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Sample records for atomic shells l

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

    Indian Academy of Sciences (India)

    G A V Ramana Murty; G J Naga Raju; V Vijayan; T Ranjan Rautray; B Seetharami Reddy; S Lakshminarayana; K L Narasimham; S Bhuloka Reddy

    2004-06-01

    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 atomic number of the targets atoms.

  2. Binding energy correction for atomic L-shell ionization by heavy charged particles

    International Nuclear Information System (INIS)

    During the process of inner shell ionization of atoms by low-velocity heavy charged particles the effective binding energy of the target electron is changed due to the presence of the incoming projectile. In the present work the binding energy corrections for the ionization of 2s and 2p sub-shells of the target atom have been calculated by employing approximate expressions for L-shell ionization based on a semi-classical approximation (SCA). The binding energy correction thus obtained has been incorporated in the classical binary encounter theory of ionization to calculate the L-shell ionization cross section of argon by the impact of low energy (50-200keV) protons. The results are compared with the available experimental data. (Auth.)

  3. Cross sections for K- and L-shell excitation in energetic ion-atom collisions

    International Nuclear Information System (INIS)

    Absolute K- and L-shell vacancy production cross sections have been determined from Auger-electron measurements in various heavy-ion-atom collisions. Collision systems with atomic numbers Z between 5 and 18 and with projectile energies varied between 6 and 600 keV were investigated. From cross section plots for some exemplary collision systems general trends are indicated and discussed in terms of the molecular-orbital (MO) model. Cross section ratios are deduced and compared to theoretical predictions

  4. An extended empirical model for L- and M-shell ionizations of atoms

    CERN Document Server

    Talukder, M R

    2011-01-01

    An extension of the analytical model of Talukder et al (Int. J. Mass Spectrom. 269 (2008) 118) is proposed to estimate electron impact single L- and M-shell ionization cross sections of atoms with incident energy from threshold to ultra-relativistic range. Comparisons are made with other theoretical calculations. It is found that this model agrees well with the experimental data and quantum calculations.

  5. Models for L-shell filling of slow hollow atoms moving below a surface

    International Nuclear Information System (INIS)

    A multiple cascade model is used to analyze the filling of L- and K-vacancies of hollow Ne atoms moving in shallow layers of an Al (111) surface. The model requires cross sections for charge transfer into the L-shell of the projectile which were determined from molecular-orbital calculations based on solid-state energies and screening effects. The analysis includes mechanisms of Landau-Zener curve-crossing and Fano-Lichten promotion. Absorption and build-up effects within the solid were taken into account. The results from the cascade model show good agreement with the ratio of L- to K-Auger emission recently measured for Ne9+ incident on Al. (orig.)

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

    International Nuclear Information System (INIS)

    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)

  7. Isolation and Structural Characterization of a Mackay 55-Metal-Atom Two-Shell Icosahedron of Pseudo-Ih Symmetry, Pd55L12(μ3-CO)20 (L = PR3, R = Isopropyl): Comparative Analysis with Interior Two-Shell Icosahedral Geometries in Capped Three-Shell Pd145, Pt-Centered Four-Shell Pd-Pt M165, and Four-Shell Au133 Nanoclusters.

    Science.gov (United States)

    Erickson, Jeremiah D; Mednikov, Evgueni G; Ivanov, Sergei A; Dahl, Lawrence F

    2016-02-10

    We present the first successful isolation and crystallographic characterization of a Mackay 55-metal-atom two-shell icosahedron, Pd55L12(μ3-CO)20 (L = PPr(i)3) (1). Its two-shell icosahedron of pseudo-Ih symmetry (without isopropyl substituents) enables a structural/bonding comparison with interior 55-metal-atom two-shell icosahedral geometries observed within the multi-shell capped 145-metal-atom three-shell Pd145(CO)72(PEt3)30 and 165-metal-atom four-shell Pt-centered (μ12-Pt)Pd164-xPtx(CO)72(PPh3)20 (x ≈ 7) nanoclusters, and within the recently reported four-shell Au133(SC6H4-p-Bu(t))52 nanocluster. DFT calculations carried out on a Pd55(CO)20(PH3)12 model analogue, with triisopropyl phosphine substituents replaced by H atoms, revealed a positive +0.84 e charge for the entire Pd55 core, with a highly positive second-shell Pd42 surface of +1.93 e. PMID:26790717

  8. Following electron impact excitations of Rn, Ra, Th, U and Pu single atom L sub-shells ionization cross section calculations by using Lotz's equation

    Science.gov (United States)

    Ayinol, M.; Aydeniz, D.

    2016-03-01

    L shell ionization cross section and Li subshells ionization cross sections of Rn, Ra, Th, U, Pu atoms calculated. For each of atoms, ten different electron impact energy values (Eo) are used. Calculations carried out by using Lotz equation in Matlab. First, calculations done for non-relativistic case by using non-relativistic Lotz equation then repeated with relativistic Lotz equation. σL total and σLi(i = 1,2,3) subshells ionisation cross section values obtained for Eo values in the energy range of ELi atom. Starting almost from Eo = ELi values of the each sub shell ionization threshold energy, σL total and σLi (i = 1,2,3) are increasing rapidly with Eo. For a fixed Eo = 3.ELi), while Z increases from 86L and σLi (i = 1, 2,3) are decrease. These results will also help to understand some σLi(i = 1,2,3) subshells results obtained from other electron-atom impact studies.

  9. Atomic inner-shell transitions

    Science.gov (United States)

    Crasemann, B.; Chen, M. H.; Mark, H.

    1984-01-01

    Atomic inner-shell processes have quite different characteristics, in several important aspects, from processes in the optical regime. Energies are large, e.g., the 1s binding energy reaches 100 keV at Z = 87; relativistic and quantum-electrodynamic effects therefore are strong. Radiationless transitions vastly dominate over photon emission in most cases. Isolated inner-shell vacancies have pronounced single-particle character, with correlations generally contributing only approximately 1 eV to the 1s and 2p binding energies; the structure of such systems is thus well tractable by independent-particle self-consistent-field atomic models. For systems containing multiple deep inner-shell vacancies, or for highly stripped ions, the importance of relativistic intermediate coupling and configuration interaction becomes pronounced. Cancellation of the Coulomb interaction can lead to strong manifestations of the Breit interaction in such phenomena as multiplet splitting and hypersatellite X-ray shifts. Unique opportunities arise for the test of theory.

  10. Measurement of atomic L shell Coster-Kronig yields (f12, f23 and f13) for some elements in the atomic number range 59≤Z≤90

    International Nuclear Information System (INIS)

    Non-radiative transitions cause changes in the generation of the intensity of the L lines. In order to investigate the physical quantities relevant to the L lines affected by the non-radiative transitions, experimental measurements were carried out using a Si(Li) x-ray spectrometer. Atomic L shell Coster-Kronig yields (f12, f13 and f23) for some elements in the atomic number range 59≤Z≤90 were determined. These selected measured semi-empirical values were also fitted by least squares to polynomials in Z of the form ΣnanZn (except for f13) and compared with theoretical and with earlier fitted values. (author)

  11. Atomic processes in nova shells

    International Nuclear Information System (INIS)

    The unusual spectra of the spatially-resolved nova shells of DQ Her, T Aur and CP Pup are reviewed. Because calculations for these conditions have not been made, recombination models of HI, HeI and CNO from a neutral to a doubly ionized state were constructed. The models are described and the results presented for densities at various temperatures. A photoionization model is also described. The effects of non-uniform density distributions in nova shells have been investigated and the observational consequences discussed. A model of the CP Pup shell is described and the evolution of this plasma during the nova's constant luminosity phase traced. The properties of neon novae are summarized and compared with the features seen in the optical spectra of old classical novae. Enhanced neon abundances are used in the model of the CP Pup Shell to investigate its effect on the evolution of the shell. Finally, the results of some near-infrared observations made on the shells of CP Pup, RR Pic and T Pyx are reported. 245 refs., 48 tabs., 17 figs

  12. Atomic-level models of the bacterial carboxysome shell

    International Nuclear Information System (INIS)

    The carboxysome is a bacterial microcompartment that functions as a simple organelle by sequestering enzymes involved in carbon fixation. The carboxysome shell is roughly 800 to 1400 angstroms in diameter and is assembled from several thousand protein subunits. Previous studies have revealed the three-dimensional structures of hexameric carboxysome shell proteins, which self-assemble into molecular layers that most likely constitute the facets of the polyhedral shell. Here, we report the three-dimensional structures of two proteins of previously unknown function, CcmL and OrfA (or CsoS4A), from the two known classes of carboxysomes, at resolutions of 2.4 and 2.15 angstroms. Both proteins assemble to form pentameric structures whose size and shape are compatible with formation of vertices in an icosahedral shell. Combining these pentamers with the hexamers previously elucidated gives two plausible, preliminary atomic models for the carboxysome shell.

  13. Multiphoton inner-shell ionization of the carbon atom

    OpenAIRE

    Rey, H. F.; Hart, H W

    2015-01-01

    We apply time-dependent R-matrix theory to study inner-shell ionization of C atoms in ultra-short high-frequency light fields with a photon energy between 170 and 245 eV. At an intensity of 1017 W/cm2, ionization is dominated by single-photon emission of a 2l electron, with two-photon emission of a 1s electron accounting for about 2-3% of all emission processes, and two-photon emission of 2l contributing about 0.5-1%. Three-photon emission of a 1s electron is estimated to contribute about 0.0...

  14. The Atomic Regular Polyhedron Electronic Shell

    Directory of Open Access Journals (Sweden)

    Zilong Kong

    2013-10-01

    Full Text Available The periodic table of elements is arranged based on a series of regular polyhedron. The stability of inert gas atoms can be explained by the distribution of electrons, as well as their motion and magnetic force structure. A magnetic force regular octahedron is proposed. It is a unique configuration that best satisfies the convergence of electrons moving in the same direction within regular polyhedra. In the case of an electrostatic force crust, the formal electron spin accounts for the crusts intrinsic magnetic moment exceeding the speed of light. If one is to consider that the electron has a magnetic outer layer and an electrostatic inner layer, then the question can be solved and abovementioned inference can provide the basis for magnetic force and momentum for the regular octahedron model. The electron periphery has twenty-petal adsorptive substances; the existence of adsorptive substance causes the magnetic force greater than the electrostatic force. Each electronic shell in the regular polyhedron is in accordance with the electron configuration of periodic table of elements; the kinetic track of each electron is a surface of regular polyhedron. The magnetic properties of iron, cobalt, and nickel can be explained by the regular dodecahedron electronic shell of an atom. The electron orbit converged from reverse direction can explain diamond. The adsorptive substances found in atomic nuclei and electrons are defined as magnetic particles called magnetons. The thermodynamic magneton theory can be better explained when it is analyzed using principles of thermodynamics, superconductivity, viscosity, and even in the creation of glass. The structure of the light is a helical line.

  15. Photoexcitation of K-shell and L-shell Hollow Beryllium

    International Nuclear Information System (INIS)

    We have observed K-shell and L-shell hollow beryllium atoms (2s22p3s and 1s3s23p) created by photoexcitation using synchrotron radiation. Resonance shapes were fitted to the Fano profile and the parameters were deduced. A Dirac-Fock calculation was performed to identify the configuration of the peaks and to predict other hollow atomic peaks. The results of the calculation were in good agreement with the experimental data. The comparison of the transition strength has revealed that the three-electron photoexcitation to the 1s3s23p configuration is stronger than the two-electron photoexcitation to the 2s22p3s configuration. This is attributed to the large overlap between the 2s orbital of the ground state (1s22s2) with the 3s orbital of the L-shell hollow state (1s3s23p)

  16. Inner-shell excitation of alkali-metal atoms

    International Nuclear Information System (INIS)

    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

  17. Measurement of vacancy transfer probability from K to L shell using K-shell fluorescence yields

    Indian Academy of Sciences (India)

    Ö Söğüt; E Büyükkasap; A Küçükönder; T Tarakçioğlu

    2009-10-01

    The vacancy transfer probabilities from K to L shell through radiative decay, KL , have been deduced for the elements in the range 19 ≤ ≤ 58 using K-shell fluorescence yields. The targets were irradiated with photons at 59.5 keV from a 75mCi 241Am annular source. The K X-rays from different targets were detected with a high resolution Si(Li) detector. The measurement of vacancy transfer probabilities are least-squared fitted to second-order polynomials to obtain analytical relations that represent these probabilities as a function of atomic number. The obtained results agree with theoretical and fitted values.

  18. Improved atomic shell excitation and relaxation in the TIGER series codes

    International Nuclear Information System (INIS)

    A new version of the TIGER Monte Carlo electron/photon transport code that more accurately models the transport for problems where atomic-shell effects are important is documented. The new model includes both electron impact ionization and photoionization of the K, L1, L2, L3, M (average) and N (average) shells, as well as a description of the subsequent atomic relaxation cascade. The relevant physical theories are essentially equivalent to those currently being employed in the SANDYL code. Because these modifications are only incidentally affected by the problem geometry, they can easily be extended to other codes in the TIGER series

  19. Symmetry chains for atomic shell model III. Symmetry chains conserving total orbital angular momentum

    Energy Technology Data Exchange (ETDEWEB)

    Thomas, M.S. (Royal Military Coll. of Canada, Kingston, Ontario); Gruber, B. (Technische Univ. Clausthal, Clausthal-Zellerfeld (Germany, F.R.). Inst. fuer Theoretische Physik)

    1982-01-01

    In this article symmetry chains for the atomic shell model are investigated which lead from the group SO(8l+-5) to the subgroup SOsub(L)(3). The tail group SOsub(L)(3) corresponds to total orbital angular momentum. Along these chains total orbital angular momentum L is a good quantum number, but not total spin S. Total orbital angular momentum can be considered as being made up of four quasi angular momenta.

  20. Atomic shell structure from the Single-Exponential Decay Detector

    International Nuclear Information System (INIS)

    The density of atomic systems is analysed via the Single-Exponential Decay Detector (SEDD). SEDD is a scalar field designed to explore mathematical, rather than physical, properties of electron density. Nevertheless, it has been shown that SEDD can serve as a descriptor of bonding patterns in molecules as well as an indicator of atomic shells [P. de Silva, J. Korchowiec, and T. A. Wesolowski, ChemPhysChem 13, 3462 (2012)]. In this work, a more detailed analysis of atomic shells is done for atoms in the Li–Xe series. Shell populations based on SEDD agree with the Aufbau principle even better than those obtained from the Electron Localization Function, which is a popular indicator of electron localization. A link between SEDD and the local wave vector is given, which provides a physical interpretation of SEDD

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

    International Nuclear Information System (INIS)

    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

  2. Shell evolution of atomic nuclei due to the tensor force

    International Nuclear Information System (INIS)

    Magic numbers and shell structure are extremely important for the study of atomic nuclei, as they determine the mass, the shape of surface, and the limit of the existence of nuclei, and have been considered to be universal over all nuclei, since Mayer and Jensen (1949). However, recent studies on exotic nuclei with large variations of proton or neutron numbers indicate that the changes of magic numbers and shell structure, i.e, shell evolution, arise due to nuclear forces, in particular the tensor force, demolishing this universality. We shall present an overview of such a paradigm shift emerging in exotic nuclei. (author)

  3. Double K-shell photoionization of atomic beryllium

    Energy Technology Data Exchange (ETDEWEB)

    Yip, F. L. [Departamento de Quimica, Modulo 13, Universidad Autonoma de Madrid, E-28049 Madrid (Spain); Martin, F. [Departamento de Quimica, Modulo 13, Universidad Autonoma de Madrid, E-28049 Madrid (Spain); Instituto Madrilen(tilde sign)o de Estudios Avanzados en Nanociencia, Cantoblanco, E-28049 Madrid (Spain); McCurdy, C. W. [Department of Chemistry, University of California, Davis, California 95616 (United States); Lawrence Berkeley National Laboratory, Chemical Sciences, and Ultrafast X-ray Science Laboratory, Berkeley, California 94720 (United States); Rescigno, T. N. [Lawrence Berkeley National Laboratory, Chemical Sciences, and Ultrafast X-ray Science Laboratory, Berkeley, California 94720 (United States)

    2011-11-15

    Double photoionization of the core 1s electrons in atomic beryllium is theoretically studied using a hybrid approach that combines orbital and grid-based representations of the Hamiltonian. The {sup 1} S ground state and {sup 1} P final state contain a double occupancy of the 2s valence shell in all configurations used to represent the correlated wave function. Triply differential cross sections are evaluated, with particular attention focused on a comparison of the effects of scattering the ejected electrons through the spherically symmetric valence shell with similar cross sections for helium, representing a purely two-electron target with an analogous initial-state configuration.

