clusters

    Energy Technology Data Exchange (ETDEWEB)

    Patanen, M.; Benkoula, S.; Nicolas, C.; Goel, A. [Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin, BP 48, 91192 Gif-sur-Yvette Cedex (France); Antonsson, E. [Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin, BP 48, 91192 Gif-sur-Yvette Cedex (France); Physikalische und Theoretische Chemie Institut für Chemie und Biochemie, Fachbereich Biologie, Chemie, Pharmazie, Freie Universität Berlin, Takustrasse 3, 14195 Berlin (Germany); Neville, J. J. [Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin, BP 48, 91192 Gif-sur-Yvette Cedex (France); Department of Chemistry, University of New Brunswick, Fredericton, New Brunswick E3B 6E2 (Canada); Miron, C., E-mail: Catalin.Miron@synchrotron-soleil.fr [Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin, BP 48, 91192 Gif-sur-Yvette Cedex (France); Extreme Light Infrastructure - Nuclear Physics (ELI-NP), ‘Horia Hulubei’ National Institute for Physics and Nuclear Engineering, 30 Reactorului Street, RO-077125 Măgurele, Jud. Ilfov (Romania)

    2015-09-28

    Soft X-ray photoelectron spectra of Ar 2p levels of atomic argon and argon clusters are recorded over an extended range of photon energies. The Ar 2p intensity ratios between atomic argon and clusters’ surface and bulk components reveal oscillations similar to photoelectron extended X-ray absorption fine structure signal (PEXAFS). We demonstrate here that this technique allows us to analyze separately the PEXAFS signals from surface and bulk sites of free-standing, neutral clusters, revealing a bond contraction at the surface.

  2. What can we Learn on Gas Phase Chiral Compounds by Photoelectron Circular Dichroism ?

    Science.gov (United States)

    Nahon, Laurent

    2017-06-01

    Since 15 years, a new type of chiroptical effect has been the subject of a large array of both theoretical and experimental studies: Photoelectron Circular Dichroism (PECD) in the angular distribution of photoelectrons produced by CPL-ionization of pure enantiomers in the gas phase observed as a very intense (up to 35 %) forward/backward asymmetry with respect to the photon axis and which reveals the chirality of the molecule (configuration). PECD happens to be an orbital-specific, photon energy dependent effect and is a very subtle probe of the molecular potential being very sensitive to static molecular structures such as conformers, chemical substitution, clusters, as well as to vibrational motion, much more so than other observables in photoionization such as the cross section or the β asymmetry parameter (for a recent review see L. Nahon, G. A. Garcia, and I. Powis, J. Elec. Spec. Rel. Phen. 204, 322 (2015)). Therefore PECD studies have both a fundamental interest as well and analytical interest, especially since chiral species are ubiquitous in the biosphere, food and medical industry. This last aspect is probably the driving force for the recent extension of PECD studies by the laser community using UV REMPI schemes. After a large introduction to the PECD process itself, and a description of our double imaging electron/ion coincidence set-up, several recent results on one-photon VUV PECD will be presented, including: - Sensitivity to chemical substitutions, isomerism and conformation - Case of floppy biomolecules such as amino acids alanine and proline with a conformer analysis and possible consequences for the origin of life's homochirality - Analytical capabilities in terms of enantiomeric excess determination on a pure molecule as well as on a mixture of compounds. Future trends for PECD studies will be given regarding the case of more complex/structured chiral systems as well as opportunities for time-resolved PECD opened by the recent first performance

  3. An experimental and theoretical study of the valence shell photoelectron spectrum of tetrafluoromethane

    International Nuclear Information System (INIS)

    Holland, D.M.P.; Potts, A.W.; Trofimov, A.B.; Breidbach, J.; Schirmer, J.; Feifel, R.; Richter, T.; Godehusen, K.; Martins, M.; Tutay, A.; Yalcinkaya, M.; Al-Hada, M.; Eriksson, S.; Karlsson, L.

    2005-01-01

    The complete valence shell photoelectron spectrum of tetrafluoromethane has been recorded using synchrotron radiation and the observed structure has been interpreted using ionisation energies and relative spectral intensities computed using the third-order algebraic-diagrammatic-construction (ADC(3)) scheme for the one-particle Green's function and the outer valence Green's function (OVGF) method. The ADC(3) calculations were performed using both the original variant based on the Dyson equation and the recently proposed non-Dyson scheme. The theoretical predictions for the single-hole ionic states due to outer valence shell ionisation agree satisfactorily with the experimental results. Ionisation from the inner valence 2t 2 and 3a 1 orbitals is strongly influenced by reorganisation effects and the intensity is spread amongst numerous satellites. Highly resolved spectra have been measured for the C∼2T2 and the D∼2A1 states, and the vibrational structure has been associated primarily with excitation of the ν1+(a1) mode. However, the analyses also provide evidence for excitation of the Jahn-Teller active ν2+(e) mode in the C∼2T2 state, and the ν3+(t2) mode in the D∼2A1 state. Excitation of this latter mode can be explained in terms of vibronic coupling between the C∼2T2 and the D∼2A1 states. Photoelectron angular distributions and branching ratios have been determined and demonstrate that shape resonances affect the outer valence shell photoionisation dynamics. The experimental results are compared with previous theoretical predictions but a consistent interpretation has not been obtained. The major difficulty concerns the uncertainty in the locations of valence shell transitions into the 5a 1 and the 5t 2 virtual orbitals

  4. An experimental and theoretical study of the valence shell photoelectron spectrum of tetrafluoromethane

    Science.gov (United States)

    Holland, D. M. P.; Potts, A. W.; Trofimov, A. B.; Breidbach, J.; Schirmer, J.; Feifel, R.; Richter, T.; Godehusen, K.; Martins, M.; Tutay, A.; Yalcinkaya, M.; Al-Hada, M.; Eriksson, S.; Karlsson, L.

    2005-01-01

    The complete valence shell photoelectron spectrum of tetrafluoromethane has been recorded using synchrotron radiation and the observed structure has been interpreted using ionisation energies and relative spectral intensities computed using the third-order algebraic-diagrammatic-construction (ADC(3)) scheme for the one-particle Green's function and the outer valence Green's function (OVGF) method. The ADC(3) calculations were performed using both the original variant based on the Dyson equation and the recently proposed non-Dyson scheme. The theoretical predictions for the single-hole ionic states due to outer valence shell ionisation agree satisfactorily with the experimental results. Ionisation from the inner valence 2t 2 and 3a 1 orbitals is strongly influenced by reorganisation effects and the intensity is spread amongst numerous satellites. Highly resolved spectra have been measured for the C˜2T2 and the D˜2A1 states, and the vibrational structure has been associated primarily with excitation of the ν1+(a1) mode. However, the analyses also provide evidence for excitation of the Jahn-Teller active ν2+(e) mode in the C˜2T2 state, and the ν3+(t2) mode in the D˜2A1 state. Excitation of this latter mode can be explained in terms of vibronic coupling between the C˜2T2 and the D˜2A1 states. Photoelectron angular distributions and branching ratios have been determined and demonstrate that shape resonances affect the outer valence shell photoionisation dynamics. The experimental results are compared with previous theoretical predictions but a consistent interpretation has not been obtained. The major difficulty concerns the uncertainty in the locations of valence shell transitions into the 5a 1 and the 5t 2 virtual orbitals.

  5. Angular momentum transfer in incomplete fusion

    Indian Academy of Sciences (India)

    fusion reactions. The angular momentum of the intermediate nucleus formed in incomplete fusion was deduced from the isomeric cross-section ratio by considering the statistical de- excitation of the incompletely fused composite nucleus. The data show that incomplete fusion is associated with angular momenta slightly ...

  6. Responsive web design with AngularJS

    CERN Document Server

    Patel, Sandeep Kumar

    2014-01-01

    If you are an AngularJS developer who wants to learn about responsive web application development, this book is ideal for you. Responsive Web Design with AngularJS is intended for web developers or designers with a basic knowledge of HTML, CSS, and JavaScript.

  7. Angular momentum transfer in incomplete fusion

    Indian Academy of Sciences (India)

    The angular momentum of the intermediate nucleus formed in incomplete fusion was deduced from the isomeric cross-section ratio by considering the statistical de-excitation of the incompletely fused composite nucleus. The data show that incomplete fusion is associated with angular momenta slightly smaller than critical ...

  8. Accelerated rotation with orbital angular momentum modes

    CSIR Research Space (South Africa)

    Schulze, C

    2015-04-01

    Full Text Available A 91, 043821 (2015) Accelerated rotation with orbital angular momentum modes Christian Schulze, Filippus S. Roux, Angela Dudley, Ronald Rop, Michael Duparr´e, and Andrew Forbes Abstract: We introduce a class of light field that angularly...

  9. Dijet angular distributions at D0

    International Nuclear Information System (INIS)

    Fatyga, M.K.

    1996-09-01

    Measurements of the dijet angular distributions are relatively insensitive to parton distribution functions and thus offer an excellent method of testing the LO and NLO predictions of perturbative QCD. The authors present measurements of the dijet angular distributions for |η| < 3.0 in p anti p collisions at √s = 1.8 TeV

  10. Experimental determination of high angular momentum states

    International Nuclear Information System (INIS)

    Barreto, J.L.V.

    1985-01-01

    The current knowledge of the atomic nucleus structure is summarized. A short abstract of the nuclear properties at high angular momentum and a more detailed description of the experimental methods used in the study of high angular momenta is made. (L.C.) [pt

  11. Concepts of radial and angular kinetic energies

    DEFF Research Database (Denmark)

    Dahl, Jens Peder; Schleich, W.P.

    2002-01-01

    We consider a general central-field system in D dimensions and show that the division of the kinetic energy into radial and angular parts proceeds differently in the wave-function picture and the Weyl-Wigner phase-space picture, Thus, the radial and angular kinetic energies are different quantities...

  12. Perturbed angular correlations and distributions

    International Nuclear Information System (INIS)

    Makaryunas, K.

    1976-01-01

    The present index comprises original works and review papers on the perturbed angular correlations (PAC) and distributions (PAD). The articles published in the Soviet and foreign journals as well as the materials of conferences, monographs and collections published in the USSR and abroad, the preprints produced by various institutes and abstracts of disertations are included from 1948 up to 1973. The whole material compiled in this index is divided into three parts. Part one is a bibliographic index. All papers in this part are divided into three sections. Section one comprises the papers devoted to the theoretical works on PAC, review papers, monographs, materials of conferences. Section two deals with the works of methodical character where correlation spectrometers as well as the treatment of experimental data are described. In section three experimental works with concrete nuclei are compiled. Part two gives the characteristic of works performed with concrete nuclei. This part is presented in the form of the table in which the works are systematized according to the chemical elements and isotopes. The table shows the characteristics of the nuclear levels used in the investigations by PAC as well as brief characteristics of experiments and results obtained. Part three - appendix contains alphabetic index of the authors, the list of the used editions with the abbreviations of the titles of these editions. The lists indicating the dynamic of the quantity of works on PAC and the distribution according to the literature sources are also given

  13. Investigation of the SiO2/Si(1 0 0) interface structure by means of angle-scanned photoelectron spectroscopy and diffraction

    International Nuclear Information System (INIS)

    Dreiner, S.; Schuermann, M.; Westphal, C.

    2004-01-01

    The local environment of Si at the interface between a thermally grown SiO 2 film and Si(1 0 0) was studied by angle-scanned photoelectron spectroscopy and diffraction. Si 2p core-level spectra containing chemically shifted components were recorded. These components were deconvoluted by least squares fitting and assigned to different Si oxidation states. The angular dependence of the photoelectron intensity was obtained from the least squares fit results. A simple statistical model was developed to describe the population and depth distribution of the different suboxide species. Using a simple electron attenuation scheme we can simulate the photoemission polar angle dependence of the various Si oxidation states within the model. The fitting of these model curves to the experimental data results in parameters which indicate a Si-O-Si bridge-bonded interface structure

  14. Photoelectron diffraction and holography: Present status and future prospects

    Energy Technology Data Exchange (ETDEWEB)

    Fadley, C.S. [California Univ., Davis, CA (United States). Dept. of Physics]|[Lawrence Berkeley Lab., CA (United States); Thevuthasan, S. [California Univ., Davis, CA (United States). Dept. of Physics; Kaduwela, A.P. [Lawrence Berkeley Lab., CA (United States)] [and others

    1993-07-01

    Photoelectron diffraction and photoelectron holography, a newly developed variant of it, can provide a rich range of information concerning surface structure. These methods are sensitive to atomic type, chemical state, and spin state. The theoretical prediction of diffraction patterns is also well developed at both the single scattering and multiple scattering levels, and quantitative fits of experiment to theory can lead to structures with accuracies in the {plus_minus}0.03 {Angstrom} range. Direct structural information can also be derived from forward scattering in scanned-angle measurements at higher energies, path length differences contained in scanned-energy data at lower energies, and holographic inversions of data sets spanning some region in angle and energy space. Diffraction can also affect average photoelectron emission depths. Circular dichroism in core-level emission can be fruitfully interpreted in terms of photoelectron diffraction theory, as can measurements with spin-resolved core-spectra, and studies of surface magnetic structures and phase transitions should be possible with these methods. Synchrotron radiation is a key element of fully utilizing these techniques.

  15. X-ray photoelectron spectroscopy (XPS) studies of rhenium catalyst

    International Nuclear Information System (INIS)

    Mohd Ambar Yarmo; Che Seman Mahmood

    2000-01-01

    Rhenium oxide on alumina (Re 2 O 7 /Al 2 O 3 ) is a very active catalyst system for olefin metathesis reaction. The catalyst can be prepared by wet impregnation of ammonium perrhenate (NH 4 ReO 4 ) solution onto alumina (γ-AI 2 O 3 ) support followed by drying and calcination in air. In this study, rhenium catalysts at different treatment conditions namely active, non-active and during propylene metathesis reaction were investigated using X-ray photoelectron spectroscopy (XPS) technique. Analysis of O 1s , photoelectron peak shows that some chemical interaction between rhenium oxides and the support have been established through Re-O-Al linkage. Analysis of Re 4f7/2 photoelectron peak by using a systematic deconvolution procedure, shows that the metal was in a mixed and varied oxidation states from Re(IV) to Re(VII) depending on their treatment condition. The presence of the metal-carbene complex, the reaction intermediate, could possibly be observed by analysing the C 1s , photoelectron peak. However, a much higher vacuum (i.e. 10 -10 - 10 -11 torr) is needed in the spectroscopy system in order to have the improved detection sensitivity. (Author)

  16. Graphene defect formation by extreme ultraviolet generated photoelectrons

    NARCIS (Netherlands)

    Gao, An; Lee, Christopher James; Bijkerk, Frederik

    2014-01-01

    We have studied the effect of photoelectrons on defect formation in graphene during extreme ultraviolet (EUV) irradiation. Assuming the major role of these low energy electrons, we have mimicked the process by using low energy primary electrons. Graphene is irradiated by an electron beam with energy

  17. Langmuir Wave Instability And Photoelectron Emission In Irradiated ...

    African Journals Online (AJOL)

    We have investigated dust charged fluctuation due to the combined effect of Langmuir Wave and Photoelectron Emission in Irradiated Dusty Plasma. The dispersion relation and growth of the Langmuir wave instability is also presented. The applicability of the developed dispersion relation and growth rate of the Langmuir ...

  18. The PhotoElectron Boundary as observed by MAVEN instruments

    Science.gov (United States)

    Garnier, P.; Steckiewicz, M.; Mazelle, C. X.; Xu, S.; Mitchell, D. L.; Holmberg, M.; Halekas, J. S.; Andersson, L.; Brain, D.; Connerney, J. E. P.; Espley, J. R.; Lillis, R. J.; Luhmann, J. G.; Savaud, J. A.; Jakosky, B. M.

    2017-12-01

    Photoelectron peaks in the 20-30 eV energy range are commonly observed in planetary atmospheres (Earth, Mars, Titan...), produced by the intense photoionization from solar 30.4 nm photons. At Mars, these photoelectrons result from the ionization of CO2 and O atmospheric neutrals, and are known to escape the planet down its tail, making them tracers for the atmospheric escape (Frahm et al., 2006). Furthermore, their presence or absence allows us to define the so-called PhotoElectron Boundary (PEB), that separates the sunlit photoelectron-dominated ionosphere from the solar wind controlled environment, as initially observed by the Mars Global Surveyor (MGS) MAG/ER instrument (Mitchell et al. (2000, 2001). We provide here a detailed statistical analysis of the location and properties of the PEB based on the Mars Atmosphere and Volatile Evolution (MAVEN) mission electron and magnetic field data. Our dataset includes 1696 dayside PEB crossings obtained from September 2014 until May 2016 (the observations of escaping photoelectrons in the wake being not included). The PEB appears as mostly sensitive to the solar wind dynamic and crustal magnetic fields pressures, for which a quantitative dependance is derived and compared with two other important boundaries : the bow shock and magnetic pileup boundary. The PEB altitude is highly variable, leading to a variable wake cross section for escape (up to +- 50%), which is important for deriving global escape rates from in situ photoelectron escape rates. The PEB is not always sharp, and is, despite a strong variability, characterized on average by : a magnetic field topology typical for the edge of the Magnetic Pile Up Region above it, more field aligned fluxes above than below, and a clear change of the altitude dependence of both electron fluxes and total density (that appears different from the ionopause). The PEB thus appears as a transition region between two plasma and field configurations which is determined by the

  19. Simulation of photoelectric X-ray polarimetry and reconstruction of the photoelectron azimuthal angle

    International Nuclear Information System (INIS)

    Wang Shuo; Ji Jianfeng; Han Dong; Feng Hua

    2013-01-01

    Sensitive X-ray polarimetry in the keV energy range can be achieved by measuring the azimuthal angle distribution of emitted electrons after the photoelectric absorption of X-rays in a micropattern gas detector. However, the initial direction of the electron is not readily measurable due to the randomization of its motion during energy loss. By using the Geant4, Maxwell and Garfield packages, we simulated the detected electron tracks following photoelectric absorption, electron drift and diffusion in the gas, and proposed a technique capable of reconstructing the initial direction of the emitted photoelectron. The technique allows us to measure the angular modulation of flux predicted for a polarized X-ray beam. We calculated the modulation factors in 2-10 keV with a gas mixture of neon and CO 2 , and discussed how electron diffusion along the drift will dilute the track and suppress the modulation. These results are useful for the design of the X-ray polarimeter. (authors)

  20. Radiofrequency encoded angular-resolved light scattering

    DEFF Research Database (Denmark)

    Buckley, Brandon W.; Akbari, Najva; Diebold, Eric D.

    2015-01-01

    The sensitive, specific, and label-free classification of microscopic cells and organisms is one of the outstanding problems in biology. Today, instruments such as the flow cytometer use a combination of light scatter measurements at two distinct angles to infer the size and internal complexity...... of cells at rates of more than 10,000 per second. However, by examining the entire angular light scattering spectrum it is possible to classify cells with higher resolution and specificity. Current approaches to performing these angular spectrum measurements all have significant throughput limitations...... Encoded Angular-resolved Light Scattering (REALS), this technique multiplexes angular light scattering in the radiofrequency domain, such that a single photodetector captures the entire scattering spectrum from a particle over approximately 100 discrete incident angles on a single shot basis. As a proof...

  1. Optical communication beyond orbital angular momentum

    CSIR Research Space (South Africa)

    Trichili, A

    2016-06-01

    Full Text Available Mode division multiplexing (MDM) is mooted as a technology to address future bandwidth issues, and has been successfully demonstrated in free space using spatial modes with orbital angular momentum (OAM). To further increase the data transmission...

  2. Dynamical Model of Fission Fragment Angular Distribution

    Science.gov (United States)

    Drozdov, V. A.; Eremenko, D. O.; Fotina, O. V.; Platonov, S. Yu.; Yuminov, O. A.; Giardina, G.; Taccone, A.

    2002-01-01

    A dynamical model of fission fragment angular distributions is suggested. The model allows one to calculate fission fragment angular distributions, prescission light particle multyplicities, evaporation residue cross sections etc. for the cases of decay of hot and rotating heavy nuclei. The experimental data on angular anisotropies of fission fragments and prescission neutron multiplicities are analyzed for the 16O + 208Pb, 232Th, 248Cm and 238U reactions at the energies of the incident 16O ions ranging from 90 to 160 MeV. This analysis allows us to extract both the nuclear friction coefficient value and the relaxation time for the tilting mode. It is also demonstrated that the angular distributions are sensitive to the deformation dependence of the nuclear friction.

  3. Amplitude damping channel for orbital angular momentum

    CSIR Research Space (South Africa)

    Dudley, Angela L

    2010-03-01

    Full Text Available Since the pioneering work on the entanglement of the orbital angular momentum (OAM) states of light, much attention has been devoted to the subject, with particular attention into the quantum aspects of information processing using OAM. Furthermore...

  4. Mastering AngularJD for .NET developers

    CERN Document Server

    Majid, Mohammad Wadood

    2015-01-01

    This book is envisioned for traditional developers and programmers who want to develop client-side applications using the AngularJS framework and ASP.NET Web API 2 with Visual Studio. .NET developers who have already built web applications or web services and who have a fundamental knowledge of HTML, JavaScript, and CSS and want to explore single-page applications will also find this guide useful. Basic knowledge of AngularJS would be helpful.

  5. Enantioselective femtosecond laser photoionization spectrometry of limonene using photoelectron circular dichroism

    NARCIS (Netherlands)

    Rafiee Fanood, M.M.; Janssen, M.H.M.; Powis, I.

    2015-01-01

    Limonene is ionized by circularly polarized 420 nm femtosecond laser pulses. Ion mass and photoelectron energy spectra identify the dominant (2 + 1) multiphoton ionization mechanism, aided by TDDFT calculations of the Rydberg excitations. Photoelectron circular dichroism measurements on pure

  6. Effect of plasma instability on F region photoelectron distributions

    International Nuclear Information System (INIS)

    Bloomberg, H.W.

    1975-01-01

    Ionospheric suprathermal photoelectrons have relatively large cross sections for selected energies. In particular, electrons with energies of about 2.5 eV strongly excite nitrogen vibrational modes, while metastable states of oxygen are excited at about 5 eV. Thus an energy distribution based on chemical kinetic considerations gives rise to a maximum at around 4 eV in the F region below 250 km. However, rocket experiments have shown that the expected peaks in the flux spectrum are relatively weak. This discrepancy is explained by the development of a linear instability leading to a wave-particle interaction. the linear mode is driven by the photoelectrons near the 4-eV maximum in the presence of a magnetic field. The effect is shown to be ineffective at sufficiently low altitudes, where collisionless theory fails

  7. Effect of plasma instability on F region photoelectron distributions

    International Nuclear Information System (INIS)

    Bloomberg, H.W.

    1975-01-01

    Ionospheric suprathermal photoelectrons have relatively large cross sections for selected energies. In particular, electrons with energies of about 2.5 eV strongly excite nitrogen vibrational modes, while metastable states of oxygen are excited at about 5 eV. Thus an energy distribution based on chemical kinetic considerations give rise to a maximum at around 4 eV in the F region below 250 km. However, rocket experiments have shown that the expected peaks in the flux spectrum are relatively weak. This discrepancy is explained by the development of a linear instability leading to a wave-particle interaction. The linear mode is driven by the photoelectrons near the 4-eV maximum in the presence of a magnetic field. The effect is shown to be ineffective at sufficiently low altitudes, where collisionless theory fails. (auth)

  8. High resolution photoelectron spectroscopy of clusters of Group V elements

    International Nuclear Information System (INIS)

    Wang, Lai-sheng; Niu, B.; Lee, Y.T.; Shirley, D.A.

    1989-07-01

    High resolution HeI (580 angstrom) photoelectron spectra of As 2 , As 4 , and P 4 were obtained with a newly-built high temperature molecular beam source. Vibrational structure was resolved in the photoelectron spectra of the three cluster species. The Jahn-Teller effect is discussed for the 2 E and 2 T 2 states of P 4 + and As 4 + . As a result of the Jahn-Teller effect, the 2 E state splits into two bands, and the 2 T 2 state splits into three bands, in combination with the spin-orbit effect. It was observed that the ν 2 normal vibrational mode was involved in the vibronic interaction of the 2 E state, while both the ν 2 and ν 3 modes were active in the 2 T 2 state. 26 refs., 5 figs., 3 tabs

  9. Photoelectron spectroscopy via electronic spectroscopy of molecular ions

    International Nuclear Information System (INIS)

    Khan, Z.H.

    1990-01-01

    In this work, a new aspect of the correlation between optical and photoelectron spectra is discussed on the basis of which the first ionization potentials of condensed-ring aromatics can be estimated from certain features in the electronic spectra of their positive ions. Furthermore, it is noticed that the first IP's are very sensitive to molecular size as the latter's inclusion in the regression formulas improves the results considerably. Once the first ionization potential for a molecule is determined, its higher IP's may be computed if the lower-energy electronic bands for its cation are known. This procedure is especially useful for such systems whose uv photoelectron spectra are unknown. (author). 11 refs, 10 figs, 1 tab

  10. Molecular photoelectron holography with circularly polarized laser pulses.

    Science.gov (United States)

    Yang, Weifeng; Sheng, Zhihao; Feng, Xingpan; Wu, Miaoli; Chen, Zhangjin; Song, Xiaohong

    2014-02-10

    We investigate the photoelectron momentum distribution of molecular-ion H2+driven by ultrashort intense circularly polarized laser pulses. Both numerical solutions of the time-dependent Schrödinger equation (TDSE) and a quasiclassical model indicate that the photoelectron holography (PH) with circularly polarized pulses can occur in molecule. It is demonstrated that the interference between the direct electron wave and rescattered electron wave from one core to its neighboring core induces the PH. Moreover, the results of the TDSE predict that there is a tilt angle between the interference pattern of the PH and the direction perpendicular to the molecular axis. Furthermore, the tilt angle is sensitively dependent on the wavelength of the driven circularly polarized pulse, which is confirmed by the quasiclassical calculations. The PH induced by circularly polarized laser pulses provides a tool to resolve the electron dynamics and explore the spatial information of molecular structures.

  11. Partial angular coherence and the angular Schmidt spectrum of entangled two-photon fields

    Energy Technology Data Exchange (ETDEWEB)

    Jha, Anand Kumar; Boyd, Robert W. [Institute of Optics, University of Rochester, Rochester, New York 14627 (United States); Agarwal, Girish S. [Department of Physics, Oklahoma State University, Stillwater, Oklahoma 74078 (United States)

    2011-12-15

    We study partially coherent fields that have a coherent-mode representation in the orbital-angular-momentum-mode basis. For such fields, we introduce the concepts of the angular coherence function and the coherence angle. Such fields are naturally produced by the process of parametric down-conversion--a second-order nonlinear optical process in which a pump photon breaks up into two entangled photons, known as the signal and idler photons. We show that the angular coherence functions of the signal and idler fields are directly related to the angular Schmidt (spiral) spectrum of the down-converted two-photon field and thus that the angular Schmidt spectrum can be measured directly by measuring the angular coherence function of either the signal or the idler field, without requiring coincidence detection.

  12. Photoelectron spectroscopic study of carbon aluminum hydride cluster anions

    Science.gov (United States)

    Zhang, Xinxing; Wang, Haopeng; Ganteför, Gerd; Eichhorn, Bryan W.; Kiran, Boggavarapu; Bowen, Kit H.

    2016-10-01

    Numerous previously unknown carbon aluminum hydride cluster anions were generated in the gas phase, identified by time-of-flight mass spectrometry and characterized by anion photoelectron spectroscopy, revealing their electronic structure. Density functional theory calculations on the CAl5-9H- and CAl5-7H2- found that several of them possess unusually high carbon atom coordination numbers. These cluster compositions have potential as the basis for new energetic materials.

  13. Photoelectron spectra and biological activity of cinnamic acid derivatives revisited

    Science.gov (United States)

    Novak, Igor; Klasinc, Leo; McGlynn, Sean P.

    2018-01-01

    The electronic structures of several derivatives of cinnamic acid have been studied by UV photoelectron spectroscopy (UPS) and Green's function quantum chemical calculations. The spectra reveal the presence of dimers in the gas phase for p-coumaric and ferulic acids. The electronic structure analysis has been related to the biological properties of these compounds through the analysis of some structure-activity relationships (SAR).

  14. Imaging photoelectron photoion coincidence spectroscopy with velocity focusing electron optics

    International Nuclear Information System (INIS)

    Bodi, Andras; Johnson, Melanie; Gerber, Thomas; Gengeliczki, Zsolt; Sztaray, Balint; Baer, Tomas

    2009-01-01

    An imaging photoelectron photoion coincidence spectrometer at the vacuum ultraviolet (VUV) beamline of the Swiss Light Source is presented and a few initial measurements are reported. Monochromatic synchrotron VUV radiation ionizes the cooled or thermal gas-phase sample. Photoelectrons are velocity focused, with better than 1 meV resolution for threshold electrons, and also act as start signal for the ion time-of-flight analysis. The ions are accelerated in a relatively low, 40-80 V cm -1 field, which enables the direct measurement of rate constants in the 10 3 -10 7 s -1 range. All electron and ion events are recorded in a triggerless multiple-start/multiple-stop setup, which makes it possible to carry out coincidence experiments at >100 kHz event frequencies. As examples, the threshold photoelectron spectrum of the argon dimer and the breakdown diagrams for hydrogen atom loss in room temperature methane and the chlorine atom loss in cold chlorobenzene are shown and discussed.

  15. Transverse angular momentum in topological photonic crystals

    Science.gov (United States)

    Deng, Wei-Min; Chen, Xiao-Dong; Zhao, Fu-Li; Dong, Jian-Wen

    2018-01-01

    Engineering local angular momentum of structured light fields in real space enables applications in many fields, in particular, the realization of unidirectional robust transport in topological photonic crystals with a non-trivial Berry vortex in momentum space. Here, we show transverse angular momentum modes in silicon topological photonic crystals when considering transverse electric polarization. Excited by a chiral external source with either transverse spin angular momentum or transverse phase vortex, robust light flow propagating along opposite directions is observed in several kinds of sharp-turn interfaces between two topologically-distinct silicon photonic crystals. A transverse orbital angular momentum mode with alternating phase vortex exists at the boundary of two such photonic crystals. In addition, unidirectional transport is robust to the working frequency even when the ring size or location of the pseudo-spin source varies in a certain range, leading to the superiority of the broadband photonic device. These findings enable one to make use of transverse angular momentum, a kind of degree of freedom, to achieve unidirectional robust transport in the telecom region and other potential applications in integrated photonic circuits, such as on-chip robust delay lines.

  16. Angular distribution of oriented nucleus fission neutrons

    International Nuclear Information System (INIS)

    Barabanov, A.L.; Grechukhin, D.P.

    1982-01-01

    Calculations of anisotropy of angular distribution of oriented 235 U nuclei thermal fission neutrons have been carried out. the neutrons were assumed to evaporate isotropically by completely accelerated fragements in the fragment system with only its small part, i. e. fission-producing neutrons, emitted at the moment of neck break. It has been found out that at low energies of neutrons Esub(n)=1-2 MeV the sensitivity of the angular distribution anisotropy to variations of spectrum of neutron evaporation from fragments and the magnitude of a share of fission-producing neutrons reaches approximately 100%, which at high energies, Esub(n) > 5 MeV it does not exceed approximately 20%. Therefore the angular distribution of fast neutrons to a greater degree of confidence may be used for restoring the angular distribution anisotropy of fragments while the angular distribution of low energy neutrons may be used for deriving information on the fission process, but only in case 6f the experiment accuracy is better than approximately 3%

  17. Angular Spectral Analysis and Lowpass Filtering of Aeromagnetic ...

    African Journals Online (AJOL)

    Total-field aeromagnetic data over the western half of the Bornu basin and its surrounding areas were analyzed using angular spectral analysis, upward continuation and lowpass filtering techniques. Results revealed several angular spectral peaks at various angular orientations. The angular orientations correlated with the ...

  18. Data-oriented development with AngularJS

    CERN Document Server

    Waikar, Manoj

    2015-01-01

    This book helps beginner-level AngularJS developers organize AngularJS applications by discussing important AngularJS concepts and best practices. If you are an experienced AngularJS developer but haven't written directives or haven't created custom HTML controls before, then this book is ideal for you.

  19. Angular distributions of electrons photoemitted from core levels of oriented diatomic molecules: multiple scattering theory in non-spherical potentials

    Energy Technology Data Exchange (ETDEWEB)

    Diez Muino, R. [Donostia International Physics Center (DIPC), San Sebastian (Spain) and Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA (United States)]. E-mail: rdm@sc.ehu.es; Rolles, D. [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA (United States); Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin (Germany); Garcia de Abajo, F.J. [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA (United States); Centro Mixto CSIC-UPV/EHU, San Sebastian (Spain); Fadley, C.S. [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA (United States); Department of Physics, University of California at Davis, Davis, CA (United States); Van Hove, M.A. [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA (United States); Department of Physics, University of California at Davis, Davis, CA (United States); Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA (United States)

    2002-08-14

    We use multiple scattering in non-spherical potentials (MSNSP) to calculate the angular distributions of electrons photoemitted from the 1s shells of CO and N{sub 2} gas-phase molecules with fixed-in-space orientations. For low photoelectron kinetic energies (E<50 eV), as appropriate to certain shape resonances, the electron scattering must be represented by non-spherical scattering potentials, which are naturally included in our formalism. Our calculations accurately reproduce the experimental angular patterns recently measured by several groups, including those at the shape-resonance energies. The MSNSP theory is thus an efficient method to calculate the scattering states of low-energy electrons in small low-symmetry systems. (author). Letter-to-the-editor.

  20. Angular distributions of electrons photoemitted from core levels of oriented diatomic molecules: Multiple scattering theory in non-spherical potentials

    Energy Technology Data Exchange (ETDEWEB)

    Diez Muino, R.; Rolles, D.; Garcia de Abajo, F.J.; Fadley, C.S.; Van Hove, M.A.

    2001-09-06

    We use multiple scattering in non-spherical potentials (MSNSP) to calculate the angular distributions of electrons photoemitted from the 1s-shells of CO and N2 gas-phase molecules with fixed-in-space orientations. For low photoelectron kinetic energies (E<50 eV), as appropriate to certain shape-resonances, the electron scattering must be represented by non-spherical scattering potentials, which are naturally included in our formalism. Our calculations accurately reproduce the experimental angular patterns recently measured by several groups, including those at the shape-resonance energies. The MSNSP theory thus enhances the sensitivity to spatial electronic distribution and dynamics, paving the way toward their determination from experiment.

  1. Angular correlations and high energy evolution

    International Nuclear Information System (INIS)

    Kovner, Alex; Lublinsky, Michael

    2011-01-01

    We address the question of to what extent JIMWLK evolution is capable of taking into account angular correlations in a high energy hadronic wave function. Our conclusion is that angular (and indeed other) correlations in the wave function cannot be reliably calculated without taking into account Pomeron loops in the evolution. As an example we study numerically the energy evolution of angular correlations between dipole scattering amplitudes in the framework of the large N c approximation to JIMWLK evolution (the 'projectile dipole model'). Target correlations are introduced via averaging over an (isotropic) ensemble of anisotropic initial conditions. We find that correlations disappear very quickly with rapidity even inside the saturation radius. This is in accordance with our physical picture of JIMWLK evolution. The actual correlations inside the saturation radius in the target QCD wave function, on the other hand, should remain sizable at any rapidity.

