WorldWideScience

Sample records for atomic shells n

  1. Technical Note: Effect of explicit M and N-shell atomic transitions on a low-energy x-ray source

    Energy Technology Data Exchange (ETDEWEB)

    Watson, Peter G. F., E-mail: peter.watson@mail.mcgill.ca; Seuntjens, Jan [Medical Physics Unit, McGill University, Montreal, Quebec H4A 3J1 (Canada)

    2016-04-15

    Purpose: In EGSnrc, atomic transitions to and from the M and N-shells are treated in an average way by default. This approach is justified in which the energy difference between explicit and average M and N-shell binding energies is less than 1 keV, and for most applications can be considered negligible. However, for simulations of low energy x-ray sources on thin, high-Z targets, characteristic x-rays can make up a significant portion of the source spectra. As of release V4-2.4.0, EGSnrc has included an option to enable a more complete algorithm of all atomic transitions available in the EADL compilation. In this paper, the effect of M and N-shell averaging on the calculation of half-value layer (HVL) and relative depth dose (RDD) curve of a 50 kVp intraoperative x-ray tube with a thin gold target was investigated. Methods: A 50 kVp miniature x-ray source with a gold target (The INTRABEAM System, Carl Zeiss, Germany) was modeled with the EGSnrc user code cavity, both with and without M and N-shell averaging. From photon fluence spectra simulations, the source HVLs were determined analytically. The same source model was then used with egs-chamber to calculate RDD curves in water. Results: A 4% increase of HVL was reported when accounting for explicit M and N-shell transitions, and up to a 9% decrease in local relative dose for normalization at 3 mm depth in water. Conclusions: The EGSnrc default of using averaged M and N-shell binding energies has an observable effect on the HVL and RDD of a low energy x-ray source with high-Z target. For accurate modeling of this class of devices, explicit atomic transitions should be included.

  2. Atomic inner-shell physics

    International Nuclear Information System (INIS)

    Crasemann, B.

    1985-01-01

    This book discusses: relativistic and quantum electrodynamic effects on atomic inner shells; relativistic calculation of atomic transition probabilities; many-body effects in energetic atomic transitions; Auger Electron spectrometry of core levels of atoms; experimental evaluation of inner-vacancy level energies for comparison with theory; mechanisms for energy shifts of atomic K-X rays; atomic physics research with synchrotron radiation; investigations of inner-shell states by the electron energy-loss technique at high resolution; coherence effects in electron emission by atoms; inelastic X-ray scattering including resonance phenomena; Rayleigh scattering: elastic photon scattering by bound electrons; electron-atom bremsstrahlung; X-ray and bremsstrahlung production in nuclear reactions; positron production in heavy-ion collisions, and X-ray processes in heavy-ion collisions

  3. Inner-shell excitation of alkali-metal atoms

    International Nuclear Information System (INIS)

    Tiwary, S.N.

    1987-06-01

    Inner-shell excitation of alkali-metal atoms, which leads to auto-ionization, is reviewed. The validity of quantum mechanical approximation is analyzed and the importance of exchange and correlation is demonstrated. Basic difficulties in making accurate calculations for inner-shell excitation process are discussed. Suggestions are made for further study of inner-shell process in atoms and ions. (author). 26 refs, 4 figs, 1 tab

  4. Relativistic effects in atomic inner-shell transitions

    International Nuclear Information System (INIS)

    Chen, M.H.

    1982-01-01

    Theoretical calculations of atomic inner-shell transition rates based on independent-particle models are reviewed. Factors affecting inner-shell transition rates are examined, particularly the effects of relativity. 48 references, 5 figures

  5. Muonic atoms with vacant electron shells

    International Nuclear Information System (INIS)

    Bacher, R.; Gotta, D.; Simons, L.M.; Missimer, J.; Mukhopadhyay, N.C.

    1985-01-01

    We show that the cascade in muonic atoms with Z<20 ejects sufficient atomic electrons to ionize an isolated muonic atom completely. In gases, the rates with which electrons refill the atomic shell can be accurately deduced from measured and calculated electron transfer cross sections. Thus, we can conclude that completely ionized muonic atoms can be prepared in gases, and that they remain isolated for long enough times at attainable pressures to facilitate studies of fundamental interactions in muonic atoms

  6. Electron induced atomic inner-shell ionization

    International Nuclear Information System (INIS)

    Quarles, C.A.

    1974-01-01

    The current status of cross section measurements for atomic inner-shell ionization by electron bombardment is reviewed. Inner shell ionization studies using electrons as projectiles compliment the similar studies being done with heavy particles, and in addition can provide tests of the theory in those cases when relativistic effects and exchange effects are expected to be important. Both total cross sections and recently measured differential cross sections will be discussed and compared with existing theories where possible. Prospects for further experimental and theoretical work in this area of atomic physics using small electron accelerators will also be discussed

  7. Symmetry chains for the atomic shell model. I. Classification of symmetry chains for atomic configurations

    International Nuclear Information System (INIS)

    Gruber, B.; Thomas, M.S.

    1980-01-01

    In this article the symmetry chains for the atomic shell model are classified in such a way that they lead from the group SU(4l+2) to its subgroup SOsub(J)(3). The atomic configurations (nl)sup(N) transform like irreducible representations of the group SU(4l+2), while SOsub(J)(3) corresponds to total angular momentum in SU(4l+2). The defining matrices for the various embeddings are given for each symmetry chain that is obtained. These matrices also define the projection onto the weight subspaces for the corresponding subsymmetries and thus relate the various quantum numbers and determine the branching of representations. It is shown in this article that three (interrelated) symmetry chains are obtained which correspond to L-S coupling, j-j coupling, and a seniority dependent coupling. Moreover, for l<=6 these chains are complete, i.e., there are no other chains but these. In articles to follow, the symmetry chains that lead from the group SO(8l+5) to SOsub(J)(3) will be discussed, with the entire atomic shell transforming like an irreducible representation of SO(8l+5). The transformation properties of the states of the atomic shell will be determined according to the various symmetry chains obtained. The symmetry lattice discussed in this article forms a sublattice of the larger symmetry lattice with SO(8l+5) as supergroup. Thus the transformation properties of the states of the atomic configurations, according to the various symmetry chains discussed in this article, will be obtained too. (author)

  8. Kinetic-energy density functional: Atoms and shell structure

    International Nuclear Information System (INIS)

    Garcia-Gonzalez, P.; Alvarellos, J.E.; Chacon, E.

    1996-01-01

    We present a nonlocal kinetic-energy functional which includes an anisotropic average of the density through a symmetrization procedure. This functional allows a better description of the nonlocal effects of the electron system. The main consequence of the symmetrization is the appearance of a clear shell structure in the atomic density profiles, obtained after the minimization of the total energy. Although previous results with some of the nonlocal kinetic functionals have given incipient structures for heavy atoms, only our functional shows a clear shell structure for most of the atoms. The atomic total energies have a good agreement with the exact calculations. Discussion of the chemical potential and the first ionization potential in atoms is included. The functional is also extended to spin-polarized systems. copyright 1996 The American Physical Society

  9. Autoionization of inner atomic shells during β decay

    International Nuclear Information System (INIS)

    Batkin, I.S.; Kopytin, I.V.; Smirnov, Y.G.; Churakova, T.A.

    1981-01-01

    A theory describing the autoionization of inner atomic shells in nuclear β decay has been developed. It is shown on the basis of diagram technique that in first order in Z -1 the matrix element of the process is represented in the form of the sum of two terms, one of which corresponds to ionization of an electron shell of an atom with sudden change of the charge of the nucleus, and the other to direct interaction of a β particle with the electrons of the atomic shell. Specific calculations are carried out in the nonrelativistic approximation with use of electron wave functions and a Green's function constructed with a Teitz screened Coulomb potential, the systematic inclusion of the contribution of the direct mechanism being carried out for the first time. For the case of β decay of the isotopes 35 S, 45 Ca, 63 Ni, 147 Pm, and 151 Sm we have calculated the shape of the spectrum of shakeup electrons and the integrated probability of autoionization of the K shell. It was found that the contribution of the direct mechanism in all cases considered is significant

  10. Wavefunction effects in inner shell ionization of light atoms by protons

    International Nuclear Information System (INIS)

    Aashamar, K.; Amundsen, P.A.

    An efficient computer code for calculating the impact parameter distribution of atomic ionization probabilities caused by charged particle impact, has been developed. The programme is based on the semiclassical approximation, and it allows the use of an arbitrary atomic central potential for deriving the one-electron orbitals that form the basis for the description of the atomic states. Extensive calculations are reported for proton induced K-shell ionization in carbon and neon, covering energies in the range 0.1-10 MeV. Some calculations on proton-argon L-shell ionization are also reported. Comparison of the results obtained using (screened) hydrogenic potentials and the recently reported energy- optimized effective atomic central potentials, respectively demonstrates that wavefunction effects are generally important for inner-shell ionization of light atoms. The agreement between theory and experiment in the K-shell case is improved for fast collisions upon using better wavefunctions. (Auth.)

  11. Study of inter sub-shell and inter shell electron correlations in 4d open-shell heavy atomic ions

    International Nuclear Information System (INIS)

    Koike, Fumihiro

    2009-01-01

    The effect of correlations between 4p, 4d, and 4f has been studied extensively. The characteristic spectral structures of 4p - 4d and 4d - 4f optical transitions, due to the unique structures of N = 4 open sub-shells in heavy atomic ions, have been studied theoretically. To gain an insight of this effect, a series of careful MCDF calculations for 4d q (q = 0 to 10) atomic ions with atomic numbers Z = 48 to 56 has been carried out. The difference of orbital energy differences between 4p and 4d orbitals and 4d and 4f orbitals coincidently falls within the range of a few % for almost all the atomic ions investigated. The 4p 6 4d4f and 4p 5 4d 3 configurations may mix strongly, and the optical 4p - 4d and 4d - 4f transitions may take place coherently, providing us with quite a peculiar EUV emission spectrum. The effect of spectral narrowing and shift is expected to be quite common to the atomic specieds with the atomic numbers in the range Z = 48 to 56.

  12. The K-shell ionisation of atoms by relativistic protons

    International Nuclear Information System (INIS)

    Davidovic, D.M.; Moiseiwitsch, B.L.; Norrington, P.H.

    1978-01-01

    The K-shell ionisation of atoms by protons travelling with relativistic velocities is investigated using an extension of the first-order time-dependent perturbation-theory treatment of Moeller (Ann. Phys. Lpz.; 14:531 (1932)), taking Dirac plane waves for the description of the incident and scattered protons and the Darwin approximation for the relativistic wavefunctions of the K-shell atomic electrons and the ejected electron. The differential cross sections and total cross sections are calculated. Results are compared with those of earlier workers. (author)

  13. Ionization of inner shells of atoms taking account of outer shell rearrangement

    International Nuclear Information System (INIS)

    Amusia, M.Ya.

    1977-01-01

    The application of the general many-body theory and methods formulated with its help, in particular, the so-called random phase approximation with exchange (RPAE) and the many-body perturbation theory (MBPT) makes possible a description of ionization processes for many outer and intermediate shells of a number of atoms. This investigation of outer- and intermediate-shell ionization by photons and electrons demonstrates the collective character of these processes and the possibility of describing them by RPAE. 28 references

  14. Ionization effects in electronic inner-shells of ionized atoms

    International Nuclear Information System (INIS)

    Shchornak, G.

    1983-01-01

    A review of the atomic physics of ionization atoms has been presented. Interaction and structure effects in atomic shells, correlated to the occurrence of vacancies in several subshells of the atom have been considered. The methods of calculations of atomic states and wave functions have been reviewed. The energy shift of characteristic X-rays is discussed as a function of the ionization stage of the atom. The influence of inner and outer-shell vacancies on the energy of the X-rays is shown in detail. The influence of chemical effects on the parameters of X-rays is also taken into account. Further on, the change of transition probabilities in radiative and non-radiative transitions by changing stage of ionization is discussed; and among them the leading part of Auger and Coster-Kronig transitions by the arearrangement of the atomic states is shown. The influence of non-radiative electronic transitions on ionization cross-sections for multiple ionization is discussed. Using these results, ionization cross-sections for direct and indirect processes for several ionization stages are given

  15. Atomic mass formula with linear shell terms

    International Nuclear Information System (INIS)

    Uno, Masahiro; Yamada, Masami; Ando, Yoshihira; Tachibana, Takahiro.

    1981-01-01

    An atomic mass formula is constructed in the form of a sum of gross terms and empirical linear shell terms. Values of the shell parameters are determined after the statistical method of Uno and Yamada, Which is characterized by inclusion of the error inherent in the mass formula. The resulting formula reproduces the input masses with the standard deviation of 393 keV. A prescription is given for estimating errors of calculated masses. The mass formula is compared with recent experimental data of Rb, Cs and Fr isotopes, which are not included in the input data, and also with the constant-shell-term formula of Uno and Yamada. (author)

  16. Internal conversion theory of gamma radiation in unfilled atomic shells

    International Nuclear Information System (INIS)

    Anderson, Eh.M.; Trusov, V.F.; Ehglajs, M.O.

    1980-01-01

    The internal conversion theory of gamma radiation in unfilled shells, when the atom is in a state with certain energy and momentum, is considered. A formula for the conversion coefficient between the atom and ion levels is obtained. This coefficient turns to be dependent on genealogic characteristics of the atom. It is discussed when the conversion coefficients are proportional to the numbers of filling subshells in the atom. Exact calculations have been carried out in the multiconfigurational approximation taking into account intermediate coupling for the d-shell of the Fe atom Single-electron radial wave functions have been calculated on the basis of the relativistic method of the Hartree-Fock-Dirak self-consistent field. Conversion coefficients on certain subshells as well as submatrix elements of the production operator are calculated. The electric coefficient of internal conversion (CIC) in the calculation for one electron does not depend on spin orientation. That is why the electric CIC from the level will not depend on filling number distribution by subshells. For magnetic CIC the dependence on the atom state is significant. Using multiconfiguration basis for calculating energy matrix and its succeeding diagonalization means the account of the intermediate coupling type, which takes place for the unfilled shells

  17. Inner shells as a link between atomic and nuclear physics

    International Nuclear Information System (INIS)

    Merzbacher, E.

    1982-01-01

    Nuclear decay and reaction processes generally take place in neutral or partially ionized atoms. The effects of static nuclear properties (size, shape, moments) on atomic spectra are well known, as are electronic transitions accompanying nuclear transitions, e.g. K capture and internal conversion. Excitation or ionization of initially filled inner shells, really or virtually, may modify nuclear Q values, will require correction to measured beta-decay endpoint energies, and can permit the use of inner-shell transitions in the determination of nuclear widths. Improvements in resolution continue to enhance the importance of these effects. There is also beginning to appear experimental evidence of the dynamical effects of atomic electrons on the course of nuclear reactions. The dynamics of a nuclear reaction, which influences and may in turn be influenced by atomic electrons in inner shells, offers instructive examples of the interplay between strong and electromagnetic interactions and raises interesting questions about coherence properties of particle beams. A variety of significantly different collision regimes, depending on the atomic numbers of the collision partners and the collision velocity, will be discussed and illustrated. 21 References, 5 figures

  18. Inner-shell photoionization of group-IIB atoms

    International Nuclear Information System (INIS)

    Kutzner, M.; Tidwell, C.; Vance, S.E.; Radojevic, V.

    1994-01-01

    Total and partial photoionization cross sections, branching ratios, and angular-distribution asymmetry parameters for inner subshells (nl,l≥2) of the group-IIB elements zinc, cadmium, and mercury have been calculated in both the relativistic random-phase approximation and the relativistic random-phase approximation modified to include relaxation. Comparisons are made between the results of the two theoretical methods and with experiment where available. The present theoretical results for the 3d inner-shell photoionization of zinc are not in accord with experiment. We confirm previous work [S. L. Carter and H. P. Kelly, J. Phys. B 11, 2467 (1978)] which demonstrated that relaxation is an important effect in photoionization of the 4d subshell of atomic cadmium. It is also found that the inclusion of relaxation effects resolves a discrepancy between theory and experiment for the 4f inner-shell photoionization of atomic mercury

  19. Multislice theory of fast electron scattering incorporating atomic inner-shell ionization

    International Nuclear Information System (INIS)

    Dwyer, C.

    2005-01-01

    It is demonstrated how atomic inner-shell ionization can be incorporated into a multislice theory of fast electron scattering. The resulting theory therefore accounts for both inelastic scattering due to inner-shell ionization and dynamical elastic scattering. The theory uses a description of the ionization process based on the angular momentum representation for both the initial and final states of the atomic electron. For energy losses near threshold, only a small number of independent states of the ejected atomic electron need to be considered, reducing demands on computing time, and eliminating the need for tabulated inelastic scattering factors. The theory is used to investigate the influence of the collection aperture size on the spatial origin of the silicon K-shell EELS signal generated by a STEM probe. The validity of a so-called local approximation is also considered

  20. NiCo_2O_4@TiN Core-shell Electrodes through Conformal Atomic Layer Deposition for All-solid-state Supercapacitors

    International Nuclear Information System (INIS)

    Wang, Ruiqi; Xia, Chuan; Wei, Nini; Alshareef, Husam N.

    2016-01-01

    Highlights: • NiCo_2O_4 nanostructures are prepared via a simple hydrothermal method. • Outer shell of TiN is then grown through conformal atomic layer deposition. • Electrodes exhibit significantly enhanced rate capability with TiN coating. • Solid-state polymer electrolyte is employed to improve cycling stability. • Full devices show a stack power density of 58.205 mW cm"−"3 at 0.061 mWh cm"−"3. - Abstract: Ternary transition metal oxides such as NiCo_2O_4 show great potential as supercapacitor electrode materials. However, the unsatisfactory rate performance of NiCo_2O_4 may prove to be a major hurdle to its commercial usage. Herein, we report the development of NiCo_2O_4@TiN core–shell nanostructures for all-solid-state supercapacitors with significantly enhanced rate capability. We demonstrate that a thin layer of TiN conformally grown by atomic layer deposition (ALD) on NiCo_2O_4 nanofiber arrays plays a key role in improving their electrical conductivity, mechanical stability, and rate performance. Fabricated using the hybrid NiCo_2O_4@TiN electrodes, the symmetric all-solid-state supercapacitor exhibited an impressive stack power density of 58.205 mW cm"−"3 at a stack energy density of 0.061 mWh cm"−"3. To the best of our knowledge, these values are the highest of any NiCo_2O_4-based all-solid-state supercapacitor reported. Additionally, the resulting NiCo_2O_4@TiN all-solid-state device displayed outstanding cycling stability by retaining 70% of its original capacitance after 20,000 cycles at a high current density of 10 mA cm"−"2. These results illustrate the promise of ALD-assisted hybrid NiCo_2O_4@TiN electrodes within sustainable and integrated energy storage applications.

  1. Simultaneous K plus L shell ionized atoms during heavy-ion ...

    Indian Academy of Sciences (India)

    The fraction of simultaneous K plus L shell ionized atoms is estimated in Fe, Co and Cu elements using carbon ions at different projectile energies. The present results indicate that the fraction of simultaneous K plus L shell ionization probability decreases with increase in projectile energy as well as with increase in the ...

  2. On the atomic shell structure calculation (1)

    International Nuclear Information System (INIS)

    Choe Sun Chol

    1986-01-01

    We have considered the problem of atomic shell structure calculation using operator technique. We introduce reduced matrix elements of annihilation operators according to eg. (4). The normalized basis function is denoted as || ...>. The reduced matrix elements of the pair annihilation operators are expressed throw one-electron matrix elements. Some numerical results are represented and the problem of sign assignment is discussed. (author)

  3. Ultrafast atomic process in X-ray emission by using inner-shell ionization method for sodium and carbon atoms

    Energy Technology Data Exchange (ETDEWEB)

    Moribayashi, Kengo; Sasaki, Akira; Tajima, Toshiki [Japan Atomic Energy Research Inst., Neyagawa, Osaka (Japan). Kansai Research Establishment

    1998-07-01

    An ultrafast inner-shell ionization process with X-ray emission stimulated by high-intensity short-pulse X-ray is studied. Carbon and sodium atoms are treated as target matter. It is shown that atomic processes of the target determine the necessary X-ray intensity for X-ray laser emission as well as the features of X-ray laser such as wavelength and duration time. The intensity also depends on the density of initial atoms. Furthermore, we show that as the intensity of X-ray source becomes high, the multi-inner-shell ionization predominates, leading to the formation of hollow atoms. As the density of hollow atoms is increased by the pumping X-ray power, the emission of X-rays is not only of significance for high brightness X-ray measurement but also is good for X-ray lasing. New classes of experiments of pump X-ray probe and X-ray laser are suggested. (author)

  4. UV-assisted room temperature gas sensing of GaN-core/ZnO-shell nanowires

    International Nuclear Information System (INIS)

    Park, Sunghoon; Ko, Hyunsung; Kim, Soohyun; Lee, Chongmu

    2014-01-01

    GaN is highly sensitive to low concentrations of H 2 in ambient air and is almost insensitive to most other common gases. However, enhancing the sensing performance and the detection limit of GaN is a challenge. This study examined the H 2 -gas-sensing properties of GaN nanowires encapsulated with ZnO. GaN-core/ZnO-shell nanowires were fabricated by using a two-step process comprising the thermal evaporation of GaN powders and the atomic layer deposition of ZnO. The core-shell nanowires ranged from 80 to 120 nm in diameter and from a few tens to a few hundreds of micrometers in length, with a mean shell layer thickness of ∼8 nm. Multiple-networked pristine GaN nanowire and ZnO-encapsulated GaN (or GaN-core/ZnO-shell) nanowire sensors showed responses of 120 - 147% and 179 - 389%, respectively, to 500 - 2,500 ppm of H 2 at room temperature under UV (254 nm) illumination. The underlying mechanism of the enhanced response of the GaN nanowire to H 2 gas when using ZnO encapsulation and UV irradiation is discussed.

  5. Calculation of Ion Charge State Distributions After Inner-Shell Ionization in Xe Atom

    International Nuclear Information System (INIS)

    Mohammedein, A.M.; Ghoneim, A.A.; Kandil, M.K.; Kadad, I.M.

    2009-01-01

    The vacancy cascades following initial inner-shell vacancies in single and multi-ionized atoms often lead to highly charged residual ions. The inner-shell vacancy produced by ionization processes may decay by either a radiative or non-radiative transition. In addition to the vacancy filling processes, there is an electron shake off process due to the change of core potential of the atom. In the calculation of vacancy cascades, the radiative (x-ray) and non-radiative (Auger and Coster-Kronig) branching ratios give valuable information on the de-excitation dynamics of an atom with inner-shell vacancy. The production of multi-charged ions yield by the Auger cascades following inner shell ionization of an atom has been studied both experimentally and theoretically. Multi-charged Xe ions following de-excitation of K, L 1 , L 2,3 , M 1 , M 2,3 and M 4,5 subshell vacancies are calculated using Monte-Carlo algorithm to simulate the vacancy cascade development. Fluorescence yield (radiative) and Auger, Coster- Kronig yield (non- radiative) are evaluated. The decay of K hole state through radiative transitions is found to be more probable than non-radiative transitions in the first step of de-excitation. On the other hand, the decay of L, M vacancies through non-radiative transitions are more probable. The K shell ionization in Xe atom mainly yields Xe 7+ , Xe 8+ , Xe 9+ and Xe 1 0 + ions, and the charged X 8+ ions are the highest. The main product from the L 1 shell ionization is found to be Xe 8+ , Xe 9+ ions, while the charged Xe 8+ ions predominate at L 2,3 hole states. The charged Xe 6+ , Xe 7+ and Xe 8+ ions mainly yield from 3s 1/2 and 3p 1/2 , 3/2 ionization, while Xe in 3d 3/2 , 5/2 hole states mainly turns into Xe 4+ and Xe 5+ ions. The present results are found to agree well with the experimental data. (author)

  6. Quantitative measurement of solvation shells using frequency modulated atomic force microscopy

    Science.gov (United States)

    Uchihashi, T.; Higgins, M.; Nakayama, Y.; Sader, J. E.; Jarvis, S. P.

    2005-03-01

    The nanoscale specificity of interaction measurements and additional imaging capability of the atomic force microscope make it an ideal technique for measuring solvation shells in a variety of liquids next to a range of materials. Unfortunately, the widespread use of atomic force microscopy for the measurement of solvation shells has been limited by uncertainties over the dimensions, composition and durability of the tip during the measurements, and problems associated with quantitative force calibration of the most sensitive dynamic measurement techniques. We address both these issues by the combined use of carbon nanotube high aspect ratio probes and quantifying the highly sensitive frequency modulation (FM) detection technique using a recently developed analytical method. Due to the excellent reproducibility of the measurement technique, additional information regarding solvation shell size as a function of proximity to the surface has been obtained for two very different liquids. Further, it has been possible to identify differences between chemical and geometrical effects in the chosen systems.

  7. Deposition of conductive TiN shells on SiO2 nanoparticles with a fluidized bed ALD reactor

    NARCIS (Netherlands)

    Didden, A.; Hillebrand, P.; Wollgarten, M.; Dam, B.; Van de Krol, R.

    2016-01-01

    Conductive TiN shells have been deposited on SiO2 nanoparticles (10–20 nm primary particle size) with fluidized bed atomic layer deposition using TDMAT and NH3 as precursors. Analysis of the powders confirms that shell growth saturates at approximately 0.4 nm/cycle at TDMAT doses of >1.2 mmol/g of

  8. Generalized oscillator strengths for some higher valence-shell excitations of krypton atom

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The valence-shell excitations of krypton atom have been investigated by fast electron impact with an angle-resolved electron-energy-loss spectrometer. The generalized oscillator strengths for some higher mixed valence-shell excitations in 4d, 4f, 5p, 5d, 6s, 6p, 7s ← 4p of krypton atom have been determined. Their profiles are discussed, and the generalized oscillator strengths for the electric monopole and quadrupole excitations in 5p ← 4p are compared with the calculations of Amusia et al. (Phys. Rev. A 67 022703 (2003)). The differences between the experimental results and theoretical calculations show that more studies are needed.

  9. Two-photon decay of K-shell vacancy states in heavy atoms

    International Nuclear Information System (INIS)

    Ilakovac, K.; Uroic, M.; Majer, M.; Pasic, S.; Vukovic, B.

    2006-01-01

    Two-photon decay has been extensively studied in atomic, nuclear and particle physics since the 1930s when the problem of stability of the 2s state of the hydrogen atom emerged. Since then, many theoretical and experimental investigations have been made on hydrogen and one-electron (H-like) ions and on helium and two-electron (He-like) ions. The work on two-photon decay in many-electron systems involving inner shells started about 30 years ago and, in the meantime, two-photon decay of the K-shell vacancy state has been the subject of many theoretical and experimental studies. Experimental results have been obtained for 2s->1s and higher-state electron ->1s two-photon transitions in molybdenum, and for 2s -> 1s, 3s -> 1s, 3d -> 1s and 4sd -> 1s two-photon transitions in silver, xenon, hafnium and mercury. Nonrelativistic and relativistic calculations of the processes have been made. The relativistic calculations for transitions in molybdenum, silver and xenon atoms are in a reasonable agreement with the experimental results, but some problems remain to be solved. A review of investigations of two-photon transitions in atomic systems is presented

  10. Atomic mass prediction from the mass formula with empirical shell terms

    International Nuclear Information System (INIS)

    Uno, Masahiro; Yamada, Masami

    1982-08-01

    The mass-excess prediction of about 8000 nuclides was calculated from two types of the atomic mass formulas with empirical shell terms of Uno and Yamada. The theoretical errors to accompany the calculated mass excess are also presented. These errors have been obtained by a new statistical method. The mass-excess prediction includes the term of the gross feature of a nuclear mass surface, the shell terms and a small correction term for odd-odd nuclei. Two functional forms for the shell terms were used. The first is the constant form, and the sencond is the linear form. In determining the values of shell parameters, only the data of even-even and odd-A nuclei were used. A new statistical method was applied, in which the error inherent to the mass formula was taken account. The obtained shell parameters and the values of mass excess are shown in tables. (Kato, T.)

  11. 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.

  12. 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

  13. Notes from the Nordic Spring Symposium on atomic inner shell phenomena

    International Nuclear Information System (INIS)

    Hansteen, J.M.; Gundersen, R.

    1978-01-01

    The purpose of the symposium was to bring together scientists from those various fields of physics that involve atomic inner shell processes. Vol. 2 contains the submitted complete lecture notes in chronological order. (JIW)

  14. Impact parameter sensitive study of inner-shell atomic processes in the experimental storage ring

    Science.gov (United States)

    Gumberidze, A.; Kozhuharov, C.; Zhang, R. T.; Trotsenko, S.; Kozhedub, Y. S.; DuBois, R. D.; Beyer, H. F.; Blumenhagen, K.-H.; Brandau, C.; Bräuning-Demian, A.; Chen, W.; Forstner, O.; Gao, B.; Gassner, T.; Grisenti, R. E.; Hagmann, S.; Hillenbrand, P.-M.; Indelicato, P.; Kumar, A.; Lestinsky, M.; Litvinov, Yu. A.; Petridis, N.; Schury, D.; Spillmann, U.; Trageser, C.; Trassinelli, M.; Tu, X.; Stöhlker, Th.

    2017-10-01

    In this work, we present a pilot experiment in the experimental storage ring (ESR) at GSI devoted to impact parameter sensitive studies of inner shell atomic processes for low-energy (heavy-) ion-atom collisions. The experiment was performed with bare and He-like xenon ions (Xe54+, Xe52+) colliding with neutral xenon gas atoms, resulting in a symmetric collision system. This choice of the projectile charge states was made in order to compare the effect of a filled K-shell with the empty one. The projectile and target X-rays have been measured at different observation angles for all impact parameters as well as for the impact parameter range of ∼35-70 fm.

  15. Wigner’s phase-space function and atomic structure: II. Ground states for closed-shell atoms

    DEFF Research Database (Denmark)

    Springborg, Michael; Dahl, Jens Peder

    1987-01-01

    We present formulas for reduced Wigner phase-space functions for atoms, with an emphasis on the first-order spinless Wigner function. This function can be written as the sum of separate contributions from single orbitals (the natural orbitals). This allows a detailed study of the function. Here we...... display and analyze the function for the closed-shell atoms helium, beryllium, neon, argon, and zinc in the Hartree-Fock approximation. The quantum-mechanical exact results are compared with those obtained with the approximate Thomas-Fermi description of electron densities in phase space....

  16. The L1-shell ionisation of atoms by relativistic particles

    International Nuclear Information System (INIS)

    Moiseiwitsch, B.L.; Norrington, P.H.

    1979-01-01

    An expression for the L 1 -shell ionisation cross sections of atoms by high-energy particles has been derived using the relativistic plane-wave Born approximation. The incident and scattered particles are described by Dirac plane waves while Darwin hydrogenic wavefunctions are used for the atomic electrons. A comparison is made with experimental total cross sections for incident electrons in the energy range 1-2 MeV. The agreement is a considerable improvement on that obtained using the non-relativistic planewave Born approximation. (author)

  17. Structure, energetic and phase transition of multi shell icosahedral bimetallic nanostructures: A molecular dynamics study of NimPdn (n + m = 55 and 147)

    International Nuclear Information System (INIS)

    Hewage, Jinasena W.

    2015-01-01

    Structure, energetic and thermodynamic properties of multi shell icosahedral bimetallic nickel–palladium nanostructures with the size of 55 and 147 atoms were studied by using the molecular dynamics simulations and the microcanonical ensemble version of multiple histogram method. In 55 atoms icosahedra, two core–shell motifs, Ni 13 Pd 42 and Pd 13 Ni 42 with their isomers Pd 13 (Pd 29 Ni 13 ) and Ni 13 (Ni 29 Pd 13 ) were considered. Similarly in 147 atoms icosahedra, all mutations corresponding to the occupations of either nickel atoms or palladium atoms in the core, inner shell or outer shell and their isomers generated by interchanging thirteen core atoms with thirteen atoms of the other type in the inner and outer shells were considered. It is found that the nickel-core clusters are more stable than the palladium-core clusters and cohesive energy increases with the nickel composition. Phase transition of each cluster was studied by means of constant volume heat capacity. The trend in variation of melting temperature is opposite to the energy trend and special increase in melting points was observed for nickel-core isomers compared to the palladium-core isomers. Helmholtz free energy change with temperature for shell to core interchange of thirteen atoms revealed the thermodynamic stability of the formation of Ni core Pd shell structures and the surface segregation of palladium. - Highlights: • Nanostructures of Ni m Pd n clusters for m + n = 55 and 147 have been studied. • Structures favor the formation of nickel-core surrounded by palladium atoms. • In general, it appears the increase of cohesive energy with the nickel composition. • Calculated thermodynamic parameters confirm the energetic results. • Results show also the palladium segregation on the surface

  18. Epitaxial TiO 2/SnO 2 core-shell heterostructure by atomic layer deposition

    KAUST Repository

    Nie, Anmin

    2012-01-01

    Taking TiO 2/SnO 2 core-shell nanowires (NWs) as a model system, we systematically investigate the structure and the morphological evolution of this heterostructure synthesized by atomic layer deposition/epitaxy (ALD/ALE). All characterizations, by X-ray diffraction, high-resolution transmission electron microscopy, selected area electron diffraction and Raman spectra, reveal that single crystalline rutile TiO 2 shells can be epitaxially grown on SnO 2 NWs with an atomically sharp interface at low temperature (250 °C). The growth behavior of the TiO 2 shells highly depends on the surface orientations and the geometrical shape of the core SnO 2 NW cross-section. Atomically smooth surfaces are found for growth on the {110} surface. Rough surfaces develop on {100} surfaces due to (100) - (1 × 3) reconstruction, by introducing steps in the [010] direction as a continuation of {110} facets. Lattice mismatch induces superlattice structures in the TiO 2 shell and misfit dislocations along the interface. Conformal epitaxial growth has been observed for SnO 2 NW cores with an octagonal cross-section ({100} and {110} surfaces). However, for a rectangular core ({101} and {010} surfaces), the shell also derives an octagonal shape from the epitaxial growth, which was explained by a proposed model based on ALD kinetics. The surface steps and defects induced by the lattice mismatch likely lead to improved photoluminescence (PL) performance for the yellow emission. Compared to the pure SnO 2 NWs, the PL spectrum of the core-shell nanostructures exhibits a stronger emission peak, which suggests potential applications in optoelectronics. © The Royal Society of Chemistry 2012.

  19. Four shells atomic model to computer the counting efficiency of electron-capture nuclides

    International Nuclear Information System (INIS)

    Grau Malonda, A.; Fernandez Martinez, A.

    1985-01-01

    The present paper develops a four-shells atomic model in order to obtain the efficiency of detection in liquid scintillation courting, Mathematical expressions are given to calculate the probabilities of the 229 different atomic rearrangements so as the corresponding effective energies. This new model will permit the study of the influence of the different parameters upon the counting efficiency for nuclides of high atomic number. (Author) 7 refs

  20. On-shell diagrams for N=8 supergravity amplitudes

    Energy Technology Data Exchange (ETDEWEB)

    Heslop, Paul; Lipstein, Arthur E. [Department of Mathematical Sciences, Durham University,Lower Mountjoy, Stockton Road, Durham, DH1 3LE (United Kingdom)

    2016-06-10

    We define recursion relations for N=8 supergravity amplitudes using a generalization of the on-shell diagrams developed for planar N=4 super-Yang-Mills. Although the recursion relations generically give rise to non-planar on-shell diagrams, we show that at tree-level the recursion can be chosen to yield only planar diagrams, the same diagrams occurring in the planar N=4 theory. This implies non-trivial identities for non-planar diagrams as well as interesting relations between the N=4 and N=8 theories. We show that the on-shell diagrams of N=8 supergravity obey equivalence relations analogous to those of N=4 super-Yang-Mills, and we develop a systematic algorithm for reading off Grassmannian integral formulae directly from the on-shell diagrams. We also show that the 1-loop 4-point amplitude of N=8 supergravity can be obtained from on-shell diagrams.

  1. High-resolution inner-shell spectroscopies of free atoms and molecules using soft-x-ray beamlines at the third-generation synchrotron radiation sources

    International Nuclear Information System (INIS)

    Ueda, Kiyoshi

    2003-01-01

    This article reviews the current status of inner-shell spectroscopies of free atoms and molecules using high-resolution soft-x-ray monochromators installed in the soft-x-ray beamlines at the third-generation synchrotron radiation facilities. Beamlines and endstations devoted to atomic and molecular inner-shell spectroscopies and various types of experimental techniques, such as ion yield spectroscopy, resonant photoemission spectroscopy and multiple-coincidence momentum imaging, are described. Experimental results for K-shell excitation of Ne, O K-shell excitation of H 2 O and CO 2 , C K-shell excitation and ionization of CO 2 and B K-shell excitation of BF 3 , obtained at beamline 27SU of SPring-8 in Japan, are discussed as examples of atomic and molecular inner-shell spectroscopies using the third-generation synchrotron radiation sources. (topical review)

  2. Atomic ionization at positron-electron annihilation at β+-decay

    International Nuclear Information System (INIS)

    Fedotkin, S.N.

    2012-01-01

    The role of the nuclear charge screening and corrections to the Born approximation for the flying from atom electron in a process of atomic ionization at annihilation of positron with another electron of daughter's atom at β + - decay is studied. It was considered the processes of ionization of different atomic shells (n = 1, 2, 3, 4) at annihilation of positron, emitted at β'+ - decay with K- electron of daughter's atom. It is shown that the screening effect is important only for shell with n = 4. While corrections to the Born approximation plays the essential role for all shells. It is shown that the most probable process is related with emission of the another K- electron

  3. Investigation of the structure change of atomic shells due to uranium ionization by the Dirac-Fock-Slater method

    International Nuclear Information System (INIS)

    Shchornak, G.

    1979-01-01

    The influence of outer vacancies in the atomic shells of uranium on the atomic shell structure is claculated by the Dirac-Fock-Slater method. It is found out that the energy of the X-ray transitions increases due to the detachment of the electrons with the lowest binding energies. The electron detachment from the subshells of the 4f level gives rise to negative energy shifts of the X-ray transitions.(author)

  4. Realistic Gamow shell model for resonance and continuum in atomic nuclei

    Science.gov (United States)

    Xu, F. R.; Sun, Z. H.; Wu, Q.; Hu, B. S.; Dai, S. J.

    2018-02-01

    The Gamow shell model can describe resonance and continuum for atomic nuclei. The model is established in the complex-moment (complex-k) plane of the Berggren coordinates in which bound, resonant and continuum states are treated on equal footing self-consistently. In the present work, the realistic nuclear force, CD Bonn, has been used. We have developed the full \\hat{Q}-box folded-diagram method to derive the realistic effective interaction in the model space which is nondegenerate and contains resonance and continuum channels. The CD-Bonn potential is renormalized using the V low-k method. With choosing 16O as the inert core, we have applied the Gamow shell model to oxygen isotopes.

  5. Prediction of mass excess, β-decay energy and neutron separation energy from the atomic mass formula with empirical shell terms

    International Nuclear Information System (INIS)

    Ando, Yoshihira; Uno, Masahiro; Yamada, Masami

    1983-02-01

    Recently we proposed two types of atomic mass formula (constant-shell-term formula, linear-shell-term formula). With use of these formulas, we calculate and tabulate mass excesses, neutron separation energies, and β-decay energies (β-decay and/or electron capture) for about 5000 nuclides. The mass excess values and their errors in the 1977 atomic mass evaluation by A.H. Wapstra and K. Bos which we used in constructing our formulas, are also tabulated for reference. The constant-shell-term formula is fitted to 1468 input mass data with the standard deviation of 626 keV and the linear-shell-term formula with 394 keV

  6. Prediction of mass excess, #betta#-decay energy and neutron separation energy from the atomic mass formula with empirical shell terms

    International Nuclear Information System (INIS)

    Ando, Yoshihira; Uno, Masahiro; Yamada, Masami.

    1983-02-01

    Recently we proposed two types of atomic mass formula (constant-shell-term formula, linear-shell-term formula). With use of these formulas, we calculate and tabulate mass excesses, neutron separation energies, and #betta#-decay energies (#betta# - -decay and/or electron capture) for about 5000 nuclides. The mass excess values and their errors in the 1977 atomic mass evaluation by A.H. Wapstra and K. Bos which we used in constructing our formulas, are also tabulated for reference. The constant-shell-term formula is fitted to 1468 input mass data with the standard deviation of 626 keV and the linear-shell-term formula with 394 keV. (author)

  7. NiCo2O4@TiN Core-shell Electrodes through Conformal Atomic Layer Deposition for All-solid-state Supercapacitors

    KAUST Repository

    Wang, Renqi

    2016-03-04

    Ternary transition metal oxides such as NiCo2O4 show great promise as supercapacitor electrode materials. However, the unsatisfactory rate performance of NiCo2O4 may prove to be a major hurdle to its commercial usage. Herein, we report the development of NiCo2O4@TiN core–shell nanostructures for all-solid-state supercapacitors with significantly enhanced rate capability. We demonstrate that a thin layer of TiN conformally grown by atomic layer deposition (ALD) on NiCo2O4 nanofiber arrays plays a key role in improving their electrical conductivity, mechanical stability, and rate performance. Fabricated using the hybrid NiCo2O4@TiN electrodes, the symmetric all-solid-state supercapacitor exhibited an impressive stack power density of 58.205 mW cm−3 at a stack energy density of 0.061 mWh cm−3. To the best of our knowledge, these values are the highest of any NiCo2O4-based all-solid-state supercapacitor reported. Additionally, the resulting NiCo2O4@TiN all-solid-state device displayed outstanding cycling stability by retaining 70% of its original capacitance after 20,000 cycles at a high current density of 10 mA cm−2. These results illustrate the promise of ALD-assisted hybrid NiCo2O4@TiN electrodes for sustainable and integrated energy storage applications.

  8. NiCo2O4@TiN Core-shell Electrodes through Conformal Atomic Layer Deposition for All-solid-state Supercapacitors

    KAUST Repository

    Wang, Renqi; Xia, Chuan; Wei, Nini; Alshareef, Husam N.

    2016-01-01

    Ternary transition metal oxides such as NiCo2O4 show great promise as supercapacitor electrode materials. However, the unsatisfactory rate performance of NiCo2O4 may prove to be a major hurdle to its commercial usage. Herein, we report the development of NiCo2O4@TiN core–shell nanostructures for all-solid-state supercapacitors with significantly enhanced rate capability. We demonstrate that a thin layer of TiN conformally grown by atomic layer deposition (ALD) on NiCo2O4 nanofiber arrays plays a key role in improving their electrical conductivity, mechanical stability, and rate performance. Fabricated using the hybrid NiCo2O4@TiN electrodes, the symmetric all-solid-state supercapacitor exhibited an impressive stack power density of 58.205 mW cm−3 at a stack energy density of 0.061 mWh cm−3. To the best of our knowledge, these values are the highest of any NiCo2O4-based all-solid-state supercapacitor reported. Additionally, the resulting NiCo2O4@TiN all-solid-state device displayed outstanding cycling stability by retaining 70% of its original capacitance after 20,000 cycles at a high current density of 10 mA cm−2. These results illustrate the promise of ALD-assisted hybrid NiCo2O4@TiN electrodes for sustainable and integrated energy storage applications.

  9. The role of fullerene shell upon stuffed atom polarization potential

    OpenAIRE

    Amusia, M. Ya.; Chernysheva, L. V.

    2015-01-01

    We have demonstrated that the polarization of the fullerene shell considerably alters the polarization potential of an atom, stuffed inside a fullerene. This essentially affects the electron elastic scattering phases as well as corresponding cross-sections. We illustrate the general trend by concrete examples of electron scattering by endohedrals of Neon and Argon. To obtain the presented results, we have suggested a simplified approach that permits to incorporate the effect of fullerenes pol...

  10. Photoionization of the outer electrons in noble gas endohedral atoms

    International Nuclear Information System (INIS)

    Amusia, M. Ya.; Baltenkov, A. S.; Chernysheva, L. V.

    2008-01-01

    We suggest a prominent modification of the outer shell photoionization cross section in noble gas (NG) endohedral atoms NG-C n under the action of the electron shell of fullerene C n . This shell leads to two important effects: a strong enhancement of the cross section due to fullerene shell polarization under the action of the incoming electromagnetic wave and to prominent oscillation of this cross section due to the reflection of a photoelectron from the NG by the fullerene shell. Both factors lead to powerful maxima in the outer shell ionization cross sections of NG-C n , which we call giant endohedral resonances. The oscillator strength reaches a very large value in the atomic scale, 25. We consider atoms of all noble gases except He. The polarization of the fullerene shell is expressed in terms of the total photoabsorption cross section of the fullerene. The photoelectron reflection is taken into account in the framework of the so-called bubble potential, which is a spherical δ-type potential. It is assumed in the derivations that the NG is centrally located in the fullerene. It is also assumed, in accordance with the existing experimental data, that the fullerene radius R C is much larger than the atomic radius r A and the thickness Δ C of the fullerene shell. As was demonstrated recently, these assumptions allow us to represent the NG-C n photoionization cross section as a product of the NG cross section and two well-defined calculated factors

  11. Ionic bonding of lanthanides, as influenced by d- and f-atomic orbitals, by core-shells and by relativity.

    Science.gov (United States)

    Ji, Wen-Xin; Xu, Wei; Schwarz, W H Eugen; Wang, Shu-Guang

    2015-03-15

    Lanthanide trihalide molecules LnX3 (X = F, Cl, Br, I) were quantum chemically investigated, in particular detail for Ln = Lu (lutetium). We applied density functional theory (DFT) at the nonrelativistic and scalar and SO-coupled relativistic levels, and also the ab initio coupled cluster approach. The chemically active electron shells of the lanthanide atoms comprise the 5d and 6s (and 6p) valence atomic orbitals (AO) and also the filled inner 4f semivalence and outer 5p semicore shells. Four different frozen-core approximations for Lu were compared: the (1s(2) -4d(10) ) [Pd] medium core, the [Pd+5s(2) 5p(6) = Xe] and [Pd+4f(14) ] large cores, and the [Pd+4f(14) +5s(2) 5p(6) ] very large core. The errors of LuX bonding are more serious on freezing the 5p(6) shell than the 4f(14) shell, more serious upon core-freezing than on the effective-core-potential approximation. The LnX distances correlate linearly with the AO radii of the ionic outer shells, Ln(3+) -5p(6) and X(-) -np(6) , characteristic for dominantly ionic Ln(3+) -X(-) binding. The heavier halogen atoms also bind covalently with the Ln-5d shell. Scalar relativistic effects contract and destabilize the LuX bonds, spin orbit coupling hardly affects the geometries but the bond energies, owing to SO effects in the free atoms. The relativistic changes of bond energy BE, bond length Re , bond force k, and bond stretching frequency vs do not follow the simple rules of Badger and Gordy (Re ∼BE∼k∼vs ). The so-called degeneracy-driven covalence, meaning strong mixing of accidentally near-degenerate, nearly nonoverlapping AOs without BE contribution is critically discussed. © 2015 Wiley Periodicals, Inc.

  12. Signatures of shell evolution in alpha decay across the N = 126 shell closure

    Science.gov (United States)

    Rui-Wang; Wang, Rui-Yao; Qian, Yi-Bin; Ren, Zhong-Zhou

    2017-06-01

    Within the alpha-cluster model, we particularly investigate the alpha decay of exotic nuclei in the vicinity of the N = 126 neutron shell plus the Z = 82 proton shell. The systematics of alpha-preformation probability (P α ), as an indicator of the shell effect, is deduced from the ratio of the experimental decay width to the calculated one. Through the comparative analysis of the P α trend in the N = 124-130 isotonic chain, the N = 126 and Z = 82 shell closures are believed to strongly affect the formation of the alpha particle before its penetration. Additionally, the P α variety in Po and Rn isotopes is presented as another proof for such an influence. More importantly, it may be concluded that the expected neutron (or proton) shell effect gradually fades away along with the increasing valence proton (or neutron) number. The odd-even staggering presented in the P α value is also discussed. Supported by National Natural Science Foundation of China (11375086, 11535004, 11605089, 11120101005), Natural Science Youth Fund of Jiangsu Province (BK20150762), Fundamental Research Funds for the Central Universities (30916011339), 973 National Major State Basic Research and Development Program of China (2013CB834400), and a Project Funded by the Priority Academic Programme Development of JiangSu Higher Education Institutions (PAPD)

  13. Epitaxial TiO 2/SnO 2 core-shell heterostructure by atomic layer deposition

    KAUST Repository

    Nie, Anmin; Liu, Jiabin; Li, Qianqian; Cheng, Yingchun; Dong, Cezhou; Zhou, Wu; Wang, Pengfei; Wang, Qingxiao; Yang, Yang; Zhu, Yihan; Zeng, Yuewu; Wang, Hongtao

    2012-01-01

    Taking TiO 2/SnO 2 core-shell nanowires (NWs) as a model system, we systematically investigate the structure and the morphological evolution of this heterostructure synthesized by atomic layer deposition/epitaxy (ALD/ALE). All characterizations

  14. Computation of Ion Charge State Distributions After Inner-shell Ionization in Ne, Ar and Kr Atoms Using Monte Carlo Simulation

    International Nuclear Information System (INIS)

    Ahmed Ghoneim, Adel Aly; Ghoneim, Adel A.; Al-Zanki, Jasem M.; El-Essawy, Ashraf H.

    2009-01-01

    Atomic reorganization starts by filling the initially inner-shell vacancy by a radiative transition (x-ray) or by a non-radiative transition (Auger and Coster-Kronig processes). New vacancies created during this atomic reorganization may in turn be filled by further radiative and non-radiative transitions until all vacancies reach the outermost occupied shells. The production of inner-shell vacancy in an atom and the de-excitation decays through radiative and non-radiative transitions may result in a change of the atomic potential; this change leads to the emission of an additional electron in the continuum (electron shake-off processes). In the present work, the ion charge state distributions (CSD) and mean atomic charge ions produced from inner shell vacancy de-excitation decay are calculated for neutral Ne , Ar and Kr atoms. The calculations are carried out using Monte Carlo (MC) technique to simulate the cascade development after primary vacancy production. The radiative and non-radiative transitions for each vacancy are calculated in the simulation. In addition, the change of transition energies and transition rates due to multi vacancies produced in the atomic configurations through the cascade development are considered in the present work. It is found that considering the electron shake off process and closing of non-allowed non-radiative channels improves the results of both charge state distributions (CSD) and average charge state. To check the validity of the present calculations, the results obtained are compared with available theoretical and experimental data. The present results are found to agree well with the available theoretical and experimental values. (author)

  15. DFT study of Fe-Ni core-shell nanoparticles: Stability, catalytic activity, and interaction with carbon atom for single-walled carbon nanotube growth

    International Nuclear Information System (INIS)

    Yang, Zhimin; Wang, Qiang; Shan, Xiaoye; Zhu, Hongjun; Li, Wei-qi; Chen, Guang-hui

    2015-01-01

    Metal catalysts play an important role in the nucleation and growth of single-walled carbon nanotubes (SWCNTs). It is essential for probing the nucleation and growth mechanism of SWCNTs to fundamentally understand the properties of the metal catalysts and their interaction with carbon species. In this study, we systematically studied the stability of 13- and 55-atom Fe and Fe-Ni core-shell particles as well as these particles interaction with the carbon atoms using the density functional theory calculations. Icosahedral 13- and 55-atom Fe-Ni core-shell bimetallic particles have higher stability than the corresponding monometallic Fe and Ni particles. Opposite charge transfer (or distribution) in these particles leads to the Fe surface-shell displays a positive charge, while the Ni surface-shell exhibits a negative charge. The opposite charge transfer would induce different chemical activities. Compared with the monometallic Fe and Ni particles, the core-shell bimetallic particles have weaker interaction with C atoms. More importantly, C atoms only prefer staying on the surface of the bimetallic particles. In contrast, C atoms prefer locating into the subsurface of the monometallic particles, which is more likely to form stable metal carbides. The difference of the mono- and bimetallic particles on this issue may result in different nucleation and growth mechanism of SWCNTs. Our findings provide useful insights for the design of bimetallic catalysts and a better understanding nucleation and growth mechanism of SWCNTs

  16. Ultra fast atomic process in X-ray emission by inner-shell ionization

    Energy Technology Data Exchange (ETDEWEB)

    Moribayashi, Kengo; Sasaki, Akira [Japan Atomic Energy Research Inst., Neyagawa, Osaka (Japan). Kansai Research Establishment; Tajima, T

    1998-03-01

    An ultra-fast atomic process together with X-ray emission by inner-shell ionization using high intensity (10{sup 18} W/cm{sup 2}) short pulse (20fs) X-ray is studied. A new class of experiment is proposed and a useful pumping source is suggested. In this method, it is found that the gain value of X-ray laser amounts to larger than 1000(1/cm) with use of the density of 10{sup 22}/cm{sup 3} of carbon atom. Electron impact ionization effect and initial density effect as well as intensity of pumping source effect are also discussed. (author)

  17. Shell structure from N=Z (100Sn) to N>>Z (78Ni)

    International Nuclear Information System (INIS)

    Grawe, H.

    2003-01-01

    The shell structure of 100 Sn shows striking resemblance to 56 Ni one major shell below. Large-scale shell model calculations employing realistic interactions derived from effective NN potentials and allowing for up to 4p4h excitations of the 100 Sn core account very well for the spectroscopy of key neighbours 102,103 Sn, 98 Cd and 94 Ag, as inferred from level energies, isomerism, E2 strengths and Gamow-Teller (GT) decay of high-spin states. Recent β- decay studies of 101-104 Sn using the sulphurisation ISOL technique open the perspective to study the 100 Sn GT resonance. At N>>Z the persistence of the N=50 and the weakness of the N=40 shells are traced back to the monopole interaction in S=0 proton-neutron (πν) pairs of nucleons, a scenario which can be generalised to account for the new N=6,16(14),34(32) magicity in light neutron-rich nuclei. (orig.)

  18. Modification of calcite crystal growth by abalone shell proteins: an atomic force microscope study.

    OpenAIRE

    Walters, D A; Smith, B L; Belcher, A M; Paloczi, G T; Stucky, G D; Morse, D E; Hansma, P K

    1997-01-01

    A family of soluble proteins from the shell of Haliotis rufescens was introduced over a growing calcite crystal being scanned in situ by an atomic force microscope (AFM). Atomic step edges on the crystal surface were altered in shape and speed of growth by the proteins. Proteins attached nonuniformly to the surface, indicating different interactions with crystallographically different step edges. The observed changes were consistent with the habit modification induced by this family of protei...

  19. Computation of electron-impact K-shell ionization cross sections of atoms

    International Nuclear Information System (INIS)

    Uddin, M.A.; Haque, A.K.F.; Billah, M. Masum; Basak, A.K.; Karim, K.R.; Saha, B.C.

    2005-01-01

    The total cross sections of electron impact single K-shell ionization of atomic targets, with a wide range of atomic numbers from Z=6-50, are evaluated in the energy range up to about 10 MeV employing the recently proposed modified version of the improved binary-encounter dipole (RQIBED) model [Uddin et al., Phys. Rev. A 70, 032706 (2004)], which incorporates the ionic and relativistic effects. The experimental cross sections for all targets are reproduced satisfactorily even in the relativistic energies using fixed generic values of the two parameters in the RQIBED model. The relativistic effect is found to be significant in all targets except for C, being profound in Ag and Sn

  20. Correlated electron capture and inner-shell excitation measurements in ion-atom collisions

    International Nuclear Information System (INIS)

    Tanis, J.A.; Bernstein, E.M.; Clark, M.W.

    1985-01-01

    In an ion-atom collision projectile excitation and charge transfer (electron capture) may occur together in a single encounter. If the excitation and capture are correlated, then the process is called resonant transfer and excitation (RTE); if they are uncorrelated, then the process is termed nonresonant transfer and excitation (NTE). Experimental work to date has shown the existence of RTE and provided strong evidence for NTE. Results presented here provide information on the relative magnitudes of RTE and NTE, the charge state dependence of RTE, the effect of the target momentum distribution on RTE, the magnitude of L-shell RTE compared to K-shell RTE, and the target Z dependences of RTE and NTE. 15 refs., 5 figs

  1. Systematic study of shell effect near drip-lines

    International Nuclear Information System (INIS)

    Adhikari, S.; Samanta, C.

    2004-01-01

    The variation of nuclear shell effects with nucleon numbers is evaluated using the modified Bethe–Weizsaecker mass formula (BWM) and the measured atomic masses. The shell effects at magic neutron numbers N=8, 20, 28, 50, 82 and 126 and magic proton numbers Z=8, 20, 28, 50 and 82 are found to vary rapidly approaching the drip-lines. The shell effect due to one magic number increases on approaching another magic number. Thus, shell effects are not always negligible near the drip-lines. (author)

  2. Inner shell excitation in atoms and molecules by high resolution electron impact

    International Nuclear Information System (INIS)

    King, G.C.

    1986-01-01

    In this work an inner-shell spin-forbidden transition in N 2 and a parity-forbidden transition in Ar were studied. These transitions were observed by using incident electron energies as low as 1.15 times the excitation energy of the inner-shell states. (Auth.)

  3. Evaluating and interpreting the chemical relevance of the linear response kernel for atoms II: open shell.

    Science.gov (United States)

    Boisdenghien, Zino; Fias, Stijn; Van Alsenoy, Christian; De Proft, Frank; Geerlings, Paul

    2014-07-28

    Most of the work done on the linear response kernel χ(r,r') has focussed on its atom-atom condensed form χAB. Our previous work [Boisdenghien et al., J. Chem. Theory Comput., 2013, 9, 1007] was the first effort to truly focus on the non-condensed form of this function for closed (sub)shell atoms in a systematic fashion. In this work, we extend our method to the open shell case. To simplify the plotting of our results, we average our results to a symmetrical quantity χ(r,r'). This allows us to plot the linear response kernel for all elements up to and including argon and to investigate the periodicity throughout the first three rows in the periodic table and in the different representations of χ(r,r'). Within the context of Spin Polarized Conceptual Density Functional Theory, the first two-dimensional plots of spin polarized linear response functions are presented and commented on for some selected cases on the basis of the atomic ground state electronic configurations. Using the relation between the linear response kernel and the polarizability we compare the values of the polarizability tensor calculated using our method to high-level values.

  4. Enhanced thermoelectric transport in modulation-doped GaN/AlGaN core/shell nanowires.

    Science.gov (United States)

    Song, Erdong; Li, Qiming; Swartzentruber, Brian; Pan, Wei; Wang, George T; Martinez, Julio A

    2016-01-08

    The thermoelectric properties of unintentionally n-doped core GaN/AlGaN core/shell N-face nanowires are reported. We found that the temperature dependence of the electrical conductivity is consistent with thermally activated carriers with two distinctive donor energies. The Seebeck coefficient of GaN/AlGaN nanowires is more than twice as large as that for the GaN nanowires alone. However, an outer layer of GaN deposited onto the GaN/AlGaN core/shell nanowires decreases the Seebeck coefficient at room temperature, while the temperature dependence of the electrical conductivity remains the same. We attribute these observations to the formation of an electron gas channel within the heavily-doped GaN core of the GaN/AlGaN nanowires. The room-temperature thermoelectric power factor for the GaN/AlGaN nanowires can be four times higher than the GaN nanowires. Selective doping in bandgap engineered core/shell nanowires is proposed for enhancing the thermoelectric power.

  5. Zero-point energy of N perfectly conducting concentric cylindrical shells

    International Nuclear Information System (INIS)

    Tatur, K.; Woods, L.M.

    2008-01-01

    The zero-point (Casimir) energy of N perfectly conducting, infinitely long, concentric cylindrical shells is calculated utilizing the mode summation technique. The obtained convergent expression is studied as a function of size, curvature and number of shells. Limiting cases, such as infinitely close shells or infinite radius shells are also investigated

  6. Optical oscillator strengths of the valence-shell excitations of atoms and molecules determined by the dipole ( γ,γ) method

    Science.gov (United States)

    Xu, Long-Quan; Liu, Ya-Wei; Xu, Xin; Ni, Dong-Dong; Yang, Ke; Zhu, Lin-Fan

    2017-07-01

    The dipole (γ,γ) method, which is the inelastic X-ray scattering operated at a negligibly small momentum transfer, has been developed to determine the absolute optical oscillator strengths of the valence-shell excitations of atoms and molecules. This new method is free from the line saturation effect, and its Bethe-Born conversion factor varies much more slowly with the excitation energy than that of the dipole (e, e) method. Thus the dipole (γ,γ) method provides a reliable approach to obtain the benchmark optical oscillator strengths of the valence-shell excitations for gaseous atoms and molecules. In this paper, we give a review of the dipole (γ,γ) method and some recent measurements of absolute optical oscillator strengths of gaseous atoms and molecules. Contribution to the Topical Issue "Atomic and Molecular Data and their Applications", edited by Gordon W.F. Drake, Jung-Sik Yoon, Daiji Kato, Grzegorz Karwasz.

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

    International Nuclear Information System (INIS)

    Lindle, D.W.

    1983-12-01

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

  8. Closed-shell and open-shell square-planar iridium nitrido complexes

    Science.gov (United States)

    Scheibel, Markus G.; Askevold, Bjorn; Heinemann, Frank W.; Reijerse, Edward J.; de Bruin, Bas; Schneider, Sven

    2012-07-01

    Coupling reactions of nitrogen atoms represent elementary steps to many important heterogeneously catalysed reactions, such as the Haber-Bosch process or the selective catalytic reduction of NOx to give N2. For molecular nitrido (and related oxo) complexes, it is well established that the intrinsic reactivity, for example nucleophilicity or electrophilicity of the nitrido (or oxo) ligand, can be attributed to M-N (M-O) ground-state bonding. In recent years, nitrogen (oxygen)-centred radical reactivity was ascribed to the possible redox non-innocence of nitrido (oxo) ligands. However, unequivocal spectroscopic characterization of such transient nitridyl {M=N•} (or oxyl {M-O•}) complexes remained elusive. Here we describe the synthesis and characterization of the novel, closed-shell and open-shell square-planar iridium nitrido complexes [IrN(Lt-Bu)]+ and [IrN(Lt-Bu)] (Lt-Bu=N(CHCHP-t-Bu2)2). Spectroscopic characterization and quantum chemical calculations for [IrN(Lt-Bu)] indicate a considerable nitridyl, {Ir=N•}, radical character. The clean formation of IrI-N2 complexes via binuclear coupling is rationalized in terms of nitrido redox non-innocence in [IrN(Lt-Bu)].

  9. Micro-Raman investigations of InN-GaN core-shell nanowires on Si (111) substrate

    Science.gov (United States)

    Sangeetha, P.; Jeganathan, K.; Ramakrishnan, V.

    2013-06-01

    The electron-phonon interactions in InN-GaN core-shell nanowires grown by plasma assisted- molecular beam epitaxy (MBE) on Si (111) substrate have been analysed using micro-Raman spectroscopic technique with the excitation wavelength of 633, 488 and 325 nm. The Raman scattering at 633 nm reveals the characteristic E2 (high) and A1 (LO) phonon mode of InN core at 490 and 590 cm-1 respectively and E2 (high) phonon mode of GaN shell at 573 cm-1. The free carrier concentration of InN core is found to be low in the order ˜ 1016 cm-3 due to the screening of charge carriers by thin GaN shell. Diameter of InN core evaluated using the spatial correlation model is consistent with the transmission electron microscopic measurement of ˜15 nm. The phonon-life time of core-shell nanowire structure is estimated to be ˜0.4 ps. The micro-Raman mapping and its corresponding localised spectra for 325 nm excitation exhibit intense E2 (high) phonon mode of GaN shell at 573 cm-1 as the decrease of laser interaction length and the signal intensity is quenched at the voids due to high spacing of NWs.

  10. Micro-Raman investigations of InN-GaN core-shell nanowires on Si (111 substrate

    Directory of Open Access Journals (Sweden)

    P. Sangeetha

    2013-06-01

    Full Text Available The electron-phonon interactions in InN-GaN core-shell nanowires grown by plasma assisted- molecular beam epitaxy (MBE on Si (111 substrate have been analysed using micro-Raman spectroscopic technique with the excitation wavelength of 633, 488 and 325 nm. The Raman scattering at 633 nm reveals the characteristic E2 (high and A1 (LO phonon mode of InN core at 490 and 590 cm−1 respectively and E2 (high phonon mode of GaN shell at 573 cm−1. The free carrier concentration of InN core is found to be low in the order ∼ 1016 cm−3 due to the screening of charge carriers by thin GaN shell. Diameter of InN core evaluated using the spatial correlation model is consistent with the transmission electron microscopic measurement of ∼15 nm. The phonon-life time of core-shell nanowire structure is estimated to be ∼0.4 ps. The micro-Raman mapping and its corresponding localised spectra for 325 nm excitation exhibit intense E2 (high phonon mode of GaN shell at 573 cm−1 as the decrease of laser interaction length and the signal intensity is quenched at the voids due to high spacing of NWs.

  11. Micro-Raman investigations of InN-GaN core-shell nanowires on Si (111) substrate

    International Nuclear Information System (INIS)

    Sangeetha, P.; Ramakrishnan, V.; Jeganathan, K.

    2013-01-01

    The electron-phonon interactions in InN-GaN core-shell nanowires grown by plasma assisted- molecular beam epitaxy (MBE) on Si (111) substrate have been analysed using micro-Raman spectroscopic technique with the excitation wavelength of 633, 488 and 325 nm. The Raman scattering at 633 nm reveals the characteristic E 2 (high) and A 1 (LO) phonon mode of InN core at 490 and 590 cm −1 respectively and E 2 (high) phonon mode of GaN shell at 573 cm −1 . The free carrier concentration of InN core is found to be low in the order ∼ 10 16 cm −3 due to the screening of charge carriers by thin GaN shell. Diameter of InN core evaluated using the spatial correlation model is consistent with the transmission electron microscopic measurement of ∼15 nm. The phonon-life time of core-shell nanowire structure is estimated to be ∼0.4 ps. The micro-Raman mapping and its corresponding localised spectra for 325 nm excitation exhibit intense E 2 (high) phonon mode of GaN shell at 573 cm −1 as the decrease of laser interaction length and the signal intensity is quenched at the voids due to high spacing of NWs.

  12. Local functional derivative of the total energy and the shell structure in atoms and molecules

    NARCIS (Netherlands)

    Pino, R.; Markvoort, Albert. J.; Santen, van R.A.; Hilbers, P.A.J.

    2003-01-01

    The full and local Thomas–Fermi–Dirac energy functional derivatives are evaluated at Hartree–Fock densities for several atoms and molecules. These functions are interpreted as local chemical potentials and related mainly to kinetic energy functional derivatives. They are able to reveal the shell

  13. Collisional alignment and orientation of atomic outer shells. Pt. 1

    International Nuclear Information System (INIS)

    Andersen, N.; Gallagher, J.W.; Hertel, I.V.

    1988-01-01

    The study of polarization of atomic radiation emitted after impact excitation has yielded an enormous wealth of detailed information on the mechanism and dynamics of collisional excitation and energy transfer, both in electron and heavy particle impact studies. In these studies, the beam of electrons, ions or fast atoms used to excite the target atoms provides a suitable quantization axis with respect to which the polarization of the fluorescent light of the excited atoms is detected. From these data information on the cross sections for the different magnetic substates of the excited atom is extracted, imparting a great deal of insight into impact mechanisms for both outer and inner shell excitation. It is our aim to provide a comprehensive review including all data available in the literature presented in a standardized and easily accessible fashion. In this review we include only alignment and orientation studies, which have a well-defined planar symmetry, i.e., in which the initial and final relative momentum of the interacting particles are well defined by differential scattering techniques. We do not make a major distinction between heavy-particle and electron impact excitation: In fact, one of our aims is to demonstrate similarities between the two fields from a technical as well as from a conceptual point of view. The review is divided into three parts: This first part (I) deals with direct excitation of atoms by electrons and fast atoms or ions. Section 2 gives an introduction to the general concepts and ideas behind this kind of study and a description of typical experimental setups. Section 3 deals with electron impact excitation of atoms, starting with the simplest case of electron-helium collisions which may be fully described by two parameters, followed by more complex cases such as electron impact excitation of hydrogen and the heavy rare gases. Section 4 describes the results for direct excitation by atomic impact. (orig./AH)

  14. K-shell auger decay of atomic oxygen

    Energy Technology Data Exchange (ETDEWEB)

    Stolte, W.C.; Lu, Y.; Samson, J.A.R. [Univ. of Nebraska, Lincoln, NE (United States)] [and others

    1997-04-01

    The aim of the present research is to understand the interaction between the ejected photoelectron and Auger electron produced by the Auger decay of a 1s hole in atomic oxygen, and to understand the influence this interaction has on the shape of the ionization cross sections. To accomplish this the authors have measured the relative ion yields (ion/photon) in the vicinity of the oxygen K-shell (525 - 533 eV) for O{sup +} and O{sup 2+}. The measurements were performed at the ALS on beamline, 6.3.2. The atomic oxygen was produced by passing molecular oxygen through a microwave-driven discharge. A Rydberg analysis of the two series leading to the [1s]2s{sup 2}2p{sup 4}({sup 4}P) and [1s]2s{sup 2}2p{sup 4}({sup 2}P) limits were obtained. This analysis shows some differences to the recently published results by Menzel et al. The energy position of the main 1s{sup 1}2s{sup 2}2p{sup 5}({sup 3}P) resonance differs by approximately 1 eV from the authors value, all members of the ({sup 2}P)np series differ by 0.3 eV, but the members of the ({sup 4}P)np series agree. The molecular resonance at 530.5 eV and those between 539 eV and 543 eV, measured with the microwave discharge off show identical results in both experiments.