  4. Inner-shell Photoionization Studies of Neutral Atomic Nitrogen

    Science.gov (United States)

    Stolte, W. C.; Jonauskas, V.; Lindle, D. W.; Sant'Anna, M. M.; Savin, D. W.

    2016-02-01

    Inner-shell ionization of a 1s electron by either photons or electrons is important for X-ray photoionized objects such as active galactic nuclei and electron-ionized sources such as supernova remnants. Modeling and interpreting observations of such objects requires accurate predictions for the charge state distribution (CSD), which results as the 1s-hole system stabilizes. Due to the complexity of the complete stabilization process, few modern calculations exist and the community currently relies on 40-year-old atomic data. Here, we present a combined experimental and theoretical study for inner-shell photoionization of neutral atomic nitrogen for photon energies of 403-475 eV. Results are reported for the total ion yield cross section, for the branching ratios for formation of N+, {{{N}}}2+, and {{{N}}}3+, and for the average charge state. We find significant differences when comparing to the data currently available to the astrophysics community. For example, while the branching ratio to {{{N}}}2+ is somewhat reduced, that for N+ is greatly increased, and that to {{{N}}}3+, which was predicted to be zero, grows to ≈ 10% at the higher photon energies studied. This work demonstrates some of the shortcomings in the theoretical CSD data base for inner-shell ionization and points the way for the improvements needed to more reliably model the role of inner-shell ionization of cosmic plasmas.

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

    International Nuclear Information System (INIS)

    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-, L1-, L2,3-, M1-, M2,3- and M4,5 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 Xe7+, Xe8+, Xe9+ and Xe10+ ions, and the charged X8+ ions are the highest. The main product from the L1- shell ionization is found to be Xe8+, Xe9+ ions, while the charged Xe8+ ions predominate at L2,3 hole states. The charged Xe6+, Xe7+ and Xe8+ ions mainly yield from 3s1/2 and 3p1/2,3/2 ionization, while Xe in 3d3/2,5/2 hole states mainly turns into Xe4+ and Xe5+ ions. The present results are found to agree well with the experimental data.

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

    International Nuclear Information System (INIS)

    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, L1, L2,3, M1, M2,3 and M4,5 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 Xe7+, Xe8+, Xe9+ and Xe10+ ions, and the charged X8+ ions are the highest. The main product from the L1 shell ionization is found to be Xe8+, Xe9+ ions, while the charged Xe8+ ions predominate at L2,3 hole states. The charged Xe6+, Xe7+ and Xe8+ ions mainly yield from 3s1/2 and 3p1/2,3/2 ionization, while Xe in 3d3/2,5/2 hole states mainly turns into Xe4+ and Xe5+ ions. The present results are found to agree well with the experimental data. (author)

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

    Science.gov (United States)

    Amusia, Miron; Chernysheva, Larissa

    2016-05-01

    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 upon endohedrals that are formed when Ne and Ar atom are stuffed inside fullerene C60. To obtain the presented results, we have suggested a simplified approach that permits to incorporate the effect of fullerenes polarizability into the endohedrals polarization potential. By applying this approach, we obtained numeric results that show strong variations in shape and magnitudes of scattering phases and cross-sections due to effect of fullerene polarization upon the endohedral polarization potential. Using concrete examples we have demonstrated that the elastic scattering of electrons upon endohedrals is an entirely quantum mechanical process, where addition of even a single atom can qualitatively alter the multi-particle cross-section.

  8. K-shell transitions in L-shell ions with the EBIT calorimeter spectrometer

    Science.gov (United States)

    Hell, Natalie; Brown, G. V.; Wilms, J.; Beiersdorfer, P.; Kelley, R. L.; Kilbourne, C. A.; Porter, F. S.

    2015-08-01

    With the large improvement in effective area of Astro-H's micro-calorimeter soft X-ray spectrometer (SXS) over grating spectrometers, high-resolution X-ray spectroscopy with good signal to noise will become more commonly available, also for faint and extended sources. This will result in a range of spectral lines being resolved for the first time in celestial sources, especially in the Fe region. However, a large number of X-ray line energies in the atomic databases are known to a lesser accuracy than that expected for Astro-H/SXS, or have no known uncertainty at all. To benchmark the available calculations, we have therefore started to measure reference energies of K-shell transition in L-shell ions for astrophysically relevant elements in the range 11 ≤ Z ≤ 28 (Na to Ni), using the Lawrence Livermore National Laboratory's EBIT-I electron beam ion trap coupled with the NASA/GSFC EBIT calorimeter spectrometer (ECS). The ECS has a resolution of ~5eV, i.e., similar to Astro-H/SXS and Chandra/HETG. A comparison to crystal spectra of lower charge states of sulfur with ~0.6eV resolution shows that the analysis of spectra taken at ECS resolution allows us to determine the transition energies of the strongest components.Work at LLNL was performed under the auspices of DOE under contract DE-AC52-07NA27344 and supported by NASA's APRA program.

  9. L x rays emitted from multiply ionized holmium atoms

    International Nuclear Information System (INIS)

    Spectra of L x rays emitted from Ho targets bombarded by 10 keV electrons and 6 MeV/amu C, Ne, Ar, Kr, and Xe ions were measured in high resolution using a curved crystal spectrometer. The spectra were analyzed in order to examine the systematic evolution of the L x-ray satellite structure as a function of projectile atomic number. Scaling rules are established for the apparent average M-shell spectator vacancy fraction and apparent average double to single L-vacancy population ratio at the time of L x-ray emission. The results are compared to those obtained for K-shell ionizing collisions and with predictions of the geometrical model

  10. Scattering of low-energy neutrinos on atomic shells

    International Nuclear Information System (INIS)

    We present a derivation of the total cross section for inelastic scattering of low-energy solar neutrinos and reactor antineutrinos on bound electrons, resulting in a transition of the electron to an excited state. The atomic-shell structure of various chemical elements is treated in terms of a nonrelativistic approximation. We estimate the interaction rates for modern neutrino detectors, in particular the Borexino and GEMMA experiments. We establish that in these experiments the effect can be safely neglected, but it could be accessible to future large-volume neutrino detectors with low energy threshold

  11. Time delay in valence shell photoionization of noble gas atoms

    CERN Document Server

    Kheifets, A S

    2013-01-01

    We use the non-relativistic random phase approximation with exchange to perform calculations of valence shell photoionization of Ne, Ar, Kr and Xe from their respective thresholds to photon energy of 200 eV. The energy derivative of the complex phase of the photoionization matrix elements is converted to the photoelectron group delay that can be measured in attosecond streaking or two-photon transitions interference experiments. Comparison with reported time delay measurements in Ne and Ar at a few selected photon energies is made. Systematic mapping of time delay across a wide range of photon energies in several atomic targets allows to highlight important aspects of fundamental atomic physics that can be probed by attosecond time delay measurements.

  12. Fe L-Shell Density Diagnostics in Theory and Practice

    Energy Technology Data Exchange (ETDEWEB)

    Mauche, C W; Liedahl, D A; Fournier, K B

    2004-12-06

    We provide a discussion of the density and photoexcitation sensitivity of the X-ray spectra of Fe L-shell ions (Fe XVII-Fe XXIV) calculated with the Livermore X-ray Spectral Synthesizer, a suite of IDL codes that calculates spectral models of highly charged ions based primarily on HULLAC atomic data. These models are applicable to collisionally ionized laboratory or cosmic plasmas with electron temperatures T{sub e} {approx} 2-45 MK (0.2-4 keV) and electron densities n{sub e} {approx}> 10{sup 11} cm{sup -3}. Potentially useful density diagnostics are identified for Fe XVII and Fe XIX-Fe XXIII, with the most straightforward being the Fe XVII I(17.10 {angstrom})/I(17.05 {angstrom}) line ratio and the Fe XXII I(11.92 {angstrom})/I(11.77 {angstrom}) line ratio. Applying these models to the Chandra X-ray Observatory High Energy Transmission Grating spectrum of the intermediate polar EX Hya, we find that the strength of all the Fe L-shell lines are consistent with electron densities n{sub e} {approx}> 1 x 10{sup 14} cm{sup -3}. Specifically, from the observed Fe XVII I(17.10{angstrom})/I(17.05{angstrom}) line ratio, we infer an electron density n{sub e} {approx}> 2 x 10{sup 14} cm{sup -3} at the 3{sigma} level, while from the observed Fe XXII I(11.92 {angstrom})/I(11.77 {angstrom}) line ratio, we infer n{sub e} = 1.0{sub -0.5}{sup +2.0} x 10{sup 14} cm{sup -3} at the 1{sigma} level and n{sub e} {approx}> 2 x 10{sup 13} cm{sup -3} at the 3{sigma} level.

  13. Multiphoton inner-shell ionization of the carbon atom

    CERN Document Server

    Rey, H F

    2015-01-01

    We apply time-dependent R-matrix theory to study inner-shell ionization of C atoms in ultra-short high-frequency light fields with a photon energy between 170 and 245 eV. At an intensity of 10$^{17}$ W/cm$^2$, ionization is dominated by single-photon emission of a $2\\ell$ electron, with two-photon emission of a 1s electron accounting for about 2-3\\% of all emission processes, and two-photon emission of $2\\ell$ contributing about 0.5-1\\%. Three-photon emission of a 1s electron is estimated to contribute about 0.01-0.03\\%. Around a photon energy of 225 eV, two-photon emission of a 1s electron, leaving C$^+$ in either 1s2s2p$^3$ or 1s2p$^4$ is resonantly enhanced by intermediate 1s2s$^2$2p$^3$ states. The results demonstrate the capability of time-dependent R-matrix theory to describe inner-shell ionization processes including rearrangement of the outer electrons.

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

    CERN Document Server

    Amusia, M Ya

    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 polarizability into the Neon and Argon endohedrals polarization potential. As a result, we obtained numeric results that show strong variations in shape and magnitudes of scattering phases and cross-sections due to effect of fullerene polarization upon the endohedral polarization potential.

  15. Simultaneous melting of shell and core atoms, a molecular dynamics study of lithium–copper nanoalloys

    International Nuclear Information System (INIS)

    Melting of nanoalloys originates from the alloy surface and gradually propagates into the interior region. The thermal stability of Li cores and Cu shells nanoalloy with size of 3.5 nm is studied through molecular dynamics and embedded atom method with the use of potential energy, Lindemann index, and radial distribution function. Results show that the shell and core Li atoms are melted in two steps: first, some Li atoms in the core migrate to the nanoalloy surface and maintain a typical solid state despite that the system temperature is higher than the bulk melting point of Li because of Li solidification in the solid–liquid interface; second, the shell and core Li atoms are simultaneously melted at high temperatures. A comparative study of Li@Cu nanoalloys with different Li atomic numbers shows that thermal stability is enhanced with the decreasing number of Li atoms within the nanoalloys because of weak binding for Cu thin shells

  16. 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.

  17. L-shell ionization by relativistic electrons

    International Nuclear Information System (INIS)

    Measurements of the relative x-ray production cross-sections Lsub(α)/Lsub(l), Lsub(β)/Lsub(α) and Lsub (γ)/Lsub(α) by relativistic electrons for the heavy elements Gd, Tm, Ta, Au, Pb, Bi and Th have been carried out. The ratios Lsub(β)/Lsub(α) and Lsub(α)/Lsub (l), are compared with previous experimental and theoretical work

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

    International Nuclear Information System (INIS)

    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)

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

    International Nuclear Information System (INIS)

    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)

  20. Nuclear shell energies and deformations in atomic mass formula

    International Nuclear Information System (INIS)

    Our group has for several years been studying a method of calculating nuclear shell energies and incorporating them into a mass formula. This method is characterized by the calculation of single-particle levels in an extended spherical Woods-Saxon potential, the extraction of crude shell energy, the refinement of crude shell energy due to residual interactions, and the incorporation into a mass formula. Here, we report the advance of this work focusing especially on nuclear deformations, and give some preliminary results and remarks. (author)

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

    International Nuclear Information System (INIS)

    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

  2. Electron-pair shell density approximation applied to inner and outer electron radii of atoms

    International Nuclear Information System (INIS)

    The shell density approximation to the electron-pair radial density of atoms is applied to the inner 〈r〉 and outer 〈r>〉 electron radii, which are two components of the familiar average electron radius 〈r〉. The inner and outer radii with two-electron nature are found to be expressed by simple weighted sums of single-electron shell radii, where the weight factors are related to the numbers of shell electrons. A numerical examination of the 53 atoms He through Xe shows that the average relative errors of the approximation are only 3.5% and 1.1% for the inner and outer electron radii, respectively. Lower and upper bounds to 〈r〉 and 〈r>〉 are discussed. The present results also bound the electron-pair relative distance and centre-of-mass radius in terms of the single-electron shell radii. (paper)

  3. L-Shell Spectroscopy of Au as a Temperature Diagnostic Tool

    Energy Technology Data Exchange (ETDEWEB)

    Trabert, E; Hansen, S B; Beiersdorfer, P; Brown, G V; Widmann, K; Chung, H K

    2008-03-27

    In order to develop plasma diagnostic for reduced-size hot hohlraums under laser irradiation, they have studied the L-shell emission from highly charged gold ions in the SuperEBIT electron beam ion trap. The resolving power necessary to identify emission features from individual charge states in a picket fence pattern has been estimated, and the observed radiation features have been compared with atomic structure calculations. They find that the strong 3d{sub 5/2} {yields} 2p{sub 3/2} emission features are particularly useful in determining the charge state distribution and average ion charge , which are strongly sensitive to the electron temperature.