  2. Time-resolved photoelectron spectroscopy using synchrotron radiation time structure

    International Nuclear Information System (INIS)

    Bergeard, N.; Silly, M.G.; Chauvet, C.; Guzzo, M.; Ricaud, J.P.; Izquierdo, M.; Sirotti, F.; Krizmancic, D.; Guzzo, M.; Stebel, L.; Pittana, P.; Sergo, R.; Cautero, G.; Dufour, G.; Rochet, F.

    2011-01-01

    Synchrotron radiation time structure is becoming a common tool for studying dynamic properties of materials. The main limitation is often the wide time domain the user would like to access with pump-probe experiments. In order to perform photoelectron spectroscopy experiments over time scales from milliseconds to picoseconds it is mandatory to measure the time at which each measured photoelectron was created. For this reason the usual CCD camera based two-dimensional detection of electron energy analyzers has been replaced by a new delay-line detector adapted to the time structure of the SOLEIL synchrotron radiation source. The new two-dimensional delay-line detector has a time resolution of 5 ns and was installed on a Scienta SES 2002 electron energy analyzer. The first application has been to characterize the time of flight of the photo emitted electrons as a function of their kinetic energy and the selected pass energy. By repeating the experiment as a function of the available pass energy and of the kinetic energy, a complete characterization of the analyzer behaviour in the time domain has been obtained. Even for kinetic energies as low as 10 eV at 2 eV pass energy, the time spread of the detected electrons is lower than 140 ns. These results and the time structure of the SOLEIL filling modes assure the possibility of performing pump-probe photoelectron spectroscopy experiments with the time resolution given by the SOLEIL pulse width, the best performance of the beamline and of the experimental station. (authors)

  3. Precise analysis of the metal package photomultiplier single photoelectron spectra

    International Nuclear Information System (INIS)

    Chirikov-Zorin, I.E.; Fedorko, I.; Sykora, I.; Tokar, S.; Menzione, A.

    2000-01-01

    A deconvolution method based on a sophisticated photomultiplier response function was used to analyse the compact metal package photomultiplier spectra taken in single photoelectron mode. The spectra taken by Hamamtsu R5600 and R5900 photomultipliers have been analysed. The detailed analysis shows that the method appropriately describes the process of charge multiplication in these photomultipliers in a wide range of working regimes and the deconvoluted parameters are established with about 1% accuracy. The method can be used for a detailed analysis of photomultiplier noise and for calibration purposes

  4. Accuracy of single photoelectron time spread measurement of fast photomultipliers

    International Nuclear Information System (INIS)

    Leskovar, B.

    1975-01-01

    The accuracy of time spread measurements of fast photomultipliers was investigated, using single photoelectrons. The effect of the finite light pulse width on the measurement accuracy was determined and discussed. Experimental data were obtained on a special measuring system for light pulse widths ranging from 200 psec to 10 nsec, using fast photomultipliers 8850 and C31024 with optimized operating conditions for minimum transit time spread. A modified exponential function expression and curve-fitting parameters are given, which fit closely the experimentally obtained data over a wide dynamic range of light pulse widths. (U.S.)

  5. Secondary-electron cascade in attosecond photoelectron spectroscopy from metals

    DEFF Research Database (Denmark)

    Baggesen, Jan Conrad; Madsen, Lars Bojer

    2009-01-01

    an analytical model based on an approximate solution to Boltzmann's transport equation to account for the amount and energy distribution of these secondary electrons. Our theory is in good agreement with the electron spectrum found in a recent attosecond streaking experiment. To suppress the background and gain......Attosecond spectroscopy is currently restricted to photon energies around 100 eV. We show that under these conditions, electron-electron scatterings, as the photoelectrons leave the metal, give rise to a tail of secondary electrons with lower energies and hence a significant background. We develop...

  6. Time-resolved photoelectron spectroscopy of nitrobenzene and its aldehydes

    Science.gov (United States)

    Schalk, Oliver; Townsend, Dave; Wolf, Thomas J. A.; Holland, David M. P.; Boguslavskiy, Andrey E.; Szöri, Milan; Stolow, Albert

    2018-01-01

    We report the first femtosecond time-resolved photoelectron spectroscopy study of 2-, 3- and 4-nitrobenzaldehyde (NBA) and nitrobenzene (NBE) in the gas phase upon excitation at 200 nm. In 3- and 4-NBA, the dynamics follow fast intersystem crossing within 1-2 picoseconds. In 2-NBA and NBE, the dynamics are faster (∼ 0.5 ps). 2-NBA undergoes hydrogen transfer similar to solution phase dynamics. NBE either releases NO2 in the excited state or converts internally back to the ground state. We discuss why these channels are suppressed in the other nitrobenzaldehydes.

  7. Automation of an X-ray photoelectron spectrometer

    International Nuclear Information System (INIS)

    Ashury, M.R.

    2003-02-01

    The Institute of Solid State Physics of the Vienna University of Technology is established with an X-ray Photoelectron Spectrometer Kratos XSAM 800. In its original state the instrument enables measurements of photoelectron spectra in a semiautomatical mode. After mounting of the specimen an eventual surface cleaning by argon ion sputtering is possible. Next steps are setting of x-ray tube high voltage and current, start energy and energy range of spectrum and time of measurement. Data are obtained by an x-t plotter and evaluations are performed from the registration charts. If necessary, measured spectra have to be digitized by means of a scanner. In the Introduction of this thesis the principle of X-ray photoelectron spectrometry is treated including a number of practical examples. It shows that an automation allows an extension of the performance of the instrument. Details are remote controlled experiments, wider energy ranges with improved energy resolution. Furthermore, the digitized data treatment enables background subtration, determination of line positions and integrated signal strengths, and is the detection of lowlevel of lines (the peak with lowamplitude) possible. A further advantage is the computer assisted documentation and comparison of results from different specimens. After this description of the essential requirements different possible solutions of an automation are discussed. Thus, it is decided to develop a completely new hardware for a perfect control of the spectrometer. A further decision is to be made on the most efficient kind of micro processor. From the considerations follows a completely new control board with a transputer as multi tasking processor. The complete control unit consists of a digital system, an analog system and a power unit. The digital system controls settings and spectra accumulation and includes the transputer board, the pc-link card, the i/o-card and the step scanning control board. The analog system controls the

  8. Photoelectron Spectroscopy of 4-Bromochlorobenzene Dimer and Trimer Anions

    International Nuclear Information System (INIS)

    Kim, Namdoo

    2013-01-01

    I investigated the electron attachment to 4-BCB dimer and trimer anions using anion photoelectron spectroscopy and theoretical calculations. I found that an excess electron can be delocalized to these clusters through extended π-network. However, the nature of the ion core is different for the dimer and trimer. For the heterodimer anions, the geometry is determined by the differences in electronegativity of the molecules. Dimer anions with a large electronegativity difference have T-shaped geometries and those with a small electronegativity difference have PD geometries

  9. Polarization of photoelectrons produced from atoms by synchrotron radiation

    International Nuclear Information System (INIS)

    Hughes, V.W.; Lu, D.C.; Huang, K.N.

    1981-01-01

    The polarization of photoelectrons from stoms has proved to be an important tool for studying correlation effects in atoms, as well as relativistic effects such as the spin-orbit interaction. Extensive experimental and theoretical studies have been made of the Fano effect, which is the production of polarized electrons by photoionization of unpolarized atoms by circularly polarized light. The experiments have dealt mostly with alkali atoms and with photon energies slightly above the ionization thresholds. Measurements that could be made to utilize polarized radiation are discussed

  10. Time-resolved photoelectron nano-spectroscopy of individual silver particles: Perspectives and limitations

    DEFF Research Database (Denmark)

    Rohmer, Martin; Bauer, Michael; Leissner, Till

    2010-01-01

    Simultaneous time- and energy-resolved two-photon photoemission with nanometer resolution is demonstrated for the first time. We monitor the energy dependence of the decay dynamics of electron excitations in individual silver particles, which were deposited from a gas aggregation cluster source...

  11. Determination of the photoelectron reference plane in nanostructured surfaces

    International Nuclear Information System (INIS)

    Lobo-Checa, Jorge; Mugarza, Aitor; Ortega, Jose Enrique; Michel, Enrique G

    2011-01-01

    In angle-resolved photoemission (ARPES) from crystalline solids, wave-vector conservation applies to the two-dimensional (2D) surface, which may thus be defined as the reference plane in ARPES. We investigate whether such reference varies for photoemitted electrons in nanometer-sized systems that expose different crystal planes. To this aim, we exploit the structural tunability of the Ag/Cu(223) system which is capable of offering surfaces with periodic arrays of nanofacets of varying size and orientation. A thorough, photon-energy-dependent analysis of the surface states confined to such nanostructures is performed comparing different reference planes for photoemitted electrons. Assuming the premise that k || must be a good quantum number for 2D states, we conclude that the (final state) photoelectron reference direction is not the average optical direction but the local facet that confines the (initial state) surface electrons. Moreover, in the general case of nanostructured systems with uneven surfaces, we show how the photoelectron reference plane can be empirically determined through such a photon-energy-dependent ARPES analysis. (paper)

  12. Interpretation of intensities in electron-momentum and photoelectron spectroscopies

    International Nuclear Information System (INIS)

    McCarthy, I.E.

    1984-06-01

    Relative intensities for the photoelectron reaction on atoms and molecules are not related to structure calculations in the same way as those for the noncoplanar symmetric (e,2e) reaction. The photoelectron dipole matrix element is dependent on recoil momentum only through its unique relationship to the photon energy and is much harder to calculate for chemically-interesting momenta. Relative intensities for binary (e,2e) reactions are independent of total energy at high enough energies and strongly dependent on symmetry and recoil momentum, for which an intensity profile can be measured for values starting at zero. In comparing with structure calculations, binary (e,2e) intensities for low recoil momentum may be compared directly with pole strengths in calculations of the one-electron Green's function or corresponding configuration-interaction calculations. In the case of states within a single symmetry manifold the relative intensities will be independent of recoil momentum up to some maximum, usually at least a few atomic units

  13. Photoelectron spectroscopy and Auger electron spectroscopy of solids and surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Kowalczyk, S.P.

    1976-01-01

    The use of photoelectron spectroscopy, primarily x-ray photoelectron spectroscopy, to obtain information on the electronic structure of a wide variety of solids (especially the bulk electronic structure of solids) is covered. Both valence band and core-level spectra, as well as a few cases of photon excited Auger electron spectroscopy, are employed in the investigations to derive information on N(E). The effect of several modulations inherent in the measured I(E)'s, such as final state band structure, cross section, and relaxation, is discussed. Examples of many-electron interactions in PES are given. Some experimental aspects of PES and AES studies are given with emphasis on sample preparation techniques. Multiple splitting of core levels is examined using the Mn levels in MnF/sub 2/ as a detailed case study. Core level splittings in transition metals, rare earth metals, transition metal halides and several alloys are also reported. The application of PES to the study of the chemical bond in some crystalline semiconductors and insulators, A/sup N/B/sup 8-N/ and A/sup N/B/sup 10-N/ compounds is treated, and a spectroscopic scale of ionicity for these compounds is developed from the measured ''s-band'' splitting in the valence band density of states. (GHT)

  14. Photoelectron diffraction of magnetic ultrathin films: Fe/Cu(001)

    Energy Technology Data Exchange (ETDEWEB)

    Tobin, J.G. (Lawrence Livermore National Lab., CA (USA)); Wagner, M.K. (Wisconsin Univ., Madison, WI (USA). Dept. of Chemistry); Guo, X.Q.; Tong, S.Y. (Wisconsin Univ., Milwaukee, WI (USA). Dept. of Physics)

    1991-01-03

    The preliminary results of an ongoing investigation of Fe/Cu(001) are presented here. Energy dependent photoelectron diffraction, including the spin-dependent variant using the multiplet split Fe3s state, is being used to investigate the nanoscale structures formed by near-monolayer deposits of Fe onto Cu(001). Core-level photoemission from the Fe3p and Fe3s states has been generated using synchrotron radiation as the tunable excitation source. Tentatively, a comparison of the experimental Fe3p cross section measurements with multiple scattering calculations indicates that the Fe is in a fourfold hollow site with a spacing of 3.6{Angstrom} between it and the atom directly beneath it, in the third layer. This is consistent with an FCC structure. The possibility of utilizing spin-dependent photoelectron diffraction to investigate magnetic ultrathin films will be demonstrated, using our preliminary spectra of the multiplet-split Fe3s os near-monolayer Fe/Cu(001). 18 refs., 10 figs.

  15. Using photoelectron diffraction to determine complex molecular adsorption structures

    International Nuclear Information System (INIS)

    Woodruff, D P

    2010-01-01

    Backscattering photoelectron diffraction, particularly in the energy-scan mode, is now an established technique for determining in a quantitative fashion the local structure of adsorbates on surfaces, and has been used successfully for ∼100 adsorbate phases. The elemental and chemical-state specificity afforded by the characteristic core level photoelectron binding energies means that it has particular advantages for molecular adsorbates, as the local geometry of inequivalent atoms in the molecule can be determined in a largely independent fashion. On the other hand, polyatomic molecules present a general problem for all methods of surface structure determination in that a mismatch of intramolecular distances with interatomic distances on the substrate surface means that the atoms in the adsorbed molecule are generally in low-symmetry sites. The quantities measured experimentally then represent an incoherent sum of the properties of each structural domain that is inequivalent with respect to the substrate point group symmetry. This typically leads to greater ambiguity or precision in the structural solutions. The basic principles of the method are described and illustrated with a simple example involving molecule/substrate bonding through only one constituent atom (TiO 2 -(110)/H 2 O). This example demonstrates the importance of obtaining quantitative local structural information. Further examples illustrate both the successes and the problems of this approach when applied to somewhat more complex molecular adsorbates.

  16. Photoelectron spectroscopy and Auger electron spectroscopy of solids and surfaces

    International Nuclear Information System (INIS)

    Kowalczyk, S.P.

    1976-01-01

    The use of photoelectron spectroscopy, primarily x-ray photoelectron spectroscopy, to obtain information on the electronic structure of a wide variety of solids (especially the bulk electronic structure of solids) is covered. Both valence band and core-level spectra, as well as a few cases of photon excited Auger electron spectroscopy, are employed in the investigations to derive information on N(E). The effect of several modulations inherent in the measured I(E)'s, such as final state band structure, cross section, and relaxation, is discussed. Examples of many-electron interactions in PES are given. Some experimental aspects of PES and AES studies are given with emphasis on sample preparation techniques. Multiple splitting of core levels is examined using the Mn levels in MnF 2 as a detailed case study. Core level splittings in transition metals, rare earth metals, transition metal halides and several alloys are also reported. The application of PES to the study of the chemical bond in some crystalline semiconductors and insulators, A/sup N/B/sup 8-N/ and A/sup N/B/sup 10-N/ compounds is treated, and a spectroscopic scale of ionicity for these compounds is developed from the measured ''s-band'' splitting in the valence band density of states

  17. Angular and linear momentum of excited ferromagnets

    NARCIS (Netherlands)

    Yan, P.; Kamra, A.; Cao, Y.; Bauer, G.E.W.

    2013-01-01

    The angular momentum vector of a Heisenberg ferromagnet with isotropic exchange interaction is conserved, while under uniaxial crystalline anisotropy the projection of the total spin along the easy axis is a constant of motion. Using Noether's theorem, we prove that these conservation laws persist

  18. Angular distribution in ternary cold fission

    International Nuclear Information System (INIS)

    Delion, D.S.; J.W. Goethe Univ., Frankfurt; Sandulescu, A.; J.W. Goethe Univ., Frankfurt; Greiner, W.

    2003-01-01

    We describe the spontaneous ternary cold fission of 252 Cf, accompanied by 4 He, 10 Be and 14 C. The light cluster decays from the first resonant eigenstate in the Coulomb potential plus a harmonic oscillator potential. We have shown that the angular distribution of the emitted light particle is strongly connected with its deformation and the equatorial distance. (author)

  19. Probabilistic calculation for angular dependence collision

    International Nuclear Information System (INIS)

    Villarino, E.A.

    1990-01-01

    This collision probabilistic method is broadly used in cylindrical geometry (in one- or two-dimensions). It constitutes a powerful tool for the heterogeneous Response Method where, the coupling current is of the cosine type, that is, without angular dependence at azimuthal angle θ and proportional to μ (cosine of the θ polar angle). (Author) [es

  20. Heteromodal conceptual processing in the angular gyrus.

    Science.gov (United States)

    Bonner, Michael F; Peelle, Jonathan E; Cook, Philip A; Grossman, Murray

    2013-05-01

    Concepts bind together the features commonly associated with objects and events to form networks in long-term semantic memory. These conceptual networks are the basis of human knowledge and underlie perception, imagination, and the ability to communicate about experiences and the contents of the environment. Although it is often assumed that this distributed semantic information is integrated in higher-level heteromodal association cortices, open questions remain about the role and anatomic basis of heteromodal representations in semantic memory. Here we used combined neuroimaging evidence from functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI) to characterize the cortical networks underlying concept representation. Using a lexical decision task, we examined the processing of concepts in four semantic categories that varied on their sensory-motor feature associations (sight, sound, manipulation, and abstract). We found that the angular gyrus was activated across all categories regardless of their modality-specific feature associations, consistent with a heteromodal account for the angular gyrus. Exploratory analyses suggested that categories with weighted sensory-motor features additionally recruited modality-specific association cortices. Furthermore, DTI tractography identified white matter tracts connecting these regions of modality-specific functional activation with the angular gyrus. These findings are consistent with a distributed semantic network that includes a heteromodal, integrative component in the angular gyrus in combination with sensory-motor feature representations in modality-specific association cortices. Copyright © 2013 Elsevier Inc. All rights reserved.

  1. INVESTIGATION OF ANGULAR BALL BEARING WEAR

    Directory of Open Access Journals (Sweden)

    A. L. Savchenko

    2006-01-01

    Full Text Available Wearing process of balls in an angular ball bearing has been investigated in the paper. Force affecting a separator from the side of balls is determined theoretically. Wear rate may be calculated with a formula for abrasive wear while substituting numerical parameter values of the investigated ball bearing for formula symbols.

  2. Canonical three-body angular basis

    International Nuclear Information System (INIS)

    Matveenko, A.V.

    2001-01-01

    Three-body problems are basic for the quantum mechanics of molecular, atomic, or nuclear systems. We demonstrate that their variational solution for rotational states can be greatly simplified. A special choice of coordinates (hyperspherical) and of the kinematics (body-fixed coordinate frame) allows one to choose basis functions in a form that makes the angular coupling trivial. (author)

  3. Temperature and angular momentum dependence of the ...

    Indian Academy of Sciences (India)

    Temperature and angular momentum dependence of the quadrupole deformation is studied in the middle of the sd-shell for 28Si and 27Si isotopes using the spherical shell model approach. The shell model calculations have been performed using the standard universal sd-shell (USD) interaction and the canonical ...

  4. Angular momentum gated neutron evaporation studies

    International Nuclear Information System (INIS)

    Banerjee, K.; Kundu, S.; Rana, T.K.; Bhattacharya, C.; Mukherjee, G.; Gohil, M.; Meena, J.K.; Pandey, R.; Pai, H.; Dey, A.; Biswas, M.; Mukhopadhyay, S.; Pandit, D.; Pal, S.; Banerjee, S.R.; Bhattacharya, S.; Bandhopadhyay, T.

    2010-01-01

    The inverse level density parameter k (k = A/a, where A is the mass number of the compound nucleus)is investigated as a function of angular momentum by measuring γ-ray fold gated neutron evaporation spectrum in 4 He + 115 In fusion reaction using 35 MeV 4 He ion beam from VECC K130 cyclotron

  5. Angular-momentum-bearing modes in fission

    International Nuclear Information System (INIS)

    Moretto, L.G.; Peaslee, G.F.; Wozniak, G.J.

    1989-03-01

    The angular-momentum-bearing degrees of freedom involved in the fission process are identified and their influence on experimental observables is discussed. The excitation of these modes is treated in the ''thermal'' limit, and the resulting distributions of observables are calculated. Experiments demonstrating the role of these modes are presented and discussed. 61 refs., 12 figs

  6. Angular Intermittency and Analytical QCD Predictions

    CERN Document Server

    Chekanov, S.V.

    1997-01-01

    We present a comparison of local multiplicity fluctuations in angular phase-space intervals with first-order QCD predictions. The data are based on 810k hadronic events at 91.2 GeV collected with the L3 detector at LEP during 1994.

  7. Angular momentum transfer in incomplete fusion

    Indian Academy of Sciences (India)

    Keywords. Heavy-ion reactions; incomplete fusion; isomeric cross-section ratio; 12C, 16O beams; 93Nb; 89Y targets; angular momentum. ... R Tripathi1 A Goswami1. Radiochemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085, India; School of Studies in Physics, Vikram University, Ujjain 456 010, India ...

  8. Temperature and angular momentum dependence of the ...

    Indian Academy of Sciences (India)

    Abstract. Temperature and angular momentum dependence of the quadrupole deformation is studied in the middle of the sd-shell for 28Si and 27Si isotopes using the spherical shell model ... Department of Physics, University of Kashmir, Srinagar 190 006, India; Inter-University Accelerator Centre, New Delhi 110 067, India ...

  9. On the angular momentum in star formation

    International Nuclear Information System (INIS)

    Horedt, G.P.

    1978-01-01

    The author discusses the rotation of interstellar clouds which are in a stage immediately before star formation. Cloud collisions seem to be the principal cause of the observed rotation of interstellar clouds. The rotational motion of the clouds is strongly influenced by turbulence. Theories dealing with the resolution of the angular momentum problem in star formation are classified into five major groups. The old idea that the angular momentum of an interstellar cloud passes during star formation into the angular momentum of double star systems and/or circumstellar clouds, is developed. It is suggested that a rotating gas cloud contracts into a ring-like structure which fragments into self-gravitating subcondensations. By collisions and gas accretion these subcondensations accrete into binary systems surrounded by circumstellar clouds. Using some rough approximations the authors find analytical expressions for the semi-major axis of the binary system and for the density of the circumstellar clouds as a function of the initial density and of the initial angular velocity of an interstellar cloud. The obtained values are well within the observational limits. (Auth.)

  10. A Novel Permanent Magnetic Angular Acceleration Sensor

    Directory of Open Access Journals (Sweden)

    Hao Zhao

    2015-07-01

    Full Text Available Angular acceleration is an important parameter for status monitoring and fault diagnosis of rotary machinery. Therefore, we developed a novel permanent magnetic angular acceleration sensor, which is without rotation angle limitations and could directly measure the instantaneous angular acceleration of the rotating system. The sensor rotor only needs to be coaxially connected with the rotating system, which enables convenient sensor installation. For the cup structure of the sensor rotor, it has a relatively small rotational inertia. Due to the unique mechanical structure of the sensor, the output signal of the sensor can be directed without a slip ring, which avoids signal weakening effect. In this paper, the operating principle of the sensor is described, and simulated using finite element method. The sensitivity of the sensor is calibrated by torsional pendulum and angle sensor, yielding an experimental result of about 0.88 mV/(rad·s−2. Finally, the angular acceleration of the actual rotating system has been tested, using both a single-phase asynchronous motor and a step motor. Experimental result confirms the operating principle of the sensor and indicates that the sensor has good practicability.

  11. Variation in angular velocity and angular acceleration of a particle in rectilinear motion

    International Nuclear Information System (INIS)

    Mashood, K K; Singh, V A

    2012-01-01

    We discuss the angular velocity and angular acceleration associated with a particle in rectilinear motion with constant acceleration. The discussion was motivated by an observation that students and even teachers have difficulty in ascribing rotational motion concepts to a particle when the trajectory is a straight line. We present some details of our observations. A formal derivation of ω and α is presented which reveals ‘surprising’ and non-intuitive aspects, namely non-monotonic behaviour with an associated extremum. The special case of constant velocity is studied and we find that angular acceleration associated with it also has an extremum. We discuss a plausible source of difficulty. (paper)

  12. Study of the photoelectron and electron momentum spectra of cyclopentene using benchmark Dyson orbital theories.

    Science.gov (United States)

    Huang, Yan R; Ning, Chuan G; Deng, Jing K; Deleuze, Michael S

    2008-05-07

    A complete study of the valence electronic structure and related electronic excitation properties of cyclopentene in its C(s) ground state geometry is presented. Ionization spectra obtained from this compound by means of photoelectron spectroscopy (He I and He II) and electron momentum spectroscopy have been analyzed in details up to electron binding energies of 30 eV using one-particle Green's function (1p-GF) theory along with the outer-valence (OVGF) and the third-order algebraic diagrammatic construction [ADC(3)] schemes. The employed geometries derive from DFT/B3LYP calculations in conjunction with the aug-cc-pVTZ basis set, and closely approach the structures inferred from experiments employing microwave spectroscopy or electron diffraction in the gas phase. The 1p-GF/ADC(3) calculations indicate that the orbital picture of ionization breaks down at electron binding energies larger than approximately 17 eV in the inner-valence region, and that the outer-valence 7a' orbital is also subject to a significant dispersion of the ionization intensity over shake-up states. This study confirms further the rule that OVGF pole strengths smaller than 0.85 foretell a breakdown of the orbital picture of ionization at the ADC(3) level. Spherically averaged (e, 2e) electron momentum distributions at an electron impact energy of 1200 eV that were experimentally inferred from an angular analysis of EMS intensities have been interpreted by comparison with accurate simulations employing ADC(3) Dyson orbitals. Very significant discrepancies were observed with momentum distributions obtained from several outer-valence ionization bands using standard Kohn-Sham orbitals.

  13. Development of Angular Motion, Angular Momentum, and Torque Knowledge Bases for an Intelligent Physics Tutoring System

    National Research Council Canada - National Science Library

    Eason, Michael

    1998-01-01

    .... The knowledge base developed in this project provides the physics backbone for the rest of the tutoring system by generating the necessary equations and solution graphs to solve selected angular motion...

  14. Angular dependence of quartz fiber calorimeter response

    International Nuclear Information System (INIS)

    Anzivino, G.; Chamorovskii, Yu.; Contin, A.; Danilov, M.; Dellacasa, G.; DeSalvo, R.; Gavrilov, V.; Golutvin, A.; Gorodetzky, P.; Johnson, K.F.; Juillot, P.; Lacommare, G.; Lazic, D.; Litvintsev, D.; Lundin, M.; Marino, M.; Musso, A.; Ratnikov, F.; Rusinov, V.; Stolin, V.; Vinogradov, M.

    1995-01-01

    A small quartz fiber calorimeter prototype with copper absorber has been assembled and tested at ITEP as a first test of a ''0 degree'' component of the RD-40 R and D program. Calibration and monitoring of each tower response was performed using the positions of single photoelectron peaks as well as the response to minimum ionizing particles incident at an angle of 45 . The response of the prototype to 4 GeV electrons as a function of beam angle with respect to the quartz fibers was studied in the range from 0 to 90 . The test results are compared to the GEANT based Monte Carlo (MC) simulations. (orig.)

  15. Attosecond photoelectron spectroscopy of electron transport in solids

    Energy Technology Data Exchange (ETDEWEB)

    Magerl, Elisabeth

    2011-03-31

    Time-resolved photoelectron spectroscopy of condensed matter systems in the attosecond regime promises new insights into excitation mechanisms and transient dynamics of electrons in solids. This timescale became accessible directly only recently with the development of the attosecond streak camera and of laser systems providing few-cycle, phase-controlled laser pulses in the near-infrared, which are used to generate isolated, sub-femtosecond extreme-ultraviolet pulses with a well-defined timing with respect to the near-infrared pulse. Employing these pulses, the attosecond streak camera offers time resolutions as short as a few 10 attoseconds. In the framework of this thesis, a new, versatile experimental apparatus combining attosecond pulse generation in gases with state of the art surface science techniques is designed, constructed, and commissioned. Employing this novel infrastructure and the technique of the attosecond transient recorder, we investigate transport phenomena occurring after photoexcitation of electrons in tungsten and rhenium single crystals and show that attosecond streaking is a unique method for resolving extremely fast electronic phenomena in solids. It is demonstrated that electrons originating from different energy levels, i.e. from the conduction band and the 4f core level, are emitted from the crystal surface at different times. The origin of this time delay, which is below 150 attoseconds for all studied systems, is investigated by a systematic variation of several experimental parameters, in particular the photon energy of the employed attosecond pulses. These experimental studies are complemented by theoretical studies of the group velocity of highly-excited electrons based on ab initio calculations. While the streaking technique applied on single crystals can provide only information about the relative time delay between two types of photoelectrons, the absolute transport time remains inaccessible. We introduce a scheme of a reference

  16. Ultrafast photoelectron spectroscopy of small molecule organic films

    Science.gov (United States)

    Read, Kendall Laine

    As research in the field of ultrafast optics has produced shorter and shorter pulses, at an ever-widening range of frequencies, ultrafast spectroscopy has grown correspondingly. In particular, ultrafast photoelectron spectroscopy allows direct observation of electrons in transient or excited states, regardless of the eventual relaxation mechanisms. High-harmonic conversion of 800nm, femtosecond, Ti:sapphire laser pulses allows excite/probe spectroscopy down into atomic core level states. To this end, an ultrafast, X-UV photoelectron spectroscopic system is described, including design considerations for the high-harmonic generation line, the time of flight detector, and the subsequent data collection electronics. Using a similar experimental setup, I have performed several ultrafast, photoelectron excited state decay studies at the IBM, T. J. Watson Research Center. All of the observed materials were electroluminescent thin film organics, which have applications as the emitter layer in organic light emitting devices. The specific materials discussed are: Alq, BAlq, DPVBi, and Alq doped with DCM or DMQA. Alq:DCM is also known to lase at low photoexcitation thresholds. A detailed understanding of the involved relaxation mechanisms is beneficial to both applications. Using 3.14 eV excite, and 26.7 eV probe, 90 fs laser pulses, we have observed the lowest unoccupied molecular orbital (LUMO) decay rate over the first 200 picoseconds. During this time, diffusion is insignificant, and all dynamics occur in the absence of electron transport. With excitation intensities in the range of 100μJ/cm2, we have modeled the Alq, BAlq, and DPVBi decays via bimolecular singlet-singlet annihilation. At similar excitations, we have modeled the Alq:DCM decay via Förster transfer, stimulated emission, and excimeric formation. Furthermore, the Alq:DCM occupied to unoccupied molecular orbital energy gap was seen to shrink as a function of excite-to-probe delay, in accordance with the

  17. Attosecond photoelectron spectroscopy of electron transport in solids

    International Nuclear Information System (INIS)

    Magerl, Elisabeth

    2011-01-01

    Time-resolved photoelectron spectroscopy of condensed matter systems in the attosecond regime promises new insights into excitation mechanisms and transient dynamics of electrons in solids. This timescale became accessible directly only recently with the development of the attosecond streak camera and of laser systems providing few-cycle, phase-controlled laser pulses in the near-infrared, which are used to generate isolated, sub-femtosecond extreme-ultraviolet pulses with a well-defined timing with respect to the near-infrared pulse. Employing these pulses, the attosecond streak camera offers time resolutions as short as a few 10 attoseconds. In the framework of this thesis, a new, versatile experimental apparatus combining attosecond pulse generation in gases with state of the art surface science techniques is designed, constructed, and commissioned. Employing this novel infrastructure and the technique of the attosecond transient recorder, we investigate transport phenomena occurring after photoexcitation of electrons in tungsten and rhenium single crystals and show that attosecond streaking is a unique method for resolving extremely fast electronic phenomena in solids. It is demonstrated that electrons originating from different energy levels, i.e. from the conduction band and the 4f core level, are emitted from the crystal surface at different times. The origin of this time delay, which is below 150 attoseconds for all studied systems, is investigated by a systematic variation of several experimental parameters, in particular the photon energy of the employed attosecond pulses. These experimental studies are complemented by theoretical studies of the group velocity of highly-excited electrons based on ab initio calculations. While the streaking technique applied on single crystals can provide only information about the relative time delay between two types of photoelectrons, the absolute transport time remains inaccessible. We introduce a scheme of a reference

  18. Photoelectron studies of autoionizing Rydberg states in HCl

    International Nuclear Information System (INIS)

    White, M.G.; Grover, J.R.

    1985-01-01

    The results of a systematic investigation of electronically autoionizing Rydberg states in HCl are discussed. Vibrationally resolved photoelectron spectroscopy was used to map out the non-radiative decay of vibronic levels of 3psigma → n(/sub d//sup s/)sigma Rydberg states converging to the A 2 Σ + (3psigma) -1 excited ionic state. The observed vibrational distributions of the resulting X 2 PI(1π) -1 ionic state are compared with the results of model calculations of Terwilliger and Smith based on spectral analysis of the absorption spectrum. Overall, the X 2 PI vibrational branching ratios are found to be in only rough qualitative agreement with the calculations and these results are discussed in relation to the approximations involved. 18 refs., 4 figs., 1 tab

  19. Measurement of the Photoelectron Detection Efficiency of the HPD Anode

    CERN Document Server

    Carson, L; Soler, P

    2009-01-01

    This paper reports on measurements carried out on the Hybrid Photon Detectors (HPDs) of the LHCb RICH detectors. The purpose of these tests is to determine the photoelectron detection efficiency $\\eta$ of the HPD anode. Knowledge of $\\eta$ is required for an accurate simulation of the RICH detectors. It is found that this efficiency is $(93.3\\pm0.7)\\%$ for a 50 ns digital readout window, and $(87.9\\pm1.4)\\%$ for a 25 ns digital readout window. The 25 ns result exceeds the LHCb-RICH requirement of 85\\%, and is in agreement both with direct $\\eta$ measurements using preseries HPDs, and with indirect measurements from testbeams using preseries and production HPDs.

  20. X-ray photoelectron spectra of γ-irradiated perfluorobenzene

    International Nuclear Information System (INIS)

    Sunder, S.; Sagert, N.H.; Wood, D.D.; Miller, N.H.

    1990-01-01

    The effect of γ-radiolysis on perfluorobenzene (PFB) was investigated using low-temperature X-ray photoelectron spectroscopy (XPS). PFB was irradiated in fluorine-passivated nickel cells using Co 60 γ-rays in an Atomic Energy of Canada Limited Gammacell at a dose rate of about 2.6 Gy·s -1 and for a total dose of about 50 kGy. The γ-radiolysis of PFB not only results in cross-linkage but also in the formation of saturated carbon centers in the PFB, as indicated by the presence of CF 2 and CF 3 groups. The relative abundance of CF, CF 2 and CF 3 groups, in the irradiated PFB, was estimated to be about 86, 9 and 5%, respectively

  1. Negative ion photoelectron spectroscopy of SeO-

    International Nuclear Information System (INIS)

    Coe, J.V.; Snodgrass, J.T.; Freidhoff, C.B.; McHugh, K.M.; Bowen, K.H.

    1985-01-01

    Negative ion photoelectron spectroscopy (NIPES) involves a kinetic energy analysis of electrons which are photodetached when a mass selected beam of negative ions is crossed with a fixed frequency laser beam. The photodetachment spectra of SeO - displays transitions from the X 2 PI state of SeO - to both the X 3 Σ - and a 1 Δ states of SeO. The singlet-triplet splitting of SeO is readily observable since selection rules regarding spin do not apply in the bound to free state process of photodetachment. The electron affinity of SeO and the negative ion potential parameters of SeO - have been determined

  2. High temperature and high resolution uv photoelectron spectroscopy using supersonic molecular beams

    International Nuclear Information System (INIS)

    Wang, Lai-Sheng; Reutt-Robey, J.E.; Niu, B.; Lee, Y.T.; Shirley, D.A.