  15. Enhanced thermoelectric transport in modulation-doped GaN/AlGaN core/shell nanowires

    International Nuclear Information System (INIS)

    Song, Erdong; Martinez, Julio A; Li, Qiming; Pan, Wei; Wang, George T; Swartzentruber, Brian

    2016-01-01

    The thermoelectric properties of unintentionally n-doped core GaN/AlGaN core/shell N-face nanowires are reported. We found that the temperature dependence of the electrical conductivity is consistent with thermally activated carriers with two distinctive donor energies. The Seebeck coefficient of GaN/AlGaN nanowires is more than twice as large as that for the GaN nanowires alone. However, an outer layer of GaN deposited onto the GaN/AlGaN core/shell nanowires decreases the Seebeck coefficient at room temperature, while the temperature dependence of the electrical conductivity remains the same. We attribute these observations to the formation of an electron gas channel within the heavily-doped GaN core of the GaN/AlGaN nanowires. The room-temperature thermoelectric power factor for the GaN/AlGaN nanowires can be four times higher than the GaN nanowires. Selective doping in bandgap engineered core/shell nanowires is proposed for enhancing the thermoelectric power. (paper)

  16. Off-shell distortions of multichannel atomic processes

    Science.gov (United States)

    Barrachina, R. O.; Clauser, C. F.

    2017-10-01

    Any multichannel problem can be reduced to a succession of two-body events. However, these basic building blocks of many-body theories do not correspond to elastic processes but are off-the-energy-shell. In view of this difficulty, the great majority of the Distorted-Wave models includes a subsidiary approximation where these off-shell terms are arbitrarily forced to lie on the energy shell. At a first glance, since the energy deficiency is negligible for high enough velocities, the on-shell assumption seems to be completely justified. However, for the case of Coulomb interactions, the two-body off-shell distortions have branch-point singularities on the on-shell limit. In this article we demonstrate that these singularities might produce sizeable distortions of multiple scattering amplitudes, mainly when dealing with ion-ion collisions. Finally, we propose a method of including these distortions that might lead to better results that removing them completely.

  17. Micro-Raman investigations of InN-GaN core-shell nanowires on Si (111) substrate

    Energy Technology Data Exchange (ETDEWEB)

    Sangeetha, P.; Ramakrishnan, V. [Department of Laser Studies, School of Physics, Madurai Kamaraj University, Madurai-625 021 (India); Jeganathan, K. [Centre for Nanoscience and Nanotechnology, School of Physics, Bharathidasan University, Tiruchirappalli-620 024 (India)

    2013-06-15

    The electron-phonon interactions in InN-GaN core-shell nanowires grown by plasma assisted- molecular beam epitaxy (MBE) on Si (111) substrate have been analysed using micro-Raman spectroscopic technique with the excitation wavelength of 633, 488 and 325 nm. The Raman scattering at 633 nm reveals the characteristic E{sub 2} (high) and A{sub 1} (LO) phonon mode of InN core at 490 and 590 cm{sup -1} respectively and E{sub 2} (high) phonon mode of GaN shell at 573 cm{sup -1}. The free carrier concentration of InN core is found to be low in the order {approx} 10{sup 16} cm{sup -3} due to the screening of charge carriers by thin GaN shell. Diameter of InN core evaluated using the spatial correlation model is consistent with the transmission electron microscopic measurement of {approx}15 nm. The phonon-life time of core-shell nanowire structure is estimated to be {approx}0.4 ps. The micro-Raman mapping and its corresponding localised spectra for 325 nm excitation exhibit intense E{sub 2} (high) phonon mode of GaN shell at 573 cm{sup -1} as the decrease of laser interaction length and the signal intensity is quenched at the voids due to high spacing of NWs.

  18. Probability of K atomic shell ionization by heavy particles impact, in functions of the scattering angle

    International Nuclear Information System (INIS)

    Oliveira, P.M.C. de.

    1976-12-01

    A method of calculation of the K atomic shell ionization probability by heavy particles impact, in the semi-classical approximation is presented. In this approximation, the projectile has a classical trajectory. The potential energy due to the projectile is taken as perturbation of the Hamiltonian of the neutral atom. We use scaled Thomas-Fermi wave function for the atomic electrons. The method is valid for intermediate atomic number elements and particle energies of some MeV. Probabilities are calculated for the case of Ag (Z = 47) and protons of 1 and 2 MeV. Results are given as function of scattering angle, and agree well known experimental data and also improve older calculations. (Author) [pt

  19. Superconducting transition temperature and the formation of closed electron shells in the atoms of superconducting compounds

    International Nuclear Information System (INIS)

    Chapnik, I.M.

    1985-01-01

    The relationship between the regularities in the tansition temperature (T/sub c/) values in analogous compounds (having the same structure and stoichiometry) and the formation of the closed electron shells outside inert gas shells in the atoms of the variable component of the 158 intermetallic superconducting compounds has been discussed. The T/sub c/ data for compounds of the elements from the first long period of the Periodic Table (K to Se) are compared with the T/sub c/ data for the analogous compounds of the elements from the second long period (Rb to Te)

  20. Fabrication and photoelectrochemical properties of silicon nanowires/g-C{sub 3}N{sub 4} core/shell arrays

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Zhen [Institute of Electronic Paper Displays, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou, Guangdong Province (China); Institute of Advanced Materials, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou, Guangdong Province (China); Ma, Ge [Institute of Electronic Paper Displays, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou, Guangdong Province (China); Chen, Zhihong, E-mail: chenzhihong1227@sina.com [Shenyang Institute of Automation, Guangzhou, Chinese Academy of Sciences, Guangzhou 511458 (China); Zhang, Yongguang [Research Institute for Energy Equipment Materials, Tianjin Key Laboratory of Materials Laminating Fabrication and Interface Control Technology, Hebei University of Technology, Tianjin 300130 (China); Zhang, Zhe [Institute of Electronic Paper Displays, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou, Guangdong Province (China); Gao, Jinwei [Institute of Advanced Materials, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou, Guangdong Province (China); Meng, Qingguo; Yuan, Mingzhe [Shenyang Institute of Automation, Guangzhou, Chinese Academy of Sciences, Guangzhou 511458 (China); Wang, Xin, E-mail: wangxin@scnu.edu.cn [Institute of Electronic Paper Displays, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou, Guangdong Province (China); Liu, Jun-ming [Institute of Advanced Materials, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou, Guangdong Province (China); Zhou, Guofu [Institute of Electronic Paper Displays, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou, Guangdong Province (China)

    2017-02-28

    Highlights: • A novel Silicon Nanowires/g-C{sub 3}N{sub 4} core/shell arrays photoanode prepared by a mild and inexpensive metal-catalyzed electroless etching (MCEE) process followed by liquid atomic layer deposition (LALD), wiich is a facile and low-cost method. • In comparison with FTO/g-C{sub 3}N{sub 4} and Si NWs samples, the Si NWs/g-C{sub 3}N{sub 4} samples showed significantly enhanced photocurrent which could be attributed to the SiNWs-based core/shell structure. • A systematical PEC mechanism of the Si NWs/g-C{sub 3}N{sub 4} was proposed is this manuscript. - Abstract: A photoelectrochemical (PEC) cell made of metal-free carbon nitride (g-C{sub 3}N{sub 4}) @siliconnanowire(Si NW) arrays (denoted as Si NWs/g-C{sub 3}N{sub 4}) is presented in this work. The as-prepared photoelectrodes with different mass contents of g-C{sub 3}N{sub 4} have been synthesized via a metal-catalyzed electroless etching (MCEE), liquid atomic layer deposition (LALD) and annealing methods. The amount of g-C{sub 3}N{sub 4} on the Si NW arrays can be controlled by tuning the concentration of the cyanamide solution used in the LALD procedure. The dense and vertically aligned Si NWs/g-C{sub 3}N{sub 4} core/shell nanostructures were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). In comparison with FTO/g-C{sub 3}N{sub 4} and Si NW samples, the Si NWs/g-C{sub 3}N{sub 4} samples showed significantly enhanced photocurrents over the entire potential sweep range. Electrochemical impedance spectroscopy (EIS) was conducted to investigate the properties of the charge transfer process, and the results indicated that the enhanced PEC performance may be due to the increased photo-generated interfacial charge transfer between the Si NWs and g-C{sub 3}N{sub 4}. The photocurrent density reached 45 μA/cm{sup 2} under 100 mW/cm{sup 2} (AM 1.5 G) illumination at 0 V (vs. Pt) in neutral Na{sub 2}SO{sub 4} solution (pH ∼ 7

  1. Hylleraas-like functions with the correct cusp conditions: K-shell electrons for the neutral atoms

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez, K.V. [Universidad Nacional del Sur, 8000 Bahia Blanca and Consejo Nacional de Investigaciones Cientificas y Tecnicas (Argentina)], E-mail: krodri@criba.edu.ar; Gasaneo, G. [Universidad Nacional del Sur, 8000 Bahia Blanca and Consejo Nacional de Investigaciones Cientificas y Tecnicas (Argentina); Mitnik, D.M.; Miraglia, J.E. [Instituto de Astronomia y Fisica del Espacio and Universidad de Buenos Aires (Argentina)

    2007-10-15

    We present simple correlated wavefunctions for the two K-shell electrons of neutral atoms. A variational method was chosen to calculate the mean energy of the ground state, in which the electrons are subject to a local Hartree potential representing the presence of the outer shell electrons. The functions are constructed in terms of exponential and power series, where special care has been taken in order to fulfill the exact behavior at the electron-electron and electron-nucleus coalescence points (Kato cusp conditions). Global properties, such as the energies and virial coefficients, as well as local properties, such as spatial mean values, are also analyzed.

  2. Measurement of ground state properties of neutron-rich nuclei on the r-process path between the N=50 and N=82 shells

    CERN Multimedia

    2007-01-01

    The evolution of the unknown ground-state ${\\beta}$-decay properties of the neutron-rich $^{84-89}$Ge, $^{90-93}$Se and $^{102-104}$Sr isotopes near the r-process path is of high interest for the study of the abundance peaks around the N=50 and N=82 neutron shells. At ISOLDE, beams of certain elements with sufficient isotopic purity are produced as molecular sidebands rather than atomic beams. This applies e.g, to germanium, separated as GeS$^{+}$, selenium separated as SeCO$^{+}$ and strontium separated as SrF$^{+}$. However, in case of neutron-rich isotopes produced in actinide targets, new "isobaric" background of atomic ions appears on the mass of the molecular sideband. For this particular case, the ECR charge breeder, positioned in the experimental hall after ISOLDE first mass separation, can be advantageously used as a purification device, by breaking the molecules and removing the molecular contaminants. This proposal indicates our interest in the study of basic nuclear structure properties of neutron...

  3. Conference proceedings on X84 International Conference on X-ray and Inner-Shell Processes in Atoms, Molecules and Solids

    International Nuclear Information System (INIS)

    Meisel, A.; Finster, J.

    1984-01-01

    The proceedings contain 46 lectures and contributions presented at the 1984 conference. Topics of the conference were ion-atom collisions, inner-shell ionization phenomena, X-ray spectroscopy and electron spectroscopy

  4. In-situ observation of Cu-Pt core-shell nanoparticles in the atomic scale by XAFS

    International Nuclear Information System (INIS)

    Zheng, Xusheng; Liu, Shoujie; Chen, Xing; Cheng, Jie; Ye, Qing; Pan, Zhiyun; Chu, Wangsheng; Wu, Ziyu; Marcelli, Augosto

    2013-01-01

    Bimetallic nanoparticles play an important role in potential industrial applications, such as catalysis, optoelectronics, information storage and biological labeling. Herein, homogeneous Cu-Pt core-shell nanoparticles with the averaged size of 8 nm have been synthesized by chemical methods. Cu atoms diffusion process, which motivated by heating, was observed in-situ by using temperature-dependent x-ray absorption fine-structure (XAFS) spectroscopy. Results show that Cu diffuse gradually from Cu core to Pt shell in these nanoparticles with increasing temperature. We also found the surface ligand (O) bonded Pt at the room temperature and were removed gradually by heating the sample. The analysis of the diffusion process in bimetallic nanoparticles will provide important guideline for their designing and tuning.

  5. Study of the N=40 shell by using Coulomb excitation

    International Nuclear Information System (INIS)

    Leenhardt, St.

    2000-01-01

    Two Coulomb excitation experiments on neutron rich exotic nuclei have been performed at GANIL. They allowed the measurement of the reduced transition probability B(E2) (from ground state to first excited state) of some nuclei around N = 40. This number, 40, is a half-magic number in the shell model. For nuclei with an important neutron excess, it is predicted that the shell closure is stronger at N = 40. The B(E2) is a good tool for testing this growing. We have measured, by using the LISE3 spectrometer and a γ multidetector, B(E2) of 68 Ni, 66 Ni and 72 Zn, unknown till now. We have used for the first time segmented germanium 'clovers' detector, for photon detection (v/c∼0.3). Results confirm the strong shell effect for 68 Ni. Indeed 68 Ni was shown to be the Nickel isotope with the lowest value of B(E2), and hence the most rigid isotope. Nevertheless it seems that the shell effect at N = 40 decreases rapidly, for other isotopes very close to 68 Ni(Z = 28) and N = 40). (authors)

  6. Wilson lines, Grassmannians and gauge invariant off-shell amplitudes in N=4 SYM

    Energy Technology Data Exchange (ETDEWEB)

    Bork, L.V. [Institute for Theoretical and Experimental Physics,Moscow (Russian Federation); The Center for Fundamental and Applied Research,All-Russia Research Institute of Automatics, Moscow (Russian Federation); Onishchenko, A.I. [Bogoliubov Laboratory of Theoretical Physics,Joint Institute for Nuclear Research, Dubna (Russian Federation); Moscow Institute of Physics and Technology State University,Dolgoprudny (Russian Federation); Skobeltsyn Institute of Nuclear Physics, Moscow State University,Moscow (Russian Federation)

    2017-04-04

    In this paper we consider tree-level gauge invariant off-shell amplitudes (Wilson line form factors) in N=4 SYM. For the off-shell amplitudes with one leg off-shell we present a conjecture for their Grassmannian integral representation in spinor helicity, twistor and momentum twistor parameterizations. The presented conjecture is successfully checked against BCFW results for MHV{sub n}, NMHV{sub 4} and NMHV{sub 5} off-shell amplitudes. We have also verified that our Grassmannian integral representation correctly reproduces soft (on-shell) limit for the off-shell gluon momentum. It is shown that the (deformed) off-shell amplitude expressions could be also obtained using quantum inverse scattering method for auxiliary gl(4|4) super spin chain.

  7. Formation of hollow atoms above a surface

    Science.gov (United States)

    Briand, Jean Pierre; Phaneuf, Ronald; Terracol, Stephane; Xie, Zuqi

    2012-06-01

    Slow highly stripped ions approaching or penetrating surfaces are known to capture electrons into outer shells of the ions, leaving the innermost shells empty, and forming hollow atoms. Electron capture occurs above and below the surfaces. The existence of hollow atoms below surfaces e.g. Ar atoms whose K and L shells are empty, with all electrons lying in the M and N shells, was demonstrated in 1990 [1]. At nm above surfaces, the excited ions may not have enough time to decay before hitting the surfaces, and the formation of hollow atoms above surfaces has even been questioned [2]. To observe it, one must increase the time above the surface by decelerating the ions. We have for the first time decelerated O^7+ ions to energies as low as 1 eV/q, below the minimum energy gained by the ions due to the acceleration by their image charge. As expected, no ion backscattering (trampoline effect) above dielectric (Ge) was observed and at the lowest ion kinetic energies, most of the observed x-rays were found to be emitted by the ions after surface contact. [4pt] [1] J. P. Briand et al., Phys.Rev.Lett. 65(1990)159.[0pt] [2] J.P. Briand, AIP Conference Proceedings 215 (1990) 513.

  8. Probing the N=50 shell gap near $^{78}$Ni

    CERN Multimedia

    Reiter, P; Blazhev, A A; Franchoo, S; Hadinia, B; Raabe, R; Diriken, J V J; Angus, L J

    An experiment is proposed to study the properties of low-lying states close to the N=50 shell gap by single nucleon transfer. The d($^{78}$Zn,p)$\\,^{79}$Zn reaction will be studied using the T-REX silicon-detector array coupled to the MINIBALL $\\gamma$-ray spectrometer. A $^{78}$Zn beam intensity of 5 x 10$^{4}$ pps is expected. The isotope $^{79}$Zn, with Z=30 and N =49, lies two protons above and one neutron below the double-shell closure at $^{78}$Ni. Determination of the single-particle structure of low-lying states in $^{79}$Zn will provide valuable information about the persistence of the N=50 shell gap in this neutron-rich region. In particular the behaviour of the g$_{9/2}$ and d$_{5/2}$ orbitals will be investigated. In total, 27 shifts of beam time are requested. This experiment is envisaged to be the first of a series of measurements on progressively more neutron-rich Zn isotopes.

  9. Micro-Raman investigations of InN-GaN core-shell nanowires on Si (111) substrate

    OpenAIRE

    P. Sangeetha; K. Jeganathan; V. Ramakrishnan

    2013-01-01

    The electron-phonon interactions in InN-GaN core-shell nanowires grown by plasma assisted- molecular beam epitaxy (MBE) on Si (111) substrate have been analysed using micro-Raman spectroscopic technique with the excitation wavelength of 633, 488 and 325 nm. The Raman scattering at 633 nm reveals the characteristic E2 (high) and A1 (LO) phonon mode of InN core at 490 and 590 cm−1 respectively and E2 (high) phonon mode of GaN shell at 573 cm−1. The free carrier concentration of InN core is foun...

  10. Z dependence of the N=152 deformed shell gap: In-beam γ-ray spectroscopy of neutron-rich 245,246Pu

    International Nuclear Information System (INIS)

    Makii, H.; Ishii, T.; Asai, M.; Tsukada, K.; Toyoshima, A.; Ichikawa, S.; Matsuda, M.; Makishima, A.; Kaneko, J.; Toume, H.; Shigematsu, S.; Kohno, T.; Ogawa, M.

    2007-01-01

    We have measured in-beam γ rays in the neutron-rich 246 Pu 152 and 245 Pu 151 nuclei by means of 244 Pu( 18 O, 16 O) 246 Pu and 244 Pu( 18 O, 17 O) 245 Pu neutron transfer reactions, respectively. The γ rays emitted from 246 Pu ( 245 Pu) were identified by selecting the kinetic energy of scattered 16 O ( 17 O) detected by Si ΔE-E detectors. The ground-state band of 246 Pu was established up to the 12 + state. We have found that the shell gap of N=152 is reduced in energy with decreasing atomic number by extending the systematics of the one-quasiparticle energies in N=151 nuclei into those in 245 Pu. This reduction of the shell gap clearly affects the 2 + energy of the ground-state band of 246 Pu

  11. Transformation mechanism of n-butyl terminated Si nanoparticles embedded into Si1-xCx nanocomposites mixed with Si nanoparticles and C atoms

    International Nuclear Information System (INIS)

    Shin, J.W.; Oh, D.H.; Kim, T.W.; Cho, W.J.

    2009-01-01

    Bright-field transmission electron microscopy (TEM) images, high-resolution TEM (HRTEM) images, and fast-Fourier transformed electron-diffraction patterns showed that n-butyl terminated Si nanoparticles were aggregated. The formation of Si 1-x C x nanocomposites was mixed with Si nanoparticles and C atoms embedded in a SiO 2 layer due to the diffusion of C atoms from n-butyl termination shells into aggregated Si nanoparticles. Atomic force microscopy (AFM) images showed that the Si 1-x C x nanocomposites mixed with Si nanoparticles and C atoms existed in almost all regions of the SiO 2 layer. The formation mechanism of Si nanoparticles and the transformation mechanism of n-butyl terminated Si nanoparticles embedded into Si 1-x C x nanocomposites mixed with Si nanoparticles and C atoms are described on the basis of the TEM, HRTEM, and AFM results. These results can help to improve the understanding of the formation mechanism of Si nanoparticles.

  12. Emission Characteristics of InGaN/GaN Core-Shell Nanorods Embedded in a 3D Light-Emitting Diode.

    Science.gov (United States)

    Jung, Byung Oh; Bae, Si-Young; Lee, Seunga; Kim, Sang Yun; Lee, Jeong Yong; Honda, Yoshio; Amano, Hiroshi

    2016-12-01

    We report the selective-area growth of a gallium nitride (GaN)-nanorod-based InGaN/GaN multiple-quantum-well (MQW) core-shell structure embedded in a three-dimensional (3D) light-emitting diode (LED) grown by metalorganic chemical vapor deposition (MOCVD) and its optical analysis. High-resolution transmission electron microscopy (HR-TEM) observation revealed the high quality of the GaN nanorods and the position dependence of the structural properties of the InGaN/GaN MQWs on multiple facets. The excitation and temperature dependences of photoluminescence (PL) revealed the m-plane emission behaviors of the InGaN/GaN core-shell nanorods. The electroluminescence (EL) of the InGaN/GaN core-shell-nanorod-embedded 3D LED changed color from green to blue with increasing injection current. This phenomenon was mainly due to the energy gradient and deep localization of the indium in the selectively grown InGaN/GaN core-shell MQWs on the 3D architecture.

  13. Local conditions for the Pauli potential in order to yield self-consistent electron densities exhibiting proper atomic shell structure

    Energy Technology Data Exchange (ETDEWEB)

    Finzel, Kati, E-mail: kati.finzel@liu.se [Linköpings University, IFM Department of Physics, 58183 Linköping (Sweden)

    2016-01-21

    The local conditions for the Pauli potential that are necessary in order to yield self-consistent electron densities from orbital-free calculations are investigated for approximations that are expressed with the help of a local position variable. It is shown that those local conditions also apply when the Pauli potential is given in terms of the electron density. An explicit formula for the Ne atom is given, preserving the local conditions during the iterative procedure. The resulting orbital-free electron density exhibits proper shell structure behavior and is in close agreement with the Kohn-Sham electron density. This study demonstrates that it is possible to obtain self-consistent orbital-free electron densities with proper atomic shell structure from simple one-point approximations for the Pauli potential at local density level.

  14. Inner shell transitions of BrI in the EUV

    Energy Technology Data Exchange (ETDEWEB)

    Mazzoni, M [Florence Univ. (Italy). Ist. di Astronomia; Pettini, M [Osservatorio Astrofisico di Arcetri, Florence (Italy)

    1981-10-12

    The EUV line spectrum originating from transitions of the inner 3d shell of neutral atomic bromine has been observed in absorption. Fano parameters have been derived for the three autoionized resonances nd/sup 10/(n + 1)s/sup 2/(n + 1)p/sup 5/ /sup 2/P-nd/sup 9/(n + 1)s/sup 2/(n + 1)p/sup 62/D observed in both bromine (n = 3) and iodine (n = 4) spectra.

  15. K-shell excitation studied for H- and He-like bismuth ions in collisions with low-z target atoms

    International Nuclear Information System (INIS)

    Stoehlker, T.; Bosch, F.; Geissel, H.; Kozhuharov, C.; Ludziejewski, T.; Mokler, P.H.; Scheidenberger, C.; Stachura, Z.; Warczak, A.

    1997-09-01

    The formation of excited projectile states via Coulomb excitation is investigated for hydrogen- and helium-like bismuth projectiles (Z=83) in relativistic ion-atom collisions. The excitation process was unambiguously identified by observing the radiative decay of the excited levels to the vacant 1s shell in coincidence with ions that did not undergo charge exchange in the reaction target. In particular, owing to the large fine structure splitting of Bi, the excitation cross-sections to the various L-shell sublevels are determined separately. The results are compared with detailed relativistic calculations, showing that both the relativistic character of the bound-state wave-functions and the magnetic interaction are of considerable importance for the K-shell excitation process in high-Z ions like Bi. The experimental data confirm the result of the complete relativistic calculations, namely that the magnetic part of the Lienard-Wiechert interaction leads to a significant reduction of the K-shell excitation cross-section. (orig.)

  16. Deeply bound pionic atom

    International Nuclear Information System (INIS)

    Toki, Hiroshi; Yamazaki, Toshimitsu

    1989-01-01

    The standard method of pionic atom formation does not produce deeply bound pionic atoms. A study is made on the properties of deeply bound pionic atom states by using the standard pion-nucleus optical potential. Another study is made to estimate the cross sections of the formation of ls pionic atom states by various methods. The pion-nucleus optical potential is determined by weakly bound pionic atom states and pion nucleus scattering. Although this potential may not be valid for deeply bound pionic atoms, it should provide some hint on binding energies and level widths of deeply bound states. The width of the ls state comes out to be 0.3 MeV and is well separated from the rest. The charge dependence of the ls state is investigated. The binding energies and the widths increase linearly with Z azbove a Z of 30. The report then discusses various methods to populate deeply bound pionic atoms. In particular, 'pion exchange' reactions are proposed. (n, pπ) reaction is discussed first. The cross section is calculated by assuming the in- and out-going nucleons on-shell and the produced pion in (n1) pionic atom states. Then, (n, dπ - ) cross sections are estimated. (p, 2 Heπ - ) reaction would have cross sections similar to the cross section of (n, dπ - ) reaction. In conclusion, it seems best to do (n, p) experiment on heavy nuclei for deeply bound pionic atom. (Nogami, K.)

  17. Interplay of spherical closed shells and N /Z asymmetry in quasifission dynamics

    Science.gov (United States)

    Mohanto, G.; Hinde, D. J.; Banerjee, K.; Dasgupta, M.; Jeung, D. Y.; Simenel, C.; Simpson, E. C.; Wakhle, A.; Williams, E.; Carter, I. P.; Cook, K. J.; Luong, D. H.; Palshetkar, C. S.; Rafferty, D. C.

    2018-05-01

    Background: Quasifission (QF) has gained tremendous importance in heavy-ion nuclear physics research because of its strong influence on superheavy-element synthesis. Collisions involving closed-shell nuclei in the entrance channel are found to affect the QF reaction mechanism. Hence, it is important to improve the understanding of their effect on QF. Apart from that, some recent studies show that the difference in N /Z of reaction partners influences the reaction dynamics. Since heavier doubly magic nuclei have different N /Z than lighter doubly magic nuclei, it is important to understand the effect of N /Z mismatch as well as the effect of shell closures. Purpose: To investigate the effect of entrance-channel shell closures and N /Z asymmetry on QF. The reactions were chosen to decouple these effects from the contributions of other entrance-channel parameters. Method: Fission fragment mass-angle distributions were measured using the CUBE fission spectrometer, consisting of two large area position-sensitive multi-wire proportional counters (MWPCs), for five reactions, namely, 50Cr+208Pb , 52Cr+Pb,208206 , 54Cr+Pb,208204 . Result: Two components were observed in the measured fragment mass angle distribution, a fast mass-asymmetric quasifission and a slow mass-symmetric component having a less significant mass-angle correlation. The ratio of these components was found to depend on spherical closed shells in the entrance channel nuclei and the magnitude of the N /Z mismatch between the two reaction partners, as well as the beam energy. Conclusions: Entrance-channel spherical closed shells can enhance compound nucleus formation provided the N /Z asymmetry is small. Increase in the N /Z asymmetry is expected to destroy the effect of entrance-channel spherical closed shells, through nucleon transfer reactions.

  18. Coulomb ionization of inner shells by heavy charged particles

    International Nuclear Information System (INIS)

    Lapicki, G.

    1975-01-01

    The theory of inner-shell Coulomb ionization by heavy charged particles, of atomic number small compared to the target atomic number, is developed through the extension of work by Brandt and his coworkers for K shells to L shells. In slow collisions relative to the characteristic times of the inner shell electrons, the quantum-mechanical predictions in the plane-wave Born approximation (PWBA) can exceed experimental cross sections by orders of magnitude. The effects of the perturbation of the atom by and the Coulomb deflection of the particle during collisions are included in the theory. The perturbed atomic states amount to a binding of the inner-shell electrons to the moving particle in slow collisions, and to a polarization of the inner shells by the particle passing at large impact parameters during nonadiabatic collisions. These effects, not contained in the PWBA, are treated in the framework of the perturbed stationary state (PSS) theory for slow collisions and in terms of the harmonic oscillator model of Ashley, Brandt, and Ritchie for stopping powers in fast collisions. The effect of the Coulomb deflection of the particle in the field of the target nucleus on the cross sections is incorporated in the semiclassical approximation of Bang and Hansteen. Except for the lightest target atoms, the contribution of electron capture by the particles to inner-shell ionizations is shown to be negligible. The theory as developed earlier for the K shell, and here for L shells, agrees well with the vast body of experimental data on inner-shell Coulomb ionization by heavy charged particles

  19. The rate coefficients for the processes of (n - n')-mixing in collisions of Rydberg atoms H*(n) with H(1s) atoms

    International Nuclear Information System (INIS)

    Mihajlov, A A; Ignjatovic, Lj M; Djuric, Z; Ljepojevic, N N

    2004-01-01

    This paper presents the results of semi-classical calculations of rate coefficients of (n - n')-mixing processes in collisions of Rydberg atoms H*(n) with H(1s) atoms. These processes have been modelled by the mechanism of the resonant energy exchange within the electron component of the H*(n) + H collisional system. The calculations of the rate coefficients, based on this model, were performed for the series of principal quantum numbers, n and n', and atomic, T a , and electronic, T e , temperatures. It was shown that these processes can be of significant influence on the populations of Rydberg atoms in weakly ionized plasmas (ionization degree ∼ -4 ), and therefore have to be included in appropriate models of such plasmas

  20. Synthesis and characterization of thermal energy storage microencapsulated n-dodecanol with acrylic polymer shell

    International Nuclear Information System (INIS)

    Ma, Yanjie; Zong, Jiwen; Li, Wei; Chen, Long; Tang, Xiaofen; Han, Na; Wang, Jianping; Zhang, Xingxiang

    2015-01-01

    Two kinds of (microencapsulated phase change materials) MicroPCMs with acrylic-based copolymer as shell and n-dodecanol as core were successfully fabricated via suspension-like polymerization and photo-induced microencapsulation, respectively. Morphology and core–shell structure were observed by (field emission scanning electron microscope) FE-SEM. Thermal properties of the microencapsulated n-dodecanol were investigated by (differential scanning calorimeter) DSC and (thermogravimetric analysis) TGA. The results indicate that the mass ratio of core to shell has great influence on the morphology, inner structure, microencapsulated efficiency and durability of the microcapsules. Besides, the effects of various solvents and UV irridiation time on the microcapsule surface were discussed as well. In the experiment carried out, metal-ion complexation was conducted by the reaction between Mn ion and carboxyl groups on copolymer shell to enhance the performance of the microcapsules with n-dodecanol encapsulated. As the results indicate, the physicochemical properties and thermal conductivity of the shell were improved after Mn ion complexation reaction. Supercooling phenomenon of n-dodecanol was depressed to some extent. In the end, the thermo-regulated fiber containing acrylic-based copolymer microcapsules was fabricated, and thermo-regulated performance test of the fiber was also conducted. - Graphical abstract: (a)∼(d) schematic diagram of microencapsulation and (e) microcapsule with core–shell structure. - Highlights: • Microencapsulated n-dodecanol with acrylic polymer shell. • Microencapsulated n-dodecanol was fabricated by photo-induced microencapsulation. • Acrylic-based copolymer microcapsules with manganese-ion complexation

  1. Approximate symmetries in atomic nuclei from a large-scale shell-model perspective

    Science.gov (United States)

    Launey, K. D.; Draayer, J. P.; Dytrych, T.; Sun, G.-H.; Dong, S.-H.

    2015-05-01

    In this paper, we review recent developments that aim to achieve further understanding of the structure of atomic nuclei, by capitalizing on exact symmetries as well as approximate symmetries found to dominate low-lying nuclear states. The findings confirm the essential role played by the Sp(3, ℝ) symplectic symmetry to inform the interaction and the relevant model spaces in nuclear modeling. The significance of the Sp(3, ℝ) symmetry for a description of a quantum system of strongly interacting particles naturally emerges from the physical relevance of its generators, which directly relate to particle momentum and position coordinates, and represent important observables, such as, the many-particle kinetic energy, the monopole operator, the quadrupole moment and the angular momentum. We show that it is imperative that shell-model spaces be expanded well beyond the current limits to accommodate particle excitations that appear critical to enhanced collectivity in heavier systems and to highly-deformed spatial structures, exemplified by the second 0+ state in 12C (the challenging Hoyle state) and 8Be. While such states are presently inaccessible by large-scale no-core shell models, symmetry-based considerations are found to be essential.

  2. Inner-shell near-threshold photoionization of A-C60 endohedral atoms

    International Nuclear Information System (INIS)

    Baltenkov, Arkadiy S.; Dolmatov, Valery K.; Manson, Steven T.

    2002-01-01

    Photoelectron angular distributions and total photoionization cross sections of near-threshold 1s photoionization of Li from the oriented-in-space endohedral Li-C 60 fullerene are investigated within the framework of our recently developed photoionization theory of multicenter formations. Both at-the-center and off-the-center endohedral Li are considered, and off-the-center effects are shown to be of extreme importance, in contrast to the conventional wisdom. Multiple-scattering effects on the outgoing photoelectron are included and found to influence the photoionization spectra strongly, e.g., decreasing the cross section by more than an order of magnitude in certain cases, as compared to the situation when such effects are neglected. Diffraction resonances in the photoionization cross section of the endohedral Li atom are found as a result of the multicenter nature of the C 60 surrounding cage, and these are compared with the results of other empirical and ab initio theories. Since there is nothing particularly special about Li 1s with respect to photoionization, the trends uncovered in this paper should qualitatively apply to near-threshold inner-shell ns photoionization spectra of virtually any endohedral atom A from any A-C 60 endohedral fullerene formation

  3. TiN/VN composites with core/shell structure for supercapacitors

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Shanmu; Chen, Xiao [Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, No. 189 Songling Road, Qingdao 266101 (China); Gu, Lin [WPI Advanced Institute for Materials Research, Tohoku University, Sendai 9808577 (Japan); Zhou, Xinhong [Qingdao University of Science and Technology, Qingdao 266101 (China); Wang, Haibo; Liu, Zhihong; Han, Pengxian; Yao, Jianhua; Wang, Li [Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, No. 189 Songling Road, Qingdao 266101 (China); Cui, Guanglei, E-mail: cuigl@qibebt.ac.cn [Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, No. 189 Songling Road, Qingdao 266101 (China); Chen, Liquan [Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, No. 189 Songling Road, Qingdao 266101 (China); Institute of Physics, Chinese Academy of Sciences, Beijing 100080 (China)

    2011-06-15

    Research highlights: {yields} Vanadium and titanium nitride nanocomposite with core-shell structure was prepared. {yields} TiN/VN composites with different V:Ti molar ratios were obtained. {yields} TiN/VN composites can provide promising electronic conductivity and favorable capacity storage. -- Abstract: TiN/VN core-shell composites are prepared by a two-step strategy involving coating of commercial TiN nanoparticles with V{sub 2}O{sub 5}.nH{sub 2}O sols followed by ammonia reduction. The highest specific capacitance of 170 F g{sup -1} is obtained when scanned at 2 mV s{sup -1} and a promising rate capacity performance is maintained at higher voltage sweep rates. These results indicate that these composites with good electronic conductivity can deliver a favorable capacity performance.

  4. On the atomic-number similarity of the binding energies of electrons in filled shells of elements of the periodic table

    Science.gov (United States)

    Karpov, V. Ya.; Shpatakovskaya, G. V.

    2017-03-01

    An expression for the binding energies of electrons in the ground state of an atom is derived on the basis of the Bohr-Sommerfeld quantization rule within the Thomas-Fermi model. The validity of this relation for all elements from neon to uranium is tested within a more perfect quantum-mechanical model with and without the inclusion of relativistic effects, as well as with experimental binding energies. As a result, the ordering of electronic levels in filled atomic shells is established, manifested in an approximate atomic-number similarity. It is proposed to use this scaling property to analytically estimate the binding energies of electrons in an arbitrary atom.

  5. On the atomic-number similarity of the binding energies of electrons in filled shells of elements of the periodic table

    Energy Technology Data Exchange (ETDEWEB)

    Karpov, V. Ya. [Bruk Institute of Electronic Control Machines (Russian Federation); Shpatakovskaya, G. V., E-mail: shpagalya@yandex.ru [Russian Academy of Sciences, Keldysh Institute of Applied Mathematics (Russian Federation)

    2017-03-15

    An expression for the binding energies of electrons in the ground state of an atom is derived on the basis of the Bohr–Sommerfeld quantization rule within the Thomas–Fermi model. The validity of this relation for all elements from neon to uranium is tested within a more perfect quantum-mechanical model with and without the inclusion of relativistic effects, as well as with experimental binding energies. As a result, the ordering of electronic levels in filled atomic shells is established, manifested in an approximate atomic-number similarity. It is proposed to use this scaling property to analytically estimate the binding energies of electrons in an arbitrary atom.

  6. Silver atom solvation and desolvation in ice matrices: study of solvation shell geometry by electron spin resonance and electron spin echo methods

    Energy Technology Data Exchange (ETDEWEB)

    Kevan, L; Narayana, P A

    1978-01-01

    Results of studies of the solvation shell structure of silver atoms in ice matrix at 4/sup 0/K by electron spin resonance (ESR) and electron spin echo spectrometry are reported. Drastic change in the hyperfine coupling constant of the silver atom was noted when the silver atom initially produced at 4/sup 0/K was warmed to 77/sup 0/K and reexamined by ESR at 4/sup 0/K. This suggested a very drastic rearrangement of the water molecules surrounding the silver atom. The geometric arrangement of water molecules around the silver atom produced at 4/sup 0/K was what would be expected for a solvated silver ion, indicating that no rearrangement had occurred after the silver atom formed. The addition of a little thermal excitation (heating to 77/sup 0/K) results in the geometry changes than can be explained by assuming either that a water molecule rotates around one of its OH bands or by the development of a hydrogen bond between the silver atom and one of the first solvation shell water molecules. Optical excitation in the absorption band of the silver atom in the ice matrix at 400nm resulted in desolvation of the silver ion or a reversion to the structure originally obtained by reaction of solver salts in ic matrix with radiation produced electrons. This was best explained by a charge transfer mechanism. (BLM)

  7. Line splitting and modified atomic decay of atoms coupled with N quantized cavity modes

    Science.gov (United States)

    Zhu, Yifu

    1992-05-01

    We study the interaction of a two-level atom with N non-degenerate quantized cavity modes including dissipations from atomic decay and cavity damps. In the strong coupling regime, the absorption or emission spectrum of weakly excited atom-cavity system possesses N + 1 spectral peaks whose linewidths are the weighted averages of atomic and cavity linewidths. The coupled system shows subnatural (supernatural) atomic decay behavior if the photon loss rates from the N cavity modes are smaller (larger) than the atomic decay rate. If N cavity modes are degenerate, they can be treated effectively as a single mode. In addition, we present numerical calculations for N = 2 to characterize the system evolution from the weak coupling to strong coupling limits.

  8. MOVPE growth of position-controlled InGaN / GaN core-shell nanorods

    Energy Technology Data Exchange (ETDEWEB)

    Mandl, Martin [Osram Opto Semiconductors GmbH, Regensburg (Germany); Institut fuer Halbleitertechnik, TU Braunschweig (Germany); Schimpke, Tilman; Binder, Michael; Galler, Bastian; Lugauer, Hans-Juergen; Strassburg, Martin [Osram Opto Semiconductors GmbH, Regensburg (Germany); Wang, Xue; Ledig, Johannes; Ehrenburg, Milena; Wehmann, Hergo-Heinrich; Waag, Andreas [Institut fuer Halbleitertechnik, TU Braunschweig (Germany); Kong, Xiang; Trampert, Achim [Paul-Drude-Institut fuer Festkoerperelektronik, Berlin (Germany)

    2013-07-01

    Core-shell group III-nitride nano- and microrods (NAMs) enable a significant increase of the active layer area by exploiting the non-polar side facets (m-planes) and thus can potentially contribute to mitigating the so-called efficiency droop in LEDs. GaN NAMs exhibiting high aspect ratios were grown in a production-type MOVPE system. Low V/III ratio, hydrogen-rich carrier gas mixture and surfactants supported the 3D growth of the pencil-shape n-type GaN core. Desired narrow distributions of shape, diameter and height were achieved. The arrangement of the NAMs was controlled by patterns etched into SiO{sub 2} masks deposited on GaN templates. The active layer (InGaN/GaN SQW and MQWs) and the layer for the p-side were deposited with 2D-like conditions wrapped around the core. The crystalline quality of the NAMs, shell growth rates and the Indium distribution were investigated by high resolution transmission electron microscopy. Furthermore, optical emission was studied using density-dependent photoluminescence spectroscopy.

  9. The rate coefficients for the processes of (n - n')-mixing in collisions of Rydberg atoms H*(n) with H(1s) atoms

    Energy Technology Data Exchange (ETDEWEB)

    Mihajlov, A A [Institute of Physics, PO Box 57, 11001 Belgrade (Serbia and Montenegro); Ignjatovic, Lj M [Institute of Physics, PO Box 57, 11001 Belgrade (Serbia and Montenegro); Djuric, Z [Silvaco Data Systems, Compass Point, St Ives PE27 5JL (United Kingdom); Ljepojevic, N N [Silvaco Data Systems, Compass Point, St Ives PE27 5JL (United Kingdom)

    2004-11-28

    This paper presents the results of semi-classical calculations of rate coefficients of (n - n')-mixing processes in collisions of Rydberg atoms H*(n) with H(1s) atoms. These processes have been modelled by the mechanism of the resonant energy exchange within the electron component of the H*(n) + H collisional system. The calculations of the rate coefficients, based on this model, were performed for the series of principal quantum numbers, n and n', and atomic, T{sub a}, and electronic, T{sub e}, temperatures. It was shown that these processes can be of significant influence on the populations of Rydberg atoms in weakly ionized plasmas (ionization degree {approx}<10{sup -4}), and therefore have to be included in appropriate models of such plasmas.

  10. Atomically thin Pt shells on Au nanoparticle cores: facile synthesis and efficient synergetic catalysis

    DEFF Research Database (Denmark)

    Engelbrekt, Christian; Seselj, Nedjeljko; Poreddy, Raju

    2016-01-01

    in electrooxidation of sustainable fuels (i.e. formic acid, methanol and ethanol), and selective hydrogenation of benzene derivatives. Especially high activity was achieved for formic acid oxidation, 549 mA (mgPt)−1 (at 0.6 V vs. SCE), which is 3.5 fold higher than a commercial ... properties were thoroughly characterized by ultraviolet-visible light spectrophotometry, transmission electron microscopy, nanoparticle tracking analysis and electrochemistry. The 8 ± 2 nm Au@PtNPs contained 24 ± 1 mol% Pt and 76 ± 1 mol% Au corresponding to an atomically thin Pt shell. Electrochemical data...

  11. A new formulation of the relativistic many-body theory of electric dipole moments of closed shell atoms

    International Nuclear Information System (INIS)

    Latha, K V P; Angom, Dilip; Chaudhuri, Rajat K; Das, B P; Mukherjee, Debashis

    2007-01-01

    The electric dipole moments of closed-shell atoms are sensitive to the parity and time-reversal violating phenomena in the nucleus. The nuclear Schiff moment is one such property, it arises from the parity and time reversal violating quark-quark interactions and the quark-chromo electric dipole moments. We calculate the electric dipole moment of atomic 199 Hg arising from the nuclear Schiff moment using the relativistic coupled-cluster theory. This is the most accurate calculation of the quantity to date. Our calculations in combination with the experiment data provide important insights to the P and T violating coupling constants at the elementary particle level. In addition, a new limit on the tensor-pseudo tensor induced atomic EDM, calculated using the relativistic coupled-cluster theory is also presented

  12. Shell structure of potassium isotopes deduced from their magnetic moments

    CERN Document Server

    Papuga, J.; Kreim, K; Barbieri, C; Blaum, K; De Rydt, M; Duguet, T; Garcia Ruiz, R F; Heylen, H; Kowalska, M; Neugart, R; Neyens, G; Nortershauser, W; Rajabali, M M; Sanchez, R; Smirnova, N; Soma, V; Yordanov, D T

    2014-09-29

    $\\textbf{Background:}$ Ground-state spins and magnetic moments are sensitive to the nuclear wave function, thus they are powerful probes to study the nuclear structure of isotopes far from stability. \\\\ \\\\ $\\textbf{Purpose:}$ Extend our knowledge about the evolution of the $1/2^+$ and $3/2^+$ states for K isotopes beyond the $N = 28$ shell gap. \\\\ \\\\ $\\textbf{Method:}$ High-resolution collinear laser spectroscopy on bunched atomic beams. \\\\ \\\\ $\\textbf{Results:}$ From measured hyperfine structure spectra of K isotopes, nuclear spins and magnetic moments of the ground states were obtained for isotopes from $N = 19$ up to $N = 32$. In order to draw conclusions about the composition of the wave functions and the occupation of the levels, the experimental data were compared to shell-model calculations using SDPF-NR and SDPF-U effective interactions. In addition, a detailed discussion about the evolution of the gap between proton $1d_{3/2}$ and $2s_{1/2}$ in the shell model and $\\textit{ab initio}$ framework is al...

  13. The relation between the (N) and (N-1) electrons atomic ground state

    International Nuclear Information System (INIS)

    Briet, P.

    1984-05-01

    The relation between the ground state of an N and (N-1) electrons atomic system are studied. We show that in some directions of the configuration space, the ratio of the N electrons atomic ground state to the one particle density is asymptotically equivalent to the (N-1) electrons atomic ground state

  14. The influence of MOVPE growth conditions on the shell of core-shell GaN microrod structures

    Science.gov (United States)

    Schimpke, Tilman; Avramescu, Adrian; Koller, Andreas; Fernando-Saavedra, Amalia; Hartmann, Jana; Ledig, Johannes; Waag, Andreas; Strassburg, Martin; Lugauer, Hans-Jürgen

    2017-05-01

    A core-shell geometry is employed for most next-generation, three-dimensional opto-electric devices based on III-V semiconductors and grown by metal organic vapor phase epitaxy (MOVPE). Controlling the shape of the shell layers is fundamental for device optimization, however no detailed analysis of the influence of growth conditions has been published to date. We study homogeneous arrays of gallium nitride core-shell microrods with height and diameter in the micrometer range and grown in a two-step selective area MOVPE process. Changes in shell shape and homogeneity effected by deliberately altered shell growth conditions were accurately assessed by digital analysis of high-resolution scanning electron microscope images. Most notably, two temperature regimes could be established, which show a significantly different behavior with regard to material distribution. Above 900 °C of wafer carrier temperature, the shell thickness along the growth axis of the rods was very homogeneous, however variations between vicinal rods increase. In contrast, below 830 °C the shell thickness is higher close to the microrod tip than at the base of the rods, while the lateral homogeneity between neighboring microrods is very uniform. This temperature effect could be either amplified or attenuated by changing the remaining growth parameters such as reactor pressure, structure distance, gallium precursor, carrier gas composition and dopant materials. Possible reasons for these findings are discussed with respect to GaN decomposition as well as the surface and gas phase diffusion of growth species, leading to an improved control of the functional layers in next-generation 3D V-III devices.

  15. Strontium clusters: electronic and geometry shell effects

    DEFF Research Database (Denmark)

    Lyalin, Andrey G.; Solov'yov, Ilia; Solov'yov, Andrey V.

    2008-01-01

    charged strontium clusters consisting of up to 14 atoms, average bonding distances, electronic shell closures, binding energies per atom, and spectra of the density of electronic states (DOS). It is demonstrated that the size-evolution of structural and electronic properties of strontium clusters...... is governed by an interplay of the electronic and geometry shell closures. Influence of the electronic shell effects on structural rearrangements can lead to violation of the icosahedral growth motif of strontium clusters. It is shown that the excessive charge essentially affects the optimized geometry...

  16. Interelectron correlations in photoionization of outer shells near inner shell thresholds

    International Nuclear Information System (INIS)

    Amusia, M Ya; Chernysheva, L V; Drukarev, E G

    2015-01-01

    We have studied the role of virtual excitations of inner shells upon outer shell photoionization. The calculations were performed in the frames of the Random Phase Approximation with Exchange (RPAE) and its generalized version GRPAE that take into account variation of the atomic field due to electron elimination and the inner vacancies decay. We apply both analytic approximation and numeric computations. The results are presented for 3p electrons in Ar and for 4d-electrons in Pd near inner shells thresholds. The effect considered proved to be quite noticeable. (paper)

  17. Poly(n-isopropylacrylamide)-based hydrogel coatings on magnetite nanoparticles via atom transfer radical polymerization

    Energy Technology Data Exchange (ETDEWEB)

    Frimpong, Reynolds A; Hilt, J Zach [Department of Chemical and Materials Engineering, University of Kentucky, Lexington, KY 40506 (United States)], E-mail: hilt@engr.uky.edu

    2008-04-30

    Core magnetite (Fe{sub 3}O{sub 4}) nanoparticles have been functionalized with a model intelligent hydrogel system based on the temperature responsive polymer poly(n-isopropyl acrylamide) (PNIPAAm) to obtain magnetically responsive core-shell nanocomposites. Fe{sub 3}O{sub 4} nanoparticles were obtained from a one-pot co-precipitation method which provided either oleic acid (hydrophobic) or citric acid (hydrophilic) coated nanoparticles. Subsequent ligand exchange of these coatings with various bromine alkyl halides and a bromo silane provided initiating sites for functionalization with NIPAAm using atom transfer radical polymerization (ATRP). The bromine alkyl halides that were used were 2-bromo-2-methyl propionic acid (BMPA) and 2-bromopropionyl bromide (BPB). The bromo silane that was used was 3-bromopropyl trimethoxysilane (BPTS). The intelligent polymeric shell consists of NIPAAm crosslinked with poly(ethylene glycol) 400 dimethacrylate (PEG400DMA). Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and transmission electron microscopy (TEM) were used to confirm the presence of the polymeric shell. Dynamic light scattering (DLS) was used to characterize the nanocomposites for particle size changes with temperature. Their magnetic and temperature responsiveness show great promise for further biomedical applications. This platform for functionalizing magnetic nanoparticles with intelligent hydrogels promises to impact a wide range of medical and biological applications of magnetic nanoparticles.

  18. Poly(n-isopropylacrylamide)-based hydrogel coatings on magnetite nanoparticles via atom transfer radical polymerization

    International Nuclear Information System (INIS)

    Frimpong, Reynolds A; Hilt, J Zach

    2008-01-01

    Core magnetite (Fe 3 O 4 ) nanoparticles have been functionalized with a model intelligent hydrogel system based on the temperature responsive polymer poly(n-isopropyl acrylamide) (PNIPAAm) to obtain magnetically responsive core-shell nanocomposites. Fe 3 O 4 nanoparticles were obtained from a one-pot co-precipitation method which provided either oleic acid (hydrophobic) or citric acid (hydrophilic) coated nanoparticles. Subsequent ligand exchange of these coatings with various bromine alkyl halides and a bromo silane provided initiating sites for functionalization with NIPAAm using atom transfer radical polymerization (ATRP). The bromine alkyl halides that were used were 2-bromo-2-methyl propionic acid (BMPA) and 2-bromopropionyl bromide (BPB). The bromo silane that was used was 3-bromopropyl trimethoxysilane (BPTS). The intelligent polymeric shell consists of NIPAAm crosslinked with poly(ethylene glycol) 400 dimethacrylate (PEG400DMA). Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and transmission electron microscopy (TEM) were used to confirm the presence of the polymeric shell. Dynamic light scattering (DLS) was used to characterize the nanocomposites for particle size changes with temperature. Their magnetic and temperature responsiveness show great promise for further biomedical applications. This platform for functionalizing magnetic nanoparticles with intelligent hydrogels promises to impact a wide range of medical and biological applications of magnetic nanoparticles

  19. Structures of 38-atom gold-platinum nanoalloy clusters

    Energy Technology Data Exchange (ETDEWEB)

    Ong, Yee Pin; Yoon, Tiem Leong [School of Physics, Universiti Sains Malaysia, 11800 USM, Penang (Malaysia); Lim, Thong Leng [Faculty of Engineering and Technology, Multimedia University, Melaka Campus, 75450 Melaka (Malaysia)

    2015-04-24

    Bimetallic nanoclusters, such as gold-platinum nanoclusters, are nanomaterials promising wide range of applications. We perform a numerical study of 38-atom gold-platinum nanoalloy clusters, Au{sub n}Pt{sub 38−n} (0 ≤ n ≤ 38), to elucidate the geometrical structures of these clusters. The lowest-energy structures of these bimetallic nanoclusters at the semi-empirical level are obtained via a global-minimum search algorithm known as parallel tempering multi-canonical basin hopping plus genetic algorithm (PTMBHGA), in which empirical Gupta many-body potential is used to describe the inter-atomic interactions among the constituent atoms. The structures of gold-platinum nanoalloy clusters are predicted to be core-shell segregated nanoclusters. Gold atoms are observed to preferentially occupy the surface of the clusters, while platinum atoms tend to occupy the core due to the slightly smaller atomic radius of platinum as compared to gold’s. The evolution of the geometrical structure of 38-atom Au-Pt clusters displays striking similarity with that of 38-atom Au-Cu nanoalloy clusters as reported in the literature.

  20. Restricted open-shell Kohn-Sham theory: N unpaired electrons

    International Nuclear Information System (INIS)

    Schulte, Marius; Frank, Irmgard

    2010-01-01

    Graphical abstract: High-spin or low-spin? The lowest-lying states for different multiplicities of iron complexes are described with a combination of restricted open-shell Kohn-Sham theory and Car-Parrinello molecular dynamics. - Abstract: We present an energy expression for restricted open-shell Kohn-Sham theory for N unpaired electrons. It is shown that it is possible to derive an explicit energy expression for all low-spin multiplets of systems that exhibit neither radial nor cylindrical symmetry. The approach was implemented in the CPMD code and tested for iron complexes.

  1. Grassmannian integral for general gauge invariant off-shell amplitudes in N=4 SYM

    Energy Technology Data Exchange (ETDEWEB)

    Bork, L.V. [Institute for Theoretical and Experimental Physics,Moscow (Russian Federation); The Center for Fundamental and Applied Research,All-Russia Research Institute of Automatics, Moscow (Russian Federation); Onishchenko, A.I. [Bogoliubov Laboratory of Theoretical Physics,JointInstitute for Nuclear Research, Dubna (Russian Federation); Moscow Institute of Physics and Technology, State University,Dolgoprudny (Russian Federation); Skobeltsyn Institute of Nuclear Physics, Moscow State University,Moscow (Russian Federation)

    2017-05-08

    In this paper we consider tree-level gauge invariant off-shell amplitudes (Wilson line form factors) in N=4 SYM with arbitrary number of off-shell gluons or equivalently Wilson line operator insertions. We make a conjecture for the Grassmannian integral representation for such objects and verify our conjecture on several examples. It is remarkable that in our formulation one can consider situation when on-shell particles are not present at all, i.e. we have Grassmannian integral representation for purely off-shell object. In addition we show that off-shell amplitude with arbitrary number of off-shell gluons could be also obtained using quantum inverse scattering method for auxiliary gl(4|4) super spin chain.

  2. RMF+BCS description of N = 32 and N = 34 shell closure

    International Nuclear Information System (INIS)

    Saxena, G.; Kumawat, M.; Singh, U.K.; Jain, S.K.; Aggarwal, Mamta; Kaushik, M.; Singh, S. Somorendro

    2017-01-01

    We have employed RMF+BCS (relativistic mean-field plus BCS) approach to study N = 32 and N = 34 shell closure with the help of ground state properties of even-even nuclei. Our present investigations include single particle energies, deformations, separation energies as well as neutron and proton densities etc. Encouraged by the recent experiments showing neutron magicity at N = 32 for Ca isotopes, we have applied RMF theory with delta function pairing along with mass dependency (1/A) for full chain of N = 32 and N = 34 isotones upto drip lines. This study predicts new doubly magic nuclei specially 48 Si which is in the same mass region in 52 Ca as the recent experiments observed

  3. Inner-shell physics after fifty years of quantum mechanics

    International Nuclear Information System (INIS)

    Merzbacher, E.

    1976-01-01

    A historical view is given of how the development of quantum mechanics has been affected by the information relating to inner shells, gathered by physicists since the early days of atomic physics, and of the impact of quantum mechanics on the physics of inner atomic shells. 25 refs

  4. N=28 shell closure : shape coexistence and spin-orbit contribution

    International Nuclear Information System (INIS)

    Sarazin, Frederic

    1999-01-01

    One of the fundamental questions, which emerge from the study of nuclei far from stability, concerns the persistence of the magic character of certain configurations of protons and neutrons. From previous measurements around the N=28 magic number, it appears that this shell closure is especially weakening. In this context, a mass measurement experiment by a time of flight method around N=28 (Z 43 S in the same experiment and its interpretation by a shell model calculation confirm the analysis of the masses and constitutes the first evidence of shape coexistence around N=28. At the same time, an estimation of the evolution of the contribution of the spin-orbit coupling far from stability, partially responsible of the magic numbers sequence, showed that, although non-negligible, it is not sufficient to explain the vanishing of the shell closure. Through this study, it appeared extremely difficult to separate the contribution of the deformation from the one of the spin-orbit coupling in spectroscopic experiments. A feasibility study has thus been undertaken concerning a polarised proton and deuteron target to measure directly the evolution of the spin-orbit potential as a function of the isospin through elastic scattering experiments. (author) [fr

  5. Vacancy decay in endohedral atoms

    International Nuclear Information System (INIS)

    Amusia, M. Ya.; Baltenkov, A. S.

    2006-01-01

    It is demonstrated that the fullerene shell dramatically affects the radiative and Auger vacancy decay of an endohedral atom A-C 60 . The collectivized electrons of the C 60 shell add new possibilities for radiative and nonradiative decays similar to that in ordinary atoms where the vacancies in the initial and final state almost always belong to different subshells. It is shown that the smallness of the atomic shell radii as compared to that of the fullerene shell provides an opportunity to derive the simple formulas for the probabilities of the electron transitions. It is shown that the radiative and Auger (or Koster-Kronig) widths of the vacancy decay due to electron transition in the atom A in A-C 60 acquire an additional factor that can be expressed via the polarizability of the C 60 at transition energy. It is demonstrated that due to an opening of the nonradiative decay channel for vacancies in subvalent subshells the decay probability increases by five to six orders of magnitude

  6. Density Functional Theory of Open-Shell Systems. The 3d-Series Transition-Metal Atoms and Their Cations.

    Science.gov (United States)

    Luo, Sijie; Averkiev, Boris; Yang, Ke R; Xu, Xuefei; Truhlar, Donald G

    2014-01-14

    The 3d-series transition metals (also called the fourth-period transition metals), Sc to Zn, are very important in industry and biology, but they provide unique challenges to computing the electronic structure of their compounds. In order to successfully describe the compounds by theory, one must be able to describe their components, in particular the constituent atoms and cations. In order to understand the ingredients required for successful computations with density functional theory, it is useful to examine the performance of various exchange-correlation functionals; we do this here for 4s(N)3d(N') transition-metal atoms and their cations. We analyze the results using three ways to compute the energy of the open-shell states: the direct variational method, the weighted-averaged broken symmetry (WABS) method, and a new broken-symmetry method called the reinterpreted broken symmetry (RBS) method. We find the RBS method to be comparable in accuracy with the WABS method. By examining the overall accuracy in treating 18 multiplicity-changing excitations and 10 ionization potentials with the RBS method, 10 functionals are found to have a mean-unsigned error of systems, the M06-L functional is the most accurate. And by combining the results with our previous studies of p-block and 4d-series elements as well as databases for alkyl bond dissociation, main-group atomization energies, and π-π noncovalent interactions, we find five functionals, namely, PW6B95, MPW1B95, M08-SO, SOGGA11-X, and MPWB1K, to be highly recommended. We also studied the performance of PW86 and C09 exchange functionals, which have drawn wide interest in recent studies due to their claimed ability to reproduce Hartree-Fock exchange at long distance. By combining them with four correlation functionals, we find the performance of the resulting functionals disappointing both for 3d transition-metal chemistry and in broader tests, and thus we do not recommend PW86 and C09 as components of generalized

  7. Intruder states at the N=20 shell closure

    International Nuclear Information System (INIS)

    Heyde, K.

    1991-01-01

    It is indicated that mp-mh (multiple) excitations across closed shells can occur at low energy throughout the nuclear mass region. Besides the 4p-4h, 8p-8h configurations, that are deformed, coexisting low-lying excitations are mainly observed for light N=Z nuclei. A new class of 2p-2h intruder O + state is shown to exist in nuclei where a neutron excess is present. In the latter cases, the proton-neutron interaction energy between the excited 2p-2h configuration and the open shell accounts for a very specific mass dependence in the intruder excitation energy. The experimental evidence that corroborates the idea of intruder states will be given. (G.P.) 28 refs.; 13 figs

  8. Interaction of GaN epitaxial layers with atomic hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Losurdo, M.; Giangregorio, M.M.; Capezzuto, P.; Bruno, G.; Namkoong, G.; Doolittle, W.A.; Brown, A.S

    2004-08-15

    GaN surface passivation processes are still under development and among others hydrogen treatments are investigated. In this study, we use non-destructive optical and electrical probes such as spectroscopic ellipsometry (SE) and surface potential Kelvin probe microscopy (SP-KPM) in conjunction with non-contact atomic force microscopy (AFM) for the study of the different reactivity of Ga-polar and N-polar GaN epitaxial layers with atomic hydrogen. The GaN epitaxial layers are grown by molecular beam epitaxy on sapphire (0 0 0 1) substrates, and GaN and AlN buffer layers are used to grow N-polar and Ga-polar films, respectively. The atomic hydrogen is produced by a remote rf (13.56 MHz) H{sub 2} plasma in order to rule out any ion bombardment of the GaN surface and make the interaction chemical. It is found that the interaction of GaN surfaces with atomic hydrogen depends on polarity, with N-polar GaN exhibiting greater reactivity. Furthermore, it is found that atomic hydrogen is effective in the passivation of grain boundaries and surface defects states.

  9. Interaction of GaN epitaxial layers with atomic hydrogen

    International Nuclear Information System (INIS)

    Losurdo, M.; Giangregorio, M.M.; Capezzuto, P.; Bruno, G.; Namkoong, G.; Doolittle, W.A.; Brown, A.S.

    2004-01-01

    GaN surface passivation processes are still under development and among others hydrogen treatments are investigated. In this study, we use non-destructive optical and electrical probes such as spectroscopic ellipsometry (SE) and surface potential Kelvin probe microscopy (SP-KPM) in conjunction with non-contact atomic force microscopy (AFM) for the study of the different reactivity of Ga-polar and N-polar GaN epitaxial layers with atomic hydrogen. The GaN epitaxial layers are grown by molecular beam epitaxy on sapphire (0 0 0 1) substrates, and GaN and AlN buffer layers are used to grow N-polar and Ga-polar films, respectively. The atomic hydrogen is produced by a remote rf (13.56 MHz) H 2 plasma in order to rule out any ion bombardment of the GaN surface and make the interaction chemical. It is found that the interaction of GaN surfaces with atomic hydrogen depends on polarity, with N-polar GaN exhibiting greater reactivity. Furthermore, it is found that atomic hydrogen is effective in the passivation of grain boundaries and surface defects states

  10. Atomic physics at high brilliance synchrotron sources: Proceedings

    International Nuclear Information System (INIS)

    Berry, G.; Cowan, P.; Gemmell, D.

    1994-08-01

    This report contains papers on the following topics: present status of SPring-8 and the atomic physics undulator beamline; recent photoabsorption measurements in the rare gases and alkalis in the 3 to 15 keV proton energy region; atomic and molecular physics at LURE; experiments on atoms, ions and small molecules using the new generation of synchrotron radiation sources; soft x-ray fluorescence spectroscopy using tunable synchrotron radiation; soft x-ray fluorescence spectroscopy excited by synchrotron radiation: Inelastic and resonant scattering near threshold; outer-shell photoionization of ions; overview of the APS BESSRC beamline development; the advanced light source: Research opportunities in atomic and molecular physics; Photoionization of the Ba + ion by 4d shell excitation; decay dynamics of inner-shell excited atoms and molecules; absorption of atomic Ca, Cr, Mn and Cu; High-resolution photoelectron studies of resonant molecular photoionization; radiative and radiationless resonant raman scattering by synchrotron radiation; auger spectrometry of atoms and molecules; some thoughts of future experiments with the new generation of storage rings; Electron spectroscopy studies of argon K-shell excitation and vacancy cascades; ionization of atoms by high energy photons; ion coincidence spectroscopy on rare gas atoms and small molecules after photoexcitation at energies of several keV; an EBIS for use with synchrotron radiation photoionization of multiply charged ions and PHOBIS; gamma-2e coincidence measurements the wave of the future in inner-shell electron spectroscopy; recoil momentum spectroscopy in ion-atom and photon-atom collisions; a study of compton ionization of helium; future perspectives of photoionization studies at high photon energies; and status report on the advanced photon source. These papers have been cataloged separately elsewhere

  11. Evolution of L -shell photoabsorption of the molecular-ion series Si Hn + (n =1 ,2 ,3 ): Experimental and theoretical studies

    Science.gov (United States)

    Kennedy, E. T.; Mosnier, J.-P.; van Kampen, P.; Bizau, J.-M.; Cubaynes, D.; Guilbaud, S.; Carniato, S.; Puglisi, A.; Sisourat, N.

    2018-04-01

    We report on complementary laboratory and theoretical investigations of the 2 p photoexcitation cross sections for the molecular-ion series Si Hn + (n =1 ,2 ,3 ) near the L -shell threshold. The experiments used an electron cyclotron resonance (ECR) plasma molecular-ion source coupled with monochromatized synchrotron radiation in a merged-beam configuration. For all three molecular ions, the S i2 + decay channel appeared dominant, suggesting similar electronic and nuclear relaxation patterns involving resonant Auger and dissociation processes, respectively. The total yields of the S i2 + products were recorded and put on absolute cross-section scales by comparison with the spectrum of the S i+ parent atomic ion. Interpretation of the experimental spectra ensued from a comparison with total photoabsorption cross-sectional profiles calculated using ab initio configuration interaction theoretical methods inclusive of vibrational dynamics and contributions from inner-shell excitations in both ground and valence-excited electronic states. The spectra, while broadly similar for all three molecular ions, moved towards lower energies as the number of screening hydrogen atoms increased from one to three. They featured a wide and shallow region below ˜107 eV due to 2 p →σ* transitions to dissociative states, and intense and broadened peaks in the ˜107 -113 -eV region merging into sharp Rydberg series due to 2 p →n δ ,n π transitions converging on the LII ,III limits above ˜113 eV . This overall spectral shape is broadly replicated by theory in each case, but the level of agreement does not extend to individual resonance structures. In addition to the fundamental interest, the work should also prove useful for the understanding and modeling of astronomical and laboratory plasma sources where silicon hydride molecular species play significant roles.

  12. Off-shell N = 2 tensor supermultiplets

    International Nuclear Information System (INIS)

    Wit, Bernard de; Saueressig, Frank

    2006-01-01

    A multiplet calculus is presented for an arbitrary number n of N = 2 tensor supermultiplets. For rigid supersymmetry the known couplings are reproduced. In the superconformal case the target spaces parametrized by the scalar fields are cones over (3n-1)-dimensional spaces encoded in homogeneous SU(2) invariant potentials, subject to certain constraints. The coupling to conformal supergravity enables the derivation of a large class of supergravity Lagrangians with vector and tensor multiplets and hypermultiplets. Dualizing the tensor fields into scalars leads to hypermultiplets with hyperkaehler or quaternion-Kaehler target spaces with at least n abelian isometries. It is demonstrated how to use the calculus for the construction of Lagrangians containing higher-derivative couplings of tensor multiplets. For the application of the c-map between vector and tensor supermultiplets to Lagrangians with higher-order derivatives, an off-shell version of this map is proposed. Various other implications of the results are discussed. As an example an elegant derivation of the classification of 4-dimensional quaternion-Kaehler manifolds with two commuting isometries is given

  13. Synthesis of N-halamine-functionalized silica-polymer core-shell nanoparticles and their enhanced antibacterial activity

    International Nuclear Information System (INIS)

    Dong, Alideertu; Wang Tao; Xiao Linghan; Wang Weiwei; Zhao Tianyi; Zheng Xin; Liu Fengqi; Gao Ge; Huang Jinfeng; Chen Yuxin; Lan Shi

    2011-01-01

    N-halamine-functionalized silica-polymer core-shell nanoparticles with enhanced antibacterial activity were synthesized through the encapsulation of silica nanoparticles as support with polymeric N-halamine. The as-synthesized nanoparticles were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive x-ray spectrometry (EDX), dynamic light scattering (DLS), thermogravimetric analysis (TGA), and Fourier transform infrared (FTIR). These N-halamine-functionalized silica-polymer core-shell nanoparticles displayed powerful antibacterial performance against both Gram-positive bacteria and Gram-negative bacteria, and their antibacterial activities have been greatly improved compared with their bulk counterparts. Therefore, these N-halamine-functionalized silica-polymer core-shell nanoparticles have the potential for various significant applications such as in medical devices, healthcare products, water purification systems, hospitals, dental office equipment, food packaging, food storage, household sanitation, etc.