  4. X-ray Signature of Charge Exchange in the Spectra of L-shell Iron Ions

    Energy Technology Data Exchange (ETDEWEB)

    Beiersdorfer, P; Schweikhard, L; Liebisch, P; Brown, G V

    2007-01-05

    The X-ray signature of charge exchange between highly charged L-shell iron ions and neutral gas atoms was studied in the laboratory in order to assess its diagnostic utility. Significant differences with spectra formed by electron-impact excitation were observed. In particular, a strong enhancement was found of the emission corresponding to n {le} 4 {yields} n = 2 transitions relative to the n = 3 {yields} n = 2 emission. This enhancement was detectable even with relatively low-resolution X-ray instrumentation (E/{Delta}E {approx} 10) and may enable future identification of charge exchange as a line-formation mechanism in astrophysical spectra.

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

    International Nuclear Information System (INIS)

    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.)

  6. 78 FR 14778 - Application to Export Electric Energy; Shell Energy North America (US), L.P.

    Science.gov (United States)

    2013-03-07

    ...Shell Energy North America (US), L.P. (Shell Energy) has applied to renew its authority to transmit electric energy from the United States to Mexico pursuant to section 202(e) of the Federal Power...

  7. 78 FR 14779 - Application to Export Electric Energy; Shell Energy North America (US), L.P.

    Science.gov (United States)

    2013-03-07

    ...Shell Energy North America (US), L.P. (Shell Energy) has applied to renew its authority to transmit electric energy from the United States to Canada pursuant to section 202(e) of the Federal Power...

  8. The Casimir-Polder interaction an atom with spherical shell

    OpenAIRE

    Khusnutdinov, Nail

    2014-01-01

    The Casimir-Polder and van der Waals interaction energy of an atom with infinitely thin sphere with finite conductivity is investigated in the framework of the hydrodynamic approach. We put the sphere into spherical cavity inside the infinite dielectric media, then calculate the energy of vacuum fluctuations in the context of the zeta-function approach. The energy for a single atom is obtained by rarefying media. The Casimir-Polder expression for an atom and plate is recovered in the limit of...

  9. L-SHELL IONIZATION MEASUREMENT OF TUNGSTEN BY ELECTRON IMPACT

    Institute of Scientific and Technical Information of China (English)

    PENG XIU-FENG; HE FU-QING; LONG XIAN-GUAN

    2000-01-01

    L-shell partial production cross sections of Lα- , Lβ-, Lγ- rays by electron impact were measured by observing the counts of X-ray from impacted thin tungsten target. Total production cross sections and mean ionization cross sections were deduced from these measured results. The electron beam energy range was from 11 to 36 keV. Tungsten was sputtered onto a carbon backing to reduce bremsstrahlung of the backing. The effect of electrons reflected by the backing has been corrected. Comparison with two theoretical calculations has performed. The experimental results agree rather well with the theoretical predications.

  10. Mapping the Two-Component Atomic Fermi Gas to the Nuclear Shell-Model

    DEFF Research Database (Denmark)

    Özen, C.; Zinner, Nikolaj Thomas

    2014-01-01

    the external potential becomes important. A system of two-species fermionic cold atoms with an attractive zero-range interaction is analogous to a simple model of nucleus in which neutrons and protons interact only through a residual pairing interaction. In this article, we discuss how the problem of...... a two-component atomic fermi gas in a tight external trap can be mapped to the nuclear shell model so that readily available many-body techniques in nuclear physics, such as the Shell Model Monte Carlo (SMMC) method, can be directly applied to the study of these systems. We demonstrate an...

  11. K-shell ionization of atoms and ions by relativistic projectiles

    International Nuclear Information System (INIS)

    We evaluate the total cross section for the single K-shell ionization of atoms and ions by the impact of relativistic electrons. The study is performed to leading orders of the QED perturbation theory with respect to the parameters αZ and 1/Z. The results obtained are in good agreement with experimental data for different atomic targets. In the case of moderate values of the nuclear charge Z, the total cross section is described by a simple analytic formula. The K-shell ionization by relativistic heavy particles is also considered.

  12. 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.

  13. Sub-nanometer dimensions control of core/shell nanoparticles prepared by atomic layer deposition

    International Nuclear Information System (INIS)

    Bimetallic core/shell nanoparticles (NPs) are the subject of intense research due to their unique electronic, optical and catalytic properties. Accurate and independent control over the dimensions of both core and shell would allow for unprecedented catalytic performance. Here, we demonstrate that both core and shell dimensions of Pd/Pt core/shell nanoparticles (NPs) supported on Al2O3 substrates can be controlled at the sub-nanometer level by using a novel strategy based on atomic layer deposition (ALD). From the results it is derived that the main conditions for accurate dimension control of these core/shell NPs are: (i) a difference in surface energy between the deposited core metal and the substrate to obtain island growth; (ii) a process yielding linear growth of the NP cores with ALD cycles to obtain monodispersed NPs with a narrow size distribution; (iii) a selective ALD process for the shell metal yielding a linearly increasing thickness to obtain controllable shell growth exclusively on the cores. For Pd/Pt core/shell NPs it is found that a minimum core diameter of 1 nm exists above which the NP cores are able to catalytically dissociate the precursor molecules for shell growth. In addition, initial studies on the stability of these core/shell NPs have been carried out, and it has been demonstrated that core/shell NPs can be deposited by ALD on high aspect ratio substrates such as nanowire arrays. These achievements show therefore that ALD has significant potential for the preparation of tuneable heterogeneous catalyst systems. (paper)

  14. van der Waals coefficients for positronium interactions with closed-shell atoms

    CERN Document Server

    Swann, A R; Gribakin, G F

    2015-01-01

    The random-phase approximation with exchange (RPAE) is used with a $B$-spline basis to compute dynamic dipole polarizabilities of noble-gas atoms and several other closed-shell atoms (Be, Mg, Ca, Zn, Sr and Cd). From these, values of the van der Waals $C_6$ constants for positronium interactions with these atoms are determined and compared with existing data. Our best predictions of $C_6$ for Ps--noble-gas pairs are expected to be accurate to within 1%, and to within few per cent for the alkaline earths. Implications of increased $C_6$ values for more polarizable atoms are discussed.

  15. Valence and L-shell photoionization of Cl-like argon using R-matrix techniques

    Science.gov (United States)

    Tyndall, N. B.; Ramsbottom, C. A.; Ballance, C. P.; Hibbert, A.

    2016-02-01

    Photoionization cross-sections are obtained using the relativistic Dirac Atomic R-matrix Codes (DARC) for all valence and L-shell energy ranges between 27 and 270 eV. A total of 557 levels arising from the dominant configurations 3s23p4, 3s3p5, 3p6, 3s23p3[3d, 4s, 4p], 3p53d, 3s23p23d2, 3s3p43d, 3s3p33d2 and 2s22p53s23p5 have been included in the target wavefunction representation of the Ar III ion, including up to 4p in the orbital basis. We also performed a smaller Breit-Pauli (BP) calculation containing the lowest 124 levels. Direct comparisons are made with previous theoretical and experimental work for both valence shell and L-shell photoionization. Excellent agreement was found for transitions involving the 2Po initial state to all allowed final states for both calculations across a range of photon energies. A number of resonant states have been identified to help analyse and explain the nature of the spectra at photon energies between 250 and 270 eV.

  16. Valence and L-shell photoionization of Cl-like Argon using R-matrix techniques

    CERN Document Server

    Tyndall, Niall; Ballance, Connor; Hibbert, Alan

    2015-01-01

    Photoionization cross sections are obtained using the relativistic Dirac Atomic R-matrix Codes (DARC) for all valence and L-shell energy ranges between 27-270eV. A total of 557 levels arising from the dominant configurations 3s$^2$3p$^4$, 3s3p$^5$, 3p$^6$, 3s$^2$3p$^3$[3d, 4s, 4p], 3p$^5$3d, 3s$^2$3p$^2$3d$^2$, 3s3p$^4$3d, 3s3p$^3$3d$^2$ and 2s$^2$2p$^5$3s$^2$3p$^5$ have been included in the target wavefunction representation of the Ar III ion, including up to 4p in the orbital basis. We also performed a smaller Breit-Pauli (BP) calculation containing the lowest 124 levels. Direct comparisons are made with previous theoretical and experimental work for both valence shell and L-shell photoionization. Excellent agreement was found for transitions involving the $^2$P$^{\\rm o}$ initial state to all allowed final states for both calculations across a range of photon energies. A number of resonant states have been identified to help analyze and explain the nature of the spectra at photon energies between 250 and 27...

  17. Interference effect in the relativistic inner shell ionization of atoms by electron impact

    International Nuclear Information System (INIS)

    We present in this paper, the results of our calculation of right-left asymmetry in the relativistic (e, 2e) processes for inner K-shell ionization of atoms. The calculation has been performed in plane wave Born approximation (PWBA) using one photon exchange approximation. The triple differential cross section (TDCS), in plane wave Born approximation (PWBA) can be factorized into products of electron kinematic factors and atomic structure functions [Donnely (1984)]. The right left asymmetry in the relativistic (e, 2e) process on the K-shell of the atoms has been shown to depend on the interference between the transition charge and component of the transition current in the scattering plane. Further, we discuss the dependence of right-left asymmetry on the incident electron energy, atomic number of the target and scattering angle. (author)

  18. X-ray emission from heavy atomic collisions : couplings of inner shells in superheavy quasimolecules

    OpenAIRE

    Verma, Punita

    2010-01-01

    Overcritical electromagnetic fields with a coupling strength of ZUA greater than or equal to 1/alpha (=137, with alpha being the fine structure constant) can be experienced in superheavy quasimolecules (atomic number ZUA = Z1+Z2) formed transiently in close collisions of two very heavy atomic partners (Z1, Z2) at velocities (vion) smaller compared to the orbital velocity of the innermost electrons of concern (ve-). The inner shell processes in these collisions are governed approximately by th...

  19. Preliminary structural investigations of the Eut-L shell protein of the ethanolamine ammonia-lyase metabolosome of Escherichia coli

    International Nuclear Information System (INIS)

    Preliminary X-ray analysis of crystals of the bacterial microcompartment shell protein Eut-L from Escherichia coli is reported. The ethanolamine ammonia-lyase microcompartment is composed of five different shell proteins that have been proposed to assemble into symmetrically shaped polyhedral particles of varying sizes. Here, preliminary X-ray analysis of crystals of the bacterial microcompartment shell protein Eut-L from Escherichia coli is reported. Cloning, overexpression and purification resulted in highly pure protein that crystallized readily under many different conditions. In all cases the protein forms thin hexagonal plate-shaped crystals belonging to space group P3 that are of unusually high stability against different solvent conditions. The crystals diffracted to a resolution of 2.0 Å using synchrotron radiation but proved to be radiation-sensitive. Preparations of heavy-atom-derivatized crystals for use in determining the three-dimensional structure are under way

  20. 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

    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.......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...

  1. Photoionization of the valence shells of the neutral tungsten atom

    CERN Document Server

    Ballance, Connor P

    2015-01-01

    Results from large-scale theoretical cross section calculations for the total photoionization of the 4f, 5s, 5p and 6s orbitals of the neutral tungsten atom using the Dirac Coulomb R-matrix approximation (DARC: Dirac-Atomic R-matrix codes) are presented. Comparisons are made with previous theoretical methods and prior experimental measurements. In previous experiments a time-resolved dual laser approach was employed for the photo-absorption of metal vapours and photo-absorption measurements on tungsten in a solid, using synchrotron radiation. The lowest ground state level of neutral tungsten is $\\rm 5p^6 5d^4 6s^2 \\; {^5}D_{\\it J}$, with $\\it J$=0, and requires only a single dipole matrix for photoionization. To make a meaningful comparison with existing experimental measurements, we statistically average the large-scale theoretical PI cross sections from the levels associated with the ground state $\\rm 5p^6 5d^4 6s^2 \\; {^5}D_{\\it J}[{\\it J}=0,1,2,3,4]$ levels and the $\\rm 5d^56s \\; ^7S_3$ excited metastable...

  2. Anomalous elastic scattering of x-ray photon by an atom with an open shell

    International Nuclear Information System (INIS)

    In the non-relativistic approximation for the wavefunctions of the one-electron states and in the dipole approximation for the scattering amplitude the effect of relaxation of atomic shells in the field of core vacancies, multiplet splitting, Auger and radiative vacancy decays and virtual processes of one-photon double excitation/ionization from the atomic ground state on the differential cross section of anomalous elastic scattering of the linearly polarized x-ray photon by the copper atom near its 1s-shell ionization threshold are studied. The results of calculations are found to be in agreement with the high-precision synchrotron radiation experiment by Arp et al (1993 J. Phys. B: At. Mol. Opt. Phys. 26 4381)

  3. Anomalous elastic scattering of x-ray photon by an atom with an open shell

    Energy Technology Data Exchange (ETDEWEB)

    Hopersky, A N; Petrov, I D; Nadolinsky, A M; Yavna, V A; Koneev, R V [Rostov State University of Transport Communication, Chair of Mathematics, Rostov-on-Don, 344038 (Russian Federation)

    2004-08-28

    In the non-relativistic approximation for the wavefunctions of the one-electron states and in the dipole approximation for the scattering amplitude the effect of relaxation of atomic shells in the field of core vacancies, multiplet splitting, Auger and radiative vacancy decays and virtual processes of one-photon double excitation/ionization from the atomic ground state on the differential cross section of anomalous elastic scattering of the linearly polarized x-ray photon by the copper atom near its 1s-shell ionization threshold are studied. The results of calculations are found to be in agreement with the high-precision synchrotron radiation experiment by Arp et al (1993 J. Phys. B: At. Mol. Opt. Phys. 26 4381)

  4. 正电子碰撞Ag,In,Sn原子L壳层电离截面的理论计算%Theoretical calculation of L-shell ionization cross section of Ag, In, and Sn atoms by positron impact

    Institute of Scientific and Technical Information of China (English)

    何彪; 何建新; 易有根; 江少恩; 郑志坚

    2011-01-01

    在David Botz分析模型的基础上,综合考虑正电子及电子碰撞电离的库仑效应和电子交换效应,引入离子效应和相对论效应修正因子,计算了Ag,In,Sn原子的L壳层电离截面.计算结果表明,引入了修正因子的计算结果明显优于平面波波恩近似和扭曲波波恩近似的计算结果,并和最近文献的实验值符合得较好.其计算结果可为激光等离子体模拟提供准确参数.%Based on the analytical formulas of David Botz, considering the Coulomb effect and exchange effect in the ionization by positron and electron impact, the total cross sections of positron-impact Lshell ionization of Ag? In, Sn atomic are calculated by incorporating both ionic and relativistic corrections in it. In comparison with the quantum mechanical predictions of plane-wave and distorted-wave Born approximations, it is found that the improved analytical formulas are in better agreement with the experimental results. The calculated results can be used to simlate the laser plasma.

  5. Discovery of a Shell of Neutral Atomic Hydrogen Surrounding the Carbon Star IRC+10216

    CERN Document Server

    Matthews, L D; Bertre, T Le

    2015-01-01

    We have used the Robert C. Byrd Green Bank Telescope to perform the most sensitive search to date for neutral atomic hydrogen (HI) in the circumstellar envelope (CSE) of the carbon star IRC+10216. Our observations have uncovered a low surface brightness HI shell of diameter ~1300" (~0.8 pc), centered on IRC+10216. The HI shell has an angular extent comparable to the far ultraviolet-emitting astrosphere of IRC+10216 previously detected with the GALEX satellite, and its kinematics are consistent with circumstellar matter that has been decelerated by the local interstellar medium. The shell appears to completely surround the star, but the highest HI column densities are measured along the leading edge of the shell, near the location of a previously identified bow shock. We estimate a total mass of atomic hydrogen associated with IRC+10216 CSE of M_HI~3x10e-3 M_sun. This is only a small fraction of the expected total mass of the CSE (<1%) and is consistent with the bulk of the stellar wind originating in molec...