    1989-07-01

    A high temperature molecular beam source with electron bombardment heating has been built for high resolution photoelectron spectroscopic studies of high temperature species and clusters. This source has the advantages of: producing an intense, continuous, seeded molecular beam, eliminating the interference of the heating mechanism from the photoelectron measurement. Coupling the source with our hemispherical electron energy analyzer, we can obtain very high resolution HeIα (584 angstrom) photoelectron spectra of high temperature species. Vibrationally-resolved photoelectron spectra of PbSe, As 2 , As 4 , and ZnCl 2 are shown to demonstrate the performance of the new source. 25 refs., 8 figs., 1 tab

  3. Multichannel system for angular distribution measurements

    International Nuclear Information System (INIS)

    Burjan, V.; Kroha, V.; Putz, K.

    A description is given of the individual blocks of the spectrometric apparatus used for measuring the angular distribution of particle spectra and excitation functions of (d,p) reactions at an electrostatic accelerator and the U-120 M cyclotron, both operating at the Nuclear Physics Institute of the Czechoslovak Academy of Sciences at Rez. Main attention was devoted to attaining maximum energy resolution at a high measurement efficiency, this by installing 8 independent spectrometric chains allowing simultaneous measurement of angular distribution in 8 points of the beam. The semiconductor detectors were cooled to -40 degC to -60 degC, which significantly reduced the level of inherent detector noise. An energy resolution of 13 keV was attained using Tesla detectors at a particle energy of 11 MeV. A brief review of data processing and software is given. (B.S.)

  4. Angular distribution of laser ablation plasma

    International Nuclear Information System (INIS)

    Kondo, K.; Kanesue, T.; Dabrowski, R.; Okamura, M.

    2010-01-01

    An expansion of a laser induced plasma is fundamental and important phenomena in a laser ion source. To understand the expanding direction, an array of Langmuir probes were employed. The chosen ion for the experiment was Ag 1+ which was created by a second harmonics of a Nd-YAG laser. The obtained angular distribution was about ±10 degree. This result also indicates a proper positioning of a solenoid magnet which enhances ion beam current.

  5. Continuum angular distributions in the transition regions

    International Nuclear Information System (INIS)

    Kalbach, C.

    1993-01-01

    One of the open questions from the 1988 published systematics of continuum angular distributions in light particle reactions is addressed. Evidence for a smooth transition in the systematics at incident energies of ∼125 MeV is summarized, and appropriate revisions to the global parameterization are proposed. Applying similar changes to the second-order term helps to remove problems noted in the literature with low-energy (N,α) reactions

  6. Coincident-inclusive electrofission angular correlations

    International Nuclear Information System (INIS)

    Arruda Neto, J.D.T.

    1983-08-01

    A method for the joint analysis of coincident and inclusive electrofission data, in order to minimize effects of the model dependence of data interpretation, is developed. Explicit calculations of the (e,e'f) angular correlations are presented. The potentialities of the method to the study of sub- and near-barrier properties of the fission process, and to the study of the giant resonances fission mode, are discussed. (Author) [pt

  7. Spatial angular compounding of photoacoustic images

    OpenAIRE

    Kang, Hyun Jae; Bell, Muyinatu A Lediju; Guo, Xiaoyu; Boctor, Emad M.

    2016-01-01

    Photoacoustic (PA) images utilize pulsed lasers and ultrasound transducers to visualize targets with higher optical absorption than the surrounding medium. However, they are susceptible to acoustic clutter and background noise artifacts that obfuscate biomedical structures of interest. We investigated three spatial-angular compounding methods to improve PA image quality for biomedical applications, implemented by combining multiple images acquired as an ultrasound probe was rotated about the ...

  8. Orbital angular momentum light in microscopy.

    Science.gov (United States)

    Ritsch-Marte, Monika

    2017-02-28

    Light with a helical phase has had an impact on optical imaging, pushing the limits of resolution or sensitivity. Here, special emphasis will be given to classical light microscopy of phase samples and to Fourier filtering techniques with a helical phase profile, such as the spiral phase contrast technique in its many variants and areas of application.This article is part of the themed issue 'Optical orbital angular momentum'. © 2017 The Author(s).

  9. Continuous particle spectra and their angular distributions

    International Nuclear Information System (INIS)

    Sastry, Ch.V.; Jain, R.K.; Rama Rao, J.; Ernst, J.; Machner, H.

    1996-01-01

    The angular distribution of continuous particle spectra in pre-equilibrium reactions is still an unsolved problem, particularly so at forward angles. In the present work, the angular distributions of alpha particles emitted in (α, α',x) reactions in the target elements gold and rhodium have been studied in detail. Alpha particle beams of energy 60 MeV from the Variable Energy Cyclotron of Calcutta were used in these experiments. The theoretical calculations were done using an extended exciton model of Kalbach incorporated into the Computer Code PRECO-D2. The formalism used in the exciton model was modified to include division of pre equilibrium cross section into multi-step direct (MSD) and multi-step compound (MSC) components. These MSD and MSC cross sections were used to calculate the angular distributions in terms of Legendre polynomials whose coefficients are given by simple phenomenological relations. Even with a reasonable set of parameters, the agreement between theory and experiment was far from satisfactory at forward angles. Similar conclusion was also drawn in the case of continuous particle spectra of deuterons in (d, d'x) reactions at 25 MeV in various targets. (author). 10 refs., 2 figs

  10. The Cosmology Large Angular Scale Surveyor

    Science.gov (United States)

    Harrington, Kathleen; Marriage, Tobias; Ali, Aamir; Appel, John; Bennett, Charles; Boone, Fletcher; Brewer, Michael; Chan, Manwei; Chuss, David T.; Colazo, Felipe; hide

    2016-01-01

    The Cosmology Large Angular Scale Surveyor (CLASS) is a four telescope array designed to characterize relic primordial gravitational waves from inflation and the optical depth to reionization through a measurement of the polarized cosmic microwave background (CMB) on the largest angular scales. The frequencies of the four CLASS telescopes, one at 38 GHz, two at 93 GHz, and one dichroic system at 145217 GHz, are chosen to avoid spectral regions of high atmospheric emission and span the minimum of the polarized Galactic foregrounds: synchrotron emission at lower frequencies and dust emission at higher frequencies. Low-noise transition edge sensor detectors and a rapid front-end polarization modulator provide a unique combination of high sensitivity, stability, and control of systematics. The CLASS site, at 5200 m in the Chilean Atacama desert, allows for daily mapping of up to 70% of the sky and enables the characterization of CMB polarization at the largest angular scales. Using this combination of a broad frequency range, large sky coverage, control over systematics, and high sensitivity, CLASS will observe the reionization and recombination peaks of the CMB E- and B-mode power spectra. CLASS will make a cosmic variance limited measurement of the optical depth to reionization and will measure or place upper limits on the tensor-to-scalar ratio, r, down to a level of 0.01 (95% C.L.).

  11. The Cosmology Large Angular Scale Surveyor (CLASS)

    Science.gov (United States)

    Harrington, Kathleen; Marriange, Tobias; Aamir, Ali; Appel, John W.; Bennett, Charles L.; Boone, Fletcher; Brewer, Michael; Chan, Manwei; Chuss, David T.; Colazo, Felipe; hide

    2016-01-01

    The Cosmology Large Angular Scale Surveyor (CLASS) is a four telescope array designed to characterize relic primordial gravitational waves from in ation and the optical depth to reionization through a measurement of the polarized cosmic microwave background (CMB) on the largest angular scales. The frequencies of the four CLASS telescopes, one at 38 GHz, two at 93 GHz, and one dichroic system at 145/217 GHz, are chosen to avoid spectral regions of high atmospheric emission and span the minimum of the polarized Galactic foregrounds: synchrotron emission at lower frequencies and dust emission at higher frequencies. Low-noise transition edge sensor detectors and a rapid front-end polarization modulator provide a unique combination of high sensitivity, stability, and control of systematics. The CLASS site, at 5200 m in the Chilean Atacama desert, allows for daily mapping of up to 70% of the sky and enables the characterization of CMB polarization at the largest angular scales. Using this combination of a broad frequency range, large sky coverage, control over systematics, and high sensitivity, CLASS will observe the reionization and recombination peaks of the CMB E- and B-mode power spectra. CLASS will make a cosmic variance limited measurement of the optical depth to reionization and will measure or place upper limits on the tensor-to-scalar ratio, r, down to a level of 0.01 (95% C.L.).

  12. Verification of angular dependence in MOSFET detector

    International Nuclear Information System (INIS)

    Souza, Clayton H.; Shorto, Julian M.B.; Siqueira, Paulo T.D.; Nunes, Maíra G.; Silva Junior, Iremar A.; Yoriyaz, Hélio

    2017-01-01

    In vivo dosimetry is an essential tool for quality assurance programs, being a procedure commonly performed with thermoluminescent dosimeters (TLDs) or diodes. However, a type of dosimeter that has increasing popularity in recent years is the metal-oxide-semiconductor field effect transistor (MOSFET) detector. MOSFET dosimeters fulfill all the necessary characteristics to realize in vivo dosimetry since it has a small size, good precision and feasibility of measurement, as well as easy handling. Nevertheless, its true differential is to allow reading of the dose in real time, enabling immediate intervention in the correction of physical parameters deviations and anticipation of small anatomical changes in a patient during treatment. In order for MOSFET dosimeter to be better accepted in clinical routine, information reporting performance should be available frequently. For this reason, this work proposes to verify reproducibility and angular dependence of a standard sensitivity MOSFET dosimeter (TN-502RD-H) for Cs-137 and Co-60 sources. Experimental data were satisfactory and MOSFET dosimeter presented a reproducibility of 3.3% and 2.7% (1 SD) for Cs-137 and Co-60 sources, respectively. In addition, an angular dependence of up to 6.1% and 16.3% for both radioactive sources, respectively. It is conclusive that MOSFET dosimeter TN-502RD-H has satisfactory reproducibility and a considerable angular dependence, mainly for the Co-60 source. This means that although precise measurements, special attention must be taken for applications in certain anatomical regions in a patient. (author)

  13. Angular craniometry in craniocervical junction malformation.

    Science.gov (United States)

    Botelho, Ricardo Vieira; Ferreira, Edson Dener Zandonadi

    2013-10-01

    The craniometric linear dimensions of the posterior fossa have been relatively well studied, but angular craniometry has been poorly studied and may reveal differences in the several types of craniocervical junction malformation. The objectives of this study were to evaluate craniometric angles compared with normal subjects and elucidate the main angular differences among the types of craniocervical junction malformation and the correlation between craniocervical and cervical angles. Angular craniometries were studied using primary cranial angles (basal and Boogard's) and secondary craniocervical angles (clivus canal and cervical spine lordosis). Patients with basilar invagination had significantly wider basal angles, sharper clivus canal angles, larger Boogard's angles, and greater cervical lordosis than the Chiari malformation and control groups. The Chiari malformation group does not show significant differences when compared with normal controls. Platybasia occurred only in basilar invagination and is suggested to be more prevalent in type II than in type I. Platybasic patients have a more acute clivus canal angle and show greater cervical lordosis than non-platybasics. The Chiari group does not show significant differences when compared with the control, but the basilar invagination groups had craniometric variables significantly different from normal controls. Hyperlordosis observed in the basilar inavagination group was associated with craniocervical kyphosis conditioned by acute clivus canal angles.

  14. Verification of angular dependence in MOSFET detector

    Energy Technology Data Exchange (ETDEWEB)

    Souza, Clayton H.; Shorto, Julian M.B.; Siqueira, Paulo T.D.; Nunes, Maíra G.; Silva Junior, Iremar A.; Yoriyaz, Hélio, E-mail: chsouza@usp.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2017-07-01

    In vivo dosimetry is an essential tool for quality assurance programs, being a procedure commonly performed with thermoluminescent dosimeters (TLDs) or diodes. However, a type of dosimeter that has increasing popularity in recent years is the metal-oxide-semiconductor field effect transistor (MOSFET) detector. MOSFET dosimeters fulfill all the necessary characteristics to realize in vivo dosimetry since it has a small size, good precision and feasibility of measurement, as well as easy handling. Nevertheless, its true differential is to allow reading of the dose in real time, enabling immediate intervention in the correction of physical parameters deviations and anticipation of small anatomical changes in a patient during treatment. In order for MOSFET dosimeter to be better accepted in clinical routine, information reporting performance should be available frequently. For this reason, this work proposes to verify reproducibility and angular dependence of a standard sensitivity MOSFET dosimeter (TN-502RD-H) for Cs-137 and Co-60 sources. Experimental data were satisfactory and MOSFET dosimeter presented a reproducibility of 3.3% and 2.7% (1 SD) for Cs-137 and Co-60 sources, respectively. In addition, an angular dependence of up to 6.1% and 16.3% for both radioactive sources, respectively. It is conclusive that MOSFET dosimeter TN-502RD-H has satisfactory reproducibility and a considerable angular dependence, mainly for the Co-60 source. This means that although precise measurements, special attention must be taken for applications in certain anatomical regions in a patient. (author)

  15. Energy-resolved positron annihilation for molecules

    International Nuclear Information System (INIS)

    Barnes, L.D.; Gilbert, S.J.; Surko, C.M.

    2003-01-01

    This paper presents an experimental study designed to address the long-standing question regarding the origin of very large positron annihilation rates observed for many molecules. We report a study of the annihilation, resolved as a function of positron energy (ΔE∼25 meV, full width at half maximum) for positron energies from 50 meV to several eV. Annihilation measurements are presented for a range of hydrocarbon molecules, including a detailed study of alkanes, C n H 2n+2 , for n=1-9 and 12. Data for other molecules are also presented: C 2 H 2 , C 2 H 4 ; CD 4 ; isopentane; partially fluorinated and fluorinated methane (CH x F 4-x ); 1-fluorohexane (C 6 H 13 F) and 1-fluorononane (C 9 H 19 F). A key feature of the results is very large enhancements in the annihilation rates at positron energies corresponding to the excitation of molecular vibrations in larger alkane molecules. These enhancements are believed to be responsible for the large annihilation rates observed for Maxwellian distributions of positrons in molecular gases. In alkane molecules larger than ethane (C 2 H 6 ), the position of these peaks is shifted downward by an amount ∼20 meV per carbon. The results presented here are generally consistent with a physical picture recently considered in detail by Gribakin [Phys. Rev. A 61, 022720 (2000)]. In this model, the incoming positron excites a vibrational Feshbach resonance and is temporarily trapped on the molecule, greatly enhancing the probability of annihilation. The applicability of this model and the resulting enhancement in annihilation rate relies on the existence of positron-molecule bound states. In accord with this reasoning, the experimental results presented here provide the most direct evidence to date that positrons bind to neutral molecules. The shift in the position of the resonances is interpreted as a measure of the binding energy of the positron to the molecule. Other features of the results are also discussed, including large, qualitative changes in the annihilation spectra observed when hydrocarbon molecules are fluorinated

  16. Coronagraphic Planet Finding with Energy Resolving Detectors

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose to build a 10,000 pixel MKID camera and integrate it with the Project 1640 coronagraph and the PALM-3000 adaptive optics system at the PaloMarch 200-inch...

  17. Angular-Momentum Evolution in Laser-Plasma Accelerators

    CERN Document Server

    Thaury, Cédric; Corde, Sébastien; Lehe, Rémi; Le Bouteiller, Madeleine; Ta Phuoc, Kim; Davoine, Xavier; Rax, J. M.; Rousse, Antoine; Malka, Victor

    2013-01-01

    The transverse properties of an electron beam are characterized by two quantities, the emittance which indicates the electron beam extent in the phase space and the angular momentum which allows for non-planar electron trajectories. Whereas the emittance of electron beams produced in laserplasma accelerator has been measured in several experiments, their angular momentum has been scarcely studied. It was demonstrated that electrons in laser-plasma accelerator carry some angular momentum, but its origin was not established. Here we identify one source of angular momentum growth and we present experimental results showing that the angular momentum content evolves during the acceleration.

  18. ANGULAR MOMENTUM AND GALAXY FORMATION REVISITED

    International Nuclear Information System (INIS)

    Romanowsky, Aaron J.; Fall, S. Michael

    2012-01-01

    Motivated by a new wave of kinematical tracers in the outer regions of early-type galaxies (ellipticals and lenticulars), we re-examine the role of angular momentum in galaxies of all types. We present new methods for quantifying the specific angular momentum j, focusing mainly on the more challenging case of early-type galaxies, in order to derive firm empirical relations between stellar j * and mass M * (thus extending earlier work by Fall). We carry out detailed analyses of eight galaxies with kinematical data extending as far out as 10 effective radii, and find that data at two effective radii are generally sufficient to estimate total j * reliably. Our results contravene suggestions that ellipticals could harbor large reservoirs of hidden j * in their outer regions owing to angular momentum transport in major mergers. We then carry out a comprehensive analysis of extended kinematic data from the literature for a sample of ∼100 nearby bright galaxies of all types, placing them on a diagram of j * versus M * . The ellipticals and spirals form two parallel j * -M * tracks, with log-slopes of ∼0.6, which for the spirals are closely related to the Tully-Fisher relation, but for the ellipticals derives from a remarkable conspiracy between masses, sizes, and rotation velocities. The ellipticals contain less angular momentum on average than spirals of equal mass, with the quantitative disparity depending on the adopted K-band stellar mass-to-light ratios of the galaxies: it is a factor of ∼3-4 if mass-to-light ratio variations are neglected for simplicity, and ∼7 if they are included. We decompose the spirals into disks and bulges and find that these subcomponents follow j * -M * trends similar to the overall ones for spirals and ellipticals. The lenticulars have an intermediate trend, and we propose that the morphological types of galaxies reflect disk and bulge subcomponents that follow separate, fundamental j * -M * scaling relations. This provides a

  19. ANGULAR MOMENTUM AND GALAXY FORMATION REVISITED

    Energy Technology Data Exchange (ETDEWEB)

    Romanowsky, Aaron J. [University of California Observatories, 1156 High Street, Santa Cruz, CA 95064 (United States); Fall, S. Michael [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)

    2012-12-15

    Motivated by a new wave of kinematical tracers in the outer regions of early-type galaxies (ellipticals and lenticulars), we re-examine the role of angular momentum in galaxies of all types. We present new methods for quantifying the specific angular momentum j, focusing mainly on the more challenging case of early-type galaxies, in order to derive firm empirical relations between stellar j{sub *} and mass M{sub *} (thus extending earlier work by Fall). We carry out detailed analyses of eight galaxies with kinematical data extending as far out as 10 effective radii, and find that data at two effective radii are generally sufficient to estimate total j{sub *} reliably. Our results contravene suggestions that ellipticals could harbor large reservoirs of hidden j{sub *} in their outer regions owing to angular momentum transport in major mergers. We then carry out a comprehensive analysis of extended kinematic data from the literature for a sample of {approx}100 nearby bright galaxies of all types, placing them on a diagram of j{sub *} versus M{sub *}. The ellipticals and spirals form two parallel j{sub *}-M{sub *} tracks, with log-slopes of {approx}0.6, which for the spirals are closely related to the Tully-Fisher relation, but for the ellipticals derives from a remarkable conspiracy between masses, sizes, and rotation velocities. The ellipticals contain less angular momentum on average than spirals of equal mass, with the quantitative disparity depending on the adopted K-band stellar mass-to-light ratios of the galaxies: it is a factor of {approx}3-4 if mass-to-light ratio variations are neglected for simplicity, and {approx}7 if they are included. We decompose the spirals into disks and bulges and find that these subcomponents follow j{sub *}-M{sub *} trends similar to the overall ones for spirals and ellipticals. The lenticulars have an intermediate trend, and we propose that the morphological types of galaxies reflect disk and bulge subcomponents that follow

  20. Research on static angular stiffness measurement of flexible joint

    Directory of Open Access Journals (Sweden)

    Yongchao HUANG

    2016-10-01

    Full Text Available Measurement accuracy of the angular stiffness of flexible joint is directly related to the control accuracy and sensitivity of gyro, but the traditional measurement methods have many problems. According to the principle of angular stiffness measurement of flexible joint, two static measurement methods of angular stiffness are proposed based on different loading ways, namely mechanical loading angular stiffness measurement and piezoelectric loading angular stiffness measurement. The mechanical loading angular stiffness measurement system is built by using a motor driven indexing feeding tilting table, the measure experiment if the angular stiffness of flexible joint is conducted, and the angular stiffness of flexible joint is measured. For the excessive fluctuation problem of the measure result in mechanical load test, a piezoelectric loading structure is designed and a measurement method employing piezoelectric actuator is proposed for angular stiffness measurement of flexible joint. Based on ANSYS Workbench, the displacement output of the piezoelectric loading structure is analyzed by simulations. The simulation results illustrate that the displacement output meets the requirement of static loading angular stiffness measurement of flexible joint, and the theoretical feasibility of piezoelectric loading angular stiffness measurement method is validated.

  1. Angular Rate Estimation Using a Distributed Set of Accelerometers

    Directory of Open Access Journals (Sweden)

    Sung Kyung Hong

    2011-11-01

    Full Text Available A distributed set of accelerometers based on the minimum number of 12 accelerometers allows for computation of the magnitude of angular rate without using the integration operation. However, it is not easy to extract the magnitude of angular rate in the presence of the accelerometer noises, and even worse, it is difficult to determine the direction of a rotation because the angular rate is present in its quadratic form within the inertial measurement system equations. In this paper, an extended Kalman filter scheme to correctly estimate both the direction and magnitude of the angular rate through fusion of the angular acceleration and quadratic form of the angular rate is proposed. We also provide observability analysis for the general distributed accelerometers-based inertial measurement unit, and show that the angular rate can be correctly estimated by general nonlinear state estimators such as an extended Kalman filter, except under certain extreme conditions.

  2. Angular Position Tracking Control of a Quadcopter

    OpenAIRE

    T. V. Glazkov; A. E. Golubev

    2017-01-01

    The paper dwells on tracking the quad-copter angular position with desired quality parameters of transient processes. The aerial vehicle is considered as a rigid body with six degrees of freedom.  A full rigid body quad-copter mathematical model is considered without the assumption of smallness of the Euler angles.Among the most well known methods of non-linear stabilization are feedback linearization and backstepping. The backstepping approach allows us to have an effective solution of the s...

  3. Angular Momentum Sensitive Two-Center Interference

    Science.gov (United States)

    Ilchen, M.; Glaser, L.; Scholz, F.; Walter, P.; Deinert, S.; Rothkirch, A.; Seltmann, J.; Viefhaus, J.; Decleva, P.; Langer, B.; Knie, A.; Ehresmann, A.; Al-Dossary, O. M.; Braune, M.; Hartmann, G.; Meissner, A.; Tribedi, L. C.; AlKhaldi, M.; Becker, U.

    2014-01-01

    In quantum mechanics the Young-type double-slit experiment can be performed with electrons either traveling through a double slit or being coherently emitted from two inversion symmetric molecular sites. In the latter one the valence photoionization cross sections of homonuclear diatomic molecules were predicted to oscillate over kinetic energy almost 50 years ago. Beyond the direct proof of the oscillatory behavior of these photoionization cross sections σ, we show that the angular distribution of the emitted electrons reveals hitherto unexplored information on the relative phase shift between the corresponding partial waves through two-center interference patterns.

  4. Projection of angular momentum via linear algebra

    Science.gov (United States)

    Johnson, Calvin W.; O'Mara, Kevin D.

    2017-12-01

    Projection of many-body states with good angular momentum from an initial state is usually accomplished by a three-dimensional integral. We show how projection can instead be done by solving a straightforward system of linear equations. We demonstrate the method and give sample applications to 48Cr and 60Fe in the p f shell. This new projection scheme, which is competitive against the standard numerical quadrature, should also be applicable to other quantum numbers such as isospin and particle number.

  5. The angular momentum of isolated white dwarfs

    Directory of Open Access Journals (Sweden)

    Brassard P.

    2013-03-01

    Full Text Available This is a very brief report on an ongoing program aimed at mapping the internal rotation profiles of stars through asteroseismology. Three years ago, we developed and applied successfully a new technique to the pulsating GW Vir white dwarf PG 1159−035, and were able to infer that it rotates very slowly and rigidly over some 99% of its mass. We applied the same approach to the three other GW Vir pulsators with available rotational splitting data, and found similar results. We discuss the implications of these findings on the question of the angular momentum of white dwarfs resulting from single star evolution.

  6. Models and theory for precompound angular distributions

    Energy Technology Data Exchange (ETDEWEB)

    Blann, M.; Pohl, B.A.; Remington, B.A. (Lawrence Livermore National Lab., CA (USA)); Scobel, W.; Trabandt, M. (Hamburg Univ. (Germany, F.R.). 1. Inst. fuer Experimentalphysik); Byrd, R.C. (Los Alamos National Lab., NM (USA)); Foster, C.C. (Indiana Univ. Cyclotron Facility, Bloomington, IN (USA)); Bonetti, R.; Chiesa, C. (Milan Univ. (Italy). Ist. di Fisica Generale Applicata); Grimes, S.M. (Ohio Univ

    1990-06-06

    We compare angular distributions calculated by folding nucleon- nucleon scattering kernels, using the theory of Feshbach, Kerman and Koonin, and the systematics of Kalbach, with a wide range of data. The data range from (n,xn) at 14 MeV incident energy to (p,xn) at 160 MeV incident energy. The FKK theory works well with one adjustable parameter, the depth of the nucleon-nucleon interaction potential. The systematics work well when normalized to the hybrid model single differential cross section prediction. The nucleon- nucleon scattering approach seems inadequate. 9 refs., 10 figs.

  7. Photoelectron imaging following 2 + 1 multiphoton excitation of HBr.

    Science.gov (United States)

    Romanescu, Constantin; Loock, Hans-Peter

    2006-07-07

    The photodissociation and photoionization dynamics of HBr via low-n Rydberg and ion-pair states was studied by using 2 + 1 REMPI spectroscopy and velocity map imaging of photoelectrons. Two-photon excitation at about 9.4-10 eV was used to prepare rotationally selected excited states. Following absorption of the third photon the unperturbed F (1)Delta(2) and i (3)Delta(2) states ionize directly into the ground vibrational state of the molecular ion according to the Franck-Condon principle and upon preservation of the ion core. In case of the V (1)Sigma(+)(0(+)) ion-pair state and the perturbed E (1)Sigma(+)(0(+)), g (3)Sigma(-)(0(+)), and H (1)Sigma(+)(0(+)) Rydberg states the absorption of the third photon additionally results in a long vibrational progression of HBr(+) in the X (2)Pi state as well as formation of electronically excited atomic photofragments. The vibrational excitation of the molecular ion is explained by autoionization of repulsive superexcited states into the ground state of the molecular ion. In contrast to HCl, the perturbed Rydberg states of HBr show strong participation of the direct ionization process, with ionic core preservation.

  8. Photoelectron spectra and electronic structures of some indigo dyes

    Science.gov (United States)

    Bauer, Helmut; Kowski, Klaus; Kuhn, Hubert; Lüttke, Wolfgang; Rademacher, Paul

    1998-04-01

    The He(I) photoelectron spectra of thioindigo ( 3), selenoindigo ( 4), bi(4,4-dimethyltetrahydropyrrole-3-one-2-ylidene) ( 5), bi(4,4-dimethyltetrahydrothiophene-3-one-2-ylidene) ( 6), octahydroindigo ( 8), 4,4'-dibutyl-5,5'-dimethylpyrrolindigo ( 9), and thiophenindigo ( 10) have been obtained by evaporating the compounds at temperatures up to about 350°C. The ionization potentials (IPs) are compared with those of the parent compound indigo ( 1) and are related to orbital energies or electronic states of the respective radical cations with the aid of semi-empirical SCF MO calculations. A satisfactory interpretation of the spectra is achieved with the Outer Valence Green's function method OVGF in combination with PM3 results. The first three IPs of all indigoid molecules in this study have the same origin, i.e. they relate to similar molecular orbitals. Because of the close relationship of the electronic structures of indigoid molecules, the IPs of the unknown unsubstituted pyrrolindigo ( 7) could be estimated.

  9. X-Ray Photoelectron Spectroscopic Characterization of Iron Oxide Nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Radu, T., E-mail: Teodora.Radu@itim-cj.ro [National Institute for Research and Development of Isotopic and Molecular Technologies, 67-103 Donat Street, 400293, Cluj Napoca (Romania); Iacovita, C. [Department of Pharmaceutical Physics-Biophysics, Faculty of Pharmacy, “Iuliu Hatieganu” University of Medicine and Pharmacy, 400349, Cluj-Napoca (Romania); Benea, D. [Faculty of Physics, Babes Bolyai University, 400271, Cluj-Napoca (Romania); Turcu, R. [National Institute for Research and Development of Isotopic and Molecular Technologies, 67-103 Donat Street, 400293, Cluj Napoca (Romania)

    2017-05-31

    Highlights: • Characterization of three types of iron oxides magnetic nanoparticles. • A correlation between valence band XPS and the degree of iron oxidation is proposed. • Theoretical contributions of Fe in tetragonal and octahedral environment are shown. - Abstract: We report X-ray photoelectron spectroscopy (XPS) results on iron oxide magnetic nanoparticle (Fe{sub 3}O{sub 4}) synthesized using solvothermal reduction in the presence of polyethylene glycol. The magnetite obtained was employed as precursor for the synthesis of γ-Fe{sub 2}O{sub 3} (by oxygen dissociation) which in turn was transformed into α-Fe{sub 2}O{sub 3}. We confirmed the magnetite, maghemite and hematite structure by Fourier Transformed Spectroscopy (FTIR) and X-ray diffraction (XRD). The analysis of the XPS core level and valence band (VB) photoemission spectra for all investigated samples is discussed in terms of the degree of iron oxidation. This is of fundamental importance to better understand the electronic structure of the obtained iron oxide nanoparticles in order to control and improve their quality for specific biomedical applications. Moreover, theoretical band structure calculations are performed for magnetite and the separate contributions of Fe in tetragonal and octahedral environment are shown.

  10. A proposed measurement of optical orbital and spin angular momentum and its implications for photon angular momentum

    Science.gov (United States)

    Leader, Elliot

    2018-04-01

    The expression for the total angular momentum carried by a laser optical vortex beam, splits, in the paraxial approximation, into two terms which seem to represent orbital and spin angular momentum respectively. There are, however, two very different competing versions of the formula for the spin angular momentum, one based on the use of the Poynting vector, as in classical electrodynamics, the other related to the canonical expression for the angular momentum which occurs in Quantum Electrodynamics. I analyze the possibility that a sufficiently sensitive optical measurement could decide which of these corresponds to the actual physical angular momentum carried by the beam.

  11. The Cosmology Large Angular Scale Surveyor (CLASS)

    Science.gov (United States)

    Cleary, Joseph

    2018-01-01

    The Cosmology Large Angular Scale Surveyor (CLASS) is an array of four telescopes designed to measure the polarization of the Cosmic Microwave Background. CLASS aims to detect the B-mode polarization from primordial gravitational waves predicted by cosmic inflation theory, as well as the imprint left by reionization upon the CMB E-mode polarization. This will be achieved through a combination of observing strategy and state-of-the-art instrumentation. CLASS is observing 70% of the sky to characterize the CMB at large angular scales, which will measure the entire CMB power spectrum from the reionization peak to the recombination peak. The four telescopes operate at frequencies of 38, 93, 145, and 217 GHz, in order to estimate Galactic synchrotron and dust foregrounds while avoiding atmospheric absorption. CLASS employs rapid polarization modulation to overcome atmospheric and instrumental noise. Polarization sensitive cryogenic detectors with low noise levels provide CLASS the sensitivity required to constrain the tensor-to-scalar ratio down to levels of r ~ 0.01 while also measuring the optical depth the reionization to sample-variance levels. These improved constraints on the optical depth to reionization are required to pin down the mass of neutrinos from complementary cosmological data. CLASS has completed a year of observations at 38 GHz and is in the process of deploying the rest of the telescope array. This poster provides an overview and update on the CLASS science, hardware and survey operations.

  12. Electromagnetic angular positioner based on DC micromotor

    Directory of Open Access Journals (Sweden)

    Bodnicki Maciej

    2018-01-01

    Full Text Available The presented works concerned launching of an angular positioner powered by an electromagnetic actuator, designed for performing angular micromovements within a range of few microradians. The principle of operation is based on balancing the electromagnetic torque of the motor with a torque that is twisting a compliant element. As electrodynamic actuators have no distinguished controlled positions, therefore in typical positioning systems desired positions are obtained applying a closed-loop position control. Usually, such systems employ also a feedback (dumping related to velocity of the moving elements, what simplifies forming of dynamics of the system. The design of the physical model employs a DC micromotor, whose rotor is coupled with a torsional torquemeter. A feedback signal is generated by resistive strain gauges. The paper presents a mathematical model of the positioning system, results of simulation study as well as results of experimental study. The simulation study indicates that it is possible to select such design features and such type of the micoromotor that a high dynamics of positioning is ensured.

  13. Orbital angular momentum of general astigmatic modes

    International Nuclear Information System (INIS)

    Visser, Jorrit; Nienhuis, Gerard

    2004-01-01

    We present an operator method to obtain complete sets of astigmatic Gaussian solutions of the paraxial wave equation. In case of general astigmatism, the astigmatic intensity and phase distribution of the fundamental mode differ in orientation. As a consequence, the fundamental mode has a nonzero orbital angular momentum, which is not due to phase singularities. Analogous to the operator method for the quantum harmonic oscillator, the corresponding astigmatic higher-order modes are obtained by repeated application of raising operators on the fundamental mode. The nature of the higher-order modes is characterized by a point on a sphere, in analogy with the representation of polarization on the Poincare sphere. The north and south poles represent astigmatic Laguerre-Gaussian modes, similar to circular polarization on the Poincare sphere, while astigmatic Hermite-Gaussian modes are associated with points on the equator, analogous to linear polarization. We discuss the propagation properties of the modes and their orbital angular momentum, which depends on the degree of astigmatism and on the location of the point on the sphere

  14. [Sensitivity of four representative angular cephalometric measures].

    Science.gov (United States)

    Xü, T; Ahn, J; Baumrind, S

    2000-05-01

    Examined the sensitivity of four representative cephalometric angles to the detection of different vectors of craniofacial growth. Landmark coordinate data from a stratified random sample of 48 adolescent subjects were used to calculate conventional values for changes between the pretreatment and end-of-treatment lateral cephalograms. By modifying the end-of-treatment coordinate values appropriately, the angular changes could be recalculated reflecting three hypothetical situations: Case 1. What if there were no downward landmark displacement between timepoints? Case 2. What if there were no forward landmark displacement between timepoints? Case 3. What if there were no Nasion change? These questions were asked for four representative cephalometric angles: SNA, ANB, NAPg and UI-SN. For Case 1, the associations (r) between the baseline and the modified measure for the three angles were very highly significant (P < 0.001) with r2 values no lower than 0.94! For Case 2, however, the associations were much weaker and no r value reached significance. These angular measurements are less sensitive for measuring downward landmark displacement than they are for measuring forward landmark displacement.

  15. Critique of the angular momentum sum rules and a new angular momentum sum rule

    NARCIS (Netherlands)

    Bakker, B.L.G.; Leader, E.; Trueman, T. L.