  14. Synthesis of N-halamine-functionalized silica-polymer core-shell nanoparticles and their enhanced antibacterial activity

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Alideertu; Wang Tao; Xiao Linghan; Wang Weiwei; Zhao Tianyi; Zheng Xin; Liu Fengqi; Gao Ge [College of Chemistry, Jilin University and MacDiarmid Laboratory, Changchun 130021 (China); Huang Jinfeng; Chen Yuxin [Key Laboratory for Molecular Enzymology and Engineering of the Ministry of Education, Jilin University, Changchun 130012 (China); Lan Shi, E-mail: gaoge@jlu.edu.cn [College of Chemistry and Chemical Engineering, Inner Mongolia University for the Nationalities, Tongliao 028000 (China)

    2011-07-22

    N-halamine-functionalized silica-polymer core-shell nanoparticles with enhanced antibacterial activity were synthesized through the encapsulation of silica nanoparticles as support with polymeric N-halamine. The as-synthesized nanoparticles were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive x-ray spectrometry (EDX), dynamic light scattering (DLS), thermogravimetric analysis (TGA), and Fourier transform infrared (FTIR). These N-halamine-functionalized silica-polymer core-shell nanoparticles displayed powerful antibacterial performance against both Gram-positive bacteria and Gram-negative bacteria, and their antibacterial activities have been greatly improved compared with their bulk counterparts. Therefore, these N-halamine-functionalized silica-polymer core-shell nanoparticles have the potential for various significant applications such as in medical devices, healthcare products, water purification systems, hospitals, dental office equipment, food packaging, food storage, household sanitation, etc.

  15. K-shell-hole production, multiple-hole production, charge transfer, and antisymmetry

    International Nuclear Information System (INIS)

    Reading, J.F.; Ford, A.L.

    1980-01-01

    In calculating K-shell-hole production when an ion collides with an atom, account must be taken of the fact that processes involving electrons other than the K-shell electron can occur. For example, after making a K-shell hole an L-shell electron may be knocked into it, or an L-shell vacancy may be produced and the K-shell electron promoted to that vacancy in the ''Fermi sea'' of the target-atom orbitals. In 1973 a theorem was proved by one of the present authors demonstrating that all these multielectron processes cancel in an independent-particle model for the target atom. In this paper it is shown that the same thing occurs for hole production by charge transfer to the ion. The authors demonstrate that multihole production does not obey this simple rule and that the probability for multihole production is not the product of independent single-electron probabilities. The correct expressions that should be used for these processes are given, together with new results for charge-transfer processes accompanied by hole production

  16. High-precision mass measurements in the realm of the deformed shell closure N=152

    Energy Technology Data Exchange (ETDEWEB)

    Eibach, Martin Andreas

    2013-12-04

    The nuclear masses reflect the sum of all interactions inside a nucleus. Their precise knowledge can be used to benchmark nuclear mass models and to gain nuclear structure information. Penning-trap mass spectrometers have proven their potential to obtain lowest uncertainties. Uniquely located at a nuclear reactor, the double Penning-trap mass spectrometer TRIGA-TRAP is dedicated to measurements in the neutron-rich region. For a gain in sensitivity a non-destructive detection system for single ion mass measurements was adopted. This includes the implementation of a narrow band-pass filter tuned to the heavy ion cyclotron frequency as well as a cryogenic low-noise amplifier. For on-line mass measurements, the laser ablation ion source was equipped with a newly developed miniature radiofrequency quadrupole trap in order to improve the extraction efficiency. A more economic use of the radioactive material enabled mass measurements using only 10{sup 15} atoms of target material. New mass measurements were performed within this work in the realm of the deformed shell closure N=152. Their implementation into the atomic-mass evaluation improved the uncertainty of more than 80 nuclides in the heavy mass region and simultaneously shifted the absolute mass of two α decay chains.

  17. Transnitrosation of alicyclic N-nitrosamines containing a sulfur atom.

    Science.gov (United States)

    Inami, Keiko; Kondo, Sonoe; Ono, Yuta; Saso, Chiharu; Mochizuki, Masataka

    2013-12-15

    Aromatic and aliphatic nitrosamines are known to transfer a nitrosonium ion to another amine. The transnitrosation of alicyclic N-nitroso compounds generates S-nitrosothiols, which are potential nitric oxide donors in vivo. In this study, certain alicyclic N-nitroso compounds based on non-mutagenic N-nitrosoproline or N-nitrosothioproline were synthesised, and the formation of S-nitrosoglutathione (GSNO) was quantified under acidic conditions. We then investigated the effect of a sulfur atom as the substituent and as a ring component on the GSNO formation. In the presence of thiourea under acidic conditions, GSNO was formed from N-nitrosoproline and glutathione, and an N-nitroso compound containing a sulfur atom and glutathione produced GSNO without thiourea. The quantity of GSNO derived from the reaction of the N-nitrosamines containing a sulfur atom and glutathione was higher than that from the N-nitrosoproline and glutathione plus thiourea. Among the analogues that contained a sulfur atom either in the ring or as a substituent, the thiazolidines produced a slightly higher quantity of GSNO than the analogue with a thioamide group. A compound containing sulfur atoms both in the ring and as a substituent exhibited the highest activity for GSNO formation among the alicyclic N-nitrosamines tested. The results indicate that the intramolecular sulfur atom plays an important role in the transnitrosation via alicyclic N-nitroso compounds to form GSNO. Crown Copyright © 2013. Published by Elsevier Ltd. All rights reserved.

  18. X-ray core states, atomic size and Moseley's law

    International Nuclear Information System (INIS)

    Smith, D.Y.; Karstens, William

    2000-01-01

    Vinti's dipolar sum-rule for the spatial extent of quantum states was tested on atomic K-shell and ns valence states. Agreement between radii derived from absorption spectra and from atomic-structure calculations is excellent, provided Pauli-principle-prohibited transitions are accounted for. These many-electron corrections to the single-electron sum-rule contributed less than 20% to the radii, which supports application of single-electron rules to electron-excess defects as a first approximation. We found the oscillator strength for K-shell excitations decreases rapidly with atomic number because of strength transfer to higher-lying p states. Hence, K-shell contributions to radiation damage decrease with increasing atomic number. A new interpretation of Moseley's law for the X-ray K edge in terms of K-shell radii is described

  19. An off-shell formulation of N=4 supersymmetric Yang-Mills theory in twistor harmonic superspace

    International Nuclear Information System (INIS)

    Sokatchev, E.

    1989-01-01

    Twistor-like harmonic variables which parametrize the coset space SO(1, 4)/SO(1, 2)xSO(2) are introduced. With their help the on-shell constraints for N=4, d=5 supersymmetric Yang-Mills theory are rewritten as conditions for flatness in the harmonic directions of superspace. A Chern-Simons off-shell action leading to those equations is proposed. There are indications that the off-shell theory might be finite, despite the fact that the on-shell one seems non-renormalizable. (orig.)

  20. Nanomechanics of biocompatible hollow thin-shell polymer microspheres.

    Science.gov (United States)

    Glynos, Emmanouil; Koutsos, Vasileios; McDicken, W Norman; Moran, Carmel M; Pye, Stephen D; Ross, James A; Sboros, Vassilis

    2009-07-07

    The nanomechanical properties of biocompatible thin-shell hollow polymer microspheres with approximately constant ratio of shell thickness to microsphere diameter were measured by nanocompression tests in aqueous conditions. These microspheres encapsulate an inert gas and are used as ultrasound contrast agents by releasing free microbubbles in the presence of an ultrasound field as a result of free gas leakage from the shell. The tests were performed using an atomic force microscope (AFM) employing the force-distance curve technique. An optical microscope, on which the AFM was mounted, was used to guide the positioning of tipless cantilevers on top of individual microspheres. We performed a systematic study using several cantilevers with spring constants varying from 0.08 to 2.3 N/m on a population of microspheres with diameters from about 2 to 6 microm. The use of several cantilevers with various spring constants allowed a systematic study of the mechanical properties of the microsphere thin shell at different regimes of force and deformation. Using thin-shell mechanics theory for small deformations, the Young's modulus of the thin wall material was estimated and was shown to exhibit a strong size effect: it increased as the shell became thinner. The Young's modulus of thicker microsphere shells converged to the expected value for the macroscopic bulk material. For high applied forces, the force-deformation profiles showed a reversible and/or irreversible nonlinear behavior including "steps" and "jumps" which were attributed to mechanical instabilities such as buckling events.

  1. Preparation of n-tetradecane-containing microcapsules with different shell materials by phase separation method

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Rui [Department of Chemical Engineering, Tsinghua University, Beijing (China); Zhang, Yan; Zhang, Qingwu [Department of Chemical Engineering, China University of Mining and Technology, Beijing (China); Wang, Xin; Zhang, Yinping [Department of Building Science, Tsinghua University, Beijing (China)

    2009-10-15

    Microcapsules for thermal energy storage and heat-transfer enhancement have attracted great attention. Microencapsulation of n-tetradecane with different shell materials was carried out by phase separation method in this paper. Acrylonitrile-styrene copolymer (AS), acrylonitrile-styrene-butadiene copolymer (ABS) and polycarbonate (PC) were used as the shell materials. The structures, morphologies and the thermal capacities of the microcapsules were characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The ternary phase diagrams showed the potential encapsulation capabilities of the three shell materials. The effects of the shell/core ratio and the molecular weight of the shell material on the encapsulation efficiency and the thermal capacity of the microcapsules were also discussed. Microcapsules with melting enthalpy > 100 J/g, encapsulation efficiency 66-75%, particle size<1 {mu}m were obtained for all three shell materials. (author)

  2. Study of the N=40 shell by using Coulomb excitation; Etude par excitation coulombienne de la fermeture de couche N=40

    Energy Technology Data Exchange (ETDEWEB)

    Leenhardt, St

    2000-01-01

    Two Coulomb excitation experiments on neutron rich exotic nuclei have been performed at GANIL. They allowed the measurement of the reduced transition probability B(E2) (from ground state to first excited state) of some nuclei around N = 40. This number, 40, is a half-magic number in the shell model. For nuclei with an important neutron excess, it is predicted that the shell closure is stronger at N = 40. The B(E2) is a good tool for testing this growing. We have measured, by using the LISE3 spectrometer and a {gamma} multidetector, B(E2) of {sup 68}Ni, {sup 66}Ni and {sup 72}Zn, unknown till now. We have used for the first time segmented germanium 'clovers' detector, for photon detection (v/c{approx}0.3). Results confirm the strong shell effect for {sup 68}Ni. Indeed {sup 68}Ni was shown to be the Nickel isotope with the lowest value of B(E2), and hence the most rigid isotope. Nevertheless it seems that the shell effect at N = 40 decreases rapidly, for other isotopes very close to {sup 68}Ni(Z = 28) and N = 40). (authors)

  3. Coulomb excitation of neutron-rich nuclei between the N=40 and N=50 shell gaps using REX-ISOLDE and the Ge MINIBALL array

    CERN Multimedia

    2002-01-01

    We propose to perform Coulomb excitation experiments of neutron-rich nuclei in the vicinity of $^{68}$Ni towards $^{78}$Ni using the REX-ISOLDE facility coupled with the highly efficient MINIBALL array. Major changes in the structure of the atomic nucleus are expected around the N = 40 subshell closure. Recent B(E2) measurements suggested that $^{68}$Ni behaves like a doubly magic nucleus while neutron-rich Zn isotopes with N>38 exhibit a sudden increase of B(E2) values which may be the signature of deformation. We would like to check and test these predictions for neutron-rich nuclei in the vicinity of N = 40 and N = 50 shell closures like $^{72}$Zn, $^{74}$Zn, $^{76}$Zn, $^{68}$Ni, $^{70}$Ni. Our calculations show that an energy upgrade from 2.2 to 3 MeV/nucleon will be of crucial importance for a part of our study while some nuclei can still be very efficiently studied at an energy of 2.2 MeV/nucleon. Therefore, to perform our experiment in an efficient way, we request 21 shifts of beam time before the ene...

  4. High-precision mass measurements of nickel, copper, and gallium isotopes and the purported shell closure at N=40

    International Nuclear Information System (INIS)

    Guenaut, C.; Audi, G.; Beck, D.

    2007-01-01

    High-precision mass measurement of more than thirty neutron-rich nuclides around the Z=28 closed proton shell were performed with the triple-trap mass spectrometer ISOLTRAP at ISOLDE/CERN to address the question of a possible neutron shell closure at N=40. The results for 57,60,64-69 Ni, 65-74,76 Cu (Z=29), and 63-65,68-78 Ga (Z=31), have a relative uncertainty of the order of 10 -8 . In particular, the masses of 72-74,76 Cu have been measured for the first time. We analyse the resulting mass surface for signs of magicity, comparing the behavior of N=40 to that of known magic numbers and to mid-shell behavior. Contrary to nuclear spectroscopy studies, no indications of a shell or sub-shell closure are found for N=40. (authors)

  5. Study of the closure of the nuclear shells N = 16, 20, 28 and 40

    International Nuclear Information System (INIS)

    Sorlin, O.

    2005-12-01

    There are 2 types of nuclear shell closures: one is associated to a number of the harmonic oscillator, typically N = 20 and 40, and the other is a consequence of the spin-orbital interaction that produces magic numbers such as N = 28, 50, 82 and N = 126. The first part of this work deals with the knowledge accumulated around the closure of the N = 28 shell. 3 means of investigation have been used: -) the study of beta decay nuclei (K 47 , Ar 46 , S 44 , Si 42 and Cl 45 ), -) the on-line spectroscopy of nuclei around N = 28, and -) the study of Ar 45 and Ar 47 through transfer reactions. The second part is dedicated to results concerning the nuclear structure of nuclei around N = 14-20 and around N = 40. (A.C.)

  6. Self-assembly fabrication of microencapsulated n-octadecane with natural silk fibroin shell for thermal-regulating textiles

    International Nuclear Information System (INIS)

    Zhao, Liang; Luo, Jie; Wang, Hao; Song, Guolin; Tang, Guoyi

    2016-01-01

    Highlights: • Microencapsulated n-octadecane with silk fibroin shell was fabricated. • The microcapsules show high heat storage capability. • The microcapsules are good candidate for thermal-regulating textiles. - Graphical Abstract: Display Omitted - Abstract: Novel microencapsulated n-octadecane with natural silk fibroin (SF) shell was prepared using a self-assembly method in oil-in-water (o/w) emulsion. The microstructures and chemical compositions of the resultant microcapsules were investigated by scanning electronic microscope (SEM) and Fourier transformation infrared spectroscope (FT-IR). SEM images demonstrated that the microcapsules presented spherical shape with a median size of 4–5 µm. FT-IR results confirmed that SF shell was successfully fabricated upon n-octadecane core. According to the DSC and TGA examinations, the resultant microcapsules exhibited good phase-change performance, high thermal-storage capability and high thermal reliability. The microencapsulated n-octadecane with SF shell synthesized in the present study would be a potential candidate for the application of thermal-regulating textiles or fibers and biological medical materials, etc.

  7. Teleporting N-qubit unknown atomic state by utilizing the V-type three-level atom

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Realizing the teleportation of quantum state, especially the teleportation of N-qubit quantum state, is of great importance in quantum information. In this paper, Raman-interaction of the V-type degenerate three-level atom and single-mode cavity field is studied by utilizing complete quantum theory. Then a new scheme for teleporting N-qubit unknown atomic state via Raman-interaction of the V-type degenerate three-level atom with a single-mode cavity field is proposed, which is based upon the complete quantum theory mentioned above.

  8. An equations of motion approach for open shell systems

    International Nuclear Information System (INIS)

    Yeager, D.L.; McKoy, V.

    1975-01-01

    A straightforward scheme is developed for extending the equations of motion formalism to systems with simple open shell ground states. Equations for open shell random phase approximation (RPA) are given for the cases of one electron outside of a closed shell in a nondegenerate molecular orbital and for the triplet ground state with two electrons outside of a closed shell in degenerate molecular orbitals. Applications to other open shells and extension of the open shell EOM to higher orders are both straightforward. Results for the open shell RPA for lithium atom and oxygen molecule are given

  9. Synthesis of bimetallic Pt-Pd core-shell nanocrystals and their high electrocatalytic activity modulated by Pd shell thickness

    Science.gov (United States)

    Li, Yujing; Wang, Zhi Wei; Chiu, Chin-Yi; Ruan, Lingyan; Yang, Wenbing; Yang, Yang; Palmer, Richard E.; Huang, Yu

    2012-01-01

    Bimetallic Pt-Pd core-shell nanocrystals (NCs) are synthesized through a two-step process with controlled Pd thickness from sub-monolayer to multiple atomic layers. The oxygen reduction reaction (ORR) catalytic activity and methanol oxidation reactivity of the core-shell NCs for fuel cell applications in alkaline solution are systematically studied and compared based on different Pd thickness. It is found that the Pd shell helps to reduce the over-potential of ORR by up to 50mV when compared to commercial Pd black, while generating up to 3-fold higher kinetic current density. The carbon monoxide poisoning test shows that the bimetallic NCs are more resistant to the CO poisoning than Pt NCs and Pt black. It is also demonstrated that the bimetallic Pt-Pd core-shell NCs can enhance the current density of the methanol oxidation reaction, lowering the over-potential by 35 mV with respect to the Pt core NCs. Further investigation reveals that the Pd/Pt ratio of 1/3, which corresponds to nearly monolayer Pd deposition on Pt core NCs, gives the highest oxidation current density and lowest over-potential. This study shows for the first time the systematic investigation of effects of Pd atomic shells on Pt-Pd bimetallic nanocatalysts, providing valuable guidelines for designing high-performance catalysts for fuel cell applications.Bimetallic Pt-Pd core-shell nanocrystals (NCs) are synthesized through a two-step process with controlled Pd thickness from sub-monolayer to multiple atomic layers. The oxygen reduction reaction (ORR) catalytic activity and methanol oxidation reactivity of the core-shell NCs for fuel cell applications in alkaline solution are systematically studied and compared based on different Pd thickness. It is found that the Pd shell helps to reduce the over-potential of ORR by up to 50mV when compared to commercial Pd black, while generating up to 3-fold higher kinetic current density. The carbon monoxide poisoning test shows that the bimetallic NCs are more

  10. Localized hole effects in inner-shell excitation

    International Nuclear Information System (INIS)

    Rescigno, T.N.; Orel, A.E.

    1983-01-01

    Ab initio calculations of valence shell ionization potentials have shown that orbital relaxation and correlation differences usually make contributions of comparable magnitude. In marked contrast to this observation is the situation for deep core ionization, where correlation differences (approx. 1 eV) play a relatively minor role compared to orbital relaxation (approx. 20 eV). Theoretical calculations have shown that this relaxation is most easily described if the 1s-vacancy created by a K-shell excitation is allowed to localize on one of the atomic centers. For molecules possessing a center of inversion, this means that the molecular orbitals that best describe the final state do not transform as any irreducible representation of the molecular point group. Recent experimental work by Shaw, King, Read and Cvejanovic and by Stefani and coworkers has prompted us to carry out further calculations on N 2 , as well as analogous investigations of 1s/sub N/ → π* excitation in NO and N 2 O. The generalized oscillator strengths display a striking similarity and point to the essential correctness of the localized hole picture for N 2 . The theoretical calculations are briefly described, followed by a summary of the results and comparison to experiment, followed by a short discussion

  11. Photoionization of atoms. Progress report, 1 April 1979-30 March 1980

    International Nuclear Information System (INIS)

    Samson, J.A.R.; Starace, A.F.

    1979-12-01

    A strong 304 A fluorescent signal from He + (n = 2) has been observed as a function of incident photon wavelength; strong autoionizing structure arising from 3n + states are seen in the spectrum. Measurements of the ratio of photoproduced Ne + ions to Ne 2+ ions indicate that further calibration of detector response is required. The dissociative photoionization of O 2 has been measured successfully as a necessary preliminary to measuring the photoionization cross section of atomic oxygen. The experimental apparatus has been built to measure the photoelectron angular distribution of atomic cesium. In order to measure rare gas photoionization cross sections to +-1% accuracy, a new gas tight window has been developed and second order lines in the laboratory light sources have been classified. A new random phase approximation (RPA) for the theoretical calculation of open- or closed-shell atom photoionization cross sections has been developed; the close-coupling approximation and the closed-shell atom RPA of Chang and Fano are limiting cases of a new set of coupled differential equations. The Rydberg energy spectrum and oscillator strengths of atomic hydrogen have been calculated for magnetic fields of order 10 5 Gauss using a basis of oblate spheroidal angle functions. Below N approx. = 12 an adiabatic approximation is excellent. Above n approx. = 12 non-adiabatic coupling terms rapidly become important, and the perturbed energy levels for n greater than or equal to 16 cross, indicating quasi-conserved dynamical symmetries. A previous calculation of the cesium 6s → epsilon p photoionization cross section has been extended to include interchannel coupling to the 5p → epsilon d photoionization channels; above the near threshold cross section minimum, the cross section is dominated by 5p → 5d resonance transitions

  12. Challenges to the Application of δ15N measurements of the organic fraction of archaeological and fossil mollusk shells to assess paleoenvironmental change.

    Science.gov (United States)

    Andrus, C. F. T.

    2015-12-01

    Nitrogen isotope analysis of the organic fraction of mollusk shells is beginning to be applied to questions of past anthropogenic and natural environmental variation using samples from archaeological and fossil deposits. Fairly extensive proxy validation research has been conducted in the past decade, documenting the relationship between the δ15N of ambient particulate organic matter, mollusk soft tissues, and shell organic matrix. However, comparatively little research has addressed the potential effects of taphonomy and diagenesis on these proxy records. Assessing archaeological samples are especially complex in that humans may have transported and/or cooked shell prior to deposition. Shell δ15N data will be presented from modern and archaeological oyster (Crassostrea virginica) and clam shell (Mercenaria spp.) of various late Holocene ages and late Cretaceous Crassatellites vadosus shells. Archaeological shells show some loss of organic matter over time, yet some Cretaceous shells retain enough matrix to permit δ15N analysis. The Cretaceous samples required concentration of the remaining organic matrix by removing carbonate via acid pretreatment prior to EA-IRMS analysis, but modern and archaeological shells had sufficient organic matrix to permit analysis without acid pretreatment. The δ15N data from the archaeological shells do not display obvious alteration from the loss of organic matrix. The results of cooking experiments performed on modern oyster shells also indicate little alteration of δ15N values, unless the shell was heated to the point of disintegration. While these experiments indicate promise for the application of δ15N analysis of shell organic matter, the results are incomplete and lack ideal control over initial δ15N values in ancient samples used for comparisons. Future research, perhaps focused on compound-specific δ15N analysis and additional controlled experiments on moderns shells, may improve this assessment.

  13. Single-quantum annihilation of positrons with shell-bound atomic electrons

    International Nuclear Information System (INIS)

    Palathingal, J.C.; Asoka-Kumar, P.; Lynn, K.G.; Posada, Y.; Wu, X.Y.

    1991-01-01

    The single-quantum annihilation of positrons has been studied experimentally with a positron beam and a thin lead target, at energies 1 MeV and higher. Spectral peaks corresponding to the K, L, and M shells have been resolved and observed distinctly for the first time. The shell ratios L/K and M/K have been determined. An analysis of the L peak has yielded the (LII+LIII)/L ratio. The first measurements of the directional distributions of the annihilation quanta of the three individual electron shells are also reported. The results are in agreement with theory. They also point out the potential for applying the phenomena to the development of a tunable, highly directional gamma-ray source

  14. Atomic nucleus and elementary particles

    International Nuclear Information System (INIS)

    Zakrzewski, J.

    1976-01-01

    Negatively charged leptons and hadrons can be incorporated into atomic shells forming exotic atoms. Nucleon resonances and Λ hyperons can be considered as constituents of atomic nuclei. Information derived from studies of such exotic systems enriches our knowledge of both the interactions of elementary particles and of the structure of atomic nuclei. (author)

  15. Synthesis and detection the oxidization of Co cores of Co@SiO2 core-shell nanoparticles by in situ XRD and EXAFS.

    Science.gov (United States)

    Zhang, Kunhao; Zhao, Ziyan; Wu, Zhonghua; Zhou, Ying

    2015-01-01

    In this paper, the Co@SiO2 core-shell nanoparticles were prepared by the sol-gel method. The oxidization of Co core nanoparticles was studied by the synchrotron radiation-based techniques including in situ X-ray diffraction (XRD) and X-ray absorption fine structure (XAFS) up to 800°C in air and N2 protection conditions, respectively. It was found that the oxidization of Co cores is undergoing three steps regardless of being in air or in N2 protection condition. In the first step ranging from room temperature to 200°C, the Co cores were dominated by Co(0) state as well as small amount of Co(2+) ions. When temperature was above 300°C, the interface between Co cores and SiO2 shells was gradually oxidized into Co(2+), and the CoO layer was observed. As the temperature increasing to 800°C, the Co cores were oxidized to Co3O4 or Co3O4/CoO. Nevertheless, the oxidization kinetics of Co cores is different for the Co@SiO2 in air and N2 gas conditions. Generally, the O2 in the air could get through the SiO2 shells easily onto the Co core surface and induce the oxidization of the Co cores due to the mesoporous nature of the SiO2 shells. However, in N2 gas condition, the O atoms can only be from the SiO2 shells, so the diffusion effect of O atoms in the interface between Co core and SiO2 shell plays a key role.

  16. Molecular dynamics study of the interactions of incident N or Ti atoms with the TiN(001) surface

    International Nuclear Information System (INIS)

    Xu, Zhenhai; Zeng, Quanren; Yuan, Lin; Qin, Yi; Chen, Mingjun; Shan, Debin

    2016-01-01

    Graphical abstract: - Highlights: • Interactions of incident N or Ti atoms with TiN(001) surface are studied by CMD. • The impact position of incident N on the surface determines the interaction modes. • Adsorption could occur due to the atomic exchange process. • Resputtering and reflection may simultaneously occur. • The initial sticking coefficient of N on TiN(001) is much smaller than that of Ti. - Abstract: The interaction processes between incident N or Ti atoms and the TiN(001) surface are simulated by classical molecular dynamics based on the second nearest-neighbor modified embedded-atom method potentials. The simulations are carried out for substrate temperatures between 300 and 700 K and kinetic energies of the incident atoms within the range of 0.5–10 eV. When N atoms impact against the surface, adsorption, resputtering and reflection of particles are observed; several unique atomic mechanisms are identified to account for these interactions, in which the adsorption could occur due to the atomic exchange process while the resputtering and reflection may simultaneously occur. The impact position of incident N atoms on the surface plays an important role in determining the interaction modes. Their occurrence probabilities are dependent on the kinetic energy of incident N atoms but independent on the substrate temperature. When Ti atoms are the incident particles, adsorption is the predominant interaction mode between particles and the surface. This results in the much smaller initial sticking coefficient of N atoms on the TiN(001) surface compared with that of Ti atoms. Stoichiometric TiN is promoted by N/Ti flux ratios larger than one.

  17. One-dimensional σ-models with N = 5, 6, 7, 8 off-shell supersymmetries

    International Nuclear Information System (INIS)

    Gonzales, M.; Toppan, F.; Rojas, M.

    2008-12-01

    We computed the actions for the 1D N = 5 σ-models with respect to the two inequivalent (2, 8, 6) multiplets. 4 supersymmetry generators are manifest, while the constraint originated by imposing the 5-th supersymmetry automatically induces a full N = 8 off-shell invariance. The resulting action coincides in the two cases and corresponds to a conformally flat 2D target satisfying a special geometry of rigid type. To obtain these results we developed a computational method (for Maple 11) which does not require the notion of superfields and is instead based on the nowadays available list of the inequivalent representations of the 1D N-extended supersymmetry. Its application to systematically analyze the σ-models off-shell invariant actions for the remaining N = 5, 6, 7, 8 (k, 8, 8 - k) multiplets, as well as for the N > 8 representations, only requires more cumbersome computations. (author)

  18. Nuclear structure of the N = Z odd - odd nuclei around N=28 closed shell interpreted with IBFFM

    International Nuclear Information System (INIS)

    Dragulescu, E.; Serbanut, G. C.; Serbanut, I.

    2001-01-01

    In the very recent years the knowledge of the level structure at lower and higher energies in the fpg shell N=Z nuclei has renewed a growing interest due to major improvements in the theoretical techniques. Going away from closed shell, the shell model calculations rapidly exhaust computer capabilities and we must resort to the model observed on collective phenomena. The fpg odd-odd N = Z nuclei close to the doubly magic 56 Ni nucleus are good candidates to investigate the competition between collective and single-particle excitations. Here part of the results obtained from an exhaustive systematic study of the self conjugate doubly-odd nuclei with A > 62: 62 Ga and 66 As nuclei using the interacting - boson - fermion - fermion - model (IBFFM) is presented. The odd-odd nuclei are described in the framework of the IBFFM by coupling valence shell proton and neutron quasiparticles to even-even core described in the interacting - boson model. In the first step of the calculations the core parameters for 60 Zn and 64 Ge cores were fitted to the energies of their excited states. In the second step of calculations, we have adjusted the IBFM proton Hamiltonian to the low - lying levels of 63 Ga and 67 As nuclei and IBFM neutron Hamiltonian of low - lying levels of 61 Zn and 65 Ge nuclei involved in the cases of the structure of odd-odd 62 Ga and 66 As nuclei. We have finally calculated the level spectra and electromagnetic properties of above mentioned nuclei. The IBFFM positive - parity energy spectra are compared with experimental ones. The calculations show a reasonable agreement with experimental data and existing shell - model calculations. (authors)

  19. Short range correlations in the pion s-wave self-energy of pionic atoms

    OpenAIRE

    Salcedo, L. L.; Holinde, K.; Oset, E.; Schütz, C.

    1995-01-01

    We evaluate the contribution of second order terms to the pion-nucleus s-wave optical potential of pionic atoms generated by short range nuclear correlation. The corrections are sizeable because they involve the isoscalar s-wave $\\pi N$ amplitude for half off-shell situations where the amplitude is considerably larger than the on-shell one. In addition, the s-wave optical potential is reanalyzed by looking at all the different conventional contributions together lowest order, Pauli corrected ...

  20. Atomic many-body theory of giant resonances

    International Nuclear Information System (INIS)

    Kelly, H.P.; Altun, Z.

    1987-01-01

    In this paper the use of many-body perturbation theory (MBPT) to include effects of electron correlations is discussed. The various physical processes contributing to the broad photoionization cross sections of the rare gases are studied in terms of the relevant many-body diagrams. Use of the random phase approximation with exchange (RPAE) is discussed by Amusia and Cherepkov. Calculations using the relativistic RPAE are reviewed by Johnson. In addition, many-body perturbation theory (MBPT) is used to study resonances which are due to excitation of bound states degenerate with the continuum. Very interesting giant resonance structure can occur when an inner shell electron is excited into a vacant open-shell orbital of the same principal quantum number. A particular example which is studied is the neutral manganese atom 3p 6 3d 5 4s 2 ( 6 S), in which the spins of the five 3d electrons are aligned. A very large resonance occurs in the 3d and 4s cross sections due to 3p → 3d excitation near 51 eV, and calculations of this resonance by MBPT and RPAE are discussed. A second example of this type of resonance occurs in open-shell rare-earth atoms with configurations 4d 10 4f/sup n/5s 2 5p 6 s 2 . Calculations and experimental results will be discussed for the case of europium with a half-filled sub-shell 4f 7 . 71 references, 15 figures

  1. Potential of Transition Metal Atoms Embedded in Buckled Monolayer g-C3N4 as Single-Atom Catalysts

    KAUST Repository

    Li, Shu-Long; Kan, Xiang; Yin, Hui; Gan, Li-Yong; Schwingenschlö gl, Udo; Zhao, Yong

    2017-01-01

    We use first-principles calculations to systematically explore the potential of transition metal atoms (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, Ir, Pt, and Au) embedded in buckled monolayer g-C3N4 as single-atom catalysts. We show that clustering of Sc and Ti on g-C3N4 is thermodynamically impeded and that V, Cr, Mn, and Cu are much less susceptible to clustering than the other TM atoms under investigation. Strong bonding of the transition metal atoms in the cavities of g-C3N4 and high diffusion barriers together are responsible for single-atom fixation. Analysis of the CO oxidation process indicates that embedding of Cr and Mn in g-C3N4 gives rise to promising single-atom catalysts at low temperature.

  2. Potential of Transition Metal Atoms Embedded in Buckled Monolayer g-C3N4 as Single-Atom Catalysts

    KAUST Repository

    Li, Shu-Long

    2017-10-27

    We use first-principles calculations to systematically explore the potential of transition metal atoms (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, Ir, Pt, and Au) embedded in buckled monolayer g-C3N4 as single-atom catalysts. We show that clustering of Sc and Ti on g-C3N4 is thermodynamically impeded and that V, Cr, Mn, and Cu are much less susceptible to clustering than the other TM atoms under investigation. Strong bonding of the transition metal atoms in the cavities of g-C3N4 and high diffusion barriers together are responsible for single-atom fixation. Analysis of the CO oxidation process indicates that embedding of Cr and Mn in g-C3N4 gives rise to promising single-atom catalysts at low temperature.

  3. Luminescence and efficiency optimization of InGaN/GaN core-shell nanowire LEDs by numerical modelling

    Science.gov (United States)

    Römer, Friedhard; Deppner, Marcus; Andreev, Zhelio; Kölper, Christopher; Sabathil, Matthias; Strassburg, Martin; Ledig, Johannes; Li, Shunfeng; Waag, Andreas; Witzigmann, Bernd

    2012-02-01

    We present a computational study on the anisotropic luminescence and the efficiency of a core-shell type nanowire LED based on GaN with InGaN active quantum wells. The physical simulator used for analyzing this device integrates a multidimensional drift-diffusion transport solver and a k . p Schrödinger problem solver for quantization effects and luminescence. The solution of both problems is coupled to achieve self-consistency. Using this solver we investigate the effect of dimensions, design of quantum wells, and current injection on the efficiency and luminescence of the core-shell nanowire LED. The anisotropy of the luminescence and re-absorption is analyzed with respect to the external efficiency of the LED. From the results we derive strategies for design optimization.

  4. Cu–Ni core–shell nanoparticles: structure, stability, electronic, and magnetic properties: a spin-polarized density functional study

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Qiang, E-mail: wangqiang@njtech.edu.cn; Wang, Xinyan; Liu, Jianlan; Yang, Yanhui [Nanjing Tech University, School of Chemistry and Molecular Engineering, Institute of Advanced Synthesis (IAS) (China)

    2017-02-15

    Bimetallic core–shell nanoparticles (CSNPs) have attracted great interest not only because of their superior stability, selectivity, and catalytic activity but also due to their tunable properties achieved by changing the morphology, sequence, and sizes of both core and shell. In this study, the structure, stability, charge transfer, electronic, and magnetic properties of 13-atom and 55-atom Cu and Cu–Ni CSNPs were investigated using the density functional theory (DFT) calculations. The results show that Ni@Cu CSNPs with a Cu surface shell are more energetically favorable than Cu@Ni CSNPs with a Ni surface shell. Interestingly, three-shell Ni@Cu{sub 12}@Ni{sub 42} is more stable than two-shell Cu{sub 13}@Ni{sub 42}, while two-shell Ni{sub 13}@Cu{sub 42} is more stable than three-shell Cu@Ni{sub 12}@Cu{sub 42}. Analysis of Bader charge illustrates that the charge transfer increases from Cu core to Ni shell in Cu@Ni NPs, while it decreases from Ni core to Cu shell in Ni@Cu NPs. Furthermore, the charge transfer results that d-band states have larger shift toward the Fermi level for the Ni@Cu CSNPs with Cu surface shell, while the Cu@Ni CSNPs with Ni surface shell have similar d-band state curves and d-band centers with the monometallic Ni NPs. In addition, the Cu–Ni CSNPs possess higher magnetic moment when the Ni atoms aggregated at core region of CSNPs, while having lower magnetic moment when the Ni atoms segregate on surface region. The change of the Cu atom location in CSNPs has a weak effect on the total magnetic moment. Our findings provide useful insights for the design of bimetallic core–shell catalysts.

  5. Mass measurements of 56-57Cr and the question of shell reincarnation at N = 32

    International Nuclear Information System (INIS)

    Guenaut, C; Audi, G; Beck, D

    2005-01-01

    Binding energies determined with high accuracy provide smooth derivatives of the mass surface for analysis of shell and pairing effects. Measurements with the Penning trap mass spectrometer ISOLTRAP at CERN-ISOLDE were made for 56-57 Cr for which an accuracy of 4 x 10 -8 was achieved. Analysis of the mass surface for the supposed new N = 32 shell closure rather indicates a sub-shell closure, but of a different nature than known cases such as 94 Sr

  6. Mass measurements of 56-57Cr and the question of shell reincarnation at N = 32

    Science.gov (United States)

    Guénaut, C.; Audi, G.; Beck, D.; Blaum, K.; Bollen, G.; Delahaye, P.; Herfurth, F.; Kellerbauer, A.; Kluge, H.-J.; Lunney, D.; Schwarz, S.; Schweikhard, L.; Yazidjian, C.

    2005-10-01

    Binding energies determined with high accuracy provide smooth derivatives of the mass surface for analysis of shell and pairing effects. Measurements with the Penning trap mass spectrometer ISOLTRAP at CERN-ISOLDE were made for 56-57Cr for which an accuracy of 4 × 10-8 was achieved. Analysis of the mass surface for the supposed new N = 32 shell closure rather indicates a sub-shell closure, but of a different nature than known cases such as 94Sr.

  7. Mass measurements of $^{56-57}$Cr and the question of shell reincarnation at $N = 32$

    CERN Document Server

    Guenaut, Celine; Beck, D; Blaum, Klaus; Bollen, Georg; Delahaye, P; Herfurth, F; Kellerbauer, A G; Kluge, H J; Lunney, M D; Schwarz, S; Schweikhard, L; Yazidjian, C

    2005-01-01

    Binding energies determined with high accuracy provide smooth derivatives of the mass surface for analysis of shell and pairing effects. Measurements with the Penning trap mass spectrometer ISOLTRAP at CERN-ISOLDE were made for $^{56-57}$Cr for which an accuracy of $4 \\times 10^{-8}$ was achieved. Analysis of the mass surface for the supposed new $N = 32$ shell closure rather indicates a sub-shell closure, but of a different nature than known cases such as $^{94}$Sr.

  8. Preparation of Ca-alginate coated nZVI core shell beads for uranium (VI) removal from aqueous solution

    International Nuclear Information System (INIS)

    Shuhong Hu; Xiaoyan Lin; Yahui Zhang; Meiling Shi

    2017-01-01

    In this study, the core-shell nanoscale zero-valent iron (nZVI)@Alg-Ca beads were synthesized by coaxial electronic injection method for removal of U (VI) from aqueous solution, and characterized by SEM, EDX and XPS. The results showed that the pseudo-second-order models and the Langmuir isotherm model fitted well with the data obtained. The removal mechanism may include both physical adsorption of U (VI) on the surface or inside of core-shell nZVI@Alg-Ca beads and subsequent reduction of U (VI) to U (IV). Therefore, the core-shell nZVI@Alg-Ca beads would have an application prospect in effective removal of U (VI) contamination from aqueous solution. (author)

  9. Filling of double vacancy in the K atomic shell with emission of one single photon

    International Nuclear Information System (INIS)

    Jalbert, G.

    1978-12-01

    A method was developed to calculate the transition rate for two-electron one-photon K(sub αα) transition (2s 2p → 1s 2 ). The method was tested for Ni with two K-shell vacancies in the initial state. The (sub αα) rate is calculated within the framework of a single system formed by the atom and the radiation. The transition is originated in the interactiion between the parts of that system. In the dipole approximation, the transition rate is obtained from the second order term of the time dependente perturbation theory. Hartree-Fock-Slater wave functions were used in the calculations for Ni. The results are compared with the available theoretical and experimental information. (Author) [pt

  10. Simulation study of 3–5 keV x-ray conversion efficiency from Ar K-shell vs. Ag L-shell targets on the National Ignition Facility laser

    Energy Technology Data Exchange (ETDEWEB)

    Kemp, G. E., E-mail: kemp10@llnl.gov; Colvin, J. D.; Fournier, K. B.; May, M. J.; Barrios, M. A.; Patel, M. V.; Scott, H. A.; Marinak, M. M. [Lawrence Livermore National Laboratory, Livermore, California 94550-9698 (United States)

    2015-05-15

    Tailored, high-flux, multi-keV x-ray sources are desirable for studying x-ray interactions with matter for various civilian, space and military applications. For this study, we focus on designing an efficient laser-driven non-local thermodynamic equilibrium 3–5 keV x-ray source from photon-energy-matched Ar K-shell and Ag L-shell targets at sub-critical densities (∼n{sub c}/10) to ensure supersonic, volumetric laser heating with minimal losses to kinetic energy, thermal x rays and laser-plasma instabilities. Using HYDRA, a multi-dimensional, arbitrary Lagrangian-Eulerian, radiation-hydrodynamics code, we performed a parameter study by varying initial target density and laser parameters for each material using conditions readily achievable on the National Ignition Facility (NIF) laser. We employ a model, benchmarked against Kr data collected on the NIF, that uses flux-limited Lee-More thermal conductivity and multi-group implicit Monte-Carlo photonics with non-local thermodynamic equilibrium, detailed super-configuration accounting opacities from CRETIN, an atomic-kinetics code. While the highest power laser configurations produced the largest x-ray yields, we report that the peak simulated laser to 3–5 keV x-ray conversion efficiencies of 17.7% and 36.4% for Ar and Ag, respectively, occurred at lower powers between ∼100–150 TW. For identical initial target densities and laser illumination, the Ag L-shell is observed to have ≳10× higher emissivity per ion per deposited laser energy than the Ar K-shell. Although such low-density Ag targets have not yet been demonstrated, simulations of targets fabricated using atomic layer deposition of Ag on silica aerogels (∼20% by atomic fraction) suggest similar performance to atomically pure metal foams and that either fabrication technique may be worth pursuing for an efficient 3–5 keV x-ray source on NIF.

  11. Coupled-states calculations of argon L-shell impact ionisation

    International Nuclear Information System (INIS)

    Martir, M.H.; Ford, A.L.; Reading, J.F.

    1982-01-01

    A coupled-states method is used to calculate the corrections to the first Born approximation for L-shell impact ionisation in the ion-atom collisions p+Ar and α+Ar at energies between 100 and 850 keV amu -1 . Using a classical projectile path and a pseudostate description of the ionisation continuum, the pseudostate and partial-wave convergence is considered. It is found that the absolute cross sections for these collisions are sensitive to the particular independent-particle-model (IPM) target-atom potential which is used. A modification to the long-range part of the neutral-atom Hartree-Fock (HF) potential is proposed that lowers the energy of the unbound pseudostates and that thereby brings the L-shell removal energies closer to the experimental ionisation potentials. With this modified HF potential good agreement between the present L-shell ionisation cross sections and experimental L-vacancy production cross sections is found. (author)

  12. Successive change regularity of actinide properties with atomic number

    International Nuclear Information System (INIS)

    Yang Xuexian

    1990-08-01

    The development and achievements on chemistry of actinide elements are summarised. The relations of properties of actinides to their electronic configurations of valence electronic shells are discussed. Some anomalies of solid properties, the radius contraction, the stable state effect of f 7n -orbits (n = 0, 1, 2) and the tetrad effect of oxidation states, etc., with atomic number (Z) are described. 31 figures appended show directly the successive change regularity of actinide properties with Z

  13. Fabrication of Foam Shells for ICF Experiments

    Science.gov (United States)

    Czechowicz, D. G.; Acenas, O.; Flowers, J. S.; Nikroo, A.; Paguio, R. R.; Schroen, D. G.; Streit, J.; Takagi, M.

    2004-11-01

    The General Atomics/Schafer team has developed processes to fabricate foam shells targets suitable for ICF experiments. The two most common chemical systems used to produce foam shells have been resorcinol-formaldehyde (R/F) aerogel and divinylbenzene (DVB). Spherical targets have been made in the form of shells and beads having diameters ranging from approximately 0.5 mm to 4.0 mm, and having densities from approximately 100 mg/cc to 250 mg/cc. The work on R/F foam shells has been concentrated on 1) shell fabrication process improvement to obtain high yields ( ˜25%) and 2) depositing a reliable permeation barrier to provide shells for ongoing direct drive experiments at LLE. Development of divinylbenzene foam shells has been mainly directed towards Inertial Fusion Energy applications (at densities as low as 30 mg/cc) and recently for shells for experiments at LLE. Details of the relevant metrology and properties of these foams as well as the range of targets currently available will be discussed.

  14. Unconstrained off-shell N=3 supersymmetric Yang-Mills theory

    International Nuclear Information System (INIS)

    Galperin, A.; Ivanov, E.; Kalitzin, S.; Ogievetsky, V.; Sokatchev, E.

    1984-01-01

    The harmonic superspace is used to build up an unconstrained off-shell formulation of N=3 supersymmetric Yang-Mills theory. The theory is defined in an analytic N=3 superspace having M 4 x(SU(3)/U(1)xU(1) as an even part. The basic objects are the analytic potentials which serve as gauge connections entering harmonic derivatives. The action is an integral over analytic superspace. The Lagrange density is surprisingly simple and it is gauge invariant up to total harmonic derivative. The equations of motion are integrability conditions on the internal space SU(3)/U(1)xU(1). The jumping over the ''N=3 barrier'' became possible due to the infinite number of auxiliary fields

  15. Determination of K shell absorption jump factors and jump ratios of 3d transition metals by measuring K shell fluorescence parameters

    International Nuclear Information System (INIS)

    Kaçal, Mustafa Recep; Han, İbrahim; Akman, Ferdi

    2015-01-01

    Energy dispersive X-ray fluorescence technique (EDXRF) has been employed for measuring K-shell absorption jump factors and jump ratios for Ti, Cr, Fe, Co, Ni and Cu elements. The jump factors and jump ratios for these elements were determined by measuring K shell fluorescence parameters such as the Kα X-ray production cross-sections, K shell fluorescence yields, Kβ-to-Kα X-rays intensity ratios, total atomic absorption cross sections and mass attenuation coefficients. The measurements were performed using a Cd-109 radioactive point source and an Si(Li) detector in direct excitation and transmission experimental geometry. The measured values for jump factors and jump ratios were compared with theoretically calculated and the ones available in the literature. - Highlights: • This work regard the K shell absorption jump ratios and jump factors of Ti, Cr, Fe, Co, Ni and Cu. • This paper presents the first measurement of these parameters using the experimental K shell fluorescence parameters. • A good agreement was found between experimental and theoretical values. • The EDXRF technique was suitable, precise and reliable for the measurement of these atomic parameters

  16. Atomic structures and mechanical properties of single-crystal GaN nanotubes

    International Nuclear Information System (INIS)

    Xu, B.; Lu, A.J.; Pan, B.C.; Yu, Q.X.

    2005-01-01

    An approach is proposed to theoretically construct a realistic single-crystal GaN nanotube at atomic scale. The generated atomic structures of the single-crystal GaN nanotubes match the structural aspects from experiment very well. Our energetic calculations show that a single-crystal GaN nanotube with [100]-oriented lateral facets is more stable than that with [110]-oriented lateral facets, when they have around the same wall thickness. For a specified orientation of the lateral facets on the single-crystal GaN nanotubes, the energetic stabilities of the tubes obey a P rule, in which P is the ratio of the number of four-coordinated atoms to the number of three-coordinated atoms. Furthermore, the Young's modulus of the considered GaN nanotubes decrease with increasing the ratio of the number of bulk atoms to the number of surface atoms in each type of tube. Our calculations and analysis demonstrate that the surface effect of a single-crystal nanotube enhances its Young's modulus significantly

  17. Shell gap reduction in neutron-rich N=17 nuclei

    International Nuclear Information System (INIS)

    Obertelli, A.; Gillibert, A.; Alamanos, N.; Alvarez, M.; Auger, F.; Dayras, R.; Drouart, A.; France, G. de; Jurado, B.; Keeley, N.; Lapoux, V.; Mittig, W.; Mougeot, X.; Nalpas, L.; Pakou, A.; Patronis, N.; Pollacco, E.C.; Rejmund, F.; Rejmund, M.; Roussel-Chomaz, P.; Savajols, H.; Skaza, F.; Theisen, Ch.

    2006-01-01

    The spectroscopy of 27 Ne has been investigated through the one-neutron transfer reaction 26 Ne(d,p) 27 Ne in inverse kinematics at 9.7 MeV/nucleon. The results strongly support the existence of a low-lying negative parity state in 27 Ne, which is a signature of a reduced sd-fp shell gap in the N=16 neutron-rich region, at variance with stable nuclei

  18. Direct correlations of structural and optical properties of three-dimensional GaN/InGaN core/shell micro-light emitting diodes

    Science.gov (United States)

    Sadat Mohajerani, Matin; Müller, Marcus; Hartmann, Jana; Zhou, Hao; Wehmann, Hergo-H.; Veit, Peter; Bertram, Frank; Christen, Jürgen; Waag, Andreas

    2016-05-01

    Three-dimensional (3D) InGaN/GaN quantum-well (QW) core-shell light emitting diodes (LEDs) are a promising candidate for the future solid state lighting. In this contribution, we study direct correlations of structural and optical properties of the core-shell LEDs using highly spatially-resolved cathodoluminescence spectroscopy (CL) in combination with scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM). Temperature-dependent resonant photoluminescence (PL) spectroscopy has been performed to understand recombination mechanisms and to estimate the internal quantum efficiency (IQE).

  19. High resolution inner-shell spectroscopies of atoms and molecules in gas phase using the soft x-ray photochemistry beamline at SPring-8

    International Nuclear Information System (INIS)

    Ueda, Kiyoshi

    2003-01-01

    This article describes recent activities on inner-shell spectroscopies of atoms and molecules on beamline 27SU, nicknamed soft X-ray photochemistry beamline, at SPring-8, an 8-GeV synchrotron radiation facility in Japan. This beamline provides linearly polarized monochromatic soft X-rays at the resolution higher than 10,000. The end station is designed so that one can perform various kinds of excitation and de-excitation spectroscopies as well as coincidence spectroscopies. Following the description of the beamline and the end station, we present recent results for inner-shell spectroscopies on Ne, CO 2 , BF 3 , and CF 4 . Emphasis is given to illustrate the strategy of the research on this beamline and performance of the beamline and the end station. (author)

  20. Penning-trap mass measurements of the neutron-rich K and Ca isotopes: Resurgence of the N=28 shell strength

    Science.gov (United States)

    Lapierre, A.; Brodeur, M.; Brunner, T.; Ettenauer, S.; Finlay, P.; Gallant, A. T.; Simon, V. V.; Delheij, P.; Lunney, D.; Ringle, R.; Savajols, H.; Dilling, J.

    2012-02-01

    We present Penning-trap mass measurements of neutron-rich 44,47-50K and 49,50Ca isotopes carried out at the TITAN facility at TRIUMF-ISAC. The 44K mass measurement was performed with a charge-bred 4+ ion utilizing the TITAN electron beam ion trap and agrees with the literature. The mass excesses obtained for 47K and 49,50Ca are more precise and agree with the values published in the 2003 Atomic Mass Evaluation (AME’03). The 48,49,50K mass excesses are more precise than the AME’03 values by more than 1 order of magnitude. For 48,49K, we find deviations of 7σ and 10σ, respectively. The new 49K mass excess lowers significantly the two-neutron separation energy at the neutron number N=30 compared with the separation energy calculated from the AME’03 mass-excess values and thus increases the N=28 neutron-shell gap energy at Z=19 by approximately 1 MeV.

  1. Atomic four-level N systems

    International Nuclear Information System (INIS)

    Goren, C.; Rosenbluh, M.; Wilson-Gordon, A.D.; Friedmann, H.

    2004-01-01

    We investigate the atomic four-level N configuration both analytically and numerically, for various pump and probe intensities, with and without transfer of coherence (TOC) and Doppler broadening, and compare the results obtained to those of realistic atomic systems. We find that TOC affects the whole spectrum, in addition to producing an electromagnetically induced absorption (EIA) peak at line center. We show that the EIA peak splits as the pump intensity increases. These results are compared with those of realistic systems. When the pump is σ + polarized and the probe is π polarized, the results are similar to those of the N configuration. When the pump and probe polarizations are both linear with perpendicular polarizations, various N-like subsystems contribute to the spectrum. Consequently, the splitting of the EIA peak only occurs at very high pump intensities. We also discuss the influence of the probe on the pump absorption and refraction and find that both the pump and probe show EIA peaks when the pump intensity is low, and complementary behavior when the pump is intense. At both low and high pump intensity, the pump and probe dispersions are of opposite sign

  2. Collective effects in isolated atoms (many-body aspects of photoionization process)

    International Nuclear Information System (INIS)

    Amusia, M.Y.

    1983-01-01

    This chapter examines outer and intermediate many-electron shells and demonstrates that photoionization is of collective nature because in the atomic reaction to the external electromagnetic field at least all electrons of the ionized subshell take part. Performs the calculation of complex atom photoionization using random phase approximation with exchange (RPAE). Explains that in RPAE the ionization amplitude is presented as a sum of two terms, describing the direct knock-out and the induced one which is connected with a variation of the self-consistent field, caused by polarization of atomic shells under the action of the external field. Discusses collective effects in outer shells; deviation from RPAE prediction in outer shells; excitations ''two electrons-two holes'' and autoionizing states; collective effects in inner shells; and bremsstrahlung. Observes a large number of many-particle effects which manifest themselves practically in all atomic processes. Finds that by correcting and improving the one-electron approximation it becomes possible even in its frame to include much of what seems to be many-electron corrections

  3. Spin-spin interactions of electrons and also of nucleons create atomic molecular and nuclear structures

    International Nuclear Information System (INIS)

    Kaliambos, L.A.

    2008-01-01

    Fundamental interactions of spinning electrons at an interelectron separation less than 578.8 fm yield attractive electromagnetic forces with S = 0 creating vibrations under a motional emf. They explain the indistinguishability of electrons and give a vibration energy able for calculating the ground-state energies of many-electron atoms without using any perturbative approximation. Such forces create two-electron orbitals able to account for the exclusion principal and the mechanism of covalent bonds. In the outer subshells of atoms the penetrating orbitals interact also as pair-pair systems and deform drastically the probability densities of the quantum mechanical electron clouds. Such a dynamics of deformation removes the degeneracy and leads to the deviation from the shell scheme. However in the interior of atoms the large nuclear charge leads to a spherically symmetric potential with non-interacting pairs for creating shells of degenerate states giving an accurate explanation of the X-ray lines. On the other hand, considerable charge distributions in nucleons as multiples of 2e/3 and - e/3 determined by the magnetic moments, interact for creating the nuclear structure with p-n bonds. Such spin-spin interactions show that the dominant concept of the untisymmetric wave function for fermions is inapplicable not only in the simple p-n, p-p, and n-n systems but also in the LS coupling of atoms in which the electrons interact from different quantum states giving either S = 0 or S = l. (author)

  4. Assessment of density functional theory for bonds formed between rare gases and open-shell atoms: a computational study of small molecules containing He, Ar, Kr and Xe.

    Science.gov (United States)

    Bertolus, Marjorie; Major, Mohamed; Brenner, Valérie

    2012-01-14

    The validity of the description of the DFT approximations currently implemented in plane wave DFT codes (LDA, GGA, meta-GGA, hybrid, GGA + empirical dispersion correction) for interactions between rare gases and open-shell atoms which form materials is poorly known. We have performed a first assessment of the accuracy of these functionals for the description of the bonds formed by helium, argon, krypton and xenon with various open-shell atoms. This evaluation has been done on model molecular systems for which precise experimental data are available and reference post-Hartree-Fock calculations (CCSD(T) using large basis sets) are feasible. The results show that when the rare gas atom shares density with the neighbouring atoms, the GGA functionals yield good geometries and qualitatively correct binding energies, even if these are quite significantly overestimated. The use of hybrid functionals enables us to obtain good geometries and satisfactory binding energies. For compounds in which the rare gas atom forms weak dispersive-like bonding, the accuracy yielded by the various functionals is not as good. No functional gives satisfactory binding energies for all the compounds investigated. Several GGA and hybrid functionals yield correct geometries, even if some isomers are not obtained. One GGA functional (PBE) yields qualitatively correct results for the compounds of the three rare gases and several hybrid functionals give satisfactory energies for He compounds. The addition of an empirical dispersive correction improves the results on association compounds, but several isomers are not found.

  5. Assessment of density functional theory for bonds formed between rare gases and open-shell atoms: a computational study of small molecules containing He, Ar, Kr and Xe

    International Nuclear Information System (INIS)

    Bertolus, Marjorie; Major, Mohamed; Brenner, Valerie

    2012-01-01

    The validity of the description of the DFT approximations currently implemented in plane wave DFT codes (LDA, GGA, meta-GGA, hybrid, GGA + empirical dispersion correction) for interactions between rare gases and open-shell atoms which form materials is poorly known. We have performed a first assessment of the accuracy of these functionals for the description of the bonds formed by helium, argon, krypton and xenon with various open-shell atoms. This evaluation has been done on model molecular systems for which precise experimental data are available and reference post-Hartree-Fock calculations (CCSD(T) using large basis sets) are feasible. The results show that when the rare gas atom shares density with the neighbouring atoms, the GGA functionals yield good geometries and qualitatively correct binding energies, even if these are quite significantly overestimated. The use of hybrid functionals enables us to obtain good geometries and satisfactory binding energies. For compounds in which the rare gas atom forms weak dispersive-like bonding, the accuracy yielded by the various functionals is not as good. No functional gives satisfactory binding energies for all the compounds investigated. Several GGA and hybrid functionals yield correct geometries, even if some isomers are not obtained. One GGA functional (PBE) yields qualitatively correct results for the compounds of the three rare gases and several hybrid functionals give satisfactory energies for He compounds. The addition of an empirical dispersive correction improves the results on association compounds, but several isomers are not found. (authors)

  6. Beta-decay half-lives at the N=28 shell closure

    Energy Technology Data Exchange (ETDEWEB)

    Grevy, S.; Angelique, J.C.; Baumann, P.; Borcea, C.; Buta, A.; Canchel, G.; Catford, W.N.; Courtin, S.; Daugas, J.M.; Oliveira, F. de; Dessagne, P.; Dlouhy, Z.; Knipper, A.; Kratz, K.L.; Lecolley, F.R.; Lecouey, J.L.; Lehrsenneau, G.; Lewitowicz, M.; Lienard, E.; Lukyanov, S.; Marechal, F.; Miehe, C.; Mrazek, J.; Negoita, F.; Orr, N.A.; Pantelica, D.; Penionzhkevich, Y.; Peter, J.; Pfeiffer, B.; Pietri, S.; Poirier, E.; Sorlin, O.; Stanoiu, M.; Stefan, I.; Stodel, C.; Timis, C

    2004-08-05

    Measurements of the beta-decay half-lives of neutron-rich nuclei (Mg-Ar) in the vicinity of the N=28 shell closure are reported. Some 22 half-lives have been determined, 12 of which for the first time. Particular emphasis is placed on the results for the Si isotopes, the half-lives of which have been extended from N=25 to 28. Comparison with QRPA calculations suggests that {sup 42}Si is strongly deformed. This is discussed in the light of a possible weakening of the spin-orbit potential.

  7. Atomic physics with highly charged ions

    International Nuclear Information System (INIS)

    Richard, P.

    1991-08-01

    This report discusses: One electron outer shell processes in fast ion-atom collisions; role of electron-electron interaction in two-electron processes; multi-electron processes at low energy; multi-electron processes at high energy; inner shell processes; molecular fragmentation studies; theory; and, JRM laboratory operations

  8. Cross sections for double K-shell ionization in slow heavy ion-atom collisions, ch. 4

    International Nuclear Information System (INIS)

    Hoogkamer, T.P.; Woerlee, P.H.; Saris, F.W.

    1977-01-01

    Cross sections for Ksub(αα) X-ray production have been measured in collisions of 200 keV N + → NH 3 , N 2 , H 2 O; O + → NH 3 , H 2 O and 200, 400, 600 keV Ne 2+ → Ne. Fluorescence yields for Ksub(αα) two-electron one-photon transitions have been estimated for N and O, whereas for Ne, theoretical values for the fluorescence yield are available. We have used these to obtain double K-shell ionizzation cross sections which are compared to calculated cross section based on the theory for rotational coupling in the transient quasimolecular state

  9. Mass measurements of {sup 56-57}Cr and the question of shell reincarnation at N = 32

    Energy Technology Data Exchange (ETDEWEB)

    Guenaut, C [CSNSM-IN2P3/CNRS, Universite de Paris Sud, 91405 Orsay (France); Audi, G [CSNSM-IN2P3/CNRS, Universite de Paris Sud, 91405 Orsay (France); Beck, D [GSI, Planckstrasse 1, 64291 Darmstadt (Germany)] [and others

    2005-10-01

    Binding energies determined with high accuracy provide smooth derivatives of the mass surface for analysis of shell and pairing effects. Measurements with the Penning trap mass spectrometer ISOLTRAP at CERN-ISOLDE were made for {sup 56-57}Cr for which an accuracy of 4 x 10{sup -8} was achieved. Analysis of the mass surface for the supposed new N = 32 shell closure rather indicates a sub-shell closure, but of a different nature than known cases such as {sup 94}Sr.

  10. Fragmentation of stretched spin strength in N=Z sd-shell nuclei

    International Nuclear Information System (INIS)

    Carr, J.A.; Bloom, S.D.; Petrovich, F.; Philpott, R.J.

    1992-01-01

    Calculations have been performed to explore the effect of configuration mixing in a large basis on the fragmentation of ''stretched'' M6 strength in the sd-shell nuclei 20 Ne, 24 Mg, 28 Si, 32 S, and 36 Ar. This work elaborates on results for 28 Si given previously, extends those calculations to neighboring N=Z nuclei with the same basis restriction (one particle in the 1f 7/2 orbit and up to four particles in the 1d 3/2 orbit) used in that earlier paper, and examines all self-conjugate sd-shell nuclei in a basis with one particle in the 1f 7/2 orbit and unrestricted occupancy of the sd-shell orbits. It is found that configuration mixing in a large basis reproduces interesting features of the spectrum for 28 Si and 32 S and gives an improved description of other properties of the observed 6 - states, but fails to describe the observed spectrum in 24 Mg. Emphasis is placed on the location of additional observable fragments of the M6 response

  11. Foam shell project: Progress report

    International Nuclear Information System (INIS)

    Overturf, G.; Reibold, B.; Cook, B.; Schroen-Carey, D.

    1994-01-01

    The authors report on their work to produce a foam shell target for two possible applications: (1) as liquid-layered cryogenic target on Omega Upgrade, and (2) as a back-up design for the NIF. This target consists of a roughly 1 mm diameter and 100 μm thick spherical low-density foam shell surrounding a central void. The foam will be slightly overfilled with liquid D 2 or DT, the overfilled excess being symmetrically distributed on the inside of the shell and supported by thermal gradient techniques. The outside of the foam is overcoated with full density polymer which must be topologically smooth. The technology for manufacturing this style of foam shell involves microencapsulation techniques and has been developed by the Japanese at ILE. Their goal is to determine whether this technology can be successfully adapted to meet US ICF objectives. To this end a program of foam shell development has been initiated at LLNL in collaboration with both the General Atomics DOE Target Fabrication Contract Corporation and the Target Fabrication Group at LLE

  12. Accelerated ions as a tool in atomic physics

    International Nuclear Information System (INIS)

    Hansteen, J.M.

    1977-01-01

    Some of the aspects of atomic physics which are being brought into focus by the construction and completion of a new generation of heavy-ion accelerators are dealt with. Various types of processes occurring in the overlapping electron clouds are visualised in an elementary way, using among others, some recent observations on the formation of quasi-molecules and quasi-atoms. Phenomena connected with the inner electron shells in superheavy atoms are touched upon, in particular those processes possibly leading to the production of positrons. In such cases the crucial importance of an atomic Coulomb excitation mechanism is stressed. In conclusion the view is emphasized that inner shell ionization phenomena in heavy ion collisions form a bridge between processes originating respectively from nuclear and atomic physics. (Auth.)

  13. Ni3Si(Al)/a-SiOx core shell nanoparticles: characterization, shell formation, and stability

    Science.gov (United States)

    Pigozzi, G.; Mukherji, D.; Gilles, R.; Barbier, B.; Kostorz, G.

    2006-08-01

    We have used an electrochemical selective phase dissolution method to extract nanoprecipitates of the Ni3Si-type intermetallic phase from two-phase Ni-Si and Ni-Si-Al alloys by dissolving the matrix phase. The extracted nanoparticles are characterized by transmission electron microscopy, energy-dispersive x-ray spectrometry, x-ray powder diffraction, and electron powder diffraction. It is found that the Ni3Si-type nanoparticles have a core-shell structure. The core maintains the size, the shape, and the crystal structure of the precipitates that existed in the bulk alloys, while the shell is an amorphous phase, containing only Si and O (SiOx). The shell forms around the precipitates during the extraction process. After annealing the nanoparticles in nitrogen at 700 °C, the tridymite phase recrystallizes within the shell, which remains partially amorphous. In contrast, on annealing in air at 1000 °C, no changes in the composition or the structure of the nanoparticles occur. It is suggested that the shell forms after dealloying of the matrix phase, where Si atoms, the main constituents of the shell, migrate to the surface of the precipitates.

  14. Relativistic heavy-atom effects on heavy-atom nuclear shieldings

    Science.gov (United States)

    Lantto, Perttu; Romero, Rodolfo H.; Gómez, Sergio S.; Aucar, Gustavo A.; Vaara, Juha

    2006-11-01

    The principal relativistic heavy-atom effects on the nuclear magnetic resonance (NMR) shielding tensor of the heavy atom itself (HAHA effects) are calculated using ab initio methods at the level of the Breit-Pauli Hamiltonian. This is the first systematic study of the main HAHA effects on nuclear shielding and chemical shift by perturbational relativistic approach. The dependence of the HAHA effects on the chemical environment of the heavy atom is investigated for the closed-shell X2+, X4+, XH2, and XH3- (X =Si-Pb) as well as X3+, XH3, and XF3 (X =P-Bi) systems. Fully relativistic Dirac-Hartree-Fock calculations are carried out for comparison. It is necessary in the Breit-Pauli approach to include the second-order magnetic-field-dependent spin-orbit (SO) shielding contribution as it is the larger SO term in XH3-, XH3, and XF3, and is equally large in XH2 as the conventional, third-order field-independent spin-orbit contribution. Considering the chemical shift, the third-order SO mechanism contributes two-thirds of the difference of ˜1500ppm between BiH3 and BiF3. The second-order SO mechanism and the numerically largest relativistic effect, which arises from the cross-term contribution of the Fermi contact hyperfine interaction and the relativistically modified spin-Zeeman interaction (FC/SZ-KE), are isotropic and practically independent of electron correlation effects as well as the chemical environment of the heavy atom. The third-order SO terms depend on these factors and contribute both to heavy-atom shielding anisotropy and NMR chemical shifts. While a qualitative picture of heavy-atom chemical shifts is already obtained at the nonrelativistic level of theory, reliable shifts may be expected after including the third-order SO contributions only, especially when calculations are carried out at correlated level. The FC/SZ-KE contribution to shielding is almost completely produced in the s orbitals of the heavy atom, with values diminishing with the principal

  15. On the size and structure of helium snowballs formed around charged atoms and clusters of noble gases.

    Science.gov (United States)

    Bartl, Peter; Leidlmair, Christian; Denifl, Stephan; Scheier, Paul; Echt, Olof

    2014-09-18

    Helium nanodroplets doped with argon, krypton, or xenon are ionized by electrons and analyzed in a mass spectrometer. HenNgx(+) ions containing up to seven noble gas (Ng) atoms and dozens of helium atoms are identified; the high resolution of the mass spectrometer combined with advanced data analysis make it possible to unscramble contributions from isotopologues that have the same nominal mass but different numbers of helium or Ng atoms, such as the magic He20(84)Kr2(+) and the isobaric, nonmagic He41(84)Kr(+). Anomalies in these ion abundances reveal particularly stable ions; several intriguing patterns emerge. Perhaps most astounding are the results for HenAr(+), which show evidence for three distinct, solid-like solvation shells containing 12, 20, and 12 helium atoms. This observation runs counter to the common notion that only the first solvation shell is solid-like but agrees with calculations by Galli et al. for HenNa(+) [J. Phys. Chem. A 2011, 115, 7300] that reveal three shells of icosahedral symmetry. HenArx(+) (2 ≤ x ≤ 7) ions appear to be especially stable if they contain a total of n + x = 19 atoms. A sequence of anomalies in the abundance distribution of HenKrx(+) suggests that rings of six helium atoms are inserted into the solvation shell each time a krypton atom is added to the ionic core, from Kr(+) to Kr3(+). Previously reported strong anomalies at He12Kr2(+) and He12Kr3(+) [Kim , J. H.; et al. J. Chem. Phys. 2006, 124, 214301] are attributed to a contamination. Only minor local anomalies appear in the distributions of HenXex(+) (x ≤ 3). The distributions of HenKr(+) and HenXe(+) show strikingly similar, broad features that are absent from the distribution of HenAr(+); differences are tentatively ascribed to the very different fragmentation dynamics of these ions.