  6. 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)

  7. Two-photon excitation/ionization of the 1s-shell of the argon atom

    CERN Document Server

    Novikov, S A

    2002-01-01

    The absolute values and the shape of the two-photon excitation/ionization cross section of the 1s-shell of the argon atom are calculated with inclusion of the many-particle effects, i.e., the relaxation of the atomic residue in the field of the vacancies created, and the decay of the vacancies into the channels of Auger and (or) radiative types. The wavefunctions of the one-particle states are calculated in non-relativistic approximation. The calculations are performed for both linear and circular polarization of the laser beam.

  8. Two-photon excitation/ionization of the 1s-shell of the argon atom

    International Nuclear Information System (INIS)

    The absolute values and the shape of the two-photon excitation/ionization cross section of the 1s-shell of the argon atom are calculated with inclusion of the many-particle effects, i.e., the relaxation of the atomic residue in the field of the vacancies created, and the decay of the vacancies into the channels of Auger and (or) radiative types. The wavefunctions of the one-particle states are calculated in non-relativistic approximation. The calculations are performed for both linear and circular polarization of the laser beam.

  9. Core-Shell Magneto-Optical Trap for Alkaline-Earth-Metal-Like Atoms

    CERN Document Server

    Lee, Jeongwon; Noh, Jiho; Mun, Jongchul

    2014-01-01

    We propose and demonstrate a new magneto-optical trap (MOT) for alkaline-earth-metal-like (AEML) atoms where the narrow $^{1}S_{0}\\rightarrow$$^{3}P_{1}$ transition and the broad $^{1}S_{0}\\rightarrow$$^{1}P_{1}$ transition are spatially arranged into a core-shell configuration. Our scheme resolves the main limitations of previously adopted MOT schemes, leading to a significant increase in both the loading rate and the steady state atom number. We apply this scheme to $^{174}$Yb MOT, where we show about a hundred-fold improvement in the loading rate and ten-fold improvement in the steady state atom number compared to reported cases that we know of to date. This technique could be readily extended to other AEML atoms to increase the statistical sensitivity of many different types of precision experiments.

  10. Characterization of Physic nut (Jatropha curcas L.) shells

    NARCIS (Netherlands)

    Wever, Diego; Heeres, H. J.; Broekhuis, Antonius A.

    2012-01-01

    The characterization of Physic nut shells was done using the wet chemical analysis of wood components. The obtained fractions were analyzed using IR, NMR, GPC, ICP and MALDI-TOF mass spectroscopy. TGA was used to determine the fixed carbon (+ash) and water content of the shells. The results of wet c

  11. Study of the K shell photoelectric parameters of Dy, Yb and W atoms using low energy Bremsstrahlung radiation

    Energy Technology Data Exchange (ETDEWEB)

    Hosur, S.B.; Naika, L.R.; Badiger, N.M. [Department of Studies in PhysicsKarnatak University, Dharwad - 580003 (India)

    2011-04-15

    Low energy external Bremsstrahlung (EB) photons were used to estimate the K shell photoelectric parameters; the K shell photoelectric cross section at the K edge, the K shell binding energy, the K shell jump ratio, the K shell jump factors, the Davisson-Kirchner ratio and the K shell oscillator strength for dysprosium (Dy), ytterbium (Yb) and tungsten (W) atoms. The EB photons are produced in the nickel (Ni) target by using the beta particles from a weak beta source of {sup 90}Sr-{sup 90}Y. These photons are made to fall on these elemental targets of our interest and the transmitted spectrum is measured using GMX 10P HPGe detector coupled to an 8K multichannel analyzer. The sharp decrease at the K edge in the measured spectrum is used to determine the K shell photoelectric parameters of these elements. The experimental results are in good agreement with the theoretical values. (authors)

  12. Study of the K shell photoelectric parameters of Dy, Yb and W atoms using low energy Bremsstrahlung radiation

    International Nuclear Information System (INIS)

    Low energy external Bremsstrahlung (EB) photons were used to estimate the K shell photoelectric parameters; the K shell photoelectric cross section at the K edge, the K shell binding energy, the K shell jump ratio, the K shell jump factors, the Davisson-Kirchner ratio and the K shell oscillator strength for dysprosium (Dy), ytterbium (Yb) and tungsten (W) atoms. The EB photons are produced in the nickel (Ni) target by using the beta particles from a weak beta source of 90Sr-90Y. These photons are made to fall on these elemental targets of our interest and the transmitted spectrum is measured using GMX 10P HPGe detector coupled to an 8K multichannel analyzer. The sharp decrease at the K edge in the measured spectrum is used to determine the K shell photoelectric parameters of these elements. The experimental results are in good agreement with the theoretical values. (authors)

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

    International Nuclear Information System (INIS)

    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)

  14. 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. PMID:24837234

  15. Semiempirical Sternheimer shielding factors for the atomic 4f and 5d shells

    International Nuclear Information System (INIS)

    In a recent Physical Review Letter, workers at Los Alamos reported new electric-quadrupole moment values for selected nuclei through study of hfs in the X-ray spectra of muonic atoms. On combining these true moment values with the apparent values previously deduced for the same nuclei from many-electron hfs studies, the authors evaluated Sternheimer shielding factors for several electron shells in various atoms. They were struck by the unreasonably large scatter in the resulting shielding factors. After some study, the authors concluded that the scatter arose from (1) questionable assumptions and procedures used earlier in analyzing the many-electron hfs, and (2) the diversity of methods used in evaluating quadrupole radial hfs integrals. Limiting themselves to the atomic 4f and 5d shells, they made a study of all atoms for which (a) a true quadrupole moment value (i.e. one determined either by muonic hfs or Coulomb excitation) was known and (b) the many-electron hfs had been studied

  16. L/M sub-shell measurements on INDUS-2 beam line BL16

    Energy Technology Data Exchange (ETDEWEB)

    Singla, Raj Mittal, E-mail: rmsingla@yahoo.com [Nuclear Science Laboratories, Physics Department, Punjabi University, Patiala -147002 (India)

    2015-06-24

    Beamline BL-16 on INDUS-2 at RRCAT, Indore has been employed for M sub shell measurements on Pt, Au, Hg, Pb, Th and U at 8 and 10 keV photon energies to determine M sub-shell X-ray emission cross-sections and for L sub-shell measurements on Dy, Ho, Er, Lu, Ta, W, Pt, Au, Hg, Pb and Bi with selective creation of electron vacancies in individual sub-shells to derive L Coster-Kronig (CK) yield values. The cross sections have been measured for the first time. The determined L sub-shell CK yields were used to explore some details of CK transitions.

  17. L/M sub-shell measurements on INDUS-2 beam line BL16

    International Nuclear Information System (INIS)

    Beamline BL-16 on INDUS-2 at RRCAT, Indore has been employed for M sub shell measurements on Pt, Au, Hg, Pb, Th and U at 8 and 10 keV photon energies to determine M sub-shell X-ray emission cross-sections and for L sub-shell measurements on Dy, Ho, Er, Lu, Ta, W, Pt, Au, Hg, Pb and Bi with selective creation of electron vacancies in individual sub-shells to derive L Coster-Kronig (CK) yield values. The cross sections have been measured for the first time. The determined L sub-shell CK yields were used to explore some details of CK transitions

  18. L-shell ionization in high-z targets by carbon and silicon ions

    International Nuclear Information System (INIS)

    L-shell ionization in Ho, Er, Tm, Ta, W, Tl, Pb and Bi by 20 Mev carbon ions and 37.5 Mev silicon ions has been investigated. The observed L/sub //alpha/sub L//gamma/ x-ray intensity ratios are compared with the estimates based on PWBA and BEA calculations. The energy shifts in the L/sub //alpha/, L/sub //gamma/sub //1 and L/sub //gamma/sub //4 x-rays are attributed to the presence of M shell spectator vacancies. 7 refs

  19. On the angular distribution and spin polarization of the photoelectrons from semi-filled shell atoms

    CERN Document Server

    Amusia, M Ya

    2007-01-01

    We present here the results of calculations of photoelectrons' angular anisotropy and spin-polarization parameters for a number of semi-filled shell atoms. We consider ionization of outer or in some cases next to the outer electrons in a number of elements from I, V, and VI groups of the Periodic Table. All calculations are performed with account of multi-electron correlations in the frame of the Spin Polarized version of the Random Phase Approximation with Exchange - SP RPAE. We consider the dipole angular distribution and spin polarization of photoelectrons from semi-filled subshells and from closed shells that are neighbors to the semi-filled shells. We have considered also angular anisotropy and spin-polarization of photoelectrons from some excited atoms that are formed by spin-flip of one of the outer electrons. To check the accuracy and consistency of the applied SP RPAE approach and to see the role of the nuclear charge variation only, we have calculated the dipole angular anisotropy and spin-polarizat...

  20. Empirical and semi-empirical interpolation of L X-ray fluorescence parameters for elements in the atomic range 50≤Z≤92

    International Nuclear Information System (INIS)

    In this study, interpolations (empirical and semi-empirical) of L sub-shell fluorescence yield and L shell Coster–Kronig transition probability values and the measured L X-ray production cross-sections, intensity ratios and L sub-shell fluorescence yield values of elements have been performed in the range of 50≤Z≤92. In this experimental setup, two sources (50 mCi 55Fe and 50 mCi 241Am) were used. L X-rays emitted by samples were counted by an Ultra-LEGe detector with a resolution of 150 eV at 5.9 keV. - Highlights: • This work was performed for the elements having the atomic numbers between 50 and 92. • Experimental L-shell fluorescence parameters were investigated. • New fit values of L subshell fluorescence and Coster–Kronig yield were presented

  1. L-Shell X-Ray Yields and Production Cross Sections of Zr and Mo Bombarded by Slow Highly Charged Ar16+ Ions

    International Nuclear Information System (INIS)

    The L-shell x-ray yields of Zr and Mo bombarded by slow Ar16+ions are measured. The energy of the Ar16+ions ranges from about 150 keV to 350 keV. The L-shell x-ray production cross sections of Zr and Mo are extracted from these yields data. The explanation of these experimental results is in the framework of the adiabatic direct-ionization and the binding energy modified BEA approximation. We consider, in the slow asymmetric collisions such as Ar and Mo/Zr, the transient united atoms (UA) are formed during the ion-surface interaction and the direct-ionization is the main mechanism for the inner-shell vacancy production. Generally, the theoretical results are in good agreement with the experimental data. (atomic and molecular physics)

  2. Determination of the K shell oscillator strengths and the imaginary form factors of atoms using a weak beta source

    Energy Technology Data Exchange (ETDEWEB)

    Hosur, Savita B; Badiger, N M; Naik, L R [Department of Physics, Karnatak University, Dharwad-580 003 (India)], E-mail: nagappa123@yahoo.co.in

    2008-05-14

    The K shell oscillator strengths and the imaginary form factors of Gd, Hf and Ta atoms have been determined using a novel method. In this method, bremsstrahlung photons produced by beta particles from a weak beta source of {sup 90}Sr-{sup 90}Y in a nickel foil are incident on an elemental target and the transmitted spectrum of photons emerging from the target is measured using an ORTEC make HPGe detector coupled to 8 K multichannel analyser. The recorded spectrum shows a sudden drop at the K shell binding energy of the target atom and an exponential decrease in the intensity above the K shell binding energy. These portions have been used to determine the K shell binding energy, photoelectric cross-section at the K edge, the K shell oscillator strength and the imaginary form factor of the elements Gd, Hf and Ta. Good agreement between the experimental and the theoretical values is observed.

  3. Determination of the K shell oscillator strengths and the imaginary form factors of atoms using a weak beta source

    International Nuclear Information System (INIS)

    The K shell oscillator strengths and the imaginary form factors of Gd, Hf and Ta atoms have been determined using a novel method. In this method, bremsstrahlung photons produced by beta particles from a weak beta source of 90Sr-90Y in a nickel foil are incident on an elemental target and the transmitted spectrum of photons emerging from the target is measured using an ORTEC make HPGe detector coupled to 8 K multichannel analyser. The recorded spectrum shows a sudden drop at the K shell binding energy of the target atom and an exponential decrease in the intensity above the K shell binding energy. These portions have been used to determine the K shell binding energy, photoelectric cross-section at the K edge, the K shell oscillator strength and the imaginary form factor of the elements Gd, Hf and Ta. Good agreement between the experimental and the theoretical values is observed

  4. ESR Dosimetry for Atomic Bomb Survivors Using Shell Buttons and Tooth Enamel

    Science.gov (United States)

    Ikeya, Motoji; Miyajima, Junko; Okajima, Shunzo

    1984-09-01

    Atomic bomb radiation doses to humans at Nagasaki and Hiroshima are investigated by electron spin resonance (ESR) from shell buttons and tooth enamel voluntarily supplied by survivors. A shell button gives a dose of 2.1± 0.2 Gy with ESR signals at g=2.001 and g=1.997 while the signal at g=1.997 for the tooth enamel of the same person is 1.9± 0.5 Gy. Other teeth show doses from about 0.5 Gy to 3 Gy. An apparent shielding converted to a concrete thickness is given using the T65D calculated in 1965. Teeth extracted during dental treatment should be preserved for cumulative radiation dosimetry.

  5. Relativistic calculations of double $K$-shell photoionization for neutral medium-$Z$ atoms

    CERN Document Server

    Yerokhin, V A; Fritzsche, S

    2014-01-01

    Fully relativistic calculations are presented for the double $K$-shell photoionization cross section for several neutral medium-$Z$ atoms, from magnesium ($Z = 10$) up to silver ($Z = 47$). The calculations take into account all multipoles of the absorbed photon as well as the retardation of the electron-electron interaction. The approach is based on the partial-wave representation of the Dirac continuum states and uses the Green-function technique to represent the full Dirac spectrum of intermediate states. The method is strictly gauge invariant, which is used as an independent cross check of the computational procedure. The calculated ratios of the double-to-single $K$-shell ionization cross sections are compared with the experimental data and with previous computations.

  6. Prospects for ultracold polar and magnetic chromium-closed-shell-atom molecules

    CERN Document Server

    Tomza, Michał

    2013-01-01

    The properties of the electronic ground state of the polar and paramagnetic chromium--closed-shell-atom molecules have been investigated. State-of-the-art \\textit{ab initio} techniques have been applied to compute the potential energy curves for the chromium--alkaline-earth-metal-atom, CrX (X = Be, Mg, Ca, Sr, Ba), and chromium--ytterbium, CrYb, molecules in the Born-Oppenheimer approximation for the $X^7\\Sigma^+$ high-spin electronic ground state. The spin restricted open-shell coupled cluster method restricted to single, double, and noniterative triple excitations, RCCSD(T), was employed and the scalar relativistic effects within Douglas-Kroll-Hess Hamiltonian or energy-consistent pseudopotentials were included. The permanent electric dipole moments and static electric dipole polarizabilities were computed. The leading long-range coefficients describing the dispersion interaction between atoms at large interatomic distances, $C_6$, are also reported. Molecules under investigation are an example of species p...