    2004-01-01

    We present a study of the tensorial structure of the hadronic matrix elements of the angular momentum operators J. Well known results in the literature are shown to be incorrect, and we have taken pains to derive the correct expressions in three different ways, two involving explicit physical wave

  16. Inefficient Angular Momentum Transport in Accretion Disk Boundary Layers: Angular Momentum Belt in the Boundary Layer

    Science.gov (United States)

    Belyaev, Mikhail A.; Quataert, Eliot

    2018-04-01

    We present unstratified 3D MHD simulations of an accretion disk with a boundary layer (BL) that have a duration ˜1000 orbital periods at the inner radius of the accretion disk. We find the surprising result that angular momentum piles up in the boundary layer, which results in a rapidly rotating belt of accreted material at the surface of the star. The angular momentum stored in this belt increases monotonically in time, which implies that angular momentum transport mechanisms in the BL are inefficient and do not couple the accretion disk to the star. This is in spite of the fact that magnetic fields are advected into the BL from the disk and supersonic shear instabilities in the BL excite acoustic waves. In our simulations, these waves only carry a small fraction (˜10%) of the angular momentum required for steady state accretion. Using analytical theory and 2D viscous simulations in the R - ϕ plane, we derive an analytical criterion for belt formation to occur in the BL in terms of the ratio of the viscosity in the accretion disk to the viscosity in the BL. Our MHD simulations have a dimensionless viscosity (α) in the BL that is at least a factor of ˜100 smaller than that in the disk. We discuss the implications of these results for BL dynamics and emission.

  17. An EM Induction Hi-Speed Rotation Angular Rate Sensor.

    Science.gov (United States)

    Li, Kai; Li, Yuan; Han, Yan

    2017-03-17

    A hi-speed rotation angular rate sensor based on an electromagnetic induction signal is proposed to provide a possibility of wide range measurement of high angular rates. An angular rate sensor is designed that works on the principle of electromagnetism (EM) induction. In addition to a zero-phase detection technique, this sensor uses the feedback principle of magnetic induction coils in response to a rotating magnetic field. It solves the challenge of designing an angular rate sensor that is suitable for both low and high rotating rates. The sensor was examined for angular rate measurement accuracy in simulation tests using a rotary table. The results show that it is capable of measuring angular rates ranging from 1 rps to 100 rps, with an error within 1.8‰ of the full scale (FS). The proposed sensor is suitable to measurement applications where the rotation angular rate is widely varied, and it contributes to design technology advancements of real-time sensors measuring angular acceleration, angular rate, and angular displacement of hi-speed rotary objects.

  18. An EM Induction Hi-Speed Rotation Angular Rate Sensor

    Directory of Open Access Journals (Sweden)

    Kai Li

    2017-03-01

    Full Text Available A hi-speed rotation angular rate sensor based on an electromagnetic induction signal is proposed to provide a possibility of wide range measurement of high angular rates. An angular rate sensor is designed that works on the principle of electromagnetism (EM induction. In addition to a zero-phase detection technique, this sensor uses the feedback principle of magnetic induction coils in response to a rotating magnetic field. It solves the challenge of designing an angular rate sensor that is suitable for both low and high rotating rates. The sensor was examined for angular rate measurement accuracy in simulation tests using a rotary table. The results show that it is capable of measuring angular rates ranging from 1 rps to 100 rps, with an error within 1.8‰ of the full scale (FS. The proposed sensor is suitable to measurement applications where the rotation angular rate is widely varied, and it contributes to design technology advancements of real-time sensors measuring angular acceleration, angular rate, and angular displacement of hi-speed rotary objects.

  19. Ionization of oriented targets by intense circularly polarized laser pulses: Imprints of orbital angular nodes in the two-dimensional momentum distribution

    DEFF Research Database (Denmark)

    Martiny, Christian; Abu-Samha, Mahmoud; Madsen, Lars Bojer

    2010-01-01

    We solve the three-dimensional time-dependent Schrödinger equation for a few-cycle circularly polarized femtosecond laser pulse that interacts with an oriented target exemplified by an argon atom, initially in a 3px or 3py state. The photoelectron momentum distributions show distinct signatures......, we show that ionization by a circularly polarized pulse completely maps out the angular nodal structure of the initial state, thus providing a potential tool for studying orbital symmetry in individual systems or during chemical reactions....

  20. Coincident photoelectron spectroscopy on superconductors; Koinzidente Photoelektronenspektroskopie an Supraleitern

    Energy Technology Data Exchange (ETDEWEB)

    Voss, Stefan

    2011-07-01

    Aim of the performed experiments of this thesis was to attempt to detect Cooper pairs as carriers of the superconducting current directly by means of the photoelectric effect. The method of the coincident photoelectron spectroscopy aims thereby at the detection of two coherently emitted electrons by the interaction with a photon. Because electrostatic analyzers typically cover only a very small spatial angle, which goes along with very low coincidence rates, in connection with this thesis a time-of-flight projection system has been developed, which maps nearly the whole spatial angle on a position-resolving detector. The pulsed light source in form of special synchrotron radiation necessary for the measurement has been adjusted so weak, that only single photons could arrive at the sample. Spectroscoped were beside test measurements on silver layers both a lead monocrystal as representative of the classical BCS superconductors and monocrystalline Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} from the family of the high-temperature superconductors. With excitation energies up to 40 eV could be shown that sufficiently smooth and clean surfaces in the superconducting phase exhibit within the resolving power of about 0.5 eV no recognizable differences in comparison to the normally conducting phase. Beside these studies furthermore the simple photoemission at the different samples and especially in the case of the lead crystal is treated, because here no comparable results are known. Thereby the whole momentum space is discussed and the Fermi surface established as three-dimensional model, by means of which the measurement results are discussed. in the theoretical descriptions different models for the Cooper-pair production are presented, whereby to the momentum exchange with the crystal a special role is attributed, because this can only occur in direct excitations via discrete lattice vectors.

  1. Development of a superconducting radio frequency photoelectron injector

    Science.gov (United States)

    Arnold, A.; Büttig, H.; Janssen, D.; Kamps, T.; Klemz, G.; Lehmann, W. D.; Lehnert, U.; Lipka, D.; Marhauser, F.; Michel, P.; Möller, K.; Murcek, P.; Schneider, Ch.; Schurig, R.; Staufenbiel, F.; Stephan, J.; Teichert, J.; Volkov, V.; Will, I.; Xiang, R.

    2007-07-01

    A superconducting radio frequency (RF) photoelectron injector (SRF gun) is under development at the Research Center Dresden-Rossendorf. This project aims mainly at replacing the present thermionic gun of the superconducting electron linac ELBE. Thereby the beam quality is greatly improved. Especially, the normalized transverse emittance can be reduced by up to one order of magnitude depending on the operating conditions. The length of the electron bunches will be shortened by about two orders of magnitude making the present bunchers in the injection beam line dispensable. The maximum obtainable bunch charge of the present thermionic gun amounts to 80 pC. The SRF gun is designed to deliver also higher bunch charge values up to 2.5 nC. Therefore, this gun can be used also for advanced facilities such as energy recovery linacs (ERLs) and soft X-ray FELs. The SRF gun is designed as a 3{1}/{2} cell cavity structure with three cells basically TESLA cells supplemented by a newly developed gun cell and a choke filter. The exit energy is projected to be 9.5 MeV. In this paper, we present a description of the design of the SRF gun with special emphasis on the physical and technical problems arising from the necessity of integrating a photocathode into the superconducting cavity structure. Preparation, transfer, cooling and alignment of the photocathode are discussed. In designing the SRF gun cryostat for most components wherever possible the technical solutions were adapted from the ELBE cryostat in some cases with major modifications. As concerns the status of the project the design is finished, most parts are manufactured and the gun is being assembled. Some of the key components are tested in special test arrangements such as cavity warm tuning, cathode cooling, the mechanical behavior of the tuners and the effectiveness of the magnetic screening of the cavity.

  2. Inhomogeneous Broadening in Perturbed Angular Correlation Spectroscopy

    Science.gov (United States)

    Bunker, Austin; Adams, Mike; Hodges, Jeffery; Park, Tyler; Stufflebeam, Michael; Evenson, William; Matheson, Phil; Zacate, Matthew

    2009-10-01

    Our research concerns the effect of a static distribution of defects on the net electric field gradient (EFG) within crystal structures. Defects and vacancies perturb the distribution of gamma rays emitted from radioactive probe nuclei within the crystal. These defects and vacancies produce a net EFG at the site of the probe which causes the magnetic quadrupole moment of the nucleus of the probe to precess about the EFG. The net EFG, which is strongly dependent upon the defect concentration, perturbs the angular correlation (PAC) of the gamma rays, and is seen in the damping of the perturbation function, G2(t), in time and broadening of the spectral peaks in the Fourier transform. We have used computer simulations to study the probability distribution of EFG tensor components in order to uncover the concentration dependence of G2(t). This in turn can be used to analyze experimental PAC data and quantitatively describe properties of the crystal.

  3. Topological photonic orbital-angular-momentum switch

    Science.gov (United States)

    Luo, Xi-Wang; Zhang, Chuanwei; Guo, Guang-Can; Zhou, Zheng-Wei

    2018-04-01

    The large number of available orbital-angular-momentum (OAM) states of photons provides a unique resource for many important applications in quantum information and optical communications. However, conventional OAM switching devices usually rely on precise parameter control and are limited by slow switching rate and low efficiency. Here we propose a robust, fast, and efficient photonic OAM switch device based on a topological process, where photons are adiabatically pumped to a target OAM state on demand. Such topological OAM pumping can be realized through manipulating photons in a few degenerate main cavities and involves only a limited number of optical elements. A large change of OAM at ˜10q can be realized with only q degenerate main cavities and at most 5 q pumping cycles. The topological photonic OAM switch may become a powerful device for broad applications in many different fields and motivate a topological design of conventional optical devices.

  4. Angular filter refractometry analysis using simulated annealing.

    Science.gov (United States)

    Angland, P; Haberberger, D; Ivancic, S T; Froula, D H

    2017-10-01

    Angular filter refractometry (AFR) is a novel technique used to characterize the density profiles of laser-produced, long-scale-length plasmas [Haberberger et al., Phys. Plasmas 21, 056304 (2014)]. A new method of analysis for AFR images was developed using an annealing algorithm to iteratively converge upon a solution. A synthetic AFR image is constructed by a user-defined density profile described by eight parameters, and the algorithm systematically alters the parameters until the comparison is optimized. The optimization and statistical uncertainty calculation is based on the minimization of the χ 2 test statistic. The algorithm was successfully applied to experimental data of plasma expanding from a flat, laser-irradiated target, resulting in an average uncertainty in the density profile of 5%-20% in the region of interest.

  5. Nuclear scissors modes and hidden angular momenta

    Energy Technology Data Exchange (ETDEWEB)

    Balbutsev, E. B., E-mail: balbuts@theor.jinr.ru; Molodtsova, I. V. [Joint Institute for Nuclear Research (Russian Federation); Schuck, P. [Université Paris-Sud, Institut de Physique Nucléaire, IN2P3–CNRS (France)

    2017-01-15

    The coupled dynamics of low-lying modes and various giant resonances are studied with the help of the Wigner Function Moments method generalized to take into account spin degrees of freedom and pair correlations simultaneously. The method is based on Time-Dependent Hartree–Fock–Bogoliubov equations. The model of the harmonic oscillator including spin–orbit potential plus quadrupole–quadrupole and spin–spin interactions is considered. New low-lying spin-dependent modes are analyzed. Special attention is paid to the scissors modes. A new source of nuclear magnetism, connected with counter-rotation of spins up and down around the symmetry axis (hidden angular momenta), is discovered. Its inclusion into the theory allows one to improve substantially the agreement with experimental data in the description of energies and transition probabilities of scissors modes.

  6. Angular reduction in multiparticle matrix elements

    International Nuclear Information System (INIS)

    Lehman, D.R.; Parke, W.C.

    1989-01-01

    A general method for reduction of coupled spherical harmonic products is presented. When the total angular coupling is zero, the reduction leads to an explicitly real expression in the scalar products of the unit vector arguments of the spherical harmonics. For nonscalar couplings, the reduction gives Cartesian tensor forms for the spherical harmonic products; tensors built from the physical vectors in the original expression. The reduction for arbitrary couplings is given in closed form, making it amenable to symbolic manipulation on a computer. The final expressions do not depend on a special choice of coordinate axes, nor do they contain azimuthal quantum number summations, or do they have complex tensor terms for couplings to a scalar; consequently, they are easily interpretable from the properties of the physical vectors they contain

  7. Chiral symmetries associated with angular momentum

    International Nuclear Information System (INIS)

    Bhattacharya, M; Kleinert, M

    2014-01-01

    In quantum mechanics courses, symmetries of a physical system are usually introduced as operators which commute with the Hamiltonian. In this paper we will consider chiral symmetries which anticommute with the Hamiltonian. Typically, introductory courses at the (under)graduate level do not discuss these simple, useful and beautiful symmetries at all. The first time a student encounters them is when the Dirac equation is discussed in a course on relativistic quantum mechanics, or when particle–hole symmetry is studied in the context of superconductivity. In this paper, we will show how chiral symmetries can be simply elucidated using the theory of angular momentum, which is taught in virtually all introductory quantum mechanics courses. (paper)

  8. Cierre angular primario: opciones quirúrgicas

    Directory of Open Access Journals (Sweden)

    Henry Pérez-González

    2014-10-01

    Full Text Available Se realizó una revisión bibliográfica con el objetivo de exponer las principales opciones quirúrgicas en el tratamiento del cierre angular primario efectuando una búsqueda de los principales artículos científicos de los últimos años, así como de la literatura impresa que incluye el tema, siendo seleccionados los contenidos más relevantes para la confección del informe final. Las opciones de tratamiento incluyen la cirugía láser (iridotomía, iridoplastia y la cirugía incisional (filtrante, extracción del cristalino, dependiendo de los factores fisiopatológicos involucrados y la forma clínica en el momento del diagnóstico.

  9. Untangling Galaxy Components - The Angular Momentum Parameter

    Science.gov (United States)

    Tabor, Martha; Merrifield, Michael; Aragon-Salamanca, Alfonso

    2017-06-01

    We have developed a new technique to decompose Integral Field spectral data cubes into separate bulge and disk components, allowing us to study the kinematic and stellar population properties of the individual components and how they vary with position. We present here the application of this method to a sample of fast rotator early type galaxies from the MaNGA integral field survey, and demonstrate how it can be used to explore key properties of the individual components. By extracting ages, metallicities and the angular momentum parameter lambda of the bulges and disks, we show how this method can give us new insights into the underlying structure of the galaxies and discuss what this can tell us about their evolution history.

  10. Angular biasing in implicit Monte-Carlo

    International Nuclear Information System (INIS)

    Zimmerman, G.B.

    1994-01-01

    Calculations of indirect drive Inertial Confinement Fusion target experiments require an integrated approach in which laser irradiation and radiation transport in the hohlraum are solved simultaneously with the symmetry, implosion and burn of the fuel capsule. The Implicit Monte Carlo method has proved to be a valuable tool for the two dimensional radiation transport within the hohlraum, but the impact of statistical noise on the symmetric implosion of the small fuel capsule is difficult to overcome. We present an angular biasing technique in which an increased number of low weight photons are directed at the imploding capsule. For typical parameters this reduces the required computer time for an integrated calculation by a factor of 10. An additional factor of 5 can also be achieved by directing even smaller weight photons at the polar regions of the capsule where small mass zones are most sensitive to statistical noise

  11. Angular Position Tracking Control of a Quadcopter

    Directory of Open Access Journals (Sweden)

    T. V. Glazkov

    2017-01-01

    Full Text Available The paper dwells on tracking the quad-copter angular position with desired quality parameters of transient processes. The aerial vehicle is considered as a rigid body with six degrees of freedom.  A full rigid body quad-copter mathematical model is considered without the assumption of smallness of the Euler angles.Among the most well known methods of non-linear stabilization are feedback linearization and backstepping. The backstepping approach allows us to have an effective solution of the stabilization problems with uncertainties available in the system. However, in synthesis of the feedback through backstepping, there is still an urgent issue: how to ensure desirable quality of transients in the closed-loop system. The paper presents a solution of this problem using as an example the tracking a given (programmed change of the angular position of a quad-copter.The control algorithms obtained in this paper are implemented using the Rolling Spider MATLAB Toolbox (ROSMAT tool package on the Parrot Rolling Spider quad-copter. A numerical simulation and experiments have shown the efficiency of obtained control laws, with the transient processes taking into account the desired quality indicators. However, the experiments showed that lack of terms in the mathematical model to describe the aerodynamic effects, resulted in the instability of the quad-copter flight near the obstacle (the effect of the reflected airflow.Further research can be aimed at solving the control problem in question using a mathematical model of the quad-copter motion that takes into account various aerodynamic effects.One of the potential application areas for the theoretical results, obtained in the paper, is to solve the problems of automatic control of unmanned aerial vehicles.

  12. Photoelectron diffraction studies of small adsorbates on single crystal surfaces

    International Nuclear Information System (INIS)

    Pascal, Mathieu

    2002-01-01

    The structural determination of small molecules adsorbed on single crystal surfaces has been investigated using scanned energy mode photoelectron diffraction (PhD). The experimental PhD data were compared to theoretical models using a simulation program based on multiple scattering calculations. Three adsorption systems have been examined on Ag(110), Cu(110) and Cu(111) crystals. The structure of the (2x1)-O adsorption phase on Ag(110) revealed that the O atoms occupied the long bridge site and are almost co-planar with the top layer of Ag atoms. The best agreement between multiple scattering theory and experiment has been obtained for a missing-row (or equivalently an 'added- row') reconstruction. Alternative buckled-row and unreconstructed surface models can be excluded. The adsorption of the benzoate species on Cu(110) has been found to occur via the carboxylate group. The molecules occupy short bridge sites with the O atoms being slightly displaced from atop sites and are aligned along the close-packed azimuth. The tilt of the molecule with respect to the surface and the degree to which the surface is relaxed have also been investigated. The adsorption of methyl on Cu(111) was studied using either azomethane or methyl iodide to prepare the surface layers. At saturation coverage the preferred adsorption site is the fcc threefold hollow site, whereas at half saturation coverage ∼ 30 % of the methyl species occupy the hop threefold hollow sites. Best agreement between theory and experiment corresponded to a methyl group adsorbed with C 3v symmetry. The height of the C above the surface in a pure methyl layer was 1.66 ± 0.02 A, but was reduced to 1.62 ± 0.02 A in the presence of co-adsorbed iodine, suggesting that iodine increases the strength of adsorption. Iodine was also found to occupy the fee threefold hollow sites with a Cu-l bondlength of 2.61 ± 0.02 A. (author)

  13. Photoelectron spectroscopy on doped organic semiconductors and related interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Olthof, Selina Sandra

    2010-06-08

    Using photoelectron spectroscopy, we show measurements of energy level alignment of organic semiconducting layers. The main focus is on the properties and the influence of doped layers. The investigations on the p-doping process in organic semiconductors show typical charge carrier concentrations up to 2.10{sup 20} cm{sup -3}. By a variation of the doping concentration, an over proportional influence on the position of the Fermi energy is observed. Comparing the number of charge carriers with the amount of dopants present in the layer, it is found that only 5% of the dopants undergo a full charge transfer. Furthermore, a detailed investigation of the density of states beyond the HOMO onset reveals that an exponentially decaying density of states reaches further into the band gap than commonly assumed. For an increasing amount of doping, the Fermi energy gets pinned on these states which suggests that a significant amount of charge carriers is present there. The investigation of metal top and bottom contacts aims at understanding the asymmetric current-voltage characteristics found for some symmetrically built device stacks. It can be shown that a reaction between the atoms from the top contact with the molecules of the layer leads to a change in energy level alignment that produces a 1.16 eV lower electron injection barrier from the top. Further detailed investigations on such contacts show that the formation of a silver top contact is dominated by diffusion processes, leading to a broadened interface. However, upon insertion of a thin aluminum interlayer this diffusion can be stopped and an abrupt interface is achieved. Furthermore, in the case of a thick silver top contact, a monolayer of molecules is found to oat on top of the metal layer, almost independent on the metal layer thickness. Finally, several device stacks are investigated, regarding interface dipoles, formation of depletion regions, energy alignment in mixed layers, and the influence of the built

  14. Corrosion and degradation studies utilizing X-ray photoelectron spectroscopy

    Science.gov (United States)

    Hixson, Holly Gwyndolen

    1997-08-01

    This dissertation involves studies of corrosion behavior at the surface of various metal samples, as well as the degradation of wool fibers obtained from the Star-Spangled Banner. Molybdenum metal and iron-zinc alloys were examined under corrosive conditions, and the degradation of the wool fibers was studied. The behavior of a polished molybdenum metal surface upon exposure to both aerated and deaerated water and 1.0 M NaCl solution was studied by X-ray Photoelectron Spectroscopy (XPS). Exposure to deaerated water and NaCl failed to produce oxidation of the metal surfaces, but exposing the polished metal surface to aerated water produced significant oxidation. Metal surfaces cleaned by argon-ion etching were found to be inert to oxidation by aerated water. The etching process also appears to passivate the metal surface. The behavior of molybdenum metal in 0.5 M Hsb2SOsb4 treated at various potentials has been studied using core and valence band XPS. The study indicates that Mosp{IV} and Mosp{VI} (including possibly Mosp{V} in some cases) were formed as the potential of the system was increased within the active range of molybdenum. The corrosive behavior of iron-zinc alloys that have been electroplated on plain steel in both aerated and deaerated quadruply-distilled water has been studied using XPS. Several different iron-zinc alloys were electroplated for comparative purposes: an iron-rich alloy, a zinc-rich alloy, and an alloy of similar iron and zinc composition. Treatment in aerated water produces oxidation for the iron-rich and similar composition alloys, but the oxide is reduced for the zinc-rich alloy. Degradation of the fibers in the original Star-Spangled Banner has been monitored using XPS and Scanning Electron Microscopy (SEM). Comparison of white and red wool fibers and linen fibers from the flag with new, mechanically-abraded, and chemically-treated white, red, and linen fibers, respectively, was performed in an attempt to determine the fibers' levels

  15. Evaluation of Photoelectron Therapy Effect on Hepatocellular Carcinoma

    Directory of Open Access Journals (Sweden)

    bahram Mofid

    2007-10-01

    Full Text Available Mofid B1, Navabpoor M2, Alizadeh Azimi M3 1. Assistant professor, Department of Radiotherapy, Faculty of Para-Medicine, Shahid Beheshti University of medical sciences 2. Instructor, Department of Technology of radiology, Faculty of Para-Medicine, Shahid Beheshti University of medical sciences Abstract Background: Photoelectron therapy method has been usad successfully, on the body phantom, cancer cells culture and animals. In this method, drugs containing x-Ray opaque factors–with high atomic numbers–are injected into the patient’s vein. After appropriate drug accumulation, about at least ten percent of the total injected amounts, 200kev. up to 300kev. of localized x-Ray beams is radiated to the site of the tumor. The Ethic Committee of Shahid Beheshti University of Medical Education and Health Services authorized the implementation of this new cancer treatment method, initially only on the group of patients who suffered from hepato-cellular carcinoma. Hepato cellular carcinoma is one of the most current malignancies of liver. In some cases, in addition to surgery, several approaches exist to come near the aim of predominating hepato-cellular carcinoma such as chemotherapy, current Radiation Therapy, Radio-Frequency application (RF, Trans-Artepical Chemo Embolization, (TACE, and Percutaneous Ethanol Injection (PEI. The effectiveness of the above-mentioned methods is about 10%-47%, applied alone or along side each other. Materials and methods: This study was a clinical-trial one. In this study, first, lipiodol (an x-ray opaque material with a high atomic number was transferred into the main vessel terminating to the tumor by angio-catheterization. Then,200kev. up to 250kev. of localized x-ray was radiated to the site of the tumor in one session. The drug volume was proportionally selected to the volume of the tumor, and the irradiation intensity was between 400 to 600cent.Gy. the beam energy absorption capacity of this drug is as times as

  16. Renner-Teller effects in the photoelectron spectra of CNC, CCN, and HCCN.

    Science.gov (United States)

    Coudert, Laurent H; Gans, Bérenger; Garcia, Gustavo A; Loison, Jean-Christophe

    2018-02-07

    The line intensity of photoelectron spectra when either the neutral or cationic species display a Renner-Teller coupling is derived and applied to the modeling of the photoelectron spectra of CNC, CCN, and HCCN. The rovibronic energy levels of these three radicals and of their cations are investigated starting from ab initio results. A model treating simultaneously the bending mode and the overall rotation is developed to deal with the quasilinearity problem in CNC + , CCN + , and HCCN and accounts for the large amplitude nature of their bending mode. This model is extended to treat the Renner-Teller coupling in CNC, CCN, and HCCN + . Based on the derived photoelectron line intensity, the photoelectron spectra of all three molecules are calculated and compared to the experimental ones.

  17. A study of the valence shell photoelectron and photoabsorption spectra of CF3SF5

    International Nuclear Information System (INIS)

    Holland, D M P; Shaw, D A; Walker, I C; McEwen, I J; Apra, E; Guest, M F

    2005-01-01

    The outer valence shell photoelectron spectrum of CF 3 SF 5 has been studied experimentally and theoretically. Synchrotron radiation has been used to record angle-resolved outer valence shell photoelectron spectra of CF 3 SF 5 in the photon energy range 18-60 eV. These spectra have allowed photoelectron asymmetry parameters and branching ratios to be derived. The Outer Valence Green's Function approach has been employed to calculate the molecular orbital configuration and associated binding energies. A charge distribution analysis has also been obtained. Assignments have been proposed for the peaks observed in the photoelectron spectrum. The absolute photoabsorption cross section of CF 3 SF 5 has been measured from threshold to 40 eV, and strongly resembles that of SF 6 . Assignments, involving intravalence transitions, have been proposed for some of the principal features appearing in the photoabsorption spectrum of CF 3 SF 5

  18. Angular correlations between recoil velocity and angular momentum vectors in molecular photodissociation

    Science.gov (United States)

    Hall, G. E.; Sivakumar, N.; Chawla, D.; Houston, P. L.; Burak, I.

    1988-03-01

    A technique has been developed for determining the angular correlation between a photofragment's angular momentum vector J, its recoil velocity vector v, and the transition dipole moment of the parent molecule μp . Doppler profile spectroscopy used in conjunction with laser-induced fluorescence probing by polarized light can be used to determine the correlations. The pairwise correlations between these vectors as well as their triple correlation are discussed for limiting cases using a classical approach as well as for the general case using a quantum approach based on density matrices. The current formulations differ in two ways from the recent approach of Dixon, who used a bipolar expansion of the correlated velocity and angular momentum distributions. The physical basis for the influence of the vector correlations on the Doppler profile is somewhat more transparent in the current formulations, and the direct connection between the measured correlations and the t-matrix elements occurring in the theory of Balint-Kurti and Shapiro for the photodissociation of a triatomic molecule is also demonstrated.

  19. Electronic structures of 1-adamantanol, cyclohexanol and cyclohexanone and anisotropic interactions with He*(23S) atoms: collision-energy-resolved Penning ionization electron spectroscopy combined with quantum chemistry calculations

    International Nuclear Information System (INIS)

    Tian Shanxi; Kishimoto, Naoki; Ohno, Koichi

    2002-01-01

    He I ultraviolet photoelectron spectra and He*(2 3 S) Penning ionization electron spectra have been measured for 1-adamantanol, cyclohexanol and cyclohexanone. Four stable isomeric conformers of cyclohexanol were predicted by Becke's three-parameter hybrid density functional B3LYP/6-31+G(d,p) calculations. Since the orbital reactivity in Penning ionizations is simply related to the electron density extending outside the molecular surface, the theoretical Penning ionization electron spectra were synthesized using the calculated molecular orbital wave functions and ionization potentials. They were in good agreement with the experimental spectra except for the low-electron-energy bands. Collision energy dependence of partial ionization cross sections for the oxygen lone pair orbitals exhibited that there are strong steric hindrances by the neighboring hydrogen atoms in 1-adamantanol and cyclohexanol

  20. Inheritance of resistance to angular leaf spot in yellow beans ...

    African Journals Online (AJOL)

    Angular leaf spot (Phaeoisariopsis griseola (Sacc) is an important disease of common bean (Phaseolus vulgaris L.) in most parts of Africa, causing yield losses of 40-80%. This study was carried out to determine the inheritance of resistance to angular leaf spot in yellow beans. Biparental crosses were done between ...

  1. Prospects of Measuring the Angular Power Spectrum of the Diffuse ...

    Indian Academy of Sciences (India)

    Review. J. Astrophys. Astr. (2016) 37: 35. DOI: 10.1007/s12036-016-9413-x. Prospects of Measuring the Angular Power Spectrum of the Diffuse. Galactic .... In this section we briefly review the Tapered Gridded Estimator (TGE), the details ... of the product of the primary beam pattern A(θ) and δI(θ) the angular fluctuation.

  2. Measuring Average Angular Velocity with a Smartphone Magnetic Field Sensor

    Science.gov (United States)

    Pili, Unofre; Violanda, Renante

    2018-01-01

    The angular velocity of a spinning object is, by standard, measured using a device called a tachometer. However, by directly using it in a classroom setting, the activity is likely to appear as less instructive and less engaging. Indeed, some alternative classroom-suitable methods for measuring angular velocity have been presented. In this paper,…

  3. A kinematic model for calculating the magnitude of angular ...

    African Journals Online (AJOL)

    Keplerian velocity laws imply the existence of velocity shear and shear viscosity within an accretion disk. Due to this viscosity, angular momentum is transferred from the faster moving inner regions to the slower-moving outer regions of the disk. Here we have formulated a model for calculating the magnitude of angular ...

  4. Learning web development with Bootstrap and AngularJS

    CERN Document Server

    Radford, Stephen

    2015-01-01

    Whether you know a little about Bootstrap or AngularJS, or you're a complete beginner, this book will enhance your capabilities in both frameworks and you'll build a fully functional web app. A working knowledge of HTML, CSS, and JavaScript is required to fully get to grips with Bootstrap and AngularJS.

  5. 3D printed bio-inspired angular acceleration sensor

    NARCIS (Netherlands)

    van Tiem, Joël; Groenesteijn, Jarno; Sanders, Remco G.P.; Krijnen, Gijsbertus J.M.

    2015-01-01

    Abstract—We present a biomimetic angular acceleration sensor inspired by the vestibular system, as found e.g. in mammals and fish. The sensor consist of a fluid filled circular channel. When exposed to angular accelerations the fluid flows relative to the channel. Read-out is based on

  6. inheritance of resistance to angular leaf spot in yellow beans ...

    African Journals Online (AJOL)

    Prof. Adipala Ekwamu

    Susceptible. II -indeterminate erect; III -indeterminate semi-prostate; ALS = Angular leaf spot. Isolation of Phaeoisariopsis griseola and plant inoculation. Isolation of angular leaf spot was made from lesions of naturally infected bean leaves showing fungal sporulation. In the case of non-sporulating lesions, the fungus was.

  7. Angular sensitivity of blowfly photoreceptors : broadening by artificial electrical coupling

    NARCIS (Netherlands)

    Smakman, J.G.J.; Stavenga, D.G.

    1987-01-01

    1. Electrical coupling between R1-6 photoreceptors was investigated by measuring angular sensitivities and quantum bumps. 2. Recordings were made from two extreme types of cells: Type a: cells with a diffraction-like angular sensitivity profile. Only large bumps could be obtained from these cells.

  8. Epidemiology Of Angular Deformities Of The Knee In Children In ...

    African Journals Online (AJOL)

    Background: Bony problems such as angular deformities and metabolic bone disease are of high frequency in Nigeria. Objective: The aim of this study was to define the pattern of presentation in children with angular deformities of the knee. Methodology: It was an 18-month prospective study involving children aged ...

  9. Fundamental methods to measure the orbital angular momentum of light

    NARCIS (Netherlands)

    Berkhout, Gregorius Cornelis Gerardus (Joris)

    2011-01-01

    Light is a ubiquitous carrier of information. This information can be encoded in the intensity, direction, frequency and polarisation of the light and, which was described more recently, in its orbital angular momentum. Although creating light beams with orbital angular momentum is relatively easy,

  10. Structure determination by photoelectron diffraction of small molecules on surfaces

    International Nuclear Information System (INIS)

    Booth, N.A.

    1998-05-01

    The synchrotron radiation based technique of Photoelectron Diffraction (PhD) has been applied to three adsorption systems. Structure determinations, are presented for each system which involve the adsorption of small molecules on the low index {110} plane of single crystal Cu and Ni substrates. For the NH 3 -Cu(110) system PhD was successful in determining a N-Cu bondlength of 2.05 ± 0.03 A as well as values for the anisotropic vibrational amplitudes of the N and an expansion of the 1st to 2nd Cu substrate layer spacing from the bulk value of 0.08 ± 0.08 A. The most significant and surprising structural parameter determined for this system was that the N atom occupies an asymmetric adsorption site. Rather than being situated in the expected high symmetry atop site the N atom was found to be offset parallel to the surface by 0.37 ± 0.12 A in the [001] azimuth. In studying the glycine-Cu(110) system the adsorption structure of an amino-acid has been quantified. The local adsorption geometries of all the atoms involved in the molecule to surface bond have been determined. The glycine molecule is found to be bonded to the surface via both its amino and carboxylate functional groups. The molecule straddles two [11-bar0] rows of the Cu substrate. The two O atoms are found to be in identical sites both approximately atop Cu atoms on the [11-bar0] rows offset parallel to the surface by 0.80 ± 0.05 A in the [001] azimuth, the O-Cu bondlength was found to be 2.03 ± 0.05 A. The N atom was also found to adsorb in an approximately atop geometry but offset parallel to the surface by 0.24 ± 0.10A in the [11-bar0] direction, the N-Cu bondlength was found to be 2.05± 0.05 A. PhD was unsuccessful in determining the positions of the two C atoms that form a bridge between the two functional groups bonded to the surface due to difficulties in separating the two inequivalent contributions to the final intensity modulation function. For the CN-Ni(110) system both PhD and Near Edge

  11. Optical communications beyond orbital angular momentum

    Science.gov (United States)

    Rosales-Guzmán, Carmelo; Trichili, Abderrahmen; Dudley, Angela; Ndagano, Bienvenu; Ben Salem, Amine; Zghal, Mourad; Forbes, Andrew

    2016-09-01

    Current optical communication technologies are predicted to face a bandwidth capacity limit in the near future. The nature of the limitation is fundamental rather than technological and is set by nonlinearities in optical fibers. One solution, suggested over 30 years ago, comprises the use of spatial modes of light as information carriers. Along this direction, light beams endowed with orbital angular momentum (OAM) have been demonstrated as potential information carriers in both, free space and fibres. However, recent studies suggest that purely OAM modes does not increase the bandwidth of optical communication systems. In fact, in all work to date, only the azimuthal component of transverse spatial modes has been used. Crucially, all transverse spatial modes require two degrees of freedom to be described; in the context of Laguerre-Gaussian (LGp`) beams these are azimuthal (l) and radial (p), the former responsible for OAM. Here, we demonstrate a technique where both degrees of freedom of LG modes are used as information carrier over free space. We transfer images encoded using 100 spatial modes in three wavelengths as our basis, and employ a spatial demultiplexing scheme that detects all 100 modes simultaneously. Our scheme is a hybrid of MIMO and SMM, and serves as a proof-of-principle demonstration. The cross-talk between the modes is small and independent of whether OAM modes are used or not.