  16. L-shell radiative transition rates by selective synchrotron ionization

    International Nuclear Information System (INIS)

    Bonetto, R D; Carreras, A C; Trincavelli, J; Castellano, G

    2004-01-01

    Relative L-shell radiative transition rates were obtained for a number of decays in Gd, Dy, Er, Yb, Hf, Ta and Re by means of a method for refining atomic and experimental parameters involved in the spectral analysis of x-ray irradiated samples. For this purpose, pure samples were bombarded with monochromatic synchrotron radiation tuning the incident x-ray energy in order to allow selective ionization of the different atomic shells. The results presented are compared to experimental and theoretical values published by other authors. A good general agreement was found and some particular discrepancies are discussed

  17. Multiconfiguration Hartree--Fock method for atomic energy levels and transition probabilities

    International Nuclear Information System (INIS)

    Fischer, C.F.

    1978-01-01

    The effect of correlation in the motion of electrons in a many-electron system is considered in the theoretical determination of atomic properties. The correlation effects are computed using the configuration interaction. Restriction is made to the discussion of outer processes of neutral atoms or ions of low degree of ionization in which the relativistic effects are small. The first-order theory, the 3p,3d state of Al II, correlation in the 3d/sup n/ shell, and f-values in the presence of cross-overs are discussed. 29 references

  18. Auger Spectra and Different Ionic Charges Following 3s, 3p and 3d Sub-Shells Photoionization of Kr Atoms

    Directory of Open Access Journals (Sweden)

    Yehia A. Lotfy

    2006-01-01

    Full Text Available The decay of inner-shell vacancy in an atom through radiative and non-radiative transitions leads to final charged ions. The de-excitation decay of 3s, 3p and 3d vacancies in Kr atoms are calculated using Monte-Carlo simulation method. The vacancy cascade pathway resulted from the de-excitation decay of deep core hole in 3s subshell in Kr atoms is discussed. The generation of spectator vacancies during the vacancy cascade development gives rise to Auger satellite spectra. The last transitions of the de-excitation decay of 3s, 3p and 3d holes lead to specific charged ions. Dirac-Fock-Slater wave functions are adapted to calculate radiative and non-radiative transition probabilities. The intensity of Kr^{4+} ions are high for 3s hole state, whereas Kr^{3+} and Kr^{2+} ions have highest intensities for 3p and 3d hole states, respectively. The present results of ion charge state distributions agree well with the experimental data.

  19. Inner shell ionization by incident nuclei

    International Nuclear Information System (INIS)

    Hansteen, J.M.

    1974-10-01

    The atomic Coulomb excitation process induced by impinging heavy charged particles such as protons, deuterons, α-particles and complex heavy ions is reviewed. Recent experimental and theoretical efforts have led toimproved understanding of the atomic Coulomb excitation as well as to discovery of new types of ionization mechanisms. The following models are mentioned: the Plane Wave Born Approximation (PWBA); theeeeeeeeeeeee modified PWBA model; the Binary Encounter Approximation (BEA); the Semi-Classical Approximation (SCA); the Perturbed-Stationary-State model (PSS). The structure of the SCA model is more thoroughly treated. Experimental results on single Coulomb ionizations of the K-, L-, and M-shells, and of the connected sub-shells by protons are compared with predictions. Most calculations are based on straight line projectile paths and non-relativistic hydrogen-like target electron wave functions. The BEA model and the SCA model seem to work reasonably well for multiple Coulomb ionizations by stripped light ions. Background effects in ion-atom collisions are commented upon. Future aspects of atomic Coulomb excitation by incident nuclei and ions are discussed. The interplay between Coulomb induced processes and united atom phenomena is especially mentioned. The simple ionization models have yielded valuable insights but it is suggested that this branch of collision physics has reached a turning point where new and more advanced and unifying models are needed. (JIW)

  20. K-shell ionization and double-ionization of Au atoms with 1.33 MeV photons

    International Nuclear Information System (INIS)

    Belkacem, A.; Dauvergne, D.; Feinberg, B.; Ionescu, D.; Maddi, J.; Sorensen, A.H.

    2000-01-01

    At relativistic energies, the cross section for the atomic photoelectric effect drops off as does the cross section for liberating any bound electron through Compton scattering. However, when the photon energy exceeds twice the rest mass of the electron, ionization may proceed via electron-positron pair creation. We used 1.33 MeV photons impinging on Au thin foils to study double K-shell ionization and vacuum-assisted photoionization. The preliminary results yield a ratio of vacuum-assisted photoionization and pair creation of 2x10 -3 , a value that is substantially higher than the ratio of photo double ionization to single photoionization that is found to be 0.5-1x10 -4 . Because of the difficulties and large error bars associated with the small cross sections additional measurements are needed to minimize systematic errors

  1. The measurement of electrostatic potentials in core/shell GaN nanowires using off-axis electron holography

    DEFF Research Database (Denmark)

    Yazdi, Sadegh; Kasama, Takeshi; Ciechonski, R

    2013-01-01

    Core-shell GaN nanowires are expected to be building blocks of future light emitting devices. Here we apply off-axis electron holography to map the electrostatic potential distributions in such nanowires. To access the cross-section of selected individual nanowires, focused ion beam (FIB) milling...... is used. Furthermore, to assess the influence of FIB damage, the dopant potential measured from an intact NW is compared with a FIB prepared one. It is shown that in addition to the built-in potential between the p-type shell and unintentionally n-type under-layer there is a potential barrier between...... the core and under-layer which are both unintentionally n-type doped....

  2. Formation of InN atomic-size wires by simple N adsorption on the In/Si(111)–(4 × 1) surface

    International Nuclear Information System (INIS)

    Guerrero-Sánchez, J.; Takeuchi, Noboru

    2016-01-01

    Highlights: • N atoms on the surface form bonds with two In atoms and one Si atom. • Surface formation energy calculations show two stable structures with formation of InN atomic-size wires. • Projected density of states shows a tendency to form In−N and Si−N bonds on the surface. • Charge density corroborates the covalent character of the In−N bonds. - Abstract: We have carried out first principles total energy calculations to study the formation of InN atomic-size wires on the In/Si(111)–(4 × 1) surface. In its most favorable adsorption site, a single N atom forms InN arrangements. The deposit of 0.25 monolayers (MLs) of N atoms, result in the breaking of one of the original In chains and the formation of an InN atomic size wire. Increasing the coverage up to 0.5 ML of N atoms results in the formation of two of those wires. Calculated surface formation energies show that for N-poor conditions the most stable configuration is the original In/Si(111)–(4 × 1) surface with no N atoms. Increasing the N content, and in a reduced range of chemical potential, the formation of an InN wire is energetically favorable. Instead, from intermediate to N-rich conditions, two InN atomic wires are more stable. Projected density of states calculations have shown a trend to form covalent bonds between the In−p and N−p orbitals in these stable models.

  3. Atom transfer radical polymerization of n-butyl acrylate catalyzed by atom transfer radical polymerization of n-butyl acrylate catalyzed by

    NARCIS (Netherlands)

    Zhang, H.; Linde, van der R.

    2002-01-01

    The homogeneous atom transfer radical polymerization (ATRP) of n-butyl acrylate with CuBr/N-(n-hexyl)-2-pyridylmethanimine as a catalyst and ethyl 2-bromoisobutyrate as an initiator was investigated. The kinetic plots of ln([M]0/[M]) versus the reaction time for the ATRP systems in different

  4. a-Axis GaN/AlN/AlGaN Core-Shell Heterojunction Microwires as Normally Off High Electron Mobility Transistors.

    Science.gov (United States)

    Song, Weidong; Wang, Rupeng; Wang, Xingfu; Guo, Dexiao; Chen, Hang; Zhu, Yuntao; Liu, Liu; Zhou, Yu; Sun, Qian; Wang, Li; Li, Shuti

    2017-11-29

    Micro/nanowire-based devices have been envisioned as a promising new route toward improved electronic and optoelectronic applications, which attracts considerable research interests. However, suffering from applicable strategies to synthesize uniform core-shell structures to meet the requirement for the investigations of electrical transport behaviors along the length direction or high electron mobility transistor (HEMT) devices, heterojunction wire-based electronics have been explored limitedly. In the present work, GaN/AlN/AlGaN core-shell heterojunction microwires on patterned Si substrates were synthesized without any catalyst via metalorganic chemical vapor deposition. The as-synthesized microwires had low dislocation, sharp, and uniform heterojunction interfaces. Electrical transport performances were evaluated by fabricating HEMTs on the heterojunction microwire channels. Results demonstrated that a normally off operation was achieved with a threshold voltage of 1.4 V, a high on/off current ratio of 10 8 , a transconductance of 165 mS/mm, and a low subthreshold swing of 81 mV/dec. The normally off operation may attribute to the weak polarization along semipolar facets of the heterojunction, which leads to weak constrain of 2DEG.

  5. Microencapsulated n-octadecane with different methylmethacrylate-based copolymer shells as phase change materials for thermal energy storage

    International Nuclear Information System (INIS)

    Qiu, Xiaolin; Li, Wei; Song, Guolin; Chu, Xiaodong; Tang, Guoyi

    2012-01-01

    Microcapsules containing n-octadecane with different methylmethacrylate (MMA (methyl methacrylate))-based copolymer shells were fabricated by a suspension-like polymerization. Butyl acrylate (BA), butyl methacrylate (BMA), lauryl methacrylate (LMA) and stearyl methacrylate (SMA) were employed as monomers to copolymerize with MMA. Pentaerythritol tetraacrylate (PETRA) was employed as a crosslinking agent. The (microencapsulted phase change materials) MicroPCMs were characterized using Fourier transformed infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). Thermal properties and thermal resistances of MicroPCMs were investigated by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA), respectively. Phase change enthalpies and PCM contents of MicroPCMs increased with the length decreasing of the side chain of the monomers. The n-octadecane content of as much as 77.3% can be obtained in the crosslinked MicroPCMs with P(MMA-co-BMA) as shell, and accompanied by the highest melting enthalpy (173.7 J/g) and crystallization enthalpy (174.4 J/g). Heat capacities of crosslinked MicroPCMs are higher than those of their uncrosslinked counterparts. The crosslinked MicroPCMs exhibit significantly greater thermal stabilities compared with their uncrosslinked counterparts and the n-ontadecane bulk. The crosslinked MicroPCMs with P(MMA-co-SMA) displays the highest thermal resistance temperature up to 255 °C. Therefore, MicroPCMs with MMA-based copolymer as shells, especially crosslinked copolymer shells, show excellent potentials for thermal energy storage. -- Highlights: ► n-Octadecane was encapsulated with methylmethacrylate(MMA)-based copolymer shells. ► n-Octadecane content of Microcapsules increased with length decreasing of side chain of monomers. ► Microcapsule with P(MMA-co-butyl methacrylate) has the highest latent heat. ► Microcapsule with P(MMA-co-stearyl methacrylate) has the greatest thermal stability.

  6. Ni(3)Si(Al)/a-SiO(x) core-shell nanoparticles: characterization, shell formation, and stability.

    Science.gov (United States)

    Pigozzi, G; Mukherji, D; Gilles, R; Barbier, B; Kostorz, G

    2006-08-28

    We have used an electrochemical selective phase dissolution method to extract nanoprecipitates of the Ni(3)Si-type intermetallic phase from two-phase Ni-Si and Ni-Si-Al alloys by dissolving the matrix phase. The extracted nanoparticles are characterized by transmission electron microscopy, energy-dispersive x-ray spectrometry, x-ray powder diffraction, and electron powder diffraction. It is found that the Ni(3)Si-type nanoparticles have a core-shell structure. The core maintains the size, the shape, and the crystal structure of the precipitates that existed in the bulk alloys, while the shell is an amorphous phase, containing only Si and O (SiO(x)). The shell forms around the precipitates during the extraction process. After annealing the nanoparticles in nitrogen at 700 °C, the tridymite phase recrystallizes within the shell, which remains partially amorphous. In contrast, on annealing in air at 1000 °C, no changes in the composition or the structure of the nanoparticles occur. It is suggested that the shell forms after dealloying of the matrix phase, where Si atoms, the main constituents of the shell, migrate to the surface of the precipitates.

  7. Assessment of the accuracy of coupled cluster perturbation theory for open-shell systems. II. Quadruples expansions.

    Science.gov (United States)

    Eriksen, Janus J; Matthews, Devin A; Jørgensen, Poul; Gauss, Jürgen

    2016-05-21

    We extend our assessment of the potential of perturbative coupled cluster (CC) expansions for a test set of open-shell atoms and organic radicals to the description of quadruple excitations. Namely, the second- through sixth-order models of the recently proposed CCSDT(Q-n) quadruples series [J. J. Eriksen et al., J. Chem. Phys. 140, 064108 (2014)] are compared to the prominent CCSDT(Q) and ΛCCSDT(Q) models. From a comparison of the models in terms of their recovery of total CC singles, doubles, triples, and quadruples (CCSDTQ) energies, we find that the performance of the CCSDT(Q-n) models is independent of the reference used (unrestricted or restricted (open-shell) Hartree-Fock), in contrast to the CCSDT(Q) and ΛCCSDT(Q) models, for which the accuracy is strongly dependent on the spin of the molecular ground state. By further comparing the ability of the models to recover relative CCSDTQ total atomization energies, the discrepancy between them is found to be even more pronounced, stressing how a balanced description of both closed- and open-shell species-as found in the CCSDT(Q-n) models-is indeed of paramount importance if any perturbative CC model is to be of chemical relevance for high-accuracy applications. In particular, the third-order CCSDT(Q-3) model is found to offer an encouraging alternative to the existing choices of quadruples models used in modern computational thermochemistry, since the model is still only of moderate cost, albeit markedly more costly than, e.g., the CCSDT(Q) and ΛCCSDT(Q) models.

  8. Innershell ionisation at small impactparameters in proton-atom collisions

    International Nuclear Information System (INIS)

    Duinker, W.

    1981-01-01

    This thesis concentrates on innershell ionisation in proton-atom collisions. An experiment on K-shell ionisation of argon is described, performed in a gasfilled collision chamber under single collision conditions. Further experiments with carbon and aluminium were performed, the K-shell vacancy production in the collision of protons with these atoms being detected through the measurement of Auger-electrons. A spectrometer with a large solid angle was specially constructed for this and its performance is described. K-shell ionisation accompanying nuclear (p,γ) reactions has also been measured using 26 Mg and 27 Al. (Auth./C.F.)

  9. The influence of (n-n')-mixing processes in He*(n)+He(1s2) collisions on He*(n) atoms' populations in weakly ionized helium plasmas

    International Nuclear Information System (INIS)

    Mihajlov, A.A.; Ignjatovic, Lj.M.; Sreckovic, V.A.; Djuric, Z.

    2008-01-01

    The results of semi-classical calculations of rate coefficients of (n-n ' )-mixing processes due to collisions of Rydberg atoms He*(n) with He(1s 2 ) atoms are presented. It is assumed that these processes are caused by the resonant energy exchange within the electron component of He*(n)+He collision system. The method is realized through the numerical simulation of the (n-n ' )-mixing processes, and is applied for calculations of the corresponding rate coefficients. The calculations are performed for the principal quantum numbers n,n ' in ranges 4≤n ' ≤10, and the atom and electron temperatures, T a ,T e , in domains 5000K≤T a ≤T e ≤20000K. It is shown that the (n-n ' )-mixing processes can significantly influence the populations of Rydberg atoms in non-equilibrium weakly ionized helium plasmas with ionization degree ∼10 -4 . Therefore, these processes have to be included in the appropriate models of such plasmas

  10. Assessment of the accuracy of coupled cluster perturbation theory for open-shell systems. I. Triples expansions.

    Science.gov (United States)

    Eriksen, Janus J; Matthews, Devin A; Jørgensen, Poul; Gauss, Jürgen

    2016-05-21

    The accuracy at which total energies of open-shell atoms and organic radicals may be calculated is assessed for selected coupled cluster perturbative triples expansions, all of which augment the coupled cluster singles and doubles (CCSD) energy by a non-iterative correction for the effect of triple excitations. Namely, the second- through sixth-order models of the recently proposed CCSD(T-n) triples series [J. J. Eriksen et al., J. Chem. Phys. 140, 064108 (2014)] are compared to the acclaimed CCSD(T) model for both unrestricted as well as restricted open-shell Hartree-Fock (UHF/ROHF) reference determinants. By comparing UHF- and ROHF-based statistical results for a test set of 18 modest-sized open-shell species with comparable RHF-based results, no behavioral differences are observed for the higher-order models of the CCSD(T-n) series in their correlated descriptions of closed- and open-shell species. In particular, we find that the convergence rate throughout the series towards the coupled cluster singles, doubles, and triples (CCSDT) solution is identical for the two cases. For the CCSD(T) model, on the other hand, not only its numerical consistency, but also its established, yet fortuitous cancellation of errors breaks down in the transition from closed- to open-shell systems. The higher-order CCSD(T-n) models (orders n > 3) thus offer a consistent and significant improvement in accuracy relative to CCSDT over the CCSD(T) model, equally for RHF, UHF, and ROHF reference determinants, albeit at an increased computational cost.

  11. Assessment of the accuracy of coupled cluster perturbation theory for open-shell systems. I. Triples expansions

    Energy Technology Data Exchange (ETDEWEB)

    Eriksen, Janus J., E-mail: janusje@chem.au.dk; Jørgensen, Poul [qLEAP Center for Theoretical Chemistry, Department of Chemistry, Aarhus University, DK-8000 Aarhus C (Denmark); Matthews, Devin A. [The Institute for Computational Engineering and Sciences, The University of Texas at Austin, Austin, Texas 78712 (United States); Gauss, Jürgen [Institut für Physikalische Chemie, Johannes Gutenberg-Universität Mainz, D-55128 Mainz (Germany)

    2016-05-21

    The accuracy at which total energies of open-shell atoms and organic radicals may be calculated is assessed for selected coupled cluster perturbative triples expansions, all of which augment the coupled cluster singles and doubles (CCSD) energy by a non-iterative correction for the effect of triple excitations. Namely, the second- through sixth-order models of the recently proposed CCSD(T–n) triples series [J. J. Eriksen et al., J. Chem. Phys. 140, 064108 (2014)] are compared to the acclaimed CCSD(T) model for both unrestricted as well as restricted open-shell Hartree-Fock (UHF/ROHF) reference determinants. By comparing UHF- and ROHF-based statistical results for a test set of 18 modest-sized open-shell species with comparable RHF-based results, no behavioral differences are observed for the higher-order models of the CCSD(T–n) series in their correlated descriptions of closed- and open-shell species. In particular, we find that the convergence rate throughout the series towards the coupled cluster singles, doubles, and triples (CCSDT) solution is identical for the two cases. For the CCSD(T) model, on the other hand, not only its numerical consistency, but also its established, yet fortuitous cancellation of errors breaks down in the transition from closed- to open-shell systems. The higher-order CCSD(T–n) models (orders n > 3) thus offer a consistent and significant improvement in accuracy relative to CCSDT over the CCSD(T) model, equally for RHF, UHF, and ROHF reference determinants, albeit at an increased computational cost.

  12. Atomic physics made clear

    International Nuclear Information System (INIS)

    Meinhold, H.

    1980-01-01

    This book is a popular introduction into the foundations of atomic physics und quantum mechanics. Starting from some phenomenological concepts Bohr's model and the construction of the periodic system regarding the shell structure of atoms are introduced. In this framework the selection rules and magnetic moments of atomic electrons are considered. Finally the wave-particle dualism is considered. In the appendix some mathematical methods are described which are useful for a deeper penetration into the considered ideas. (HSI)

  13. Organic superalkalis with closed-shell structure and aromaticity

    Science.gov (United States)

    Srivastava, Ambrish Kumar

    2018-06-01

    Benzene (C6H6) and polycyclic hydrocarbons such as naphthalene (C10H8), anthracene (C14H10) and coronene (C24H12) are well known aromatic organic compounds. We study the substitution of Li replacing all H-atoms in these hydrocarbons using density functional method. The vertical ionisation energy of such lithiated species, i.e. C6Li6, C10Li8, C14Li10 and C24Li12 ranges 4.24-4.50 eV, which is lower than the ionisation energy (IE) of Li atom. Thus, these species may behave as superalkalis due to their lower IE than alkali metal. However, these lithiated species possess planar and closed-shell structure, unlike typical superalkalis. Furthermore, all Li-substituted species are aromatic although their degree of aromaticity is reduced as compared to corresponding hydrocarbon analogues. We have further explored the structure of C6Li6 as star-like, unlike its inorganic analogue B3N3Li6, which appears as fan-like structure. We have also demonstrated that the interaction of C6Li6 with a superhalogen (such as BF4) is similar to that of a typical superalkali (such as OLi3). This may further suggest that the proposed lithiated species may form a new class of closed-shell organic superalkalis with aromaticity.

  14. Enzymatic production of N-acetyl-d-glucosamine from crayfish shell wastes pretreated via high pressure homogenization.

    Science.gov (United States)

    Wei, Guoguang; Zhang, Alei; Chen, Kequan; Ouyang, Pingkai

    2017-09-01

    This study presents an efficient pretreatment of crayfish shell using high pressure homogenization that enables N-acetyl-d-glucosamine (GlcNAc) production by chitinase. Firstly, the chitinase from Serratia proteamaculans NJ303 was screened for its ability to degrade crayfish shell and produce GlcNAc as the sole product. Secondly, high pressure homogenization, which caused the crayfish shell to adopt a fluffy netted structure that was characterized by Scanning electron microscope (SEM), Fourier transform infrared spectrometer (FT-IR), X-ray diffraction (XRD), was evaluated as the best pretreatment method. In addition, the optimal conditions of high pressure homogenization of crayfish shell were determined to be five cycles at a pressure of 400bar, which achieved a yield of 3.9g/L of GlcNAc from 25g/L of crayfish shell in a batch enzymatic reaction over 1.5h. The results showed high pressure homogenization might be an efficient method for direct utilization of crayfish shell for enzymatic production of GlcNAc. Copyright © 2017 Elsevier Ltd. All rights reserved.

  15. Large-scale shell model calculations for the N=126 isotones Po-Pu

    International Nuclear Information System (INIS)

    Caurier, E.; Rejmund, M.; Grawe, H.

    2003-04-01

    Large-scale shell model calculations were performed in the full Z=82-126 proton model space π(Oh 9/2 , 1f 7/2 , Oi 13/2 , 2p 3/2 , 1f 5/2 , 2p 1/2 ) employing the code NATHAN. The modified Kuo-Herling interaction was used, no truncation was applied up to protactinium (Z=91) and seniority truncation beyond. The results are compared to experimental data including binding energies, level schemes and electromagnetic transition rates. An overall excellent agreement is obtained for states that can be described in this model space. Limitations of the approach with respect to excitations across the Z=82 and N=126 shells and deficiencies of the interaction are discussed. (orig.)

  16. Efficient simultaneous removal of U(VI) and Cu(II) from aqueous solution using core-shell nZVI@SA/CMC-Ca beads

    International Nuclear Information System (INIS)

    Shuhong Hu; Xiaoyan Lin; Wenhui Zhao; Ministry of Education, Sichuan; Xuegang Luo

    2018-01-01

    Core-shell nanoscale zero-valent iron@alginate/carboxymethyl cellulose sodium composite loaded with calcium (nZVI@SA/CMC-Ca) beads were synthesized in this study using coaxial electronic injection method. The adsorbent structure was characterized via FT-IR, SEM, EDX and XPS. The adsorption behavior of U(VI) and Cu(II) on core-shell nZVI@SA/CMC-Ca beads was studied under various experimental parameters like pH, contact time and temperature. The isotherm and the kinetic data, pertaining to the adsorption of U(VI) and Cu(II) by core-shell nZVI@SA/CMC-Ca beads obeyed both the Langmuir and Freundlich isotherms model and the pseudo-second-order kinetics model, respectively. The thermodynamic parameters revealed the spontaneous and endothermic nature of the adsorption. The experiment of regeneration and reusability suggested core-shell nZVI@SA/CMC-Ca bead was a regenerated material. (author)

  17. Systematic study of L shell ionization of heavry atoms by protons

    International Nuclear Information System (INIS)

    Barros Leite Filho, C.V. de.

    1977-01-01

    Cross sections for L-subshell ionization by proton impact have been determined for W, Au, Tl, Pb, Bi, Th and U over the projectile range 0.5-3.5 MeV. The measured X-ray production cross sections of the total L- Shell and of some well resolved lines or groups of lines are consistent with those obtained by different authors in the same regions of bombarding energies and atomic numbers. Ionization cross sections were obtained by using the above results and the experimental values for the relative radiative transition probabilities, fluorescente yelds and Coster-Kronig factors. Relative radiative decay rates were measured with a Si (Li) detection system. A graphical method was employed to analyze the X-ray spectra so obtained. The values of fluorescente and Coster-Kronig yields were taken from previously published experiments performed in this laboratory. The influence of these experimental data on the shape of cross section versus proton energy curves is discussed. Comparisons of the experimentally determined L-subshell ionization cross sections are made wuth calculations in the plane-wave Born approximation, semi-classical aproximation and binary encounter approximation. The large effect of binding-energy trajetory and relativistic corrections on the PWBA calculations, invalidates quantitative conclusions regarding agreement between experimental and theoretical values. Semi-classical arguments are presented, however, to explain some general aspects of the ionization cross section curves. (Author) [pt

  18. Atomic-level Electron Microscopy of Metal and Alloy Electrocatalysts

    DEFF Research Database (Denmark)

    Deiana, Davide

    , the elemental distribution of the PtxY, before and after the electrochemical tests, has been determined. A core-shell structure is formed after the ORR chemical treatment, with an alloyed core embedded by a ~1 nm Pt-rich shell, due to the segregation of the Y from the first few atomic layers of the particle...... was the only matching structure. In the case of Pd−Hg, a core-shell structure has been found, with a pure Pd core and a Pd-Hg shell. Through atomic resolution STEM, the structure of the alloy in the shell of different particles has been revealed, showing the formation of an ordered alloy structure....... flat surfaces and exposed to different sintering conditions. Ex situ STEM imaging has been used to monitor the variation of the particle dimensions through the analysis of particle area distributions. Clusters with a monomodal size distribution exhibited intrinsic sintering resistance on different...

  19. Core-shell structured ceramic nonwoven separators by atomic layer deposition for safe lithium-ion batteries

    Science.gov (United States)

    Shen, Xiu; Li, Chao; Shi, Chuan; Yang, Chaochao; Deng, Lei; Zhang, Wei; Peng, Longqing; Dai, Jianhui; Wu, Dezhi; Zhang, Peng; Zhao, Jinbao

    2018-05-01

    Safety is one of the most factors for lithium-ion batteries (LIBs). In this work, a novel kind of ceramic separator with high safety insurance is proposed. We fabricated the core-shell nanofiber separators for LIBs by atomic layer deposition (ALD) of 30 nm Al2O3 on the electrospinning nonwoven fiber of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP). The separators show a pretty high heat resistance up to 200 °C without any shrinkage, an excellent fire-resistant property and a wide electrochemical window. Besides, with higher uptake and ionic conductivity, cells assembled with the novel separator shows better electrochemical performance. The ALD produced separators exhibit great potential in elaborate products like 3C communications and in energy field with harsh requirements for safety such as electric vehicles. The application of ALD on polymer fiber membranes brings a new strategy and opportunity for improving the safety of the advanced LIBs.

  20. Quasi-spin method in the case of j-j coupling in a shell of equivalent atomic electrons

    International Nuclear Information System (INIS)

    Savichyus, E.G.; Kanyauskas, Yu.M.; Rudzikas, Z.B.

    1979-01-01

    Mathematical apparatus of the theory of multielectronic atoms and ions in the case of j-j coupling in a shell of equivalent electrons is built. Quasi-spin method is used. The scheme of the investigation is the following: 1. Tensorial properties of the operators in quasi-spin space are considered. 2. Matrix elements of these operators are built and with the help of Wigner-Eckart theorem the dependence of the matrix elements upon the projection, including the quasi-spin projection, of the quantity of electrons in jj-subshell, is determined. 3. Subgenealogical coefficients (genealogical coefficients presented in quasi-spin space) are determined and some of their properties are investigated. The tables of subgenealogical coefficients for j=5/2, 7/2 are presented

  1. A double copy for N=2 supergravity: a linearised tale told on-shell

    International Nuclear Information System (INIS)

    Cardoso, G.L.; Nagy, S.; Nampuri, S.

    2016-01-01

    We construct the on-shell double copy dictionary for linearised four-dimensional N=2 supergravity coupled to one vector multiplet with a quadratic prepotential. We apply this dictionary to the weak-field approximation of dyonic BPS black holes in this theory.

  2. A double copy for N=2 supergravity: a linearised tale told on-shell

    Energy Technology Data Exchange (ETDEWEB)

    Cardoso, G.L.; Nagy, S.; Nampuri, S. [Center for Mathematical Analysis, Geometry and Dynamical Systems, Department of Mathematics, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa (Portugal)

    2016-10-24

    We construct the on-shell double copy dictionary for linearised four-dimensional N=2 supergravity coupled to one vector multiplet with a quadratic prepotential. We apply this dictionary to the weak-field approximation of dyonic BPS black holes in this theory.

  3. Multiple ionization and coupling effects in L-subshell ionization of heavy atoms by oxygen ions

    International Nuclear Information System (INIS)

    Pajek, M.; Banas, D.; Semaniak, J.; Braziewicz, J.; Majewska, U.; Chojnacki, S.; Czyzewski, T.; Fijal, I.; Jaskola, M.; Glombik, A.; Kretschmer, W.; Trautmann, D.; Lapicki, G.; Mukoyama, T.

    2003-01-01

    The multiple-ionization and coupling effects in L-shell ionization of atoms by heavy-ion impact have been studied by measuring the L x-ray production cross sections in solid targets of Au, Bi, Th, and U bombarded by oxygen ions in the energy range 6.4-70 MeV. The measured L x-ray spectra were analyzed using the recently proposed method accounting for the multiple-ionization effects, such as x-ray line shifting and broadening, which enables one to obtain the ionization probabilities for outer shells. The L-subshell ionization cross sections have been obtained from measured x-ray production cross sections for resolved Lα 1,2 , Lγ 1 , and Lγ 2,3 transitions using the L-shell fluorescence and Coster-Kronig yields being substantially modified by the multiple ionization in the M and N shells. In particular, the effect of closing of strong L 1 -L 3 M 4,5 Coster-Kronig transitions in multiple-ionized atoms was evidenced and discussed. The experimental ionization cross sections for the L 1 , L 2 , and L 3 subshells have been compared with the predictions of the semiclassical approximation (SCA) and the ECPSSR theory that includes the corrections for the binding-polarization effect within the perturbed stationary states approximation, the projecticle energy loss, and Coulomb deflection effects as well as the relativistic description of inner-shell electrons. These approaches were further modified to include the L-subshell couplings within the ''coupled-subshell model'' (CSM). Both approaches, when modified for the coupling effects, are in better agreement with the data. Particularly, the predictions of the SCA-CSM calculations reproduce the experimental L-subshell ionization cross section reasonably well. Remaining discrepancies are discussed qualitatively, in terms of further modifications of the L-shell decay rates caused by a change of electronic wave functions in multiple-ionized atoms

  4. Photoionization of atoms encapsulated by cages using the power-exponential potential

    International Nuclear Information System (INIS)

    Lin, C Y; Ho, Y K

    2012-01-01

    The systems of confined atoms in cages have received considerable attention for decades due to interesting phenomena arising from the effect of cage environment on the atom. For early theoretical work based on empirical model potentials, the Dirac δ-potential, i.e. the so-called bubble potential, and the attractive short-range spherical shell potential are conventionally used for the description of interaction between the valence electron of confined atom and the cage. In this work, the power-exponential potential with a flexible confining shape is proposed to model the cages. The methods of complex scaling in the finite-element discrete variable representation are implemented to investigate the hydrogen, hydrogen-like ions and alkali metals encapsulated by the cages. The energy spectrum varying with the confining well depth exhibits avoided crossings. The influence of cage on atomic photoionization leading to the oscillation behaviour or the so-called confinement resonances in cross sections is demonstrated in a variety of confined atomic systems. In comparisons with existing predictions using the Dirac δ-potential and the attractive short-range spherical shell potentials, our results show the significant influence of cage thickness and smooth shell boundary on the photoionization. The drastic changes of cross sections due to the character of cage are presented and discussed for the encaged lithium and sodium atoms. The present model is useful for clarifying the boundary effect of confining shell on the endohedral atoms. (paper)

  5. Sequences of measures on atomic subalgebras of P(N) | Aizpuru ...

    African Journals Online (AJOL)

    Sequences of measures on atomic subalgebras of P(N). Antonio Aizpuru, Antonio Gutierrez-D´avila. Abstract. A vector form of Phillips' theorem, for atomic Boolean algebras with countably many atoms, is given. As a consequence we obtain a new characterization of weak compact sets of σ-additive measures. Quaestiones ...

  6. Ag@ZnO core-shell nanoparticles study by first principle: The structural, magnetic and optical properties

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, Hai-Xia [Department of Physics, University of Science and Technology Beijing, Beijing 100083 (China); Wang, Xiao-Xu [Department of Physics, University of Science and Technology Beijing, Beijing 100083 (China); Beijing Computing Center, Beijing 100094 (China); Hu, Yao-Wen [Department of Physics, Tsinghua University, Beijing 100084 (China); Song, Hong-Quan; Huo, Jin-Rong; Li, Lu [Department of Physics, University of Science and Technology Beijing, Beijing 100083 (China); Qian, Ping, E-mail: ustbqianp@163.com [Department of Physics, University of Science and Technology Beijing, Beijing 100083 (China); Song, Yu-Jun [Department of Physics, University of Science and Technology Beijing, Beijing 100083 (China)

    2016-12-15

    Ag@ZnO core-shell nanoparticles of around 72 atoms have been investigated by the density functional theory, revealing proving for the first time that the core-shell structure exhibits a shrinkage phenomenon from outer shell in agreement with the other studies in literatures. Our calculations predict that the Ag@ZnO core-shell structure is a ferromagnetic spin polarized state, and the magnetism mainly stems from the spin splitting of 2p electrons of O atoms. In addition, the total and partial DOS of Ag@ZnO indicate that the nanostructure is a half-metallic nanoparticle and has the characters of the p-type semiconductor. Furthermore, the optical properties calculations show that the absorption edge of Ag@ZnO have a red shift and good photocatalysis compare to that of the bulk ZnO. These results of the Ag@ZnO core-shell structure obtain a well agreement with the experimental measurement. - Graphical abstract: Geometric structure of (a) Ag@ZnO core-shell nanostructure; (b) the core of Ag; (c) the shell of ZnO The core-shell nanoparticle Ag@ZnO contains Ag inner core of radius of 4 Å and ZnO outer shell with thickness of 2 Å. Ag@ZnO core-shell nanoparticles of around 72 atoms have been proved for the first time that the core-shell structure exhibit a shrinkage phenomenon from outer shell. Our calculations predict that the Ag@ZnO core-shell structure is a half-metallic nanoparticle and has the characters of the p-type semiconductor. The absorption edge of Ag@ZnO have a red shift and get good photo-catalysis compare to that of the bulk ZnO.

  7. Nuclear shell effects in neutron-rich nuclei around N=20 and N=32,34

    International Nuclear Information System (INIS)

    Seidlitz, Michael

    2012-01-01

    Nuclear shell effects in neutron-rich nuclei around N=20 and N=32,34 were studied by means of reduced transition probabilities, i.e. B(E2) and B(M1) values. To this end a series of Coulomb-excitation experiments, employing radioactive 31 Mg and 29,30 Na beams, as well as a precise lifetime experiment of excited states in 56 Cr were performed. The collective properties of excited states of 31 Mg were the subject of a Coulomb-excitation experiment at REX-ISOLDE, CERN, employing a radioactive 31 Mg beam at a beam energy of 3.0 MeV/u. The beam intensity amounted to 3000 ions/s on average. The highly efficient MINIBALL setup was employed, consisting of eight HPGe cluster detectors for γ-ray detection and a segmented Si-detector for coincident particle detection. The level scheme of 31 Mg was extended. Spin and parity assignment of the observed 945 keV state yielded 5/2 + and its de-excitation is dominated by a strong collective M1 transition. Comparison of the transition probabilities of 30,31,32 Mg establishes that for the N=19 magnesium isotope not only the ground state but also excited states are largely dominated by a deformed pf intruder configuration. This implies that 31 Mg is part of the so-called ''island of inversion''. Coulomb-excitation experiments of radioactive 29,30 Na were carried out at REX-ISOLDE, CERN, at a final beam energy of 2.85 MeV/u. De-excitation γ rays were detected by the MINIBALL γ-ray spectrometer in coincidence with scattered particles in a segmented Si-detector. Despite rather low beam intensities transition probabilities to the first excited states were deduced. Results of very recently published experiments at MSU and TRIUMF could be largely confirmed and extended. The measured B(E2) values agree well with shell-model predictions, supporting the idea that in the sodium isotopic chain the ground-state wave function contains a significant intruder admixture already at N=18, with N=19 having an almost pure 2p2h deformed ground

  8. Metal shell technology based upon hollow jet instability

    International Nuclear Information System (INIS)

    Kendall, J.M.; Lee, M.C.; Wang, T.G.

    1982-01-01

    Spherical shells of submillimeter size are sought as ICF targets. Such shells must be dimensionally precise, smooth, of high strength, and composed of a high atomic number material. We describe a technology for the production of shells based upon the hydrodynamic instability of an annular jet of molten metal. We have produced shells in the 0.7--2.0 mm size range using tin as a test material. Specimens exhibit good sphericity, fair concentricity, and excellent finish over most of the surface. Work involving a gold--lead--antimony alloy is in progress. Droplets of this are amorphous and possess superior surface finish. The flow of tin models that of the alloy well; experiments on both metals show that the technique holds considerable promise

  9. Atomic layer deposition synthesis and evaluation of core–shell Pt-WC electrocatalysts

    International Nuclear Information System (INIS)

    Hsu, Irene J.; Chen, Jingguang G.; Jiang, Xiaoqiang; Willis, Brian G.

    2015-01-01

    Pt-WC core shell particles were produced using atomic layer deposition (ALD) to deposit Pt layers onto WC particle substrates. A range of Pt depositions were used to determine the growth mechanism for the Pt-WC powder system. TEM imaging and Cu stripping voltammetry found that Pt ALD growth on WC powder substrates was similar to that on WC thin films. However, excess free carbon was found to affect Pt ALD by blocking adsorption sites on WC. The Pt-WC samples were evaluated for the oxygen reduction reaction using a rotating disk electrode to obtain quantitative activity information. The mass and specific activities for the 30 and 50 ALD cycle samples were found to be comparable to a 10 wt. % Pt/C catalyst. However, higher overpotentials and lower limiting currents were observed with ALD Pt-WC compared to Pt/C catalysts, indicating that the oxygen reduction mechanism is not as efficient on Pt-WC as on bulk Pt. Additionally, these Pt-WC catalysts were used to demonstrate hydrogen evolution reaction activity and were found to perform as well as bulk Pt catalyst but with a fraction of the Pt loading, in agreement with the previous work on Pt-WC thin film catalysts

  10. Projected shell model description of N = 114 superdeformed isotone nuclei

    International Nuclear Information System (INIS)

    Guo, R S; Chen, L M; Chou, C H

    2006-01-01

    A systematic description of the yrast superdeformed (SD) bands in N 114, Z = 80-84 isotone nuclei using the projected shell model is presented. The calculated γ-ray energies, moment of inertia and M1 transitions are compared with the data for which spin is assigned. Excellent agreement with the available data for all isotones is obtained. The calculated electromagnetic properties provide a microscopic understanding of those measured nuclei. Some predictions in superdeformed nuclei are also discussed

  11. Universal cross sections for K-shell ionization by low-velocity protons; importance of relativistic and energy-loss effects

    International Nuclear Information System (INIS)

    Zander, A.R.; Lapicki, G.

    1981-01-01

    When Z 1 2 , inner-shell ionization of a target atom of atomic number Z 2 by a projectile of atomic number Z 1 occurs predominately via removal of an inner-shell electron to the target atom continuum (direct ionization). Electron capture contributes then insignificantly to the ionization, and thus the predictions of perturbativein-Z 1 /Z 2 theories of direct ionization can be tested through comparison with measured ionization cross sections. We present such a comparison with the recently reported data for K-shell ionization of the Z 2 =22, 26, 28, and 30 elements by 60-150 keV protons (Z 1 =1). These ionization cross sections were inferred from x-ray production measurements using Krause's fluorescence yields

  12. Determination of the N=16 Shell Closure at the Oxygen Drip Line

    International Nuclear Information System (INIS)

    Hoffman, C. R.; Tabor, S. L.; Baumann, T.; Bazin, D.; Schiller, A.; Brown, J.; Williams, T.; Christian, G.; Frank, N.; Peters, W. A.; Thoennessen, M.; DeYoung, P. A.; Mears, P.; Reith, J.; Peaslee, G.; Finck, J. E.; Scott, M. J.; Voss, P. J.; Hinnefeld, J.; Howes, R.

    2008-01-01

    The neutron unbound ground state of 25 O (Z=8, N=17) was observed for the first time in a proton knockout reaction from a 26 F beam. A single resonance was found in the invariant mass spectrum corresponding to a neutron decay energy of 770 -10 +20 keV with a total width of 172(30) keV. The N=16 shell gap was established to be 4.86(13) MeV by the energy difference between the ν1s 1/2 and ν0d 3/2 orbitals. The neutron separation energies for 25 O agree with the calculations of the universal sd shell model interaction. This interaction incorrectly predicts an 26 O ground state that is bound to two-neutron decay by 1 MeV, leading to a discrepancy between the theoretical calculations and experiment as to the particle stability of 26 O. The observed decay width was found to be on the order of a factor of 2 larger than the calculated single-particle width using a Woods-Saxon potential

  13. Core-shell structural nanodiamond@TiN supported Pt nanoparticles as a highly efficient and stable electrocatalyst for direct methanol fuel cells

    International Nuclear Information System (INIS)

    Zhao, Yuling; Wang, Yanhui; Dong, Liang; Zhang, Yan; Huang, Junjie; Zang, Jianbing; Lu, Jing; Xu, Xipeng

    2014-01-01

    Highlights: • Core-shell structural nanodiamond@TiN was used as a novel support for Pt catalysts. • The ND@TiN support possessed a high electrochemical stability than carbon black. • The Pt/ND@TiN showed a higher catalytic activity for MOR and ORR than the Pt/C. • The Pt/ND@TiN demonstrated a much better durability compared with the Pt/C. - Abstract: A novel core-shell support material was designed with nanodiamond (ND) as core possessed excellent stability and TiN as shell improved the conductivity of support. The nano-TiN shell was decorated on the surface of ND by annealing TiO 2 in nitrogen atmosphere, and the obtained ND@TiN was employed to support Pt nanoparticles (NPs). The ND@TiN support and Pt/ND@TiN electrocatalyst were characterized by X-ray diffraction and transmission electron microscopy. ND particles were coated uniformly by the TiN layer and Pt NPs with a mean size of 4.2 nm were highly dispersed on the surface of ND@TiN. The electrochemical results confirmed that the ND@TiN support possessed a much more stability than the carbon black and exhibited a bigger background current density than the ND. The Pt/ND@TiN catalyst showed higher catalytic activity and better stability in methanol oxidation and oxygen reduction reactions compared with the Pt/C and Pt/ND

  14. Dislocations in AlGaN: Core Structure, Atom Segregation, and Optical Properties.

    Science.gov (United States)

    Massabuau, Fabien C-P; Rhode, Sneha L; Horton, Matthew K; O'Hanlon, Thomas J; Kovács, András; Zielinski, Marcin S; Kappers, Menno J; Dunin-Borkowski, Rafal E; Humphreys, Colin J; Oliver, Rachel A

    2017-08-09

    We conducted a comprehensive investigation of dislocations in Al 0.46 Ga 0.54 N. Using aberration-corrected scanning transmission electron microscopy and energy dispersive X-ray spectroscopy, the atomic structure and atom distribution at the dislocation core have been examined. We report that the core configuration of dislocations in AlGaN is consistent with that of other materials in the III-Nitride system. However, we observed that the dissociation of mixed-type dislocations is impeded by alloying GaN with AlN, which is confirmed by our experimental observation of Ga and Al atom segregation in the tensile and compressive parts of the dislocations, respectively. Investigation of the optical properties of the dislocations shows that the atom segregation at dislocations has no significant effect on the intensity recorded by cathodoluminescence in the vicinity of the dislocations. These results are in contrast with the case of dislocations in In 0.09 Ga 0.91 N where segregation of In and Ga atoms also occurs but results in carrier localization limiting non-radiative recombination at the dislocation. This study therefore sheds light on why InGaN-based devices are generally more resilient to dislocations than their AlGaN-based counterparts.

  15. Extending synchrotron-based atomic physics experiments into the hard X-ray region

    International Nuclear Information System (INIS)

    LeBrun, T.

    1996-01-01

    The high-brightness, hard x-ray beams available from third-generation synchrotron sources are opening new opportunities to study the deepest inner shells of atoms, an area where little work has been done and phenomena not observed in less tightly bound inner-shells are manifested. In addition scattering processes which are weak at lower energies become important, providing another tool to investigate atomic structure as well as an opportunity to study photon/atom interactions beyond photoabsorption. In this contribution the authors discuss some of the issues related to extending synchrotron-based atomic physics experiments into the hard x-ray region from the physical and the experimental point of view. They close with a discussion of a technique, resonant Raman scattering, that may prove invaluable in determining the spectra of the very highly-excited states resulting from the excitation of deep inner shells

  16. Investigation of nitrogen atom production in Ar/N2 and He/N2 surface wave plasmas

    International Nuclear Information System (INIS)

    Tabbal, M.; Kazopoulo, M.; Christidis, T.; Isber, S.

    2000-01-01

    Full text: There is presently great interest in nitrogen plasmas for surface coating processes. Such as the deposition of nitride thin films and surface treatment of materials. Indeed, nitrogen plasmas have been used to nitride the surface of ferrous and non-ferrous materials in order to improve their surface properties such as resistance to corrosion and hardness. Moreover, the design and development of nitrogen atom sources could be essential for the synthesis of gallium nitride (GaN), a wide band-gap semiconductor whose properties have revolutionized the microelectronics and optoelectronics industries. Correlations have been established between the density of active species in the process, namely atomic nitrogen (N) produced by the discharge and GaN film properties. Thus, it is of fundamental importance to investigate the N-atom production mechanisms in such discharges. N-atom production has been studied in pure N 2 surface-wave plasmas (SWP), as a function of operating parameters, namely gas pressure and electrical power. These studies indicate that the increase in the gas temperature (T g ) limits the N-atom production. One possible way of enhancing the N 2 dissociation rate ([N]/[N 2 ]) in the plasma could be the use of gas mixtures such as Ar/N 2 or He/N 2 . the aim of this paper is to characterize an Ar/N 2 and He/N 2 surface-wave discharge (SWD) by optical emission spectroscopy (OES), in order to determine the optimal plasma conditions in terms of [N]/[N 2 ]. The plasma is generated by a radio frequency (40.68 MHz) wave launcher. The effect of mixing N 2 with Ar and He on the production of N-atoms in the plasma was investigated at varying experimental conditions, such as operating pressure (4.5 and 7.5 Torr), electrical power (40 to 120 W), at a total gas flow of 250 sccm. It was found that [N]/[N 2 ] increases with the partial pressure of Ar in the mixture by a factor of about 8 at 120W. Such an enhancement is reduced at lower incident powers. On the

  17. Preparation of N-Doped Composite Shell Encapsulated Iron Nanoparticles and Their Magnetic, Adsorptive, and Photocatalytic Properties

    Directory of Open Access Journals (Sweden)

    Caijing Shi

    2017-01-01

    Full Text Available The N-doped composite shell encapsulated iron nanoparticles (CSEINPs were prepared by DC arc discharge under nitrogen at 800°C, using the anode with high Fe content and good homogeneity. The morphology, microstructure, composition, and some properties of the N-doped CSEINPs were characterized by various characterization techniques. The results revealed that the shells of the N-doped CSEINPs were composed of homogeneously amorphous structure containing C, Fe, O, and N elements; the saturation magnetization (Ms and coercivity (Hc of them at room temperature were 130 emu/g and 194 Oe, respectively. Due to the surface structure and the electrostatic interaction, the N-doped CSEINPs are employed to remove methylene blue (MB from the waste solution, and they exhibited high adsorption properties and photocatalytic activity under irradiation of visible light (IVL. The kinetics of adsorption of MB on the N-doped CSEINPs was investigated and the recycling test was carried out. The formation mechanism of the N-doped CSEINPs is discussed briefly.

  18. Shell biofilm-associated nitrous oxide production in marine molluscs

    DEFF Research Database (Denmark)

    Heisterkamp, I.M.; Schramm, Andreas; Larsen, Lone Heimann

    2013-01-01

    Emission of the greenhouse gas nitrous oxide (N2O) from freshwater and terrestrial invertebrates has exclusively been ascribed to N2O production by ingested denitrifying bacteria in the anoxic gut of the animals. Our study of marine molluscs now shows that also microbial biofilms on shell surfaces...... are important sites of N2O production. The shell biofilms of Mytilus edulis, Littorina littorea and Hinia reticulata contributed 18-94% to the total animal-associated N2O emission. Nitrification and denitrification were equally important sources of N2O in shell biofilms as revealed by 15N-stable isotope...... mollusc species. Ammonium excretion by the animals was found to be sufficient to sustain N2O production in the shell biofilm. Apparently, the animals provide a nutrient-enriched microenvironment that stimulates growth and N2O production of the shell biofilm. This animal-induced stimulation...

  19. Engineered inorganic core/shell nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Mélinon, Patrice, E-mail: patrice.melinon@univ-lyon1.fr [Institut Lumière matière Université Claude Bernard Lyon 1 et CNRS et OMNT, Domaine Scientifique de la Doua, Bâtiment Léon Brillouin, 43 Boulevard du 11 Novembre 1918, F 69622 Villeurbanne (France); Begin-Colin, Sylvie [IPCMS et OMNT, 23 rue du Loess BP 43, 67034 STRASBOURG Cedex 2 (France); Duvail, Jean Luc [IMN UMR 6502 et OMNT Campus Sciences : 2 rue de la Houssinire, BP32229, 44322 Nantes Cedex3 (France); Gauffre, Fabienne [SPM et OMNT : Institut des sciences chimiques de Rennes - UMR 6226, 263 Avenue du General Leclerc, CS 74205, 35042 RENNES Cedex (France); Boime, Nathalie Herlin [IRAMIS-NIMBE, Laboratoire Francis Perrin (CEA CNRS URA 2453) et OMNT, Bat 522, CEA Saclay, 91191 Gif sur Yvette Cedex (France); Ledoux, Gilles [Institut Lumière Matière Université Claude Bernard Lyon 1 et CNRS et OMNT, Domaine Scientifique de la Doua, Bâtiment Alfred Kastler 43 Boulevard du 11 Novembre 1918 F 69622 Villeurbanne (France); Plain, Jérôme [Universit de technologie de Troyes LNIO-ICD, CNRS et OMNT 12 rue Marie Curie - CS 42060 - 10004 Troyes cedex (France); Reiss, Peter [CEA Grenoble, INAC-SPrAM, UMR 5819 CEA-CNRS-UJF et OMNT, Grenoble cedex 9 (France); Silly, Fabien [CEA, IRAMIS, SPEC, TITANS, CNRS 2464 et OMNT, F-91191 Gif sur Yvette (France); Warot-Fonrose, Bénédicte [CEMES-CNRS, Université de Toulouse et OMNT, 29 rue Jeanne Marvig F 31055 Toulouse (France)

    2014-10-20

    It has been for a long time recognized that nanoparticles are of great scientific interest as they are effectively a bridge between bulk materials and atomic structures. At first, size effects occurring in single elements have been studied. More recently, progress in chemical and physical synthesis routes permitted the preparation of more complex structures. Such structures take advantages of new adjustable parameters including stoichiometry, chemical ordering, shape and segregation opening new fields with tailored materials for biology, mechanics, optics magnetism, chemistry catalysis, solar cells and microelectronics. Among them, core/shell structures are a particular class of nanoparticles made with an inorganic core and one or several inorganic shell layer(s). In earlier work, the shell was merely used as a protective coating for the core. More recently, it has been shown that it is possible to tune the physical properties in a larger range than that of each material taken separately. The goal of the present review is to discuss the basic properties of the different types of core/shell nanoparticles including a large variety of heterostructures. We restrict ourselves on all inorganic (on inorganic/inorganic) core/shell structures. In the light of recent developments, the applications of inorganic core/shell particles are found in many fields including biology, chemistry, physics and engineering. In addition to a representative overview of the properties, general concepts based on solid state physics are considered for material selection and for identifying criteria linking the core/shell structure and its resulting properties. Chemical and physical routes for the synthesis and specific methods for the study of core/shell nanoparticle are briefly discussed.

  20. Some possible atomic physics experiments with 15 UD pelletron machine

    International Nuclear Information System (INIS)

    Mandal, A.

    1995-01-01

    Some possible experiments in atomic physics using medium energy heavy ion beam from the Pelletron are discussed. Main discussions is on x-ray spectroscopy using heavy ion beam. Different excitation mechanisms of inner atomic shells, experimental results and comparison with different theoretical models are presented. Effects of multiple vacancies in outer shells on K-shell ionisation, projectile charge state and target thickness effects are discussed. High resolution x-ray spectroscopy using curved crystal spectrometer is useful for studying these effects. Special emphasis is given to the study of quasi-molecular orbit (MO) formation during adiabatic collision of heavy ion with atom. Different aspects of MO x-ray study are presented. Other continuum x-rays e.g. radiative electron capture (REC), secondary electron Bremsstrahlung (SEB) nucleus-nucleus Bremsstrahlung (NNB) etc are also discussed. (author). 16 refs., 5 figs

  1. Counting Tm dopant atoms around GaN dots using high-angle annular dark field images

    International Nuclear Information System (INIS)

    Rouvière, J-L; Okuno, H; Jouneau, P H; Bayle-Guillemaud, P; Daudin, B

    2011-01-01

    High resolution Z-contrast STEM imaging is used to study the Tm doping of GaN quantum dots grown in AlN by molecular beam epitaxy (MBE). High-angle annular dark field (HAADF) imaging allows us to visualize directly individual Tm atoms in the AlN matrix and even to count the number of Tm atoms in a given AlN atomic column. A new visibility coefficient to determine quantitatively the number of Tm atoms in a given atomic column is introduced. It is based on locally integrated intensities rather than on peak intensities of HAADF images. STEM image simulations shows that this new visibility is less sensitive to the defocus-induced blurring or to the position of the Tm atom within the thin lamella. Most of the Tm atoms diffuse out of GaN dots. Tm atoms are found at different positions in the AlN matrix, (i) Above the wetting layer, Tm atoms are spread within a thickness of 14 AlN monolayers (MLs). (ii) Above the quantum dots all the Tm are located in the same plane situated at 2-3 MLs above the apex of the GaN dot, i.e. at a distance of 14 MLs from the wetting layer, (iii) In addition, Tm can diffuse very far from the GaN dot by following threading dislocations lines.

  2. Inner shell ionization accompanying nuclear collisions

    International Nuclear Information System (INIS)

    Sujkowski, Z.

    1987-01-01

    Selected phenomena leading to inner shell ionization and being of relevance for nuclear physics are discussed. The selection emphasizes the K-shell ionization induced in head-on collisions by fast light and medium-heavy ions. Cross-sections are reviewed. Effects of multiple inner shell ionization on the K X-ray spectra are illustrated with recent results. Implications for nuclear experiments are noted. Use of atomic observables as clocks for proton induced nuclear reactions is reviewed. Prospects for H.I. reactions are discussed. Preliminary experimental results on the direct K-shell ionization accompanying H.I. fusion reactions are presented. The post-collisional K-shell ionization due to internal conversion of γ-rays is discussed as the dominating contribution to the ionization for residues of dissipative nuclear reactions with Z > 40. Systematics of the corresponding K X-ray multiplicities are presented for rotational nuclei. These multiplicity values can be used for determining cross-sections for e.g. incomplete fusion reactions. Examples of such applications are given. Also discussed is the use of target K X-rays for normalization purposes and of the post-collisional, residue K X-rays in the studies of high spin phenomena. 96 references, 35 figures, 3 tables

  3. Advanced Kr Atomic Structure and Ionization Kinetics for Pinches on ZR

    Science.gov (United States)

    Dasgupta, Arati; Clark, Robert; Giuliani, John; Ouart, Nick; Davis, Jack; Jones, Brent; Ampleford, Dave; Hansen, Stephanie

    2011-10-01

    High fluence photon sources above 10 keV are a challenge for HED plasmas. This motivates Kr atomic modeling as its K-shell radiation starts at 13 keV. We have developed atomic structure and collisional-radiatve data for the full K-and L-shell and much of the M-shell using the the state-of-the-art Flexible Atomic Code. All relevant atomic collisional and radiative processes that affect ionization balance and are necessary to accurately model the pinch dynamics and the spectroscopic details of the emitted radiation are included in constructing the model. This non-LTE CRE model will be used to generate synthetic spectra for fixed densities and temperatures relevant for Kr gas-puff simulations in ZR. Work supported by DOE/NNSA. Sandia is a multi-program laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  4. Fabrication, thermal properties and thermal stabilities of microencapsulated n-alkane with poly(lauryl methacrylate) as shell

    International Nuclear Information System (INIS)

    Qiu, Xiaolin; Lu, Lixin; Wang, Ju; Tang, Guoyi; Song, Guolin

    2015-01-01

    Highlights: • Microencapsulation of octadecane and paraffin by crosslinked poly(lauryl methacrylate). • Octadecane microcapsules have a melting enthalpy of about 118 J g −1 . • Weight loss temperatures of the microcapsules were increased by 67 °C and 28 °C. • Phase change enthalpies decreased by around 10 wt% after 500 thermal cycles. • Foams with microcapsules can be applied for passive temperature control. - Abstract: Microencapsulation of n-octadecane or paraffin with poly(lauryl methacrylate) (PLMA) shell was performed by a suspension-like polymerization. The polymer shell was crosslinked by pentaerythritol tetraacrylate (PETRA). The surface morphologies of microcapsules were investigated by scanning electron microscopy (SEM). Phase change properties, thermal reliabilities and thermal stabilities of microcapsules were determined by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). The n-octadecane microcapsule exhibits higher melting enthalpy (118.0 J g −1 ) and crystallization enthalpy (108.3 J g −1 ) compared with the paraffin microcapsule. The thermal resistant temperatures were enhanced by more than 25 °C when n-alkanes were microencapsulated by PLMA. The PCM contents of microcapsules decreased by less than 4 wt% and 6 wt% after 500 and 1000 thermal cycles, respectively. Heat-up experiments indicated that microcapsule-treated foams exhibited upgraded thermal regulation capacities. Consequently, microencapsulated n-octadecane or paraffin with PLMA as shell possesses good potentials for heat storage and thermal regulation.

  5. Template-free synthesis of hierarchical yolk-shell Co and N codoped porous carbon microspheres with enhanced performance for oxygen reduction reaction

    Science.gov (United States)

    Chao, Shujun; Cui, Qian; Wang, Kui; Bai, Zhengyu; Yang, Lin; Qiao, Jinli

    2015-08-01

    The structures and compositions of materials have important influences on their performance. Herein, hierarchically structured yolk-shell Co and N codoped porous carbon microspheres (YS-Co/N-PCMs) have been successfully synthesized by using low-cost melamine, formaldehyde and cobalt acetate as raw materials via a facile template-free hydrothermal method and a subsequent pyrolysis. The formation process of the yolk-shell precursor is systematically investigated, involving a morphological evolution process from solid microspheres, ultrathin and wrinkled shells wrap, to yolk-shell structure formation. More importantly, the unique structure combines the favorable features towards oxygen reduction reaction (ORR), such as high surface area, sufficient Co-Nx and graphitic N active sites and suitable pore structures. As a result, the YS-Co/N-PCMs catalyst shows high catalytic activity for ORR in alkaline media for fuel cells, which not only outperforms commercial Pt-based catalysts in terms of resistance to methanol crossover and long-time stability, but is also better than many non-precious metal doped carbon-based catalysts reported previously. In addition, the YS-Co/N-PCMs catalyst also has high catalytic activity toward oxygen evolution reaction (OER). Therefore, the YS-Co/N-PCMs catalyst may serve as a promising alternative to Pt/C catalyst for ORR and OER in alkaline media.

  6. Core–shell interaction and its impact on the optical absorption of pure and doped core-shell CdSe/ZnSe nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xinqin; Cui, Yingqi; Zeng, Qun; Yang, Mingli, E-mail: myang@scu.edu.cn [Institute of Atomic and Molecular Physics, Key Laboratory of High Energy Density Physics and Technology of Ministry of Education, Sichuan University, Chengdu 610065 (China); Yu, Shengping [College of Chemistry and Environment Protection Engineering, Southwest University for Nationalities, Chengdu 610041 (China)

    2016-04-07

    The structural, electronic, and optical properties of core-shell nanoclusters, (CdSe){sub x}@(CdSe){sub y} and their Zn-substituted complexes of x = 2–4 and y = 16–28, were studied with density functional theory calculations. The substitution was applied in the cores, the shells, and/or the whole clusters. All these clusters are characterized by their core-shell structures in which the core-shell interaction was found different from those in core or in shell, as reflected by their bondlengths, volumes, and binding energies. Moreover, the core and shell combine together to compose a new cluster with electronic and optical properties different from those of separated individuals, as reflected by their HOMO-LUMO gaps and optical absorptions. With the substitution of Cd by Zn, the structural, electronic, and optical properties of clusters change regularly. The binding energy increases with Zn content, attributed to the strong Zn–Se bonding. For the same core/shell, the structure with a CdSe shell/core has a narrower gap than that with a ZnSe shell/core. The optical absorption spectra also change accordingly with Zn substitution. The peaks blueshift with increasing Zn concentration, accompanying with shape variations in case large number of Cd atoms are substituted. Our calculations reveal the core-shell interaction and its influence on the electronic and optical properties of the core-shell clusters, suggesting a composition–structure–property relationship for the design of core-shell CdSe and ZnSe nanoclusters.

  7. Study of shell closures N=40 and N=50 in neutron-rich nuclei; Etude des fermetures de couches N=40 et N=50 dans les noyaux riches en neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Perru, O

    2004-12-01

    For this thesis I have studied 2 neutron shell closures: N=40 and N=50. On N=50, an experiment was done in February 2001 on the ISOL line PARRNe, the issue was to measure the first excited states of {sup 83}Ge (Z=32, N=51) by studying the beta decay of {sup 83}Ga produced by fission of {sup 238}U.The extreme precision of the experimental device, with the operation of hot plasma ion sources made it possible to reach spectroscopic information of the Ge isotopes beyond the magic gap N=50. Two transitions have been attributed to {sup 83}Ge: at 867 keV and at 1238 keV. The level scheme of {sup 83}Ge could be interpreted in terms of weak coupling: the excited states of this nucleus are due to the couplings between the single neutron beyond N=50 and the remaining nucleons.On N=40, we wanted to determine the transition probability between ground state and first excited state, called B(E2), in {sup 70}Ni (N=42) and {sup 74}Zn (N=44) from Coulomb excitation. These exotic nuclei are produced by fragmentation of a primary beam of {sup 76}Ge on a target of {sup 58}Ni, selected by the spectrometer LISE, then interact with a secondary {sup 208}Pb target to induce the Coulomb excitation. At the end of this analysis, the following values have been obtained: B(E2,{sup 70}Ni)=860(170) e{sup 2}fm{sup 4}, B(E2,{sup 74}Zn)=1960(140) e{sup 2}fm{sup 4}. These values have been compared on the one hand to variational calculations which I have realised, on the other hand to published shell model calculations.These calculations point out the complex aspect of the Ni nuclei, which do not seem to have a typical behaviour of semi magic nuclei although they are located on a closed shell in protons (Z=28). (author)

  8. Construction of carbon nanoflakes shell on CuO nanowires core as enhanced core/shell arrays anode of lithium ion batteries

    International Nuclear Information System (INIS)

    Cao, F.; Xia, X.H.; Pan, G.X.; Chen, J.; Zhang, Y.J.

    2015-01-01

    Highlights: • CuO/C core/shell nanowire arrays are prepared by electro-deposition + ALD method. • Carbon shell is favorable for structural stability. • CuO/C core/shell arrays show enhanced cycle stability and high capacity. - Abstract: Tailored metal oxide/carbon composite structures have attracted great attention due to potential synergistic effects and enhanced properties. In this work, novel CuO/C core/shell nanowire arrays are prepared by the combination of electro-deposition of CuO and atomic-layer-deposition-assisted formation of carbon nanoflakes shell. The CuO nanowires with diameters of ∼200 nm are homogenously coated by carbon nanoflakes shell. When evaluated as anode materials for lithium ion batteries (LIBs), compared to the unmodified CuO nanowire arrays, the CuO/C core/shell nanowire arrays exhibit improved electrochemical performances with higher capacity, better electrochemical reactivity and high-rate capability as well as superior cycling life (610 mAh g"−"1 at 0.5C after 290 cycles). The enhanced electrochemical performance is mainly attributed to the introduction of carbon flake shell in the core/shell nanowire arrays structure, which provides higher active material-electrolyte contact area, improved electrical conductivity, and better accommodation of volume change. The proposed method provides a new way for fabrication of high-performance metal oxides anodes of LIBs.

  9. Aqueous-phase synthesis and color-tuning of core/shell/shell inorganic nanocrystals consisting of ZnSe, (Cu, Mn)-doped ZnS, and ZnS

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Jongwan; Yoon, Sujin [Department of Chemistry and Research Institute for Natural Science, Hanyang University, Seoul, 133-791 (Korea, Republic of); Kim, Felix Sunjoo, E-mail: fskim@cau.ac.kr [School of Chemical Engineering and Materials Science, Chung-Ang University, Seoul, 156-756 (Korea, Republic of); Kim, Nakjoong, E-mail: kimnj@hanyang.ac.kr [Department of Chemistry and Research Institute for Natural Science, Hanyang University, Seoul, 133-791 (Korea, Republic of)

    2016-06-25

    We report synthesis of colloidal nanocrystals based on ZnSe core, (Cu,Mn)-doped ZnS inner-shell, and ZnS outer-shell by using an eco-friendly method and their optical properties. Synthesis of core/shell/shell nanocrystals was performed by using a one-pot/three-step colloidal method with 3-mercaptopropionic acid as a stabilizer in aqueous phase at low temperature. A double-shell structure was employed with inner-shell as a host for doping and outer-shell as a passivation layer for covering surface defects. Copper and manganese were introduced as single- or co-dopants during inner-shell formation, providing an effective means to control the emission color of the nanocrystals. The synthesized nanocrystals showed fluorescent emission ranging from blue to green, to white, and to orange, adjusted by doping components, amounts, and ratios. The photoluminescence quantum yields of the core/doped-shell/shell nanocrystals approached 36%. - Highlights: • ZnSe/ZnS:(Cu,Ms)/ZnS core/(doped)shell/shell nanocrystals were synthesized in an aqueous phase. • Emission color of nanocrystals was controlled from blue to white to orange by adjusting the atomic ratio of Cu and Mn co-dopants. • Photoluminescence quantum yields of the colloidal nanocrystals approached 36%.

  10. Position-controlled MOVPE growth and electro-optical characterization of core-shell InGaN/GaN microrod LEDs

    Science.gov (United States)

    Schimpke, Tilman; Lugauer, H.-J.; Avramescu, A.; Varghese, T.; Koller, A.; Hartmann, J.; Ledig, J.; Waag, A.; Strassburg, M.