  7. Accurate evaluation of magnetic coupling between atoms with numerous open shells: An ab initio method

    Science.gov (United States)

    Gellé, A.; Varignon, J.; Lepetit, M.-B.

    2009-11-01

    We propose a new ab initio method designed for the accurate calculation of effective exchange integrals between atoms with numerous open shells. This method applies to ferromagnetic as well as antiferromagnetic exchange, direct or ligand-mediated exchange. Test calculations on high spin transition metal oxides such as KNiF3, Ba2CoS3 or YMnO3 exhibit a very good accuracy compared either to the best ab initio calculations —when those are feasible— and with experimental evaluations.

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

    International Nuclear Information System (INIS)

    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

  9. 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

    We present a facile synthesis protocol for atomically thin platinum (Pt) shells on top of gold (Au) nanoparticles (NPs) (Au@PtNPs) in one pot under mild conditions. The Au@PtNPs exhibited remarkable stability (> 2 years) at room temperature. The synthesis, bimetallic nanostructures and catalytic...... 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 < 5 nm PtNP catalyst. Excellent...

  10. Atomically thin spherical shell-shaped superscatterers based on Bohr model

    CERN Document Server

    Li, Rujiang; Lin, Shisheng; Liu, Xu; Chen, Hongsheng

    2015-01-01

    Graphene monolayers can be used for atomically thin three-dimensional shell-shaped superscatterer designs. Due to the excitation of the first-order resonance of transverse magnetic (TM) graphene plasmons, the scattering cross section of the bare subwavelength dielectric particle is enhanced significantly by five orders of magnitude. The superscattering phenomenon can be intuitively understood and interpreted with Bohr model. Besides, based on the analysis of Bohr model, it is shown that contrary to the TM case, superscattering is hard to occur by exciting the resonance of transverse electric (TE) graphene plasmons due to their poor field confinements.

  11. Fermi orbital derivatives in self-interaction corrected density functional theory: Applications to closed shell atoms.

    Science.gov (United States)

    Pederson, Mark R

    2015-02-14

    A recent modification of the Perdew-Zunger self-interaction-correction to the density-functional formalism has provided a framework for explicitly restoring unitary invariance to the expression for the total energy. The formalism depends upon construction of Löwdin orthonormalized Fermi-orbitals which parametrically depend on variational quasi-classical electronic positions. Derivatives of these quasi-classical electronic positions, required for efficient minimization of the self-interaction corrected energy, are derived and tested, here, on atoms. Total energies and ionization energies in closed-shell singlet atoms, where correlation is less important, using the Perdew-Wang 1992 Local Density Approximation (PW92) functional, are in good agreement with experiment and non-relativistic quantum-Monte-Carlo results albeit slightly too low. PMID:25681892

  12. Fermi Orbital Derivatives in Self-Interaction Corrected Density Functional Theory: Applications to Closed Shell Atoms

    CERN Document Server

    Pederson, Mark R

    2014-01-01

    A recent modification of the Perdew-Zunger self-interaction-correction (SIC) to the density-functional formalism (Pederson, Ruzsinszky, Perdew) has provided a framework for explicitly restoring unitary invariance to the expression for the total energy. The formalism depends upon construction of Lowdin orthonormalized Fermi-orbitals (Luken et al) which parametrically depend on variational quasi-classical electronic positions. Derivatives of these quasi-classical electronic positions, required for efficient minimization of the self-interaction corrected energy, are derived and tested here on atoms. Total energies and ionization energies in closed-shell atoms, where correlation is less important, using the PW92 LDA functional are in very good to excellent agreement with experiment and non-relativistic Quantum-Monte-Carlo (QMC) results.

  13. Atomic force microscopy indentation to determine mechanical property for polystyrene–silica core–shell hybrid particles with controlled shell thickness

    International Nuclear Information System (INIS)

    The positively charged polystyrene (PS) particles with a size of ca. 200 nm were synthesized by soap-free polymerization. The PS cores were coated with silica shells of tunable thickness employing the modified Stöber method. The PS cores were removed by thermal decomposition at 500 °C, resulting in well-defined silica hollow spheres (10–30 nm in shell thickness). The elastic response of the as-synthesized samples was probed by an atomic force microscope (AFM). A point load was applied to the particle surface through a sharp AFM tip, and the force–displacement curves were recorded. Elastic moduli (E) for the PS particles (2.01 ± 0.70 GPa) and the core–shell structured hybrid particles were determined on the basis of Hertzian contact model. The calculated E values of composites exhibited a linear dependence on the silica shell thickness. While the shell thickness increased from ca. 10 to 15 and 20 nm, the E values of composites increased from 4.42 ± 0.27 to 5.88 ± 0.48 and 9.07 ± 0.94 GPa. For core–shell structured organic/inorganic composites, the E values of the hybrid particles were much lower than those of inorganic shells, while these values were much close to those of organic cores. Moreover, the moduli of elasticity of the composites appeared to be determined by the properties of the polymer cores, the species of inorganic shells and the thickness of shells. Besides, the inorganic shells enhanced the mechanical properties of the polymer cores. This work will provide essential experimental and theoretical basis for the design and application of core–shell structured organic/inorganic composite abrasives in chemical mechanical polishing/planarization. - Highlights: • The elastic moduli (E) of the PS/SiO2 hybrid particles were probed by AFM. • The E values of composites exhibited a linear dependence on the shell thickness. • The elasticity appeared to be determined by the properties of the organic cores. • The E values were affected by the

  14. Atomic force microscopy indentation to determine mechanical property for polystyrene–silica core–shell hybrid particles with controlled shell thickness

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Yang, E-mail: cy.jpu@126.com [School of Materials Science and Engineering, Changzhou University, Changzhou, Jiangsu 213164 (China); Qian, Cheng [School of Materials Science and Engineering, Changzhou University, Changzhou, Jiangsu 213164 (China); Miao, Naiming [School of Mechanical Engineering, Changzhou University, Changzhou, Jiangsu 213016 (China)

    2015-03-31

    The positively charged polystyrene (PS) particles with a size of ca. 200 nm were synthesized by soap-free polymerization. The PS cores were coated with silica shells of tunable thickness employing the modified Stöber method. The PS cores were removed by thermal decomposition at 500 °C, resulting in well-defined silica hollow spheres (10–30 nm in shell thickness). The elastic response of the as-synthesized samples was probed by an atomic force microscope (AFM). A point load was applied to the particle surface through a sharp AFM tip, and the force–displacement curves were recorded. Elastic moduli (E) for the PS particles (2.01 ± 0.70 GPa) and the core–shell structured hybrid particles were determined on the basis of Hertzian contact model. The calculated E values of composites exhibited a linear dependence on the silica shell thickness. While the shell thickness increased from ca. 10 to 15 and 20 nm, the E values of composites increased from 4.42 ± 0.27 to 5.88 ± 0.48 and 9.07 ± 0.94 GPa. For core–shell structured organic/inorganic composites, the E values of the hybrid particles were much lower than those of inorganic shells, while these values were much close to those of organic cores. Moreover, the moduli of elasticity of the composites appeared to be determined by the properties of the polymer cores, the species of inorganic shells and the thickness of shells. Besides, the inorganic shells enhanced the mechanical properties of the polymer cores. This work will provide essential experimental and theoretical basis for the design and application of core–shell structured organic/inorganic composite abrasives in chemical mechanical polishing/planarization. - Highlights: • The elastic moduli (E) of the PS/SiO{sub 2} hybrid particles were probed by AFM. • The E values of composites exhibited a linear dependence on the shell thickness. • The elasticity appeared to be determined by the properties of the organic cores. • The E values were affected

  15. L-shell x-ray fluorescence computed tomography (XFCT) imaging of Cisplatin

    International Nuclear Information System (INIS)

    X-ray fluorescence computed tomography (XFCT) imaging has been focused on the detection of K-shell x-rays. The potential utility of L-shell x-ray XFCT is, however, not well studied. Here we report the first Monte Carlo (MC) simulation of preclinical L-shell XFCT imaging of Cisplatin. We built MC models for both L- and K-shell XFCT with different excitation energies (15 and 30 keV for L-shell and 80 keV for K-shell XFCT). Two small-animal sized imaging phantoms of 2 and 4 cm diameter containing a series of objects of 0.6 to 2.7 mm in diameter at 0.7 to 16 mm depths with 10 to 250 µg mL−1 concentrations of Pt are used in the study. Transmitted and scattered x-rays were collected with photon-integrating transmission detector and photon-counting detector arc, respectively. Collected data were rearranged into XFCT and transmission CT sinograms for image reconstruction. XFCT images were reconstructed with filtered back-projection and with iterative maximum-likelihood expectation maximization without and with attenuation correction. While K-shell XFCT was capable of providing an accurate measurement of Cisplatin concentration, its sensitivity was 4.4 and 3.0 times lower than that of L-shell XFCT with 15 keV excitation beam for the 2 cm and 4 cm diameter phantom, respectively. With the inclusion of excitation and fluorescence beam attenuation correction, we found that L-shell XFCT was capable of providing fairly accurate information of Cisplatin concentration distribution. With a dose of 29 and 58 mGy, clinically relevant Cisplatin Pt concentrations of 10 µg mg−1 could be imaged with L-shell XFCT inside a 2 cm and 4 cm diameter object, respectively. (paper)

  16. L-Shell X-Ray Yields and Production Cross Sections of Zr and Mo Bombarded by Slow Highly Charged Ar16+ Ions

    Institute of Scientific and Technical Information of China (English)

    XU Jin-Zhang; DU Juan; CHEN Xi-Meng; SHAO Jian-Xiong; YANG Zhi-Hu; CUI Ying; GAO Zhi-Min; LIU Yu-Wen

    2008-01-01

    The L-shell x-ray yields of Zr and Mo bombarded by slow Ar16+ ions are measured.The energy of the Ar16+ ions ranges from about 150 keV to 350 keV.The L-shell x-ray production cross sections of Zr and Mo are extracted from these yields data.The explanation of these experimental results is in the framework of the adiabatic directionization and the binding energy modified BEA approximation.We consider,in the slow asymmetric collisions such as Ar and Mo/Zr,the transient united atoms (UA) are formed during the ion-surface interaction and the direct-ionization is the main mechanism for the inner-shell vacancy production.Generally,the theoretical results are in good agreement with the experimental data.

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

    International Nuclear Information System (INIS)

    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. (author)

  18. Relativistic Equation of Motion Coupled-Cluster Method: Application to the closed-shell atomic systems

    CERN Document Server

    Pathak, Himadri; Das, B P; Vaval, Nayana; Pal, Sourav

    2014-01-01

    We report our successful implementation of the full fledged relativistic equation of motion coupled cluster (EOMCC) method. This method is employed to compute the principal ionization potentials (IPs) of closed-shell rare gas atoms, He-like ions, Be-like ions along with Na+, Al+, K+, Be, and Mg. Four component Dirac spinors are used in the calculations and the one and two electron integrals are evaluated using the Dirac Coulomb Hamiltonian. Our results are in excellent agreement with those available measurements, which are taken from the National Institute of Science and Technology database (NIST). We also present results using the second order many-body perturbation theory (MBPT(2)) and random phase approximation (RPA) in the EOMCC framework. These results are compared with those of EOMCC at the level of single and double excitations in order to assess the role of the electron correlation effects in the intermediate schemes considered in our calculations .

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

    International Nuclear Information System (INIS)

    A method was developed to calculate the transition rate for two-electron one-photon K(sub αα) transition (2s 2p → 1s2). 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)

  20. L shell X-ray fluorescence parameters of Pb in phthalocyanine complexes

    International Nuclear Information System (INIS)

    The L shell X-ray intensity ratios Li/Lα (i=l, β and γ), the production cross-sections σLi (i=l, α, β and γ) and the L3 subshell fluorescence yields ωL3 have been investigated for the element Pb in the phthalocyanine complexes. The measurements have been performed using an 241Am annular radioactive source and an Ultra-LEGe detector with a resolution of 150 eV at 5.9 keV. The experimental values have been compared with the theoretical values of pure Pb element. - Highlights: • The L shell XRF parameters of Pb in the phthalocyanine complexes were investigated. • These parameters were obtained using EDXRF method. • The results are agreement with the theoretical values

  1. High Precision {\\it K}-Shell Photoabsorption Cross Sections for Atomic Oxygen: Experiment and Theory

    CERN Document Server

    McLaughlin, B M; Bowen, K P; Gardenghi, D J; Stolte, W C

    2013-01-01

    Photoabsorption of atomic oxygen in the energy region below the $\\rm 1s^{-1}$ threshold in x-ray spectroscopy from {\\it Chandra} and {\\it XMM-Newton} is observed in a variety of x-ray binary spectra. Photoabsorption cross sections determined from an R-matrix method with pseudo-states (RMPS) and new, high precision measurements from the Advanced Light Source (ALS) are presented. High-resolution spectroscopy with E/$\\Delta$E $\\approx$ 4,250 $\\pm$ 400 was obtained for photon energies from 520 eV to 555 eV at an energy resolution of 124 $\\pm$ 12 meV FWHM. {\\it K}-shell photoabsorption cross-section measurements were made with a re-analysis of previous experimental data on atomic oxygen at the ALS. Natural linewidths $\\Gamma$ are extracted for the $\\rm 1s^{-1}2s^22p^4 (^4P)np ^3P^{\\circ}$ and $\\rm 1s^{-1}2s^22p^4(^2P)np ~^3P^{\\circ}$ Rydberg resonances series and compared with theoretical predictions. Accurate cross sections and linewidths are obtained for applications in x-ray astronomy. Excellent agreement betwe...

  2. Discovery of K-Shell Emission Lines of Neutral Atoms in the Galactic Center Region

    CERN Document Server

    Nobukawa, Masayoshi; Tsuru, Takeshi Go; Ryu, Syukyo G; Tatischeff, Vincent

    2010-01-01

    The K-shell emission line of neutral irons from the Galactic center (GC) region is one of the key for the structure and activity of the GC. The origin is still open question, but possibly due either to X-ray radiation or to electron bombarding to neutral atoms. To address this issue, we analyzed the Suzaku X-ray spectrum from the GC region of intense neutral iron line emission, and report on the discovery of Kalpha lines of neutral argon, calcium, chrome, and manganese atoms. The equivalent widths of these Kalpha lines indicate that the metal abundances in the GC region should be ~1.6 and ~4 of solar value, depending on the X-ray and the electron origins, respectively. On the other hand, the metal abundances in the hot plasma in the GC region are found to be ~1-2 solar. These results favor that the origin of the neutral Kalpha lines are due to X-ray irradiation.

  3. Two Large HI Shells in the Outer Galaxy near l=279 degrees

    CERN Document Server

    McClure-Griffiths, N M; Gaensler, B M; Green, A J; Haynes, R F; Wieringa, M H; Dickey, John M.