  12. CLASS: The Cosmology Large Angular Scale Surveyor

    Science.gov (United States)

    Essinger-Hileman, Thomas; Ali, Aamir; Amiri, Mandana; Appel, John W.; Araujo, Derek; Bennett, Charles L.; Boone, Fletcher; Chan, Manwei; Cho, Hsiao-Mei; Chuss, David T.; hide

    2014-01-01

    The Cosmology Large Angular Scale Surveyor (CLASS) is an experiment to measure the signature of a gravitational wave background from inflation in the polarization of the cosmic microwave background (CMB). CLASS is a multi-frequency array of four telescopes operating from a high-altitude site in the Atacama Desert in Chile. CLASS will survey 70% of the sky in four frequency bands centered at 38, 93, 148, and 217 GHz, which are chosen to straddle the Galactic-foreground minimum while avoiding strong atmospheric emission lines. This broad frequency coverage ensures that CLASS can distinguish Galactic emission from the CMB. The sky fraction of the CLASS survey will allow the full shape of the primordial B-mode power spectrum to be characterized, including the signal from reionization at low-length. Its unique combination of large sky coverage, control of systematic errors, and high sensitivity will allow CLASS to measure or place upper limits on the tensor-to-scalar ratio at a level of r = 0:01 and make a cosmic-variance-limited measurement of the optical depth to the surface of last scattering, tau. (c) (2014) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

  13. Angular distributions of sputtered particles from NiTi alloy

    International Nuclear Information System (INIS)

    Neshev, I.; Hamishkeev, V.; Chernysh, V.S.; Postnikov, S.; Mamaev, B.

    1993-01-01

    The angular distributions of sputtered Ni and Ti from a polycrystalline NiTi (50-50%) alloy are investigated by Auger electron spectroscopy and Rutherford backscattering spectroscopy. A difference in the angular distributions is observed with Ni being sputtered preferentially near the surface normal. A computer program for the calculation of the angular distributions of constituents sputtered from binary targets is created and used. The mechanisms responsible for the observed differences in the angular distributions are discussed. It is found that the collisional cascade theory is not directly applicable to the results of the constituents' angular distributions obtained in the presence of oxygen. The fitted coefficients of bombardment-induced segregation are found to be greater than the experimentally obtained ones. (author)

  14. Carrier-envelope phase dependent photoelectron energy spectra in low intensity regime.

    Science.gov (United States)

    Li, Yang; Li, Min; Zhou, Yueming; Ma, Xiaomeng; Xie, Hui; Lan, Pengfei; Lu, Peixiang

    2017-05-15

    We study the carrier-envelope phase (CEP) dependent photoelectron energy spectra from above-threshold ionization by numerically solving the time-dependent Schrödinger equation of hydrogen atom in a few-cycle laser field at intensities in the range of (2-10) × 10 13 W/cm 2 . Depending on the electron energy and the laser intensity, the yield of the photoelectron reveals clear oscillations with respect to the CEP. At high laser intensities (larger than ~3 × 10 13 W/cm 2 ), the yield of the high-energy photoelectrons (larger than 2U p , with U p being the ponderomotive potential) shows two kinds of oscillations with the CEP for different electron energies. There is a clear phase jump for those two kinds of oscillations. In contrast, at low laser intensities (smaller than ~3 × 10 13 W/cm 2 ), the phase of the oscillation for the high-energy photoelectron yield with the CEP is nearly independent on the electron energy, which will reduce the sensitivity of the retrieval of single-shot CEP using the method reported by T. Wittmann et al. [Nat. Phys. 5, 357 (2009)] at low laser intensities. We further show that the low-energy photoelectrons display distinct CEP-dependent intercycle interference fringes, providing an alternative approach to retrieve the CEP with high sensitivity in a few-cycle laser field with low intensity.

  15. DEVELOPMENT OF NEXT-GENERATION DETECTORS AND INSTRUMENTATION FOR PHOTOELECTRON SPECTROSCOPY, DIFFRACTION AND HOLOGRAPHY

    International Nuclear Information System (INIS)

    Charles S. Fadley, Principal Investigator

    2005-01-01

    We have developed a new multichannel detector for use in photoelectron spectroscopy (as well as other types of high-count-rate spectroscopy) that will operate at rates of up to 1 GHz. Such detectors are crucial to the full utilization of the high-brightness radiation generated by third-generation synchrotron radiation sources. In addition, new software and hardware has been developed to permit rapidly and accurately scanning photoelectron spectra that will be accumulated in as little as a 200 micros. A versatile next-generation sample goniometer permitting equally rapid scanning of specimen angles or photon energies for angle-resolved photoemission studies, photoelectron diffraction, and photoelectron holography measurements, and cooling to below 10K has also been designed and constructed. These capabilities have been incorporated into a unique photoelectron spectrometer/diffractometer at the Advanced Light Source of the Lawrence Berkeley National Laboratory; this experimental system includes ultrahigh energy resolution, in situ rotation, variable polarization, and optional spin detection. This overall system is now being used in studies of a variety of problems including magnetic metals and oxides; metal/metal, metal/metal oxide, and metal-oxide/metal-oxide multilayers; and systems exhibiting giant and colossal magnetoresistance

  16. Adiabatic theory of strong-field photoelectron momentum distributions near a backward rescattering caustic

    Science.gov (United States)

    Morishita, Toru; Tolstikhin, Oleg I.

    2017-11-01

    We present a comprehensive treatise on the derivation of the factorization formula describing strong-field photoelectron momentum distributions near the outermost backward rescattering caustic within the adiabatic theory and its validation by calculations. The formula derived holds for ionization by linearly polarized laser pulses of sufficiently low frequency and becomes exact as the frequency tends to zero for a fixed pulse amplitude. The convergence of the results obtained from the formula to accurate photoelectron momentum distributions obtained by solving the time-dependent Schrödinger equation is demonstrated. The formula is shown to work quantitatively in both tunneling and over-the-barrier regimes of ionization for finite-range potentials as well as potentials with a Coulomb tail. This paves the way for future applications of the present theory in strong-field physics. In particular, the explicit analytical form of the returning photoelectron wave packet given here enables one to extract differential cross sections for elastic scattering of a photoelectron on the parent ion from experimental photoelectron momentum distributions.

  17. Spin Rate of a Racquetball Due To Angular Impact

    Directory of Open Access Journals (Sweden)

    Dolev Illouz

    2014-12-01

    Full Text Available The relationship between the impact angle of a racquetball and the resulting angular velocity of the ball was investigated. Impact angles ranging from 0° to 80° were tested. The ball was dropped at constant speed on a plywood board that could be angled and the impact was filmed at 600 fps. The video was then analyzed to determine the angular velocity of the ball after the bounce. It was found that there is a proportional relationship between the incoming impact angle (θ and angular velocity (ω of the racquetball, for angles up to 50°, indicating that the ball did not slip during impact at these angles.

  18. Control of Angular Intervals for Angle-Multiplexed Holographic Memory

    Science.gov (United States)

    Kinoshita, Nobuhiro; Muroi, Tetsuhiko; Ishii, Norihiko; Kamijo, Koji; Shimidzu, Naoki

    2009-03-01

    In angle-multiplexed holographic memory, the full width at half maximum of the Bragg selectivity curves is dependent on the angle formed between the medium and incident laser beams. This indicates the possibility of high density and high multiplexing number by varying the angular intervals between adjacent holograms. We propose an angular interval scheduling for closely stacking holograms into medium even when the angle range is limited. We obtained bit error rates of the order of 10-4 under the following conditions: medium thickness of 1 mm, laser beam wavelength of 532 nm, and angular multiplexing number of 300.

  19. Fission fragment angular distribution in heavy ion induced fission

    Directory of Open Access Journals (Sweden)

    S. Soheyli

    2006-06-01

    Full Text Available   We have calculated the fission fragment angular anisotropy for 16O + 232Th,12C + 236U , 11B + 237 Np , 14 N + 232 Th , 11B + 235U , 12C + 232Th systems with the saddle point statistical model and compared the fission fragment angular anisotropy for these systems. This comparison was done with two methods a without neutron correction and b with neutron correction. Also we studied normal and anomalous behavior of the fission fragment angular anisotropy. Finally, we have predicted the average emitted neutron from compound nuclei considering the best fit for each system.

  20. Fission fragment angular distribution in heavy ion induced fission

    OpenAIRE

    S. Soheyli; I. Ziaeian

    2006-01-01

      We have calculated the fission fragment angular anisotropy for 16O + 232Th,12C + 236U , 11B + 237 Np , 14 N + 232 Th , 11B + 235U , 12C + 232Th systems with the saddle point statistical model and compared the fission fragment angular anisotropy for these systems. This comparison was done with two methods a) without neutron correction and b) with neutron correction. Also we studied normal and anomalous behavior of the fission fragment angular anisotropy. Finally, we have predicted the averag...

  1. Angular absorption of iridium - ICW12 needles: practical considerations

    International Nuclear Information System (INIS)

    Szymczyk, W.; Lesiak, J.

    1984-01-01

    An analysis was made of two potential sources of error in Ir 192 dosimetry: the effect of angular absorption and the differences in the ionization constants found in literature. Corrections for selfabsorption in the ICW12 iridium source were determined from measurements and calculations. It was found that the decrease in the dose caused by the angular absorption in the central therapeutic area of a typical implantation can exceed 5 percent. The need for employing the concept of ''constant exposure rate'' is stressed as well as that for using angular absorption in the form of absorption. 13 refs., 6 figs., 1 tab. (author)

  2. Molecular photoionisation using synchrotron radiation. Photoelectron photoion coincidence and circular dichroism

    CERN Document Server

    Garcia-Macias, G A

    2002-01-01

    The first ionisation potential of the CF sub 3 radical has been determined in this work from the appearance potential of the CF sub 3 sup + fragment, formed in the photofragmentation of CF sub 3 Br. In obtaining this value special care has been taken in removing the contributions from second order light and internal energy of the fragmenting parent ion. The resulting ionisation potential was found to be in very good agreement with a number of recent theoretical calculations. The valence photoelectron spectra of three monoterpenes such as limonene, carvone and camphor have been recorded along with their mass spectra taken in coincidence with energy selected photoelectrons, providing information about state selected parent ion fragmentation channels. A new photoelectron spectrometer based on the Alien box design has been studied by ray-tracing simulations. It will include a two dimensional position sensitive detector system consisting in two micro channel plates in a chevron stack and a delay-line anode to enco...

  3. Transient photoelectron spectroscopy of the dissociative Br2(1Piu) state.

    Science.gov (United States)

    Strasser, Daniel; Goulay, Fabien; Leone, Stephen R

    2007-11-14

    Photodissociation of bromine on the Br2(1Piu) state is probed with ultrafast extreme ultraviolet (53.7 nm) single-photon ionization. Time-resolved photoelectron spectra show simultaneously the depletion of ground state bromine molecules as well as the rise of Br(2P3/2) products due to 402.5 nm photolysis. A partial photoionization cross-section ratio of atomic versus molecular bromine is obtained. Transient photoelectron spectra of a dissociative wave packet on the excited state are presented in the limit of low-power-density, single-photon excitation to the dissociative state. Transient binding energy shifts of "atomic-like" photoelectron peaks are observed and interpreted as photoionization of nearly separated Br atom pairs on the Br2(1Piu) state to repulsive dissociative ionization states.

  4. Photoelectron spectra as a probe of double-core resonsance in two-electron atoms

    International Nuclear Information System (INIS)

    Grobe, R.; Haan, S.L.; Eberly, J.H.

    1996-01-01

    The authors calculate photoelectron spectra for a two-electron atom under the influence of two external driving fields, using an essential states formalism. They focus on the regime of so-called coherence transfer, in which electron-electron correlation transfers field-induced photo-coherence from one electron to the other. In the case studied here, two laser fields are resonant with coupled atomic transitions, in the manner familiar from three-level dark-state spectroscopy. Dynamical two electron effects are monitored via the photoelectron energy spectrum. The authors show that the distribution of the photoelectron energies can be singly, doubly or triply peaked depending on the relative laser intensities. The electron spectra are independent of the turn-on sequence of the fields

  5. Photoelectron and photodissociation studies of free atoms and molecules, using synchrotron radiation

    Energy Technology Data Exchange (ETDEWEB)

    Medhurst, Laura Jane [Univ. of California, Berkeley, CA (United States)

    1991-11-01

    High resolution synchrotron radiation and Zero-Kinetic-Energy Photoelectron spectroscopy were used to study two-electron transitions in atomic systems at their ionization thresholds. Using this same technique the core-ionized mainline and satellite states of N2 and CO were studied with vibrational resolution. Vibrationally resolved synchrotron radiation was used to study the dissociation of N2, C2H4, and CH3Cl near the N 1s and C 1s thresholds. The photoelectron satellites of the argon 3s, krypton 4s and xenon 4d subshells were studied with zero kinetic energy photoelectron spectroscopy at their ionization thresholds. In all of these cases, satellites with lower binding energies are enhanced at their thresholds while those closer to the double ionization threshold are suppressed relative to their intensities at high incident light energies.

  6. Photoelectron and photodissociation studies of free atoms and molecules, using synchrotron radiation

    International Nuclear Information System (INIS)

    Medhurst, L.J.

    1991-11-01

    High resolution synchrotron radiation and Zero-Kinetic-Energy Photoelectron spectroscopy were used to study two-electron transitions in atomic systems at their ionization thresholds. Using this same technique the core-ionized mainline and satellite states of N 2 and CO were studied with vibrational resolution. Vibrationally resolved synchrotron radiation was used to study the dissociation of N 2 , C 2 H 4 , and CH 3 Cl near the N 1s and C 1s thresholds. The photoelectron satellites of the argon 3s, krypton 4s and xenon 4d subshells were studied with zero kinetic energy photoelectron spectroscopy at their ionization thresholds. In all of these cases, satellites with lower binding energies are enhanced at their thresholds while those closer to the double ionization threshold are suppressed relative to their intensities at high incident light energies

  7. Photoelectron and photodissociation studies of free atoms and molecules, using synchrotron radiation

    Energy Technology Data Exchange (ETDEWEB)

    Medhurst, L.J.

    1991-11-01

    High resolution synchrotron radiation and Zero-Kinetic-Energy Photoelectron spectroscopy were used to study two-electron transitions in atomic systems at their ionization thresholds. Using this same technique the core-ionized mainline and satellite states of N{sub 2} and CO were studied with vibrational resolution. Vibrationally resolved synchrotron radiation was used to study the dissociation of N{sub 2}, C{sub 2}H{sub 4}, and CH{sub 3}Cl near the N 1s and C 1s thresholds. The photoelectron satellites of the argon 3s, krypton 4s and xenon 4d subshells were studied with zero kinetic energy photoelectron spectroscopy at their ionization thresholds. In all of these cases, satellites with lower binding energies are enhanced at their thresholds while those closer to the double ionization threshold are suppressed relative to their intensities at high incident light energies.

  8. Observations of OI 7774 emission excited by conjugate photoelectrons. [ionosonde data analhysis

    Science.gov (United States)

    Christensen, A. B.

    1975-01-01

    Observations and computer calculations of O I 7774 A airglow emissions excited by conjugate photoelectrons have been carried out. The observations were made at McDonald Observatory, Texas using a 2 m grille spectrometer from December 1972 to June 1973. The zenithal emission intensity during conjugate photoelectron precipitation was fairly constant at 2-4 R until conjugate sunset, after which it diminished steadily and ceased near a conjugate solar zenith angle of 105 (plus or minus 3) deg. A predawn enhancement in both O I 7774 A and forbidden O I 6300 A was observed to commence near 102 deg. The computations utilize the two-stream technique of Nagy and Banks (1970) to obtain the escaping photoelectron flux and the local excitation rates of the oxygen emissions. Good agreement with the observations is obtained for the dependence of the emission rate on conjugate solar zenith angle.

  9. Characterization of EUV irradiation effects on polystyrene derivatives studied by x-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS)

    Science.gov (United States)

    Yamamoto, Hiroki; Kozawa, Takahiro; Tagawa, Seiichi

    2011-04-01

    The trade-off among resolution, sensitivity, and line edge roughness (LER) is the most serious problem in actualization of extreme ultraviolet (EUV). As feature sizes are reduced, it becomes very strict to simultaneously meet these requirements. Also, reaction in resist materials induced by EUV photon is more complicate. In chemically amplified EUV resists, not acid generator but polymers mainly adsorbed EUV photons. The secondary electrons are generated from polymer upon exposure to ionizing radiation such as EUV radiation and electron beam. Therefore, the increase in secondary electrons generated by EUV photons adsorbed in resist film is very important factor in the resist design. Therefore, it is essential to know the ionization mechanisms of backbone polymers and understand the reaction mechanism in details in order to accomplish high sensitivity and ultra-fine pattern in EUV lithography. We investigated the photoelectron spectra of typical backbone polymers for chemically amplified EUV resists using ultraviolet photoelectron spectroscopy (UPS). Also, the structure degradations in polystyrene (PS) derivatives thin films induced by EUV radiation were analyzed by X-ray photoelectron spectroscopy (XPS) and UPS.

  10. Helicons in uniform fields. II. Poynting vector and angular momenta

    Science.gov (United States)

    Stenzel, R. L.; Urrutia, J. M.

    2018-03-01

    The orbital and spin angular momenta of helicon modes have been determined quantitatively from laboratory experiments. The current density is obtained unambiguously from three dimensional magnetic field measurements. The only approximation made is to obtain the electric field from Hall Ohm's law which is usually the case for low frequency whistler modes. This allows the evaluation of the Poynting vector from which the angular momentum is obtained. Comparing two helicon modes (m = 0 and m = 1), one can separate the contribution of angular momentum of a rotating and non-rotating wave field. The orbital angular momentum is important to assess the wave-particle interaction by the transverse Doppler shift of rotating waves which has not been considered so far.

  11. Angular Momentum Transport in Quasi-Keplerian Accretion Disks ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    Keplerian accretion disk yield results that are inconsistent with the generally accepted model. If correct, the ideas proposed by Hayashi &. Matsuda would radically alter our understanding of the nature of the angular momentum transport in the disk, ...

  12. Application of instantaneous angular acceleration to diesel engine fault diagnosis

    Science.gov (United States)

    Ren, Yunpeng; Hu, Tianyou; Liu, Xin

    2005-12-01

    Diesel engine is a kind of important power generating machine, of which the running state monitoring and fault diagnosis attracts increasing attention. The theory and the method of diesel engine fault diagnosis based on angular acceleration measurement were studied, since angular acceleration contains a lot of information for diesel engine fault diagnosing and its power balance evaluating. USB data acquisition system was designed for the angular acceleration measurement, and it was composed with AVRAT09S8515 micro-processor and PDIUSBD12 USB interface IC. At the same time, the high speed micro-processor AVRAT09S8515 with unique function of automatically capturing the rising or falling edge of square wave was studied, and it was utilized in the diesel engine's crankshaft angular acceleration measuring system. The software and hardware of the whole system was designed, which supplied a whole solution to diesel engine fault diagnosis and power balance evaluation between each cylinder.

  13. Dissipation of angular momentum in light heavy ion collision

    International Nuclear Information System (INIS)

    Bhattacharya, C.; Bhattacharya, S.; Bhattacharjee, T.; Dey, A.; Kundu, S.; Krishan, K.; Banerjee, S.R.; Das, P.; Basu, S.K.

    2003-01-01

    The fragment emission has been studied and is reported how angular momentum dissipation can be estimated in a model independent manner using additional information from the fusion-fission component of the fragment emission data

  14. The search for and registration of superweak angular ground motions

    International Nuclear Information System (INIS)

    Budagov, J.; Lyablin, M.; Shirkov, G.

    2013-01-01

    The Earth's surface angular oscillations of the seismic, industrial and terrestrial origins have been registered with the high-resolution inclinometer of a new design concept. The microseismic peak was first recognized in the ground microradian motion

  15. Large-uncertainty intelligent states for angular momentum and angle

    International Nuclear Information System (INIS)

    Goette, Joerg B; Zambrini, Roberta; Franke-Arnold, Sonja; Barnett, Stephen M

    2005-01-01

    The equality in the uncertainty principle for linear momentum and position is obtained for states which also minimize the uncertainty product. However, in the uncertainty relation for angular momentum and angular position both sides of the inequality are state dependent and therefore the intelligent states, which satisfy the equality, do not necessarily give a minimum for the uncertainty product. In this paper, we highlight the difference between intelligent states and minimum uncertainty states by investigating a class of intelligent states which obey the equality in the angular uncertainty relation while having an arbitrarily large uncertainty product. To develop an understanding for the uncertainties of angle and angular momentum for the large-uncertainty intelligent states we compare exact solutions with analytical approximations in two limiting cases

  16. Efficient evaluation of angular power spectra and bispectra

    Science.gov (United States)

    Assassi, Valentin; Simonović, Marko; Zaldarriaga, Matias

    2017-11-01

    Angular statistics of cosmological observables are hard to compute. The main difficulty is due to the presence of highly-oscillatory Bessel functions which need to be integrated over. In this paper, we provide a simple and fast method to compute the angular power spectrum and bispectrum of any observable. The method is based on using an FFTlog algorithm to decompose the momentum-space statistics onto a basis of power-law functions. For each power law, the integrals over Bessel functions have a simple analytical solution. This allows us to efficiently evaluate these integrals, independently of the value of the multipole l. In particular, this method significantly speeds up the evaluation of the angular bispectrum compared to existing methods. To illustrate our algorithm, we compute the galaxy, lensing and CMB temperature angular power spectrum and bispectrum.

  17. The decay of orbital angular momentum entanglement in atmospheric turbulence

    CSIR Research Space (South Africa)

    Roux, FS

    2013-07-01

    Full Text Available Salam International Centre for Theoretical Physics, Trieste, Italy, 8-12 July 2013 The decay of orbital angular momentum entanglement in atmospheric turbulence Roux FS CSIR, National Laser Centre, Pretoria, 0001 Corresponding email: FSroux...

  18. Pluto Moons exhibit Orbital Angular Momentum Quantization per Mass

    Directory of Open Access Journals (Sweden)

    Potter F.

    2012-10-01

    Full Text Available The Pluto satellite system of the planet plus five moons is shown to obey the quan- tum celestial mechanics (QCM angular momentum per mass quantization condition predicted for any gravitationally bound system.

  19. Design and Implementation of a Digital Angular Rate Sensor

    Directory of Open Access Journals (Sweden)

    Zhen Peng

    2010-10-01

    Full Text Available With the aim of detecting the attitude of a rotating carrier, the paper presents a novel, digital angular rate sensor. The sensor consists of micro-sensing elements (gyroscope and accelerometer, signal processing circuit and micro-processor (DSP2812. The sensor has the feature of detecting three angular rates of a rotating carrier at the same time. The key techniques of the sensor, including sensing construction, sensing principles, and signal processing circuit design are presented. The test results show that the sensor can sense rolling, pitch and yaw angular rate at the same time and the measurement error of yaw (or pitch angular rate and rolling rate of the rotating carrier is less than 0.5%.

  20. The Effects of Isokinetic Strength Training on Strength at Different Angular Velocities: a Pilot Study

    Directory of Open Access Journals (Sweden)

    Tuğba Kocahan

    2017-09-01

    Conclusion: It was shown that angular velocity is important in isokinetic training, and that training at high angular velocities provides strength increases at lower angular velocities, but would not increase strength at angular velocities above the training level. For this reason, it is thought that in the preparation of an isokinetic strength training protocol, angular velocities need to be taken into account. For any athlete, the force at the angular velocity required in her/his sports branch needs to be considered.

  1. Spacecraft Angular Velocity Estimation Algorithm Based on Orientation Quaternion Measurements

    Directory of Open Access Journals (Sweden)

    M. V. Li

    2016-01-01

    Full Text Available The spacecraft (SC mission involves providing the appropriate orientation and stabilization of the associated axes in space. One of the main sources of information for the attitude control system is the angular rate sensor blocks. One way to improve a reliability of the system is to provide a back up of the control algorithms in case of failure of these blocks. To solve the problem of estimation of SP angular velocity vector in the inertial system of coordinates with a lack of information from the angular rate sensors is supposed the use of orientation data from the star sensors; in this case at each clock of the onboard digital computer. The equations in quaternions are used to describe the kinematics of rotary motion. Their approximate solution is used to estimate the angular velocity vector. Methods of modal control and multi-dimensional decomposition of a control object are used to solve the problem of observation and identification of the angular rates. These methods enabled us to synthesize the SP angular velocity vector estimation algorithm and obtain the equations, which relate the error quaternion with the calculated estimate of the angular velocity. Mathematical modeling was carried out to test the algorithm. Cases of different initial conditions were simulated. Time between orientation quaternion measurements and angular velocity of the model was varied. The algorithm was compared with a more accurate algorithm, built on more complete equations. Graphs of difference in angular velocity estimation depending on the number of iterations are presented. The difference in angular velocity estimation is calculated from results of the synthesized algorithm and the algorithm for more accurate equations. Graphs of error distribution for angular velocity estimation with initial conditions being changed are also presented, and standard deviations of estimation errors are calculated. The synthesized algorithm is inferior in accuracy assessment to

  2. The adsorption of mercury on tungsten (100) studied by ultra-violet photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Egelhoff, W.F. Jr.; Perry, D.L.; Linnett, J.W.

    1976-01-01

    In recent years, photoelectron spectroscopy has been applied to the study of adsorption on several metal surfaces. A popular choice of substrate has been the 100 face of single crystal tungsten, since adsorption on this surface has been well-characterised by a wide variety of experimental techniques. In this letter a study of the adsorption of mercury on W(100) by ultra-violet photoelectron spectroscopy (UPS) is reported. These results, seen in the context of previous UPS studies of chemisorption, show a number of interesting features. (Auth.)

  3. Photoelectron interference fringes by super intense x-ray laser pulses

    International Nuclear Information System (INIS)

    Toyota, Koudai; Morishita, Toru; Watanabe, Shinichi; Tolstikhin, Oleg I

    2009-01-01

    The photoelectron spectra of H - produced by circularly polarized strong high-frequency laser pulses are theoretically studied. An oscillating substructure in the above-threshold ionization (ATI) peaks is observed, which extends the validity of the earlier findings in the 1D calculations [K. Toyota et al., Phys. Rev. A 76, 043418 (2007)] and 3D calculations for linear polarization [O. I. Tolstikhin, Phys. Rev. A 77, 032712 (2008)]. Its origin is due to an interference between a pair of photoelectron wave packets created in the rising and falling part of the pulse, which appears clearly in the stabilization regime.

  4. A Very Fast and Angular Momentum Conserving Tree Code

    Energy Technology Data Exchange (ETDEWEB)

    Marcello, Dominic C., E-mail: dmarce504@gmail.com [Department of Physics and Astronomy, and Center for Computation and Technology Louisiana State University, Baton Rouge, LA 70803 (United States)

    2017-09-01

    There are many methods used to compute the classical gravitational field in astrophysical simulation codes. With the exception of the typically impractical method of direct computation, none ensure conservation of angular momentum to machine precision. Under uniform time-stepping, the Cartesian fast multipole method of Dehnen (also known as the very fast tree code) conserves linear momentum to machine precision. We show that it is possible to modify this method in a way that conserves both angular and linear momenta.

  5. Single crystal analyser accepting the narrowest neutron angular profile

    International Nuclear Information System (INIS)

    Abbas, Sohrab; Wagh, Apoorva G.; Strobl, Markus; Treimer, Wolfgang

    2007-01-01

    We have designed, fabricated and tested a novel silicon single crystal analyser. It accepts a 0.21 arcsec (FWHM) wide angular profile of a monochromatic 5.24 A neutron beam, in agreement with its design. This is the narrowest and sharpest acceptance angular profile attained to date in the world with a neutron analyser. This analyser will facilitate SUSANS experiments probing wave vector transfers Q ∼ 10 -6 A -1 . (author)

  6. Gamma-gamma angular correlation measurement in the 100 Ru

    International Nuclear Information System (INIS)

    Kenchian, G.

    1990-01-01

    An angular correlation automatic spectrometer with two Ge(Li) detectors has been developed. The spectrometer moves automatically, controlled by a microcomputer. The gamma-gamma directional angular correlations of coincidence transitions have been measured in 100 Ru nuclide, following the β + and electron capture of 100 Rh. The 100 Rh source has been produced with 100 Ru(p,n) 100 Rh reaction, using the proton beam of the Cyclotron Accelerator insiding in 100 Ru isotope. (author)

  7. A Very Fast and Angular Momentum Conserving Tree Code

    International Nuclear Information System (INIS)

    Marcello, Dominic C.

    2017-01-01

    There are many methods used to compute the classical gravitational field in astrophysical simulation codes. With the exception of the typically impractical method of direct computation, none ensure conservation of angular momentum to machine precision. Under uniform time-stepping, the Cartesian fast multipole method of Dehnen (also known as the very fast tree code) conserves linear momentum to machine precision. We show that it is possible to modify this method in a way that conserves both angular and linear momenta.

  8. The Angular Momentum of Baryons and Dark Matter Halos Revisited

    Science.gov (United States)

    Kimm, Taysun; Devriendt, Julien; Slyz, Adrianne; Pichon, Christophe; Kassin, Susan A.; Dubois, Yohan

    2011-01-01

    Recent theoretical studies have shown that galaxies at high redshift are fed by cold, dense gas filaments, suggesting angular momentum transport by gas differs from that by dark matter. Revisiting this issue using high-resolution cosmological hydrodynamics simulations with adaptive-mesh refinement (AMR), we find that at the time of accretion, gas and dark matter do carry a similar amount of specific angular momentum, but that it is systematically higher than that of the dark matter halo as a whole. At high redshift, freshly accreted gas rapidly streams into the central region of the halo, directly depositing this large amount of angular momentum within a sphere of radius r = 0.1R(sub vir). In contrast, dark matter particles pass through the central region unscathed, and a fraction of them ends up populating the outer regions of the halo (r/R(sub vir) > 0.1), redistributing angular momentum in the process. As a result, large-scale motions of the cosmic web have to be considered as the origin of gas angular momentum rather than its virialised dark matter halo host. This generic result holds for halos of all masses at all redshifts, as radiative cooling ensures that a significant fraction of baryons remain trapped at the centre of the halos. Despite this injection of angular momentum enriched gas, we predict an amount for stellar discs which is in fair agreement with observations at z=0. This arises because the total specific angular momentum of the baryons (gas and stars) remains close to that of dark matter halos. Indeed, our simulations indicate that any differential loss of angular momentum amplitude between the two components is minor even though dark matter halos continuously lose between half and two-thirds of their specific angular momentum modulus as they evolve. In light of our results, a substantial revision of the standard theory of disc formation seems to be required. We propose a new scenario where gas efficiently carries the angular momentum generated

  9. Layer-resolved photoelectron diffraction: electron attenuation anisotropy in GaAs

    Czech Academy of Sciences Publication Activity Database

    Bartoš, Igor; Cukr, Miroslav; Jiříček, Petr

    2012-01-01

    Roč. 185, 5-7 (2012), 184-187 ISSN 0368-2048 Grant - others:AVČR(CZ) Praemium Academiae Institutional research plan: CEZ:AV0Z10100521 Keywords : low-energy electron attenuation in GaAs * layer-resolved photoelectron diffraction * synchrotron radiation Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.706, year: 2012

  10. Ion clearing and photoelectron production in the 200 MeV SXLS ring

    International Nuclear Information System (INIS)

    Halama, H.; Bozoki, E.

    1991-01-01

    The design of the SXLS clearing system and its behavior are presented. In normal 200 MeV operation, clearing electrode current is dominated by photoelectrons. Clearing electrodes appear essential only in several locations but not in the dipoles. The effect of clearing voltage on the tune and the beam profile is also discussed. 4 refs., 5 figs

  11. An analytical investigation: Effect of solar wind on lunar photoelectron sheath

    Science.gov (United States)

    Mishra, S. K.; Misra, Shikha

    2018-02-01

    The formation of a photoelectron sheath over the lunar surface and subsequent dust levitation, under the influence of solar wind plasma and continuous solar radiation, has been analytically investigated. The photoelectron sheath characteristics have been evaluated using the Poisson equation configured with population density contributions from half Fermi-Dirac distribution of the photoemitted electrons and simplified Maxwellian statistics of solar wind plasma; as a consequence, altitude profiles for electric potential, electric field, and population density within the photoelectron sheath have been derived. The expression for the accretion rate of sheath electrons over the levitated spherical particles using anisotropic photoelectron flux has been derived, which has been further utilized to characterize the charging of levitating fine particles in the lunar sheath along with other constituent photoemission and solar wind fluxes. This estimate of particle charge has been further manifested with lunar sheath characteristics to evaluate the altitude profile of the particle size exhibiting levitation. The inclusion of solar wind flux into analysis is noticed to reduce the sheath span and altitude of the particle levitation; the dependence of the sheath structure and particle levitation on the solar wind plasma parameters has been discussed and graphically presented.

  12. UV photoelectron yield spectroscopy of chalcopyrite structure Cu-In-Se thin films

    International Nuclear Information System (INIS)

    Kohiki, Shigemi; Nishitani, Mikihiko; Negami, Takayuki; Wada, Takahiro; Monjushiro, Hideaki; Watanabe, Iwao; Yokoyama, Yu

    1994-01-01

    Surface-sensitive UV photoelectron yield spectroscopy was employed to study electron acceptor levels at surfaces of chalcopyrite structure Cu-In-Se thin films. Surface Fermi level pinning was observed for Cu-rich films. Shallow acceptor levels ascribable to defects Cu In and V Cu were observed for near-stoichiometric and In-rich films respectively. (orig.)

  13. A coupled bunch instability due to beam-photoelectron interactions in KEKB-LER

    Energy Technology Data Exchange (ETDEWEB)

    Ohmi, Kazuhito [National Lab. for High Energy Physics, Tsukuba, Ibaraki (Japan)

    1996-08-01

    LER of KEKB is designed to storage the positron beam of 2.6 A with multibunch operation. Nb = 3.3 x 10{sup 10} positrons are filled in a bunch and the bunch passes every 2ns through a beam chamber. The photoelectron instability may be serious for KEKB-LER. We consider a motion of photoelectrons produced by a bunch with a computer simulation technic. A cylindrical chamber with a diameter of 10 cm was used as a model chamber. About 15 times of the photoelectrons were produced by a bunch. The wake force was calculated for the loading bunches with displacements of 0.5 mm and 1 mm. The wake characteristics seems to be caused by the trapped electrons kicked by the loading bunch. The wake was saturated with the loading displacement of 0.5 mm. We obtained a growth rate by the wake force. It is very high rate, 2500s{sup -1} which exceeds damping rates of various mechanism, radiation, head-tail and feedback. Perhaps it is essential to remove the photoelectrons around the positron beam explicitly. If we apply magnetic field fo about 20 G, the growth rate will be reduced. (S.Y.)

  14. Photoelectronic properties of HgI 2 crystals for nuclear radiation ...

    Indian Academy of Sciences (India)

    Photoelectronic properties of red mercuric iodide single crystals, grown from its saturated solution in tetrahydrofuran, have been studied for the wavelength range 450-700 nm at temperatures 80, 110, 175, 235 and 300 K. Various aspects of the optical generation of charge carriers have been discussed. The computer ...

  15. Near surface composition of some alloys by X-ray photoelectron ...

    Indian Academy of Sciences (India)

    0.70Ni0.30) and BiSb (Bi0.80Sb0.20, Bi0.64Sb0.34, Bi0.55Sb0.45) are determined by X-ray photoelectron spectroscopy. The stoichiometries are determined and are compared with the bulk compositions. Possible sources of systematic errors ...

  16. Determination of strain localization in aluminum alloys using laser-induced photoelectron emission

    Science.gov (United States)

    Cai, M.; Langford, S. C.; Levine, L. E.; Dickinson, J. T.