    2016-03-01

    Today's InGaN-based white LEDs still suffer from a significant efficiency reduction at elevated current densities, the so-called "Droop". Core-shell microrods, with quantum wells (QWs) covering their entire surface, enable a tremendous increase in active area scaling with the rod's aspect ratio. Enlarging the active area on a given footprint area is a viable and cost effective route to mitigate the droop by effectively reducing the local current density. Microrods were grown in a large volume metal-organic vapor phase epitaxy (MOVPE) reactor on GaN-on-sapphire substrates with a thin, patterned SiO2 mask for position control. Out of the mask openings, pencil-shaped n-doped GaN microrod cores were grown under conditions favoring 3D growth. In a second growth step, these cores are covered with a shell containing a quantum well and a p-n junction to form LED structures. The emission from the QWs on the different facets was studied using resonant temperature-dependent photoluminescence (PL) and cathodoluminescence (CL) measurements. The crystal quality of the structures was investigated by transmission electron microscopy (TEM) showing the absence of extended defects like threading dislocations in the 3D core. In order to fabricate LED chips, dedicated processes were developed to accommodate for the special requirements of the 3D geometry. The electrical and optical properties of ensembles of tens of thousands microrods connected in parallel are discussed.

  11. Preparation and characterization of antibacterial Au/C core-shell composite

    Energy Technology Data Exchange (ETDEWEB)

    Gao Yanhong [Department of Chemistry and Institute of Nanochemistry, Jinan University, 601 Huangpudadaoxi Road, Guangzhou 510632, Guangdong (China); Centers for Disease Control and Prevention of Guangdong Province, Guangzhou 510300, Guangdong (China); Zhang Nianchun [Department of Chemistry and Institute of Nanochemistry, Jinan University, 601 Huangpudadaoxi Road, Guangzhou 510632, Guangdong (China); Zhong Yuwen [Centers for Disease Control and Prevention of Guangdong Province, Guangzhou 510300, Guangdong (China); Cai Huaihong [Department of Chemistry and Institute of Nanochemistry, Jinan University, 601 Huangpudadaoxi Road, Guangzhou 510632, Guangdong (China); Liu Yingliang, E-mail: tliuyl@jnu.edu.cn [Department of Chemistry and Institute of Nanochemistry, Jinan University, 601 Huangpudadaoxi Road, Guangzhou 510632, Guangdong (China)

    2010-09-01

    An environment-friendly oxidation-reduction method was used to prepare Au/C core-shell composite using carbon as core and gold as shell. The chemical structures and morphologies of Au/C core-shell composite and carbon sphere were characterized by X-ray diffraction, transmission electron microscope, energy dispersion X-ray spectrometry (EDS) and X-ray photoelectron spectroscopy (XPS). The antibacterial properties of the Au/C core-shell composite against Escherichia coli (E. coli), Staphylococcus aureus (S. aureus) and Candida albicans (C. albicans) were examined by the disk diffusion assay and minimal inhibition concentration (MIC) methods. In addition, antibacterial ability of Au/C core-shell composite was observed by atomic force microscope. Results demonstrated that gold homogeneously supported on the surface of carbon spheres without aggregation and showed efficient antibacterial abilities.

  12. Synthesis of triangular Au core-Ag shell nanoparticles

    International Nuclear Information System (INIS)

    Rai, Akhilesh; Chaudhary, Minakshi; Ahmad, Absar; Bhargava, Suresh; Sastry, Murali

    2007-01-01

    In this paper, we demonstrate a simple and reproducible method for the synthesis of triangular Au core-Ag shell nanoparticles. The triangular gold core is obtained by the reduction of gold ions by lemongrass extract. Utilizing the negative charge on the gold nanotriangles, silver ions are bound to their surface and thereafter reduced by ascorbic acid under alkaline conditions. The thickness of the silver shell may be modulated by varying the pH of the reaction medium. The formation of the Au core-Ag shell triangular nanostructures has been followed by UV-vis-NIR Spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy (TEM) and atomic force microscopy (AFM) measurements. The sharp vertices of the triangles coupled with the core-shell structure is expected to have potential for application in surface enhanced Raman spectroscopy and in the sensitive detection of biomolecules

  13. Subshell resolved L shell ionization of Bi and U induced by 16 - 45 keV electrons

    International Nuclear Information System (INIS)

    Rahangdale, Hitesh; Das, Pradipta K.; Saha, S.; Mitra, D.

    2015-01-01

    Electron induced inner-shell ionization is important for both fundamental and applied research. Ionization of outer atomic energy levels has been studied extensively than for inner levels. Knowledge of inner shell ionization cross sections is important in X-ray and Auger electron spectroscopy and in the fields of astrophysics, plasma physics, surface science and many more. At electron impact energies near the atomic binding energies the distortion of the wave functions from plane wave towards a spherical wave, due to the electrostatic field of the atoms, needs to be considered. The distorted wave Born approximation (DWBA) calculations, taking relativistic effects and exchange interaction into account, is used to estimate the K, L and M-shell ionization cross-section for the atoms. Earlier experiments on electron impact ionization studies focused mainly on K-shell ionization cross-section, while L and M-shell ionization data were hardly reported. A review of the existing L-shell ionization cross-section data shows that, while the X-ray production cross-sections by electron impact were reported quite a few times, the reporting of subshell resolved ionization cross-sections were rarely found near the ionization threshold region. In the present work, we have measured the X ray production cross-sections of different L lines of Bi and U induced by 16-45 keV electrons and converted the obtained values to the subshell specific ionization cross-sections. The experimental data are compared with the theoretical calculations based on the (DWBA) obtained from PENELOPE. To the best of our knowledge, the subshell resolved electron induced ionization cross-sections for the L-shell of Bi and U are reported here for the first time at the energy values near the corresponding ionization threshold. (author)

  14. Design of high-activity single-atom catalysts via n-p codoping

    Science.gov (United States)

    Wang, Xiaonan; Zhou, Haiyan; Zhang, Xiaoyang; Jia, Jianfeng; Wu, Haishun

    2018-03-01

    The large-scale synthesis of stable single-atom catalysts (SACs) in experiments remains a significant challenge due to high surface free energy of metal atom. Here, we propose a concise n-p codoping approach, and find it can not only disperse the relatively inexpensive metal, copper (Cu), onto boron (B)-doped graphene, but also result in high-activity SACs. We use CO oxidation on B/Cu codoped graphene as a prototype example, and demonstrate that: (1) a stable SAC can be formed by stronger electrostatic attraction between the metal atom (n-type Cu) and support (p-type B-doped graphene). (2) the energy barrier of the prototype CO oxidation on B/Cu codoped graphene is 0.536 eV by the Eley-Rideal mechanism. Further analysis shows that the spin selection rule can provide well theoretical insight into high activity of our suggested SAC. The concept of n-p codoping may lead to new strategy in large-scale synthesis of stable single-atom catalysts.

  15. Core-shell titanium dioxide-titanium nitride nanotube arrays with near-infrared plasmon resonances

    Science.gov (United States)

    Farsinezhad, Samira; Shanavas, Thariq; Mahdi, Najia; Askar, Abdelrahman M.; Kar, Piyush; Sharma, Himani; Shankar, Karthik

    2018-04-01

    Titanium nitride (TiN) is a ceramic with high electrical conductivity which in nanoparticle form, exhibits localized surface plasmon resonances (LSPRs) in the visible region of the solar spectrum. The ceramic nature of TiN coupled with its dielectric loss factor being comparable to that of gold, render it attractive for CMOS polarizers, refractory plasmonics, surface-enhanced Raman scattering and a whole host of sensing applications. We report core-shell TiO2-TiN nanotube arrays exhibiting LSPR peaks in the range 775-830 nm achieved by a simple, solution-based, low cost, large area-compatible fabrication route that does not involve laser-writing or lithography. Self-organized, highly ordered TiO2 nanotube arrays were grown by electrochemical anodization of Ti thin films on fluorine-doped tin oxide-coated glass substrates and then conformally coated with a thin layer of TiN using atomic layer deposition. The effects of varying the TiN layer thickness and thermal annealing on the LSPR profiles were also investigated. Modeling the TiO2-TiN core-shell nanotube structure using two different approaches, one employing effective medium approximations coupled with Fresnel coefficients, resulted in calculated optical spectra that closely matched the experimentally measured spectra. Modeling provided the insight that the observed near-infrared resonance was not collective in nature, and was mainly attributable to the longitudinal resonance of annular nanotube-like TiN particles redshifted due to the presence of the higher permittivity TiO2 matrix. The resulting TiO2-TiN core-shell nanotube structures also function as visible light responsive photocatalysts, as evidenced by their photoelectrochemical water-splitting performance under light emitting diode illumination using 400, 430 and 500 nm photons.

  16. Study of the closure of the nuclear shells N = 16, 20, 28 and 40; Etudes des fermetures de couches nucleaires N=16, 20, 28 et 40

    Energy Technology Data Exchange (ETDEWEB)

    Sorlin, O

    2005-12-15

    There are 2 types of nuclear shell closures: one is associated to a number of the harmonic oscillator, typically N = 20 and 40, and the other is a consequence of the spin-orbital interaction that produces magic numbers such as N = 28, 50, 82 and N = 126. The first part of this work deals with the knowledge accumulated around the closure of the N = 28 shell. 3 means of investigation have been used: -) the study of beta decay nuclei (K{sup 47}, Ar{sup 46}, S{sup 44}, Si{sup 42} and Cl{sup 45}), -) the on-line spectroscopy of nuclei around N = 28, and -) the study of Ar{sup 45} and Ar{sup 47} through transfer reactions. The second part is dedicated to results concerning the nuclear structure of nuclei around N = 14-20 and around N = 40. (A.C.)

  17. Interaction of complex atoms with radiation

    International Nuclear Information System (INIS)

    Amus'ya, M.Ya.

    1984-01-01

    Different manifestations of multielectron atomic structure under photoionization are discussed. Collectivization of external electron shells essential both in production cross section and in angular distribution as well as in photoelectron polarization are noted. In a wide range of quantum energies (of the order of ionization potential) an incident electron scattering on the atom irradiates quite differently than on the potential. It polarizes atoms mainly dipolarly, and virtually excited atom emits ''bremsstrahlung'' quantum. With energy growth of the incident electron at small momentum transferred to it by the atom the role of the second mechanism turns to be determinant

  18. Determination and Quantification of metals in the shells of Crassostrea virginica after the Deepwater Horizon oil spill utilizing Atomic Absorption Spectrometry.

    Science.gov (United States)

    Roopnarine, D.; Patel, S.; Roopnarine, P.; Giarikos, D.; Anderson, L. C.

    2017-12-01

    The Deepwater Horizon (DWH) oil rig explosion on April 20, 2010 resulted in the release of 685,000 tons of crude oil into the Gulf of Mexico (GOM) over a period of three months. There were obvious immediate effects, but the long-term ramifications are still being studied. The primary constituent of crude oil is hydrocarbons with other organic compounds containing nitrogen, oxygen and sulfur. There are also a number of trace metals with the most abundant frequently being iron, nickel, copper and vanadium. These do not degrade like organic materials. However, the exact composition varies among the production sites. The oil from the DWH rig was classified as light crude which is moderately volatile. Natural oil seeps occur in the environment, but the DWH spill represented an acute impact. Trace amounts of heavy metals are a normal part of the composition of marine organisms, but can be toxic in high concentrations. Bivalved molluscs bioaccumulate heavy metals in their tissues and shells, and are therefore often useful as monitors of environmental pollution. We thus used the Eastern oyster Crassostrea virginica to determine the impact of the spill by measuring the concentrations of metals in the shells utilizing flame emission atomic absorption spectrometry. We focused on the hypothesis that DWH spill exposure resulted in an increase in metal uptake into the shells. Specimens spanned the years 2010 to 2014 and ranged from Grand Isle, LA to Apalachicola Bay, Fl. Vanadium had the greatest concentration in the shells, and along with copper, cadmium, zinc and iron displayed an upward trend of increase from 2010 to 2013, with a decline in 2014. However there was unexpected variability, as the specimens from Apalachicola Bay, Fl had higher levels of vanadium when compared to those from Grand Isle, LA. Ongoing work includes an increase of sample sizes from the same geographic localities and time period.

  19. Electronic structure and magnetic properties of substitutional transition-metal atoms in GaN nanotubes

    International Nuclear Information System (INIS)

    Zhang Min; Shi Jun-Jie

    2014-01-01

    The electronic structure and magnetic properties of the transition-metal (TM) atoms (Sc—Zn, Pt and Au) doped zigzag GaN single-walled nanotubes (NTs) are investigated using first-principles spin-polarized density functional calculations. Our results show that the bindings of all TM atoms are stable with the binding energy in the range of 6–16 eV. The Sc- and V-doped GaN NTs exhibit a nonmagnetic behavior. The GaN NTs doped with Ti, Mn, Ni, Cu and Pt are antiferromagnetic. On the contrary, the Cr-, Fe-, Co-, Zn- and Au-doped GaN NTs show the ferromagnetic characteristics. The Mn- and Co-doped GaN NTs induce the largest local moment of 4μ B among these TM atoms. The local magnetic moment is dominated by the contribution from the substitutional TM atom and the N atoms bonded with it. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  20. A Hartree-Fock program for atomic structure calculations

    International Nuclear Information System (INIS)

    Mitroy, J.

    1999-01-01

    The Hartree-Fock equations for a general open shell atom are described. The matrix equations that result when the single particle orbitals are written in terms of a linear combination of analytic basis functions are derived. Attention is paid to the complexities that occur when open shells are present. The specifics of a working FORTRAN program which is available for public use are described. The program has the flexibility to handle either Slater-type orbitals or Gaussian-type orbitals. It can be obtained over the internet at http://lacebark.ntu.edu.au/j_mitroy/research/atomic.htm Copyright (1999) CSIRO Australia

  1. Change in the conversion rate for the E3-isomer sup(235m)U (76,8 eV; 1/2+ → 7/2-) at variation of configurations of the valence band of the atomic shell

    International Nuclear Information System (INIS)

    Grechukhin, D.P.; Soldatov, A.A.

    1983-01-01

    In the framework of the relativistic Hartree-Fock-Slater method, a change of the conversion rate lambda for the E3 isomer (at the transition energy of h/2πω=77 eV) with respect to the rate lambda for the normal configuration of uranium atom, (7ssup(1/2)sup(2)(6dsup(3/2))sup(1)(5fsup(5/2))sup(3), is calcUlated for 14 configurations of the valence band of the atomic shell, including considerable variations of the occupation numbers in 6d, 7s, and 5f orbits. A very strong change Δlambda/lambda 1 is found to be due to variation of the occupation number for the 5f orbit (ΔN(5f) not equal to 0); the change amounts to about 8% per ΔN(5f)=+-1, that is an order of magnitude higher than Δlambda/lambda 1 due to variations of the occupation numbers for other orbits in the cases where N(5f)=const. Though the direct contribution from the 5f electrons to the conversion is very small ( 1 for ΔN(5f) not equal to 0. A rigid correlation between the partial conversion rate and the r. m. s. radius of the orbit is obtained for 6p orbits

  2. Fabrication, thermal properties and thermal stabilities of microencapsulated n-alkane with poly(lauryl methacrylate) as shell

    Energy Technology Data Exchange (ETDEWEB)

    Qiu, Xiaolin, E-mail: shirleyqiu2009@gmail.com [Jiangsu Key Laboratory of Advanced Food Manufacturing Equipment and Technology, School of Mechanical Engineering, Jiangnan University, Wuxi 214122 (China); Lu, Lixin; Wang, Ju [Jiangsu Key Laboratory of Advanced Food Manufacturing Equipment and Technology, School of Mechanical Engineering, Jiangnan University, Wuxi 214122 (China); Tang, Guoyi [Advanced Materials Institute and Clearer Production Key Laboratory, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055 (China); Key Laboratory of Advanced Materials, Department of Materials Science and Engineering, Tsinghua University, Haidian District, Beijing 100084 (China); Song, Guolin [Advanced Materials Institute and Clearer Production Key Laboratory, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055 (China)

    2015-11-20

    Highlights: • Microencapsulation of octadecane and paraffin by crosslinked poly(lauryl methacrylate). • Octadecane microcapsules have a melting enthalpy of about 118 J g{sup −1}. • Weight loss temperatures of the microcapsules were increased by 67 °C and 28 °C. • Phase change enthalpies decreased by around 10 wt% after 500 thermal cycles. • Foams with microcapsules can be applied for passive temperature control. - Abstract: Microencapsulation of n-octadecane or paraffin with poly(lauryl methacrylate) (PLMA) shell was performed by a suspension-like polymerization. The polymer shell was crosslinked by pentaerythritol tetraacrylate (PETRA). The surface morphologies of microcapsules were investigated by scanning electron microscopy (SEM). Phase change properties, thermal reliabilities and thermal stabilities of microcapsules were determined by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). The n-octadecane microcapsule exhibits higher melting enthalpy (118.0 J g{sup −1}) and crystallization enthalpy (108.3 J g{sup −1}) compared with the paraffin microcapsule. The thermal resistant temperatures were enhanced by more than 25 °C when n-alkanes were microencapsulated by PLMA. The PCM contents of microcapsules decreased by less than 4 wt% and 6 wt% after 500 and 1000 thermal cycles, respectively. Heat-up experiments indicated that microcapsule-treated foams exhibited upgraded thermal regulation capacities. Consequently, microencapsulated n-octadecane or paraffin with PLMA as shell possesses good potentials for heat storage and thermal regulation.

  3. process for K-shell ionization of atoms

    Indian Academy of Sciences (India)

    Department of Physics, College of Science Campus, M.L.S. University, Udaipur 313 002, ... been expressed as a product of kinematical factors and atomic structure functions. The ..... AL on energy is through two factors in an involved way.

  4. Enhanced visible light photocatalytic activity in SnO{sub 2}@g-C{sub 3}N{sub 4} core-shell structures

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Hao; Zhao, Xiaoru, E-mail: xrzhao@nwpu.edu.cn; Duan, Libing; Liu, Ruidi; Li, Hui

    2017-04-15

    Highlights: • Novel SnO{sub 2}@g-C{sub 3}N{sub 4} core-shell structures were successfully synthesized. • The core-shell structures exhibited enhanced visible light photocatalytic activity. • The enhanced photocatalytic activity was due to synergic action of SnO{sub 2} and g-C{sub 3}N{sub 4}. - Abstract: SnO{sub 2}@g-C{sub 3}N{sub 4} core-shell structures were successfully synthesized by simple calcination of SnO{sub 2} microspheres and urea in a muffle furnace. The investigation of morphologies and microstructures showed that g-C{sub 3}N{sub 4} was wrapped tightly on the surface of SnO{sub 2} microspheres with large intimate interface contact areas between the g-C{sub 3}N{sub 4} shells and SnO{sub 2} cores. The X-ray photoelectron spectroscopy results and photoluminescence spectra demonstrated that the intimate interface contacts could facilitate the transfer and separation of the photogenerated charge carriers at their interface, thus the recombination of the photogenerated electron-hole pairs was impeded. The photocatalytic activity of the synthesized composites was evaluated by the photodegradation of methyl orange under visible light irradiation. It was found that SnO{sub 2}@g-C{sub 3}N{sub 4} exhibited higher photodegradation rate (k = 0.013 min{sup −1}) than that of g-C{sub 3}N{sub 4} (k = 0.008 min{sup −1}) and pure SnO{sub 2}. The enhanced photocatalytic activity could be attributed to the synergic action of SnO{sub 2} and g-C{sub 3}N{sub 4}.

  5. Study of neutron-rich nuclei structure around the N=28 shell closure using the in-beam gamma spectroscopy technique

    International Nuclear Information System (INIS)

    Bastin, B.

    2007-10-01

    For a few years now, a loss of magicity in neutron-rich nuclei near the neutron drip-line at N=28 has been suggested and observed. Deformation in these nuclei has been observed. The deformation was explained in S isotopes as being due to a moderate reduction of the N=28 shell closure together with a proton induced collectivity originating from the near degeneracy of the proton d3/2 and s1/2 orbitals. As a consequence, the observed deformation seems to result from a subtle interplay between neutron and proton excitations. Since the proton configuration in the Si isotopes is expected to be more stable due to the Z=14 sub-shell gap, 42 Si was considered as a key nucleus in order to distinguish the different effects responsible for the structural changes observed at N=28. Even if it is at the limits of our technical possibilities, an in-beam gamma-spectroscopy experiment using two-step fragmentation and one or several nucleons knockout reaction mechanisms was performed at GANIL. The measurement of the energy of the first excited state in 42 Si, combined with the observation of 38,40 Si and the spectroscopy of 41,43 P, has given evidence for the loss of magicity at N=28 far from stability. Modifications of the effective interaction used in modern shell model calculations have been completed following this investigation, increasing its predictive character. This study confirms the role of the tensor force and the density dependence of the spin-orbit interaction in the collapse of the N=28 shell closure. (author)

  6. Laser method of free atom nuclei orientation

    International Nuclear Information System (INIS)

    Barabanov, A.L.

    1987-01-01

    Orientation process of free atom (atoms in beams) nuclei, scattering quanta of circularly polarized laser radiation is considered. A method for the evaluation of nuclei orientation parameters is developed. It is shown that in the process of pumping between the ground and first excited atomic states with electron shell spins J 1 and J 2 , so that J 2 = J 1 + 1, a complete orientation of nuclei can be attained

  7. Shell stabilization of super- and hyperheavy nuclei without magic gaps

    International Nuclear Information System (INIS)

    Bender, M.; Nazarewicz, W.; Oak Ridge National Lab., TN; Warsaw Univ.; Reinhard, P.G.; Oak Ridge National Lab., TN

    2001-05-01

    Quantum stabilization of superheavy elements is quantified in terms of the shell-correction energy. We compute the shell correction using self-consistent nuclear models: the non-relativistic Skyrme-Hartree-Fock approach and the relativistic mean-field model, for a number of parametrizations. All the forces applied predict a broad valley of shell stabilization around Z = 120 and N = 172-184. We also predict two broad regions of shell stabilization in hyperheavy elements with N ∼ 258 and N ∼ 308. Due to the large single-particle level density, shell corrections in the superheavy elements differ markedly from those in lighter nuclei. With increasing proton and neutron numbers, the regions of nuclei stabilized by shell effects become poorly localized in particle number, and the familiar pattern of shells separated by magic gaps is basically gone. (orig.)

  8. Production of n-rich Nuclei along the Closed Shell N=126 in the collision 136Xe + 208Pb @E lab =870 MeV

    Science.gov (United States)

    Quero, D.; Vardaci, E.; Kozulin, E. M.; Zagrebaev, V. A.; Corradi, L.; Pulcini, A.; La Rana, G.; Itkis, I. M.; Knyazheva, G. N.; Novikov, K.; Harca, I.; Fioretto, E.; Stefanini, A. M.; Montanari, D.; Montagnoli, G.; Scarlassara, F.; Szilner, S.; Mijatović, T.; Trzaska, W. H.

    2018-05-01

    Multi-nucleon transfer reactions are nowadays the only known mean to produce neutron-rich nuclei in the Terra Incognita. The closed-shell region N=126 is crucial for both studying shell-quenching in exotic nuclei and the r-process, being its last “waiting-point”. The choice of suitable reactions is challenging and a favorable case is 136Xe+208Pb, near the Coulomb barrier, because their neutron shell-closures play a stabilizing role, favoring the proton-transfer from lead to xenon. TOF-TOF data were analyzed to reconstruct the mass-energy distribution of the primary fragments. Preliminary results of an experiment held at Laboratori Nazionali di Legnaro with PRISMA, aimed at A and Z identification of the products, will be shown.

  9. The influence of (n-n{sup '})-mixing processes in He*(n)+He(1s{sup 2}) collisions on He*(n) atoms' populations in weakly ionized helium plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Mihajlov, A.A. [Institute of Physics, P.O. Box 57, 11001 Belgrade (Serbia and Montenegro); Ignjatovic, Lj.M. [Institute of Physics, P.O. Box 57, 11001 Belgrade (Serbia)], E-mail: ljuba@phy.bg.ac.yu; Sreckovic, V.A. [Institute of Physics, P.O. Box 57, 11001 Belgrade (Serbia); Djuric, Z. [Silvaco Data Systems, Compass Point, St Ives PE27 5JL (United Kingdom)

    2008-03-15

    The results of semi-classical calculations of rate coefficients of (n-n{sup '})-mixing processes due to collisions of Rydberg atoms He*(n) with He(1s{sup 2}) atoms are presented. It is assumed that these processes are caused by the resonant energy exchange within the electron component of He*(n)+He collision system. The method is realized through the numerical simulation of the (n-n{sup '})-mixing processes, and is applied for calculations of the corresponding rate coefficients. The calculations are performed for the principal quantum numbers n,n{sup '} in ranges 4{<=}n{sup '}{<=}10, and the atom and electron temperatures, T{sub a},T{sub e}, in domains 5000K{<=}T{sub a}{<=}T{sub e}{<=}20000K. It is shown that the (n-n{sup '})-mixing processes can significantly influence the populations of Rydberg atoms in non-equilibrium weakly ionized helium plasmas with ionization degree {approx}10{sup -4}. Therefore, these processes have to be included in the appropriate models of such plasmas.

  10. Microscopic description of quadrupole collectivity in neutron-rich nuclei across the N = 126 shell closure

    Science.gov (United States)

    Rodríguez-Guzmán, R.; Robledo, L. M.; Sharma, M. M.

    2015-06-01

    The quadrupole collectivity in Nd, Sm, Gd, Dy, Er, Yb, Hf and W nuclei with neutron numbers 122 ≤ N ≤ 156 is studied, both at the mean field level and beyond, using the Gogny energy density functional. Besides the robustness of the N = 126 neutron shell closure, it is shown that the onset of static deformations in those isotopic chains with increasing neutron number leads to an enhanced stability and further extends the corresponding two-neutron drip lines far beyond what could be expected from spherical calculations. Independence of the mean-field predictions with respect to the particular version of the Gogny energy density functional employed is demonstrated by comparing results based on the D1S and D1M parameter sets. Correlations beyond mean field are taken into account in the framework of the angular momentum projected generator coordinate method calculation. It is shown that N = 126 remains a robust neutron magic number when dynamical effects are included. The analysis of the collective wave functions, average deformations and excitation energies indicate that, with increasing neutron number, the zero-point quantum corrections lead to dominant prolate configurations in the 0{1/+}, 0{2/+}, 2{1/+} and 2{2/+} states of the studied nuclei. Moreover, those dynamical deformation effects provide an enhanced stability that further supports the mean-field predictions, corroborating a shift of the r-process path to higher neutron numbers. Beyond mean-field calculations provide a smaller shell gap at N = 126 than the mean-field one in good agreement with previous theoretical studies. However, the shell gap still remains strong enough in the two-neutron drip lines.

  11. Effects of the fullerene (C{sub 60}) potential and position of the atom (A) on spectral characteristics of endohedral atoms A and C{sub 60}

    Energy Technology Data Exchange (ETDEWEB)

    Baltenkov, A S [Arifov Institute of Electronics, 100125 Tashkent (Uzbekistan); Becker, U [Fritz-Haber-Institute der Max-Planck-Gesellschaft, D-14195 Berlin (Germany); Manson, S T [Department of Physics and Astronomy, Georgia State University, Atlanta, GA 30303 (United States); Msezane, A Z, E-mail: arkbalt@mail.r, E-mail: becker@fhi-berlin.mpg.d, E-mail: manson@phy-astr.gsu.ed, E-mail: amsezane@cau.ed [Center for Theoretical Studies of Physical Systems, Clark Atlanta University, Atlanta, GA 30314 (United States)

    2010-06-14

    Within the framework of a model representing the potential of a C{sub 60} cage as a spherical electro-neutral layer U(r) formed by smeared carbon atoms, the effect of the details of the potential on spectral characteristics of atoms localized inside the fullerene shell has been studied. Using examples of encapsulated H and He atoms, it is shown that for potential shell thickness not exceeding 1.3-1.5 au, confinement resonance oscillations in the photoionization cross section weakly depend on the shape of the function U(r). With increasing width of the potential well, the confinement resonances in the energy dependence of the photoionization cross section disappear. In addition, it is demonstrated that displacing the doped atom from the centre of the cavity also diminishes the amplitude of the confinement resonance.

  12. A dynamical atomic simulation for the Ni-Al Wulff nanoparticle

    International Nuclear Information System (INIS)

    Tang, Jianfeng; Yang, Jianyu

    2013-01-01

    Ni-Al bimetallic nanoparticle structures are studied from a kinetic point of view. The diffusion and growth of Ni (or Al) atoms on Al (or Ni) cores with the Wulff structure are simulated by molecular dynamics and nudged elastic band methods. An analytic embedded atom model is applied to the two metals. The energy barriers of several typical diffusion processes of the adatoms on the nanoparticle surface are calculated. Results show that the incorporation of the Ni atoms into the Al core easily occurs, and the reverse process does not readily proceed. The growth simulations reveal that a better core-shell nanoparticle is obtained when the Al atoms are deposited on the Ni core at lower temperatures, and the deposition of the Ni atoms on the Al core leads to an amorphous surface. - Highlights: • The diffusion barrier of Ni (or Al) on Al (or Ni) Wulff nanoparticle is studied. • Ni atom can diffuse easily into Al core, and Al atom generally segregate on surface. • A core-shell nanoparticle is obtained for the deposition of Al atoms on Ni core. • Amorphous nanoparticle surface is obtained by depositing Ni atoms on Al core

  13. Determination of K shell absorption jump factors and jump ratios of 3d transition metals by measuring K shell fluorescence parameters.

    Science.gov (United States)

    Kaçal, Mustafa Recep; Han, İbrahim; Akman, Ferdi

    2015-01-01

    Energy dispersive X-ray fluorescence technique (EDXRF) has been employed for measuring K-shell absorption jump factors and jump ratios for Ti, Cr, Fe, Co, Ni and Cu elements. The jump factors and jump ratios for these elements were determined by measuring K shell fluorescence parameters such as the Kα X-ray production cross-sections, K shell fluorescence yields, Kβ-to-Kα X-rays intensity ratios, total atomic absorption cross sections and mass attenuation coefficients. The measurements were performed using a Cd-109 radioactive point source and an Si(Li) detector in direct excitation and transmission experimental geometry. The measured values for jump factors and jump ratios were compared with theoretically calculated and the ones available in the literature. Copyright © 2014 Elsevier Ltd. All rights reserved.

  14. Optical characterization of magnesium incorporation in p-GaN layers for core–shell nanorod light-emitting diodes

    Science.gov (United States)

    Gîrgel, I.; Šatka, A.; Priesol, J.; Coulon, P.-M.; Le Boulbar, E. D.; Batten, T.; Allsopp, D. W. E.; Shields, P. A.

    2018-04-01

    III-nitride nanostructures are of interest for a new generation of light-emitting diodes (LEDs). However, the characterization of doping incorporation in nanorod (NR) structures, which is essential for creating the p-n junction diodes, is extremely challenging. This is because the established electrical measurement techniques (such as capacitance–voltage or Hall-effect methods) require a simple sample geometry and reliable ohmic contacts, both of which are difficult to achieve in nanoscale devices. The need for homogenous, conformal n-type or p-type layers in core–shell nanostructures magnifies these challenges. Consequently, we demonstrate how a combination of non-contact methods (micro-photoluminescence, micro-Raman and cathodoluminescence), as well as electron-beam-induced-current, can be used to analyze the uniformity of magnesium incorporation in core–shell NRs and make a first estimate of doping levels by the evolution of band transitions, strain and current mapping. These techniques have been used to optimize the growth of core–shell nanostructures for electrical carrier injection, a significant milestone for their use in LEDs.

  15. Giant resonances in free atoms and in clusters

    International Nuclear Information System (INIS)

    Brechignac, C.; Connerade, J.P.

    1994-01-01

    A review of recent developments in the study of giant resonances in free atoms and in clusters is presented, with particular emphasis on the transition from free atoms to atoms in the condensed phase. Giant resonances in alkali and related metallic clusters due to the excitation of closed shells of delocalized electrons are also reviewed and the relation between different types of collective oscillations is discussed. (author)

  16. Dopant distributions in n-MOSFET structure observed by atom probe tomography

    International Nuclear Information System (INIS)

    Inoue, K.; Yano, F.; Nishida, A.; Takamizawa, H.; Tsunomura, T.; Nagai, Y.; Hasegawa, M.

    2009-01-01

    The dopant distributions in an n-type metal-oxide-semiconductor field effect transistor (MOSFET) structure were analyzed by atom probe tomography. The dopant distributions of As, P, and B atoms in a MOSFET structure (gate, gate oxide, channel, source/drain extension, and halo) were obtained. P atoms were segregated at the interface between the poly-Si gate and the gate oxide, and on the grain boundaries of the poly-Si gate, which had an elongated grain structure along the gate height direction. The concentration of B atoms was enriched near the edge of the source/drain extension where the As atoms were implanted.

  17. Dopant distributions in n-MOSFET structure observed by atom probe tomography.

    Science.gov (United States)

    Inoue, K; Yano, F; Nishida, A; Takamizawa, H; Tsunomura, T; Nagai, Y; Hasegawa, M

    2009-11-01

    The dopant distributions in an n-type metal-oxide-semiconductor field effect transistor (MOSFET) structure were analyzed by atom probe tomography. The dopant distributions of As, P, and B atoms in a MOSFET structure (gate, gate oxide, channel, source/drain extension, and halo) were obtained. P atoms were segregated at the interface between the poly-Si gate and the gate oxide, and on the grain boundaries of the poly-Si gate, which had an elongated grain structure along the gate height direction. The concentration of B atoms was enriched near the edge of the source/drain extension where the As atoms were implanted.

  18. Contribution of inner shell Compton ionization to the X-ray fluorescence line intensity

    Science.gov (United States)

    Fernández, Jorge E.; Scot, Viviana; Di Giulio, Eugenio

    2016-10-01

    The Compton effect is a potential ionization mechanism of atoms. It produces vacancies in inner shells that are filled with the same mechanism of atomic relaxation as the one following photo-absorption. This contribution to X-ray fluorescence emission is frequently neglected because the total Compton cross-section is apparently much lower than the photoelectric one at useful X-ray energies. However, a more careful analysis suggests that is necessary to consider single shell cross sections (instead of total cross sections) as a function of energy. In this article these Compton cross sections are computed for the shells K, L1-L3 and M1-M5 in the framework of the impulse approximation. By comparing the Compton and the photoelectric cross-section for each shell it is then possible to determine the extent of the Compton correction to the intensity of the corresponding characteristic lines. It is shown that for the K shell the correction becomes relevant for excitation energies which are too high to be influent in X-ray spectrometry. In contrast, for L and M shells the Compton contribution is relevant for medium-Z elements and medium energies. To illustrate the different grades of relevance of the correction, for each ionized shell, the energies for which the Compton contribution reaches the extent levels of 1, 5, 10, 20, 50 and 100% of the photoelectric one are determined for all the elements with Z = 11-92. For practical applications it is provided a simple formula and fitting coefficients to compute average correction levels for the shells considered.

  19. Atomic hydrogen in the Orion star-forming region

    International Nuclear Information System (INIS)

    Chromey, F.R.; Elmegreen, B.G.; Elmegreen, D.M.

    1989-01-01

    A large-scale survey of atomic hydrogen in Orion reveals low-density material with a total mass comparable to that in dense molecular clouds. The atomic gas is sufficiently dense that it can shield the molecular material from photodissociative radiation and provide a pressure link to the low-density intercloud medium. An excess of H I emission comes from photodissociation fronts near the bright stars and from a giant shell in the Orion Belt region. This shell may have caused the apparent bifurcation between the Orion A and B clouds, and the associated pressures may have induced peculiar motions and star formation in NGC 2023 and 2024. 49 refs

  20. Double-shell target fabrication workshop-2016 report

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Y. Morris [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Oertel, John [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Farrell, Michael [General Atomics, San Diego, CA (United States); Baumann, Ted [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Huang, Haibo [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Nikroo, Abbas [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2017-01-10

    On June 30, 2016, over 40 representatives from Lawrence Livermore National Laboratory (LLNL), Los Alamos National Laboratory (LANL), General Atomics (GA), Laboratory for Laser Energetics (LLE), Schafer Corporation, and NNSA headquarter attended a double-shell (DS) target fabrication workshop at Livermore, California. Pushered-single-shell (PSS) and DS metalgas platforms potentially have a large impact on programmatic applications. The goal of this focused workshop is to bring together target fabrication scientists, physicists, and designers to brainstorm future PSS and DS target fabrication needs and strategies. This one-day workshop intends to give an overall view of historical information, recent approaches, and future research activities at each participating organization. Five topical areas have been discussed that are vital to the success of future DS target fabrications, including inner metal shells, foam spheres, outer ablators, fill tube assembly, and metrology.

  1. Defect-Induced Nucleation and Epitaxy: A New Strategy toward the Rational Synthesis of WZ-GaN/3C-SiC Core-Shell Heterostructures.

    Science.gov (United States)

    Liu, Baodan; Yang, Bing; Yuan, Fang; Liu, Qingyun; Shi, Dan; Jiang, Chunhai; Zhang, Jinsong; Staedler, Thorsten; Jiang, Xin

    2015-12-09

    In this work, we demonstrate a new strategy to create WZ-GaN/3C-SiC heterostructure nanowires, which feature controllable morphologies. The latter is realized by exploiting the stacking faults in 3C-SiC as preferential nucleation sites for the growth of WZ-GaN. Initially, cubic SiC nanowires with an average diameter of ∼100 nm, which display periodic stacking fault sections, are synthesized in a chemical vapor deposition (CVD) process to serve as the core of the heterostructure. Subsequently, hexagonal wurtzite-type GaN shells with different shapes are grown on the surface of 3C-SiC wire core. In this context, it is possible to obtain two types of WZ-GaN/3C-SiC heterostructure nanowires by means of carefully controlling the corresponding CVD reactions. Here, the stacking faults, initially formed in 3C-SiC nanowires, play a key role in guiding the epitaxial growth of WZ-GaN as they represent surface areas of the 3C-SiC nanowires that feature a higher surface energy. A dedicated structural analysis of the interfacial region by means of high-resolution transmission electron microscopy (HRTEM) revealed that the disordering of the atom arrangements in the SiC defect area promotes a lattice-matching with respect to the WZ-GaN phase, which results in a preferential nucleation. All WZ-GaN crystal domains exhibit an epitaxial growth on 3C-SiC featuring a crystallographic relationship of [12̅10](WZ-GaN) //[011̅](3C-SiC), (0001)(WZ-GaN)//(111)(3C-SiC), and d(WZ-GaN(0001)) ≈ 2d(3C-SiC(111)). The approach to utilize structural defects of a nanowire core to induce a preferential nucleation of foreign shells generally opens up a number of opportunities for the epitaxial growth of a wide range of semiconductor nanostructures which are otherwise impossible to acquire. Consequently, this concept possesses tremendous potential for the applications of semiconductor heterostructures in various fields such as optics, electrics, electronics, and photocatalysis for energy harvesting

  2. Energetics of a Li Atom adsorbed on B/N doped graphene with monovacancy

    International Nuclear Information System (INIS)

    Rani, Babita; Jindal, V.K.; Dharamvir, Keya

    2016-01-01

    We use density functional theory (DFT) to study the adsorption properties and diffusion of Li atom across B/N-pyridinic graphene. Regardless of the dopant type, B atoms of B-pyridinic graphene lose electron density. On the other hand, N atoms (p-type dopants) have tendency to gain electron density in N-pyridinic graphene. Higher chemical reactivity and electronic conductivity of B/N-pyridinic graphene are responsible for stronger binding of Li with the substrates as compared to pristine graphene. The binding energy of Li with B/N-pyridinic graphene exceeds the cohesive energy of bulk Li, making it energetically unfavourable for Li to form clusters on these substrates. Li atom gets better adsorbed on N-pyridinic graphene due to an additional p-p hybridization of the orbitals while Li on B-pyridinic prefers the ionic bonding. Also, significant distortion of N-pyridinic graphene upon Li adsorption is a consequence of the change in bonding mechanism between Li atom and the substrate. Our results show that bonding character and hence binding energies between Li and graphene can be tuned with the help of B/N doping of monovacancy defects. Further, the sites for most stable adsorption are different for the two types of doped and defective graphene, leading to greater Li uptake capacity of B-pyridinic graphene near the defect. In addition, B-pyridinic graphene offering lower diffusion barrier, ensures better Li kinetics. Thus, B-pyridinic graphene presents itself as a better anode material for LIBs as compared to N-pyridinic graphene. - Graphical abstract: Adsorption and diffusion of Li atom across the B/N doped monovacancy graphene is studied using ab-initio DFT calculations. Our results show that bonding mechanism and binding of Li with graphene can be tuned with the help of N/B doping of defects. Also, B-pyridinic graphene presents itself as a better anode material for lithium ion batteries as compared to N-pyridinic graphene. Display Omitted - Highlights: • Density

  3. Energetics of a Li Atom adsorbed on B/N doped graphene with monovacancy

    Energy Technology Data Exchange (ETDEWEB)

    Rani, Babita, E-mail: babitabaghla15@gmail.com [Department of Physics, Panjab University, Chandigarh 160014 (India); Department of Physics, Punjabi University, Patiala 147002 (India); Jindal, V.K. [Department of Physics, Panjab University, Chandigarh 160014 (India); Dharamvir, Keya, E-mail: keya@pu.ac.in [Department of Physics, Panjab University, Chandigarh 160014 (India)

    2016-08-15

    We use density functional theory (DFT) to study the adsorption properties and diffusion of Li atom across B/N-pyridinic graphene. Regardless of the dopant type, B atoms of B-pyridinic graphene lose electron density. On the other hand, N atoms (p-type dopants) have tendency to gain electron density in N-pyridinic graphene. Higher chemical reactivity and electronic conductivity of B/N-pyridinic graphene are responsible for stronger binding of Li with the substrates as compared to pristine graphene. The binding energy of Li with B/N-pyridinic graphene exceeds the cohesive energy of bulk Li, making it energetically unfavourable for Li to form clusters on these substrates. Li atom gets better adsorbed on N-pyridinic graphene due to an additional p-p hybridization of the orbitals while Li on B-pyridinic prefers the ionic bonding. Also, significant distortion of N-pyridinic graphene upon Li adsorption is a consequence of the change in bonding mechanism between Li atom and the substrate. Our results show that bonding character and hence binding energies between Li and graphene can be tuned with the help of B/N doping of monovacancy defects. Further, the sites for most stable adsorption are different for the two types of doped and defective graphene, leading to greater Li uptake capacity of B-pyridinic graphene near the defect. In addition, B-pyridinic graphene offering lower diffusion barrier, ensures better Li kinetics. Thus, B-pyridinic graphene presents itself as a better anode material for LIBs as compared to N-pyridinic graphene. - Graphical abstract: Adsorption and diffusion of Li atom across the B/N doped monovacancy graphene is studied using ab-initio DFT calculations. Our results show that bonding mechanism and binding of Li with graphene can be tuned with the help of N/B doping of defects. Also, B-pyridinic graphene presents itself as a better anode material for lithium ion batteries as compared to N-pyridinic graphene. Display Omitted - Highlights: • Density

  4. Structural, electronic, and magnetic properties of Y(n)O (n=2-14) clusters: Density functional study.

    Science.gov (United States)

    Yang, Zhi; Xiong, Shi-Jie

    2008-09-28

    The geometries stability, electronic properties, and magnetism of Y(n)O clusters up to n=14 are systematically studied with density functional theory. In the lowest-energy structures of Y(n)O clusters, the equilibrium site of the oxygen atom gradually moves from an outer site of the cluster, via a surface site, and finally, to an interior site as the number of the Y atoms increases from 2 to 14. Starting from n=12, the O atom falls into the center of the cluster with the Y atoms forming the outer frame. The results show that clusters with n=2, 4, 8, and 12 are more stable than their respective neighbors, and that the total magnetic moments of Y(n)O clusters are all quite small except Y(12)O cluster. The lowest-energy structure of Y(12)O cluster is a perfect icosahedron with a large magnetic moment 6mu(B). In addition, we find that the total magnetic moments are quenched for n=2, 6, and 8 due to the closed-shell electronic configuration. The calculated ionization potentials and electron affinities are in good agreement with the experimental results, which imply that the present theoretical treatments are satisfactory.

  5. Atomic Structure of Au−Pd Bimetallic Alloyed Nanoparticles

    KAUST Repository

    Ding, Yong

    2010-09-08

    Using a two-step seed-mediated growth method, we synthesized bimetallic nanoparticles (NPs) having a gold octahedron core and a palladium epitaxial shell with controlled Pd-shell thickness. The mismatch-release mechanism between the Au core and Pd shell of the NPs was systematically investigated by high-resolution transmission electron microscopy. In the NPs coated with a single atomic layer of Pd, the strain between the surface Pd layer and the Au core is released by Shockley partial dislocations (SPDs) accompanied by the formation of stacking faults. For NPs coated with more Pd (>2 nm), the stacking faults still exist, but no SPDs are found. This may be due to the diffusion of Au atoms into the Pd shell layers to eliminate the SPDs. At the same time, a long-range ordered L11 AuPd alloy phase has been identified in the interface area, supporting the assumption of the diffusion of Au into Pd to release the interface mismatch. With increasing numbers of Pd shell layers, the shape of the Au-Pd NP changes, step by step, from truncated-octahedral to cubic. After the bimetallic NPs were annealed at 523 K for 10 min, the SPDs at the surface of the NPs coated with a single atomic layer of Pd disappeared due to diffusion of the Au atoms into the surface layer, while the stacking faults and the L11 Au-Pd alloyed structure remained. When the annealing temperature was increased to 800 K, electron diffraction patterns and diffraction contrast images revealed that the NPs became a uniform Au-Pd alloy, and most of the stacking faults disappeared as a result of the annealing. Even so, some clues still support the existence of the L11 phase, which suggests that the L11 phase is a stable, long-range ordered structure in Au-Pd bimetallic NPs. © 2010 American Chemical Society.

  6. Reliably counting atomic planes of few-layer graphene (n > 4).

    Science.gov (United States)

    Koh, Yee Kan; Bae, Myung-Ho; Cahill, David G; Pop, Eric

    2011-01-25

    We demonstrate a reliable technique for counting atomic planes (n) of few-layer graphene (FLG) on SiO(2)/Si substrates by Raman spectroscopy. Our approach is based on measuring the ratio of the integrated intensity of the G graphene peak and the optical phonon peak of Si, I(G)/I(Si), and is particularly useful in the range n > 4 where few methods exist. We compare our results with atomic force microscopy (AFM) measurements and Fresnel equation calculations. Then, we apply our method to unambiguously identify n of FLG devices on SiO(2) and find that the mobility (μ ≈ 2000 cm(2) V(-1) s(-1)) is independent of layer thickness for n > 4. Our findings suggest that electrical transport in gated FLG devices is dominated by carriers near the FLG/SiO(2) interface and is thus limited by the environment, even for n > 4.

  7. Atomic radii for atoms with the 6s shell outermost: The effective atomic radius and the van der Waals radius from {sub 55}Cs to {sub 80}Hg

    Energy Technology Data Exchange (ETDEWEB)

    Tatewaki, Hiroshi, E-mail: htatewak@nsc.nagoya-cu.ac.jp [Graduate School of Natural Sciences, Nagoya City University, Nagoya, Aichi 467-8501 (Japan); Institute of Advanced Studies in Artificial Intelligence, Chukyo University, Toyota, Aichi 470-0393 (Japan); Hatano, Yasuyo [School of Information Science and Technology, Chukyo University, Toyota, Aichi 470-0393 (Japan); Noro, Takeshi [Division of Chemistry, Graduate School of Science, Hokkaido University, Sapporo, Hokkaido 060-0810 (Japan); Yamamoto, Shigeyoshi [School of International Liberal Studies, Chukyo University, Nagoya, Aichi 466-8666 (Japan)

    2015-06-15

    We consider, for atoms from {sub 55}Cs to {sub 80}Hg, the effective atomic radius (r{sub ear}), which is defined as the distance from the nucleus at which the magnitude of the electric field is equal to that in He at one half of the equilibrium bond length of He{sub 2}. The values of r{sub ear} are about 50% larger than the mean radius of the outermost occupied orbital of 6s, . The value of r{sub ear} decreases from {sub 55}Cs to {sub 56}Ba and undergoes increases and decreases with rising nuclear charge from {sub 57}La to {sub 70}Y b. In fact r{sub ear} is understood as comprising two interlaced sequences; one consists of {sub 57}La, {sub 58}Ce, and {sub 64}Gd, which have electronic configuration (4f{sup n−1})(5d{sup 1})(6s{sup 2}), and the remaining atoms have configuration (4f{sup n})(6s{sup 2}). The sphere defined by r{sub ear} contains 85%–90% of the 6s electrons. From {sub 71}Lu to {sub 80}Hg the radius r{sub ear} also involves two sequences, corresponding to the two configurations 5d{sup n+1}6s{sup 1} and 5d{sup n}6s{sup 2}. The radius r{sub ear} according to the present methodology is considerably larger than r{sub vdW} obtained by other investigators, some of who have found values of r{sub vdW} close to .

  8. FORMULA ESTABLISHMENT OF COLORLESS Pb(II COMPLEX WITH N-BENZOYL-N-PHENYL HYDROXYLAMINE (BPA USING ATOMIC ABSORPTION SPECTROSCOPY

    Directory of Open Access Journals (Sweden)

    Dhananjay B Sarode

    2012-02-01

    Full Text Available A new method for determination of stoichiometry of colorless complexes by using atomic absorption spectrophotometric technique in continuous variation method and slope ratio method was described here. This method can be used in same manner as that of mole ratio method and slope ratio method. In this method atomic absorption spectroscopy was used instead of UV-Vis spectrophotometry. Atomic absorption spectrophotometric technique is superior to UV-Vis spectrophotometry as it can be applied to colorless soluble complexes. Pb(II and n-benzoyl-n-phenyl hydroxylamine react to form colorless complex at pH 6.5, which can be easily determined by this method. It was found that Pb(II forms 1:2 complex with n-benzoyl-n-phenyl hydroxylamine and is quantitatively extracted back to aqueous solution for AAS analysis.

  9. Interplay of electronic and geometry shell effects in properties of neutral and charged Sr clusters

    DEFF Research Database (Denmark)

    Lyalin, Andrey; Solov'yov, Ilia; Solov'yov, Andrey V.

    2007-01-01

    that the size evolution of structural and electronic properties of strontium clusters is governed by an interplay of the electronic and geometry shell closures. Influence of the electronic shell effects on structural rearrangements can lead to violation of the icosahedral growth motif of strontium clusters......The optimized structure and electronic properties of neutral, singly, and doubly charged strontium clusters have been investigated using ab initio theoretical methods based on density-functional theory. We have systematically calculated the optimized geometries of neutral, singly, and doubly...... charged strontium clusters consisting of up to 14 atoms, average bonding distances, electronic shell closures, binding energies per atom, the gap between the highest occupied and the lowest unoccupied molecular orbitals, and spectra of the density of electronic states (DOS). It is demonstrated...

  10. High spin structure of nuclei near N = 50 shell gap and search for high-spin isomers using time stamped data

    International Nuclear Information System (INIS)

    Saha, S.; Palit, R.; Trivedi, T.; Sethi, J.; Joshi, P.K.; Naidu, B.S.; Donthi, R.; Jadhav, S.; Nanal, V.; Pillay, R.G.; Jain, H.C.; Kumar, S.; Biswas, D.C.; Mukherjee, G.; Saha, S.

    2011-01-01

    Information on the high-spin states of nuclei promises to provide stringent test of the interaction of the Hamiltonian used in the calculation due to smaller basis space for high J-values. It is reported in a recent shell model review that no interaction is optimized for the region of interest around N = 50 and Z = 40 shell closure. The detailed spectroscopic information of the medium and high spin states in these nuclei is required to understand the shape transition between spherical and deformed shapes at N =60 as the higher orbitals are filled. Structure of isomers near shell closure carries important information of, for example, the extent of core excitation. In the present work, the spectroscopic study of the high spin states of 89 Zr isotope have been discussed

  11. Is there chirality in atomic nuclei?

    International Nuclear Information System (INIS)

    Meng Jie

    2009-01-01

    Static chiral symmetries are common in nature, for example, the macroscopic spirals of snail shells, the microscopic handedness of certain molecules, and human hands. The concept of chirality in atomic nuclei was first proposed in 1997, and since then many efforts have been made to understand chiral symmetry and its spontaneous breaking in atomic nuclei. Recent theoretical and experimental progress in the verification of chirality in atomic nuclei will be reviewed, together with a discussion of the problems that await to be solved in the future. (authors)

  12. Decay of the double--K-shell-vacancy state in silver atoms created in the decay of 109Cd

    International Nuclear Information System (INIS)

    Horvat, V.; Ilakovac, K.

    1985-01-01

    A pair of germanium detectors and a three-parameter analyzer were applied in an experimental study of the creation and of the decay of atomic states with a double K-shell vacancy, created in the decay of 109 Cd. Assuming a variable intensity ratio of the Kα 1 and Kα 2 hypersatellite lines, their shift with respect to the diagram lines, Δ/sub K/α/sup h/ = 546 +- 20 eV, and the shift of the Kα satellite lines with an initial L-shell vacancy, Δ/sub K/α/sup s/(L -1 ) = 54 +- 6 eV, were obtained. The former result is in agreement with the previous experimental result of van Eijk et al. and with the theoretical result of Chen et al., but the latter result is significantly lower than the theoretical value of 73 eV. For the I(Kα 1 /sup h/)/I(Kα/sup h/) intensity ratio, a value of 0.54 +- 0.11 was obtained. From the numbers of counts in the hypersatellite-satellite peaks the intensity ratios of the hypersatellite lines I(Kβ/sub 1prime/ /sup h/)/I(Kα/sup h/) = 0.195 +- 0.016, and I(Kβ/sub 2prime/ /sup h/)/I(Kα/sup h/) = 0.055 +- 0.008 were obtained. The former value seems to be larger than the theoretical value 0.168, while the latter value is significantly larger than the theoretical value 0.029

  13. Analytical transition-matrix treatment of electric multipole polarizabilities of hydrogen-like atoms

    International Nuclear Information System (INIS)

    Kharchenko, V.F.

    2015-01-01

    The direct transition-matrix approach to the description of the electric polarization of the quantum bound system of particles is used to determine the electric multipole polarizabilities of the hydrogen-like atoms. It is shown that in the case of the bound system formed by the Coulomb interaction the corresponding inhomogeneous integral equation determining an off-shell scattering function, which consistently describes virtual multiple scattering, can be solved exactly analytically for all electric multipole polarizabilities. Our method allows to reproduce the known Dalgarno–Lewis formula for electric multipole polarizabilities of the hydrogen atom in the ground state and can also be applied to determine the polarizability of the atom in excited bound states. - Highlights: • A new description for electric polarization of hydrogen-like atoms. • Expression for multipole polarizabilities in terms of off-shell scattering functions. • Derivation of integral equation determining the off-shell scattering function. • Rigorous analytic solving the integral equations both for ground and excited states. • Study of contributions of virtual multiple scattering to electric polarizabilities

  14. Activated carbons prepared from hazelnut shells, walnut shells and peanut shells for high CO2 adsorption

    Directory of Open Access Journals (Sweden)

    Lewicka Katarzyna

    2017-06-01

    Full Text Available Research treats about producing activated carbons for CO2 capture from hazelnut shells (HN, walnut shells (WN and peanut shells (PN. Saturated solution of KOH was used as an activating agent in ratio 1:1. Samples were carbonized in the furnace in the range of temperatures 600°C–900°C. Properties of carbons were tested by N2 adsorption method, using BET equation, DFT method and volumetric CO2 adsorption method. With the increase of carbonization temperature specific surface area of studied samples increased. The largest surface area was calculated for samples carbonized at 900°C and the highest values of CO2 adsorption had samples: PN900 at 0°C (5.5 mmol/g and WN900 at 25°C (4.34 mmol/g. All of the samples had a well-developed microporous structure.

  15. Three-fluid MHD-model of a current shell in Z-pinch

    International Nuclear Information System (INIS)

    Bazdenkov, S.V.; Vikhrev, V.V.

    1975-01-01

    Formation and motion of the current shell in a power pulsed discharge (Z-pinch) are discussed. One-dimmensional nonstationary problem about a discharge in deuterium is solved in the three-liquid magnetohydrodynamic approximation with regard for gas ionization and motion of neutral atoms. It is shown that after the shell removal there remains a large quantity of an ionized gas near an isolating chamber wall. The quantity is sufficient that a secondary breakdown may take place in the ionized gas. The moving current shell has a double structure, i.e. a current ''piston'' and a current layer in the shock wave front

  16. Coulomb interaction in atomic and nuclear physics: Inner-Shell excitation, Coulomb dissociation of nuclei, and nuclear polarizability in electronic atoms

    International Nuclear Information System (INIS)

    Hoffmann, B.

    1984-07-01

    In three chapters different physical situations are described which have commonly the Coulomb interaction as driving force. The first two chapters study the Coulomb interactions in connection with the excitation of inner electron shells and the Coulomb excitation of nuclei in first order. In the third part on effect ofthe Coulomb interaction between electronic shell and nucleus is treated in second order (nuclear polarization), and its effect on the isotopic and isomeric shift is studied. (orig./HSI) [de

  17. Study of the effect of shell stabilization of the collective isovector valence-shell excitations along the N=80 isotonic chain

    CERN Multimedia

    Blazhev, A A; Kruecken, R; Coquard, L; Bloch, T P; Wadsworth, R; Danchev, M T; Jenkins, D G; Kroell, T; Leske, J

    It is proposed to initiate an experimental program to study the quadrupole-collective isovector valence-shell excitations the so-called mixed-symmetry states (MSSs) of unstable nuclei from the N = 80 isotonic chain. The main aim of this program is to investigate the microscopic mechanism which leads to a concentration or a fragmentation of the MSSs, an effect dubbed $\\textit{shell stabilization}$ of MSSs. This will be achieved by identification of MSSs of the unstable nuclei $^{140}$Nd and $^{142}$Sm. The MSSs of these nuclei will be identified experimentally by measuring their relative populations with respect to the population of the first 2$^{+}$ states in inverse kinematics Coulomb excitation (CE) reactions on light targets. As a first step of this program we apply for a beam time for the radioactive $^{140}$Nd and $^{142}$Sm beams at beam energy of 2.85 MeV/u. These beams will be used to determine the absolute B(E2;2$_{1}^{+} \\rightarrow$ 0$_{1}^{+}$) values for $^{140}$Nd and $^{142}$Sm in Coulomb excit...

  18. Impact parameter dependence of inner-shell ionization probabilities

    International Nuclear Information System (INIS)

    Cocke, C.L.

    1974-01-01

    The probability for ionization of an inner shell of a target atom by a heavy charged projectile is a sensitive function of the impact parameter characterizing the collision. This probability can be measured experimentally by detecting the x-ray resulting from radiative filling of the inner shell in coincidence with the projectile scattered at a determined angle, and by using the scattering angle to deduce the impact parameter. It is conjectured that the functional dependence of the ionization probability may be a more sensitive probe of the ionization mechanism than is a total cross section measurement. Experimental results for the K-shell ionization of both solid and gas targets by oxygen, carbon and fluorine projectiles in the MeV/amu energy range will be presented, and their use in illuminating the inelastic collision process discussed

  19. Giant atoms for the production of nuclear fuel

    International Nuclear Information System (INIS)

    Fahr, H.J.

    1980-01-01

    Neutral atoms can be blown up to the size of a football, if the electrons of the atomic shell are appropriately excited by photons just below the ionization energy. Such atoms, called Rydberg atoms, behave very differently to the usual ones in multiple respects. The fact that they can very easily be ionized by conventional electrostatic fields is being investigated as a method of isotope separation, for instance in the very important case of U 235 and U 238 . (orig.) [de

  20. Shell Model Far From Stability: Island of Inversion Mergers

    Science.gov (United States)

    Nowacki, F.; Poves, A.

    2018-02-01

    In this study we propose a common mechanism for the disappearance of shell closures far from stabilty. With the use of Large Scale Shell Model calculations (SM-CI), we predict that the region of deformation which comprises the heaviest Chromium and Iron isotopes at and beyond N=40 will merge with a new one at N=50 in an astonishing parallel to the N=20 and N=28 case in the Neon and Magnesium isotopes. We propose a valence space including the full pf-shell for the protons and the full sdg shell for the neutrons, which represents a come-back of the the harmonic oscillator shells in the very neutron rich regime. Our calculations preserve the doubly magic nature of the ground state of 78Ni, which, however, exhibits a well deformed prolate band at low excitation energy, providing a striking example of shape coexistence far from stability. This new Island of Inversion (IoI) adds to the four well documented ones at N=8, 20, 28 and 40.

  1. Production of hollow atoms by high brightness x-ray sources and its applications

    International Nuclear Information System (INIS)

    Moribayashi, Kengo

    2004-01-01

    We study x-ray emissions from the (multi-)inner-shell states and hollow atoms of Si ions excited by high intensity x-ray sources. It is found that the x-ray number from multi-inner-shell excited states (1s 2 2s 2 2p k 3s 2 3p 2 , k=1-4) and hollow atoms (1s 2 2s 2 3p 2 ) is affected greatly by the high intensity short-pulse x-rays and little by weak intensity post-long pulse x-rays. The ratio of the x-ray intensities from hollow atoms to those from the multi-inner-shell excited states becomes almost independent of the pulses and dependent on the intensities of x-ray sources. This ratio may be used for the measurement of intensities of high intensity short pulse x-ray sources. (author)

  2. A distributed atomic physics database and modeling system for plasma spectroscopy

    International Nuclear Information System (INIS)

    Nash, J.K.; Liedahl, D.; Chen, M.H.; Iglesias, C.A.; Lee, R.W.; Salter, J.M.

    1995-08-01

    We are undertaking to develop a set of computational capabilities which will facilitate the access, manipulation, and understanding of atomic data in calculations of x-ray spectral modeling. In this present limited description we will emphasize the objectives for this work, the design philosophy, and aspects of the atomic database, as a more complete description of this work is available. The project is referred to as the Plasma Spectroscopy Initiative; the computing environment is called PSI, or the ''PSI shell'' since the primary interface resembles a UNIX shell window. The working group consists of researchers in the fields of x-ray plasma spectroscopy, atomic physics, plasma diagnostics, line shape theory, astrophysics, and computer science. To date, our focus has been to develop the software foundations, including the atomic physics database, and to apply the existing capabilities to a range of working problems. These problems have been chosen in part to exercise the overall design and implementation of the shell. For successful implementation the final design must have great flexibility since our goal is not simply to satisfy our interests but to vide a tool of general use to the community

  3. A kinetic Monte Carlo study of coarsening resistance of novel core/shell precipitates

    International Nuclear Information System (INIS)

    Zhang, Xuan; Gao, Wenpei; Bellon, Pascal; Averback, Robert S.; Zuo, Jian-Min

    2014-01-01

    A novel approach towards the design of coarsening-resistant nanoprecipitates in structural alloys was investigated by kinetic Monte Carlo (KMC) simulation. The approach is motivated by recent experimental results in Cu–Nb–W alloys showing that room temperature ion irradiation resulted in W nanoprecipitation, leading to exceptional stability of W-rich-core/Nb-rich-shell nanoprecipitates formed following thermal annealing (Zhang et al., 2013 [11]). Here, image simulations of atomically resolved scanning transmission electron microscopy are performed to establish that these W nanoprecipitates are highly ramified. Thermal precipitate coarsening in an A–B–C ternary alloy similar to Cu–Nb–W is then studied by KMC simulations, where the highly immiscible and refractory C solute atoms are initially distributed into fractal nanoprecipitates, or cores, which become coated by a shell of B atoms during elevated temperature annealing. Compared with nanoprecipitates generated by compact C cores, the ramified nanoprecipitates result in exceptionally high trapping efficiency of B solute atoms during thermal coarsening, and the efficiency increases with the cluster size. The KMC results are analyzed and rationalized by noting that, owing to the Gibbs–Thomson effect, when the curvatures of the shell of the precipitates are zero or negative, the microstructure is coarsening-resistant. Such morphology can be realized by facets, or by dynamic balance within positive, negative and zero curvatures

  4. Synchrotron radiation in atomic physics

    International Nuclear Information System (INIS)

    Crasemann, B.

    1998-01-01

    Much of present understanding of atomic and molecular structure and dynamics was gained through studies of photon-atom interactions. In particular, observations of the emission, absorption, and scattering of X rays have complemented particle-collision experiments in elucidating the physics of atomic inner shells. Grounded on Max von Laue's theoretical insight and the invention of the Bragg spectrometer, the field's potential underwent a step function with the development of synchrotron-radiation sources. Notably current third-generation sources have opened new horizons in atomic and molecular physics by producing radiation of wide tunability and exceedingly high intensity and polarization, narrow energy bandwidth, and sharp time structure. In this review, recent advances in synchrotron-radiation studies in atomic and molecular science are outlined. Some tempting opportunities are surveyed that arise for future studies of atomic processes, including many-body effects, aspects of fundamental photon-atom interactions, and relativistic and quantum-electrodynamic phenomena. (author)

  5. Photoelectric atomic absorption cross sections for elements Z = 6 to 54 in the medium energy X-ray range (5 to 25 keV). Pt. 1

    International Nuclear Information System (INIS)

    Hildebrandt, G.; Stephenson, J.D.; Wagenfeld, H.

    1975-01-01

    Photoelectric atomic absorption cross sections have been calculated by means of hydrogen-like eigenfunctions for the atomic K, L, M and N sub-shells of the elements Z = 6 to 54, using revised screening constants and an extension of the theory. The absorption cross sections have been further separated into dipole and quadrupole components so that the numerical data can also be applied to the Borrmann effect. (orig.) [de

  6. First-principles calculations of K-shell X-ray absorption spectra for warm dense nitrogen

    International Nuclear Information System (INIS)

    Li, Zi; Zhang, Shen; Kang, Wei; Wang, Cong; Zhang, Ping

    2016-01-01

    X-ray absorption spectrum is a powerful tool for atomic structure detection on warm dense matter. Here, we perform first-principles molecular dynamics and X-ray absorption spectrum calculations on warm dense nitrogen along a Hugoniot curve. From the molecular dynamics trajectory, the detailed atomic structures are examined for each thermodynamical condition. The K-shell X-ray absorption spectrum is calculated, and its changes with temperature and pressure along the Hugoniot curve are discussed. The warm dense nitrogen systems may contain isolated nitrogen atoms, N 2 molecules, and nitrogen clusters, which show quite different contributions to the total X-ray spectrum due to their different electron density of states. The changes of X-ray spectrum along the Hugoniot curve are caused by the different nitrogen structures induced by the temperature and the pressure. Some clear signatures on X-ray spectrum for different thermodynamical conditions are pointed out, which may provide useful data for future X-ray experiments.

  7. Partial and total electronic stopping cross sections of atoms and solids for protons

    International Nuclear Information System (INIS)

    Kaneko, Toshiaki.

    1990-12-01

    Based on a wave packet theory (Phys. Rev. A40, 2188(1989); Phys. Stat. Sol. (B)156,49(1989)), partial and total electronic cross sections of target elements in atomic and solid phases with atomic number Z ranging from 2 (He) to 92 (U) are tabulated shell by shell for protons with velocity v from 0.2V 0 to 2OV 0 (V 0 =2.18 x 10 8 cm/s). (author)

  8. Relativistic scalar-vector models of the N-N and N-nuclear interactions

    International Nuclear Information System (INIS)

    Green, A.E.S.