    2000-01-01

    As part of a survey of HI 21-cm emission in the Southern Milky Way, we have detected two large shells in the interstellar neutral hydrogen near l=279 deg. The center velocities are +36 and +59 km/s, which puts the shells at kinematic distances of 7 and 10 kpc. The larger shell is about 610 pc in diameter and very empty, with density contrast of at least 15 between the middle and the shell walls. It has expansion velocity of about 20 km/s and swept up mass of several million solar masses. The energy indicated by the expansion may be as high as 2.4 X 10^53 ergs. We estimate its age to be 15 to 20 million years. The smaller shell has diameter of about 400 pc, expansion velocity about 10 km/s and swept up mass of about 10^6 solar masses. Morphologically both regions appear to be shells, with high density regions mostly surrounding the voids, although the first appears to have channels of low density which connect with the halo above and below the HI layer. They lie on the edge of the Carina arm, which suggests th...

  4. MEASUREMENT OF L-SHELL IONIZATION CROSS SECTIONS FOR NIOBIUM BY ELECTRON IMPACT

    Institute of Scientific and Technical Information of China (English)

    PENG XIU-FENG; HE FU-QING; LONG XIAN-GUAN; AN ZHU; LUO ZHENG-MING

    2001-01-01

    L-shell ionization cross sections of Nb by electron impact in the energy range from 3 to 40 keV have been determined with a Si(Li) X-ray detector. Influence of reflected electrons from backing on the measurement was corrected using an electron transport model. The experimental results are compared with theoretical calculations of Gryzinski and McGuire.

  5. 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.

  6. Quantum-Shell Corrections to the Finite-Temperature Thomas-Fermi-Dirac Statistical Model of the Atom

    Energy Technology Data Exchange (ETDEWEB)

    Ritchie, A B

    2003-07-22

    Quantum-shell corrections are made directly to the finite-temperature Thomas-Fermi-Dirac statistical model of the atom by a partition of the electronic density into bound and free components. The bound component is calculated using analytic basis functions whose parameters are chosen to minimize the energy. Poisson's equation is solved for the modified density, thereby avoiding the need to solve Schroedinger's equation for a self-consistent field. The shock Hugoniot is calculated for aluminum: shell effects characteristic of quantum self-consistent field models are fully captures by the present model.

  7. Fluidized-bed atomic layer deposition reactor for the synthesis of core-shell nanoparticles

    International Nuclear Information System (INIS)

    The design of a fluidized bed atomic layer deposition (ALD) reactor is described in detail. The reactor consists of three parts that have all been placed in one protective cabinet: precursor dosing, reactor, and residual gas treatment section. In the precursor dosing section, the chemicals needed for the ALD reaction are injected into the carrier gas using different methods for different precursors. The reactor section is designed in such a way that a homogeneous fluidized bed can be obtained with a constant, actively controlled, reactor pressure. Furthermore, no filters are required inside the reactor chamber, minimizing the risk of pressure increase due to fouling. The residual gas treatment section consists of a decomposition furnace to remove residual precursor and a particle filter and is installed to protect the pump. In order to demonstrate the performance of the reactor, SiO2 particles have been coated with TiO2 using tetrakis-dimethylamino titanium (TDMAT) and H2O as precursors. Experiments with varying pulse times show that saturated growth can be obtained with TDMAT pulse times larger than 600 s. Analysis of the powder with High-Angle Annular Dark-Field Scanning Transmission Electron Microscopy (HAADF-STEM) and energy dispersive X-ray spectroscopy confirmed that after 50 cycles, all SiO2 particles were coated with a 1.6 nm homogenous shell of TiO2

  8. Spectroscopic investigations of L-shell ionization in heavy elements by electron impact

    Science.gov (United States)

    Rahangdale, H. V.; Mitra, D.; Das, P. K.; De, S.; Guerra, M.; Santos, J. P.; Saha, S.

    2016-05-01

    The absolute L subshell specific electron impact ionization cross sections near the ionization threshold (16 model. The sensitivity of the results on the atomic parameters is explored. Observed agreements and discrepancies between the experimental results and theoretical estimates, and their dependence on the specific atomic parameters are reported.

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

    International Nuclear Information System (INIS)

    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

  10. Inner-shell corrections to the Bethe stopping-power formula evaluated from a realistic atomic model

    International Nuclear Information System (INIS)

    Generalized oscillator strengths for K- and L-shell ionization have been calculated using a central potential derived from the Hartree-Slater model. In cases in which an ejected electron carries low kinetic energies, sizable differences with hydrogenic-model calculations are evident

  11. Vapor generation and atom traps: Atomic absorption spectrometry at the ng/L level

    International Nuclear Information System (INIS)

    Atom-trapping atomic absorption spectrometry is a technique that allows detection at the ng/L level for several analytes such as As, Se, Sb, Pb, Bi, Cd, In, Tl, Te, Sn and Hg. The principle involves generation of volatile species, usually hydrides, trapping these species on the surface of an atom trap held at an optimized temperature and, finally, revolatilizing the analyte species by rapid heating of the trap and transporting them in a carrier gas to a heated quartz tube, as commonly used with hydride generation AAS systems. A transient signal having, in most cases, a full width at half maximum of less than 1 s is obtained. The atom trap may be a quartz surface or a W-coil; the former is heated externally and the latter is heated resistively. Both collection and revolatilization temperatures are optimized. In some cases, the W-coil itself is used as an electrothermal atomizer and a heated quartz tube is then not needed. The evolution of these traps starts with the well-known Watling's slotted quartz tube (SQT), continues with atom trapping SQT and finally reaches the present traps mentioned above. The analytical figures of merit for these traps need to be standardized. Naturally, enhancement is on characteristic concentration, C0, where the change in characteristic mass, m0, can be related to trapping efficiency. Novel terms are suggested for E, enhancement factor; such as Emax, maximum enhancement factor; Et, enhancement for 1.0 minute sampling and Ev, enhancement for 1.0 mL of sample. These figures will allow easy comparison of results from different laboratories as well as different analytes and/or traps

  12. Vapor generation and atom traps: Atomic absorption spectrometry at the ng/L level

    Energy Technology Data Exchange (ETDEWEB)

    Ataman, O. Yavuz [Department of Chemistry, Middle East Technical University, 06531 Ankara (Turkey)], E-mail: ataman@metu.edu.tr

    2008-08-15

    Atom-trapping atomic absorption spectrometry is a technique that allows detection at the ng/L level for several analytes such as As, Se, Sb, Pb, Bi, Cd, In, Tl, Te, Sn and Hg. The principle involves generation of volatile species, usually hydrides, trapping these species on the surface of an atom trap held at an optimized temperature and, finally, revolatilizing the analyte species by rapid heating of the trap and transporting them in a carrier gas to a heated quartz tube, as commonly used with hydride generation AAS systems. A transient signal having, in most cases, a full width at half maximum of less than 1 s is obtained. The atom trap may be a quartz surface or a W-coil; the former is heated externally and the latter is heated resistively. Both collection and revolatilization temperatures are optimized. In some cases, the W-coil itself is used as an electrothermal atomizer and a heated quartz tube is then not needed. The evolution of these traps starts with the well-known Watling's slotted quartz tube (SQT), continues with atom trapping SQT and finally reaches the present traps mentioned above. The analytical figures of merit for these traps need to be standardized. Naturally, enhancement is on characteristic concentration, C{sub 0}, where the change in characteristic mass, m{sub 0}, can be related to trapping efficiency. Novel terms are suggested for E, enhancement factor; such as E{sub max}, maximum enhancement factor; E{sub t}, enhancement for 1.0 minute sampling and E{sub v}, enhancement for 1.0 mL of sample. These figures will allow easy comparison of results from different laboratories as well as different analytes and/or traps.

  13. Vapor generation and atom traps: Atomic absorption spectrometry at the ng/L level

    Science.gov (United States)

    Ataman, O. Yavuz

    2008-08-01

    Atom-trapping atomic absorption spectrometry is a technique that allows detection at the ng/L level for several analytes such as As, Se, Sb, Pb, Bi, Cd, In, Tl, Te, Sn and Hg. The principle involves generation of volatile species, usually hydrides, trapping these species on the surface of an atom trap held at an optimized temperature and, finally, revolatilizing the analyte species by rapid heating of the trap and transporting them in a carrier gas to a heated quartz tube, as commonly used with hydride generation AAS systems. A transient signal having, in most cases, a full width at half maximum of less than 1 s is obtained. The atom trap may be a quartz surface or a W-coil; the former is heated externally and the latter is heated resistively. Both collection and revolatilization temperatures are optimized. In some cases, the W-coil itself is used as an electrothermal atomizer and a heated quartz tube is then not needed. The evolution of these traps starts with the well-known Watling's slotted quartz tube (SQT), continues with atom trapping SQT and finally reaches the present traps mentioned above. The analytical figures of merit for these traps need to be standardized. Naturally, enhancement is on characteristic concentration, C0, where the change in characteristic mass, m0, can be related to trapping efficiency. Novel terms are suggested for E, enhancement factor; such as Emax, maximum enhancement factor; Et, enhancement for 1.0 minute sampling and Ev, enhancement for 1.0 mL of sample. These figures will allow easy comparison of results from different laboratories as well as different analytes and/or traps.

  14. L-shell cross section within corrected ECPSSR theory and updated experimental data

    Science.gov (United States)

    Derradj, I.; Kahoul, A.; Deghfel, B.; Bendjedi, A.; Khalfallah, F.; Sahnoune, Y.; Bentabet, A.; Nekkab, M.

    2016-04-01

    The aim of this contribution is to investigate the inclusion of the correct exact integration limits for momentum transfer on ECPSSR theory for a wide range of elements (18≤Z≤92) by proton impact with energy up to 10.0 MeV and its effect on deducing a reliable semi-empirical method for calculating L shell x-ray production and ionization cross sections. A comparison is made with earlier theoretical and experimental results.

  15. Models for inner-shell excitation in ion-atom collisions

    International Nuclear Information System (INIS)

    Models of inner-shell vacancy production which include translation factors are developed for the change transfer process in ion-atom collisions. Translation factors are included in the basis set in which the electronic wavefunction is expanded in order to correctly describe the motion of the electron during the collision. Though several numerical studies have been done which employ this concept, the present models for change exchange are based on stationary state expansions. First the problem is formulated in the adiabatic framework. Having chosen a case in which the form of the translation factors is simple and in which additional approximations may be made, i.e., the case of long-range coupling, all terms in the equations of motion can be evaluated in closed form. An analytic solution is derived with the adiabatic theory which shows explicitly the effects of translation factors on the sharing ratio (defined as the ratio of vacancy production cross-sections of the high Z to low Z partners). The result reduces to that of the Demkov model in the low velocity limit. As the velocity increases, a sharing ratio is predicted which drops below the Demkov curve and reaches a maximum at finite velocity. Numerical calculations using translation factors in a molecular orbital basis exhibit such a fall-off. It is shown that this effect is due solely to the inclusion of the momentum transfer of the electron. The assumptions of the adiabatic approach, however, limit its application to the low velocity region. A new formulation is developed of the problem which is not limited by the adiabatic assumptions. Solutions of the equations of motion in closed form are obtained. This new treatment gives not only the correct adiabatic limit but also the exact Born result directly from the analytic solution of the coupled equations

  16. Theoretical and experimental determination of L -shell decay rates, line widths, and fluorescence yields in Ge

    Science.gov (United States)

    Guerra, M.; Sampaio, J. M.; Madeira, T. I.; Parente, F.; Indelicato, P.; Marques, J. P.; Santos, J. P.; Hoszowska, J.; Dousse, J.-Cl.; Loperetti, L.; Zeeshan, F.; Müller, M.; Unterumsberger, R.; Beckhoff, B.

    2015-08-01

    Fluorescence yields (FYs) for the Ge L shell were determined by a theoretical and two experimental groups within the framework of the International Initiative on X-Ray Fundamental Parameters Collaboration. Calculations were performed using the Dirac-Fock method, including relativistic and QED corrections. The experimental value of the L3FY ωL 3 was determined at the Physikalisch-Technische Bundesanstalt undulator beamline of the synchrotron radiation facility BESSY II in Berlin, Germany, and the L α1 ,2 and L β1 line widths were measured at the Swiss Light Source, Paul Scherrer Institute, Switzerland, using monochromatized synchrotron radiation and a von Hamos x-ray crystal spectrometer. The measured fluorescence yields and line widths are compared to the corresponding calculated values.

  17. Analysis of the simultaneous measurements of iron K- and L-shell radiation from ultrashort laser produced plasmas

    International Nuclear Information System (INIS)

    High resolution x-ray spectra of plasmas produced by the interaction of Ti:Sa laser pulses (duration from 60 fs to 1 ps, and energy from 15 to 128 mJ) with a solid iron target are investigated. Interestingly, both L-shell and K-shell Fe spectra were simultaneously measured using a focusing spectrometer with spatial resolution. In particular, the L-shell Fe radiation from F-, Ne-, and Na-like ions between ∼14-16.3 A were observed from the first-order reflection with a mica crystal. Simultaneously measured alongside the L-shell radiation was the Fe cold Kα lines (∼1.94 A), from eighth-order reflection. Two non-LTE Fe kinetic models have been developed to account for the L-shell radiation from the Fe ions and for the K-shell radiation from low ionization stages emitting the Fe cold Kα lines. Preliminary analysis of the simultaneously measured Fe L- and K-shell radiations from changing the time-duration, laser contrast, and focus of the experiments shows varying relative line intensities from different ionization stages. Resulting plasma parameters and their dependence on changing the time-duration, laser contrast, and laser focus will be discussed.

  18. 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.

  19. 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

    Science.gov (United States)

    Kemp, G. E.; Colvin, J. D.; Fournier, K. B.; May, M. J.; Barrios, M. A.; Patel, M. V.; Scott, H. A.; Marinak, M. M.

    2015-05-01

    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 (˜nc/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.

  20. 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

    International Nuclear Information System (INIS)

    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 (∼nc/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

  1. Ternary atom site location in L12-structured intermetallic compounds

    International Nuclear Information System (INIS)

    Ternary sublattice site occupancy in two L12-structured intermetallic compounds were evaluated by a transmission electron microscope technique called ALCHEMI, or atom site location by channeling enhanced microanalysis, and by x-ray diffractometry, through measuring the relative integrated intensity of fundamental and superlattice x-ray diffraction peaks. The x-ray diffractometry showed that in nickel-rich Ni3Al+Hf hafnium was found to occupy preferentially the aluminum sublattice, and in a multiphase alloy an L12-structured phase with the composition Al74.2Ti19Ni6.8 nickel atoms showed a strong preference for the titanium sublattice. The ALCHEMI data broadly agreed with the x-ray results for Ni3Al but gave completely the opposite result, i.e., a preference of nickel for the titanium sublattice, for Al3Ti. The methods of ALCHEMI and x-ray diffractometry are compared, and it is concluded that ALCHEMI data may be easily convoluted by peak overlap and delocalization effects

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

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Zhimin; Wang, Qiang, E-mail: wangqiang@njtech.edu.cn; Shan, Xiaoye; Zhu, Hongjun, E-mail: zhuhj@njtech.edu.cn [Department of Applied Chemistry, College of Science, Nanjing Tech University, Nanjing 211816 (China); Li, Wei-qi [Department of Physics, Harbin Institute of Technology, Harbin 150001 (China); Chen, Guang-hui [Department of Chemistry, Shantou University, Shantou, Guangdong 515063 (China)

    2015-02-21

    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.