    2004-12-01

    Uniaxial tensile deformation of oxidized aluminum produces low work-function patches of fresh metal which can be probed by measurements of photoelectron emission during exposure to ultraviolet light. We report measurements of photoelectron emission during uniaxial testing of polycrystalline Al(1200), Al-Mn(3003), Al-Mg(5052), and Al-Mg-Si(6061) alloys where the broad face of the gauge section is exposed to pulsed excimer laser radiation (248nm). We show that strain localization alters the distribution of fresh surface metal produced by subsequent deformation. The transition from more homogenous deformation to the principally localized deformation associated with shear bands is associated with a discontinuity in the growth rate of photoelectron intensities versus time. At this transition, the rate of fresh metal production along the illuminated portion of gauge section decreases. In all four materials, the strain at the discontinuity is somewhat below the strain given by the Considère criterion, consistent with the role of microstructural effects in strain localization. We suggest that these photoelectron measurements constrain quantitative models of strain localization.

  17. Photoelectron spectroscopy investigations of pyrrolo[1,2-a][1,10]phenanthroline derivatives

    Energy Technology Data Exchange (ETDEWEB)

    Prelipceanu, M.; Prelipceanu, O.S. [University of Applied Sciences Wildau, Department of Engineering, Institute of Photonics and Physics Technologies, Friedrich-Engels Street 63, 15745 Wildau (Germany); Leontie, L. [Faculty of Physics, ' Al.I. Cuza' University, 11 Carol I Boulevard, 700506 Iasi (Romania)], E-mail: lleontie@uaic.ro; Danac, R. [Faculty of Chemistry, ' Al.I. Cuza' University, 11 Carol I Boulevard, 700506 Iasi (Romania)

    2007-08-20

    Thin films of new pyrrolo[1,2-a][1,10]phenanthroline derivatives have been investigated by ultraviolet photoelectron spectroscopy, with a view of future applications in optoelectronic devices. The electronic band structure of investigated compounds (for electron energies {<=}25 eV) is to a great extent determined by substituent (R = NO{sub 2}, Cl) induced transformations of molecular orbitals.

  18. Isotropic gates and large gamma detector arrays versus angular distributions

    International Nuclear Information System (INIS)

    Iacob, V.E.; Duchene, G.

    1997-01-01

    Angular information extracted from in-beam γ ray measurements are of great importance for γ ray multipolarity and nuclear spin assignments. In our days large Ge detector arrays became available allowing the measurements of extremely weak γ rays in almost 4π sr solid angle (e.g., EUROGAM detector array). Given the high detector efficiency it is common for the mean suppressed coincidence multiplicity to reach values as high as 4 to 6. Thus, it is possible to gate on particular γ rays in order to enhance the relative statistics of a definite reaction channel and/or a definite decaying path in the level scheme of the selected residual nucleus. As compared to angular correlations, the conditioned angular distribution spectra exhibit larger statistics because in the latter the gate-setting γ ray may be observed by all the detectors in the array, relaxing somehow the geometrical restrictions of the angular correlations. Since the in-beam γ ray emission is anisotropic one could inquire that gate setting as mentioned above, based on anisotropic γ ray which would perturb the angular distributions in the unfolded events. As our work proved, there is no reason to worry about this if the energy gate runs over the whole solid angle in an ideal 4π sr detector, i.e., if the gate is isotropic. In real quasi 4π sr detector arrays the corresponding quasi isotropic gate preserves the angular properties of the unfolded data, too. However extraction of precise angular distribution coefficient especially a 4 , requires the consideration of the deviation of the quasi isotropic gate relative to the (ideal) isotropic gate

  19. Smoothed dissipative particle dynamics with angular momentum conservation

    International Nuclear Information System (INIS)

    Müller, Kathrin; Fedosov, Dmitry A.; Gompper, Gerhard

    2015-01-01

    Smoothed dissipative particle dynamics (SDPD) combines two popular mesoscopic techniques, the smoothed particle hydrodynamics and dissipative particle dynamics (DPD) methods, and can be considered as an improved dissipative particle dynamics approach. Despite several advantages of the SDPD method over the conventional DPD model, the original formulation of SDPD by Español and Revenga (2003) [9], lacks angular momentum conservation, leading to unphysical results for problems where the conservation of angular momentum is essential. To overcome this limitation, we extend the SDPD method by introducing a particle spin variable such that local and global angular momentum conservation is restored. The new SDPD formulation (SDPD+a) is directly derived from the Navier–Stokes equation for fluids with spin, while thermal fluctuations are incorporated similarly to the DPD method. We test the new SDPD method and demonstrate that it properly reproduces fluid transport coefficients. Also, SDPD with angular momentum conservation is validated using two problems: (i) the Taylor–Couette flow with two immiscible fluids and (ii) a tank-treading vesicle in shear flow with a viscosity contrast between inner and outer fluids. For both problems, the new SDPD method leads to simulation predictions in agreement with the corresponding analytical theories, while the original SDPD method fails to capture properly physical characteristics of the systems due to violation of angular momentum conservation. In conclusion, the extended SDPD method with angular momentum conservation provides a new approach to tackle fluid problems such as multiphase flows and vesicle/cell suspensions, where the conservation of angular momentum is essential

  20. Initial angular momentum and flow in high energy nuclear collisions

    Science.gov (United States)

    Fries, Rainer J.; Chen, Guangyao; Somanathan, Sidharth

    2018-03-01

    We study the transfer of angular momentum in high energy nuclear collisions from the colliding nuclei to the region around midrapidity, using the classical approximation of the color glass condensate (CGC) picture. We find that the angular momentum shortly after the collision (up to times ˜1 /Qs , where Qs is the saturation scale) is carried by the "β -type" flow of the initial classical gluon field, introduced by some of us earlier. βi˜μ1∇iμ2-μ2∇iμ1 (i =1 ,2 ) describes the rapidity-odd transverse energy flow and emerges from Gauss's law for gluon fields. Here μ1 and μ2 are the averaged color charge fluctuation densities in the two nuclei, respectively. Interestingly, strong coupling calculations using anti-de Sitter/conformal field theory (AdS/CFT) techniques also find an energy flow term featuring this particular combination of nuclear densities. In classical CGC the order of magnitude of the initial angular momentum per rapidity in the reaction plane, at a time 1 /Qs , is |d L2/d η |≈ RAQs-3ɛ¯0/2 at midrapidity, where RA is the nuclear radius, and ɛ¯0 is the average initial energy density. This result emerges as a cancellation between a vortex of energy flow in the reaction plane aligned with the total angular momentum, and energy shear flow opposed to it. We discuss in detail the process of matching classical Yang-Mills results to fluid dynamics. We will argue that dissipative corrections should not be discarded to ensure that macroscopic conservation laws, e.g., for angular momentum, hold. Viscous fluid dynamics tends to dissipate the shear flow contribution that carries angular momentum in boost-invariant fluid systems. This leads to small residual angular momentum around midrapidity at late times for collisions at high energies.

  1. Smoothed dissipative particle dynamics with angular momentum conservation

    Energy Technology Data Exchange (ETDEWEB)

    Müller, Kathrin, E-mail: k.mueller@fz-juelich.de; Fedosov, Dmitry A., E-mail: d.fedosov@fz-juelich.de; Gompper, Gerhard, E-mail: g.gompper@fz-juelich.de

    2015-01-15

    Smoothed dissipative particle dynamics (SDPD) combines two popular mesoscopic techniques, the smoothed particle hydrodynamics and dissipative particle dynamics (DPD) methods, and can be considered as an improved dissipative particle dynamics approach. Despite several advantages of the SDPD method over the conventional DPD model, the original formulation of SDPD by Español and Revenga (2003) [9], lacks angular momentum conservation, leading to unphysical results for problems where the conservation of angular momentum is essential. To overcome this limitation, we extend the SDPD method by introducing a particle spin variable such that local and global angular momentum conservation is restored. The new SDPD formulation (SDPD+a) is directly derived from the Navier–Stokes equation for fluids with spin, while thermal fluctuations are incorporated similarly to the DPD method. We test the new SDPD method and demonstrate that it properly reproduces fluid transport coefficients. Also, SDPD with angular momentum conservation is validated using two problems: (i) the Taylor–Couette flow with two immiscible fluids and (ii) a tank-treading vesicle in shear flow with a viscosity contrast between inner and outer fluids. For both problems, the new SDPD method leads to simulation predictions in agreement with the corresponding analytical theories, while the original SDPD method fails to capture properly physical characteristics of the systems due to violation of angular momentum conservation. In conclusion, the extended SDPD method with angular momentum conservation provides a new approach to tackle fluid problems such as multiphase flows and vesicle/cell suspensions, where the conservation of angular momentum is essential.

  2. High energy photoelectron spectroscopy in basic and applied science: Bulk and interface electronic structure

    International Nuclear Information System (INIS)

    Knut, Ronny; Lindblad, Rebecka; Gorgoi, Mihaela; Rensmo, Håkan; Karis, Olof

    2013-01-01

    Highlights: •We demonstrate how hard X-ray photoelectron spectroscopy can be used to investigate interface properties of multilayers. •By combining HAXPES and statistical methods we are able to provide quantitative analysis of the interface diffusion process. •We show how photoionization cross sections can be used to map partial density of states contributions to valence states. •We use HAXPES to provide insight into the valence electronic structure of e.g. multiferroics and dye-sensitized solar cells. -- Abstract: With the access of new high-performance electron spectrometers capable of analyzing electron energies up to the order of 10 keV, the interest for photoelectron spectroscopy has grown and many new applications of the technique in areas where electron spectroscopies were considered to have limited use have been demonstrated over the last few decades. The technique, often denoted hard X-ray photoelectron spectroscopy (HX-PES or HAXPES), to distinguish the experiment from X-ray photoelectron spectroscopy performed at lower energies, has resulted in an increasing interest in photoelectron spectroscopy in many areas. The much increased mean free path at higher kinetic energies, in combination with the elemental selectivity of the core level spectroscopies in general has led to this fact. It is thus now possible to investigate the electronic structure of materials with a substantially enhanced bulk sensitivity. In this review we provide examples from our own research using HAXPES which to date has been performed mainly at the HIKE facility at the KMC-1 beamline at HZB, Berlin. The review exemplifies the new opportunities using HAXPES to address both bulk and interface electronic properties in systems relevant for applications in magnetic storage, energy related research, but also in purely curiosity driven problems

  3. Formic and acetic acid: Valence threshold photoelectron and photoionisation total ion yield studies

    Energy Technology Data Exchange (ETDEWEB)

    Siggel-King, Michele R.F., E-mail: michele.siggel-king@stfc.ac.uk [Cockcroft Institute, Daresbury Science and Innovation Campus, Daresbury, Warrington WA4 4AD (United Kingdom); Department of Physics, University of Liverpool, Liverpool L69 3BX,UK (United Kingdom); Yencha, Andrew J. [Department of Chemistry, State University of New York at Albany, Albany, NY 12222 (United States); King, George C. [Department of Physics and Astronomy and Photon Science Institute, Manchester University, Manchester M13 9PL (United Kingdom); Malins, Andrew E.R. [Cockcroft Institute, Daresbury Science and Innovation Campus, Daresbury, Warrington WA4 4AD (United Kingdom); Eypper, Marie [School of Chemistry, University of Southampton, Southampton SO17 1BJ (United Kingdom)

    2012-09-15

    Highlights: Black-Right-Pointing-Pointer High-resolution threshold photoelectron spectrum of formic acid. Black-Right-Pointing-Pointer High-resolution total photo-ion yield spectrum of formic acid. Black-Right-Pointing-Pointer High-resolution threshold photoelectron spectrum of acetic acid. Black-Right-Pointing-Pointer High-resolution total photo-ion yield spectrum of acetic acid. -- Abstract: The carboxylic acids (formic and acetic) have been studied using threshold photoelectron (TPE) and total photoion yield (TPIY) spectroscopies; simultaneously obtained spectra of formic acid (HCOOH) were recorded over the entire valence ionisation region from 11-21 eV at a resolution of {approx}12 meV. Higher resolution spectra ({approx}6 meV) were also obtained in the energy region of the lowest two cationic states. Analysis of the TPE spectrum in this energy range agreed very favorably with the best available conventional photoelectron (PE) spectrum of formic acid. Autoionising Rydberg structure was observed in the TPIY spectrum of formic acid and is attributed primarily to the presence of the npa Prime Leftwards-Arrow 8a Prime Rydberg series converging on to the 3{sup 2}A Prime ionic state of formic acid. Preliminary results, at a resolution of {approx}8 meV, were obtained for acetic acid (CH{sub 3}COOH) over the onset of the ionisation energy region. The TPE spectrum was found to be very similar to the best published photoelectron spectrum, but no Rydberg structure was observed in the TPIY spectrum.

  4. Two-color visible/vacuum ultraviolet photoelectron imaging dynamics of Br2.

    Science.gov (United States)

    Plenge, Jürgen; Nicolas, Christophe; Caster, Allison G; Ahmed, Musahid; Leone, Stephen R

    2006-10-07

    An experimental two-color photoionization dynamics study of laser-excited Br2 molecules is presented, combining pulsed visible laser excitation and tunable vacuum ultraviolet (VUV) synchrotron radiation with photoelectron imaging. The X 1Sigmag + -B 3Pi0+u transition in Br2 is excited at 527 nm corresponding predominantly to excitation of the v' = 28 vibrational level in the B 3Pi0+u state. Tunable VUV undulator radiation in the energy range of 8.40-10.15 eV is subsequently used to ionize the excited molecules to the X 2Pi32,12 state of the ion, and the ionic ground state is probed by photoelectron imaging. Similar experiments are performed using single-photon synchrotron ionization in the photon energy range of 10.75-12.50 eV without any laser excitation. Photoelectron kinetic energy distributions are extracted from the photoelectron images. In the case of two-color photoionization using resonant excitation of the intermediate B 3Pi0+u state, a broad distribution of photoelectron kinetic energies is observed, and in some cases even a bimodal distribution, which depends on the VUV photon energy. In contrast, for single-photon ionization, a single nearly Gaussian-shaped distribution is observed, which shifts to higher energy with photon energy. Simulated spectra based on Franck-Condon factors for the transitions Br2(X 1Sigmag+, v" = 0)-Br2 +(X 2Pi12,32, v+) and Br2(B 3Pi0+u, v' = 28)-Br2 +(X 2Pi12,32, v+) are generated. Comparison of these calculated spectra with the measured images suggests that the differences in the kinetic energy distributions for the two ionization processes reflect the different extensions of the vibrational wave functions in the v" = 0 electronic ground state (X 1Sigmag+) versus the electronically and vibrationally excited state (B 3Pi0+u, v' = 28).

  5. Characteristic evolutions in numerical relativity using six angular patches

    International Nuclear Information System (INIS)

    Reisswig, Christian; Bishop, Nigel T; Lai, Chi Wai; Thornburg, Jonathan; Szilagyi, Bela

    2007-01-01

    The characteristic approach to numerical relativity is a useful tool in evolving gravitational systems. In the past this has been implemented using two patches of stereographic angular coordinates. In other applications, a six-patch angular coordinate system has proved effective. Here we investigate the use of a six-patch system in characteristic numerical relativity, by comparing an existing two-patch implementation (using second-order finite differencing throughout) with a new six-patch implementation (using either second- or fourth-order finite differencing for the angular derivatives). We compare these different codes by monitoring the Einstein constraint equations, numerically evaluated independently from the evolution. We find that, compared to the (second-order) two-patch code at equivalent resolutions, the errors of the second-order six-patch code are smaller by a factor of about 2, and the errors of the fourth-order six-patch code are smaller by a factor of nearly 50

  6. Orbital Angular Momentum Multiplexing over Visible Light Communication Systems

    Science.gov (United States)

    Tripathi, Hardik Rameshchandra

    This thesis proposes and explores the possibility of using Orbital Angular Momentum multiplexing in Visible Light Communication system. Orbital Angular Momentum is mainly applied for laser and optical fiber transmissions, while Visible Light Communication is a technology using the light as a carrier for wireless communication. In this research, the study of the state of art and experiments showing some results on multiplexing based on Orbital Angular Momentum over Visible Light Communication system were done. After completion of the initial stage; research work and simulations were performed on spatial multiplexing over Li-Fi channel modeling. Simulation scenarios which allowed to evaluate the Signal-to-Noise Ratio, Received Power Distribution, Intensity and Illuminance were defined and developed.

  7. Nuclear level density variation with angular momentum induced shape transition

    International Nuclear Information System (INIS)

    Aggarwal, Mamta

    2016-01-01

    Variation of Nuclear level density (NLD) with the excitation energy and angular momentum in particular has been a topic of interest in the recent past and there have been continuous efforts in this direction on the theoretical and experimental fronts but a conclusive trend in the variation of nuclear level density parameter with angular momentum has not been achieved so far. A comprehensive investigation of N=68 isotones around the compound nucleus 119 Sb from neutron rich 112 Ru (Z=44) to neutron deficient 127 Pr (Z= 59) nuclei is presented to understand the angular momentum induced variations in inverse level density parameter and the possible influence of deformation and structural transitions on the variations on NLd

  8. Angular trapping of anisometric nano-objects in a fluid.

    Science.gov (United States)

    Celebrano, Michele; Rosman, Christina; Sönnichsen, Carsten; Krishnan, Madhavi

    2012-11-14

    We demonstrate the ability to trap, levitate, and orient single anisometric nanoscale objects with high angular precision in a fluid. An electrostatic fluidic trap confines a spherical object at a spatial location defined by the minimum of the electrostatic system free energy. For an anisometric object and a potential well lacking angular symmetry, the system free energy can further strongly depend on the object's orientation in the trap. Engineering the morphology of the trap thus enables precise spatial and angular confinement of a single levitating nano-object, and the process can be massively parallelized. Since the physics of the trap depends strongly on the surface charge of the object, the method is insensitive to the object's dielectric function. Furthermore, levitation of the assembled objects renders them amenable to individual manipulation using externally applied optical, electrical, or hydrodynamic fields, raising prospects for reconfigurable chip-based nano-object assemblies.

  9. ANGULAR LIGHT-SCATTERING STUDIES ON ISOLATED MITOCHONDRIA

    Science.gov (United States)

    Gotterer, Gerald S.; Thompson, Thomas E.; Lehninger, Albert L.

    1961-01-01

    Angular light-scattering studies have been carried out on suspensions of isolated rat liver mitochondria. The angular scatter pattern has a large forward component, typical of large particles. Changes in dissymmetry and in the intensity of light scattered at 90° have been correlated with changes in optical density during the course of mitochondrial swelling and contraction. Such changes can be measured at mitochondrial concentrations much below those required for optical density measurements. Changes in mitochondrial geometry caused by factors "leaking" from mitochondria, not detectable by optical density measurements, have been demonstrated by measuring changes in dissymmetry. Angular light-scattering measurements therefore offer the advantages of increased sensitivity and of added indices of changes in mitochondrial conformation. PMID:19866589

  10. Angular momentum dependence of the nuclear level density parameter

    Directory of Open Access Journals (Sweden)

    Gohil M.

    2014-03-01

    Full Text Available Neutron evaporation spectra alongwith γ-multiplicity has been measured from the 185Re* compound nucleus at the excitation energies ~27 and 37 MeV. Statistical model analysis of the experimental data has been carried out to extract the value of the inverse level density parameter k at different angular momentum regions (J corresponding to different γ-multiplicity. It is observed that, for the present system the value of k remains almost constant for different J. The present results on the angular momentum dependence of the nuclear level density (NLD parameter ã (=A/k, for nuclei with A ~180 is quite different from our earlier measurements in case of light and medium mass systems. The present analysis provides useful information to understand the angular momentum dependence of NLD at different nuclear mass regions.

  11. Angular Magnetoresistance of Nanowires with Alternating Cobalt and Nickel Segments

    KAUST Repository

    Mohammed, Hanan

    2017-06-22

    Magnetization reversal in segmented Co/Ni nanowires with varying number of segments was studied using angular Magnetoresistance (MR) measurements on isolated nanowires. The MR measurements offer an insight into the pinning of domain walls within the nanowires. Angular MR measurements were performed on nanowires with two and multiple segments by varying the angle between the applied magnetic field and nanowire (−90° ≤θ≤90°). The angular MR measurements reveal that at lower values of θ the switching fields are nearly identical for the multisegmented and two-segmented nanowires, whereas at higher values of θ, a decrease in the switching field is observed in the case of two segmented nanowires. The two segmented nanowires generally exhibit a single domain wall pinning event, whereas an increased number of pinning events are characteristic of the multisegmented nanowires at higher values of θ. In-situ magnetic force microscopy substantiates reversal by domain wall nucleation and propagation in multisegmented nanowires.

  12. Spin and orbital angular momentum distribution functions of the nucleon

    Science.gov (United States)

    Wakamatsu, M.; Watabe, T.

    2000-09-01

    A theoretical prediction is given for the spin and orbital angular momentum distribution functions of the nucleon within the framework of an effective quark model of QCD, i.e., the chiral quark soliton model. An outstanding feature of the model is that it predicts a fairly small quark spin fraction of the nucleon ΔΣ~=0.35, which in turn dictates that the remaining 65% of the nucleon spin is carried by the orbital angular momentum of quarks and antiquarks at the model energy scale of Q2~=0.3 GeV2. This large orbital angular momentum necessarily affects the scenario of scale dependence of the nucleon spin contents in a drastic way.

  13. Angular Momentum Transport in Turbulent Flow between Independently Rotating Cylinders

    International Nuclear Information System (INIS)

    Paoletti, M. S.; Lathrop, D. P.

    2011-01-01

    We present measurements of the angular momentum flux (torque) in Taylor-Couette flow of water between independently rotating cylinders for all regions of the (Ω 1 , Ω 2 ) parameter space at high Reynolds numbers, where Ω 1 (Ω 2 ) is the inner (outer) cylinder angular velocity. We find that the Rossby number Ro=(Ω 1 -Ω 2 )/Ω 2 fully determines the state and torque G as compared to G(Ro=∞)≡G ∞ . The ratio G/G ∞ is a linear function of Ro -1 in four sections of the parameter space. For flows with radially increasing angular momentum, our measured torques greatly exceed those of previous experiments [Ji et al., Nature (London), 444, 343 (2006)], but agree with the analysis of Richard and Zahn [Astron. Astrophys. 347, 734 (1999)].

  14. Microbeam High Angular Resolution Diffraction Applied to Optoelectronic Devices

    International Nuclear Information System (INIS)

    Kazimirov, A.; Bilderback, D. H.; Sirenko, A. A.; Cai, Z.-H.; Lai, B.

    2007-01-01

    Collimating perfect crystal optics in a combination with the X-ray focusing optics has been applied to perform high angular resolution microbeam diffraction and scattering experiments on micron-size optoelectronic devices produced by modern semiconductor technology. At CHESS, we used capillary optics and perfect Si/Ge crystal(s) arrangement to perform X-ray standing waves, high angular-resolution diffraction and high resolution reciprocal space mapping analysis. At the APS, 2ID-D microscope beamline, we employed a phase zone plate producing a beam with the size of 240 nm in the horizontal plane and 350 nm in the vertical (diffraction) plane and a perfect Si (004) analyzer crystal to perform diffraction analysis of selectively grown InGaAsP and InGaAlAs-based waveguides with arc sec angular resolution

  15. Angular momentum non-conserving symmetries in bosonic models

    Energy Technology Data Exchange (ETDEWEB)

    Fortunato, L [ECT, Strada delle Tabarelle 286, I-38123 Villazzano (Trento) (Italy); De Graaf, W A, E-mail: fortunat@pd.infn.it [Dip. Matematica, Universita di Trento, via Sommarive 24, I-38123 Povo, Trento (Italy)

    2011-04-08

    The Levi-Malcev decomposition is applied to bosonic models of quantum mechanics based on unitary Lie algebras u(2), u(2)+u(2), u(3) and u(4) to clearly disentangle semisimple subalgebras. The theory of weighted Dynkin diagrams is then applied to identify conjugacy classes of relevant A{sub 1} subalgebras allowing us to introduce a complete classification of new angular momentum non conserving (AMNC) dynamical symmetries. The tensor analysis of the whole algebra based on the new 'angular momentum' operators reveals unexpected spinors to occur in purely bosonic models. The new chains of subalgebra can be invoked to set up ANMC bases for diagonalization.

  16. Angular momentum non-conserving symmetries in bosonic models

    Science.gov (United States)

    Fortunato, L.; de Graaf, W. A.

    2011-04-01

    The Levi-Malcev decomposition is applied to bosonic models of quantum mechanics based on unitary Lie algebras u(2), u(2)⊕u(2), u(3) and u(4) to clearly disentangle semisimple subalgebras. The theory of weighted Dynkin diagrams is then applied to identify conjugacy classes of relevant A1 subalgebras allowing us to introduce a complete classification of new angular momentum non conserving (AMNC) dynamical symmetries. The tensor analysis of the whole algebra based on the new 'angular momentum' operators reveals unexpected spinors to occur in purely bosonic models. The new chains of subalgebra can be invoked to set up ANMC bases for diagonalization.

  17. Spatial distribution of angular momentum inside the nucleon

    Science.gov (United States)

    Lorcé, Cédric; Mantovani, Luca; Pasquini, Barbara

    2018-01-01

    We discuss in detail the spatial distribution of angular momentum inside the nucleon. We show that the discrepancies between different definitions originate from terms that integrate to zero. Even though these terms can safely be dropped at the integrated level, they have to be taken into account when discussing distributions. Using the scalar diquark model, we illustrate our results and, for the first time, check explicitly that the equivalence between kinetic and canonical orbital angular momentum persists at the level of distributions, as expected in a system without gauge degrees of freedom.

  18. Alignment of angular velocity sensors for a vestibular prosthesis

    Directory of Open Access Journals (Sweden)

    DiGiovanna Jack

    2012-02-01

    Full Text Available Abstract Vestibular prosthetics transmit angular velocities to the nervous system via electrical stimulation. Head-fixed gyroscopes measure angular motion, but the gyroscope coordinate system will not be coincident with the sensory organs the prosthetic replaces. Here we show a simple calibration method to align gyroscope measurements with the anatomical coordinate system. We benchmarked the method with simulated movements and obtain proof-of-concept with one healthy subject. The method was robust to misalignment, required little data, and minimal processing.

  19. On angular distribution of nucleus fission fragments by fast neutrons

    International Nuclear Information System (INIS)

    Barabanov, A.L.; Grechukhin, D.P.

    1987-01-01

    Evaluation of amplitudes of quadrupole and hexadecapole components of angular distribution of nucleus fission fragments by neutrons with the energies E n < or approx. 6 MeV is conducted. Stability of this amplitude to permeability optical coefficient variations for neutrons is revealed. It is shown, that the ratio of these amplitudes as well as the character of their dependence on the target nucleus orientation degree are sensitive to the type of fission probability distribution along K projection if fissile nucleus J spin to the fragment scattering axis. This sensitivity may be used for fragment angular distribution anisotropy formation statistical model verification

  20. Radio source orientation and the angular diameter-redshift relation

    Science.gov (United States)

    Onuora, L. I.

    1991-08-01

    The effect of a nonrandom source orientation on the angular diameter-redshift relation was considered for the 3CR sample of Laing et al., based on the 'unified' scheme of Barthel. For an inhomogeneous sample of objects displaying milliarcsecond scale structure, it was found that there was no evidence for a systematic variation for orientation angle with redshift. However, if it was assumed that quasars are closer to the line of sight than powerful extended radio galaxies, then the observed angular size-redshift relation could be interpreted in terms of source orientation, rather than linear size evolution.

  1. Four Cases of Angular Cheilitis in Orthodontic Patients

    Directory of Open Access Journals (Sweden)

    P Kafaie

    2006-07-01

    Full Text Available Contact dermatitis is an inflammatory reaction of the skin and mucosa to either external or internal factors. It can be divided to two forms of irritant contact dermatitis and allergic contact dermatitis. Nickel is one of the most common materials that causes allergic contact dermatitis and is widely used in orthodontic appliances. The inflammatory reaction to this metal in orthodontics is usually stomatitis and angular cheilitis is very rare. We report 4 cases of angular cheilitis in orthodontic patients and discuss about their causes and treatments.

  2. An X-ray photoelectron spectroscopy study of uranyl-chitosan interaction

    Directory of Open Access Journals (Sweden)

    Veleshko Alexander N.

    2008-01-01

    Full Text Available An X-ray photoelectron spectroscopy study of uranium sorption by spherically-granulated chitosan in sulphate solutions, as well as the study of the nature of the U(VI - chitosan interaction was carried out in this work. The X-ray photoelectron spectroscopy analysis showed that the uranyl - chitosan interaction results in the formation of complexes with aminogroup nitrogen, and possibly chitin ring oxygens and free hydroxyl groups in the equatorial plane. Under the UHV in the spectrometer chamber, the uranyl-amin and uranyl-hyroxide bonds were shown to break and tetravalent uranium compounds were shown to form on the sample surface. Hydroxyl groups were shown to evaporate. The calculated DG0 = -1,3 kJ/mol can be an evidence of several concurrent processes, some of which require energy, as well as of the formation of a surface chemical compound.

  3. A microcomputer-controlled modulation technique for the detection of transient species in UV photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Lonkhuyzen, H. van; Muller, H.G.; Lange, C.A. de

    1980-01-01

    A microcomputer-controlled modulation method is described to measure UV photoelectron spectra of transient species generated in a microwave discharge. Spectra at low and high microwave power levels are simultaneously recorded and afterwards linearly combined in order to remove parent compound signals. The method is applied to discharged oxygen where the transition O 2 + ( 2 PHIsub(u)) 2 ( 1 Δsub(g)) becomes visible without interference from the parent molecule O 2 ( 3 Σsub(g) - ), and to discharged sulphur dioxide where SO( 3 Σ - ) and S( 3 P) photoelectron spectra are obtained free from SO 2 bands. Finally the build-up of transient bands as a function of time is recorded. (orig.)

  4. Investigation of hafnium silicide nanostructures on a Si(100) surface by means of photoelectron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Fluechter, C.R.; Weier, D. [Experimentelle Physik 1 - Universitaet Dortmund, (Germany); DELTA - Universitaet Dortmund, Maria-Goeppert-Mayer-Str. 2, D 44227 (Germany); Siervo, A. de; Landers, R. [Laboratorio Nacional de Luz Sincrotron, C.P. 6192, (Brazil); Schuermann, M.; Beimborn, A.; Schoenbohm, F.; Dreiner, S.; Westphal, C. [Experimentelle Physik 1 - Universitaet Dortmund, (Germany); Carazzolle, M.F.; Kleiman, G.G. [Inst. de Fisica - Universidade Estadual de Campinas, (Brazil)

    2007-07-01

    Ultrathin films of hafnium were deposited on a silicon sample and annealed at 750 C forming rectangular shaped hafnium silicide islands on the surface. This silicidation process causes the thermal instability of HfO{sub 2} films on silicon substrates. The latter system is under investigation in the field of high-k dielectrics to replace the system SiO{sub 2}/Si(100) in MOSFET devices. We investigated the structure of the HfSi{sub 2} island for different initial film thicknesses of hafnium by means of atomic force microscopy, photoelectron spectroscopy and photoelectron diffraction. Synchrotron light in the soft X-ray regime (h{nu}=180 eV) was used for excitation. The resulting diffraction patterns were compared to calculated patterns of model structures by an R-factor analysis. As a result, we propose a modified zirconium silicide model to describe the structure of the system.

  5. Probing molecular orientations in thin films by x-ray photoelectron spectroscopy

    Science.gov (United States)

    Li, Y.; Li, P.; Lu, Z.-H.

    2018-03-01

    A great number of functional organic molecules in active thin-film layers of optoelectronic devices have highly asymmetric structures, such as plate-like, rod-like, etc. This makes molecular orientation an important aspect in thin-films as it can significantly affect both the optical and electrical performance of optoelectronic devices. With a combination of in-situ ultra violet photoelectron spectroscopy (UPS) and x-ray photoelectron spectroscopy (XPS) investigations for organic molecules having a broad range of structural properties, we discovered a rigid connection of core levels and frontier highest occupied molecular orbital levels at organic interfaces. This finding opens up opportunities of using X-ray photoemission spectroscopy as an alternative tool to UPS for providing an easy and unambiguous data interpretation in probing molecular orientations.

  6. Probing molecular orientations in thin films by x-ray photoelectron spectroscopy

    Directory of Open Access Journals (Sweden)

    Y. Li

    2018-03-01

    Full Text Available A great number of functional organic molecules in active thin-film layers of optoelectronic devices have highly asymmetric structures, such as plate-like, rod-like, etc. This makes molecular orientation an important aspect in thin-films as it can significantly affect both the optical and electrical performance of optoelectronic devices. With a combination of in-situ ultra violet photoelectron spectroscopy (UPS and x-ray photoelectron spectroscopy (XPS investigations for organic molecules having a broad range of structural properties, we discovered a rigid connection of core levels and frontier highest occupied molecular orbital levels at organic interfaces. This finding opens up opportunities of using X-ray photoemission spectroscopy as an alternative tool to UPS for providing an easy and unambiguous data interpretation in probing molecular orientations.

  7. Photoelectron and electron momentum spectroscopy of tetrahydrofuran from a molecular dynamical perspective.

    Science.gov (United States)

    Shojaei, S H Reza; Morini, Filippo; Deleuze, Michael S

    2013-03-07

    The results of experimental studies of the valence electronic structure of tetrahydrofuran employing He I photoelectron spectroscopy as well as Electron Momentum Spectroscopy (EMS) have been reinterpreted on the basis of Molecular Dynamical simulations employing the classical MM3 force field and large-scale quantum mechanical simulations employing Born-Oppenheimer Molecular Dynamics in conjunction with the dispersion corrected ωB97XD exchange-correlation functional. Analysis of the produced atomic trajectories demonstrates the importance of thermal deviations from the lowest energy path for pseudorotation, in the form of considerable variations of the ring-puckering amplitude. These deviations are found to have a significant influence on several outer-valence electron momentum distributions, as well as on the He I photoelectron spectrum.

  8. Strong-field photoelectron holography of atoms by bicircular two-color laser pulses

    Science.gov (United States)

    Li, Min; Jiang, Wei-Chao; Xie, Hui; Luo, Siqiang; Zhou, Yueming; Lu, Peixiang

    2018-02-01

    We study photoelectron holography in strong bicircular two-color laser fields by solving the time-dependent Schrödinger equation (TDSE) and a semiclassical rescattering model with implementing interference effect. The holographic patterns observed in the TDSE are well recaptured by the semiclassical rescattering model. Four types of photoelectron holographic interferences between the forward scattered and nonscattered trajectories are predicted by the semiclassical rescattering model in the bicircular two-color laser field. We find that those holographic patterns are spatially separated from each other in the electron momentum distribution. We further show that the dependence of the initial transverse momentum at the tunnel exit on the ionization time for the rescattering electron is recorded by the holographic patterns.

  9. Photo-electronic current transport in back-gated graphene transistor

    Science.gov (United States)

    Srivastava, Ashok; Chen, Xinlu; Pradhan, Aswini K.

    2017-04-01

    In this work, we have studied photo-electronic current transport in a back-gated graphene field-effect transistor. Under the light illumination, band bending at the metal/graphene interface develops a built-in potential which generates photonic current at varying back-gate biases. A typical MOSFET type back-gated transistor structure uses a monolayer graphene as the channel layer formed over the silicon dioxide/silicon substrate. It is shown that the photo-electronic current consists of current contributions from photovoltaic, photo-thermoelectric and photo-bolometric effects. A maximum external responsivity close to 0.0009A/W is achieved at 30μW laser power source and 633nm wavelength.