    1985-01-01

    This paper for the Proceedings of Conference an Anti-Nucleon and Nucleon-Nucleus Interactions summarizes work by the principal investigator and his collaborators on the nucleon-nucleon (N-N) and nucleon-nuclear (N-eta) interactions. It draws heavily on a paper presented at the Many Body Conference in Rome in 1972 but also includes a brief review of our phenomenological N-eta interaction studies. We first summarize our 48-49 generalized scalar-vector meson field theory model of the N-N interactions. This is followed by a brief description of our phenomenological work in the 50's on the N-eta interaction sponsored by the Atomic Energy Commission (the present DOE). This work finally led to strong velocity dependent potentials with spin orbit and isospin terms for shell and optical model applications. This is followed by a section on the Emergence of One-Boson Exchange Models describing developments in the 60's of quantitative generalized one boson exchange potentials (GOBEP) including our purely relativistic N-N analyses. Then follows a section on the application of this meson field model to the N-eta interaction, in particular to spherical closed shell nuclei. This work was sponsored by AFOSR but funding was halted with the Mansfield amendment. We conclude with a discussion of subsequent collateral work by former colleagues and by others who have converged upon scalar-vector relativistic models of N-N, antiN-N, N-eta and antiN-eta interactions and some lessons learned from this extended endeavor. 61 refs

  9. Lifetime broadening of atomic lines produced upon ultrafast dissociation of HCl and HBr

    Energy Technology Data Exchange (ETDEWEB)

    Lablanquie, P., E-mail: pascal.lablanquie@upmc.fr [Sorbonne Universités, UPMC Univ Paris 06, LCPMR, 11 rue Pierre et Marie Curie, 75231 Paris Cedex 05 (France); CNRS, LCPMR (UMR 7614), 11 rue Pierre et Marie Curie, 75231 Paris Cedex 05 (France); Iwayama, H. [UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585 (Japan); Penent, F. [Sorbonne Universités, UPMC Univ Paris 06, LCPMR, 11 rue Pierre et Marie Curie, 75231 Paris Cedex 05 (France); CNRS, LCPMR (UMR 7614), 11 rue Pierre et Marie Curie, 75231 Paris Cedex 05 (France); Soejima, K. [Department of Environmental Science, Niigata University, Niigata 950-2181 (Japan); Shigemasa, E. [UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585 (Japan)

    2014-08-15

    Highlights: • Ultrafast dissociation of HCl is triggered by 2p{sub 3/2} → σ* excitation. • Ultrafast dissociation of HBr is triggered by 3d{sub 5/2} → σ* excitation. • Photoelectron spectroscopy reveals sharp vibrational molecular lines and broad atomic lines. • The profiles of the atomic lines are analyzed in detail. • We extract the lifetime of the inner shell hole in the neutral atomic fragment. - Abstract: Ultrafast dissociation of the HCl and HBr molecules excited respectively to the 2p{sub 3/2} → σ* and 3d{sub 5/2} → σ* resonances are studied with high resolution photoelectron spectroscopy. Sharp vibrational molecular lines and broad atomic lines are observed. The analysis of the profile of the atomic lines gives access to the lifetimes of the inner shell 2p{sub 3/2} hole in the Cl* (2p{sub 3/2}){sup −1} 3s{sup 2}3p{sup 6} configuration, and the inner shell 3d{sub 5/2} hole in the Br* (3d{sub 5/2}){sup −1} 4s{sup 2}4p{sup 6} configuration.

  10. Rate of saturation of target L-shell vacancy probability, P/sub L/, with projectile charge as given by coupled-channels calculations

    International Nuclear Information System (INIS)

    Becker, R.L.; Ford, A.L.; Reading, J.F.

    1983-01-01

    The distribution of intensities of KL/sup n/ K/sub α/-satellites is nearly binomial, with parameter p/sub L/, the mean L-shell vacancy probability per electron. The chemical environment of an atom produces a shift, δp/sub L/ of p/sub L/ from its value for an isolated target atom. δp/sub L/ tends to increase as p/sub L/ increases, so for greatest chemical sensitivity one wants p/sub L/ as large as possible. p/sub L/ increases with Z/sub p/ but, because it must remain + 9 and even for C + 6

  11. Energy spectra in $p$-shell $\\Lambda$ hypernuclei and $^{19}_{\\Lambda}\\textrm{F}$ and spin-dependent $\\Lambda N$ interactions

    OpenAIRE

    Kanada-En'yo, Yoshiko; Isaka, Masahiro; Motoba, Toshio

    2018-01-01

    Energy spectra of $0s$-orbit $\\Lambda$ states in $p$-shell $\\Lambda$ hypernuclei ($^{A}_\\Lambda Z$) and those in $^{19}_{\\Lambda}\\textrm{F}$ are studied with the microscopic cluster model and antisymmetrized molecular dynamics using the $G$-matrix effective $\\Lambda N$ ($\\Lambda NG$) interactions. Spin-dependent terms of the ESC08a version of the $\\Lambda NG$ interactions are tested and phenomenologically tuned to reproduce observed energy spectra in $p$-shell $^{A}_\\Lambda Z$. Spin-dependent...

  12. Shell model studies in the N = 54 isotones 99Rh, 100Pd

    International Nuclear Information System (INIS)

    Ghugre, S.S.; Sarkar, S.; Chintalapudi, S.N.

    1996-01-01

    The shell model in reproducing the observed level is used to investigate the observed level sequences in 99 Rh and 100 Pd within the spherical shell model framework. Shell model calculations have been performed using the code OXBASH

  13. Fe-N co-doped SiO2@TiO2 yolk-shell hollow nanospheres with enhanced visible light photocatalytic degradation

    Science.gov (United States)

    Wan, Hengcheng; Yao, Weitang; Zhu, Wenkun; Tang, Yi; Ge, Huilin; Shi, Xiaozhong; Duan, Tao

    2018-06-01

    SiO2@TiO2 yolk@shell hollow nanospheres (STNSs) is considered as an outstanding photocatalyst due to its tunable structure and composition. Based on this point, we present an unprecedentedly excellent photocatalytic property of STNSs toward tannic acid via a Fe-N co-doped strategy. Their morphologies, compositions, structure and properties are characterized. The Fe-N co-doped STNSs formed good hollow yolk@shell structure. The results show that the energy gap of the composites can be downgraded to 2.82 eV (pure TiO2 = 3.2 eV). Photocatalytic degradation of tannic acid (TA, 30 mg L-1) under visible light (380 nm TiO2 nanospheres, non-doped STNSs and N-doped STNSs, the Fe-N co-doped STNSs exhibits the highest activity, which can degrade 99.5% TA into CO2 and H2O in 80 min. The probable degradation mechanism of the composites is simultaneously proposed, the band gap of STNSs becomes narrow by co-doping Fe-N, so that the TiO2 shell can stimulate electrons under visible light exposure, generate the ions of radOH and radO2- with a strong oxidizing property. Therefore this approach works is much desired for radioactive organic wastewater photocatalytic degradation.

  14. Electromagnetic transitions in the atom

    International Nuclear Information System (INIS)

    Ulehla, I.; Suk, M.; Trka, Z.

    1990-01-01

    Methods to achieve excitation of atoms are outlined and conditions necessary for the occurrence of electromagnetic transitions in the atomic shell are given. Radiative transitions between the energy states of the atom include stimulated absorption, spontaneous emission, and stimulated emission. Selection rules applying to the majority of observed transitions are given. The parity concept is explained. It is shown how the electromagnetic field and its interaction with the magnetic moment of the atom lead to a disturbance of the energy states of the atom and the occurrence of various electro-optical and magneto-optical phenomena. The Stark effect and electron spin resonance are described. X-rays and X-ray spectra, the Auger effect and the internal photoeffect are also dealt with. The principle of the laser is explained. (M.D.). 22 figs., 1 tab

  15. Establishing an anthropogenic nitrogen baseline using Native American shell middens

    Directory of Open Access Journals (Sweden)

    Autumn eOczkowski

    2016-05-01

    Full Text Available Narragansett Bay, Rhode Island, has been heavily influenced by anthropogenic nutrients for more than 200 years. Recent efforts to improve water quality have cut sewage nitrogen (N loads to this point source estuary by more than half. Given that the bay has been heavily fertilized for longer than monitoring programs have been in place, we sought additional insight into how N dynamics in the system have historically changed. To do this, we measured the N stable isotope (δ15N values in clam shells from as early as 3000 BP to the present. Samples from Native American middens were compared with those collected locally from museums, an archaeological company, and graduate student thesis projects, during a range of time periods. Overall, δ15N values in clam shells from Narragansett Bay have increased significantly over time, reflecting known patterns of anthropogenic nutrient enrichment. Pre-colonization midden shell δ15N values were significantly lower than those post-European contact. While there were no statistical differences among shells dated from the late 15th Century to 2005, there was a significant difference between 2005 and 2015 shells, which we attribute to the higher δ15N values in the effluent associated with recent sewage treatment upgrades. In contrast, the δ15N values of shells from the southern Rhode Island coast remained constant through time; while influenced by human activities, these areas are not directly influenced by point-source sewage discharge. Overall, our results show that this isotope technique for measuring δ15N values in clam shells provides useful insight into how N dynamics in coastal ecosystems have changed during thousands of years, providing managers vital historical information when setting goals for N reduction.

  16. Recent progress in atomic mass formulas and β-decay gross theory

    International Nuclear Information System (INIS)

    Yamada, Masami

    1988-01-01

    The first half of the report focuses on atomic mass formulas which have been developed by the author and his coworkers for accurate representation of the mass of various nuclides at their ground state. The one most frequently used by them is the Uno-Yamada Formula, which consists of two parts representing the gross behavior and the fluctuations due to each nuclide, or so called shell effect. The latter part is the sum of a proton shell term and a neutron shell term, and may be constant or linear depending on the form of the shell terms. Two new formulas have been derived by incorporating the effect of proton-neutron interaction into the above-mentioned constant-type formula. One of them is different from the constant-type Uno-Yamada Formula in that the shell effect part contains a proton-neutron interaction term. Modification is also made to take into account the coulombic energy. The second half of the report addresses the β-decay gross theory. A modified β-decay gross theory is presented, in which improvements are made to reflect the effect of the UV factor and to meet the sum rules related with the Fermi transition. The monoparticle intensity function is also improved by taking into account solutions of many-body problems related with the sum rules. (N.K.)

  17. Atomic Auger spectroscopy: Historical perspective and recent highlights

    International Nuclear Information System (INIS)

    Mehlhorn, W.

    2000-01-01

    The non-radiating decay of an inner-shell ionized atom by the emission of an electron was discovered by Pierre Auger in cloud-chamber experiments in the years 1923 to 1926. The first spectroscopic investigation of Auger electrons was performed by Robinson and Cassie in 1926, marking the birth date of Auger spectroscopy. The following seven decades of Auger spectroscopy will be divided into three periods. In the first period (1926-1960) Auger spectroscopy was mainly connected with β-ray spectroscopy where inner-shell ionization of atoms in the solid state was caused either by γ-conversion or by electron capture. The second period (beginning in 1960) is characterized by the external excitation of gas-phase or free metallic atoms, opening Auger spectroscopy to electron energies in the range of few eV to few keV. The third period (beginning in 1977/78) is characterized by the use of synchrotron radiation with its outstanding properties of tunability, polarization and narrow-band high intensity for the excitation and ionization of inner-shell electrons. Finally, two recent highlights of Auger spectroscopy, the interference between photo- and Auger electron with equal energies and an 'almost' complete experiment for Auger decay, will be presented

  18. Vibrationally resolved photoionization of the 1σg and 1σu shells of N2 molecule

    International Nuclear Information System (INIS)

    Semenov, S K; Cherepkov, N A; Matsumoto, M; Fujiwara, K; Ueda, K; Kukk, E; Tahara, F; Sunami, T; Yoshida, H; Tanaka, T; Nakagawa, K; Kitajima, M; Tanaka, H; De Fanis, A

    2006-01-01

    Theoretical and experimental study of vibrationally resolved partial photoionization cross sections and angular asymmetry parameter β for the 1σ g and 1σ u shells of N 2 molecule in the region of the σ* shape resonance is reported. The measurements were made at the synchrotron radiation facility SPring-8 in Japan. The calculations in the random phase approximation have been performed using the relaxed core Hartree-Fock wavefunctions with the fractional charge of the ion core equal to 0.7. With its help, the role of interchannel coupling between the closely spaced 1σ g and 1σ u shells was studied. The experiment demonstrates the existence of a correlational maximum in the 1σ u shell photoionization cross section induced by the σ* shape resonance in the 1σ g shell. This maximum reveals itself even more clearly in the angular asymmetry parameter β for the v' = 0 and v' = 1 vibrational states of the ion. The calculation in the random phase approximation gives a consistent interpretation of the experimental data

  19. Determination of K shell absorption jump factors and jump ratios in the elements between Tm(Z = 69) and Os(Z = 76) by measuring K shell fluorescence parameters

    International Nuclear Information System (INIS)

    Kaya, N.; Tirasoglu, E.; Apaydin, G.

    2008-01-01

    The K shell absorption jump factors and jump ratios have been measured in the elements between Tm (Z = 69) and Os(Z = 76) without having any mass attenuation coefficient at the upper and lower energy branch of the K absorption edge. The jump factors and jump ratios for these elements have been determined by measuring K shell fluorescence parameters such as the total atomic absorption cross-sections, the K α X-ray production cross-sections, the intensity ratio of the K β and K α X-rays and the K shell fluorescence yields. We have performed the measurements for the calculations of these values in attenuation and direct excitation experimental geometry. The K X-ray photons are excited in the target using 123.6 keV gamma-rays from a strong 57 Co source, and detected with an Ultra-LEGe solid state detector with a resolution 0.15 keV at 5.9 keV. The measured values have been compared with theoretical and others' experimental values. The results have been plotted versus atomic number

  20. Determination of K shell absorption jump factors and jump ratios in the elements between Tm( Z = 69) and Os( Z = 76) by measuring K shell fluorescence parameters

    Science.gov (United States)

    Kaya, N.; Tıraşoğlu, E.; Apaydın, G.

    2008-04-01

    The K shell absorption jump factors and jump ratios have been measured in the elements between Tm ( Z = 69) and Os( Z = 76) without having any mass attenuation coefficient at the upper and lower energy branch of the K absorption edge. The jump factors and jump ratios for these elements have been determined by measuring K shell fluorescence parameters such as the total atomic absorption cross-sections, the K α X-ray production cross-sections, the intensity ratio of the K β and K α X-rays and the K shell fluorescence yields. We have performed the measurements for the calculations of these values in attenuation and direct excitation experimental geometry. The K X-ray photons are excited in the target using 123.6 keV gamma-rays from a strong 57Co source, and detected with an Ultra-LEGe solid state detector with a resolution 0.15 keV at 5.9 keV. The measured values have been compared with theoretical and others' experimental values. The results have been plotted versus atomic number.

  1. Shell biofilm-associated nitrous oxide production in marine molluscs: processes, precursors and relative importance.

    Science.gov (United States)

    Heisterkamp, Ines M; Schramm, Andreas; Larsen, Lone H; Svenningsen, Nanna B; Lavik, Gaute; de Beer, Dirk; Stief, Peter

    2013-07-01

    Emission of the greenhouse gas nitrous oxide (N2 O) from freshwater and terrestrial invertebrates has exclusively been ascribed to N2 O production by ingested denitrifying bacteria in the anoxic gut of the animals. Our study of marine molluscs now shows that also microbial biofilms on shell surfaces are important sites of N2 O production. The shell biofilms of Mytilus edulis, Littorina littorea and Hinia reticulata contributed 18-94% to the total animal-associated N2 O emission. Nitrification and denitrification were equally important sources of N2 O in shell biofilms as revealed by (15) N-stable isotope experiments with dissected shells. Microsensor measurements confirmed that both nitrification and denitrification can occur in shell biofilms due to a heterogeneous oxygen distribution. Accordingly, ammonium, nitrite and nitrate were important drivers of N2 O production in the shell biofilm of the three mollusc species. Ammonium excretion by the animals was found to be sufficient to sustain N2 O production in the shell biofilm. Apparently, the animals provide a nutrient-enriched microenvironment that stimulates growth and N2 O production of the shell biofilm. This animal-induced stimulation was demonstrated in a long-term microcosm experiment with the snail H. reticulata, where shell biofilms exhibited the highest N2 O emission rates when the animal was still living inside the shell. © 2012 John Wiley & Sons Ltd and Society for Applied Microbiology.

  2. Penning-trap mass spectrometry of neutron-rich copper isotopes for probing the Z = 28 and N = 50 shell closures

    CERN Multimedia

    Manea, V

    We propose to perform a Penning-trap mass measurement of $^{79}$Cu. This exotic N = 50 isotone is the last frontier before the doubly-magic $^{78}$Ni and will greatly improve our knowledge of shell evolution. In the same run, we propose $^{77-78}$Cu mass measurements, as well as the search for a possible isomer in $^{76m}$Cu. The data will help to clarify the structure of the odd proton in the Cu isotopes, the influence on the Z = 28 proton core of the νg$_{9/2}$ orbital filling and the impact of the proton-neutron residual interaction on the strength of the N = 50 shell closure.

  3. Electron spin resonance of the solvation of radiation-produced silver atoms in alcohol-water mixtures

    International Nuclear Information System (INIS)

    Li, A.S.W.; Kevan, L.

    1982-01-01

    Frozen solutions of silver salts exposed to 60 Co γ-irradiation form silver atoms by reaction of radiation-produced electrons with the silver ion. At 4 K the silver atoms are initially produced in a nonequilibrium or presolvated state and upon brief thermal excitation to 77 K the first solvation shell geometry changes towards an equilibrium or solvated silver atom. This is most pronounced in water but also occurs in methanol, ethanol and n-propanol matrices. The changes in the electron spin resonance magnetic parameters upon silver atom solvation have been determined. In alcohol-water mixtures Ag 0 is preferentially solvated by polycrystalline water at low alcohol concentration. Above a particular alcohol mole percent Ag 0 suddenly changes its environment to a glassy alcohol one. This sudden change occurs at 17, 13 and 6 mol % methanol, ethanol and n-propanol, respectively. These mole percents correlate with the minimum of the excess enthalpy of mixing and with the hydrogen atom trapping ability of these alcohol-water mixtures. The results also suggest that the local environmental disorder around Ag 0 increases with alcohol chain length in alcohol-water frozen solutions. (author)

  4. Off-shell representations of maximally-extended supersymmetry

    International Nuclear Information System (INIS)

    Cox, P.H.

    1985-01-01

    A general theorem on the necessity of off-shell central charges in representations of maximally-extended supersymmetry (number of spinor charges - 4 x largest spin) is presented. A procedure for building larger and higher-N representations is also explored; a (noninteracting) N=8, maximum spin 2, off-shell representation is achieved. Difficulties in adding interactions for this representation are discussed

  5. Ionization of nS, nP, and nD lithium, potassium, and cesium Rydberg atoms by blackbody radiation

    Science.gov (United States)

    Beterov, I. I.; Ryabtsev, I. I.; Tretyakov, D. B.; Bezuglov, N. N.; Ékers, A.

    2008-07-01

    The results of theoretical calculations of the blackbody ionization rates of lithium, potassium, and cesium atoms residing in Rydberg states are presented. The calculations are performed for nS, nP, and nD states in a wide range of principal quantum numbers, n = 8-65, for blackbody radiation temperatures T = 77, 300, and 600 K. The calculations are performed using the known quasi-classical formulas for the photoionization cross sections and for the radial matrix elements of transitions in the discrete spectrum. The effect of the blackbody-radiation-induced population redistribution between Rydberg states on the blackbody ionization rates measured under laboratory conditions is quantitatively analyzed. Simple analytical formulas that approximate the numerical results and that can be used to estimate the blackbody ionization rates of Rydberg atoms are presented. For the S series of lithium, the rate of population of high-lying Rydberg levels by blackbody radiation is found to anomalously behave as a function of n. This anomaly is similar to the occurrence of the Cooper minimum in the discrete spectrum.

  6. Measurement of K-shell jump ratios and jump factors for some elements in 76≤Z≤92 using EDXRF spectrometer

    International Nuclear Information System (INIS)

    Kaya, N.; Apaydin, G.; Tirasoglu, E.

    2011-01-01

    This article presents experimental values of the K-shell jump factor and jump ratio (ratio of the K-shell photoionization cross section to the photoionization cross section of the rest of the atom at the K edge) for some elements in 76≤Z≤92 using an energy dispersive X-ray fluorescence (EDXRF) spectrometer and compares those values with the theoretical ones giving reasonable agreement. The experimental values have been determined using the fluorescence parameters: K α production cross sections, K β /K α X-rays intensity ratios, total atomic attenuation cross sections, etc. To the best of our knowledge, K-shell jump ratios and jump factors have been measured without having any data on K edge for the first time in these elements. The results have been plotted versus atomic number.

  7. On-line system for investigation of atomic structure

    International Nuclear Information System (INIS)

    Amus'ya, M.Ya.; Chernysheva, L.V.

    1983-01-01

    A description of the on-line ATOM system is presented that enables to investigate the structure of atomic electron shells and their interactions with different scattering particles-electrons, positronse photons, mesons - with the use of computerized numerical solutions. The problem is stated along with mathematical description of atomic properties including theoretical and numerical models for each investigated physical process. The ATOM system structure is considered. The Hartree-Fock method is used to determine the wave functions of the ground and excited atomic states. The programs are written in the ALGOL langauge. Different atomic characteristics were possible to be calculated for the first time with an accuracy exceeding an experimental one

  8. Contemporary models of the atomic nucleus

    CERN Document Server

    Nemirovskii, P E

    2013-01-01

    Contemporary Models of the Atomic Nucleus discusses nuclear structure and properties, expounding contemporary theoretical concepts of the low-energy nuclear processes underlying in nuclear models. This book focuses on subjects such as the optical nuclear model, unified or collective model, and deuteron stripping reaction. Other topics discussed include the basic nuclear properties; shell model; theoretical analysis of the shell model; and radiative transitions and alpha-decay. The deuteron theory and the liquid drop nuclear model with its application to fission theory are also mentioned, but o

  9. Along the N=126 closed shell: study of $^{205}$Au through its $\\pi h_{11/2}^{-1}$ isomeric decay

    CERN Multimedia

    2002-01-01

    Excited states have been identified in only three of the N=126 closed shell nuclei 'below' $^{208}$Pb, $^{207}$Tl, $^{206}$Hg and very recently $^{204}$Pt. We aim to extend our knowledge of the neutron-rich N=126 nuclei by observing the internal decay of the $\\pi h^{-1}_{11/2}$ excited state in $^{205}$Au, which is expected to be isomeric. In addition, the decay of the analogous states in the N=122 and N=124 $^{201,203}$Au will be studied. The lifetimes of the expected isomeric states are crucial for the success of the experiment, and they are estimated to be in the range of 0.3-20 s. These are long enough to enable the extraction from the source, but shorter than the $\\beta$-decay half-lives. Proton single-particle energies and transition rates will be extracted, providing information about the robustness of the N=126 shell-closure. Three days of beam-time is requested.

  10. Electronic shell structure and chemisorption on gold nanoparticles

    DEFF Research Database (Denmark)

    Larsen, Ask Hjorth; Kleis, Jesper; Thygesen, Kristian Sommer

    2011-01-01

    to distort considerably, creating large band gaps at the Fermi level. For up to 200 atoms we consider structures generated with a simple EMT potential and clusters based on cuboctahedra and icosahedra. All types of cluster geometry exhibit jelliumlike electronic shell structure. We calculate adsorption...... energies of several atoms on the cuboctahedral clusters. Adsorption energies are found to vary abruptly at magic numbers. Using a Newns-Anderson model we find that the effect of magic numbers on adsorption energy can be understood from the location of adsorbate-induced states with respect to the cluster...

  11. Modified ferrite core-shell nanoparticles magneto-structural characterization

    Science.gov (United States)

    Klekotka, Urszula; Piotrowska, Beata; Satuła, Dariusz; Kalska-Szostko, Beata

    2018-06-01

    In this study, ferrite nanoparticles with core-shell structures and different chemical compositions of both the core and shell were prepared with success. Proposed nanoparticles have in the first and second series magnetite core, and the shell is composed of a mixture of ferrites with Fe3+, Fe2+ and M ions (where M = Co2+, Mn2+ or Ni2+) with a general composition of M0.5Fe2.5O4. In the third series, the composition is inverted, the core is composed of a mixture of ferrites and as a shell magnetite is placed. Morphology and structural characterization of nanoparticles were done using Transmission Electron Microscopy (TEM), X-ray diffraction (XRD), and Infrared spectroscopy (IR). While room temperature magnetic properties were measured using Mössbauer spectroscopy (MS). It is seen from Mössbauer measurements that Co always increases hyperfine magnetic field on Fe atoms at RT, while Ni and Mn have opposite influences in comparison to pure Fe ferrite, regardless of the nanoparticles structure.

  12. Molecular single photon double K-shell ionization

    International Nuclear Information System (INIS)

    Penent, F.; Nakano, M.; Tashiro, M.; Grozdanov, T.P.; Žitnik, M.; Carniato, S.; Selles, P.; Andric, L.; Lablanquie, P.; Palaudoux, J.; Shigemasa, E.; Iwayama, H.; Hikosaka, Y.; Soejima, K.; Suzuki, I.H.; Kouchi, N.; Ito, K.

    2014-01-01

    We have studied single photon double K-shell ionization of small molecules (N 2 , CO, C 2 H 2n (n = 1–3), …) and the Auger decay of the resulting double core hole (DCH) molecular ions thanks to multi-electron coincidence spectroscopy using a magnetic bottle time-of-flight spectrometer. The relative cross-sections for single-site (K −2 ) and two-site (K −1 K −1 ) double K-shell ionization with respect to single K-shell (K −1 ) ionization have been measured that gives important information on the mechanisms of single photon double ionization. The spectroscopy of two-site (K −1 K −1 ) DCH states in the C 2 H 2n (n = 1–3) series shows important chemical shifts due to a strong dependence on the C-C bond length. In addition, the complete cascade Auger decay following single site (K −2 ) ionization has been obtained

  13. Ionization and excitation of lithium atoms by fast charged particle impact: identification of mechanisms for double K-shell vacancy production as a function of the projectile charge and velocity

    International Nuclear Information System (INIS)

    Rangama, J.

    2002-11-01

    Ionization and excitation of lithium atoms by fast charged particle impact: identification of mechanisms for double K-shell vacancy production as a function of projectile charge and velocity. Auger electron spectroscopy is used for an experimental investigation of ionization and excitation of lithium atoms by ions (Kr34 + and Ar18 + ) and electrons at high impact velocities (from 6 to 60 a.u.). In particular, relative contributions of the mechanisms responsible for lithium K-shell ionization-excitation are determined for various projectile charges Zp and velocities vp. A large range of perturbation parameters |Zp|/vp is explored (|Zp|/vp = 0,05 - 0,7 a.u.). From single K-shell excitation results, it appears that the projectile-electron interaction gives mainly rise to a dipole-like transition 1s -> np Concerning K-shell ionization-excitation, the separation of the TS2 (two independent projectile-electron interactions) and TS1 (one projectile-electron interaction) mechanisms responsible for the formation of the 2snp 1,3P and 2sns 1,3S lithium states is performed. In TS1 process, the projectile-electron interaction can be followed by an electron-electron interaction (dielectronic process) or by an internal rearrangement of the residual target after a sudden potential change (shake process). From Born theory, ab initio calculations are performed. The good agreement between theoretical and experimental results confirms the mechanism identification. For the production of P states, TS1 is found to be strongly dominant for small |Zp|/vp values and TS2 is found to be most important for large |Zp|/vp values. Since P states cannot be formed significantly via a shake process, the TS1 and TS2 separation provides a direct signature of the dielectronic process. On the other hand, the TS1 process is shown to be the unique process for producing the S states. At the moment, only the shake aspect of the TS1 process can explain the fact that the 2s3s configuration is preferentially

  14. Atomic nitrogen encapsulated in fullerenes: realization of a chemical Faraday cage

    International Nuclear Information System (INIS)

    Lips, K.

    2000-01-01

    Fullerenes, C 60 and C 70 , are ideal containers for atomic nitrogen. We will show by electron paramagnetic resonance (EPR) experiments that nitrogen in C 60 keeps its atomic ground state configuration and resides in the center of the cage. This is the first time that atomic nitrogen is stabilized at ambient conditions. The inert shell of the fullerene protects the highly reactive nitrogen from undergoing chemical reactions with the surroundings. The fullerene cage is the chemical analogue of the Faraday cage in case of electrical fields, i.e. it shields off the chemical reactivity. As for the free nitrogen atom, the spins of the three p-electrons of nitrogen in C 60 are parallel (S = 3/2) and the atom has spherical symmetry. Due to the center position of nitrogen in C 60 , extremely sharp EPR lines are observed. This reflects the absence of a strong host-guest interaction and shows that the individuality of nitrogen in the fullerenes is preserved. Further evidence for the almost interaction-free suspension of nitrogen in the fullerene cages is provided by g-factor measurements. These investigations show that magnetic shielding of the host molecules can account for the observed differences between N rate at C 60 and N rate at C 70 . The fullerene cage can be chemically modified without destroying the endohedral complex. The chemical modifications change the symmetry of the molecule which is observed through an additional fine structure in the EPR spectrum. Influences of the modifications on the stability of N rate at C 60 will be discussed. (orig.)

  15. Role of N-methyl-2-pyrrolidone for preparation of Fe{sub 3}O{sub 4}@SiO{sub 2} controlled the shell thickness

    Energy Technology Data Exchange (ETDEWEB)

    Wee, Sung-Bok [Hanyang University, Division of Materials Science and Engineering (Korea, Republic of); Oh, Hyeon-Cheol [Korea Nano Plus, Inc. (Korea, Republic of); Kim, Tae-Gyun; An, Gye-Seok; Choi, Sung-Churl, E-mail: choi0505@hanyang.ac.kr [Hanyang University, Division of Materials Science and Engineering (Korea, Republic of)

    2017-04-15

    We developed a simple and novel approach for the synthesis of Fe{sub 3}O{sub 4}@SiO{sub 2} nanoparticles with controlled shell thickness, and studied the mechanism. The introduction of N-methyl-2-pyrrolidone (NMP) led to trapping of monomer nuclei in single shell and controlled the shell thickness. Fe{sub 3}O{sub 4}@SiO{sub 2} controlled the shell thickness, showing a high magnetization value (64.47 emu/g). Our results reveal the role and change in the chemical structure of NMP during the core-shell synthesis process. NMP decomposed to 4-aminobutanoic acid in alkaline condition and decreased the hydrolysis rate of the silica coating process.

  16. In Situ Generation of Two-Dimensional Au–Pt Core–Shell Nanoparticle Assemblies

    Directory of Open Access Journals (Sweden)

    Khalid Madiha

    2009-01-01

    Full Text Available Abstract Two-dimensional assemblies of Au–Pt bimetallic nanoparticles are generated in situ on polyethyleneimmine (PEI silane functionalized silicon and indium tin oxide (ITO coated glass surfaces. Atomic force microscopy (AFM, UV–Visible spectroscopy, and electrochemical measurements reveal the formation of core–shell structure with Au as core and Pt as shell. The core–shell structure is further supported by comparing with the corresponding data of Au nanoparticle assemblies. Static contact angle measurements with water show an increase in hydrophilic character due to bimetallic nanoparticle generation on different surfaces. It is further observed that these Au–Pt core–shell bimetallic nanoparticle assemblies are catalytically active towards methanol electro-oxidation, which is the key reaction for direct methanol fuel cells (DMFCs.

  17. Novel thermo-sensitive core-shell nanoparticles for targeted paclitaxel delivery

    International Nuclear Information System (INIS)

    Li Yuanpei; Pan Shirong; Zhang Wei; Du Zhuo

    2009-01-01

    Novel thermo-sensitive nanoparticles self-assembled from poly(N,N-diethylacrylamide- co-acrylamide)-block-poly(γ-benzyl L-glutamate) were designed for targeted drug delivery in localized hyperthermia. The lower critical solution temperature (LCST) of nanoparticles was adjusted to a level between physiological body temperature (37 deg. C) and that used in local hyperthermia (about 43 deg. C). The temperature-dependent performances of the core-shell nanoparticles were systemically studied by nuclear magnetic resonance (NMR), circular dichroism (CD), fluorescence spectroscopy, dynamic light scattering (DLS), and atom force microscopy (AFM). The mean diameter of the nanoparticles increased slightly from 110 to 129 nm when paclitaxel (PTX), a poorly water-soluble anti-tumor drug, was encapsulated. A stability study in bovine serum albumin (BSA) solution indicated that the PTX loaded nanoparticles may have a long circulation time under physiological environments as the LCST was above physiological body temperature and the shell remained hydrophilic at 37 deg.C. The PTX release profiles showed thermo-sensitive controlled behavior. The proliferation inhibiting activity of PTX loaded nanoparticles was evaluated against Hela cells in vitro, compared with Taxol (a formulation of paclitaxel dissolved in Cremophor EL and ethanol). The cytotoxicity of PTX loaded nanoparticles increased obviously when hyperthermia was performed. The nanoparticles synthesized here could be an ideal candidate for thermal triggered anti-tumor PTX delivery system.

  18. EVOLUTION OF THE WATER MASER EXPANDING SHELL IN W75N VLA 2

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jeong-Sook; Kim, Sang Joon [School of Space Science, Kyunghee University, Seocheon-dong, Giheung-si, Gyeonggi-do, 446-701 (Korea, Republic of); Kim, Soon-Wook [Korea Astronomy and Space Science Institute, 776 Daedeokdaero, Yuseong, Daejeon 305-348 (Korea, Republic of); Kurayama, Tomoharu [Graduate School of Science and Engineering, Kagoshima University, 1-21-35 Korimoto, Kagoshima, Kagoshima 890-0065 (Japan); Honma, Mareki [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Sasao, Tesuo [Yaeyama Star Club, Ookawa, Ishigaki, Okinawa 904-0022 (Japan); Surcis, Gabriele [Joint Institute for VLBI in Europe, Postbus 2, 7990 AA Dwingeloo (Netherlands); Canto, Jorge [Instituto de Astronomia (UNAM), Apartado 70-264, 04510 Mexico D. F. (Mexico); Torrelles, Jose M., E-mail: evony@kasi.re.kr, E-mail: skim@kasi.re.kr [Instituto de Ciencias del Espacio (CSIC)-UB/IEEC, Universitat de Barcelona, Marti i Franques 1, E-08028 Barcelona (Spain)

    2013-04-10

    We present Very Long Baseline Interferometry (VLBI) observations of 22 GHz H{sub 2}O masers in the high-mass star-forming region of W75N, carried out with VLBI Exploration of Radio Astrometry (VERA) for three epochs in 2007 with an angular resolution of {approx}1 mas. We detected H{sub 2}O maser emission toward the radio jet in VLA 1 and the expanding shell-like structure in VLA 2. The spatial distribution of the H{sub 2}O masers detected with VERA and measured proper motions around VLA 1 and VLA 2 are similar to those found with previous VLBI observations in epochs 1999 and 2005, with the masers in VLA 1 mainly distributed along a linear structure parallel to the radio jet and, on the other hand, forming a shell-like structure around VLA 2. We have made elliptical fits to the VLA 2 H{sub 2}O maser shell-like structure observed in the different epochs (1999, 2005, and 2007), and found that the shell is still expanding eight years after its discovery. From the difference in the size of the semi-major axes of the fitted ellipses in epochs 1999 ({approx_equal}71 {+-} 1 mas), 2005 ({approx_equal}97 {+-} 3 mas), and 2007 ({approx_equal}111 {+-} 1 mas), we estimate an average expanding velocity of {approx}5 mas yr{sup -1}, similar to the proper motions measured in the individual H{sub 2}O maser features. A kinematic age of {approx}20 yr is derived for this structure. In addition, our VERA observations indicate an increase in the ellipticity of the expanding shell around VLA 2 from epochs 1999 to 2007. In fact, the elliptical fit of the VERA data shows a ratio of the minor and major axes of {approx}0.6, in contrast with an almost circular shape for the shell detected in 1999 and 2005 (b/a {approx} 0.9). This suggests that we are probably observing the formation of a jet-driven H{sub 2}O maser structure in VLA2, evolving from a non-collimated pulsed-outflow event during the first stages of evolution of a massive young stellar object (YSO). This may support predictions made

  19. Electron shell contributions to gamma-ray spectra of positron annihilation in noble gases

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Feng; Selvam, Lalitha [Centre for Molecular Simulation, Swinburne University of Technology, PO Box 218, Hawthorn, Victoria 3122 (Australia); Gribakin, Gleb F [Department of Applied Mathematics and Theoretical Physics, Queen' s University Belfast BT7 1NN (United Kingdom); Surko, Clifford M, E-mail: fwang@swin.edu.a [Physics Department, University of California, San Diego, La Jolla, CA 92093-0319 (United States)

    2010-08-28

    Gamma-ray positron annihilation spectra of the noble gases are simulated using computational chemistry tools for the bound electron wavefunctions and plane-wave approximation for the low-energy positron. The present annihilation line shapes, i.e. the full width at half maximum, {Delta}{epsilon}, of the {gamma}-ray annihilation spectra for He and Ar (valence) agree well with available independent atomic calculations using a different algorithm. For other noble gases they achieve moderate agreement with the experimental measurements. It is found that the contributions of various atomic electron shells to the spectra depend significantly on their principal quantum number n and orbital angular momentum quantum number l. The present study further reveals that the outermost ns electrons of the noble gases exhibit spectral line shapes in close agreement with those measured, indicating (as expected) that the measurements are not due to a simple sum over the momentum densities for all atomic electrons. The robust nature of the present approach makes it possible for us to proceed to more complex molecular systems using the tools of modern computational chemistry.

  20. Modeling and Simulation on NOx and N2O Formation in Co-combustion of Low-rank Coal and Palm Kernel Shell

    Directory of Open Access Journals (Sweden)

    Mahidin Mahidin

    2012-12-01

    Full Text Available NOx and N2O emissions from coal combustion are claimed as the major contributors for the acid rain, photochemical smog, green house and ozone depletion problems. Based on the facts, study on those emissions formation is interest topic in the combustion area. In this paper, theoretical study by modeling and simulation on NOx and N2O formation in co-combustion of low-rank coal and palm kernel shell has been done. Combustion model was developed by using the principle of chemical-reaction equilibrium. Simulation on the model in order to evaluate the composition of the flue gas was performed by minimization the Gibbs free energy. The results showed that by introduced of biomass in coal combustion can reduce the NOx concentration in considerably level. Maximum NO level in co-combustion of low-rank coal and palm kernel shell with fuel composition 1:1 is 2,350 ppm, low enough compared to single low-rank coal combustion up to 3,150 ppm. Moreover, N2O is less than 0.25 ppm in all cases. Keywords: low-rank coal, N2O emission, NOx emission, palm kernel shell

  1. Theory of multiphoton ionization of atoms

    International Nuclear Information System (INIS)

    Szoeke, A.

    1986-03-01

    A non-perturbative approach to the theory of multiphoton ionization is reviewed. Adiabatic Floquet theory is its first approximation. It explains qualitatively the energy and angular distribution of photoelectrons. In many-electron atoms it predicts collective and inner shell excitation. 14 refs

  2. Distribution of radiation lifetime and oscillator strengths in atomic and ion spectra

    Energy Technology Data Exchange (ETDEWEB)

    Shabanova, L.N.; Gruzdev, P.F.; Verolajnen, Ya.F. (Leningradskij Gosudarstvennyj Univ. (USSR). Nauchno-Issledovatel' skij Fizicheskij Inst.)

    1984-04-01

    Analysis of present experimental and theoretical data on determination of radiation life time and forces of oscillators for disclosing general regularities inherent in radiation constants inside the atom, homologous atoms inside subgroups of atoms and ions of isoelectronic subsequences is conducted. Another purpose is to chose most reliable values of constants and to obtain extrapolation formulae for their determination on the base of the corresponding statistical processing data and revealed regularities. A hydrogen atom, isoelectronic series NaI-Ni18, isoelectronic series Ne, He, ZnI, CdI are considered. Systematics of radiation life time depending on the basic quantum number is presented. The force of oscillators f is considered on the example of an atomic system with one valent electron outside the locked shell - Li, Na, K, Rb, Cs. Distribution of force density of the oscillator df/dE is considered, here continuous spectrum near the threshold of ionization is regarded simultaneously with discrete spectrum. An interpolation formula for the number f for high members of atom series (n>=10) of alkaline metals is presented. Values of coefficients included in this formula are tabulated.

  3. Atomic layer deposition of GaN at low temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Ozgit, Cagla; Donmez, Inci; Alevli, Mustafa; Biyikli, Necmi [UNAM - Institute of Materials Science and Nanotechnology, Bilkent University, 06800 Ankara (Turkey)

    2012-01-15

    The authors report on the self-limiting growth of GaN thin films at low temperatures. Films were deposited on Si substrates by plasma-enhanced atomic layer deposition using trimethylgallium (TMG) and ammonia (NH{sub 3}) as the group-III and -V precursors, respectively. GaN deposition rate saturated at 185 deg. C for NH{sub 3} doses starting from 90 s. Atomic layer deposition temperature window was observed from 185 to {approx}385 deg. C. Deposition rate, which is constant at {approx}0.51 A/cycle within the temperature range of 250 - 350 deg. C, increased slightly as the temperature decreased to 185 deg. C. In the bulk film, concentrations of Ga, N, and O were constant at {approx}36.6, {approx}43.9, and {approx}19.5 at. %, respectively. C was detected only at the surface and no C impurities were found in the bulk film. High oxygen concentration in films was attributed to the oxygen impurities present in group-V precursor. High-resolution transmission electron microscopy studies revealed a microstructure consisting of small crystallites dispersed in an amorphous matrix.

  4. Highly n -doped graphene generated through intercalated terbium atoms

    Science.gov (United States)

    Daukiya, L.; Nair, M. N.; Hajjar-Garreau, S.; Vonau, F.; Aubel, D.; Bubendorff, J. L.; Cranney, M.; Denys, E.; Florentin, A.; Reiter, G.; Simon, L.

    2018-01-01

    We obtained highly n -type doped graphene by intercalating terbium atoms between graphene and SiC(0001) through appropriate annealing in ultrahigh vacuum. After terbium intercalation angle-resolved-photoelectron spectroscopy (ARPES) showed a drastic change in the band structure around the K points of the Brillouin zone: the well-known conical dispersion band of a graphene monolayer was superposed by a second conical dispersion band of a graphene monolayer with an electron density reaching 1015cm-2 . In addition, we demonstrate that atom intercalation proceeds either below the buffer layer or between the buffer layer and the monolayer graphene. The intercalation of terbium below a pure buffer layer led to the formation of a highly n -doped graphene monolayer decoupled from the SiC substrate, as evidenced by ARPES and x-ray photoelectron spectroscopy measurements. The band structure of this highly n -doped monolayer graphene showed a kink (a deviation from the linear dispersion of the Dirac cone), which has been associated with an electron-phonon coupling constant one order of magnitude larger than those usually obtained for graphene with intercalated alkali metals.

  5. Structure of exotic nuclei by large-scale shell model calculations

    International Nuclear Information System (INIS)

    Utsuno, Yutaka; Otsuka, Takaharu; Mizusaki, Takahiro; Honma, Michio

    2006-01-01

    An extensive large-scale shell-model study is conducted for unstable nuclei around N = 20 and N = 28, aiming to investigate how the shell structure evolves from stable to unstable nuclei and affects the nuclear structure. The structure around N = 20 including the disappearance of the magic number is reproduced systematically, exemplified in the systematics of the electromagnetic moments in the Na isotope chain. As a key ingredient dominating the structure/shell evolution in the exotic nuclei from a general viewpoint, we pay attention to the tensor force. Including a proper strength of the tensor force in the effective interaction, we successfully reproduce the proton shell evolution ranging from N = 20 to 28 without any arbitrary modifications in the interaction and predict the ground state of 42Si to contain a large deformed component

  6. Superradiators created atom by atom

    Science.gov (United States)

    Meschede, Dieter

    2018-02-01

    High radiation rates are usually associated with macroscopic lasers. Laser radiation is “coherent”—its amplitude and phase are well-defined—but its generation requires energy inputs to overcome loss. Excited atoms spontaneously emit in a random and incoherent fashion, and for N such atoms, the emission rate simply increases as N. However, if these atoms are in close proximity and coherently coupled by a radiation field, this microscopic ensemble acts as a single emitter whose emission rate increases as N2 and becomes “superradiant,” to use Dicke's terminology (1). On page 662 of this issue, Kim et al. (2) show the buildup of coherent light fields through collective emission from atomic radiators injected one by one into a resonator field. There is only one atom ever in the cavity, but the emission is still collective and superradiant. These results suggest another route toward thresholdless lasing.

  7. Low-temperature atomic layer epitaxy of AlN ultrathin films by layer-by-layer, in-situ atomic layer annealing.

    Science.gov (United States)

    Shih, Huan-Yu; Lee, Wei-Hao; Kao, Wei-Chung; Chuang, Yung-Chuan; Lin, Ray-Ming; Lin, Hsin-Chih; Shiojiri, Makoto; Chen, Miin-Jang

    2017-01-03

    Low-temperature epitaxial growth of AlN ultrathin films was realized by atomic layer deposition (ALD) together with the layer-by-layer, in-situ atomic layer annealing (ALA), instead of a high growth temperature which is needed in conventional epitaxial growth techniques. By applying the ALA with the Ar plasma treatment in each ALD cycle, the AlN thin film was converted dramatically from the amorphous phase to a single-crystalline epitaxial layer, at a low deposition temperature of 300 °C. The energy transferred from plasma not only provides the crystallization energy but also enhances the migration of adatoms and the removal of ligands, which significantly improve the crystallinity of the epitaxial layer. The X-ray diffraction reveals that the full width at half-maximum of the AlN (0002) rocking curve is only 144 arcsec in the AlN ultrathin epilayer with a thickness of only a few tens of nm. The high-resolution transmission electron microscopy also indicates the high-quality single-crystal hexagonal phase of the AlN epitaxial layer on the sapphire substrate. The result opens a window for further extension of the ALD applications from amorphous thin films to the high-quality low-temperature atomic layer epitaxy, which can be exploited in a variety of fields and applications in the near future.

  8. Excitation of the inner 4d shell of neutral iodine

    Energy Technology Data Exchange (ETDEWEB)

    Pettini, M; Tozzi, G P [Osservatorio Astrofisico di Arcetri, Florence (Italy); Mazzoni, M [Florence Univ. (Italy). Ist. di Astronomia

    1981-03-23

    The absorption spectrum of neutral atomic iodine has been photographed in the EUV region and three strong autoionized resonances have been identified. A broad absorption feature has been observed and is ascribed to a collective exitation of the 4d inner shell.

  9. Formation of the minor phase shell on the surface of hypermonotectic alloy powders

    International Nuclear Information System (INIS)

    Zhao, J.Z.

    2006-01-01

    The microstructure evolution in an atomized hypermonotectic alloy drop is calculated. The results indicate that the formation of the minor phase shell on the surface of the powder is due to the heterogeneous nucleation of the minor phase droplets on the atomized drop surface and the resultant diffusional transfer of solute during the liquid-liquid phase transformation

  10. Charge transfer and excitation in high-energy ion-atom collisions

    International Nuclear Information System (INIS)

    Schlachter, A.S.; Berkner, K.H.; McDonald, R.J.

    1986-11-01

    Coincidence measurements of charge transfer and simultaneous projectile electron excitation provide insight into correlated two-electron processes in energetic ion-atom collisions. Projectile excitation and electron capture can occur simultaneously in a collision of a highly charged ion with a target atom; this process is called resonant transfer and excitation (RTE). The intermediate excited state which is thus formed can subsequently decay by photon emission or by Auger-electron emission. Results are shown for RTE in both the K shell of Ca ions and the L shell of Nb ions, for simultaneous projectile electron loss and excitation, and for the effect of RTE on electron capture

  11. Cross sections for inelastic scattering of electrons by atoms: selected topics related to electron microscopy

    International Nuclear Information System (INIS)

    Inokuti, M.; Manson, S.T.

    1982-01-01

    We begin with a resume of the Bethe theory, which provides a general framework for discussing the inelastic scattering of fast electrons and leads to powerful criteria for judging the reliability of cross-section data. The central notion of the theory is the generalized oscillator strength as a function of both the energy transfer and the momentum transfer, and is the only non-trivial factor in the inelastic-scattering cross section. Although the Bethe theory was initially conceived for free atoms, its basic ideas apply to solids, with suitable generalizations; in this respect, the notion of the dielectric response function is the most fundamental. Topics selected for discussion include the generalized oscillator strengths for the K-shell and L-shell ionization for all atoms with Z less than or equal to 30, evaluated by use of the Hartree-Slater potential. As a function of the energy transfer, the generalized oscillator strength most often shows a non-monotonic structure near the K-shell and L-shell thresholds, which has been interpreted as manifestations of electron-wave propagation through atomic fields. For molecules and solids, there are additional structures due to the scattering of ejected electrons by the fields of other atoms

  12. Outer-shell transitions in collisions between multiply charged ions and atoms

    International Nuclear Information System (INIS)

    Bloemen, E.W.P.

    1980-01-01

    The study of collisions between multiply charged ions and atoms (molecules) is of importance in different areas of research. Usually, the most important process is capture of an electron from the target atom into the projectile ion. In most cases the electron goes to an excited state of the projectile ion. These electron capture processes are studied. The author also studied direct excitation of the target atom and of the projectile ion. (Auth.)

  13. Hohlraum-driven mid-Z (SiO2) double-shell implosions on the omega laser facility and their scaling to NIF.

    Science.gov (United States)

    Robey, H F; Amendt, P A; Milovich, J L; Park, H-S; Hamza, A V; Bono, M J

    2009-10-02

    High-convergence, hohlraum-driven implosions of double-shell capsules using mid-Z (SiO2) inner shells have been performed on the OMEGA laser facility [T. R. Boehly, Opt. Commun. 133, 495 (1997)]. These experiments provide an essential extension of the results of previous low-Z (CH) double-shell implosions [P. A. Amendt, Phys. Rev. Lett. 94, 065004 (2005)] to materials of higher density and atomic number. Analytic modeling, supported by highly resolved 2D numerical simulations, is used to account for the yield degradation due to interfacial atomic mixing. This extended experimental database from OMEGA enables a validation of the mix model, and provides a means for quantitatively assessing the prospects for high-Z double-shell implosions on the National Ignition Facility [Paisner, Laser Focus World 30, 75 (1994)].

  14. Measurement of the indium segregation in InGaN based LEDs with single atom sensitivity

    International Nuclear Information System (INIS)

    Jinschek, Joerg; Kisielowski, Christian; Van Dyck, Dirk; Geuens, Philippe

    2003-01-01

    In light emitting diodes (LED) consisting of GaN/InGaN/GaN quantum wells (QWs), the exact indium distribution inside the wells of the active region affects the performance of devices. Indium segregation can take place forming small InGaN clusters of locally varying composition. In the past, we used a local strain analysis from single HRTEM lattice images to determine the In composition inside the InGaN QWs with a resolution of 0.5 nm x 0.3 nm. Truly atomic resolution can be pursued by exploitation of intensity dependencies on the atomic number (Z) of the electron exit-wave (EW). In microscopes with sufficient sensitivity, local variations of amplitude and phase are found to be discrete with sample thickness, which allows for counting the number of atoms in each individual column of ∼0.08 nm diameter. In QW s of ∼17 percent of average indium concentration it is possible to discriminate between pure Ga columns and columns containing 1, 2, 3, or more In atoms because phase changes are discrete and element specific. The preparation of samples with atomically flat surfaces is a limiting factor for the application of the procedure

  15. Addressing Challenges and Scalability in the Synthesis of Thin Uniform Metal Shells on Large Metal Nanoparticle Cores: Case Study of Ag-Pt Core-Shell Nanocubes.

    Science.gov (United States)

    Aslam, Umar; Linic, Suljo

    2017-12-13

    Bimetallic nanoparticles in which a metal is coated with an ultrathin (∼1 nm) layer of a second metal are often desired for their unique chemical and physical properties. Current synthesis methods for producing such core-shell nanostructures often require incremental addition of a shell metal precursor which is rapidly reduced onto metal cores. A major shortcoming of this approach is that it necessitates precise concentrations of chemical reagents, making it difficult to perform at large scales. To address this issue, we considered an approach whereby the reduction of the shell metal precursor was controlled through in situ chemical modification of the precursor. We used this approach to develop a highly scalable synthesis for coating atomic layers of Pt onto Ag nanocubes. We show that Ag-Pt core-shell nanostructures are synthesized in high yields and that these structures effectively combine the optical properties of the plasmonic Ag nanocube core with the surface properties of the thin Pt shell. Additionally, we demonstrate the scalability of the synthesis by performing a 10 times scale-up.

  16. Photoionization and vacancy decay of endohedral atoms

    International Nuclear Information System (INIS)

    Amusia, M. Ya.

    2007-01-01

    We demonstrate the role played by the fullerenes shell in the photoionization and vacancy decay of endohedral atoms A-C 60 . It is shown, partly in the frame of a rather simple model that describes the fullerene shell, partly using only the assumption on the smallness of the atom A in comparison to the size of C 60 that it affects photoionization and the vacancy decay of A-C 60 profoundly. Namely, it leads to a number of new resonances in photoionization cross-section and other photoionization characteristics as well as strong modifications of the vacancy decay probabilities and to opening of new decay channels. We will discuss the problem of photon propagation through the C 60 shell and conclude that at any considered frequency ω, 0 ≤ ω ≤ 60 eV the C 60 enhances the incoming radiation. This shows non-metallic dielectric behavior of the 240 collectivized electrons in C 60 . We also discuss the effects of C 60 upon the fast electron inelastic scattering. The results obtained are valid qualitatively also for other than C 60 molecules, e.g. for C 70 or C 76

  17. Photoionization and vacancy decay of endohedral atoms

    Energy Technology Data Exchange (ETDEWEB)

    Amusia, M. Ya. [Racah Institute of Physics, Hebrew University, Jerusalem 91904 (Israel); A.F. Ioffe Physical-Technical Institute, St. Petersburg 194021 (Russian Federation)], E-mail: amusia@vms.huji.ac.il

    2007-10-15

    We demonstrate the role played by the fullerenes shell in the photoionization and vacancy decay of endohedral atoms A-C{sub 60}. It is shown, partly in the frame of a rather simple model that describes the fullerene shell, partly using only the assumption on the smallness of the atom A in comparison to the size of C{sub 60} that it affects photoionization and the vacancy decay of A-C{sub 60} profoundly. Namely, it leads to a number of new resonances in photoionization cross-section and other photoionization characteristics as well as strong modifications of the vacancy decay probabilities and to opening of new decay channels. We will discuss the problem of photon propagation through the C{sub 60} shell and conclude that at any considered frequency {omega}, 0 {<=} {omega} {<=} 60 eV the C{sub 60} enhances the incoming radiation. This shows non-metallic dielectric behavior of the 240 collectivized electrons in C{sub 60}. We also discuss the effects of C{sub 60} upon the fast electron inelastic scattering. The results obtained are valid qualitatively also for other than C{sub 60} molecules, e.g. for C{sub 70} or C{sub 76}.

  18. Shell closure in stable and unstable Fermion systems

    International Nuclear Information System (INIS)

    Lombard, R.J.

    1991-01-01

    Some of the findings of calculations performed with the density functional method in connection with shell closure are presented. In nuclei, some evidences seam to confirm the existence of a shell closure at N or Z=16, for Z or N<11. More data, particularly spectroscopic measurements would provide further information. Single particle energies for Z=16 isotopes as function of the neutron number N are given. (G.P.) 9 refs.; 6 figs

  19. Digestive ripening: a synthetic method par excellence for core–shell ...

    Indian Academy of Sciences (India)

    persity of nanoparticles. An even more remarkable feature of digestive ripening exemplified here is, it could be exercised as a synthetic method towards vari- ous heterostructured materials like core–shell particles, nanoalloys, and nanocomposites in combination with the synthetic method, solvated metal atom dispersion.

  20. Atomically Precise Nanocluster Assemblies Encapsulating Plasmonic Gold Nanorods.

    Science.gov (United States)

    Chakraborty, Amrita; Fernandez, Ann Candice; Som, Anirban; Mondal, Biswajit; Natarajan, Ganapati; Paramasivam, Ganesan; Lahtinen, Tanja; Häkkinen, Hannu; Nonappa, Nonappa; Pradeep, Thalappil

    2018-04-01

    We present the self-assembled structures of atomically precise, ligand-protected noble metal nanoclusters leading to encapsulation of plasmonic gold nanorods (GNRs). Unlike highly sophisticated DNA nanotechnology, our approach demonstrates a strategically simple hydrogen bonding-directed self-assembly of nanoclusters leading to octahedral nanocrystals encapsulating GNRs. Specifically, we use the p-mercaptobenzoic acid (pMBA) protected atomically precise nanocluster, Na4[Ag44(pMBA)30] and pMBA functionalized GNRs. High resolution transmission and scanning transmission electron tomographic reconstructions suggest that the geometry of the GNR surface is responsible for directing the assembly of silver nanoclusters via H-bonding leading to octahedral symmetry. Further, use of water dispersible gold nanoclusters, Au~250(pMBA)n and Au102(pMBA)44 also formed layered shells encapsulating GNRs. Such cluster assemblies on colloidal particles present a new category of precision hybrids with diverse possibilities. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Atomic and molecular effects in the VUV spectra of solids

    International Nuclear Information System (INIS)

    Sonntag, B.

    1977-10-01

    The VUV spectra of solids are often dominated by atomic or molecular effects, which clearly manifest themselves in the gross features of the spectra and the fine structure at inner shell excitation thresholds. Evidence for the influence of atomic and molecular matrix elements, multiplet-splitting and correlation is presented. Special emphasis is given to the direct experimental verification based on the comparison of atomic and solid state spectra. (orig.) [de

  2. Comparisons of theoretical and experimental neutron spectra, 115In(n,n') and fission rates, in the centre of three spherical natural uranium and iron shell configurations, located at BR1

    International Nuclear Information System (INIS)

    De Leeuw-Gierts, G.; De Leeuw, S.; Gilliam, D.M.

    1984-01-01

    Three spherical configurations of iron and uranium shells have been studied. The configurations were a 1-cm thick natural uranium shell, a 1-cm thick natural uranium shell with an inner 7-cm thick iron shell and a 1-cm thick natural uranium shell with an inner iron shell of 14-cm thickness. For the measurements, the shells were located at the centre of a hollow cavity, 100-cm in diameter, in the vertical graphite thermal column of the BR1 reactor. The central neutron spectra were calculated by means of the DTF-IV code, using the 208-group KEDAK-3 library, and by means of the ANISN code, using the 171-group VITAMIN-C library. Central neutron spectra, measured by the proton-recoil and 6 Li(n,α)t spectrometry techniques, are compared to the theory between ∼ 100 keV and 5 MeV. Mean fission cross-sections of 240 Pu, 237 Np, 234 U, 235 U, 236 U and 238 U were deduced from the calculations. Their ratios with respect to 238 U are compared to measurements made with NBS dual fission chambers. (Auth.)

  3. Characterization of core-shell nanoparticles by small angle neutron scattering

    Energy Technology Data Exchange (ETDEWEB)

    Strunz, P. [Nuclear Physics Institute (NPI), Rez (Czech Republic); Research Centre Rez, Rez (Czech Republic); Mukherji, D. [TU Braunschweig, IfW, Braunschweig (Germany); Pigozzi, G. [ETH Zuerich, Laboratory for Nanometallurgy, Zuerich (Switzerland); Gilles, R. [TU Muenchen, ZWE FRM-II, Garching (Germany); Geue, T. [PSI and ETH Zuerich, Laboratory for Neutron Scattering, Villigen PSI (Switzerland); Pranzas, K. [GKSS Research Centre, Institute of Materials Research, Geesthacht (Germany)

    2007-08-15

    The Ni{sub 3}Si-type nanoparticles dispersed in a mixture of H{sub 2}O/D{sub 2}O were characterised by SANS using the contrast variation method. The existence of a core-shell structure in the nanoparticles with a Ni{sub 3}Si(Al) core and amorphous SiO{sub x} shell is confirmed by the SANS measurements. The nanoparticles were produced by extracting precipitates from a bulk Ni-13.3Si-2Al (at. %) alloy using electrochemical phase separation technique and were pre-characterised by X-ray diffraction and transmission electron microscopy. By comparing the precipitate morphology in the Ni-Si-Al alloy with the extracted nanoparticles in the SANS measurements, it is clearly established that the precipitates shape and size are unaffected by the extraction process and that the amorphous shell forms on top of the particle core. However, the present measurement could not confirm or exclude the presence of H atoms in the shell structure. (orig.)

  4. Spectrophotometry of the shell around AG Carinae

    Science.gov (United States)

    Mitra, P. Mila; Dufour, Reginald J.

    1990-01-01

    Spatially-resolved long-slit spectrophotometry are presented for two regions of the shell nebula around the P-Cygni variable star AG Carinae. The spectra cover the 3700-6800 A wavelength range. Emission-line diagnostics are used to derive extinction, electron temperatures, and densities for various positions in the nebula. The chemical abundances and ionization structure are calculated and compared with other types of planetary nebulae and shells around other luminous stars. It is found that the N/O and N/S ratios of Ag Car are high compared to solar neighborhood ISM values. The O/H depletion found for the AG Car shell approaches that found in the condensations of the Eta Car system.

  5. Many-electron model for multiple ionization in atomic collisions

    International Nuclear Information System (INIS)

    Archubi, C D; Montanari, C C; Miraglia, J E

    2007-01-01

    We have developed a many-electron model for multiple ionization of heavy atoms bombarded by bare ions. It is based on the transport equation for an ion in an inhomogeneous electronic density. Ionization probabilities are obtained by employing the shell-to-shell local plasma approximation with the Levine and Louie dielectric function to take into account the binding energy of each shell. Post-collisional contributions due to Auger-like processes are taken into account by employing recent photoemission data. Results for single-to-quadruple ionization of Ne, Ar, Kr and Xe by protons are presented showing a very good agreement with experimental data

  6. Many-electron model for multiple ionization in atomic collisions

    Energy Technology Data Exchange (ETDEWEB)

    Archubi, C D [Instituto de AstronomIa y Fisica del Espacio, Casilla de Correo 67, Sucursal 28 (C1428EGA) Buenos Aires (Argentina); Montanari, C C [Instituto de AstronomIa y Fisica del Espacio, Casilla de Correo 67, Sucursal 28 (C1428EGA) Buenos Aires (Argentina); Miraglia, J E [Instituto de AstronomIa y Fisica del Espacio, Casilla de Correo 67, Sucursal 28 (C1428EGA) Buenos Aires (Argentina)

    2007-03-14

    We have developed a many-electron model for multiple ionization of heavy atoms bombarded by bare ions. It is based on the transport equation for an ion in an inhomogeneous electronic density. Ionization probabilities are obtained by employing the shell-to-shell local plasma approximation with the Levine and Louie dielectric function to take into account the binding energy of each shell. Post-collisional contributions due to Auger-like processes are taken into account by employing recent photoemission data. Results for single-to-quadruple ionization of Ne, Ar, Kr and Xe by protons are presented showing a very good agreement with experimental data.

  7. An efficient, selective collisional ejection mechanism for inner-shell population inversion in laser-driven plasmas

    Energy Technology Data Exchange (ETDEWEB)

    SCHROEDER,W. ANDREAS; NELSON,THOMAS R.; BORISOV,A.B.; LONGWORTH,J.W.; BOYER,K.; RHODES,C.K.

    2000-06-07

    A theoretical analysis of laser-driven collisional ejection of inner-shell electrons is presented to explain the previously observed anomalous kilovolt L-shell x-ray emission spectra from atomic Xe cluster targets excited by intense sub-picosecond 248nrn ultraviolet radiation. For incident ponderomotively-driven electrons photoionized by strong above threshold ionization, the collisional ejection mechanism is shown to be highly l-state and significantly n-state (i.e. radially) selective for time periods shorter than the collisional dephasing time of the photoionized electronic wavefunction. The resulting preference for the collisional ejection of 2p electrons by an ionized 4p state produces the measured anomalous Xe(L) emission which contains direct evidence for (i) the generation of Xe{sup 27+}(2p{sup 5}3d{sup 10}) and Xe{sup 28+}(2p{sup 5}3d{sup 9}) ions exhibiting inner-shell population inversion and (ii) a coherent correlated electron state collision responsible for the production of double 2p vacancies. For longer time periods, the selectivity of this coherent impact ionization mechanism is rapidly reduced by the combined effects of intrinsic quantum mechanical spreading and dephasing--in agreement with the experimentally observed and extremely strong {minus}{lambda}{sup {minus}6} pump-laser wavelength dependence of the efficiency of inner-shell (2p) vacancy production in Xe clusters excited in underdense plasmas.

  8. Two-photon decay in heavy atoms and ions

    International Nuclear Information System (INIS)

    Mokler, P.H.; Dunford, R.W

    2003-08-01

    We review the status of and comment on current developments in the field of two-photon decay in atomic physics research. Recent work has focused on two-photon decays in highly-charged ions and two-photon decay of inner-shell vacancies in heavy neutral atoms. We emphasize the importance of measuring the shape of the continuum emission in two-photon decay as a probe of relativistic effects in the strong central fields found in heavy atomic systems. New experimental approaches and their consequences will be discussed. (orig.)

  9. Atomic x-ray production by relativistic heavy ions

    International Nuclear Information System (INIS)

    Ioannou, J.G.

    1977-12-01

    The interaction of heavy ion projectiles with the electrons of target atoms gives rise to the production, in the target, of K-, L- or higher shell vacancies which are in turn followed by the emission of characteristic x-rays. The calculation of the theoretical value of the K- and L-shells vacancy production cross section was carried out for heavy ion projectiles of any energy. The transverse component of the cross section is calculated for the first time in detail and extensive tables of its numerical value as a function of its parameters are also given. Experimental work for 4.88 GeV protons and 3 GeV carbon ions is described. The K vacancy cross section has been measured for a variety of targets from Ti to U. The agreement between the theoretical predictions and experimental results for the 4.88 GeV protons is rather satisfactory. For the 3 GeV carbon ions, however, it is observed that the deviation of the theoretical and experimental values of the K vacancy production becomes larger with the heavier target element. Consequently, the simple scaling law of Z 1 2 for the cross section of the heavy ion with atomic number Z 1 to the proton cross section is not true, for the K-shell at least. A dependence on the atomic number Z 2 of the target of the form (Z 1 - αZ 2 ) 2 , instead of Z 1 2 , is found to give extremely good agreement between theory and experiment. Although the exact physical meaning of such dependence is not yet clearly understood, it is believed to be indicative of some sort of screening effect of the incoming fast projectile by the fast moving in Bohr orbits K-shell electrons of the target. The enhancement of the K-shell ionization cross section by relativistic heavy ions on heavy targets is also discussed in terms of its practical applications in various branches of science and technology

  10. Plasma-column instabilities in a reversed-field pinch without a shell

    Energy Technology Data Exchange (ETDEWEB)

    Schmid, P.G.

    1988-01-01

    Plasma column instabilities in a Reversed Field Pinch (RFP) without a shell were investigated in the Colorado Reversatron RFP. The Reversatron RFP (aspect ration R/a = 50 cm/8cm) is a toroidal plasma containment device consisting of a vacuum chamber, a thick conducting shell, modular shells, magnetic field producing coils and diagnostics to characterize the plasma. RFP discharges were set up in the Reversatron in three different experimental configurations: with a thick conducting shell, with a modular shell and with no shell. In two of the configurations, a shell enclosed the plasma column to provide some plasma stability. A vertical magnetic field provided equilibrium in experiments without a shell. Data from discharges without a shell indicated that the plasma duration was greatly reduced and the plasma resistance increased compared to the discharges with a thick shell. Plasma position probes indicated large plasma centriod displacements corresponding to a n = 1 and a n = 3 kink coincident with the peak of the plasma current and the start of a discharge termination phase. The modular shell lengthened the discharge duration and lowered the plasma resistance to values intermediate between the plasma with a thick shell and the plasma with no shell. The modular shell suppressed the large plasma column displacements observed in the RFP plasma without a shell.

  11. Plasma-column instabilities in a reversed-field pinch without a shell

    International Nuclear Information System (INIS)

    Schmid, P.G.

    1988-01-01

    Plasma column instabilities in a Reversed Field Pinch (RFP) without a shell were investigated in the Colorado Reversatron RFP. The Reversatron RFP (aspect ration R/a = 50 cm/8cm) is a toroidal plasma containment device consisting of a vacuum chamber, a thick conducting shell, modular shells, magnetic field producing coils and diagnostics to characterize the plasma. RFP discharges were set up in the Reversatron in three different experimental configurations: with a thick conducting shell, with a modular shell and with no shell. In two of the configurations, a shell enclosed the plasma column to provide some plasma stability. A vertical magnetic field provided equilibrium in experiments without a shell. Data from discharges without a shell indicated that the plasma duration was greatly reduced and the plasma resistance increased compared to the discharges with a thick shell. Plasma position probes indicated large plasma centriod displacements corresponding to a n = 1 and a n = 3 kink coincident with the peak of the plasma current and the start of a discharge termination phase. The modular shell lengthened the discharge duration and lowered the plasma resistance to values intermediate between the plasma with a thick shell and the plasma with no shell. The modular shell suppressed the large plasma column displacements observed in the RFP plasma without a shell

  12. Two-dimensional atom localization via a coherence-controlled absorption spectrum in an N-tripod-type five-level atomic system

    International Nuclear Information System (INIS)

    Ding Chunling; Li Jiahua; Yang Xiaoxue; Zhan Zhiming; Liu Jibing

    2011-01-01

    A scheme of two-dimensional atom localization based on a coherence-controlled absorption spectrum in an N-tripod-type five-level system is proposed, in which the atom interacts with a weak probe field and three standing-wave fields. Position information of the atom can be achieved by measuring the probe absorption. It is found that the localization properties are significantly improved due to the interaction of dark resonances. It is also shown that the localization factors depend strongly on the system parameters that lead to such spatial structures of localization as chain-like, wave-like, '8'-like, spike-like, crater-like and heart-like patterns. By properly adjusting the system parameters, we can achieve a high-precision and high-resolution atom localization under certain conditions.