  3. 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)

    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

  4. Preliminary nutritional and biological potential of Artocarpus heterophyllus L. shell powder.

    Science.gov (United States)

    Sharma, Anubhuti; Gupta, Priti; Verma, A K

    2015-03-01

    Artocarpus heterophyllus shell powder was investigated in terms of its nutritional and biological potential. A thorough examination of shell powder demonstrated its potential as a source of minerals, β carotene and dietary fiber, which were assessed gravimetrically & spectrophotometrically. This showed 3.05 ± 0.19 g 100 g(-1) DW of alkaloids followed by saponins and tannins. Three different extracts; acetone, methanol, & mix solvent were used to evaluate phenolic & flavonoid content, antioxidant & antimicrobial activity, GC/MS screening and quantitative analysis of polyphenols. Among all, the methanol extract showed highest antioxidant activity evaluated by DPPH, FRAP & ABTS assays and was significantly correlated with phenolic and flavonoid contents. Phenolic & flavonoid content was found to be 158 ± 0.34 mg (GAE) and 10.0 ± 0.64 mg (CE) respectively. The results of antimicrobial activity showed that L. monocytogenes was more susceptible to all extracts followed by other microorganisms. Catechin, ascorbic & chlorogenic acids were identified as major polyphenols analyzed by LC-MS/MS. GC/MS analysis showed that it contains a variety of compounds with different therapeutic activities. The study revealed that A. heterophyllus shell is a good source of natural antioxidants & other bioactive compounds and can be used in cosmetics, medicines and functional food application. PMID:25745202

  5. Novel method for isolation of major phenolic constituents from cashew (Anacardium occidentale L.) nut shell liquid.

    Science.gov (United States)

    Paramashivappa, R; Kumar, P P; Vithayathil, P J; Rao, A S

    2001-05-01

    Commercially available cashew (Anacardium occidentale L.) nut shell liquid (CNSL) mainly contains the phenolic constituents anacardic acid, cardol, and cardanol. These phenolic constituents are themselves heterogeneous, and each of them contains saturated, monoene, diene, and trienes in the fifteen-carbon side chain. This communication describes the separation of anacardic acid, cardol, and cardanol for industrial application. Anacardic acid was selectively isolated as calcium anacardate. The acid-free CNSL was treated with liquor ammonia and extracted with hexane/ethyl acetate (98:2) to separate the mono phenolic component, cardanol. Subsequently, ammonia solution was extracted with ethyl acetate/hexane (80:20) to obtain cardol. PMID:11368634

  6. Slurry analysis of cadmium and copper collected on 11-mercaptoundecanoic acid modified TiO2 core-Au shell nanoparticles by flame atomic absorption spectrometry

    International Nuclear Information System (INIS)

    Separation/preconcentration of copper and cadmium using TiO2 core-Au shell nanoparticles modified with 11-mercaptoundecanoic acid and their slurry analysis by flame atomic absorption spectrometry were described. For this purpose, at first, titanium dioxide nanoparticles were coated with gold shell by reducing the chloroauric acid with sodium borohydride and then modified with 11-mercaptoundecanoic acid. The characterization of modified nanoparticles was performed using ultra-violet spectroscopy and dynamic light scattering. Copper and cadmium were then collected on the prepared sorbent by batch method. The solid phase loaded with the analytes was separated by centrifugation and the supernatant was removed. Finally, the precipitate was slurried and directly aspirated into the flame for the determination of analytes. Thus, elution step and its all drawbacks were eliminated. The effects of pH, amount of sorbent, slurry volume, sample volume and diverse ions on the recovery were investigated. After optimization of experimental parameters, the analytes in different certified reference materials and spiked water samples were quantitatively recovered with 5% RSD. The analytes were enriched up to 20-fold. Limits of detection (N = 10, 3σ) for copper and cadmium were 0.28 and 0.15 ng mL-1, respectively.

  7. Relativistic equation-of-motion coupled-cluster method for the double ionization potentials of the closed-shell atoms

    CERN Document Server

    Pathak, Himadri; Sahoo, B K; Das, B P; Vaval, Nayana; Pal, Sourav

    2014-01-01

    We report the implementation of the relativistic equation-of-motion coupled-cluster method to calculate double ionization spectra (DI-EOMCC) of the closed-shell atomic systems. This method is employed to calculate principal valence double ionization potential values of He and alkaline earth metal (Be, Mg, Ca, Sr and Ba) atoms. Our results are compared with the results available from the national institute of science and technology (NIST) database and other ab initio calculations. We have achieved an accuracy of ~ 0.1%, which is an improvement over the first principles T-matrix calculations [J. Chem. Phys. 123, 144112 (2005)]. We also present results using the second-order many-body perturbation theory and the random -phase approximation in the equation-of-motion framework and these results are compared with the DI-EOMCC results.

  8. Synthesis of Pt–Pd Core–Shell Nanostructures by Atomic Layer Deposition: Application in Propane Oxidative Dehydrogenation to Propylene

    Energy Technology Data Exchange (ETDEWEB)

    Lei, Yu; Liu, Bin; Lu, Junling; Lobo-Lapidus, Rodrigo J.; Wu, Tianpin; Feng, Hao; Xia, Xiaoxing; Mane, Anil U.; Libera, Joseph A.; Greeley, Jeffrey P.; Miller, Jeffrey T.; Elam, Jeffrey W.

    2012-08-20

    Atomic layer deposition (ALD) was employed to synthesize supported Pt–Pd bimetallic particles in the 1 to 2 nm range. The metal loading and composition of the supported Pt–Pd nanoparticles were controlled by varying the deposition temperature and by applying ALD metal oxide coatings to modify the support surface chemistry. High-resolution scanning transmission electron microscopy images showed monodispersed Pt–Pd nanoparticles on ALD Al2O3- and TiO2-modified SiO2 gel. X-ray absorption spectroscopy revealed that the bimetallic nanoparticles have a stable Pt-core, Pd-shell nanostructure. Density functional theory calculations revealed that the most stable surface configuration for the Pt–Pd alloys in an H2 environment has a Pt-core, Pd-shell nanostructure. Finally, in comparison to their monometallic counterparts, the small Pt–Pd bimetallic core–shell nanoparticles exhibited higher activity in propane oxidative dehydrogenation as compared to their physical mixture.

  9. Atomic structure and thermal stability of Pt-Fe bimetallic nanoparticles: from alloy to core/shell architectures.

    Science.gov (United States)

    Huang, Rao; Wen, Yu-Hua; Shao, Gui-Fang; Sun, Shi-Gang

    2016-06-22

    Bimetallic nanoparticles comprising noble metal and non-noble metal have attracted intense interest over the past few decades due to their low cost and significantly enhanced catalytic performances. In this article, we have explored the atomic structure and thermal stability of Pt-Fe alloy and core-shell nanoparticles by molecular dynamics simulations. In Fe-core/Pt-shell nanoparticles, Fe with three different structures, i.e., body-centered cubic (bcc), face-centered cubic (fcc), and amorphous phases, has been considered. Our results show that Pt-Fe alloy is the most stable configuration among the four types of bimetallic nanoparticles. It has been discovered that the amorphous Fe cannot stably exist in the core and preferentially transforms into the fcc phase. The phase transition from bcc to hexagonal close packed (hcp) has also been observed in bcc-Fe-core/Pt-shell nanoparticles. In contrast, Fe with the fcc structure is the most preferred as the core component. These findings are helpful for understanding the structure-property relationships of Pt-Fe bimetallic nanoparticles, and are also of significance to the synthesis and application of noble metal based nanoparticle catalysts. PMID:27297782

  10. Postcollision interactions in the Auger decay of the Ar L-shell

    Energy Technology Data Exchange (ETDEWEB)

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

    1997-04-01

    The photoionization cross sections for Ar{sup +} through Ar{sup 4+}, produced by the Auger decay of an inner shell 2p hole, have been measured between 242 eV and 253 eV on beamline 9.0.1 and 6.3.2. In this study the authors are interested in near threshold phenomenon involving postcollision interactions (PCI), which are related to the Auger decay of a vacancy in the Ar L-shell. During an Auger decay a postcollision interaction can occur causing the out-going photoelectron to be retarded thus losing a certain amount of energy. If the retardation is sufficiently large the photoelectron will not escape. This result produces a singly charged ion, which normally would not be present. Such evidence of electron capture by the PCI effect was first shown clearly by Eberhardt et al. and, with higher resolution, in the present work. However, capture of the photoelectron is expected to be 100% exactly at the L{sub 2,3} thresholds. Thus, from the authors results they would have expected the Ar{sup 2+} signal to be zero at threshold, but it was not? The authors can explain this anomoly on the basis that during the Auger decay the photoelectrons are captured into high lying excited states of Ar{sup +}, which subsequently decay through autoionization yielding Ar{sup 2+}. Future work in this area will seek experimental evidence to verify this prediction.

  11. 77 FR 45596 - Shell Energy North America (US), L.P. v. California Independent System Operator Corporation...

    Science.gov (United States)

    2012-08-01

    ... Energy Regulatory Commission Shell Energy North America (US), L.P. v. California Independent System... Energy North America (US), L.P. (Complainant) filed a formal complaint against the California Independent... Commission's list of Corporate Officials. Any person desiring to intervene or to protest this filing...

  12. 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)

    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

  13. Absolute Time-Resolved Emission of Non-LTE L-Shell Spectra from Ti-Doped Aerogels

    Energy Technology Data Exchange (ETDEWEB)

    Back,C.; Feldman, U.; Weaver, J.; Seely, J.; Constantin, C.; Holland, G.; Lee, R.; Chung, H.; Scott, H.

    2006-01-01

    Outstanding discrepancies between data and calculations of laser-produced plasmas in recombination have been observed since the 1980s. Although improvements in hydrodynamic modeling may reduce the discrepancies, there are indications that non-LTE atomic kinetics may be the dominant cause. Experiments to investigate non-LTE effects were recently performed at the NIKE KrF laser on low-density Ti-doped aerogels. The laser irradiated a 2 mm diameter, cylindrical sample of various lengths with a 4-ns square pulse to create a volumetrically heated plasma. Ti L-shell spectra spanning a range of 0.47-3 keV were obtained with a transmission grating coupled to Si photodiodes. The diagnostic can be configured to provide 1-dimensional spatial resolution at a single photon energy, or 18 discrete energies with a resolving power, {gamma}/{delta}{gamma} of 3-20. The data are examined and compared to calculations to develop absolute emission measurements that can provide new tests of the non-LTE physics.

  14. Absolute, time-resolved emission of non-LTE L-shell spectra from Ti-doped aerogels

    Energy Technology Data Exchange (ETDEWEB)

    Back, C.A. [Lawrence Livermore National Laboratory, P.O. Box 808, L-21, Livermore, CA 94551 (United States)]. E-mail: tinaback@llnl.gov; Feldman, U. [Artep Inc. 2922 Excelsior Ct., Ellicott City, MD 21042 (United States); Weaver, J.L. [Naval Research Laboratory, 4555 Overlook Drive, SW, Washington DC 20375 (United States); Seely, J.F. [Naval Research Laboratory, 4555 Overlook Drive, SW, Washington DC 20375 (United States); Constantin, C. [Lawrence Livermore National Laboratory, P.O. Box 808, L-21, Livermore, CA 94551 (United States); Holland, G. [Naval Research Laboratory, 4555 Overlook Drive, SW, Washington DC 20375 (United States); Lee, R.W. [Lawrence Livermore National Laboratory, P.O. Box 808, L-21, Livermore, CA 94551 (United States); Chung, H.-K. [Lawrence Livermore National Laboratory, P.O. Box 808, L-21, Livermore, CA 94551 (United States); Scott, H.A. [Lawrence Livermore National Laboratory, P.O. Box 808, L-21, Livermore, CA 94551 (United States)

    2006-05-15

    Outstanding discrepancies between data and calculations of laser-produced plasmas in recombination have been observed since the 1980s. Although improvements in hydrodynamic modeling may reduce the discrepancies, there are indications that non-LTE atomic kinetics may be the dominant cause. Experiments to investigate non-LTE effects were recently performed at the NIKE KrF laser on low-density Ti-doped aerogels. The laser irradiated a 2mm diameter, cylindrical sample of various lengths with a 4-ns square pulse to create a volumetrically heated plasma. Ti L-shell spectra spanning a range of 0.47-3keV were obtained with a transmission grating coupled to Si photodiodes. The diagnostic can be configured to provide 1-dimensional spatial resolution at a single photon energy, or 18 discrete energies with a resolving power, {lambda}/{delta}{lambda} of 3-20. The data are examined and compared to calculations to develop absolute emission measurements that can provide new tests of the non-LTE physics.

  15. van der Waals interaction between an atom and a spherical plasma shell

    International Nuclear Information System (INIS)

    The van der Waals interaction energy of an atom with an infinitely thin sphere with finite conductivity is investigated in the framework of the hydrodynamic approach. Thin sphere models the fullerene. We put the sphere into a spherical cavity inside the infinite dielectric media then calculate the energy of vacuum fluctuations in the context of the ζ-function approach. The interaction energy for a single atom is obtained from this expression in the limit of the rare media. The Casimir-Polder expression for an atom and plate is recovered in the limit of the infinite radius of the sphere. Assuming a finite radius of the sphere, the interaction energy of an atom falls down to a third power of distance between the atom and sphere for short distances and to a seventh power for large distances from the sphere. Numerically the interaction energy is 3.8 eV for the hydrogen atom placed on the surface of the sphere with parameters of fullerene C60. We also show that the polarizability of fullerene is merely a cube of its radius.

  16. Deuteron-and alpha particle-induced K-shell ionisation of W and Au atoms

    International Nuclear Information System (INIS)

    Deuteron - and alpha particle - induced K-shell ionisation cross sections for W and Au were obtained from thick-target measurements for low impact velocities. They were compared to proton-induced cross sections in the same range of velocities. Equal-velocity cross sections ratios are a very stringent test to the corrections incorporated to the PWBA calculations. The σd/σp data presented in this paper sheds some light on the Coulomb-deflection corrections discussed in the literature. The consequences of the inelastic character of the ionisation process are thoroughly examined. (Author)

  17. Process for isolation of cardanol from technical cashew (Anacardium occidentale L.) nut shell liquid.

    Science.gov (United States)

    Phani Kumar, P; Paramashivappa, R; Vithayathil, P J; Subba Rao, P V; Srinivasa Rao, A

    2002-07-31

    Commercially available technical cashew (Anacardium occidentale L.) nut shell liquid (CNSL) contains mainly cardanol (decarboxylated anacardic acid) and cardol. Cardanol, the monophenolic component of technical CNSL, is widely used as a synthon for the preparation of a number of polymers and agricultural products. This paper describes the separation of cardanol from toxic cardol. Technical CNSL was dissolved in a mixture of methanol and ammonium hydroxide (8:5) and extracted with hexane to obtain cardanol. The resultant methanolic ammonia layer was extracted with a mixture of ethyl acetate and hexane to yield cardol. This is the first industrially feasible process based on solvent extractions for the isolation of cardanol from technical CNSL. PMID:12137500

  18. A Statistical Correlation Between Low L-shell Electrons Measured by NOAA Satellites and Strong Earthquakes

    Science.gov (United States)

    Fidani, C.