  10. X-ray photoelectron spectroscopy of the uranium/oxygen system

    International Nuclear Information System (INIS)

    Allen, G.C.; Holmes, N.R.

    1986-10-01

    Other authors have presented evidence to show that the oxidised surface layer which forms on UO 2 at 25 0 C is amorphous UO 3 . In the present study X-ray photoelectron spectroscopy, infra-red spectroscopy and X-ray diffraction have been used to characterise the higher oxides α-UO 3 , β-UO 3 , γ-UO 3 and δ-UO 3 . While the infra-red and X-ray diffraction results may be used to characterise each oxide the X-ray photoelectron spectra for each phase are very similar. During reduction of the oxide surface in the spectrometer changes in the spectra were observed which were shown to be associated with particular oxidation states of the metal rather than different uranium atom coordination sites within the oxide. A close structural relationship is demonstrated between these oxides and the product at the surface of air-oxidised UO 2 fuel. (author)

  11. Photoelectron and UV absorption spectroscopy for determination of electronic configurations of negative molecular ions: Chlorophenols

    International Nuclear Information System (INIS)

    Tseplin, E.E.; Tseplina, S.N.; Tuimedov, G.M.; Khvostenko, O.G.

    2009-01-01

    The photoelectron and UV absorption spectra of p-, m-, and o-chlorophenols in the gas phase have been obtained. On the basis of DFT B3LYP/6-311++G(d, p) calculations, the photoelectron bands have been assigned to occupied molecular orbitals. From the TDDFT B3LYP/6-311++G(d, p) calculation results, the UV absorption bands have been assigned to excited singlet states of the molecules under investigation. For each excited state a dominant transition was found. It has been shown that the energies of these singlet transitions correlate with the energy differences between the ground-state molecular orbitals participating in them. Using the UV spectra interpretation, the electronic states of molecular anions detected earlier for the same compounds by means of the resonant electron capture mass-spectrometry have been determined.

  12. Experimental investigations of the lunar photoelectron environment and related dust dynamics

    Science.gov (United States)

    Dove, Adrienne Rathert

    Airless bodies in space are exposed to a variety of charging environments in which a balance of currents due to plasma processes determines the surface charge. In the inner solar system, photoelectron emission is the dominant charging process on sunlit surfaces due to the intense solar UV radiation. This results in a positive surface potential with a photoelectron sheath above the surface. 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 with the photoelectron and plasma sheaths, may explain the occurrence of dust lofting, levitation and transport above the lunar surface and on other airless bodies. This dust has been recognized as a potentially great hazard to future exploration of dusty planetary surfaces, due to its abrasive and adhesive nature. An initial investigation explores the mechanisms that control adhesion of dust grains to insulating and conducting surfaces. Unfortunately, there is little known about the mechanisms of adhesion on widely varying surface types, but van der Waals and electrostatic forces are the dominant forces that are taken into consideration in this study, which measures the adhesive forces between ≤ 25 μm JSC-1 lunar simulant grains and various surfaces vacuum using a centrifugal force detachment method. UV irradiation effects on surface adhesion were also examined. In order to better understand the plasma processes at work on sunlit surfaces, we have performed laboratory experiments to study the physics of photoelectron sheaths above both conducting and insulating surfaces in vacuum. The first set of experiments determines the characteristics of photoelectron sheaths generated over a conducting Zr surface that is large in comparison to the Debye length of the sheath. These characteristics are derived from cylindrical Langmuir probe measurements, and are compared

  13. Time-Resolved Photoelectron Spectroscopy of Oxidation on the Ti(0001) Surface

    Energy Technology Data Exchange (ETDEWEB)

    Mizuno, Yoshiyuki

    2003-03-28

    High-resolution photoelectron spectroscopy using synchrotron radiation was applied for monitoring in real time the oxidation kinetics on the Ti(0001) surface at 405 C with dry O{sub 2} gas. The time evolution of O 1s photoelectron intensity showed a linear uptake curve up to {approx}90 L followed by a sudden saturation up to {approx}160 L and then a restart of the linear increase, indicating that O{sub 2} adsorption obeys a zero-order reaction scheme before and after the saturation. Corresponding to the first linear uptake and saturation, the surface core level shift (SCLS) component of Ti 2p decreased predominantly and disappeared completely, and appeared again after the saturation and remained persistently during TiO{sub 2} growth. Thus the zero-order reaction of O{sub 2} adsorption on the Ti(0001) surface at 405 C is concerned with the metallic Ti layer on the outermost surface.

  14. Direct Visualization of Valence Electron Motion Using Strong-Field Photoelectron Holography

    Science.gov (United States)

    He, Mingrui; Li, Yang; Zhou, Yueming; Li, Min; Cao, Wei; Lu, Peixiang

    2018-03-01

    Watching the valence electron move in molecules on its intrinsic timescale has been one of the central goals of attosecond science and it requires measurements with subatomic spatial and attosecond temporal resolutions. The time-resolved photoelectron holography in strong-field tunneling ionization holds the promise to access this realm. However, it remains to be a challenging task hitherto. Here we reveal how the information of valence electron motion is encoded in the hologram of the photoelectron momentum distribution (PEMD) and develop a novel approach of retrieval. As a demonstration, applying it to the PEMDs obtained by solving the time-dependent Schrödinger equation for the prototypical molecule H2+ , the attosecond charge migration is directly visualized with picometer spatial and attosecond temporal resolutions. Our method represents a general approach for monitoring attosecond charge migration in more complex polyatomic and biological molecules, which is one of the central tasks in the newly emerging attosecond chemistry.

  15. Many-body effect in the partial singles N2,3 photoelectron spectroscopy spectrum of atomic Cd

    International Nuclear Information System (INIS)

    Ohno, Masahide

    2008-01-01

    We can extract out the photoelectron kinetic energy (KE) dependent imaginary part of the core-hole self-energy by employing Auger-photoelectron coincidence spectroscopy (APECS). The variation with photoelectron KE in the Auger electron spectroscopy (AES) spectral peak intensity of a selected decay channel measured in coincidence with photoelectrons of a selected KE is the partial singles (non-coincidence) photoelectron spectroscopy (PES) spectrum, i.e., the product of the singles PES one and the branching ratio of the partial Auger decay width of a selected decay channel to the imaginary part of the core-hole self-energy. When a decay channel the partial Auger decay width of which is photoelectron KE independent is selected, we can extract out spectroscopically the imaginary part of the core-hole self-energy because the variation with photoelectron KE in the relative spectral intensity of the partial singles PES spectrum to the singles one is that in the branching ratio of the partial Auger decay width of a selected decay channel. As an example we discussed the N 2,3 -hole self-energy of atomic Cd

  16. Enhanced quantum efficiency of photoelectron emission, through surface textured metal electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Alexander, Anna; Bandaru, Prabhakar R., E-mail: pbandaru@ucsd.edu [Program in Materials Science, Department of Mechanical Engineering, University of California, San Diego, La Jolla, California, 92130 (United States); Moody, Nathan A. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

    2016-03-15

    It is predicted that the quantum efficiency (QE) of photoelectron emission from metals may be enhanced, possibly by an order of magnitude, through optimized surface texture. Through extensive computational simulations, it is shown that the absorption enhancement in select surface groove geometries may be a dominant contributor to enhanced QE and corresponds to localized Fabry–Perot resonances. The inadequacy of extant analytical models in predicting the QE increase, and suggestions for further improvement, are discussed.

  17. Characterization of alkanethiol/ZnO structures by X-ray photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Ogata, K.; Hama, T.; Hama, K.; Koike, K.; Sasa, S.; Inoue, M.; Yano, M.

    2005-01-01

    1-Propanethiol (CH 3 CH 2 CH 2 SH) was connected with O-polar zinc oxide (ZnO) surfaces toward biofunctional devices. X-ray photoelectron spectroscopy (XPS) measurement revealed that the S-O bonds were formed between 1-propanethiol and ZnO layers. Although the surface coverage of the molecule is less than a few percent, 1-propanethiol/ZnO structures were stable even at thermal treatment of 400 deg. C

  18. Effects of the Coulomb potential in interference patterns of strong-field holography with photoelectrons

    Science.gov (United States)

    Shvetsov-Shilovski, N. I.; Lein, M.

    2018-01-01

    Using the semiclassical two-step model for strong-field ionization we investigate the interference structures emerging in strong-field photoelectron holography, taking into account the Coulomb potential of the atomic core. For every kind of the interference pattern predicted by the three-step model, we calculate the corresponding structure in the presence of the Coulomb field, showing that the Coulomb potential modifies the interference patterns significantly.

  19. GaN quantum dot polarity determination by X-ray photoelectron diffraction

    Czech Academy of Sciences Publication Activity Database

    Romanyuk, Olexandr; Bartoš, Igor; Brault, J.; De Mierry, P.; Paskova, T.; Jiříček, Petr

    2016-01-01

    Roč. 389, Dec (2016), s. 1156-1160 ISSN 0169-4332 R&D Projects: GA ČR GA15-01687S; GA MŠk LM2015088 Institutional support: RVO:68378271 Keywords : GaN * semipolar GaN * quantum dots * X-ray photoelectron diffraction * surface polarity Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.387, year: 2016

  20. Transition absorption as a mechanism of surface photoelectron emission from metals

    DEFF Research Database (Denmark)

    Zhukovsky, Sergei; Protsenko, Igor E.; Ikhsanov, Renat Sh

    2015-01-01

    Transition absorption of a photon by an electron passingthrough a boundary between two media with different permit-tivities is described both classically and quantum mechani-cally. Transition absorption is shown to make a substantialcontribution to photoelectron emission at a metal....../semicon-ductor interface in nanoplasmonic systems, and is put forth asa possible microscopic mechanism of the surface photoelec-tric effect in photodetectors and solar cells containing plas-monic nanoparticles....

  1. Modeling and parameterization of photoelectrons emitted in condensed matter by linearly polarized synchrotron radiation

    Science.gov (United States)

    Jablonski, A.

    2018-01-01

    Growing availability of synchrotron facilities stimulates an interest in quantitative applications of hard X-ray photoemission spectroscopy (HAXPES) using linearly polarized radiation. An advantage of this approach is the possibility of continuous variation of radiation energy that makes it possible to control the sampling depth for a measurement. Quantitative applications are based on accurate and reliable theory relating the measured spectral features to needed characteristics of the surface region of solids. A major complication in the case of polarized radiation is an involved structure of the photoemission cross-section for hard X-rays. In the present work, details of the relevant formalism are described and algorithms implementing this formalism for different experimental configurations are proposed. The photoelectron signal intensity may be considerably affected by variation in the positioning of the polarization vector with respect to the surface plane. This information is critical for any quantitative application of HAXPES by polarized X-rays. Different quantitative applications based on photoelectrons with energies up to 10 keV are considered here: (i) determination of surface composition, (ii) estimation of sampling depth, and (iii) measurements of an overlayer thickness. Parameters facilitating these applications (mean escape depths, information depths, effective attenuation lengths) were calculated for a number of photoelectron lines in four elemental solids (Si, Cu, Ag and Au) in different experimental configurations and locations of the polarization vector. One of the considered configurations, with polarization vector located in a plane perpendicular to the surface, was recommended for quantitative applications of HAXPES. In this configurations, it was found that the considered parameters vary weakly in the range of photoelectron emission angles from normal emission to about 50° with respect to the surface normal. The averaged values of the mean

  2. Measurement of actinides in environmental samples by Photo-Electron Rejecting Alpha Liquid Scintillation

    Energy Technology Data Exchange (ETDEWEB)

    Cadieux, J.R. [Westinghouse Savannah River Co., Aiken, SC (United States); Clark, S. [Savannah River Ecology Lab., Univ. of Georgia (United States); Fjeld, R.A.; Reboul, S.; Sowder, A. [Clemson Univ., SC (United States). Dept. of Environmental Systems Engineering

    1994-05-01

    This work describes the adaptation of extractive scintillation with a Photo-Electron Rejecting Alpha Liquid Scintillation (PERALS) (ORDELA, Inc.) spectrometer to the analysis of actinides in environmental samples from the Savannah River Site (SRS). Environmental quality assurance standards and actual water samples were treated by one of two methods; either a two step direct extraction, or for more complex samples, pretreatment by an extraction chromatographic separation prior to measurement of the alpha activity by PERALS.

  3. Photoelectron photoion coincidence imaging of ultrafast control in multichannel molecular dynamics.

    Science.gov (United States)

    Lehmann, C Stefan; Ram, N Bhargava; Irimia, Daniel; Janssen, Maurice H M

    2011-01-01

    The control of multichannel ionic fragmentation dynamics in CF3I is studied by femtosecond pulse shaping and velocity map photoelectron photoion coincidence imaging. When CF3I is photoexcited with femtosecond laser pulses around 540 nm there are two major ions observed in the time-of-flight mass spectrum, the parent CF3I+ ion and the CF3+ fragment ion. In this first study we focussed on the influence of LCD-shaped laser pulses on the molecular dynamics. The three-dimensional recoil distribution of electrons and ions were imaged in coincidence using a single time-of-flight delay line detector. By fast switching of the voltages on the various velocity map ion lenses after detection of the electron, both the electron and the coincident ion are measured with the same imaging detector. These results demonstrate that a significant simplification of a photoelectron-photoion coincidence imaging apparatus is in principle possible using switched lens voltages. It is observed that shaped laser fields like chirped pulses, double pulses, and multiple pulses can enhance the CF3+CF3I+ ratio by up to 100%. The total energetics of the dynamics is revealed by analysis of the coincident photoelectron spectra and the kinetic energy of the CF3+ and I fragments. Both the parent CF3I+ and the CF3+ fragment result from a five-photon excitation process. The fragments are formed with very low kinetic energy. The photoelectron spectra and CF3+/CF3I+ ratio vary with the center wavelength of the shaped laser pulses. An optimal enhancement of the CF3+/CF3I+ ratio by about 60% is observed for the double pulse excitation when the pulses are spaced 60 fs apart. We propose that the control mechanism is determined by dynamics on neutral excited states and we discuss the results in relation to the location of electronically excited (Rydberg) states of CF3I.

  4. Gas phase anion photoelectron spectroscopy and theoretical investigation of gold acetylide species

    Science.gov (United States)

    Wang, Peng; Zhang, Wenjing; Xu, Xi-Ling; Yuan, Jinyun; Xu, Hong-Guang; Zheng, Weijun

    2017-05-01

    We conducted gas phase anion photoelectron spectroscopy and density functional theory studies on a number of gold acetylide species, such as AuC2H, AuC2Au, and Au2C2H. Based on the photoelectron spectra, the electron affinities of AuC2H, AuC2Au, and Au2C2H are measured to be 1.54(±0.04), 1.60(±0.08), and 4.23(±0.08) eV, respectively. The highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gaps of AuC2H and AuC2Au are measured to be about 2.62 and 2.48 eV, respectively. It is interesting that photoelectron spectra of AuC2H- and AuC2Au- display similar spectral features. The comparison of experimental and theoretical results confirms that the ground-state structures of AuC2H-, AuC2Au-, and their neutrals are all linear with Au—C≡C—H and Au—C≡C—Au configurations. The similar geometric structures, spectral features, HOMO-LUMO gaps, and chemical bonding between AuC2H-/0 and AuC2Au-/0 demonstrate that Au atom behaves like H atom in these species. The photoelectron spectrum of Au2C2H- shows that Au2C2H has a high electron affinity of 4.23(±0.08) eV, indicating Au2C2H is a superhalogen. Further, we found an unusual similarity between the terminal Au atom of Au2C2H- and the iodine atom of IAuC2H-.

  5. Genetic characterization of angular leaf spot resistance in selected ...

    African Journals Online (AJOL)

    Mr Tryphone

    2015-10-28

    Oct 28, 2015 ... Angular leaf spot disease (ALS) caused by Pseudocercospora griseola is one of the most important bean diseases in Tanzania. The bean landraces Beti-10, Nanka, Nanavala and Nkanamna used in this study have been identified as resistant to ALS but the nature of inheritance and mechanisms of.

  6. Incorporation of resistance to angular leaf spot and bean common ...

    African Journals Online (AJOL)

    Angular leaf spot (ALS) caused by the fungus Pseudocercospora griseola and Bean common mosaic and necrosis virus (BCMV/BCMNV) are important diseases of common bean in Tanzania that can cause severe yield reduction when uncontrolled. This study was conducted to incorporate resistant genes for ALS and ...

  7. Incorporation of resistance to angular leaf spot and bean common ...

    African Journals Online (AJOL)

    Luseko

    2013-07-03

    Jul 3, 2013 ... Angular leaf spot (ALS) caused by the fungus Pseudocercospora griseola and Bean common mosaic and necrosis virus (BCMV/BCMNV) are important diseases of common bean in Tanzania that can cause severe yield reduction when uncontrolled. This study was conducted to incorporate resistant genes ...

  8. Angular dispersion of protons transmitted through thin gold films

    International Nuclear Information System (INIS)

    Archubi, C.; Eckardt, J.C.; Lantschner, G.H.; Lovey, F.; Arista, N.R.; Denton, C.; Parra, C.; Valdes, J.; Zappa, F.

    2004-01-01

    The angular distributions of protons travelling through thin polycrystalline gold targets (∝15 nm) with incident energies in the range of 4-10 keV have been measured. The results confirm previous experiments at higher energies showing deviations from theoretical predictions based on the standard multiple scattering theory. In order to prove that the effect of crystal structure is one of the main causes of these deviations we have performed numerical simulations. To simulate the polycrystalline structure in a realistic way, we have made an analysis of the target by means of transmission electron microscopy (TEM) techniques. Including these characteristics in the simulation, together with the effect of vibrations and crystal disorder we analyzed the corresponding angular distribution. To evaluate the role of channeling, we also measured angular distributions of protons in a left angle 100 right angle gold foil and made the corresponding numerical simulations. The results show the critical influence of the target structure in the angular spectra of transmitted ions. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  9. Numerical simulation of side heating for controlling angular ...

    Indian Academy of Sciences (India)

    However, it induces various types of distortions like angular, transverse, longitudinal, etc. Distor- tions induced ... strains and residual stress owing to the mismatch of thermal expansions in the weld and sur- rounding ... approaches, on the other hand, aim to minimize the residual stress during the welding process for given ...

  10. The phenomenon of nucleon emission at high angular momentum ...

    Indian Academy of Sciences (India)

    Since the drop in the separation energy is closely associated with the structural changes in the rotating nuclei, relative increase in neutron emission probability around certain values of angular momentum may be construed as evidence for the shape transition. A similar effect is predicted for 168Yb around ≈ 55ħ. We also ...

  11. Classical Angular Momentum of Light: A Paradox and its Resolution

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 8; Issue 10. Classical Angular Momentum of Light: A Paradox and its Resolution. K Vijay Kumar N Kumar. Classroom Volume 8 Issue 10 October 2003 pp 69-75. Fulltext. Click here to view fulltext PDF. Permanent link:

  12. Correlated angular distributions in τ+τ- semileptonic decays

    International Nuclear Information System (INIS)

    Dova, M.T.; Epele, L.N.; Fanchiotti, H.; Garcia Canal, C.A.; Lacentre, P.E.

    1995-01-01

    The spin correlated angular distribution for τ - τ + pairs at energies of the Z 0 resonance, both decaying semi-leptonically up to 3 hadrons in each final state, was derived assuming general vector and axial vector couplings. The use of these distributions to test the V - A structure of the τ-W-ν τ vertex at LEP energies is analized. (orig.)

  13. Numerical simulation of side heating for controlling angular ...

    Indian Academy of Sciences (India)

    In the present study, a 3-D coupled transient thermal analysis model with auxiliary side heating (parallel heating) is developed to control angular distortion. During analysis, parallel heating flames are placed at several locations from weld line in cross direction. A user defined subroutine is used to apply transient heat source ...

  14. Equal channel angular pressing of pure aluminium—an analysis

    Indian Academy of Sciences (India)

    Equal channel angular pressing (ECAP) is a novel technique for producing ultra fine grain structures in submicron level by introducing a large amount of shear strain into the materials without changing the billet shape or dimensions. This process is well suited for aluminium alloys and is capable of producing ultra fine grain ...

  15. Variation in aggressiveness of Phaeoisariopsis griseola and angular ...

    African Journals Online (AJOL)

    Aggressiveness of fifteen isolates of Phaeoisariopsis griseola and variations in angular leaf spot symptom development in common bean were studied. The isolates were selected based on their virulence and genetic differences and represented Andean, Afro-Andean and Mesoamerican groups of P. griseola.

  16. Angular anisotropy of the cosmic microwave background radiation

    International Nuclear Information System (INIS)

    Silk, J.

    1982-01-01

    The theory of fluctuations in the cosmic microwave background radiation is reviewed. Anisotropy on large-scale (dipole and quadrupole) and on small scales is discussed. The smoothing effects of secondary ionization (fractional ionization x) are found to be unimportant over an angular scale greater than approx.= 5(OMEGAx)sup(1/3) degrees. (author)

  17. Holographic toolkit for optical communication beyond orbital angular momentum

    CSIR Research Space (South Africa)

    Rosales-Guzman, C

    2016-09-01

    Full Text Available , suggested over 30 years ago, comprises the use of spatial modes of light as information carriers. Along this direction, light beams endowed with orbital angular momentum (OAM) have been demonstrated as potential information carriers in both, free space...

  18. Cosmology Large Angular Scale Surveyor (CLASS) Focal Plane Development

    Science.gov (United States)

    Chuss, D. T.; Ali, A.; Amiri, M.; Appel, J.; Bennett, C. L.; Colazo, F.; Denis, K. L.; Dünner, R.; Essinger-Hileman, T.; Eimer, J.; Fluxa, P.; Gothe, D.; Halpern, M.; Harrington, K.; Hilton, G.; Hinshaw, G.; Hubmayr, J.; Iuliano, J.; Marriage, T. A.; Miller, N.; Moseley, S. H.; Mumby, G.; Petroff, M.; Reintsema, C.; Rostem, K.; U-Yen, K.; Watts, D.; Wagner, E.; Wollack, E. J.; Xu, Z.; Zeng, L.

    2016-08-01

    The Cosmology Large Angular Scale Surveyor (CLASS) will measure the polarization of the Cosmic Microwave Background to search for and characterize the polarized signature of inflation. CLASS will operate from the Atacama Desert and observe ˜ 70 % of the sky. A variable-delay polarization modulator provides modulation of the polarization at ˜ 10 Hz to suppress the 1/ f noise of the atmosphere and enable the measurement of the large angular scale polarization modes. The measurement of the inflationary signal across angular scales that spans both the recombination and reionization features allows a test of the predicted shape of the polarized angular power spectra in addition to a measurement of the energy scale of inflation. CLASS is an array of telescopes covering frequencies of 38, 93, 148, and 217 GHz. These frequencies straddle the foreground minimum and thus allow the extraction of foregrounds from the primordial signal. Each focal plane contains feedhorn-coupled transition-edge sensors that simultaneously detect two orthogonal linear polarizations. The use of single-crystal silicon as the dielectric for the on-chip transmission lines enables both high efficiency and uniformity in fabrication. Integrated band definition has been implemented that both controls the bandpass of the single-mode transmission on the chip and prevents stray light from coupling to the detectors.

  19. Gravitational Field of Ultrarelativistic Objects with Angular Momentum

    International Nuclear Information System (INIS)

    Fursaev, Dmitri V

    2006-01-01

    A brief review of recently found gyraton metrics which describe the gravitational field of objects having an angular momentum and moving with the velocity of light is given. The gyraton metrics belong to a class of exact plane wave solutions of four and higher dimensional Einstein equations in vacuum or in the presence of a negative cosmological constant

  20. Search for new physics in dijet mass and angular distributions

    Indian Academy of Sciences (India)

    We present a search for physics beyond the Standard Model in proton–proton collisions at a centre-of-mass energy of s = 7 TeV, performed with the ATLAS detector at the Large Hadron Collider (LHC). No evidence for new physics is found in dijet mass and angular distributions and stringent limits are set on a variety of ...

  1. Angular distributions and total yield of laser ablated silver

    DEFF Research Database (Denmark)

    Svendsen, Winnie Edith; Nordskov, A.; Schou, Jørgen

    1997-01-01

    The angular distribution of laser ablated silver has been measured in situ with a newly constructed setup with an array of microbalances. The distribution is strongly peaked in the forward direction corresponding to cospθ, where p varies between 5 and 9 for laser fluences from 2 to 7 J/cm2 at 355...

  2. Generation of ultraviolet radiation with wide angular tolerance in ...

    Indian Academy of Sciences (India)

    Tangential phase-matching has been realised in cesium lithium borate (CLBO) crystal for the first time for the generation of fourth harmonic (266 nm) of Nd:YAG and third harmonic (226.7 nm) of a dye laser radiation by second harmonic generation and sum-frequency mixing with the angular tolerance as large as 22 mrad ...

  3. Quantitatively measuring the orbital angular momentum density of light : Presentation

    CSIR Research Space (South Africa)

    Dudley, Angela L

    2013-08-01

    Full Text Available Although many techniques are efficient at measuring optical orbital angular momentum (OAM), they do not allow one to obtain a quantitative measurement for the OAM density across an optical field and instead only measure its global OAM. Numerous...

  4. Exact angular momentum projection based on cranked HFB solution

    Energy Technology Data Exchange (ETDEWEB)

    Enami, Kenichi; Tanabe, Kosai; Yosinaga, Naotaka [Saitama Univ., Urawa (Japan). Dept. of Physics

    1998-03-01

    Exact angular momentum projection of cranked HFB solutions is carried out. It is reconfirmed from this calculation that cranked HFB solutions reproduce the intrinsic structure of deformed nucleus. The result also indicates that the energy correction from projection is important for further investigation of nuclear structure. (author)

  5. Angular momentum projection of tilted axis rotating states

    Energy Technology Data Exchange (ETDEWEB)

    Oi, M.; Onishi, N.; Tajima, N. [Tokyo Univ. (Japan); Horibata, T.

    1998-03-01

    We applied an exact angular momentum projection to three dimensional cranked HFB (3d-CHFB) states. Tilted axis rotating states (TAR) and principal axis rotating states (PAR) are compared. It is shown that TAR is more adequate than PAR for description of the back bending phenomena driven by tilted rotation or wobbling motion. (author)

  6. Generation of ultraviolet radiation with wide angular tolerance in ...

    Indian Academy of Sciences (India)

    Home; Journals; Pramana – Journal of Physics; Volume 55; Issue 3 ... Non-linear optics; ultraviolet radiation; tangential phase-matching; Sellmeier dispersion ... of Nd:YAG and third harmonic (226.7 nm) of a dye laser radiation by second harmonic generation and sum-frequency mixing with the angular tolerance as large as ...

  7. The vorticity and angular momentum budgets of Asian summer ...

    Indian Academy of Sciences (India)

    The study delineates the vorticity and angular momentum balances of Asian summer monsoon during the evolution and established phases. It also elucidates the differences between these balances in the National Centre for Environmental Prediction/National Centre for Atmospheric Research (NCEP/NCAR) reanalysis ...

  8. Angular dose dependence of Matrixx TM and its calibration.

    Science.gov (United States)

    Wolfsberger, Luciant D; Wagar, Matthew; Nitsch, Paige; Bhagwat, Mandar S; Zygmanski, Piotr

    2010-01-28

    One of the applications of MatriXX (IBA Dosimetry) is experimental verification of dose for IMRT, VMAT, and tomotherapy. For cumulative plan verification, dose is delivered for all the treatment gantry angles to a stationary detector. Experimental calibration of MatriXX detector recommended by the manufacturer involves only AP calibration fields and does not address angular dependency of MatriXX. Angular dependency may introduce dose bias in cumulative plan verification if not corrected. For this reason, we characterized angular dependency of MatriXX and developed a method for its calibration. We found relatively large discrepancies in responses to posterior vs. anterior fields for four MatriXX (Evolution series) detectors (up to 11%), and relatively large variability of responses as a function of gantry angle in the gantry angle ranges of 91 degrees-110 degrees and 269 degrees-260 degrees. With our calibration method, the bias due to angular dependency is effectively removed in experimental verification of IMRT and VMAT plans.

  9. The angular ordering in soft-gluon emission

    International Nuclear Information System (INIS)

    Tesima, K.

    1987-01-01

    The way to evaluate multi-parton cross-sections systematically is discussed. In the leading-double-log approximation in QCD, the successive emission of soft gluons is at successively smaller angles. The angular ordering, however, is violated in the next-to-leading order

  10. Cosmology Large Angular Scale Surveyor (CLASS) Focal Plane Development

    Science.gov (United States)

    Chuss, D. T.; Ali, A.; Amiri, M.; Appel, J.; Bennett, C. L.; Colazo, F.; Denis, K. L.; Dunner, R.; Essinger-Hileman, T.; Eimer, J.; hide

    2015-01-01

    The Cosmology Large Angular Scale Surveyor (CLASS) will measure the polarization of the Cosmic Microwave Background to search for and characterize the polarized signature of inflation. CLASS will operate from the Atacama Desert and observe approx.70% of the sky. A variable-delay polarization modulator provides modulation of the polarization at approx.10Hz to suppress the 1/f noise of the atmosphere and enable the measurement of the large angular scale polarization modes. The measurement of the inflationary signal across angular scales that spans both the recombination and reionization features allows a test of the predicted shape of the polarized angular power spectra in addition to a measurement of the energy scale of inflation. CLASS is an array of telescopes covering frequencies of 38, 93, 148, and 217 GHz. These frequencies straddle the foreground minimum and thus allow the extraction of foregrounds from the primordial signal. Each focal plane contains feedhorn-coupled transition-edge sensors that simultaneously detect two orthogonal linear polarizations. The use of single-crystal silicon as the dielectric for the on-chip transmission lines enables both high efficiency and uniformity in fabrication. Integrated band definition has been implemented that both controls the bandpass of the single-mode transmission on the chip and prevents stray light from coupling to the detectors.

  11. Synchronization of colloidal rotors through angular optical binding

    Czech Academy of Sciences Publication Activity Database

    Simpson, Stephen Hugh; Chvátal, Lukáš; Zemánek, Pavel

    2016-01-01

    Roč. 93, č. 2 (2016), 023842:1-12 ISSN 2469-9926 R&D Projects: GA ČR GB14-36681G Institutional support: RVO:68081731 Keywords : hydrodynamic properties * colloidal rotors * angular optical binding Subject RIV: BH - Optics, Masers, Lasers Impact factor: 2.925, year: 2016

  12. Data visualization with D3 and AngularJS

    CERN Document Server

    Körner, Christoph

    2015-01-01

    If you are a web developer with experience in AngularJS and want to implement interactive visualizations using D3.js, this book is for you. Knowledge of SVG or D3.js will give you an edge to get the most out of this book.

  13. A new uncertainty relation for angular momentum and angle

    International Nuclear Information System (INIS)

    Kranold, H.U.

    1984-01-01

    An uncertainty relation of the form ΔL 2 ΔSo >=sup(h/2π)/sub(2) is derived for angular momentum and angle. The non-linear operator So measures angles and has a simple interpretation. Subject to very general conditions of rotational invariance the above relation is unique. Radial momentum is not quantized

  14. Demonstrating the Direction of Angular Velocity in Circular Motion

    Science.gov (United States)

    Demircioglu, Salih; Yurumezoglu, Kemal; Isik, Hakan

    2015-01-01

    Rotational motion is ubiquitous in nature, from astronomical systems to household devices in everyday life to elementary models of atoms. Unlike the tangential velocity vector that represents the instantaneous linear velocity (magnitude and direction), an angular velocity vector is conceptually more challenging for students to grasp. In physics…

  15. Fission fragment mass and angular distributions: Probes to study ...

    Indian Academy of Sciences (India)

    cesses (often commonly called quasifission in the literature) differ subtly in terms of the observables which are measured in a reaction, and disentangling the contributions of each of these processes is very challenging. While FF is observed when the fission barrier becomes vanishingly small at very high angular momenta, ...

  16. Earth Rotation and Coupling to Changes in Atmospheric Angular Momentum

    Science.gov (United States)

    Rosen, Richard D.; Frey, H. (Technical Monitor)

    2000-01-01

    The research supported under the contract dealt primarily with: (a) the mechanisms responsible for the exchange of angular momentum between the solid Earth and atmosphere; (b) the quality of the data sets used to estimate atmospheric angular momentum; and (c) the ability of these data and of global climate models to detect low-frequency signals in the momentum and, hence, circulation of the atmosphere. Three scientific papers reporting on the results of this research were produced during the course of the contract. These papers identified the particular torques responsible for the peak in atmospheric angular momentum and length-of-day during the 1982-93 El Nino event, and, more generally, the relative roles of torques over land and ocean in explaining the broad spectrum of variability in the length-of-day. In addition, a tendency for interannual variability in atmospheric angular momentum to increase during the last several decades of the 20th century was found in both observations and a global climate model experiment.

  17. Data compilation of angular distributions of sputtered atoms

    International Nuclear Information System (INIS)

    Yamamura, Yasunori; Takiguchi, Takashi; Tawara, Hiro.

    1990-01-01

    Sputtering on a surface is generally caused by the collision cascade developed near the surface. The process is in principle the same as that causing radiation damage in the bulk of solids. Sputtering has long been regarded as an undesirable dirty effect which destroys the cathodes and grids in gas discharge tubes or ion sources and contaminates plasma and the surrounding walls. However, sputtering is used today for many applications such as sputter ion sources, mass spectrometers and the deposition of thin films. Plasma contamination and the surface erosion of first walls due to sputtering are still the major problems in fusion research. The angular distribution of the particles sputtered from solid surfaces can possibly provide the detailed information on the collision cascade in the interior of targets. This report presents a compilation of the angular distribution of sputtered atoms at normal incidence and oblique incidence in the various combinations of incident ions and target atoms. The angular distribution of sputtered atoms from monatomic solids at normal incidence and oblique incidence, and the compilation of the data on the angular distribution of sputtered atoms are reported. (K.I.)

  18. Generation of ultraviolet radiation with wide angular tolerance in ...

    Indian Academy of Sciences (India)

    CLBO) crystal for the first time for the generation of fourth harmonic (266 nm) of Nd:YAG and third harmonic. (226.7 nm) of a dye laser radiation by second harmonic generation and sum-frequency mixing with the angular tolerance as large as ...

  19. Angular dependence of IPEN parallels plates ionization chambers

    International Nuclear Information System (INIS)

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

    1989-01-01

    The angular dependence of parallel plates ionization chambers for X-radiation of low energy is studied, aiming at the correction of any influence that may occur, due to positioning. The national fabrication chambers behaviour is evaluated and the results are compared with imported similar chambers. (C.G.C.) [pt

  20. Angular dependence of EEDF in ion-beam plasma

    International Nuclear Information System (INIS)

    Dudin, S.V.