  13. Electron-nuclear γ transition spectrum of a nucleus in a multicharged atomic ion

    International Nuclear Information System (INIS)

    Ivanov, L.N.; Letokhov, V.S.

    1987-01-01

    The nuclear emission of absorption spectrum of an atom possesses a set of electron satelites which are due to an alternation of the state of the electron shell. It is shown that the mechanism of formation of the satellites might be different for neutral atoms and high-charge ions. In the first case (loose electron shell) a ''shaking'' of the shell resulting from the interaction between the nucleus and γ quantum is predominant. In the second case (rigid electron shell) the mechanism involves a direct interaction between the γ quantum and electrons. The second mechanism is important in the case of dipole nuclear transitions and dominates at γ quantum energies p 2λ (λ is the nuclear transition multipole order, μ p ∼ 1/2 π is the relative proton mass and z the core mass). In the spectrum of the plasma source the electron satellites corresponding to the γ quantum emission and absorption lines are not overlapped by the Doppler contour of the γ line

  14. Absolute cross-section measurements of inner-shell ionization

    Science.gov (United States)

    Schneider, Hans; Tobehn, Ingo; Ebel, Frank; Hippler, Rainer

    1994-12-01

    Cross section ratios for K- and L-shell ionization of thin silver and gold targets by positron and electron impact have been determined at projectile energies of 30 70 keV. The experimental results are confirmed by calculations in plane wave Born approximation (PWBA) which include an electron exchange term and account for the deceleration or acceleration of the incident projectile in the nuclear field of the target atom. We report first absolute cross sections for K- and L-shell ionization of silver and gold targets by lepton impact in the threshold region. We have measured the corresponding cross sections for electron (e-) impact with an electron gun and the same experimental set-up.

  15. Design, fabrication and testing of a prototype stressed-shell fuel isolation container

    International Nuclear Information System (INIS)

    Crosthwaite, J.L.; Barrie, J.N.; Nuttall, K.

    1982-07-01

    Atomic Energy of Canada Limited is conducting and coordinating research into the development of engineered barriers for the disposal of unreprocessed irradiated fuel within a deep, stable geologic vault. In one approach, a containment shell of corrosion-resistant metal is proposed as the principal barrier to radionuclide release, giving a high probability of containment for at least 300 years, thus ensuring isolation of nearly all fission products for their hazardous lives. The simplest concept is the 'stressed-shell' container, designed with sufficient shell thickness to withstand the hydrostatic pressure within a 1000-m deep disposal vault postulated to have flooded with groundwater. This report describes the design, fabrication, analysis and hydrostatic testing of a full-scale stressed-shell prototype. The report concludes that the deformation and collapse performance of stressed-shell designs, based on short-term mechanical properties be modelled adequately by BOSOR 5, a commercially available stress-strain computer program. If the stressed-shell concept is retained as a viable fuel isolation concept, future analyses should include an assessment of the role of material creep on long-term container performance

  16. Local atomic characterization of LiCo1/3Ni1/3Mn1/3O2 cathode material

    International Nuclear Information System (INIS)

    Nedoseykina, Tatiana; Kim, Sung-Soo; Nitta, Yoshiaki

    2006-01-01

    Co, Ni and Mn K-edge XAFS investigation of LiCo 1/3 Ni 1/3 Mn 1/3 O 2 as alternative cathode material to commercially used LiCoO 2 in lithium rechargeable battery has been performed. Parameters of a local atomic structure such as radii of metal-oxygen and metal-metal coordination shells and disorder in those shells have been determined. It has been found that the radius of the first coordination shell (metal-oxygen) as well as a local disorder in the second shell (metal-metal) around each of the 3d-metals are in a good agreement with obtained for superlattice model of √3 x √3] R30 o type in triangular lattice of sites by first principle calculation. Other parameters of the local atomic structure around Co, Ni and Mn atoms do not provide evidence for presence of superstructure in LiCo 1/3 Ni 1/3 Mn 1/3 O 2

  17. Cross Sections for Inner-Shell Ionization by Electron Impact

    Energy Technology Data Exchange (ETDEWEB)

    Llovet, Xavier, E-mail: xavier@ccit.ub.edu [Centres Científics i Tecnològics, Universitat de Barcelona, Lluís Solé i Sabarís 1-3, 08028 Barcelona (Spain); Powell, Cedric J. [Materials Measurement Science Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8370 (United States); Salvat, Francesc [Facultat de Física (ECM and ICC), Universitat de Barcelona, Diagonal 645, 08028 Barcelona (Spain); Jablonski, Aleksander [Institute of Physical Chemistry, Polish Academy of Sciences, ul. Kasprzaka 44/52, 01-224 Warsaw (Poland)

    2014-03-15

    An analysis is presented of measured and calculated cross sections for inner-shell ionization by electron impact. We describe the essentials of classical and semiclassical models and of quantum approximations for computing ionization cross sections. The emphasis is on the recent formulation of the distorted-wave Born approximation by Bote and Salvat [Phys. Rev. A 77, 042701 (2008)] that has been used to generate an extensive database of cross sections for the ionization of the K shell and the L and M subshells of all elements from hydrogen to einsteinium (Z = 1 to Z = 99) by electrons and positrons with kinetic energies up to 1 GeV. We describe a systematic method for evaluating cross sections for emission of x rays and Auger electrons based on atomic transition probabilities from the Evaluated Atomic Data Library of Perkins et al. [Lawrence Livermore National Laboratory, UCRL-ID-50400, 1991]. We made an extensive comparison of measured K-shell, L-subshell, and M-subshell ionization cross sections and of Lα x-ray production cross sections with the corresponding calculated cross sections. We identified elements for which there were at least three (for K shells) or two (for L and M subshells) mutually consistent sets of cross-section measurements and for which the cross sections varied with energy as expected by theory. The overall average root-mean-square deviation between the measured and calculated cross sections was 10.9% and the overall average deviation was −2.5%. This degree of agreement between measured and calculated ionization and x-ray production cross sections was considered to be very satisfactory given the difficulties of these measurements.

  18. Analytical local electron-electron interaction model potentials for atoms

    International Nuclear Information System (INIS)

    Neugebauer, Johannes; Reiher, Markus; Hinze, Juergen

    2002-01-01

    Analytical local potentials for modeling the electron-electron interaction in an atom reduce significantly the computational effort in electronic structure calculations. The development of such potentials has a long history, but some promising ideas have not yet been taken into account for further improvements. We determine a local electron-electron interaction potential akin to those suggested by Green et al. [Phys. Rev. 184, 1 (1969)], which are widely used in atom-ion scattering calculations, electron-capture processes, and electronic structure calculations. Generalized Yukawa-type model potentials are introduced. This leads, however, to shell-dependent local potentials, because the origin behavior of such potentials is different for different shells as has been explicated analytically [J. Neugebauer, M. Reiher, and J. Hinze, Phys. Rev. A 65, 032518 (2002)]. It is found that the parameters that characterize these local potentials can be interpolated and extrapolated reliably for different nuclear charges and different numbers of electrons. The analytical behavior of the corresponding localized Hartree-Fock potentials at the origin and at long distances is utilized in order to reduce the number of fit parameters. It turns out that the shell-dependent form of Green's potential, which we also derive, yields results of comparable accuracy using only one shell-dependent parameter

  19. Mg dopant distribution in an AlGaN/GaN p-type superlattice assessed using atom probe tomography, TEM and SIMS

    International Nuclear Information System (INIS)

    Bennett, S E; Kappers, M J; Barnard, J S; Humphreys, C J; Oliver, R A; Clifton, P H; Ulfig, R M

    2010-01-01

    P-type conducting layers are critical in GaN-based devices such as LEDs and laser diodes. Such layers are often produced by doping GaN with Mg, but the hole concentration can be enhanced using AlGaN/GaN p-type superlattices by exploiting the built-in polarisation fields. A Mg-doped AlGaN/GaN superlattice was studied using SIMS. Although the AlGaN and GaN were nominally doped to the same level, the SIMS data suggested a difference in doping density between the two materials. Atom probe tomography was then used to investigate the Mg distribution. The superlattice repeats were clearly visible, as expected and, in addition, significant Mg clustering was observed in both the GaN and AlGaN layers. There were many more Mg clusters in the AlGaN layers than the GaN layers, accounting for the difference in doping density suggested by SIMS. To evaluate the structural accuracy of the atom probe reconstruction, layer thicknesses from the atom probe were compared with STEM images. Finally, future work is proposed to investigate the Mg clusters in the TEM.

  20. Manipulation of inherent characteristics of graphene through N and Mg atom co-doping; a DFT study

    Science.gov (United States)

    Rafique, Muhammad; Mirjat, Nayyar H.; Soomro, Aamir M.; Khokhar, Suhail; Shuai, Yong

    2018-04-01

    First-principles calculations were performed to investigate the structural, electronic, magnetic and optical properties of nitrogen (N) and magnesium (Mg) atom co-doped graphene systems. We observed that, N and Mg atom co-doping in graphene, introduces half-metallic properties in the electronic structure of graphene, introduces ferromagnetism behavior along with new trends in optical properties of graphene. Doping site and concentration of N and Mg atoms in graphene was changed and resulting effects of these changes on aforementioned properties were investigated. Through density of states plots we observed that, Mg atom sp orbitals mainly induced magnetic moments in graphene. It was revealed that, N/Mg atoms substitution in graphene introduces a red shift in absorption spectrum towards visible range and a finite absorption coefficient quantity value in 0 to 3 eV and 7 to 11 eV energy intervals is also produced, that is unavailable for absorption spectrum of intrinsic graphene. Moreover, N/Mg atoms co-doping produces increment in the reflectivity parameter of graphene in low lying energy region, while producing diminishing behavior in the higher energy range. These results offer a possibility to tune electronic, magnetic and optical characteristics of graphene sufficiently for utilization in graphene based spintronic and optoelectronic devices.

  1. The fission time scale measured with an atomic clock

    NARCIS (Netherlands)

    Kravchuk, VL; Wilschut, HW; Hunyadi, M; Kopecky, S; Lohner, H; Rogachevskiy, A; Siemssen, RH; Krasznahorkay, A; Hamilton, JH; Ramayya, AV; Carter, HK

    2003-01-01

    We present a new direct method of measuring the fission absolute time scale using an atomic clock based on the lifetime of a vacancy in the atomic K-shell. We studied the reaction Ne-20 + Th-232 -> O-16 + U-236* at 30 MeV/u. The excitation energy of about 115 MeV in such a reaction is in the range

  2. Lanthanum(III) and Lutetium(III) in Nitrate-Based Ionic Liquids: A Theoretical Study of Their Coordination Shell.

    Science.gov (United States)

    Bodo, Enrico

    2015-09-03

    By using ab initio molecular dynamics, we investigate the solvent shell structure of La(3+) and Lu(3+) ions immersed in two ionic liquids, ethylammonium nitrate (EAN) and its hydroxy derivative (2-ethanolammonium nitrate, HOEAN). We provide the first study of the coordination properties of these heavy metal ions in such a highly charged nonacqueous environment. We find, as expected, that the coordination in the liquid is mainly due to nitrate anions and that, due to the bidentate nature of the ligand, the complexation shell of the central ion has a nontrivial geometry and a coordination number in terms of nitrate molecules that apparently violates the decrease of ionic radii along the lanthanides series, since the smaller Lu(3+) ion seems to coordinate six nitrate molecules and the La(3+) ion only five. A closer inspection of the structural features obtained from our calculations shows, instead, that the first shell of oxygen atoms is more compact for Lu(3+) than for La(3+) and that the former coordinates 8 oxygen atoms while the latter 10 in accord with the typical lanthanide's trend along the series and that their first solvation shells have a slight irregular and complex geometrical pattern. When moving to the HOEAN solutions, we have found that the solvation of the central ion is possibly also due to the cation itself through the oxygen atom on the side chain. Also, in this liquid, the coordination numbers in terms of oxygen atoms in both solvents is 10 for La(3+) and 8 for Lu(3+).

  3. Experimental and theoretical studies of metal vapor atoms

    International Nuclear Information System (INIS)

    Whitfield, S.B.; Wehlitz, Ralf; Martins, Michael

    2004-01-01

    Employing electron spectrometry in conjunction with tuneable synchrotron radiation, we will present a detailed examination of the photoionization dynamics of selected metal vapor atoms. In particular, this paper will focus on the relative partial cross sections of the atomic Li K-shell main and satellite (ionization with excitation) photoelectron lines in the region of the strong 1snln'l' autoionizing transitions, the atomic Sc 3d, 4s main and satellite photoelectron lines in the region of the 3p→3d giant resonance, and also the atomic Fe 3d, 4s main and satellite photoelectron lines in the same resonance region. Our experimental data for Sc and Fe will be compared to our state-of-the-art calculations based on the superposition of configuration method developed by Cowan (The Theory of Atomic Structure and Spectra. University of California Berkeley Press, Berkeley and Los Angeles, 1981). Our partial cross section measurements for Li and Sc will be complemented with measurements of the angular distribution parameter, β. In addition, our Li data will also be compared with recent R-matrix calculations (Phys. Rev. 57 (1998) 1045). In the case of Fe, we will also address the term dependent behavior of the partial cross sections on resonance. These results will highlight what can be achieved with today's technology and point the way towards future endeavors in the study of the photoionization dynamics of open-shell metal vapor atoms

  4. On the spectral properties of Dirac operators with electrostatic delta-shell interactions

    Czech Academy of Sciences Publication Activity Database

    Behrndt, J.; Exner, Pavel; Holzmann, M.; Lotoreichik, Vladimir

    2018-01-01

    Roč. 111, č. 3 (2018), s. 47-78 ISSN 0021-7824 R&D Projects: GA ČR(CZ) GA14-06818S Institutional support: RVO:61389005 Keywords : Dirac operator * self-adjoint extension * shell interaction * spectral properties Subject RIV: BE - Theoretical Physics OBOR OECD: Atomic, molecular and chemical physics (physics of atoms and molecules including collision, interaction with radiation, magnetic resonances, Mössbauer effect) Impact factor: 1.802, year: 2016

  5. NIF Double Shell outer/inner shell collision experiments

    Science.gov (United States)

    Merritt, E. C.; Loomis, E. N.; Wilson, D. C.; Cardenas, T.; Montgomery, D. S.; Daughton, W. S.; Dodd, E. S.; Desjardins, T.; Renner, D. B.; Palaniyappan, S.; Batha, S. H.; Khan, S. F.; Smalyuk, V.; Ping, Y.; Amendt, P.; Schoff, M.; Hoppe, M.

    2017-10-01

    Double shell capsules are a potential low convergence path to substantial alpha-heating and ignition on NIF, since they are predicted to ignite and burn at relatively low temperatures via volume ignition. Current LANL NIF double shell designs consist of a low-Z ablator, low-density foam cushion, and high-Z inner shell with liquid DT fill. Central to the Double Shell concept is kinetic energy transfer from the outer to inner shell via collision. The collision determines maximum energy available for compression and implosion shape of the fuel. We present results of a NIF shape-transfer study: two experiments comparing shape and trajectory of the outer and inner shells at post-collision times. An outer-shell-only target shot measured the no-impact shell conditions, while an `imaging' double shell shot measured shell conditions with impact. The `imaging' target uses a low-Z inner shell and is designed to perform in similar collision physics space to a high-Z double shell but can be radiographed at 16keV, near the viable 2DConA BL energy limit. Work conducted under the auspices of the U.S. DOE by LANL under contract DE-AC52-06NA25396.

  6. Comparisons between shell-model calculations, seniority truncation, and quasiparticle approximations: Application to the odd Ni isotopes and odd N = 82 isotones

    International Nuclear Information System (INIS)

    Losano, L.; Dias, H.; Krmpotic, F.; Wildenthal, B.H.

    1988-01-01

    A detailed study of the results of correcting BCS approximation for the effects of particle-number projection and blocking has been carried out. A low-seniority shell-model approximation was used as the frame of reference for investigating the mixing of one- and three-quasiparticle states in odd-mass Ni isotopes and in odd-mass N = 82 isotones. We discuss the results obtained for the energy spectra and electromagnetic decay properties. Effects of seniority-five configurations on the low-lying states have also been studied through the comparison of the low-seniority shell-model results with those which arose from the corresponding full shell-model calculations

  7. Radial behavior of the average local ionization energies of atoms

    International Nuclear Information System (INIS)

    Politzer, P.; Murray, J.S.; Grice, M.E.; Brinck, T.; Ranganathan, S.

    1991-01-01

    The radial behavior of the average local ionization energy bar I(r) has been investigated for the atoms He--Kr, using ab initio Hartree--Fock atomic wave functions. bar I(r) is found to decrease in a stepwise manner with the inflection points serving effectively to define boundaries between electronic shells. There is a good inverse correlation between polarizability and the ionization energy in the outermost region of the atom, suggesting that bar I(r) may be a meaningful measure of local polarizabilities in atoms and molecules

  8. Two-photon emission and multiphoton absorption by atoms

    International Nuclear Information System (INIS)

    Mu, X.

    1988-01-01

    This thesis consists of investigations of two problems concerning photon-atom interactions. The first topic deals with two-photon transitions in atomic inner shells. An independent-particle model has been used to describe the two-photon transitions between different inner-shell electron states. The first relativistic self-consistent-field calculation of these transition rates in Ag, Mo, and Xe has been carried out. The theoretical results are compared with recent measurements. Good agreement with measured rates is found except in some cases where more reliable experiments still need to be done. The second topic is multiphoton multiionization of atoms. The maximum entropy principle has been employed in this theoretical investigation. A detailed statistical analysis of measured ionic charge distributions produced in strong laser pulses has been carried out. The results of this analysis indicates that the charge-state distribution is a Poissonian, rather than the binomial which prevails under infrared radiation, and hence that ionization occurs stepwise during the pulse. This result is shown to be consistent with experimental data

  9. Plasma-activated core-shell gold nanoparticle films with enhanced catalytic properties

    Energy Technology Data Exchange (ETDEWEB)

    Llorca, Jordi, E-mail: jordi.llorca@upc.edu; Casanovas, Albert; Dominguez, Montserrat; Casanova, Ignasi [Universitat Politecnica de Catalunya, Institut de Tecniques Energetiques (Spain); Angurell, Inmaculada; Seco, Miquel; Rossell, Oriol [Universitat de Barcelona, Departament de Quimica Inorganica (Spain)

    2008-03-15

    Catalytically active gold nanoparticle films have been prepared from core-shell nanoparticles by plasma-activation and characterized by high-resolution transmission electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy. Methane can be selectively oxidized into formic acid with an O{sub 2}-H{sub 2} mixture in a catalytic wall reactor functionalized with plasma-activated gold nanoparticle films containing well-defined Au particles of about 3.5 nm in diameter. No catalytic activity was recorded over gold nanoparticle films prepared by thermal decomposition of core-shell nanoparticles due to particle agglomeration.

  10. Plasma-activated core-shell gold nanoparticle films with enhanced catalytic properties

    International Nuclear Information System (INIS)

    Llorca, Jordi; Casanovas, Albert; Dominguez, Montserrat; Casanova, Ignasi; Angurell, Inmaculada; Seco, Miquel; Rossell, Oriol

    2008-01-01

    Catalytically active gold nanoparticle films have been prepared from core-shell nanoparticles by plasma-activation and characterized by high-resolution transmission electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy. Methane can be selectively oxidized into formic acid with an O 2 -H 2 mixture in a catalytic wall reactor functionalized with plasma-activated gold nanoparticle films containing well-defined Au particles of about 3.5 nm in diameter. No catalytic activity was recorded over gold nanoparticle films prepared by thermal decomposition of core-shell nanoparticles due to particle agglomeration

  11. Modification of the Xe 4d giant resonance by the C60 shell in molecular Xe at C60

    International Nuclear Information System (INIS)

    Amusia, M. Ya.; Baltenkov, A. S.; Chernysheva, L. V.; Felfli, Z.; Msezane, A. Z.

    2006-01-01

    It is demonstrated that in photoabsorption of the 4d 10 subshell of a Xe atom in molecular Xe at C 60 , the 4d giant resonance that characterizes the isolated Xe atom is distorted significantly. The reflection of photoelectron waves by the C 60 shell leads to profound oscillations in the photoionization cross section such that the Xe giant resonance is transformed into four strong peaks. Similarly, the angular anisotropy parameters, both dipole and nondipole, are also modified. The method of calculation is based on the approximation of the C 60 shell by an infinitely thin bubble potential that leaves the sum rule for the 4d-electrons almost unaffected, but noticeably modifies the dipole polarizability of the 4d-shell

  12. Metallic double shell hollow nanocages: the challenges of their synthetic techniques.

    Science.gov (United States)

    Mahmoud, M A; El-Sayed, M A

    2012-03-06

    Hollow metallic nanoparticles have been attracting the attention of many researchers in the past five years due to their new properties and potential applications. The unique structure of the hollow nanoparticles; presence of two surfaces (internal and external), and the presence of both cavities and pores in the wall surfaces of these nanoparticles are responsible for their unique properties and applications. Here the galvanic replacement technique is used to prepare nanocages made of gold, platinum, and palladium. In addition, hollow double shell nanoparticles are made of two metal shells like Au-Pt, Pt-Au, Au-Pd, Pd-Au, Pd-Pt, and Pt-Pd. Silver nanocubes are used as templates during the synthesis of hollow nanoparticles with single metal shell or double shell nanocages. Most of the problems that could affect the synthesis of solid Silver nanocubes used as template as well as the double shell nanocages and their possible solutions are discussed in a detail. The sizes and shapes of the single-shell and double-shell nanocages were characterized by a regular and high-resolution TEM. A SEM mapping technique is also used to image the surface atoms for the double shell hollow nanoparticles in order to determine the thickness of the two metal shells. In addition, optical studies are used to monitor the effect of the dielectric properties of the other metals on the plasmonic properties of the gold nanoshell in these mixed nanoparticles.

  13. The SCA description of inner-shell Coulomb ionization and associated phenomena

    International Nuclear Information System (INIS)

    Hansteen, J.M.

    1989-01-01

    The semiclassical trajectory method for describing atomic processes induced by charged projectiles is outlined. The framework for the perturbative SCA formalism is sketched with emphasis on the first-order time-dependent approach. Selected results from computations on inner-shell Coulomb ionization and δ-electron emission are presented. The kinematic scaling law for ionization and pair-production phenomena is treated in detail. The importance of this scaling law for high-energy atomic collision physics is stressed. (orig.)

  14. A Lorentz covariant holoraumy-induced “gadget” from minimal off-shell 4D, N=1 supermultiplets

    Energy Technology Data Exchange (ETDEWEB)

    Gates, James S. Jr.; Grover, Tyler; Miller-Dickson, Miles David; Mondal, Benedict A.; Oskoui, Amir; Regmi, Shirash [Center for String and Particle Theory, Department of Physics, University of Maryland,College Park, MD 20742-4111 (United States); Ross, Ethan [Center for String and Particle Theory, Department of Physics, University of Maryland,College Park, MD 20742-4111 (United States); Department of Mathematics, University of Alberta, Edmonton, AB 3, T6G 2R3 (Canada); Shetty, Rajath [Center for String and Particle Theory, Department of Physics, University of Maryland,College Park, MD 20742-4111 (United States)

    2015-11-17

    Starting from three minimal off-shell 4D, N=1 supermultiplets, using constructions solely defined within the confines of the four dimensional field theory we show the existence of a “gadget” — a member of a class of metrics on the representation space of the supermultiplets — whose values directly and completely correspond to the values of a metric defined on the 1d, N=4 adinkra networks adjacency matrices corresponding to the projections of the four dimensional supermultiplets.

  15. Nuclear mass formula with the shell energies obtained by a new method

    International Nuclear Information System (INIS)

    Koura, H.; Tachibana, T.; Yamada, M.; Uno, M.

    1998-01-01

    Nuclear shapes and masses are estimated by a new method. The main feature of this method lies in estimating shell energies of deformed nuclei from spherical shell energies by mixing them with appropriate weights. The spherical shell energies are calculated from single-particle potentials, and, till now, two mass formulas have been constructed from two different sets of potential parameters. The standard deviation of the calculated masses from all the experimental masses of the 1995 Mass Evaluation is about 760 keV. Contrary to the mass formula by Tachibana, Uno, Yamada and Yamada in the 1987-1988 Atomic Mass Predictions, the present formulas can give nuclear shapes and predict on super-heavy elements

  16. Barium atoms and N20 molecular agregates reaction

    International Nuclear Information System (INIS)

    Visticot, J.P.; Mestdagh, J.M.; Alcaraz, C.; Cuvellier, J.; Berlande, J.

    1988-06-01

    The collisions between a barium atom and N20 molecular agregates are studied, for a better understanding of the solvation part in a chemical reaction. The experiments are carried out in a crossed molecular beam device. The light coming from the collision zone is scattered, and analysed by means of a photon detector. A time-of-flight technique is applied in the investigation of the beam's polymer concentration. The results show a nearly negligible chemiluminescent effect in the reaction between barium and N20 polymer. A solvated BaO formation mechanism is proposed to justify the experimental results [fr

  17. Generation of L sub-shell photo-ionization cross-sections for elements 18Z92 at energies .320-115.606 keV (A computer program 'LSPICS')

    International Nuclear Information System (INIS)

    Sharma, Ajay; Mittal, Raj

    2005-01-01

    L sub-shell photo-ionization cross-sections, σ Li , for elements 18Z92 at energies .320-115.606 keV have been generated from an empirical relation fitted to Scofield's L sub-shell photo-ionization cross-section values. The excitation energy E for an element is constrained by the condition that only L and higher shell vacancies are produced in the elements. The closeness of generated and existing values of Scofield's L sub-shell data recommends the use of generated values in the fields of atomic and molecular physics and for trace elemental analysis. For this purpose computer software 'LSPICS' has been developed. On personal computer LSPICS generates L sub-shell photo-ionization cross-section values in barns just by entering the atomic number of element and excitation photon energy in keV

  18. Two-dimensional atom localization via a coherence-controlled absorption spectrum in an N-tripod-type five-level atomic system

    Energy Technology Data Exchange (ETDEWEB)

    Ding Chunling; Li Jiahua; Yang Xiaoxue [Wuhan National Laboratory for Optoelectronics and School of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China); Zhan Zhiming [School of Physics and Information Engineering, Jianghan University, Wuhan 430056 (China); Liu Jibing, E-mail: clding2006@126.com, E-mail: huajia_li@163.com [Department of Physics, Hubei Normal University, Huangshi 435002 (China)

    2011-07-28

    A scheme of two-dimensional atom localization based on a coherence-controlled absorption spectrum in an N-tripod-type five-level system is proposed, in which the atom interacts with a weak probe field and three standing-wave fields. Position information of the atom can be achieved by measuring the probe absorption. It is found that the localization properties are significantly improved due to the interaction of dark resonances. It is also shown that the localization factors depend strongly on the system parameters that lead to such spatial structures of localization as chain-like, wave-like, '8'-like, spike-like, crater-like and heart-like patterns. By properly adjusting the system parameters, we can achieve a high-precision and high-resolution atom localization under certain conditions.

  19. Inner-shell ionization of atoms by electron, positron and photon impacts

    International Nuclear Information System (INIS)

    Khare, S.P.; Sinha, P.; Wadehra, J.M.

    1994-01-01

    Plane wave Born approximation with Coulomb, relativistic and exchange corrections is employed to obtain L1-, L2- and L3-subshell ionization cross sections of several atoms due to electron and positron impacts for projectile energy varying from the threshold of ionization to 60 times the threshold energy. Photoionization cross sections for all the three L-subshells of the atoms are also calculated using the hydrogenic approximation for the atomic wave functions. For L3-subshell the present cross sections due to electron impact are in good agreement with a number of experimental data for different atoms over the entire energy range investigated. For L1- and L2-subshells the present calculations yield qualitative agreement with the experimental data. The agreement between the present results and the limited experimental data for positron impact is also satisfactory. The hydrogenic approximation for the L-subshell photoionization is found to be good at small photon energies but it underestimates the cross sections at large photon energies. (orig.)

  20. Delayed neutron emission near the shell-closures

    Directory of Open Access Journals (Sweden)

    Borzov Ivan

    2016-01-01

    Full Text Available The self-consistent Density Functional + Continuum QRPA approach (DF+CQRPA provides a good description of the recent experimental beta-decay half-lives and delayed neutron emission branchings for the nuclei approaching to (and beyond the neutron closed shells N = 28; 50; 82. Predictions of beta-decay properties are more reliable than the ones of standard global approaches traditionally used for the r-process modelling. An impact of the quasi-particle phonon coupling on the delayed multi-neutron emission rates P2n, P3n,… near the closed shells is also discussed.

  1. Pairing correlations in N ∝Z pf-shell nuclei

    International Nuclear Information System (INIS)

    Langanke, K.; Dean, D.J.; Koonin, S.E.; Radha, P.B.

    1997-01-01

    We perform shell model Monte Carlo calculations to study pair correlations in the ground states of N=Z nuclei with masses A=48-60. We find that T=1, J π =0 + proton-neutron correlations play an important, and even dominant role, in the ground states of odd-odd N=Z nuclei, in agreement with experiment. By studying pairing in the ground states of 52-58 Fe, we observe that the isovector proton-neutron correlations decrease rapidly with increasing neutron excess. In contrast, both the proton, and trivially the neutron correlations increase as neutrons are added. We also study the thermal properties and the temperature dependence of pair correlations for 50 Mn and 52 Fe as exemplars of odd-odd and even-even N=Z nuclei. While for 52 Fe results are similar to those obtained for other even-even nuclei in this mass range, the properties of 50 Mn at low temperatures are strongly influenced by isovector neutron-proton pairing. In coexistence with these isovector pair correlations, our calculations also indicate an excess of isoscalar proton-neutron pairing over the mean-field values. The isovector neutron-proton correlations rapidly decrease with temperatures and vanish for temperatures above T=700 keV, while the isovector correlations among like-nucleons persist to higher temperatures. Related to the quenching of the isovector proton-neutron correlations, the average isospin decreases from 1, appropriate for the ground state, to 0 as the temperature increases. (orig.)

  2. Nitrogen-doped porous carbon from Camellia oleifera shells with enhanced electrochemical performance

    International Nuclear Information System (INIS)

    Zhai, Yunbo; Xu, Bibo; Zhu, Yun; Qing, Renpeng; Peng, Chuan; Wang, Tengfei; Li, Caiting; Zeng, Guangming

    2016-01-01

    Nitrogen doped porous activated carbon was prepared by annealing treatment of Camellia oleifera shell activated carbon under NH 3 . We found that nitrogen content of activated carbon up to 10.43 at.% when annealed in NH 3 at 800 °C. At 600 °C or above, the N-doped carbon further reacts with NH 3 , leads to a low surface area down to 458 m 2 /g and low graphitization degree. X-ray photoelectron spectroscope (XPS) analysis indicated that the nitrogen functional groups on the nitrogen-doped activated carbons (NACs) were mostly in the form of pyridinic nitrogen. We discovered that the oxygen groups and carbon atoms at the defect and edge sites of graphene play an important role in the reaction, leading to nitrogen atoms incorporated into the lattice of carbon. When temperatures were lower than 600 °C the nitrogen atoms displaced oxygen groups and formed nitrogen function groups, and when temperatures were higher than 600 °C and ~ 4 at.% carbon atoms and part of oxygen function groups reacted with NH 3 . When compared to pure activated carbon, the nitrogen doped activated carbon shows nearly four times the capacitance (191 vs 51 F/g). - Highlights: • The nitrogen content up to 10.43 at % during CAC pyrolysis under NH3 at 800 °C. • The oxygen groups and carbon atoms played an important role in the nitrogen doping. • NAC-600 shows a much higher specific capacitance than CAC.

  3. Synthesis of Au@Ag core-shell nanocubes containing varying shaped cores and their localized surface plasmon resonances.

    Science.gov (United States)

    Gong, Jianxiao; Zhou, Fei; Li, Zhiyuan; Tang, Zhiyong

    2012-06-19

    We have synthesized Au@Ag core-shell nanocubes containing Au cores with varying shapes and sizes through modified seed-mediated methods. Bromide ions are found to be crucial in the epitaxial growth of Ag atoms onto Au cores and in the formation of the shell's cubic shape. The Au@Ag core-shell nanocubes exhibit very abundant and distinct localized surface plasmon resonance (LSPR) properties, which are core-shape and size-dependent. With the help of theoretical calculation, the physical origin and the resonance mode profile of each LSPR peak are identified and studied. The core-shell nanocrystals with varying shaped cores offer a new rich category for LSPR control through the plasmonic coupling effect between core and shell materials.

  4. Is it possible to embed a 4D, N=4 supersymmetric vector multiplet within a completely off-shell adinkra hologram?

    Energy Technology Data Exchange (ETDEWEB)

    Calkins, Mathew; Gates, D.E.A.; Gates, Sylvester James Jr.; McPeak, Brian [Center for String and Particle Theory, Department of Physics, University of Maryland,College Park, MD 20742-4111 (United States)

    2014-05-13

    We present evidence of the existence of a 1D, N = 16 SUSY hologram that can be used to understand representation theory aspects of a 4D, N = 4 supersymmetrical vector multiplet. In this context, the long-standing “off-shell SUSY” problem for the 4D, N = 4 Maxwell supermultiplet is precisely formulated as a problem in linear algebra.

  5. Many-particle and many-hole states in neutron-rich Ne isotopes related to broken N=20 shell closure

    International Nuclear Information System (INIS)

    Kimura, Masaaki; Horiuchi, Hisashi

    2004-01-01

    The low-lying level structures of 26 Ne, 28 Ne and 30 Ne which are related to the breaking of the N=20 shell closure have been studied in the framework of the deformed-basis anti-symmetrized molecular dynamics plus generator coordinate method using the Gogny D1S force. The properties of the many-particle and many-hole states are studied as well as that of the ground band. We predict that the negative-parity states, in which neutrons are promoted into the pf-orbit from the sd orbit, have a small excitation energy in the cases of 28 Ne and 30 Ne. We regard this to be a typical phenomena accompanying the breaking of the N=20 shell closure. It is also found that the neutron 4p4h structure of 30 Ne appears at low excitation energy, which contains α + 16 O correlations. (author)

  6. Nuclear shell effects in neutron-rich nuclei around N=20 and N=32,34

    CERN Document Server

    Seidlitz, M

    Nuclear shell effects in neutron-rich nuclei around N=20 and N=32,34 were studied by means of reduced transition probabilities, i.e. B(E2) and B(M1) values. To this end a series of Coulomb-excitation experiments, employing radioactive 31Mg and 29,30Na beams, as well as a precise lifetime experiment of excited states in 56Cr were performed. The collective properties of excited states of 31Mg were the subject of a Coulomb-excitation experiment at REX-ISOLDE, CERN, employing a radioactive 31Mg beam at a beam energy of 3.0 MeV/u. The beam intensity amounted to 3000 ions/s on average. The highly efficient MINIBALL setup was employed, consisting of eight HPGe cluster detectors for gamma-ray detection and a segmented Si-detector for coincident particle detection. The level scheme of 31Mg was extended. Spin and parity assignment of the observed 945 keV state yielded 5/2+ and its de-excitation is dominated by a strong collective M1 transition. Comparison of the transition probabilities of 30,31,32Mg establishes that f...

  7. Algebraic theory of Stark-Zeeman dynamic effect in hydrogen-like atom

    International Nuclear Information System (INIS)

    Fursa, D.V.; Yudin, G.L.

    1990-01-01

    The problems of calculating time evolution operator within the given n-shell (here n is main quantum number) for the hydrogen atom located in non-stationary electric and magnetic fields is under investigation. Making use of the Fock SO(4) group reduces this problem to the set of problems with linear realization of the dynamic symmetry group for which the evolution operator is the operator of corresponding groups representation. The types of evolution operator parametrization in the form of exponents product (the Wei-Norman method) any by means of D-functions connected with Euler angles and Cayley-Klein parameters are discussed. It is shown that the problem of evolution operator calculation can be reduced to investigation of a pair of two-level systems. 35 refs

  8. Theoretical study of inner-shell ionization by heavy-particle impact

    International Nuclear Information System (INIS)

    Sarkadi, L.

    2000-01-01

    Complete text of publication follows. In our previous theoretical studies of inner-shell ionization of atoms by heavy-particle impact we applied the so-called coupled-states model. This theory was constructed to account for the intra-shell coupling effects in L-shell ionization. The model satisfactory reproduced the main tendencies of the measured L-shell ionization data (cross sections, L 3 -subshell alignment parameters) in a broad range of the collision energy, target and projectile atomic number. However, the accuracy of these calculations was uncertain, because the coupled-states model contained a series of approximation. The most questionable assumption was that the changes of the cross sections due to the subshell coupling effects were expressed by correction factors. The correction factors were derived considering only some representative transitions between the bound and continuum states, namely transitions into states of energy E f = 0 and angular momentum l f = 0.1. As a first step to improve the coupled-states model, a computer program was developed to calculate the matrix elements of the Coulomb interaction between a charged particle and an atomic electron, ∫ ψ* f (r) /R - r/ -1 ψ i (r)dr, for arbitrary final state energy E f and angular momentum l f . The ψ k (r)'s are non-relativistic hydrogenic wave functions. The program consists of subroutines that compute matrix elements between eigenstates of both the total angular momentum j, and the orbital angular momentum l. As further output quantities, the radial components of the multipole series expansion of the matrix elements (the so-called G functions) can be obtained, as well. The structure of the program is such that the hydrogenic wave functions can be replaced by arbitrary one-electron wave functions. The program was tested in calculations of K-, L- and M-shell ionization probabilities and cross sections within the framework of the straight-line version of the (first-order) semiclassical

  9. Inner-shell electron spectroscopy for microanalysis

    International Nuclear Information System (INIS)

    Joy, D.C.; Maher, D.M.

    1979-01-01

    The transmission electron energy-loss spectrum shows characteristic edges corresponding to the excitation of inner-shell electrons of atoms in a thin sample. Analysis of these edges provides detailed chemical, structural, and electronic data from the radiated volume. By combining electron spectroscopy and electron microscopy, this microanalytical technique can be performed in conjunction with high-resolution imaging of the sample. It is shown that this approach has advantages of sensitivity, spatial resolution, and convenience over other comparable techniques. 7 figures

  10. Improving p-type doping efficiency in Al0.83Ga0.17N alloy substituted by nanoscale (AlN)5/(GaN)1 superlattice with MgGa-ON δ-codoping: Role of O-atom in GaN monolayer

    Science.gov (United States)

    Zhong, Hong-xia; Shi, Jun-jie; Zhang, Min; Jiang, Xin-he; Huang, Pu; Ding, Yi-min

    2015-01-01

    We calculate Mg-acceptor activation energy EA and investigate the influence of O-atom, occupied the Mg nearest-neighbor, on EA in nanoscale (AlN)5/(GaN)1 superlattice (SL), a substitution for Al0.83Ga0.17N disorder alloy, using first-principles calculations. We find that the N-atom bonded with Ga-atom is more easily substituted by O-atom and nMgGa-ON (n = 1-3) complexes are favorable and stable in the SL. The O-atom plays a dominant role in reducing EA. The shorter the Mg-O bond is, the smaller the EA is. The Mg-acceptor activation energy can be reduced significantly by nMgGa-ON δ-codoping. Our calculated EA for 2MgGa-ON is 0.21 eV, and can be further reduced to 0.13 eV for 3MgGa-ON, which results in a high hole concentration in the order of 1020 cm-3 at room temperature in (AlN)5/(GaN)1 SL. Our results prove that nMgGa-ON (n = 2,3) δ-codoping in AlN/GaN SL with ultrathin GaN-layer is an effective way to improve p-type doping efficiency in Al-rich AlGaN.

  11. Improving p-type doping efficiency in Al0.83Ga0.17N alloy substituted by nanoscale (AlN5/(GaN1 superlattice with MgGa-ON δ-codoping: Role of O-atom in GaN monolayer

    Directory of Open Access Journals (Sweden)

    Hong-xia Zhong

    2015-01-01

    Full Text Available We calculate Mg-acceptor activation energy EA and investigate the influence of O-atom, occupied the Mg nearest-neighbor, on EA in nanoscale (AlN5/(GaN1 superlattice (SL, a substitution for Al0.83Ga0.17N disorder alloy, using first-principles calculations. We find that the N-atom bonded with Ga-atom is more easily substituted by O-atom and nMgGa-ON (n = 1-3 complexes are favorable and stable in the SL. The O-atom plays a dominant role in reducing EA. The shorter the Mg-O bond is, the smaller the EA is. The Mg-acceptor activation energy can be reduced significantly by nMgGa-ON δ-codoping. Our calculated EA for 2MgGa-ON is 0.21 eV, and can be further reduced to 0.13 eV for 3MgGa-ON, which results in a high hole concentration in the order of 1020 cm−3 at room temperature in (AlN5/(GaN1 SL. Our results prove that nMgGa-ON (n = 2,3 δ-codoping in AlN/GaN SL with ultrathin GaN-layer is an effective way to improve p-type doping efficiency in Al-rich AlGaN.

  12. Nano-engineering of three-dimensional core/shell nanotube arrays for high performance supercapacitors

    Science.gov (United States)

    Grote, Fabian; Wen, Liaoyong; Lei, Yong

    2014-06-01

    Large-scale arrays of core/shell nanostructures are highly desirable to enhance the performance of supercapacitors. Here we demonstrate an innovative template-based fabrication technique with high structural controllability, which is capable of synthesizing well-ordered three-dimensional arrays of SnO2/MnO2 core/shell nanotubes for electrochemical energy storage in supercapacitor applications. The SnO2 core is fabricated by atomic layer deposition and provides a highly electrical conductive matrix. Subsequently a thin MnO2 shell is coated by electrochemical deposition onto the SnO2 core, which guarantees a short ion diffusion length within the shell. The core/shell structure shows an excellent electrochemical performance with a high specific capacitance of 910 F g-1 at 1 A g-1 and a good rate capability of remaining 217 F g-1 at 50 A g-1. These results shall pave the way to realize aqueous based asymmetric supercapacitors with high specific power and high specific energy.

  13. Atomic Structure of Au−Pd Bimetallic Alloyed Nanoparticles

    KAUST Repository

    Ding, Yong; Fan, Fengru; Tian, Zhongqun; Wang, Zhong Lin

    2010-01-01

    shell of the NPs was systematically investigated by high-resolution transmission electron microscopy. In the NPs coated with a single atomic layer of Pd, the strain between the surface Pd layer and the Au core is released by Shockley partial dislocations

  14. Recent shell-model results for exotic nuclei

    Directory of Open Access Journals (Sweden)

    Utsuno Yusuke

    2014-03-01

    Full Text Available We report on our recent advancement in the shell model and its applications to exotic nuclei, focusing on the shell evolution and large-scale calculations with the Monte Carlo shell model (MCSM. First, we test the validity of the monopole-based universal interaction (VMU as a shell-model interaction by performing large-scale shell-model calculations in two different mass regions using effective interactions which partly comprise VMU. Those calculations are successful and provide a deeper insight into the shell evolution beyond the single-particle model, in particular showing that the evolution of the spin-orbit splitting due to the tensor force plays a decisive role in the structure of the neutron-rich N ∼ 28 region and antimony isotopes. Next, we give a brief overview of recent developments in MCSM, and show that it is applicable to exotic nuclei that involve many valence orbits. As an example of its applications to exotic nuclei, shape coexistence in 32Mg is examined.

  15. Annual progress report for atomic and nuclear research with accelerators and fusion related atomic physics. Reporting period, October 1, 1974--September 30, 1975

    International Nuclear Information System (INIS)

    1975-10-01

    Topics covered include: laboratory operation and development; atomic collision cross sections in gases; ionization cross sections in thin solid materials; experimental impact-parameter dependent probabilities for k-shell vacancy production by fast heavy-ion projectiles; x-ray spectroscopy with high energy ions; atomic lifetime measurements; polarization studies of ion-induced x rays; theoretical spectra in ion-induced reactions; theoretical atomic cross section calculations; search for heavy-ion resonances; lifetimes of low energy states in 21 Ne; nuclear scattering and reactions; and trace element analysis

  16. High-resolution measurements of x rays from ion-atom collisions

    International Nuclear Information System (INIS)

    Knudson, A.R.

    1974-01-01

    High resolution measurements of K x-ray spectra produced by ion-atom collisions at MeV energies are presented. These measurements indicate that a distribution of L-shell vacancies accompanies K-shell excitation. The variation of these spectra as a function of incident ion energy and atomic number is discussed. Difficulties in the analysis of these spectra due to rearrangement of vacancies between the time of the collision and the time of x-ray emission are considered. The use of high resolution x-ray measurements to obtain information on projectile ion vacancy configurations is demonstrated by data for Ar ions in KCl. X-ray spectra from Al projectiles in a variety of targets were measured and the effect of target composition on these spectra is discussed

  17. K-shell ionization probability in energetic nearly symmetric heavy-ion collisions

    International Nuclear Information System (INIS)

    Tserruya, I.; Schmidt-Boecking, H.; Schuch, R.

    1977-01-01

    Impact parameter dependent K-x-ray emission probabilities for the projectile and target atoms have been measured in 35 MeV Cl on Cl, Cl on Ti and Cl on Ni collisions. The sum of projectile plus target K-shell ionization probability is taken as a measure of the total 2psigma ionization probability. The 2pπ-2psigma totational coupling model is in clear disagreement with the present results. On the other hand the sum of probabilities is reproduced both in shape and absolute magnitude by the statistical model for inner-shell ionization. The K-shell ionization probability of the higher -Z collision partner is well described by this model including the 2psigma-1ssigma vacancy sharing probability calculated as a function of the impact parameter. (author)

  18. Constructing theoretical M-shell spectra for Mg-like Au through Cl-like Au ions in gold plasma diagnostics

    International Nuclear Information System (INIS)

    Hamasha, Safeia; Alshaiub, Rania

    2012-01-01

    The theoretical atomic structure and spectra data for electric dipole transitions in six gold ions (Au 67+ through Au 62+ ) are produced using the flexible atomic code (FAC). The produced data contain energy levels, radiative transition rates and oscillator strengths with Δn≠0 (n = 3 → 4, 5, 6, 7). All M-shell strong lines for the six gold ions are also identified. The produced data and constructed spectra revealed the presence of a wide variety of ionization stages of Au with several blended spectral lines in the spectral range (1.7-4.4 Å). Calculated energy levels are compared against published values, which were calculated using the multi-reference many body perturbation theory that includes higher order quantum electrodynamics corrections effects. Favorable agreement with <0.26% difference was observed.

  19. Effects of N2 mixed gas atomization on electrochemical properties of Mm(Ni,Co,Mn,Al)5.0 alloy powder

    International Nuclear Information System (INIS)

    Yanagimoto, K.; Sunada, S.; Majima, K.; Sawada, T.

    2004-01-01

    N 2 gas, N 2 -Ar mixed gas and Ar gas atomization followed by acid surface treatment was applied to improve electrochemical properties of AB 5 type hydrogen storage alloy powder. The shape of Ar atomized powder was spherical and it changed to be irregular with increasing N 2 content of mixed gas. Irrespective of gas kinds, electrodes of atomized powder showed the same discharge capacity as cast-pulverized powder under auxiliary electrical conductivity by nickel powder addition. Without nickel powder, however, N 2 atomized powder showed the best electrochemical properties as well as gas activation behavior. By the combination process of N 2 gas atomization and acid surface treatment, it was considered that irregular shape of N 2 atomized powder promoted electrical conductivity of electrodes and catalytic nickel concentrated surface layer was formed to increase the hydrogen storage rapidity

  20. One-step synthesis of shell/core structural boron and nitrogen co-doped graphitic carbon/nanodiamond as efficient electrocatalyst for the oxygen reduction reaction in alkaline media

    International Nuclear Information System (INIS)

    Liu, Xiaoxu; Wang, Yanhui; Dong, Liang; Chen, Xi; Xin, Guoxiang; Zhang, Yan; Zang, Jianbing

    2016-01-01

    Shell/core structural boron and nitrogen co-doped graphitic carbon/nanodiamond (BN-C/ND) non-noble metal catalyst has been synthesized by a simple one-step heat-treatment of the mixture with nanodiamond, melamine, boric acid and FeCl 3 . In the process of the surface graphitization of nanodiamond with catalysis by FeCl 3 , B and N atoms from the decomposition of boric acid and melamine were directly introduced into the graphite lattice to form B, N co-doped graphitic carbon shell, while the core still retained the diamond structure. Electrochemical measurements of the BN-C/ND catalyst show much higher electrocatalytic activities towards oxygen reduction reaction (ORR) in alkaline medium than its analogues doped with B or N alone (B-C/ND or N-C/ND). The high catalytic activity of BN-C/ND is attributed to the synergetic effect caused by co-doping of C/ND with B and N. Meanwhile, the BN-C/ND exhibits an excellent electrochemical stability due to the special shell/core structure. There is almost no alteration occurred in the cyclic voltammetry measurements for BN-C/ND before and after 5000 cycles. All experimental results prove that the BN-C/ND may be exploited as a potentially efficient and inexpensive non-noble metal cathode catalyst for ORR to substitute Pt-based catalysts in fuel cells.

  1. Evolution in time of an N-atom system. II. Calculation of the eigenstates

    International Nuclear Information System (INIS)

    Rudolph, Terry; Yavin, Itay; Freedhoff, Helen

    2004-01-01

    We calculate the energy eigenvalues and eigenstates corresponding to coherent single and multiple excitations of a number of different arrays of N identical two-level atoms (TLA's) or qubits, including polygons, 'diamond' structures, polygon multilayers, icosahedra, and dodecahedra. We assume only that the coupling occurs via an exchange interaction which depends on the separation between the atoms. We include the interactions between all pairs of atoms, and our results are valid for arbitrary separations relative to the radiation wavelength

  2. Determination of interstitial oxygen atom position in U2N3+xOy by near edge structure study

    Science.gov (United States)

    Jiang, A. K.; Zhao, Y. W.; Long, Z.; Hu, Y.; Wang, X. F.; Yang, R. L.; Bao, H. L.; Zeng, R. G.; Liu, K. Z.

    2018-06-01

    The determination of interstitial oxygen atom site in U2N3+xOy film could facilitate the understanding of the oxidation mechanism of α-U2N3 and the effect of U2N3+xOy on anti-oxidation. By comparing the similarities and variances between N K edge and O K edge electron energy loss spectra (EELS) for oxidized α-U2N3 and UO2, the present work looks at the local structure of nitrogen and oxygen atoms in U2N3+xOy film, identifying the most possible position of interstitial O atom.

  3. Tailoring Ruthenium Exposure to Enhance the Performance of fcc Platinum@Ruthenium Core-Shell Electrocatalysts in the Oxygen Evolution Reaction

    KAUST Repository

    AlYami, Noktan

    2016-05-17

    The catalytic properties of noble metal nanocrystals are a function of their size, structure, and surface composition. In particular, achieving high activity without sacrificing stability is essential for designing commercially viable catalysts. A major challenge in designing state-of-the-art Ru-based catalysts for the oxygen evolution reaction (OER), which is a key step in water splitting, is the poor stability and surface tailorability of these catalysts. In this study, we designed rapidly synthesizable size-controlled, morphology-selective, and surface-tailored platinum-ruthenium core-shell (Pt@Ru) and alloy (PtRu) nanocatalysts in a scalable continuous-flow reactor. These core-shell nanoparticles with atomically precise shells were produced in a single synthetic step with carbon monoxide as the reducing agent. By varying the metal precursor concentration, a dendritic or layer-by-layer ruthenium shell can be grown. The catalytic activities of the synthesized Pt@Ru and PtRu nanoparticles exhibit noticeably higher electrocatalytic activity in the OER compared to that of pure Pt and Ru nanoparticles. Promisingly, Pt@Ru nanocrystals with a ~2-3 atomic layer Ru cuboctahedral shell surpass conventional Ru nanoparticles in terms of both durability and activity.

  4. Tailoring Ruthenium Exposure to Enhance the Performance of fcc Platinum@Ruthenium Core-Shell Electrocatalysts in the Oxygen Evolution Reaction

    KAUST Repository

    AlYami, Noktan; LaGrow, Alec P.; Joya, khurram; Hwang, Jinyeon; Katsiev, Khabiboulakh; Anjum, Dalaver H.; Losovyj, Yaroslav; Sinatra, Lutfan; Kim, Jin Young; Bakr, Osman

    2016-01-01

    The catalytic properties of noble metal nanocrystals are a function of their size, structure, and surface composition. In particular, achieving high activity without sacrificing stability is essential for designing commercially viable catalysts. A major challenge in designing state-of-the-art Ru-based catalysts for the oxygen evolution reaction (OER), which is a key step in water splitting, is the poor stability and surface tailorability of these catalysts. In this study, we designed rapidly synthesizable size-controlled, morphology-selective, and surface-tailored platinum-ruthenium core-shell (Pt@Ru) and alloy (PtRu) nanocatalysts in a scalable continuous-flow reactor. These core-shell nanoparticles with atomically precise shells were produced in a single synthetic step with carbon monoxide as the reducing agent. By varying the metal precursor concentration, a dendritic or layer-by-layer ruthenium shell can be grown. The catalytic activities of the synthesized Pt@Ru and PtRu nanoparticles exhibit noticeably higher electrocatalytic activity in the OER compared to that of pure Pt and Ru nanoparticles. Promisingly, Pt@Ru nanocrystals with a ~2-3 atomic layer Ru cuboctahedral shell surpass conventional Ru nanoparticles in terms of both durability and activity.

  5. Magnetic properties of Ni/Au core/shell studied by Monte Carlo simulations

    Energy Technology Data Exchange (ETDEWEB)

    Masrour, R., E-mail: rachidmasrour@hotmail.com [Laboratory of Materials, Processes, Environment and Quality, Cady Ayyed University, National School of Applied Sciences, Sidi Bouzid, Safi, 63 4600 (Morocco); LMPHE (URAC 12), Faculté des Sciences, Université Mohammed V-Agdal, Av. Ibn Batouta, B.P. 1014, Rabat (Morocco); Bahmad, L. [LMPHE (URAC 12), Faculté des Sciences, Université Mohammed V-Agdal, Av. Ibn Batouta, B.P. 1014, Rabat (Morocco); Hamedoun, M. [Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco); Benyoussef, A. [LMPHE (URAC 12), Faculté des Sciences, Université Mohammed V-Agdal, Av. Ibn Batouta, B.P. 1014, Rabat (Morocco); Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco); Hassan II Academy of Science and Technology, Rabat (Morocco); Hlil, E.K. [Institut Néel, CNRS et Université Joseph Fourier, BP 166, F-38042 Grenoble cedex 9 (France)

    2014-01-10

    The magnetic properties of ferromagnetic Ni/Au core/shell have been studied using Monte Carlo simulations within the Ising model framework. The considered Hamiltonian includes the exchange interactions between Ni–Ni, Au–Au and Ni–Au and the external magnetic field. The thermal total magnetizations and total magnetic susceptibilities of core/shell Ni/Au are computed. The critical temperature is deduced. The exchange interaction between Ni and Au atoms is obtained. In addition, the total magnetizations versus the external magnetic field and crystal filed for different temperature are also established.

  6. Status and problems of multiply ionized atom spectroscopy

    International Nuclear Information System (INIS)

    Kononov, Eh.Ya.; Ryabtsev, A.N.

    1984-01-01

    Principal directions of investigations associated with identification of spectral lines and with determination of energy structure of high multiplicity ions are analyzed. The considered part of atomic spectroscopy is developed both in the direction of obtaining high multiplicity ion spectra and interpretation of spectral details associated with excitation conditions and in the direction of detailed study on compound energy structures of electron shells. Spectroscopy with fast ion beams is widely developed. Accumulated atomic data, developed methods of atomic calculations and improvement of observation technique permit to realize complex spectroscopic diagnostics in astrophysics and hot plasma physics

  7. Experimental approach towards shell structure at 100Sn and 78Ni

    International Nuclear Information System (INIS)

    Grawe, H.; Gorska, M.; Fahlander, C.

    2000-07-01

    The status of experimental approach to 100 Sn and 78 Ni is reviewed. Revised single particle energies for neutrons are deduced for the N=Z=50 shell closure and evidence for low lying I π =2 + and 3 - states is presented. Moderate E2 polarisation charges of 0.1 e and 0.6 e are found to reproduce the experimental data when core excitation of 100 Sn is properly accounted for in the shell model. For the neutron rich Ni region no conclusive evidence for a N=40 subshell is found, whereas firm evidence for the persistence of the N=50 shell at 78 Ni is inferred from the existence of seniority isomers. The disappearance of this isomerism in the mid νg 9/2 shell is discussed. (orig.)

  8. ''Atomic'' Bremsstrahlung or polarizational radiation in collision of many-electron ions

    International Nuclear Information System (INIS)

    Amusia, M.Ya.; Solov'yov, A.V.

    1991-01-01

    In this work the so-called ''Atomic'' bremsstrahlung (AB) or polarizational radiation, created in collisions of atoms or ions, is discussed. This kind of radiation arises due to the polarization of the electron shell of colliding particles. It is created by the structured projectiles and targets if the constituents are electrically charged. 6 refs, 2 figs

  9. M-shell ionization of heavy elements by 0.1-1.0 MeV/amu 1,2H and 3,4He ions

    International Nuclear Information System (INIS)

    Pajek, M.; Banas, D.; Braziewicz, J.; Czarnota, M.; Bienkowski, A.; Jaskola, M.; Korman, A.; Trautmann, D.; Lapicki, G.

    2006-01-01

    The M-shell ionization in high-Z atoms by low-energy light 1 1 H, 1 2 H, 2 3 He, and 2 4 He ions have been studied systematically in the energy range 0.1-1.0 MeV/amu in order to verify the available theoretical approaches describing the M-shell ionization by charged particles in asymmetric collisions. The present low-energy data, combined with our earlier results reported for M-shell ionization by hydrogen and helium ions for higher energies, form a systematic experimental basis to test the theoretical predictions of M-shell ionization based on the plane-wave Born approximation (PWBA), the semiclassical approximation (SCA), and the binary-encounter approximation (BEA). In the PWBA based approaches the energy loss (E), Coulomb deflection (C), perturbed stationary state (PSS), and relativistic (R) effects were considered within the ECPSSR theory and its recent modification, called the ECUSAR theory, in which a description of the PSS effect was corrected to account for the united- and separated-atom (USA) electron binding energy limits. In the SCA calculations with relativistic wave functions the binding effect was included only in the limiting cases of separated-atom and united-atom limits. Possible contribution of the electron capture, multiple ionization, and recoil ionization to the M-shell vacancy production, which is dominated for light ions impact by direct single ionization process, are also discussed. The universal scaling of measured M-shell x-ray production and ionization cross sections was investigated in detail. Using the present data the isotopic effect has been studied by comparing the measured M-shell ionization cross-section ratios for equal-velocity hydrogen 1 1 H and 1 2 H as well as helium 2 3 He and 2 4 He isotopes. In addition, the ratios of measured ionization cross sections for 1 2 H and 2 4 He were used to investigate the role of the binding effect. The present results are of practical importance for the application of particle-induced x

  10. Nuclear charge radii of the 1fsub(7/2) shell nuclei from muonic atoms

    International Nuclear Information System (INIS)

    Wohlfahrt, H.D.

    1979-01-01

    Muonic X-ray of medium-weight nuclei have been performed in recent years by the Los Alamos muonic X-ray group, using the high intensity muon beam available at the LAMPF 800 MeV proton accelerator. These studies, which together include all stable 1fsub(7/2) neutron shell nuclei, provide information about the proton core polarization due to the successive addition of neutrons for the proton cores Z = 20 (Ca), 22 (Ti), 24(Cr), 26(Fe) and 28(Ni). In addition, these studies, which represent the first systematic investigations of isotone shifts, provide the opportunity to compare the core polarization caused by protons with core polarization caused by neutrons in the same (1fsub(7/2)) shell. (KBE)

  11. Mechanism for radiative recombination and defect properties of GaP/GaNP core/shell nanowires

    International Nuclear Information System (INIS)

    Dobrovolsky, A.; Stehr, J. E.; Chen, S. L.; Chen, W. M.; Buyanova, I. A.; Kuang, Y. J.; Sukrittanon, S.; Tu, C. W.

    2012-01-01

    Recombination processes in GaP/GaNP core/shell nanowires (NWs) grown on a Si substrate by molecular beam epitaxy are examined using a variety of optical characterization techniques, including cw- and time-resolved photoluminescence and optically detected magnetic resonance (ODMR). Superior optical quality of the structures is demonstrated based on the observation of intense emission from a single NW at room temperature. This emission is shown to originate from radiative transitions within N-related localized states. From ODMR, growth of GaP/GaNP NWs is also found to facilitate formation of complex defects containing a P atom at its core that act as centers of competing non-radiative recombination.

  12. Experimental Confirmation of CH Mandrel Removal from Be Shells

    International Nuclear Information System (INIS)

    Cook, B; Letts, S; Buckley, S

    2004-01-01

    Sputtered Be shells are made by sputter deposition of Be, with a radially graded Cu dopant as necessary, onto plastic mandrels supplied by General Atomics. Although the plastic mandrel may not be a design issue, it is a fielding issue because at cryo temperatures the plastic shrinks more than the Be and delaminates. We described in previous memos a proposed method for thermally removing the plastic by burning it in air at elevated temperature. A key aspect to this process is getting air in and out of the shell through the small diameter hole that must be laser drilled in the capsule wall to serve as a fill hole for the fuel. Because the hole is quite small, gas flow through the orifice must be forced, and an external pressure variation was suggested to do this. Further calculations showed that since the volume of the capsule is quite small and the amount of plastic in the shell by comparison is large, the ''pumping'' of air in and out of the shell must occur at least once per minute in order to supply enough O 2 to completely burn the plastic to CO 2 and H 2 O in a reasonable time. Such an apparatus has been now built and this memo details both its construction and operation, as well as provides the first evidence of plastic mandrel removal from Be shells

  13. Shell Venster

    International Nuclear Information System (INIS)

    De Wit, P.; Looijesteijn, B.; Regeer, B.; Stip, B.

    1995-03-01

    In the bi-monthly issues of 'Shell Venster' (window on Shell) attention is paid to the activities of the multinational petroleum company Shell Nederland and the Koninklijke/Shell Groep by means of non-specialist articles

  14. Closing of Coster-Kronig transitions in multiply ionised gold atoms

    International Nuclear Information System (INIS)

    Banas, D.; Braziewicz, J.; Czarnota, M.; Fijal, I.; Jaskola, M.; Korman, A.; Kretschmer, W.; Pajek, M.; Semaniak, J.

    2003-01-01

    The paper discusses the effect of closing of L- and M-shell Coster-Kronig (CK) transitions in multiply ionised Au atoms, for which the selected CK transitions become energetically forbidden. This effect plays an important role when the Coster-Kronig energy for single-hole configuration is relatively low, being comparable with a change of the electronic binding energies in multiply ionised atom. We show, by using a simplified model, that for gold the effect of closing of CK transitions occurs for strong L 1 -L 3 M 4,5 transition for the L 1 -subshell as well as the M 3 -M 5 N 6,7 and M 4 -M 5 O 3,4 CK transitions for the M 3 - and M 4 -subshell, respectively. We demonstrate that the discussed effect of closing CK transitions substantially changes the X-ray fluorescence and Coster-Kronig yields and thus has to be considered in interpretation of X-rays excited by heavy ion impact

  15. An off-shell superspace reformulation of D = 4, N = 4 super-Yang-Mills theory

    Energy Technology Data Exchange (ETDEWEB)

    Cederwall, Martin [Division for Theoretical Physics, Department of Physics, Chalmers University of Technology, Gothenburg (Sweden)

    2018-01-15

    D = 4, N = 4 super-Yang-Mills theory has an off-shell superspace formulation in terms of pure spinor superfields, which is directly inherited from the D = 10 theory. That superspace, in particular the choice of pure spinor variables, is less suitable for dealing with fields that are inherently 4-dimensional, such as the superfields based on the scalars, which are gauge-covariant, and traces of powers of scalars, which are gauge-invariant. We give a reformulation of D = 4, N = 4 super-Yang-Mills theory in N = 4 superspace, using inherently 4-dimensional pure spinors. All local degrees of freedom reside in a superfield based on the physical scalars. The formalism should be suited for calculations of correlators of traces of scalar superfields. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  16. Emulsion preparation for novel micro-porous polymeric hemi-shells

    CSIR Research Space (South Africa)

    Naidoo, Kersch

    2008-01-01

    Full Text Available -dichloromethane (DCM) oil phase , micro-porous hemi-shells formed as solvent evaporated. CO2 gas ) 252–254 www.elsevier.com/locate/matlet Polycaprolactone hemi-shells were prepared by using an O/W technique. PCL (15% w/v) was fully dissolved in 10ml DCM (oil 253K...-averaged particle size and hemi-shell yield with solvent evaporation time. (ImageJ, NIH), the number-average particle size and yield of hemi-shells were obtained with increasing time intervals (n=200). Scanning electron microscopy (LEO 1525 field emis- sion SEM...

  17. Compressed shell conditions extracted from spectroscopic analysis of Ti K-shell absorption spectra with evaluation of line self-emission

    Energy Technology Data Exchange (ETDEWEB)

    Johns, H. M.; Mancini, R. C.; Hakel, P.; Nagayama, T. [Physics Department, University of Nevada, Reno, 1664 N. Virginia St., Reno, Nevada 89557 (United States); Smalyuk, V. A.; Regan, S. P.; Delettrez, J. [Laboratory for Laser Energetics, University of Rochester, 250 E. River Road, Rochester, New York 14623 (United States)

    2014-08-15

    Ti-doped tracer layers embedded in the shell at varying distances from the fuel-shell interface serve as a spectroscopic diagnostic for direct-drive experiments conducted at OMEGA. Detailed modeling of Ti K-shell absorption spectra produced in the tracer layer considers n = 1–2 transitions in F- through Li-like Ti ions in the 4400–4800 eV range, both including and excluding line self-emission. Testing the model on synthetic spectra generated from 1-D LILAC hydrodynamic simulations reveals that the model including self-emission best reproduces the simulation, while the model excluding self-emission overestimates electron temperature T{sub e} and density N{sub e} to a higher degree for layers closer to the core. The prediction of the simulation that the magnitude of T{sub e} and duration of Ti absorption will be strongly tied to the distance of the layer from the core is consistent with the idea that regions of the shell close to the core are more significantly heated by thermal transport out of the hot dense core, but more distant regions are less affected by it. The simulation predicts more time variation in the observed T{sub e}, N{sub e} conditions in the compressed shell than is observed in the experiment, analysis of which reveals conditions remain in the range T{sub e} = 400–600 eV and N{sub e} = 3.0–10.0 × 10{sup 24} cm{sup −3} for all but the most distant Ti-doped layer, with error bars ∼5% T{sub e} value and ∼10% N{sub e} on average. The T{sub e}, N{sub e} conditions of the simulation lead to a greater degree of ionization for zones close to the core than occurs experimentally, and less ionization for zones far from the core.

  18. Effect of plasma oscillations of C60 collectivized electrons on photoionization of endohedral noble-gas atoms

    International Nuclear Information System (INIS)

    Amusia, M. Ya.; Baltenkov, A. S.

    2006-01-01

    It is demonstrated that outer and inner electron shells, including that formed by collectivized electrons of the fullerene C 60 , affects dramatically the cross section of the subvalent ns subshells of the noble-gas endohedral atoms A-C 60 . The calculations are performed within the framework of a very simple, so-called ''orange skin,'' model that makes it possible, in spite of its simplicity, to take into account the modification of the ns subshell due to its interaction with inner and outer atomic shells, as well as with the collectivized electrons of the C 60 . As a concrete example, we consider the Xe 5s electrons completely collectivized by the powerful action of the Xe close and remote multielectron neighboring shells

  19. Highly stable supercapacitors with conducting polymer core-shell electrodes for energy storage applications

    KAUST Repository

    Xia, Chuan; Chen, Wei; Wang, Xianbin; Hedhili, Mohamed N.; Wei, Nini; Alshareef, Husam N.

    2015-01-01

    commercial application. Here, the development of nanostructured PAni-RuO2 core-shell arrays as electrodes for highly stable pseudocapacitors with excellent energy storage performance is reported. A thin layer of RuO2 grown by atomic layer deposition (ALD

  20. Structural and magnetic properties of CoO-Pt core-shell nanoparticles

    Czech Academy of Sciences Publication Activity Database

    Zeleňáková, A.; Zeleňák, V.; Michalik, Štefan; Kováč, J.; Meisel, M. W.

    2014-01-01

    Roč. 89, č. 10 (2014), "104417-1"-"104417-10" ISSN 1098-0121 Institutional support: RVO:68378271 Keywords : CoO-Pt core shell nanoparticles * superparamagnetism * superspin glass state * x-ray diffraction * x-ray absorption spectroscopy Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 3.736, year: 2014

  1. Pion-nucleon vertex function with an off-shell nucleon

    International Nuclear Information System (INIS)

    Nutt, W.T.; Shakin, C.M.