    1995-01-01

    In a previous paper the results of measurements of electron energy distribution function (EEDF) in ion-beam plasma created by low energy broad ion beam had been presented regardless of the angular dependence of the electron distribution. The present work is specifically aimed towards elucidating the spatial structure of the EEDF in the ion-beam plasma. To solve this problem combination of the techniques of cylindrical probe, large plate probe (5 x 5 mm) and two-grid enegoanalyzer was used. Directional operation of the probes makes possible measurement of angular dependence of electron distribution function which is anisotropic in high energy region. To optimize the construction of the probe-analyzer, experiments with grids were performed, which had different size, mesh, and transparency, under different potentials, and with different distances between grids. Numerical simulation of the analyzer was performed too. It is derived that optimal design for measurements in isotropic plasma is the most plate, thin two-grid probe with maximum angular covering. Investigation of angular dependence of EEDF has shown that the distribution of trapped electrons is completely isotropic, whereas in the energy range of var-epsilon > e var-phi pl (var-phi pl - plasma potential) a strong anisotropy of the EEDF is observed

  1. QCD in the infrared with exact angular integrations

    NARCIS (Netherlands)

    Atkinson, D; Bloch, J.C R

    1998-01-01

    In a previous paper we have shown that in quantum chromodynamics the gluon propagator vanishes in the infrared limit, while the ghost propagator is more singular than a simple pole. These results were obtained after angular averaging, but here we go beyond this approximation and perform an exact

  2. Angular distribution of cosmic muons using INO–ICAL prototype ...

    Indian Academy of Sciences (India)

    2012-11-10

    Nov 10, 2012 ... Here, 2, 4, 7 and 9 layers are used in trigger criteria. This particular choice helps to increase the detector solid angular acceptance. 3. Event data analysis. Event data consist of two informations: (i) cosmic ray muon hits per layer and (ii) the corresponding time of arrival. Here, hit information is only used to ...

  3. The phenomenon of nucleon emission at high angular momentum ...

    Indian Academy of Sciences (India)

    This is contrary to the classical notion of monotonously decreasing separation energy with increasing angular momentum. We have reported in ref. [1] some results for 156Er formed in the reaction 96Zr (64Ni,xn) 155Er, which are in good agreement with the experimental results of Henss et al [2] for single neutron emission.

  4. Angular Momentum across the Hubble sequence from the CALIFA survey

    NARCIS (Netherlands)

    Falcón-Barroso, Jesús; Lyubenova, Mariya; van de Ven, Glenn

    We investigate the stellar angular momentum of galaxies across the Hubble sequence from the CALIFA survey. The distribution of CALIFA elliptical and lenticular galaxies in the λRe - ɛe diagram is consistent with that shown by the Atlas3D survey. Our data, however, show that the location of spiral

  5. Numerical simulation of side heating for controlling angular ...

    Indian Academy of Sciences (India)

    One side multipass 'V' butt weld configuration is used for this study. A series of observational tests are done with a special experimental fixture using Manual Metal Arc Welding (MMAW) to validate the proposed FEA model. It is found that the angular distortion has decreased from 2 mm to 0.4 mm with change in side heating ...

  6. A perturbed angular correlation spectrometer for material science ...

    Indian Academy of Sciences (India)

    Abstract. A four-detector perturbed angular correlation (PAC) spectrometer has been developed with ultra-fast BaF2 detectors to acquire four coincidence spectra simultane- ously, two at 180° and two at 90°. This spectrometer has double efficiency compared to that of a three-detector set-up. Higher efficiency is desirable for ...

  7. The phenomenon of nucleon emission at high angular momentum ...

    Indian Academy of Sciences (India)

    physics pp. 75–93. The phenomenon of nucleon emission at high angular momentum states of fused compound systems. T R RAJASEKARAN1 £, S SELVARAJ2 and S SANTHOSH KUMAR3. 1Department of Physics, Manonmaniam Sundaranar University, Tirunelveli 627 012, India. 2Department of Physics, The M.D.T. ...

  8. THE SIMULATION OF SCATTERING OF ELECTROMAGNETIC WAVES ON ANGULAR STRUCTURES.

    Directory of Open Access Journals (Sweden)

    P. A. Preobrazhensky

    2017-02-01

    Full Text Available The paper discusses the characteristics of scattering of electromagnetic waves on the angular diffraction structures. The solution of the problem is based on the method of integral equations. A comparative analysis of the scattering characteristics of structures with different shape is carried out.

  9. A perturbed angular correlation spectrometer for material science ...

    Indian Academy of Sciences (India)

    A four-detector perturbed angular correlation (PAC) spectrometer has been developed with ultra-fast BaF2 detectors to acquire four coincidence spectra simultaneously, two at 180° and two at 90°. This spectrometer has double efficiency compared to that of a three-detector set-up. Higher efficiency is desirable for PAC ...

  10. Continuous Variable Entanglement and Squeezing of Orbital Angular Momentum States

    DEFF Research Database (Denmark)

    Lassen, Mikael Østergaard; Leuchs, Gerd; Andersen, Ulrik Lund

    2009-01-01

    We report the first experimental characterization of the first-order continuous variable orbital angular momentum states. Using a spatially nondegenerate optical parametric oscillator (OPO) we produce quadrature entanglement between the two first-order Laguerre-Gauss modes. The family of orbital...

  11. Energy and angular distributions of backscattered electrons from ...

    Indian Academy of Sciences (India)

    Abstract. The energy and angular distributions of backscattered electrons produced under the impact of 5 keV electrons with thick Al, Ti, Ag, W and Pt targets are measured. The energy range of backscattered electrons is considered between EB = 50 eV and 5000. eV. The angle of incidence α and take-off angle θ are ...

  12. Energy and angular distributions of backscattered electrons from ...

    Indian Academy of Sciences (India)

    The energy and angular distributions of backscattered electrons produced under the impact of 5 keV electrons with thick Al, Ti, Ag, W and Pt targets are measured. The energy range of backscattered electrons is considered between B = 50 eV and 5000 eV. The angle of incidence α and take-off angle are chosen to have ...

  13. Implementing quantum walks using orbital angular momentum of classical light

    CSIR Research Space (South Africa)

    Goyal, SK

    2013-06-01

    Full Text Available We present an implementation scheme for a quantum walk in the orbital angular momentum space of a laser beam. The scheme makes use of a ring interferometer, containing a quarter-wave plate and a q plate. This setup enables one to perform...

  14. Study of selected benzyl azides by UV photoelectron spectroscopy and mass spectrometry

    Science.gov (United States)

    Pinto, R. M.; Olariu, R. I.; Lameiras, J.; Martins, F. T.; Dias, A. A.; Langley, G. J.; Rodrigues, P.; Maycock, C. D.; Santos, J. P.; Duarte, M. F.; Fernandez, M. T.; Costa, M. L.

    2010-09-01

    Benzyl azide and the three methylbenzyl azides were synthesized and characterized by mass spectrometry (MS) and ultraviolet photoelectron spectroscopy (UVPES). The electron ionization fragmentation mechanisms for benzyl azide and their methyl derivatives were studied by accurate mass measurements and linked scans at constant B/ E. For benzyl azide, in order to clarify the fragmentation mechanism, labelling experiments were performed. From the mass analysis of methylbenzyl azides isomers it was possible to differentiate the isomers ortho, meta and para. The abundance and nature of the ions resulting from the molecular ion fragmentation, for the three distinct isomers of substituted benzyl azides, were rationalized in terms of the electronic properties of the substituent. Concerning the para-isomer, IRC calculations were performed at UHF/6-31G(d) level. The photoionization study of benzyl azide, with He(I) radiation, revealed five bands in the 8-21 eV ionization energies region. From every photoelectron spectrum of methylbenzyl azides isomers it has been identified seven bands, on the same range as the benzyl azide. Interpretation of the photoelectron spectra was accomplished applying Koopmans' theorem to the SCF orbital energies obtained at HF/6-311++G(d, p) level.

  15. Analysis of Dietz's single, rectangular pulse theory for the generation of radiation via photoelectrons

    International Nuclear Information System (INIS)

    Dipp, T.M.

    1993-12-01

    The generation of radiation via photoelectrons induced off of a conducting surface has been analytically modeled and computationally simulated by several researchers. This paper analyzes and compares Dietz's theory predictions with my research to form a unified foundation of consistent, inter-supporting results that should provide confidence in the independently performed basic research and resulting scaling laws and predictions. In doing so, this paper concentrated on Dietz's small-spot, single, rectangular, ''weak'' pulse theory and equations, which involve nonrelativistic, monoenergetic photoelectrons emitted normal to a conducting surface in vacuum. In this paper I: (1) analytically compare Dietz's theory equations with my theory equations, (2) compare Dietz's theoretical scaling laws with my Particle-In-Cell (PIC) code simulation results, and (3) make Dietz's equations easier to use in predicting and optimizing photoelectron-generated radiation. As a result, it is shown that Dietz's equations match my theory's equations in their predicted scaling laws, differing only slightly in their coefficients and unique model parameters. Also, Dietz's equations generally agree with the PIC code results. Finally, optimization analysis showed that theoretical conversion efficiencies for typical real metals can meet and exceed values of 10 -5 if optimal photon energies of 15 to 20 eV are used. Even better efficiencies should be possible if the small-spot constraint is violated as well

  16. Observation of relaxation on time scale of core hole decay by coincidence photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Ohno, Masahide

    2007-01-01

    It is shown by a many-body theory that when the relaxation time of a metastable core hole state(s) to the most stable one is comparable to or shorter than core hole decay time of the former state(s), a comparison between the singles (noncoincidence) photoelectron spectroscopy (PES) spectrum and the coincidence one provides a direct evidence of the relaxation. In principle the variation with photoelectron kinetic energy of relaxation (or charge transfer (CT)) time can be determined. By singles measurement the correlation of a photoelectron generated by creation of the metastable states not only with an Auger electron generated by annihilation of the same core hole state but also with an Auger electron generated by annihilation of the stable state via relaxation of the metastable state, is completely lost, unless only the metastable state is observed by PES, whereas the correlation often manifests directly in the coincidence spectra. Thus, compared to the coincidence spectroscopy the singles one is often much less capable of elucidating the competition between relaxation and core hole decay of a metastable state. Such examples are discussed

  17. Model independent approach to the single photoelectron calibration of photomultiplier tubes

    Energy Technology Data Exchange (ETDEWEB)

    Saldanha, R.; Grandi, L.; Guardincerri, Y.; Wester, T.

    2017-08-01

    The accurate calibration of photomultiplier tubes is critical in a wide variety of applications in which it is necessary to know the absolute number of detected photons or precisely determine the resolution of the signal. Conventional calibration methods rely on fitting the photomultiplier response to a low intensity light source with analytical approximations to the single photoelectron distribution, often leading to biased estimates due to the inability to accurately model the full distribution, especially at low charge values. In this paper we present a simple statistical method to extract the relevant single photoelectron calibration parameters without making any assumptions about the underlying single photoelectron distribution. We illustrate the use of this method through the calibration of a Hamamatsu R11410 photomultiplier tube and study the accuracy and precision of the method using Monte Carlo simulations. The method is found to have significantly reduced bias compared to conventional methods and works under a wide range of light intensities, making it suitable for simultaneously calibrating large arrays of photomultiplier tubes.

  18. Photoelectron spectra and electronic structure of nitrogen analogues of boron β-diketonates with aromatic substituents

    Energy Technology Data Exchange (ETDEWEB)

    Tikhonov, Sergey A., E-mail: allser@bk.ru [Far Eastern Federal University, 8 Sukhanova St., Vladivostok, 690950 (Russian Federation); Vovna, Vitaliy I. [Far Eastern Federal University, 8 Sukhanova St., Vladivostok, 690950 (Russian Federation); Borisenko, Aleksandr V. [Vladivostok Branch of Russian Customs Academy, 16v Strelkovaya St., Vladivostok, 690034 (Russian Federation)

    2016-11-15

    Highlights: • The electronic structures of three nitrogen analogues of boron β-diketonates have been investigated. • UV photoelectron spectra have been interpreted. • The structure of the UV photoelectron spectra is in good agreement with the energies and compositions of Kohn-Sham orbitals. - Abstract: The electronic structure of three nitrogen analogoues of boron β-diketonates containing aromatic substituents was studied by the ultraviolet photoelectron spectroscopy and within the density functional theory. In order to determine effects of heteroatom substitution in the chelate ligand, a comparative analysis was carried out for the electronic structure of three model compounds. In a range of model compounds, the HOMO's nature was revealed to be the same. The HOMO-1 orbital of nitrogen containing compounds is determined by the presence of lone electron pairs of nitrogen. In a range of the complexes under study, the influence of aromatic substituents on the electronic structure was defined. In the imidoylamidinate complex, in contrast to formazanates and β-diketonates, it was found the absence of any noticeable mixing of π-orbitals of the chelate and benzene rings. It was shown that within energy range to 11 eV, the calculated results reproduce well the energy differences between the ionized states of complexes.

  19. Explaining the MoVO4- photoelectron spectrum: Rationalization of geometric and electronic structure.

    Science.gov (United States)

    Thompson, Lee M; Jarrold, Caroline C; Hratchian, Hrant P

    2017-03-14

    Attempts to reconcile simulated photoelectron spectra of MoVO 4 - clusters are complicated by the presence of very low energy barriers in the potential energy surfaces (PESs) of the lowest energy spin states and isomers. Transition state structures associated with the inversion of terminal oxygen ligands are found to lie below, or close to, the zero point energy of associated modes, which themselves are found to be of low frequency and thus likely to be significantly populated in the experimental characterization. Our simulations make use of Boltzmann averaging over low-energy coordinates and full mapping of the PES to obtain simulations in good agreement with experimental spectra. Furthermore, molecular orbital analysis of accessible final spin states reveals the existence of low energy two-electron transitions in which the final state is obtained from a finite excitation of an electron along with the main photodetachment event. Two-electron transitions are then used to justify the large difference in intensity between different bands present in the photoelectron spectrum. Owing to the general presence of terminal ligands in metal oxide clusters, this study identifies and proposes a solution to issues that are generally encountered when attempting to simulate transition metal cluster photoelectron spectroscopy.

  20. Power calculation of linear and angular incremental encoders

    Science.gov (United States)

    Prokofev, Aleksandr V.; Timofeev, Aleksandr N.; Mednikov, Sergey V.; Sycheva, Elena A.

    2016-04-01

    Automation technology is constantly expanding its role in improving the efficiency of manufacturing and testing processes in all branches of industry. More than ever before, the mechanical movements of linear slides, rotary tables, robot arms, actuators, etc. are numerically controlled. Linear and angular incremental photoelectric encoders measure mechanical motion and transmit the measured values back to the control unit. The capabilities of these systems are undergoing continual development in terms of their resolution, accuracy and reliability, their measuring ranges, and maximum speeds. This article discusses the method of power calculation of linear and angular incremental photoelectric encoders, to find the optimum parameters for its components, such as light emitters, photo-detectors, linear and angular scales, optical components etc. It analyzes methods and devices that permit high resolutions in the order of 0.001 mm or 0.001°, as well as large measuring lengths of over 100 mm. In linear and angular incremental photoelectric encoders optical beam is usually formulated by a condenser lens passes through the measuring unit changes its value depending on the movement of a scanning head or measuring raster. Past light beam is converting into an electrical signal by the photo-detecter's block for processing in the electrical block. Therefore, for calculating the energy source is a value of the desired value of the optical signal at the input of the photo-detecter's block, which reliably recorded and processed in the electronic unit of linear and angular incremental optoelectronic encoders. Automation technology is constantly expanding its role in improving the efficiency of manufacturing and testing processes in all branches of industry. More than ever before, the mechanical movements of linear slides, rotary tables, robot arms, actuators, etc. are numerically controlled. Linear and angular incremental photoelectric encoders measure mechanical motion and

  1. Continuous theta burst stimulation of angular gyrus reduces subjective recollection.

    Directory of Open Access Journals (Sweden)

    Yasemin Yazar

    Full Text Available The contribution of lateral parietal regions such as the angular gyrus to human episodic memory has been the subject of much debate following widespread observations of left parietal activity in healthy volunteers during functional neuroimaging studies of memory retrieval. Patients with lateral parietal lesions are not amnesic, but recent evidence indicates that their memory abilities may not be entirely preserved. Whereas recollection appears intact when objective measures such as source accuracy are used, patients often exhibit reduced subjective confidence in their accurate recollections. When asked to recall autobiographical memories, they may produce spontaneous narratives that lack richness and specificity, but can remember specific details when prompted. Two distinct theoretical accounts have been proposed to explain these results: that the patients have a deficit in the bottom-up capturing of attention by retrieval output, or that they have an impairment in the subjective experience of recollection. The present study aimed to differentiate between these accounts using continuous theta burst stimulation (cTBS in healthy participants to disrupt function of specific left parietal subregions, including angular gyrus. Inconsistent with predictions of the attentional theory, angular gyrus cTBS did not result in greater impairment of free recall than cued recall. Supporting predictions of the subjective recollection account, temporary disruption of angular gyrus was associated with highly accurate source recollection accuracy but a selective reduction in participants' rated source confidence. The findings are consistent with a role for angular gyrus in the integration of memory features into a conscious representation that enables the subjective experience of remembering.

  2. The role of angular momentum conservation law in statistical mechanics

    Directory of Open Access Journals (Sweden)

    I.M. Dubrovskii

    2008-12-01

    Full Text Available Within the limits of Khinchin ideas [A.Y. Khinchin, Mathematical Foundation of Statistical Mechanics. NY, Ed. Dover, 1949] the importance of momentum and angular momentum conservation laws was analyzed for two cases: for uniform magnetic field and when magnetic field is absent. The law of momentum conservation does not change the density of probability distribution in both cases, just as it is assumed in the conventional theory. It is shown that in systems where the kinetic energy depends only on particle momenta canonically conjugated with Cartesian coordinates being their diagonal quadric form,the angular momentum conservation law changes the density of distribution of the system only in case the full angular momentum of a system is not equal to zero. In the gas of charged particles in a uniform magnetic field the density of distribution also varies if the angular momentum is zero [see Dubrovskii I.M., Condensed Matter Physics, 2206, 9, 23]. Two-dimensional gas of charged particles located within a section of an endless strip filled with gas in magnetic field is considered. Under such conditions the angular momentum is not conserved. Directional particle flows take place close to the strip boundaries, and, as a consequence, the phase trajectory of the considered set of particles does not remain within the limited volume of the phase space. In order to apply a statistical thermodynamics method, it was suggested to consider near-boundary trajectories relative to a reference system that moves uniformly. It was shown that if the diameter of an orbit having average thermal energy is much smaller than a strip width, the corrections to thermodynamic functions are small depending on magnetic field. Only the average velocity of near-boundary particles that form near-boundary electric currents creating the paramagnetic moment turn out to be essential.

  3. Effect of the energy spectrum and angular momentum of pre-scission neutrons on the prediction of fission fragment angular anisotropy by the models

    Science.gov (United States)

    Soheyli, Saeed; Khanlari, Marzieh Varasteh

    2016-04-01

    Effects of the various neutron emission energy spectra, as well as the influence of the angular momentum of pre-scission neutrons on theoretical predictions of fission fragment angular anisotropies for several heavy-ion induced fission systems are considered. Although theoretical calculations of angular anisotropy are very sensitive to neutron emission correction, the effects of the different values of kinetic energy of emitted neutrons derived from the various neutron emission energy spectra before reaching to the saddle point on the prediction of fission fragment angular distribution by the model are not significant and can be neglected, since these effects on angular anisotropies of fission fragments for a wide range of fissility parameters and excitation energies of compound nuclei are not more than 10%. Furthermore, the theoretical prediction of fission fragment angular anisotropy is not sensitive to the angular momentum of emitted neutrons.

  4. Photoelectron imaging, probe of the dynamics: from atoms... to clusters; Imagerie de photoelectrons, sonde de la dynamique: des atomes... aux agregats

    Energy Technology Data Exchange (ETDEWEB)

    Lepine, F

    2003-06-15

    This thesis concerns the study of the deexcitation of clusters and atoms by photoelectron imaging. The first part is dedicated to thermionic emission of a finite size system. A 3-dimensional imaging setup allows us to measure the time evolution of the kinetic energy spectrum of electrons emitted from different clusters (W{sub n}{sup -}, C{sub n}{sup -}, C{sub 60}). Then we have a direct access to the fundamental quantities which characterize this statistical emission: the temperature of the finite heat bath and the decay rate. The second part concerns the ionization of atomic Rydberg states placed in a static electric field. We performed the first experiment of photoionization microscopy which allows us to obtain a picture which is the macroscopic projection of the electronic wave function. Then we have access to the detail of the photoionization and particularly to the quantum properties of the electron usually confined at the atomic scale. (author)

  5. X-Ray Photoelectron Spectroscopy of Stabilized Zirconia Films with Embedded Au Nanoparticles Formed under Irradiation with Gold Ions

    Science.gov (United States)

    Zubkov, S. Yu.; Antonov, I. N.; Gorshkov, O. N.; Kasatkin, A. P.; Kryukov, R. N.; Nikolichev, D. E.; Pavlov, D. A.; Shenina, M. E.

    2018-03-01

    Nanosized films of stabilized zirconia with Au nanoparticles formed by implanting Au ions are studied by X-ray photoelectron spectroscopy and transmission electron microscopy. The effect of irradiation of films with Au ions and postimplantation annealing on the distribution of chemical elements and zirconium- containing ZrO x compounds over the depth of the films is studied. Based on the data on the dimensional shift of the Au 4 f photoelectron line, the average value of the nanoparticle size is determined.

  6. A New Shape Description Method Using Angular Radial Transform

    Science.gov (United States)

    Lee, Jong-Min; Kim, Whoi-Yul

    Shape is one of the primary low-level image features in content-based image retrieval. In this paper we propose a new shape description method that consists of a rotationally invariant angular radial transform descriptor (IARTD). The IARTD is a feature vector that combines the magnitude and aligned phases of the angular radial transform (ART) coefficients. A phase correction scheme is employed to produce the aligned phase so that the IARTD is invariant to rotation. The distance between two IARTDs is defined by combining differences in the magnitudes and aligned phases. In an experiment using the MPEG-7 shape dataset, the proposed method outperforms existing methods; the average BEP of the proposed method is 57.69%, while the average BEPs of the invariant Zernike moments descriptor and the traditional ART are 41.64% and 36.51%, respectively.

  7. Characteristic angular scales in cosmic microwave background radiation

    International Nuclear Information System (INIS)

    Ghasemi, F.; Bahraminasab, A.; Movahed, M.S.; Rahvar, S.; Sreenivasan, K.R.; Tabar, M.R.R.

    2006-12-01

    We investigate the stochasticity in temperature fluctuations in the cosmic microwave background (CMB) radiation data from the Wilkinson Microwave Anisotropy Probe. We show that the angular fluctuation of the temperature is a Markov process with a Markov angular scale, Markov 1.01 -0.07 +0.09 . We characterize the complexity of the CMB fluctuations by means of a Fokker-Planck or Langevin equation and measure the associated Kramers-Moyal coefficients for the fluctuating temperature field T(n-circumflex) and its increment, ΔT = T(n-circumflex 1 ) - T(n-circumflex 2 ). Through this method we show that temperature fluctuations in the CMB have fat tails compared to a Gaussian distribution. (author)

  8. Resilience of hybrid optical angular momentum qubits to turbulence

    Science.gov (United States)

    Farías, Osvaldo Jiménez; D'Ambrosio, Vincenzo; Taballione, Caterina; Bisesto, Fabrizio; Slussarenko, Sergei; Aolita, Leandro; Marrucci, Lorenzo; Walborn, Stephen P.; Sciarrino, Fabio

    2015-02-01

    Recent schemes to encode quantum information into the total angular momentum of light, defining rotation-invariant hybrid qubits composed of the polarization and orbital angular momentum degrees of freedom, present interesting applications for quantum information technology. However, there remains the question as to how detrimental effects such as random spatial perturbations affect these encodings. Here, we demonstrate that alignment-free quantum communication through a turbulent channel based on hybrid qubits can be achieved with unit transmission fidelity. In our experiment, alignment-free qubits are produced with q-plates and sent through a homemade turbulence chamber. The decoding procedure, also realized with q-plates, relies on both degrees of freedom and renders an intrinsic error-filtering mechanism that maps errors into losses.

  9. Angular dependence of the exchange bias for the bistable state

    Energy Technology Data Exchange (ETDEWEB)

    Bai, Yuhao [College of Physics and Electronic Information, Shanxi Normal University, Linfen 041004 (China); Research College of materials science, Shanxi Normal University, Linfen 041004 (China); Xu, Xiaohong, E-mail: xuxh@dns.sxnu.edu.cn [Research College of materials science, Shanxi Normal University, Linfen 041004 (China); Key Laboratory of Magnetic Molecules and Magnetic Information Materials, Ministry of Education, Shanxi Normal University, Linfen 041004 (China)

    2017-06-15

    The angular dependence of the exchange bias (ADEB) has been investigated in detail when the exchange-coupled ferromagnetic (FM)/antiferromagnetic (AFM) bilayer is in the bistable state. Complete and incomplete jump phenomena were found at the intrinsic easy and hard axes, when they pass through two special positions making the angular deviation of 58.2826° and 121.7174° from the easy axis of the uniaxial anisotropy, respectively. The combination of these different types of the jump phenomena at the intrinsic easy and hard axes yields five distinct types of the ADEB. The physical condition for each type of ADEB is established. Additionally, the extreme value problem of the exchange bias field and coercivity are also discussed, which is an important technological issue in the design of the magnetoresistive and spintronic devices. These results enable us to make a comprehensive understanding of the experimental ADEB curves.

  10. Angular diameters of Magellanic Cloud plantary nebulae. I. Speckle interferometry

    International Nuclear Information System (INIS)

    Wood, P.R.; Bessell, M.S.; Dopita, M.A.

    1986-01-01

    Speckle interferometric angular diameters of Magellanic Cloud planetary nebulae are presented. The mass of ionized gas in each nebula has been derived from the angular diameter and published H-beta line fluxes; the derives masses range from less than 0.006 to more than 0.19 solar mass. The planetary nebulae observed were the brightest in the Magellanic Clouds; consequently, they are all relatively small, young, bright, and dense. They are almost certainly only partially ionized, so that the masses derived for the ionized parts of the nebula are lower limits to the total nebula mass. The properties of the Magellanic Cloud nebulae are compared with those of planetary nebulae at the galactic center. 27 references

  11. Relativistic correction to the deuteron magnetic moment and angular condition

    International Nuclear Information System (INIS)

    Kondratyuk, L.A.; Strikman, M.I.

    1983-01-01

    The relativistic correction (RC) to the deuteron magnetic moment μsub(d) is investigated using the light-cone dynamics. The restrictions imposed by the angular condition on the electromagnetic current operator of deuteron are discussed in detail. It is shown that the additive model for the current operator of interacting consistuencies is consistent with the angular condition only for the two first terms of expansion of the ''good'' electromagnetic current component jsub(+) in powers of the momentum transfer q. The RC into μsub(d) is calculated using the mattix element of the ''good'' component. The account of RC decreases essentially the discrepancy between the theoretical and experimental values. The value of Δsub(μ) is determined for the Hamada-Johnston potential hard core potential (0.93x10 -2 ) for the Reid soft core potential (0.71x10 -2 ) and for the Paris potential (0.63x10 -2 )

  12. Investigating pointing tasks across angularly coupled display areas

    DEFF Research Database (Denmark)

    Hennecke, Fabian; De Luca, Alexander; Nguyen, Ngo Dieu Huong

    2013-01-01

    user performance still hold – in particular when pointing is performed across differently oriented areas. To answer this question, we conducted an experiment on an angularly coupled display – the Curve – with two input conditions: direct touch and indirect mouse pointer. Our findings show......Pointing tasks are a crucial part of today’s graphical user interfaces. They are well understood for flat displays and most prominently are modeled through Fitts’ Law. For novel displays (e.g., curved displays with multi-purpose areas), however, it remains unclear whether such models for predicting...... that the target position affects overall pointing speed and offset in both conditions. However, we also found that Fitts’ Law can in fact still be used to predict performance as on flat displays. Our results help designers to optimize user interfaces on angularly coupled displays when pointing tasks are involved....

  13. Angular dependence of the parallel plate ionization chambers of Ipen

    International Nuclear Information System (INIS)

    Albuquerque, M. da P.P.; Caldas, L.

    1989-08-01

    The ionization chambers with parallel plates designed and constructed at IPEN for the dosimetry of soft X-radiation fields were studied in relation to thein angular dependence between O and +- 90 0 . The objective of this study is to verify the chambers response variation for small positioning errors during the field dosimetry used in Radiotherapy. The results were compared with those of commercial parallel plate ionization chambers used as secondary and testiary standards. (author) [pt

  14. Spin and orbital angular momentum propagation in anisotropic media: theory

    International Nuclear Information System (INIS)

    Picón, Antonio; Benseny, Albert; Mompart, Jordi; Calvo, Gabriel F

    2011-01-01

    This paper is devoted to a study of the propagation of light beams carrying orbital angular momentum in optically anisotropic media. We first review some properties of homogeneous anisotropic media, and describe how the paraxial formalism is modified in order to proceed with a new approach dealing with the general setting of paraxial propagation along uniaxial inhomogeneous media. This approach is suitable for describing space-variant optical-axis phase plates

  15. Characterization of the bell-shaped vibratory angular rate gyro.

    Science.gov (United States)

    Liu, Ning; Su, Zhong; Li, Qing; Fu, MengYin; Liu, Hong; Fan, JunFang

    2013-08-07

    The bell-shaped vibratory angular rate gyro (abbreviated as BVG) is a novel shell vibratory gyroscope, which is inspired by the Chinese traditional bell. It sensitizes angular velocity through the standing wave precession effect. The bell-shaped resonator is a core component of the BVG and looks like the millimeter-grade Chinese traditional bell, such as QianLong Bell and Yongle Bell. It is made of Ni43CrTi, which is a constant modulus alloy. The exciting element, control element and detection element are uniformly distributed and attached to the resonator, respectively. This work presents the design, analysis and experimentation on the BVG. It is most important to analyze the vibratory character of the bell-shaped resonator. The strain equation, internal force and the resonator's equilibrium differential equation are derived in the orthogonal curvilinear coordinate system. When the input angular velocity is existent on the sensitive axis, an analysis of the vibratory character is performed using the theory of thin shells. On this basis, the mode shape function and the simplified second order normal vibration mode dynamical equation are obtained. The coriolis coupling relationship about the primary mode and secondary mode is established. The methods of the signal processing and control loop are presented. Analyzing the impact resistance property of the bell-shaped resonator, which is compared with other shell resonators using the Finite Element Method, demonstrates that BVG has the advantage of a better impact resistance property. A reasonable means of installation and a prototypal gyro are designed. The gyroscopic effect of the BVG is characterized through experiments. Experimental results show that the BVG has not only the advantages of low cost, low power, long work life, high sensitivity, and so on, but, also, of a simple structure and a better impact resistance property for low and medium angular velocity measurements.

  16. Uniqueness for the inverse backscattering problem for angularly controlled potentials

    International Nuclear Information System (INIS)

    Rakesh; Uhlmann, Gunther

    2014-01-01

    We consider the problem of recovering a smooth, compactly supported potential on R 3 from its backscattering data. We show that if two such potentials have the same backscattering data and the difference of the two potentials has controlled angular derivatives, then the two potentials are identical. In particular, if two potentials differ by a finite linear combination of spherical harmonics with radial coefficients and have the same backscattering data then the two potentials are identical. (paper)

  17. Spatial Angular Compounding Technique for H-Scan Ultrasound Imaging.

    Science.gov (United States)

    Khairalseed, Mawia; Xiong, Fangyuan; Kim, Jung-Whan; Mattrey, Robert F; Parker, Kevin J; Hoyt, Kenneth

    2018-01-01

    H-Scan is a new ultrasound imaging technique that relies on matching a model of pulse-echo formation to the mathematics of a class of Gaussian-weighted Hermite polynomials. This technique may be beneficial in the measurement of relative scatterer sizes and in cancer therapy, particularly for early response to drug treatment. Because current H-scan techniques use focused ultrasound data acquisitions, spatial resolution degrades away from the focal region and inherently affects relative scatterer size estimation. Although the resolution of ultrasound plane wave imaging can be inferior to that of traditional focused ultrasound approaches, the former exhibits a homogeneous spatial resolution throughout the image plane. The purpose of this study was to implement H-scan using plane wave imaging and investigate the impact of spatial angular compounding on H-scan image quality. Parallel convolution filters using two different Gaussian-weighted Hermite polynomials that describe ultrasound scattering events are applied to the radiofrequency data. The H-scan processing is done on each radiofrequency image plane before averaging to get the angular compounded image. The relative strength from each convolution is color-coded to represent relative scatterer size. Given results from a series of phantom materials, H-scan imaging with spatial angular compounding more accurately reflects the true scatterer size caused by reductions in the system point spread function and improved signal-to-noise ratio. Preliminary in vivo H-scan imaging of tumor-bearing animals suggests this modality may be useful for monitoring early response to chemotherapeutic treatment. Overall, H-scan imaging using ultrasound plane waves and spatial angular compounding is a promising approach for visualizing the relative size and distribution of acoustic scattering sources. Copyright © 2018 World Federation for Ultrasound in Medicine and Biology. Published by Elsevier Inc. All rights reserved.

  18. Automatic spectrometer for γ-γ angular correlation

    International Nuclear Information System (INIS)

    Saxena, R.N.; Monteiro, M.T.S.; Bairrio Nuevo Junior, A.

    1974-01-01

    An automated γ-γ angular correlation spectrometer is described in detail. Eletronic arrangements used in integral and differential measurements have also been described. In part I there is a short theoretical introduction, the experimental arrangement is described in part II. The results of the directional correlation measurement of γ-cascades in 60 Ni and 75 As and of the lifetime measurement of excited states in 181 Ta and 81 Br have been described in part III

  19. Characterization of the Bell-Shaped Vibratory Angular Rate Gyro

    Directory of Open Access Journals (Sweden)

    Junfang Fan

    2013-08-01

    Full Text Available The bell-shaped vibratory angular rate gyro (abbreviated as BVG is a novel shell vibratory gyroscope, which is inspired by the Chinese traditional bell. It sensitizes angular velocity through the standing wave precession effect. The bell-shaped resonator is a core component of the BVG and looks like the millimeter-grade Chinese traditional bell, such as QianLong Bell and Yongle Bell. It is made of Ni43CrTi, which is a constant modulus alloy. The exciting element, control element and detection element are uniformly distributed and attached to the resonator, respectively. This work presents the design, analysis and experimentation on the BVG. It is most important to analyze the vibratory character of the bell-shaped resonator. The strain equation, internal force and the resonator's equilibrium differential equation are derived in the orthogonal curvilinear coordinate system. When the input angular velocity is existent on the sensitive axis, an analysis of the vibratory character is performed using the theory of thin shells. On this basis, the mode shape function and the simplified second order normal vibration mode dynamical equation are obtained. The coriolis coupling relationship about the primary mode and secondary mode is established. The methods of the signal processing and control loop are presented. Analyzing the impact resistance property of the bell-shaped resonator, which is compared with other shell resonators using the Finite Element Method, demonstrates that BVG has the advantage of a better impact resistance property. A reasonable means of installation and a prototypal gyro are designed. The gyroscopic effect of the BVG is characterized through experiments. Experimental results show that the BVG has not only the advantages of low cost, low power, long work life, high sensitivity, and so on, but, also, of a simple structure and a better impact resistance property for low and medium angular velocity measurements.

  20. Tunnelling of orbital angular momentum in parallel optical waveguides

    International Nuclear Information System (INIS)

    Alexeyev, C N; Fadeyeva, T A; Yavorsky, M A; Boklag, N A

    2011-01-01

    We study the evolution of circularly polarized optical vortices (OVs) in the system of two coupled few-mode optical fibres. We demonstrate that upon propagation OVs tunnel into the adjacent fibre as a complex superposition of OVs that comprise also OVs of opposite polarization and topological charge. The initial OV may tunnel into the other fibre as the same vortex state of lesser energy. The evolution of the orbital angular momentum in coupled fibres is studied