    1977-01-01

    A model calculation for the π-N vertex function is presented in the case in which there is a single off-mass-shell nucleon and a (nearly) on-mass-shell pion. Very strong effects due to the P 11 resonance at 1470 MeV are found. A simple parametrization of the vertex function is prvided in the case that at least one nucleon is on its mass shell. (Auth.)

  2. Nitrogen-doped porous carbon from Camellia oleifera shells with enhanced electrochemical performance

    Energy Technology Data Exchange (ETDEWEB)

    Zhai, Yunbo, E-mail: ybzhai@hnu.edu.cn [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control, Hunan University, Ministry of Education, Changsha 410082 (China); Xu, Bibo [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control, Hunan University, Ministry of Education, Changsha 410082 (China); Zhu, Yun [Office of Scientific R& D, Hunan University, Changsha 410082 (China); Qing, Renpeng; Peng, Chuan; Wang, Tengfei; Li, Caiting; Zeng, Guangming [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control, Hunan University, Ministry of Education, Changsha 410082 (China)

    2016-04-01

    Nitrogen doped porous activated carbon was prepared by annealing treatment of Camellia oleifera shell activated carbon under NH{sub 3}. We found that nitrogen content of activated carbon up to 10.43 at.% when annealed in NH{sub 3} at 800 °C. At 600 °C or above, the N-doped carbon further reacts with NH{sub 3}, leads to a low surface area down to 458 m{sup 2}/g and low graphitization degree. X-ray photoelectron spectroscope (XPS) analysis indicated that the nitrogen functional groups on the nitrogen-doped activated carbons (NACs) were mostly in the form of pyridinic nitrogen. We discovered that the oxygen groups and carbon atoms at the defect and edge sites of graphene play an important role in the reaction, leading to nitrogen atoms incorporated into the lattice of carbon. When temperatures were lower than 600 °C the nitrogen atoms displaced oxygen groups and formed nitrogen function groups, and when temperatures were higher than 600 °C and ~ 4 at.% carbon atoms and part of oxygen function groups reacted with NH{sub 3}. When compared to pure activated carbon, the nitrogen doped activated carbon shows nearly four times the capacitance (191 vs 51 F/g). - Highlights: • The nitrogen content up to 10.43 at % during CAC pyrolysis under NH3 at 800 °C. • The oxygen groups and carbon atoms played an important role in the nitrogen doping. • NAC-600 shows a much higher specific capacitance than CAC.

  3. A low temperature investigation of the gas-phase N(2D) + NO reaction. Towards a viable source of N(2D) atoms for kinetic studies in astrochemistry.

    Science.gov (United States)

    Nuñez-Reyes, Dianailys; Hickson, Kevin M

    2018-06-18

    The gas-phase reaction of metastable atomic nitrogen N(2D) with nitric oxide has been investigated over the 296-50 K temperature range using a supersonic flow reactor. As N(2D) could not be produced photolytically in the present work, these excited state atoms were generated instead through the C(3P) + NO → N(2D) + CO reaction while C(3P) atoms were created in situ by the 266 nm pulsed laser photolysis of CBr4 precursor molecules. The kinetics of N(2D) atoms were followed on-resonance by vacuum ultraviolet laser induced fluorescence at 116.7 nm. The measured rate constants for the N(2D) + NO reaction are in excellent agreement with most of the earlier work at room temperature and represent the only available kinetic data for this process below 296 K. The rate constants are seen to increase slightly as the temperature falls to 100 K with a more substantial increase at even lower temperature; a finding which is not reproduced by theoretical work. The prospects for using this chemical source of N(2D) atoms in future studies of a wide range of N(2D) atom reactions are discussed.

  4. Molecular effects in carbon K-shell Auger-electron production by 0.6-2.0 MeV protons and extraction of an atomic cross section

    International Nuclear Information System (INIS)

    McDaniel, F.D.; Lapicki, G.

    1987-01-01

    Carbon K-shell Auger-electron production cross sections are reported for 0.6-2.0 MeV protons incident on CH 4 (methane), C 2 H 2 (acetylene), C 2 H 4 (ethylene), C 2 H 6 (ethane), n-C 4 H 10 (normal butane), i-C 4 H 10 (isobutane), C 6 H 6 (benzene), CO (carbon monoxide), and CO 2 (carbon dioxide). A constant-energy mode 45 0 parallel-plate electrostatic analyzer was used for detection of Auger electrons. The carbon KLL Auger-electron cross sections for all molecules were found to be lower than that found for CH 4 by 9-23%. All carbon KLL Auger-electron data could be brought into agreement when corrected for the chemical shift of the carbon K-shell binding energy in molecules and for intramolecular scattering. KLL Auger-electron production cross sections are compared to first Born and ECPSSR theories and show good agreement with both after the chemical shift of the carbon K-shell binding energy in molecules and the effects of intramolecular scattering are considered. (orig.)

  5. Shells of Nerita gastropod bio-monitors of heavy metals pollution around the Indian Ocean

    International Nuclear Information System (INIS)

    Badran, M.I.

    1999-01-01

    Minor and heavy metals Mg, Sr, Mn, Fe and Zn were measured in individual shells of four different Nerita species collected from Phuket Island, Thailand. Shell weight and crystallography were also recorded. Heavy metal concentrations were poorly correlated with both shell weight and crystallography. Out of the four species, N. albicilla acquired the highest heavy metal concentrations. Subsequently shells of N. albicilla collected from different sites around the Indian Ocean were compared for their metal concentrations. Shells of industrial sites in Kenya and India had significantly higher heavy metal concentrations than shells from pristine sites in Mauritius and Aldabra. Discussing the factors that may affect the shell metal concentration, the variations encountered herein are best attributed to the ambient bio-available metal concentration. (author)

  6. Laser ablation of Au-CuO core-shell nanocomposite in water for optoelectronic devices

    Science.gov (United States)

    Ismail, Raid A.; Abdul-Hamed, Ryam S.

    2017-12-01

    Core-shell gold-copper oxide Au-CuO nanocomposites were synthesized using laser ablation of CuO target in colloidal solution of Au nanoparticles (NPs). The effect of laser fluence on the structural, morphological, electrical, and optical properties of Au-CuO nanocomposites was investigated using x-ray diffraction (XRD), atomic force microscope (AFM), scanning electron microscope (SEM), transmission electron microscope (TEM), photoluminescence (PL), Fourier transformed infrared spectroscopy (FTIR), Hall measurement, and UV-vis spectroscopy. X-ray diffraction results confirm the formation of polycrystalline Au-CuO NPs with monoclinic structure. The optical energy gap for CuO was 4 eV and for the Au-CuO core-shell nanocomposites was found to be in the range of 3.4-3.7 eV. SEM and TEM investigations revealed that the structure and morphology of Au-CuO core-shell nanocomposites were strongly depending on the laser fluence. A formation of Au-CuO nanospheres and platelets structures was observed. The photoluminescence data showed an emission of broad visible peaks between 407 and 420 nm. The effect of laser fluence on the dark and illuminated I-V characteristics of Au-CuO/n-Si heterojunction photodetectors was investigated and analyzed. The experimental data demonstrated that the photodetector prepared at optimum laser fluence exhibited photosensitivity of 0.6 AW-1 at 800 nm.

  7. An Eocene orthocone from Antarctica shows convergent evolution of internally shelled cephalopods

    Science.gov (United States)

    Bengtson, Stefan; Reguero, Marcelo A.; Mörs, Thomas

    2017-01-01

    Background The Subclass Coleoidea (Class Cephalopoda) accommodates the diverse present-day internally shelled cephalopod mollusks (Spirula, Sepia and octopuses, squids, Vampyroteuthis) and also extinct internally shelled cephalopods. Recent Spirula represents a unique coleoid retaining shell structures, a narrow marginal siphuncle and globular protoconch that signify the ancestry of the subclass Coleoidea from the Paleozoic subclass Bactritoidea. This hypothesis has been recently supported by newly recorded diverse bactritoid-like coleoids from the Carboniferous of the USA, but prior to this study no fossil cephalopod indicative of an endochochleate branch with an origin independent from subclass Bactritoidea has been reported. Methodology/Principal findings Two orthoconic conchs were recovered from the Early Eocene of Seymour Island at the tip of the Antarctic Peninsula, Antarctica. They have loosely mineralized organic-rich chitin-compatible microlaminated shell walls and broadly expanded central siphuncles. The morphological, ultrustructural and chemical data were determined and characterized through comparisons with extant and extinct taxa using Scanning Electron Microscopy/Energy Dispersive Spectrometry (SEM/EDS). Conclusions/Significance Our study presents the first evidence for an evolutionary lineage of internally shelled cephalopods with independent origin from Bactritoidea/Coleoidea, indicating convergent evolution with the subclass Coleoidea. A new subclass Paracoleoidea Doguzhaeva n. subcl. is established for accommodation of orthoconic cephalopods with the internal shell associated with a broadly expanded central siphuncle. Antarcticerida Doguzhaeva n. ord., Antarcticeratidae Doguzhaeva n. fam., Antarcticeras nordenskjoeldi Doguzhaeva n. gen., n. sp. are described within the subclass Paracoleoidea. The analysis of organic-rich shell preservation of A. nordenskjoeldi by use of SEM/EDS techniques revealed fossilization of hyposeptal cameral soft tissues

  8. Cascade of negative muons in atoms

    International Nuclear Information System (INIS)

    Akylas, V.R.

    1978-01-01

    A study is made of the evolution of a negative muon captured in an atom and the formalism of energy loss associated with the muonic atom. The principal goals are to calculate reliability the muon x-ray intensities, given the initial population of the muonic orbits, to invert the problem and deduce the initial distribution from the x-ray intensities, to provide a reasonably simple and convenient tool to correlate observations, and finally, to systematize some questions of theoretical interest. The early part of the history of the muon in matter, including the atomic capture and classical phase of the atomic cascade are reviewed. In the quantal treatment of the transition rates, both radiative and electron Auger transitions are considered. In general, multipolarities up to E3 and K, L, and M electronic shells are fully investigated. Multipole radiation is treated in the conventinal way and pesents no special problems. Magnetic type transitions between states with different principal quantum numbers are shown to be small. Auger electron ejection rates are more complicated and several approximations have been adopted. The basic results have been computed in terms of elemetary functions. In the Auger transitions we have shown that magnetic multipoles can be safety neglected. The relative sizes of the rates corresponding to different multipoles are systematically studied. A comparison of results is made with atomic photoelectric effect data and with the nuclear internal conversion coefficients. A general agreement is found, except around shell thresholds. The existing data of muonic x-ray intensities in iron and thallium are analyzed in a systematic way. It is found that for Fe the initial l-distribution is almost flat, whereas that for T1 is weighted towards the high l values, sharper than statistical. As a result of the investigations and in order to make our findings usable, a computer program has been developed. 36 references

  9. Fabrication of a transparent ultraviolet detector by using n-type Ga2O3 and p-type Ga-doped SnO2 core-shell nanowires.

    Science.gov (United States)

    Hsu, Cheng-Liang; Lu, Ying-Ching

    2012-09-21

    This study investigates the feasibility of synthesizing high-density transparent Ga(2)O(3)/SnO(2):Ga core-shell nanowires on a sapphire substrate at 1000 °C by VLS. The doping Ga concentrations are 0.46, 1.07, 2.30 and 17.53 atomic%. The XRD spectrum and HR-TEM reveal Ga(2)O(3) and SnO(2) as having monoclinic and tetragonal rutile structures, respectively. Experimental results indicate that the XRD peak shift of SnO(2) to a larger angle increases with the increasing amount of Ga doping. According to the CL spectrum, SnO(2) and Ga(2)O(3) peak at approximately 528-568 nm and 422-424 nm, respectively. The maximum quantum efficiency of Ga(2)O(3)/SnO(2):Ga core-shell nanowires is around 0.362%. The UV light on-off current contrast ratio of Ga(2)O(3)/SnO(2):Ga core-shell nanowires is around 1066.7 at a bias of 5 V. Moreover, the dynamic response of Ga(2)O(3)/SnO(2):Ga core-shell nanowires has an on-off current contrast ratio of around 16. Furthermore, the Ga(2)O(3) region functions similar to a capacitor and continues to accumulate SnO(2):Ga excited electrons under UV light exposure.

  10. Microstructure of InxGa1−xN nanorods grown by molecular beam epitaxy

    International Nuclear Information System (INIS)

    Webster, R F; Soundararajah, Q Y; Griffiths, I J; Cherns, D; Novikov, S V; Foxon, C T

    2015-01-01

    Transmission electron microscopy is used to examine the structure and composition of In x Ga 1−x N nanorods grown by plasma-assisted molecular beam epitaxy. The results confirm a core–shell structure with an In-rich core and In-poor shell resulting from axial and lateral growth sectors respectively. Atomic resolution mapping by energy-dispersive x-ray microanalysis and high angle annular dark field imaging show that both the core and the shell are decomposed into Ga-rich and In-rich platelets parallel to their respective growth surfaces. It is argued that platelet formation occurs at the surfaces, through the lateral expansion of surface steps. Studies of nanorods with graded composition show that decomposition ceases for x ≥ 0.8 and the ratio of growth rates, shell:core, decreases with increasing In concentration. (paper)

  11. Site-resolved imaging of a bosonic Mott insulator using ytterbium atoms

    Science.gov (United States)

    Miranda, Martin; Inoue, Ryotaro; Tambo, Naoki; Kozuma, Mikio

    2017-10-01

    We demonstrate site-resolved imaging of a strongly correlated quantum system without relying on laser cooling techniques during fluorescence imaging. We observe the formation of Mott shells in the insulating regime and realize thermometry in an atomic cloud. This work proves the feasibility of the noncooled approach and opens the door to extending the detection technology to new atomic species.

  12. Importance-truncated shell model for multi-shell valence spaces

    Energy Technology Data Exchange (ETDEWEB)

    Stumpf, Christina; Vobig, Klaus; Roth, Robert [Institut fuer Kernphysik, TU Darmstadt (Germany)

    2016-07-01

    The valence-space shell model is one of the work horses in nuclear structure theory. In traditional applications, shell-model calculations are carried out using effective interactions constructed in a phenomenological framework for rather small valence spaces, typically spanned by one major shell. We improve on this traditional approach addressing two main aspects. First, we use new effective interactions derived in an ab initio approach and, thus, establish a connection to the underlying nuclear interaction providing access to single- and multi-shell valence spaces. Second, we extend the shell model to larger valence spaces by applying an importance-truncation scheme based on a perturbative importance measure. In this way, we reduce the model space to the relevant basis states for the description of a few target eigenstates and solve the eigenvalue problem in this physics-driven truncated model space. In particular multi-shell valence spaces are not tractable otherwise. We combine the importance-truncated shell model with refined extrapolation schemes to approximately recover the exact result. We present first results obtained in the importance-truncated shell model with the newly derived ab initio effective interactions for multi-shell valence spaces, e.g., the sdpf shell.

  13. Precision mass measurements with ISOLTRAP to study the evolution of the $\\textit{N}$=82 shell gap far from stability

    CERN Multimedia

    Shell effects and their evolution across the nuclear chart impose important constraints on the modelling of the nucleon-nucleon interaction. The strength of shell closures in neutron-rich nuclei also influences the path of the $\\textit{r}$-process of nucleo-synthesis and the predicted elemental abundances. We propose to measure the masses of the isotopes $^{132,133}$In, $^{129-132}$Cd, $^{125-129}$Ag with the Penning-trap mass spectrometer ISOLTRAP. The recently developed multi-reflection time-of-flight mass separator of ISOLTRAP will allow, as a beam purifier, to handle higher contamination ratios than before and, for the more exotic cases, to directly determine the mass of the nuclides of interest. The masses of the proposed isotopes will allow the investigation of a possible weakening of the $\\textit{N}$ = 82 shell gap for $\\textit{Z}$ < 50 and corresponding $\\textit{r}$-process waiting point. This in turn enables an exploration of the impact on the $\\textit{A}$ = 130 $\\textit{r}$-process abundances.

  14. Pathological behavior of the open-shell restricted self-consistent-field equations

    International Nuclear Information System (INIS)

    Moscardo, F.; Alvarez-Collado, J.R.

    1979-01-01

    The possible solutions of open-shell restricted self-consistent-field equations for a doublet are studied for Li and Na atoms, according to the values of the parameters implied in those equations. A similar behavior, characterized by the presence of several variational solutions is observed in both atoms. Some of these solutions can be assigned to excited configurations. Excitation energies are in good agreement with experimental data. Doublet stability for the solutions obtained has been studied, discussing the saddle-point character present in those solutions associated to excited configurations

  15. Pathological behavior of the open-shell restricted self-consistent-field equations

    Energy Technology Data Exchange (ETDEWEB)

    Moscardo, F.; Alvarez-Collado, J.R.

    1979-02-01

    The possible solutions of open-shell restricted self-consistent-field equations for a doublet are studied for Li and Na atoms, according to the values of the parameters implied in those equations. A similar behavior, characterized by the presence of several variational solutions is observed in both atoms. Some of these solutions can be assigned to excited configurations. Excitation energies are in good agreement with experimental data. Doublet stability for the solutions obtained has been studied, discussing the saddle-point character present in those solutions associated to excited configurations.

  16. Phase Transition of Poly(acrylic acid-co-N-isopropylacrylamide) Core-shell Nanogels

    Science.gov (United States)

    Liu, Xiao-bing; Zhou, Jian-feng; Ye, Xiao-dong

    2012-08-01

    A series of poly(acrylic acid) macromolecular chain transfer agents with different molecular weights were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization and characterized by 1H NMR and gel permeation chromatography. Multiresponsive core-shell nanogels were prepared by dispersion polymerization of N-isopropylacrylamide in water using these poly(potassium acrylate) macro-RAFT agents as the electrosteric stabilizer. The size of the nanogels decreases with the amount of the macro-RAFT agent, indicating that the surface area occupied by per polyelectrolyte group is a critical parameter for stabilizing the nanogels. The volume phase transition and the zeta potentials of the nanogels in aqueous solutions were studied by dynamic light scattering and zetasizer analyzer, respectively.

  17. Expansion of X-ray form factor for close shell using uncorrelated wave function

    Energy Technology Data Exchange (ETDEWEB)

    AL-Robayi, Enas M. [Babylon University , College of Science for Women, laser Physics Department, Hilla (Iraq)

    2013-12-16

    The atomic scattering factor has been studied for Be+ve, and B+2ve ions using the uncorrelated wave function (Hartree-Fock (HF)) for inter particle electronic shells. The physical importance of this factor appears in its relation to several important atomic properties as, the coherent scattering intensity, the total scattering intensity, the incoherent scattering function, the coherent scattering cross section, the total incoherent cross section, the nuclear magnetic shielding constant, the geometrical structure factor. Also there is one atomic properties the one particle radial density distribution function D(r)has been studied using the partitioning technique.

  18. One particle-hole excitations in p- and fp-shell nuclei

    International Nuclear Information System (INIS)

    Hees, A.G.M. van.

    1982-01-01

    Results are presented of shell model calculations of medium and light atomic nuclei. The influence of the allowance of one particle-hole excitations is investigated. This enables improved descriptions of intermediate mass nuclei in the fp-shell. For light p-shell nuclei one particle-hole excitations create exclusively situations with abnormal parity. The description of situations with normal parity is not changed by enlarging the model space. In the first chapter shell-model calculations are performed on the light Ni-isotopes (A = 57-59). One nucleon is allowed to be excited from the fsub(7/2) orbit to one of the other fp-shell orbits. The general observation in the enlarged model space is that one can use operators that require a much weaker 'renormalization' and the calculation requires only a selected set of matrix elements of the Hamiltonian. An additional advantage of the inclusion of one particle-hole excitations is that it allows a description of several intruder states, i.e. states that cannot be produced with the assumption of a closed 56 Ni core. In the second chapter the nuclei with mass number A = 52-55, i.e. a small number of holes in the 56 Ni core, are investigated similarly. In the third chapter much lighter nuclei (A = 4-16) are discussed. For a theoretical description of nonnormal-parity states one has to admit the excitation of at least one nucleon to a higher harmonic-oscillator major-shell. (Auth.)

  19. Measurements of K shell absorption jump factors and jump ratios using EDXRF technique

    Science.gov (United States)

    Kacal, Mustafa Recep; Han, İbrahim; Akman, Ferdi

    2015-04-01

    In the present work, the K-shell absorption jump factors and jump ratios for 30 elements between Ti ( Z = 22) and Er ( Z = 68) were measured by energy dispersive X-ray fluorescence (EDXRF) technique. The jump factors and jump ratios for these elements were determined by measuring the K shell fluorescence parameters such as the Kα X-ray production cross-sections, K shell fluorescence yields, Kβ-to- Kα X-rays intensity ratios, total atomic absorption cross sections and mass attenuation coefficients. The measurements were performed using an Am-241 radioactive point source and a Si (Li) detector in direct excitation and transmission experimental geometry. The results for jump factors and jump ratios were compared with theoretically calculated and the ones available in the literature.

  20. Electronic structure of single- and multiple-shell carbon fullerenes

    International Nuclear Information System (INIS)

    Lin, Y.; Nori, F.

    1994-01-01

    We study the electronic states of giant single-shell and the recently discovered nested multiple-shell carbon fullerenes within the tight-binding approximation. We use two different approaches, one based on iterations and the other on symmetry, to obtain the π-state energy spectra of large fullerene cages: C 240 , C 540 , C 960 , C 1500 , C 2160 , and C 2940 . Our iteration technique reduces the size of the problem by more than one order of magnitude (factors of ∼12 and 20), while the symmetry-based approach reduces it by a factor of 10. We also find formulas for the highest occupied and lowest unoccupied molecular orbital energies of C 60n 2 fullerenes as a function of n, demonstrating a tendency towards a metallic regime for increasing n. For multiple-shell fullerenes, we analytically obtain the eigenvalues of the intershell interaction

  1. p-Cu2O-shell/n-TiO2-nanowire-core heterostucture photodiodes

    Directory of Open Access Journals (Sweden)

    Hsueh Ting-Jen

    2011-01-01

    Full Text Available Abstract This study reports the deposition of cuprous oxide [Cu2O] onto titanium dioxide [TiO2] nanowires [NWs] prepared on TiO2/glass templates. The average length and average diameter of these thermally oxidized and evaporated TiO2 NWs are 0.1 to 0.4 μm and 30 to 100 nm, respectively. The deposited Cu2O fills gaps between the TiO2 NWs with good step coverage to form nanoshells surrounding the TiO2 cores. The p-Cu2O/n-TiO2 NW heterostructure exhibits a rectifying behavior with a sharp turn-on at approximately 0.9 V. Furthermore, the fabricated p-Cu2O-shell/n-TiO2-nanowire-core photodiodes exhibit reasonably large photocurrent-to-dark-current contrast ratios and fast responses.

  2. Intracapsular implant rupture: MR findings of incomplete shell collapse.

    Science.gov (United States)

    Soo, M S; Kornguth, P J; Walsh, R; Elenberger, C; Georgiade, G S; DeLong, D; Spritzer, C E

    1997-01-01

    The objective of this study was to determine the frequency and significance of the MR findings of incomplete shell collapse for detecting implant rupture in a series of surgically removed breast prostheses. MR images of 86 breast implants in 44 patients were studied retrospectively and correlated with surgical findings at explantation. MR findings included (a) complete shell collapse (linguine sign), 21 implants; (b) incomplete shell collapse (subcapsular line sign, teardrop sign, and keyhole sign), 33 implants; (c) radial folds, 31 implants; and (d) normal, 1 implant. The subcapsular line sign was seen in 26 implants, the teardrop sign was seen in 27 implants, and the keyhole sign was seen in 23 implants. At surgery, 48 implants were found to be ruptured and 38 were intact. The MR findings of ruptured implants showed signs of incomplete collapse in 52% (n = 25), linguine sign in 44% (n = 21), and radial folds in 4% (n = 2). The linguine sign perfectly predicted implant rupture, but sensitivity was low. Findings of incomplete shell collapse improved sensitivity and negative predictive values, and the subcapsular line sign produced a significant incremental increase in predictive ability. MRI signs of incomplete shell collapse were more common than the linguine sign in ruptured implants and are significant contributors to the high sensitivity and negative predictive values of MRI for evaluating implant integrity.

  3. Simple and convenient preparation of Au-Pt core-shell nanoparticles on surface via a seed growth method

    International Nuclear Information System (INIS)

    Qian Lei; Sha Yufang; Yang Xiurong

    2006-01-01

    Au-Pt core-shell nanoparticles were prepared on glass surface by a seed growth method. Gold nanoparticles were used as seeds and ascorbic acid-H 2 PtCl 6 solutions as growth solutions to deposit Pt shell on the surface of gold nanoparticles. These core-shell nanoparticles and their growth process were examined by UV-Vis spectroscopy, X-ray photoelectron spectroscopy, atomic force microscopy and field-emission environmental scanning electron microscopy and the results indicated that the deposition speed was fast and nanoparticles with obvious core-shell structure could be obtained after 2 min. Moreover, this seed growth method for preparation of the core-shell nanoparticles is simple and convenient compared with other seed growth methods with NH 4 OH as a mild reductant. In addition, electrochemical experiments indicated that these Au-Pt core-shell nanoparticles had similar electrochemical properties to those of the bulk Pt electrode

  4. MicroShell Minimalist Shell for Xilinx Microprocessors

    Science.gov (United States)

    Werne, Thomas A.

    2011-01-01

    MicroShell is a lightweight shell environment for engineers and software developers working with embedded microprocessors in Xilinx FPGAs. (MicroShell has also been successfully ported to run on ARM Cortex-M1 microprocessors in Actel ProASIC3 FPGAs, but without project-integration support.) Micro Shell decreases the time spent performing initial tests of field-programmable gate array (FPGA) designs, simplifies running customizable one-time-only experiments, and provides a familiar-feeling command-line interface. The program comes with a collection of useful functions and enables the designer to add an unlimited number of custom commands, which are callable from the command-line. The commands are parameterizable (using the C-based command-line parameter idiom), so the designer can use one function to exercise hardware with different values. Also, since many hardware peripherals instantiated in FPGAs have reasonably simple register-mapped I/O interfaces, the engineer can edit and view hardware parameter settings at any time without stopping the processor. MicroShell comes with a set of support scripts that interface seamlessly with Xilinx's EDK tool. Adding an instance of MicroShell to a project is as simple as marking a check box in a library configuration dialog box and specifying a software project directory. The support scripts then examine the hardware design, build design-specific functions, conditionally include processor-specific functions, and complete the compilation process. For code-size constrained designs, most of the stock functionality can be excluded from the compiled library. When all of the configurable options are removed from the binary, MicroShell has an unoptimized memory footprint of about 4.8 kB and a size-optimized footprint of about 2.3 kB. Since MicroShell allows unfettered access to all processor-accessible memory locations, it is possible to perform live patching on a running system. This can be useful, for instance, if a bug is

  5. Ultrafine Sn nanoparticles embedded in shell of N-doped hollow carbon spheres as high rate anode for lithium-ion batteries

    Energy Technology Data Exchange (ETDEWEB)

    Dou, Peng; Cao, Zhenzhen; Wang, Chao; Zheng, Jiao [School of Materials Science and Engineering, Tianjin University, Tianjin 300072 (China); Xu, Xinhua, E-mail: xhxutju@gmail.com [School of Materials Science and Engineering, Tianjin University, Tianjin 300072 (China); Tianjin Key Laboratory of Composite and Functional Materials, Tianjin 300072 (China)

    2017-05-15

    Highlights: • Dynamic covalent bond in polymeric nanoparticles is used to induce hollow Sn{sup 4+}-MOPs. • Ultrafine Sn nanoparticles uniformly embedded in shell of N-doped hollow carbon spheres is successfully synthesized by pyrolysis of the Sn{sup 4+}-MOPs precursor. • The composite exhibits superior cycle stability and rate capacity. - Abstract: A novel reversible interaction in polymeric nanoparticles is used to induce hollow Sn{sup 4+}-MOPs. Then ultrafine Sn nanoparticles uniformly embedded in shell of N-doped hollow carbon spheres is successfully synthesized by pyrolysis of the Sn{sup 4+}-MOPs precursor. In this architecture, the N-doped carbon shells can effectively avoid the direct exposure of embedded Sn nanoparticles to the electrolyte and efficiently accommodate the volume change of Sn nanoparticles. Furthermore, the hollow structure of carbon sphere can prevent Sn nanoparticles aggregation over repeated cycling and shorten the diffusion path of both electrons and ions. As a consequence, this N-doped hollow Sn/C anode delivers a reversible capacity of 606 mA h g{sup −1} at a current density of 0.2 A g{sup −1} after 250 cycles and a reversible capacity of 221 mA h g{sup −1} even at a much higher current density of 10 A g{sup −1}, which are much better than those of pure Sn nanoparticles. The desirable cyclic stability and rate capability were attributed to the unique architecture that provided fast pathway for electron transport and simultaneously solved the major issues of Sn-based anodes, such as pulverization, aggregation and loss of electrical contact.

  6. Transient atomic behavior and surface kinetics of GaN

    International Nuclear Information System (INIS)

    Moseley, Michael; Billingsley, Daniel; Henderson, Walter; Trybus, Elaissa; Doolittle, W. Alan

    2009-01-01

    An in-depth model for the transient behavior of metal atoms adsorbed on the surface of GaN is developed. This model is developed by qualitatively analyzing transient reflection high energy electron diffraction (RHEED) signals, which were recorded for a variety of growth conditions of GaN grown by molecular-beam epitaxy (MBE) using metal-modulated epitaxy (MME). Details such as the initial desorption of a nitrogen adlayer and the formation of the Ga monolayer, bilayer, and droplets are monitored using RHEED and related to Ga flux and shutter cycles. The suggested model increases the understanding of the surface kinetics of GaN, provides an indirect method of monitoring the kinetic evolution of these surfaces, and introduces a novel method of in situ growth rate determination.

  7. Transient atomic behavior and surface kinetics of GaN

    Science.gov (United States)

    Moseley, Michael; Billingsley, Daniel; Henderson, Walter; Trybus, Elaissa; Doolittle, W. Alan

    2009-07-01

    An in-depth model for the transient behavior of metal atoms adsorbed on the surface of GaN is developed. This model is developed by qualitatively analyzing transient reflection high energy electron diffraction (RHEED) signals, which were recorded for a variety of growth conditions of GaN grown by molecular-beam epitaxy (MBE) using metal-modulated epitaxy (MME). Details such as the initial desorption of a nitrogen adlayer and the formation of the Ga monolayer, bilayer, and droplets are monitored using RHEED and related to Ga flux and shutter cycles. The suggested model increases the understanding of the surface kinetics of GaN, provides an indirect method of monitoring the kinetic evolution of these surfaces, and introduces a novel method of in situ growth rate determination.

  8. Multiple ionization produced in Yb due to N-,Si- and Ti-ion impact

    International Nuclear Information System (INIS)

    Verma, P.

    2000-01-01

    Heavy ion induced inner shell ionization produces multiple vacancies in the outer shells (M, N etc.) simultaneous to vacancies in the inner-shells (viz. L-shell), which in turn create a very complicated electronic configuration. Three projectiles N 2+,3+ , Si 7+,8+ and Ti 10+,11+ ion beams having a range of 0.3 to 3.5 MeV/u were bombarded on a thin rare earth target of Yb. The recorded L X-ray spectra of Yb have been analyzed in the light of multiple ionization produced due to the heavy ion impact. The outer-shell vacancies acting as spectator vacancies cause a shift in the energy of the various L X-ray diagram lines. A comparison of the shifts in the energies of the various L X-ray transitions of Yb due to the impact of these projectiles, from standard values and that due to proton impact along with the deviation of the intensity ratios from single hole branching ratios, reveal a dependence of multiple ionization on the projectile atomic number (Z) and energy. A further comparison of the degree of multiple ionization produced in Yb, evident by the number of spectator vacancies produced due to the impact of projectiles with 7≤Z≤22 and overlapping MeV/u range lead to explicit conclusions regarding the probability of multiple vacancy production in outer shells simultaneous to a single L-shell vacancy for such projectile target combinations. (orig.)

  9. Percolation approach for atomic and molecular cluster formation

    International Nuclear Information System (INIS)

    Knospe, O.; Seifert, G.

    1987-12-01

    We apply a percolation approach for the theoretical analysis of mass spectra of molecular microclusters obtained by adiabatic expansion technique. The evolution of the shape of the experimental size distributions as function of stagnation pressure and stagnation temperature are theoretically reproduced by varying the percolation parameter. Remaining discrepancies between theory and experiment are discussed. In addition, the even-odd alternation as well as the 'magic' shell structure within metallic, secondary ion mass spectra are investigated by introducing statistical weights for the cluster formation probabilities. Shell correction energies of atomic clusters as function of cluster-size are deduced from the experimental data. (orig.)

  10. Shell model estimate of electric dipole moments in medium and heavy nuclei

    Directory of Open Access Journals (Sweden)

    Teruya Eri

    2015-01-01

    Full Text Available Existence of the electric dipole moment (EDM is deeply related with time-reversal invariance. The EDMof a diamagnetic atom is mainly induced by the nuclear Schiff moment. After carrying out the shell model calculations to obtain wavefunctions for Xe isotopes, we evaluate nuclear Schiff moments for Xe isotopes to estimate their atomic EDMs. We estimate the contribution from each single particle orbital for the Schiff moment. It is found that the contribution on the Schiff moment is very different from orbital to orbital.

  11. Change of Cr atoms distribution in Fe85Cr15 alloy caused by 250 keV He+ ion irradiation to different doses

    International Nuclear Information System (INIS)

    Dubiel, S.M.; Żukrowski, J.

    2015-01-01

    Highlights: • Effect of He-ion irradiation dose on Fe 85 Cr 15 alloy. • Irradiation-induced clustering of Cr atoms. • Irradiation-caused reorientation of the surface magnetization vector. • Irradiation-caused increase of Fe-site spin-density. - Abstract: Redistribution of Cr atoms in a Fe 85 Cr 15 alloy caused by its irradiation with 250 keV He + ions to different doses, D = 8 ⋅ 10 16 , 16 ⋅ 10 16 and 48 ⋅ 10 16 ions/cm 2 was investigated by means of conversion electrons Mössbauer spectroscopy. The redistribution was expressed in terms of the Warren–Cowley short-range order parameters α 1 , α 2 and α 12 pertaining to the first (1NN), second (2NN) and both i.e. 1NN + 2NN shells, respectively. Clear evidence was found, both for non-irradiated and irradiated samples that the actual distribution of Cr atoms is characteristic of the shell, and for a given shell it depends on the irradiation dose. In particular, α 1 is positive, hence indicates an under population of Cr atoms in 1NN with respect to the random case, α 2 is negative, giving evidence thereby that 2NN is overpopulated by Cr atoms, and α 12 is weakly positive. Under the applied irradiation the number of Cr atoms in both neighbor shells decreased signifying thereby a clustering of Cr atoms. The underlying decrease of Cr concentration within the 1NN–2NN volume around the probe Fe atoms was estimated at 1.5 at.% ranging between 2.1 for the lowest and 0.8 at.% for the highest dose

  12. Radiative capture reactions and spectroscopy of multipolar anions in the framework of Gamow Shell Model

    International Nuclear Information System (INIS)

    Fossez, Kevin

    2014-01-01

    Small open quantum systems, whose properties are profoundly affected by the environment of continuum states, are intensely studied in various fields of Physics: nuclear physics, atomic and molecular physics, quantum optics, etc. These different many-body systems, in spite of their specific features, have generic properties which are common to all weakly bound or unbound systems close to the threshold. Coupling to the continuum is essential to describe the low-energy nuclear reactions of astrophysical interest, the formation of halo states in nuclei, atomic clusters and dipolar anions, or the near-threshold two neutron and alpha particle correlations (clustering). Recently, the open quantum system extension of the nuclear shell model, the Gamow shell model (GSM), based on the Berggren ensemble, has been applied successfully for the description of resonant states spectra in atomic nuclei. The coupled-channel formulation of the GSM (GSM-CC) allows to describe various low-energy nuclear reactions. In this work, the GSM-CC is formulated and applied for the description of proton/neutron radiative capture reactions of astrophysical interest, such as: 17 F(p, γ) 18 Ne, 7 Be(p, γ) 8 B and 7 Li(n, γ) 8 Li. Moreover, for the first time, the GSM has been applied in atomic physics for the description of spectra of dipolar anions. Systematic investigation of the hydrogen cyanide dipolar anion (HCN - ) allowed to identify the collective bands of states both in the strong coupling regime, for weakly bound halo states, and in the weak coupling regime above the dissociation threshold. In the strong coupling regime, K J = 0 anion a rotational band has been found. Above the threshold, K J quantum number is not conserved. Resonances in this regime form rotational bands according to the angular momentum of the rotating molecule, whereas the band head energies and the lifetimes depend predominantly on the external electron wave function. (author) [fr

  13. Starting SCF Calculations by Superposition of Atomic Densities

    NARCIS (Netherlands)

    van Lenthe, J.H.; Zwaans, R.; van Dam, H.J.J.; Guest, M.F.

    2006-01-01

    We describe the procedure to start an SCF calculation of the general type from a sum of atomic electron densities, as implemented in GAMESS-UK. Although the procedure is well-known for closed-shell calculations and was already suggested when the Direct SCF procedure was proposed, the general

  14. Graphitic carbon nitride nanosheet@metal-organic framework core-shell nanoparticles for photo-chemo combination therapy

    Science.gov (United States)

    Chen, Rui; Zhang, Jinfeng; Wang, Yu; Chen, Xianfeng; Zapien, J. Antonio; Lee, Chun-Sing

    2015-10-01

    Recently, nanoscale metal-organic frameworks (NMOFs) have started to be developed as a promising platform for bioimaging and drug delivery. On the other hand, combination therapies using multiple approaches are demonstrated to achieve much enhanced efficacy. Herein, we report, for the first time, core-shell nanoparticles consisting of a photodynamic therapeutic (PDT) agent and a MOF shell while simultaneously carrying a chemotherapeutic drug for effective combination therapy. In this work, core-shell nanoparticles of zeolitic-imadazolate framework-8 (ZIF-8) as shell embedded with graphitic carbon nitride (g-C3N4) nanosheets as core are fabricated by growing ZIF-8 in the presence of g-C3N4 nanosheets. Doxorubicin hydrochloride (DOX) is then loaded into the ZIF-8 shell of the core-shell nanoparticles. The combination of the chemotherapeutic effects of DOX and the PDT effect of g-C3N4 nanosheets can lead to considerably enhanced efficacy. Furthermore, the red fluorescence of DOX and the blue fluorescence of g-C3N4 nanosheets provide the additional function of dual-color imaging for monitoring the drug release process.Recently, nanoscale metal-organic frameworks (NMOFs) have started to be developed as a promising platform for bioimaging and drug delivery. On the other hand, combination therapies using multiple approaches are demonstrated to achieve much enhanced efficacy. Herein, we report, for the first time, core-shell nanoparticles consisting of a photodynamic therapeutic (PDT) agent and a MOF shell while simultaneously carrying a chemotherapeutic drug for effective combination therapy. In this work, core-shell nanoparticles of zeolitic-imadazolate framework-8 (ZIF-8) as shell embedded with graphitic carbon nitride (g-C3N4) nanosheets as core are fabricated by growing ZIF-8 in the presence of g-C3N4 nanosheets. Doxorubicin hydrochloride (DOX) is then loaded into the ZIF-8 shell of the core-shell nanoparticles. The combination of the chemotherapeutic effects of DOX

  15. Muonic atom-light nucleus interaction

    International Nuclear Information System (INIS)

    Kuz'michev, V.E.; Peresypkin, V.V.; Efetov, A.V.

    1991-01-01

    The effective potential of the interaction between light nucleus and two-particle atom at distances greater than its Bohr radius is obtained in the analytic form on the basis of a correct account of three Coulomb particle problem. Features of the interaction between p, t, 4 He, 7 Be nuclei and mesonic atoms μp, μt, μ 4 He and μ 7 Be, that arising from the differences in masses and charges of interacting particles, are studied. The corresponding potentials in the pre-threshold energy range are given. The coefficients of the symptotic formula for the effective are calculated in adiabatic approximation and with regard for the main off-shell corrections. 16 refs.; 4 figs

  16. Kinetic analysis of interaction between N atoms and O-covered Ru(0001)

    International Nuclear Information System (INIS)

    Kang, Kai; Kleyn, A. W.; Gleeson, M. A.

    2015-01-01

    Eley-Rideal (ER) reactions involving neutral atoms heavier than hydrogen reacting with adsorbed atoms of similar mass were first observed in recent molecular beam experiments by Zaharia et al. [Phys. Rev. Lett. 113, 053201 (2014)]. Through analysis of two types of measurements, they obtained different estimations for the N–O ER reaction cross section, one of which is unexpectedly high. This was qualitatively accounted for by invoking a secondary effect whereby the presence of N adatoms on the surface acted to “shield” O adatoms from prompt recombinative desorption. We apply a rate equation model that includes two ER processes involving different adsorbed species (N–O ad and N–N ad ) and an N-adsorption process to the full-beam exposure subset of the experimental data in order to study the reaction kinetics. Values for the individual reaction cross sections are derived. The measured N 2 response can be well described by the model, but it is insufficient to completely describe the NO response. Modeling of different exposures is used to evaluate the qualitative picture presented by Zaharia et al

  17. Catalyst-free fabrication of novel ZnO/CuO core-Shell nanowires heterojunction: Controlled growth, structural and optoelectronic properties

    Science.gov (United States)

    Khan, Muhammad Arif; Wahab, Yussof; Muhammad, Rosnita; Tahir, Muhammad; Sakrani, Samsudi

    2018-03-01

    Development of controlled growth and vertically aligned ZnO/CuO core-shell heterojunction nanowires (NWs) with large area by a catalyst free vapor deposition and oxidation approach has been investigated. Structural characterization reveals successful fabrication of a core ZnO nanowire having single crystalline hexagonal wurtzite structure along [002] direction and CuO nanostructure shell with thickness (8-10 nm) having polycrystalline monoclinic structure. The optical property analysis suggests that the reflectance spectrum of ZnO/CuO heterostructure nanowires is decreased by 18% in the visible range, which correspondingly shows high absorption in this region as compared to pristine ZnO nanowires. The current-voltage (I-V) characteristics of core-shell heterojunction nanowires measured by conductive atomic force microscopy (C-AFM) shows excellent rectifying behavior, which indicates the characteristics of a good p-n junction. The high-resolution transmission electron microscopy (HRTEM) has confirmed the sharp junction interface between the core-shell heterojunction nanowire arrays. The valence band offset and conduction band offset at ZnO/CuO heterointerfaces are measured to be 2.4 ± 0.05 and 0.23 ± 0.005 eV respectively, using X-ray photoelectron spectroscopy (XPS) and a type-II band alignment structure is found. The results of this study contribute to the development of new advanced device heterostructures for solar energy conversion and optoelectronics applications.

  18. Nuclear moments and charge radii of argon isotopes between the neutron-shell closures N=20 and N=28

    CERN Document Server

    Blaum, K; Lassen, J; Lievens, P; Marinova, K; Neugart, R

    2008-01-01

    We report the measurement of optical isotope shifts for $^{40-44}\\!$Ar relative to $^{38}$Ar from which changes in the mean square nuclear charge radii across the 1$\\scriptstyle{f}_{7/2}$ neutron shell are deduced. In addition, the hyperfine structure of $^{41\\!}$Ar and $^{43}$Ar yields the spins, magnetic dipole and electric quadrupole moments, in particular the spin $\\,\\scriptstyle\\textrm{I}$ = 5/2 for $\\,^{43}\\!$Ar. The investigations were carried out by fast-beam collinear laser spectroscopy using highly sensitive detection based on optical pumping and state-selective collisional ionization. Mean square charge radii are now known from $^{32}$Ar to $^{46}$Ar, covering sd-shell as well as $\\scriptstyle{f}_{7/2}$-shell nuclei. They are discussed in the framework of spherical SGII Skyrme-type Hartree-Fock calculations, semi-empirically corrected for quadrupole core polarization. The Zamick-Talmi formula excellently describes the charge radii across the $\\scriptstyle{f}_{7/2}$ neutron shell, as it does for the...

  19. Unified description of pf-shell nuclei by the Monte Carlo shell model calculations

    Energy Technology Data Exchange (ETDEWEB)

    Mizusaki, Takahiro; Otsuka, Takaharu [Tokyo Univ. (Japan). Dept. of Physics; Honma, Michio

    1998-03-01

    The attempts to solve shell model by new methods are briefed. The shell model calculation by quantum Monte Carlo diagonalization which was proposed by the authors is a more practical method, and it became to be known that it can solve the problem with sufficiently good accuracy. As to the treatment of angular momentum, in the method of the authors, deformed Slater determinant is used as the basis, therefore, for making angular momentum into the peculiar state, projected operator is used. The space determined dynamically is treated mainly stochastically, and the energy of the multibody by the basis formed as the result is evaluated and selectively adopted. The symmetry is discussed, and the method of decomposing shell model space into dynamically determined space and the product of spin and isospin spaces was devised. The calculation processes are shown with the example of {sup 50}Mn nuclei. The calculation of the level structure of {sup 48}Cr with known exact energy can be done with the accuracy of peculiar absolute energy value within 200 keV. {sup 56}Ni nuclei are the self-conjugate nuclei of Z=N=28. The results of the shell model calculation of {sup 56}Ni nucleus structure by using the interactions of nuclear models are reported. (K.I.)

  20. Atomic-Beam Magnetic Resonance Experiments at ISOLDE

    CERN Multimedia

    2002-01-01

    The aim of the atomic-beam magnetic resonance (ABMR) experiments at ISOLDE is to map the nuclear behaviour in wide regions of the nuclear chart by measuring nuclear spins and moments of ground and isomeric states. This is made through an investigation of the atomic hyperfine structure of free, neutral atoms in a thermal atomic-beam using radio-frequency techniques. On-line operation allows the study of short-lived nuclei far from the region of beta-stability.\\\\ \\\\ The ABMR experiments on the |2S^1 ^2 elements Rb, Cs, Au and Fr have been completed, and present efforts are directed towards the elements with an open p-shell and on the rare-earth elements.\\\\ \\\\ The experimental data obtained are compared with results from model calculations, giving information on the single-particle structure and on the nuclear shape parameters.

  1. Anion vacancy-mediated ferromagnetism in atomic-thick Ni3N nanosheets

    Science.gov (United States)

    Xia, Baorui; Wang, Tongtong; Chi, Xiao; Yu, Xiaojiang; Liu, Peitao; Zhang, Jingyan; Xi, Shibo; Du, Yonghua; Gao, Daqiang

    2017-12-01

    Realizing spin and electronic behavior of two-dimensional ultrathin nanosheets is significant to construct next generation nanoelectronics. Here, atomic-thick Ni3N nanosheets with clear room temperature ferromagnetism and high saturation magnetization (1.2 emu/g) are reported. X-ray magnetic circular dichroism and first-principles calculation results give the evidence that the observed intrinsic ferromagnetism in Ni3N nanosheets originates from the surface N-deficiency, where alignments of localized large magnetic moments of Ni in the vicinity of the N defect can be aligned parallel to activate macroscopic ferromagnetism. These ultrathin Ni3N nanosheets show great potential application in next-generation electron devices.

  2. Suppression of alloy fluctuations in GaAs-AlGaAs core-shell nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Loitsch, Bernhard; Winnerl, Julia; Parzinger, Eric; Matich, Sonja; Wurstbauer, Ursula; Riedl, Hubert; Abstreiter, Gerhard; Finley, Jonathan J.; Koblmüller, Gregor [Walter Schottky Institut and Physik Department, Technische Universität München, 85748 Garching (Germany); Jeon, Nari; Lauhon, Lincoln J. [Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208 (United States); Döblinger, Markus [Department of Chemistry, Ludwig-Maximilians-Universität Munich, 81377 München (Germany)

    2016-08-29

    Probing localized alloy fluctuations and controlling them by growth kinetics have been relatively limited so far in nanoscale structures such as semiconductor nanowires (NWs). Here, we demonstrate the tuning of alloy fluctuations in molecular beam epitaxially grown GaAs-AlGaAs core-shell NWs by modifications of shell growth temperature, as investigated by correlated micro-photoluminescence, scanning transmission electron microscopy, and atom probe tomography. By reducing the shell growth temperature from T > 600 °C to below 400 °C, we find a strong reduction in alloy fluctuation mediated sharp-line luminescence, concurrent with a decrease in the non-randomness of the alloy distribution in the AlGaAs shell. This trend is further characterized by a change in the alloy compositional structure from unintentional quasi-superlattices of Ga- and Al-rich AlGaAs layers at high T to a nearly homogeneous random alloy distribution at low T.

  3. O-, N-Atoms-Coordinated Mn Cofactors within a Graphene Framework as Bioinspired Oxygen Reduction Reaction Electrocatalysts.

    Science.gov (United States)

    Yang, Yang; Mao, Kaitian; Gao, Shiqi; Huang, Hao; Xia, Guoliang; Lin, Zhiyu; Jiang, Peng; Wang, Changlai; Wang, Hui; Chen, Qianwang

    2018-05-28

    Manganese (Mn) is generally regarded as not being sufficiently active for the oxygen reduction reaction (ORR) compared to other transition metals such as Fe and Co. However, in biology, manganese-containing enzymes can catalyze oxygen-evolving reactions efficiently with a relative low onset potential. Here, atomically dispersed O and N atoms coordinated Mn active sites are incorporated within graphene frameworks to emulate both the structure and function of Mn cofactors in heme-copper oxidases superfamily. Unlike previous single-metal catalysts with general M-N-C structures, here, it is proved that a coordinated O atom can also play a significant role in tuning the intrinsic catalytic activities of transition metals. The biomimetic electrocatalyst exhibits superior performance for the ORR and zinc-air batteries under alkaline conditions, which is even better than that of commercial Pt/C. The excellent performance can be ascribed to the abundant atomically dispersed Mn cofactors in the graphene frameworks, confirmed by various characterization methods. Theoretical calculations reveal that the intrinsic catalytic activity of metal Mn can be significantly improved via changing local geometry of nearest coordinated O and N atoms. Especially, graphene frameworks containing the Mn-N 3 O 1 cofactor demonstrate the fastest ORR kinetics due to the tuning of the d electronic states to a reasonable state. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Shell model description of Ge isotopes

    International Nuclear Information System (INIS)

    Hirsch, J G; Srivastava, P C

    2012-01-01

    A shell model study of the low energy region of the spectra in Ge isotopes for 38 ≤ N ≤ 50 is presented, analyzing the excitation energies, quadrupole moments, B(E2) values and occupation numbers. The theoretical results have been compared with the available experimental data. The shell model calculations have been performed employing three different effective interactions and valence spaces. We have used two effective shell model interactions, JUN45 and jj44b, for the valence space f 5/2 pg 9/2 without truncation. To include the proton subshell f 7/2 in valence space we have employed the fpg effective interaction due to Sorlin et al., with 48 Ca as a core and a truncation in the number of excited particles.

  5. Optical properties of core-shell and multi-shell nanorods

    Science.gov (United States)

    Mokkath, Junais Habeeb; Shehata, Nader

    2018-05-01

    We report a first-principles time dependent density functional theory study of the optical response modulations in bimetallic core-shell (Na@Al and Al@Na) and multi-shell (Al@Na@Al@Na and Na@Al@Na@Al: concentric shells of Al and Na alternate) nanorods. All of the core-shell and multi-shell configurations display highly enhanced absorption intensity with respect to the pure Al and Na nanorods, showing sensitivity to both composition and chemical ordering. Remarkably large spectral intensity enhancements were found in a couple of core-shell configurations, indicative that optical response averaging based on the individual components can not be considered as true as always in the case of bimetallic core-shell nanorods. We believe that our theoretical results would be useful in promising applications depending on Aluminum-based plasmonic materials such as solar cells and sensors.

  6. Shell-model predictions for Lambda Lambda hypernuclei

    International Nuclear Information System (INIS)

    Gal, A.; Millener, D.

    2011-01-01

    It is shown how the recent shell-model determination of ΛN spin-dependent interaction terms in Λ hypernuclei allows for a reliable deduction of ΛΛ separation energies in ΛΛ hypernuclei across the nuclear p shell. Comparison is made with the available data, highlighting # Lambda# # Lambda# 11 Be and # Lambda# # Lambda# 12 Be which have been suggested as possible candidates for the KEK-E373 HIDA event.

  7. Use of shell model calculations in R-matrix studies of neutron-induced reactions

    International Nuclear Information System (INIS)

    Knox, H.D.

    1986-01-01

    R-matrix analyses of neutron-induced reactions for many of the lightest p-shell nuclei are difficult due to a lack of distinct resonance structure in the reaction cross sections. Initial values for the required R-matrix parameters, E,sub(lambda) and γsub(lambdac) for states in the compound system, can be obtained from shell model calculations. In the present work, the results of recent shell model calculations for the lithium isotopes have been used in R-matrix analyses of 6 Li+n and 7 Li+n reactions for E sub(n) 7 Li and 8 Li on the 6 Li+n and 7 Li+n reaction mechanisms and cross sections are discussed. (author)

  8. Novel chiral core-shell silica microspheres with trans-(1R,2R)-diaminocyclohexane bridged in the mesoporous shell: synthesis, characterization and application in high performance liquid chromatography.

    Science.gov (United States)

    Wu, Xiabing; You, Linjun; Di, Bin; Hao, Weiqiang; Su, Mengxiang; Gu, Yu; Shen, Lingling

    2013-07-19

    Novel chiral core-shell silica microspheres with trans-(1R,2R)-diaminocyclohexane (DACH) moiety bridged in the mesoporous shell were synthesized using layer-by-layer method. The chiral mesoporous shell around the nonporous silica core was formed by the co-condensation of N,N'-bis-[(triethoxysilyl)propyl]-trans-(1R,2R)-bis-(ureido)-cyclohexane (DACH-BS) and tetraethoxysilane (TEOS) using octadecyltrimethylammonium chloride (C18TMACl) and triblock poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) copolymer (P123) as the templates. The functionalized core-shell silica microspheres were characterized and tested as chiral stationary phases for high performance liquid chromatography (HPLC). R/S-1,1'-bi-2,2'-naphthol, R/S-6,6'-dibromo-1,1'-bi-2-naphthol and R/S-1,1'-bi-2,2'-phenanthrol were enantioseparated rapidly on the column packed with the DACH core-shell silica particles. Moreover, the column packed with core-shell particles exhibited better performance than the column packed with the DACH functionalized periodic mesoporous organosilicas. Copyright © 2013 Elsevier B.V. All rights reserved.

  9. Nuclear structure in the vicinity of shell closures far from stability

    International Nuclear Information System (INIS)

    Grawe, H.; Gorska, M.; Doering, J.

    2000-09-01

    The status of experimental approach to 100 Sn and 78 Ni is reviewed. Revised single particle energies for neutrons are deduced for the N=Z=50 shell closure and evidence for low lying I π =2 + and 3 - states is presented. Moderate E2 polarization charges of 0.1 e and 0.6 e are found to reproduce the experimental data when core excitation of 100 Sn is properly accounted for in the shell model. For the neutron rich Ni region no conclusive evidence for an N=40 subshell is found, whereas firm evidence for the persistence of the N=50 shell at 78 Ni is inferred from the existence of seniority isomers. The disappearance of this isomerism in the mid νg 9/2 shell is discussed. The spectroscopy of 216 Th disproves the existence of a Z=92 shell gap as predicted by some recent mean field calculations. Inversion of the πh 9/2 and f 7/2 orbitals at Z=90 is ascribed to the coupling of the f 7/2 (and i 13/2 ) protons to the low-lying 3 - state (ℎω 3 =1.69 MeV). (orig.)

  10. Cu 4s → 4p atomic like excitations in the Ne matrix.

    Science.gov (United States)

    Hatano, Yasuyo; Tatewaki, Hiroshi; Yamamoto, Shigeyoshi

    2013-06-07

    The lowest three or four excited states (the triplet or quartet states) of the Cu atom in a neon (Ne) matrix have been studied experimentally, and have been presumed to have the electronic configuration of Cu 4p(1). The origins of the triplet and the quartet are not yet fully clear, although many models have been proposed. It has been argued, for example, that the existence of different trapping sites would give rise to two partly overlapping triplets, leading to spectra having three or four lines or more. Below, the electronic structures of the ground state and lowest excited states of the Cu atom in the neon matrix are clarified by means of ab initio molecular orbital calculations, using the cluster model. It was found that a rather large vacancy (hollow) with residual Ne atoms is vital for explaining the observed spectra having three or more lines; the Cu atom occupies the center of the substitutional site of a face-centered cubic (fcc)-like cluster comprising 66 Ne atoms, in which the first shell composed of 12 Ne atoms is empty. The presence of the residual Ne atoms in the first shell gives rise to more than three excited states, explaining the experimental spectra. Electron-electron interaction (including the crystal field) and spin-orbit interaction are both important in explaining the experimental spectra.

  11. DFT Modeling of Cross-Linked Polyethylene: Role of Gold Atoms and Dispersion Interactions.

    Science.gov (United States)

    Blaško, Martin; Mach, Pavel; Antušek, Andrej; Urban, Miroslav

    2018-02-08

    Using DFT modeling, we analyze the concerted action of gold atoms and dispersion interactions in cross-linked polyethylene. Our model consists of two oligomer chains (PEn) with 7, 11, 15, 19, or 23 carbon atoms in each oligomer cross-linked with one to three Au atoms through C-Au-C bonds. In structures with a single gold atom the C-Au-C bond is located in the central position of the oligomer. Binding energies (BEs) with respect to two oligomer radical fragments and Au are as high as 362-489 kJ/mol depending on the length of the oligomer chain. When the dispersion contribution in PEn-Au-PEn oligomers is omitted, BE is almost independent of the number of carbon atoms, lying between 293 and 296 kJ/mol. The dispersion energy contributions to BEs in PEn-Au-PEn rise nearly linearly with the number of carbon atoms in the PEn chain. The carbon-carbon distance in the C-Au-C moiety is around 4.1 Å, similar to the bond distance between saturated closed shell chains in the polyethylene crystal. BEs of pure saturated closed shell PEn-PEn oligomers are 51-187 kJ/mol. Both Au atoms and dispersion interactions contribute considerably to the creation of nearly parallel chains of oligomers with reasonably high binding energies.

  12. Role of atom--atom inelastic collisions in two-temperature nonequilibrium plasmas

    International Nuclear Information System (INIS)

    Kunc, J.A.

    1987-01-01

    The contribution of inelastic atom--atom collisions to the production of electrons and excited atoms in two-temperature (with electron temperature T/sub e/, atomic temperature T/sub a/, and atomic density N/sub a/), steady-state, nonequilibrium atomic hydrogen plasma is investigated. The results are valid for plasmas having large amounts of atomic hydrogen as one of the plasma components, so that e--H and H--H inelastic collisions and interaction of these atoms with radiation dominate the production of electrons and excited hydrogen atoms. Densities of electrons and excited atoms are calculated in low-temperature plasma, with T/sub e/ and T/sub a/≤8000 K and 10 16 cm -3 ≤N/sub a/≤10 18 cm -3 , and with different degrees of the reabsorption of radiation. The results indicate that inelastic atom--atom collisions are important for production of electrons and excited atoms in partially ionized plasmas with medium and high atomic density and temperatures below 8000 K

  13. Ultrathin Interface Regime of Core-Shell Magnetic Nanoparticles for Effective Magnetism Tailoring.

    Science.gov (United States)

    Moon, Seung Ho; Noh, Seung-Hyun; Lee, Jae-Hyun; Shin, Tae-Hyun; Lim, Yongjun; Cheon, Jinwoo

    2017-02-08

    The magnetic exchange coupling interaction between hard and soft magnetic phases has been important for tailoring nanoscale magnetism, but spin interactions at the core-shell interface have not been well studied. Here, we systematically investigated a new interface phenomenon termed enhanced spin canting (ESC), which is operative when the shell thickness becomes ultrathin, a few atomic layers, and exhibits a large enhancement of magnetic coercivity (H C ). We found that ESC arises not from the typical hard-soft exchange coupling but rather from the large magnetic surface anisotropy (K S ) of the ultrathin interface. Due to this large increase in magnetism, ultrathin core-shell nanoparticles overreach the theoretical limit of magnetic energy product ((BH) max ) and exhibit one of the largest values of specific loss power (SLP), which testifies to their potential capability as an effective mediator of magnetic energy conversion.

  14. SPECTR-W3 online database on atomic properties of atoms and ions

    International Nuclear Information System (INIS)

    Faenov, A.Ya.; Magunov, A.I.; Pikuz, T.A.; Skobelev, I.Yu.; Loboda, P.A.; Bakshayev, N.N.; Gagarin, S.V.; Komosko, V.V.; Kuznetsov, K.S.; Markelenkov, S.A.; Petunin, S.A.; Popova, V.V.

    2002-01-01

    Recent progress in the novel information technologies based on the World-Wide Web (WWW) gives a new possibility for a worldwide exchange of atomic spectral and collisional data. This facilitates joint efforts of the international scientific community in basic and applied research, promising technological developments, and university education programs. Special-purpose atomic databases (ADBs) are needed for an effective employment of large-scale datasets. The ADB SPECTR developed at MISDC of VNIIFTRI has been used during the last decade in several laboratories in the world, including RFNC-VNIITF. The DB SPECTR accumulates a considerable amount of atomic data (about 500,000 records). These data were extracted from publications on experimental and theoretical studies in atomic physics, astrophysics, and plasma spectroscopy during the last few decades. The information for atoms and ions comprises the ionization potentials, the energy levels, the wavelengths and transition probabilities, and, to a lesser extent, - also the autoionization rates, and the electron-ion collision cross-sections and rates. The data are supplied with source references and comments elucidating the details of computations or measurements. Our goal is to create an interactive WWW information resource based on the extended and updated Web-oriented database version SPECTR-W3 and its further integration into the family of specialized atomic databases on the Internet. The version will incorporate novel experimental and theoretical data. An appropriate revision of the previously accumulated data will be performed from the viewpoint of their consistency to the current state-of-the-art. We are particularly interested in cooperation for storing the atomic collision data. Presently, a software shell with the up-to-date Web-interface is being developed to work with the SPECTR-W3 database. The shell would include the subsystems of information retrieval, input, update, and output in/from the database and

  15. Spectr-W3 Online Database On Atomic Properties Of Atoms And Ions

    Science.gov (United States)

    Faenov, A. Ya.; Magunov, A. I.; Pikuz, T. A.; Skobelev, I. Yu.; Loboda, P. A.; Bakshayev, N. N.; Gagarin, S. V.; Komosko, V. V.; Kuznetsov, K. S.; Markelenkov, S. A.

    2002-10-01

    Recent progress in the novel information technologies based on the World-Wide Web (WWW) gives a new possibility for a worldwide exchange of atomic spectral and collisional data. This facilitates joint efforts of the international scientific community in basic and applied research, promising technological developments, and university education programs. Special-purpose atomic databases (ADBs) are needed for an effective employment of large-scale datasets. The ADB SPECTR developed at MISDC of VNIIFTRI has been used during the last decade in several laboratories in the world, including RFNC-VNIITF. The DB SPECTR accumulates a considerable amount of atomic data (about 500,000 records). These data were extracted from publications on experimental and theoretical studies in atomic physics, astrophysics, and plasma spectroscopy during the last few decades. The information for atoms and ions comprises the ionization potentials, the energy levels, the wavelengths and transition probabilities, and, to a lesser extent, -- also the autoionization rates, and the electron-ion collision cross-sections and rates. The data are supplied with source references and comments elucidating the details of computations or measurements. Our goal is to create an interactive WWW information resource based on the extended and updated Web-oriented database version SPECTR-W3 and its further integration into the family of specialized atomic databases on the Internet. The version will incorporate novel experimental and theoretical data. An appropriate revision of the previously accumulated data will be performed from the viewpoint of their consistency to the current state-of-the-art. We are particularly interested in cooperation for storing the atomic collision data. Presently, a software shell with the up-to-date Web-interface is being developed to work with the SPECTR-W3 database. The shell would include the subsystems of information retrieval, input, update, and output in/from the database and

  16. Pentachlorophenol removal from aqueous matrices by sorption with almond shell residues

    International Nuclear Information System (INIS)

    Estevinho, B.N.; Ratola, N.; Alves, A.; Santos, L.

    2006-01-01

    Sorption with activated carbon has been the technique preferred for pentachlorophenol (PCP) removal from contaminated waters, but regeneration needs and high operation costs are supporting a renewed interest in the search for alternative sorbents. Among them, almond shell, an agricultural by-product, provides interesting economical advantages, once shells account for 50% (in mass) of the whole almond. In this work, the capacity of almond shells to remove PCP from waters without previous activation was studied in batch conditions. While PCP analysis was performed solid-phase microextraction (SPME) followed by gas chromatography with electron capture detection (GC-ECD), mercury porosimetry and Fourier transform infrared spectroscopy (FTIR) provided a preliminary physical and chemical characterization of the sorbent. Almond shells were essentially a macroporous material, with an average surface area of 12.9 ± 2.8 m 2 /g. The efficiency of PCP removal was 93 ± 14%, in 24 h, with an initial concentration of 100 μg/l PCP and 5 μg PCP/g shell. Isotherm data adjusted better to Freundlich equation, where K F and 1/n were 0.075 ± 0.081 mg 1-1/n l 1/n and 1.882 ± 0.289, respectively. Average desorption efficiency was 7%, indicating strong adsorption capacity. Results proved that almond shells may be an excellent low-cost alternative for PCP removal from contaminated waters

  17. Structures in the K-shell delta electron spectrum near threshold for ionization by fast charged particles

    International Nuclear Information System (INIS)

    Amundsen, P.A.; Aashamar, K.

    Results of calculations of the delta electron spectrum for K-shell ionization of atoms by fast charged particles for target charges in the range 6 2 <=40 are presented. Appreciable structure is found in the spectrum near the ionization threshold, in particular for fast projectiles and heavy target elements. The structure can be quite sensitive to the details of the effective atomic potentials. (Auth.)

  18. The local atomic quasicrystal structure of the icosahedral Mg25Y11Zn64 alloy

    International Nuclear Information System (INIS)

    Bruehne, S; Uhrig, E; Gross, C; Assmus, W; Masadeh, A S; Billinge, S J L

    2005-01-01

    A local and medium range atomic structure model for the face centred icosahedral (fci) Mg 25 Y 11 Zn 64 alloy has been established in a sphere of r = 27 A. The model was refined by least squares techniques using the atomic pair distribution (PDF) function obtained from synchrotron powder diffraction. Three hierarchies of the atomic arrangement can be found: (i) five types of local coordination polyhedra for the single atoms, four of which are of Frank-Kasper type. In turn, they (ii) form a three-shell (Bergman) cluster containing 104 atoms, which is condensed sharing its outer shell with its neighbouring clusters, and (iii) a cluster connecting scheme corresponding to a three-dimensional tiling leaving space for a few glue atoms. Inside adjacent clusters, Y 8 cubes are tilted with respect to each other and thus allow for overall icosahedral symmetry. It is shown that the title compound is essentially isomorphic to its holmium analogue. Therefore, fci-Mg-Y-Zn can be seen as the representative structure type for the other rare earth analogues fci-Mg-Zn-RE (RE = Dy, Er, Ho, Tb) reported in the literature

  19. Thick-target method in the measurement of inner-shell ionization cross-sections by low-energy electron impact

    International Nuclear Information System (INIS)

    An, Z.; Wu, Y.; Liu, M.T.; Duan, Y.M.; Tang, C.H.

    2006-01-01

    In this paper, we have studied the thick-target method for the measurements of atomic inner-shell ionization cross-section or X-ray production cross-section by keV electron impact. We find that in the processes of electron impact on the thick targets, the ratios of the characteristic X-ray yields of photoelectric ionization by bremsstrahlung to the total characteristic X-ray yields are Z-dependent and shell-dependent, and the ratios also show the weak energy-dependence. In addition, in the lower incident energy region (i.e. U < 5-6), the contribution from the rediffusion effect and the secondary electrons can be negligible. In general, the thick-target method can be appropriately applied to the measurements of atomic inner-shell ionization cross-sections or X-ray production cross-sections by electron impact for low and medium Z elements in the lower incident electron energy (i.e. U < 5-6). The experimental accuracies by the thick-target method can reach to the level equivalent or superior to the accuracies of experimental data based on the thin-target method. This thick-target method has been applied to the measurement of K-shell ionization cross-sections of Ni element by electron impact in this paper

  20. Low-energy electron scattering by C, N, and O atoms

    Energy Technology Data Exchange (ETDEWEB)

    Nesbet, R K [International Business Machines Corp., San Jose, Calif. (USA). Research Lab.

    1977-07-01

    Recent theoretical studies of low-energy electron scattering by C, N, and O atoms are reviewed and results are compared with available experimental data. A critical comparison is made of the two principal methods used in this work-polarized pseudostate expansion with R-matrix computations or direct integration, and Bethe-Goldstone expansion with matrix variational computations. 31 references.