    2015-12-01

    More than 11 years of the Medium Energy Protons Electrons Detector data from the NOAA polar orbiting satellites were analyzed. Significant electron counting rate fluctuations were evidenced during geomagnetic quiet periods by using a set of adiabatic coordinates. Electron counting rates were compared to earthquakes by defining a seismic event L-shell obtained radially projecting the epicenter geographical positions to a given altitude. Counting rate fluctuations were grouped in every satellite semi-orbit together with strong seismic events and these were chosen with the L-shell coordinates close to each other. Electron data from July 1998 to December 2011 were compared for nearly 1,800 earthquakes with magnitudes larger than or equal to 6, occurring worldwide. When considering 30 - 100 keV energy channels by the vertical NOAA telescopes and earthquake epicenter projections at altitudes greater that 1,300 km, a 4 sigma correlation appeared where time of particle precipitations Tpp occurred 2 - 3 hour prior time of large seismic events Teq. This was in physical agreement with different correlation times obtained from past studies that considered particles with greater energies. The correlation suggested a 4-8 hour advance in preparedness of strong earthquakes influencing the ionosphere. Considering this strong correlation between earthquakes and electron rate fluctuations, and the hypothesis that such fluctuations originated with magnetic disturbances generated underground, a small scale experiment with low cost at ground level is advisable. Plans exists to perform one or more unconventional experiments around an earthquake affected area by private investor in Italy.

  19. Preparation of Core-Shell Hybrid Compounds by Atomic Transfer Radical Polymerization and Its Application to Plastic Lens of Headlamp.

    Science.gov (United States)

    Noh, Seung-Man; Ahn, Jae-Beum; Choi, Ki-Hyun; Park, Seung-Kyu

    2015-09-01

    Nano silica ball (NSB) core polymethylmethacrylate (PMMA) shell hybrid nanocomposites were synthesized by atomic transfer radical polymerization (ATRP) method for the application to the clearcoat to enhance scratch resistance. The characteristics of the synthesized inorganic/organic hybrid material were examined by scanning electron microscope (SEM), particle size analysis, Fourier transform infrared (FTIR) spectroscopy and thermo gravimetric analysis-differential scanning calorimetry (TGA-DSC). The scratch resistance and light transmittance of the clearcoat were measured by a nano-scratch tester and UV-visible spectroscopy, respectively. The average particle size of the NSB-PMMA hybrid compounds was 30 nm with narrow size distribution. Even 0.1 wt% loading of NSB-PMMA in the clearcoat dramatically enhanced the scratch resistance, about 40% increase in the force of the first fracture, while slightly reduced the light transmittance, about 5% only. PMID:26716303

  20. Charge-transfer energy in closed-shell ion-atom interactions. [for H and Li ions in He

    Science.gov (United States)

    Alvarez-Rizzatti, M.; Mason, E. A.

    1975-01-01

    The importance of charge-transfer energy in the interactions between closed-shell ions and atoms is investigated. Ab initio calculations on H(plus)-He and Li(plus)-He are used as a guide for the construction of approximate methods for the estimation of the charge-transfer energy for more complicated systems. For many alkali ion-rate gas systems the charge-transfer energy is comparable to the induction energy in the region of the potential minimum, although for doubly charged alkaline-earth ions in rare gases the induction energy always dominates. Surprisingly, an empirical combination of repulsion energy plus asymptotic induction energy plus asymptotic dispersion energy seems to give a fair representation of the total interaction, especially if the repulsion energy is parameterized, despite the omission of any explicit charge-transfer contribution. More refined interaction models should consider the charge-transfer energy contribution.

  1. The thermal Casimir–Polder interaction of an atom with a spherical plasma shell

    International Nuclear Information System (INIS)

    The van der Waals and Casimir–Polder interaction energy of an atom with an infinitely thin sphere with finite conductivity is investigated in the framework of the hydrodynamic approach at finite temperature. This configuration models the real interaction of an atom with fullerene. The Lifshitz approach is used to find the free energy. We find the explicit expression for the free energy and perform its analysis for (i) high and low temperatures, (ii) large radii of the sphere and (iii) short separation between an atom and sphere. At low temperatures the thermal part of the free energy approaches zero as the fourth power of the temperature, while for high temperatures it is proportional to the first degree of the temperature. The entropy of this system is positive for small radii of the sphere and it becomes negative at low temperatures and for large radii of the sphere. (paper)

  2. The thermal Casimir-Polder interaction of an atom with spherical plasma shell

    OpenAIRE

    Khusnutdinov, Nail R.

    2012-01-01

    The van der Waals and Casimir-Polder interaction energy of an atom with an infinitely thin sphere with finite conductivity is investigated in the framework of the hydrodynamic approach at finite temperature. This configuration models the real interaction of an atom with fullerene. The Lifshitz approach is used to find the free energy. We find the explicit expression for the free energy and perform the analysis of it for i) high and low temperatures, ii) large radii of sphere and ii) short sep...

  3. Up-down asymmetry in the relativistic (e, 2e) processes for K-shell ionization of Cu, Ag and Au atoms

    International Nuclear Information System (INIS)

    We present in this communication a theoretical demonstration of up-down asymmetry in the relativistic (e, 2e) process for K-shell ionization of Cu, Ag and Au atoms. The theoretical formalism has been developed in plane wave Born approximation and in this approximation the triple differential cross section (TDCS) has been expressed in terms of a product of kinematical factors and atomic structure functions. The up-down asymmetry in the relativistic (e, 2e) process on K-shell of atoms has been shown to depend on the interference between the transition charge and component of the transition current perpendicular to the scattering plane. Further, the up-down asymmetry has been shown to depend on incident electron energy, atomic number of the target and scattering electron angle. (author)

  4. Cold collisions of an open-shell S-state atom with a (2)Pi molecule : N(S-4) colliding with OH in a magnetic field.

    OpenAIRE

    Skomorowski, Wojciech; Gonzalez-Martinez, Maykel L.; Moszynski, Robert; Hutson, Jeremy M.

    2011-01-01

    We present quantum-theoretical studies of collisions between an open-shell S-state atom and a ^2Pi-state molecule in the presence of a magnetic field. We analyze the collisional Hamiltonian and discuss possible mechanisms for inelastic collisions in such systems. The theory is applied to the collisions of the nitrogen atom (^4S) with the OH molecule, with both collision partners initially in fully spin-stretched (magnetically trappable) states, assuming that the interaction takes place exclus...

  5. Three L-subshells atomic model to compute counting efficiency of electron-capture nuclides

    International Nuclear Information System (INIS)

    The present paper develops a three L-subshell a and K, M-a hells atomic model in order to obtain the counting efficiency in liquid scintillation counting. Mathematical expressions are given to calculate the probabilities of 264 different atomic rearrangement way so as the corresponding effective energies. This new model will permit to test the influence of the different atomic and nuclear parameters upon the counting efficiency nuclides of low and medium atomic number decaying by electron capture. (Author) 8 refs

  6. Isolation of atomically precise mixed ligand shell PdAu24 clusters

    Science.gov (United States)

    Sels, Annelies; Barrabés, Noelia; Knoppe, Stefan; Bürgi, Thomas

    2016-05-01

    Exposure of PdAu24(2-PET)18 (2-PET: 2-phenylethylthiolate) to BINAS (1,1-binaphthyl-2,2-dithiol) leads to species of composition PdAu24(2-PET)18-2x(BINAS)x due to ligand exchange reactions. The BINAS adsorbs in a specific mode that bridges the apex and one core site of two adjacent S(R)-Au-S(R)-Au-S(R) units. Species with different compositions of the ligand shell can be separated by HPLC. Furthermore, site isomers can be separated. For the cluster with exactly one BINAS in its ligand shell only one isomer is expected due to the symmetry of the cluster, which is confirmed by High-Performance Liquid Chromatography (HPLC). Addition of a second BINAS to the ligand shell leads to several isomers. In total six distinguishable isomers are possible for PdAu24(2-PET)14(BINAS)2 including two pairs of enantiomers concerning the adsorption pattern. At least four distinctive isomers are separated by HPLC. Calculations indicate that one of the six possibilities is energetically disfavoured. Interestingly, diastereomers, which have an enantiomeric relationship concerning the adsorption pattern of chiral BINAS, have significantly different stabilities. The relative intensity of the observed peaks in the HPLC does not reflect the statistical weight of the different isomers. This shows, as supported by the calculations, that the first adsorbed BINAS molecule influences the adsorption of the second incoming BINAS ligand. In addition, experiments with the corresponding Pt doped gold cluster reveal qualitatively the same behaviour, however with slightly different relative abundances of the corresponding isomers. This finding points towards the influence of electronic effects on the isomer distribution. Even for clusters containing more than two BINAS ligands a limited number of isomers were found, which is in contrast to the corresponding situation for monothiols, where the number of possible isomers is much larger.Exposure of PdAu24(2-PET)18 (2-PET: 2-phenylethylthiolate) to BINAS (1

  7. Following electron impact excitations of single Os, Pt, Hg, Pb and Po atom L subshells ionization cross section calculations by using Lotz's equation

    Science.gov (United States)

    Aydinol, M.; Aydeniz, D.

    2016-03-01

    L shell ionization cross section and Li subshells ionization cross sections of Os, Pt, Hg, Pb, Po atoms calculated. For each atom, ten different electron impacty energy values Eoi used. Calculations carried out by using nonrelativistic Lotz equation in Matlab. Ionization cross section values obtained for Eoi values in the energy range of ELi ≤Eoi≤4ELi for each atom. Starting allmost from Eoi = ELi (i = 1,2,3) values of the each subshell ionization threshold energy, ionization cross section are increasing rapidly with Eoi. For a fixed Eoi = 3. ELi values, while Z increases from Z = 76 to Z = 84, ionization cross section are decrease. These results help to understand some results which obtained from other electron-sigle atom impact studies on σLi subshells.

  8. Young’s modulus of PS/CeO2 composite with core/shell structure microspheres measured using atomic force microscopy

    International Nuclear Information System (INIS)

    Organic–inorganic composite microspheres with PS as a core and CeO2 as a shell were synthesized by in situ chemical precipitation method. The size of PS core was 117, 163, 206, and 241 nm, respectively, and the shell thickness was about 10 nm. The CeO2 shell was composed of a large number of nanoparticles, of which the size was 4–6 nm. Atomic force microscopy was employed to probe the mechanical properties of core–shell structured ceria-coated polystyrene (PS/CeO2) composite microspheres. On the basis of Hertz’s theory of contact mechanics, compressive moduli were measured by the analysis of force–displacement curves captured on the microsphere samples. For a fixed CeO2 shell thickness, the Young’s modulus of composite microspheres increased with an increase of PS core size. The calculated Young’s moduli (E) values of composites for 136, 185, 242, and 261 nm in diameter were 5.78 ± 0.9, 7.23 ± 1.3, 11.46 ± 1.7, and 14.54 ± 1.4 GPa, respectively. The results revealed the effect of the CeO2 shell on the elastic deformation of the PS core. This approach will provide fundamental insights into the actual role of organic/inorganic core/shell composite abrasives in chemical mechanical polishing.

  9. Time-resolved electron spectroscopy of atomic inner-shell dynamics

    International Nuclear Information System (INIS)

    The extremely fast evolution of core-hole relaxation was not yet observable directly in the time-domain. A novel technique combining core-hole creation with attosecond extreme ultraviolet (EUV) pulses and electron wave-packet sampling with a pulsed laser-field provides the necessary experimental tools. As a benchmark, the exponential decay of 3d holes in atomic krypton was tracked yielding a decay constant of 8 fs

  10. L-shell ionization of Sn and Gd by 20 - 100 keV electron impact

    International Nuclear Information System (INIS)

    Measurements have been made of the relative x-ray production cross section Lsub(α)/Lsub(γ), Lsub(α)/Lsub(β) and Lsub(α)/Lsub(l) using electrons of energy 20 to 100 keV incident on thin targets of tin and gadolinium. The experimental ratios obtained have been compared with theoretical values. Modification of these ratios due to the formation of double vacancy atomic states has been calculated, but this effect on its own is not sufficient to account for the discrepancy between theory and experimental results

  11. Experimental values of K to Li sub-shell, K to L, and K to M shell vacancy transfer probabilities for some rare earth elements.

    Science.gov (United States)

    Akman, Ferdi

    2016-09-01

    The K to Li (i=2,3), K to L, and K to M shell vacancy transfer probabilities for La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy and Er were determined at 59.54keV using a reflection geometry. The measurements were performed using an (241)Am annular radioactive source and a high resolution Si(Li) detector. The experimental results were compared with the theoretical values of Hartree-Slater and Hartree-Fock theories, semi-empirical and other available experimental results in the literature. Reasonable agreement is observed between the measured and theoretical results. PMID:27451114

  12. 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)

    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)

  13. 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)

    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.

  14. Measurements of L shell X-ray yields of thick Ag target by 6–29 keV electron impact

    International Nuclear Information System (INIS)

    In this paper, the L shell X-ray yields for a thick Ag target have been measured at incident electron energies of 6–29 keV. The experimental values are compared with the Monte Carlo simulation results that are obtained by using the PENELOPE code, in which the inner-shell ionization cross sections by electron impact calculated in the theoretical frame of distorted wave Born approximation are used. The experimental and simulation values are in agreement with ∼10% difference. Meanwhile, the L shell X-ray production cross sections are also obtained based on the measured L shell X-ray yields for a thick Ag target in this paper, and are compared with other experimental Ag L shell X-ray production cross section data by electron and positron impact measured previously and some theoretical models. Some factors that could affect these comparisons are also discussed in this paper. - Highlights: • We measured L shell X-ray yields of thick Ag target by 6–29 keV electrons. • Our measured X-ray yields are in good agreement with the MC results with ∼10%. • L shell production cross sections are obtained based on the measured X-ray yields. • L shell production cross sections obtained are in good agreement with theories

  15. Experimental cross sections for L-shell x-ray production and ionization by protons

    International Nuclear Information System (INIS)

    Tables of compiled cross sections list data for production of individual line and total L x-rays as well as for ionization of L subshells and the total L shell. The present cumulative compilation covers some six decades of measurements on targets from 10Ne to 95Am bombarded by protons ranging from 10 keV to 1 GeV. It includes data published in the period 1954–1992 from tables published in this journal, cross sections that were not reported in those tables, and new data from works published after 1992. Existing empirical, semiempirical, and theoretical analyses based on, and relative to, the pre-1993 database are reviewed. The experimental details are summarized for pre-1993 articles that were not referenced in previous compilations and, continuing the practice of these compilations, for each new publication. Covering the period 1954–December 2012, the present tabulation collects (not counting 2519 new data for Lβ1,3,4, Lβ2,15,Lγ1, Lγ2,3, and Lγ4,4′ x ray production) circa 15 500 experimental cross sections and enlarges the database from the previously published tables by 94%. -- Highlights: •An updated database is presented, increasing by 94% the earlier pre-1993 database. •The update has 40% more data from the pre-1993 period, absent in prior compilations. •The growth and possible saturation in the number of data is illustrated. •Ionization cross sections are reconverted to x-ray production cross sections. •Elements and ion energies are identified where measurements are still necessary

  16. Inner-shell magnetic dipole transition in Tm atom as a candidate for optical lattice clocks

    CERN Document Server

    Sukachev, D; Tolstikhina, I; Kalganova, E; Vishnyakova, G; Khabarova, K; Tregubov, D; Golovizin, A; Sorokin, V; Kolachevsky, N

    2016-01-01

    We consider a narrow magneto-dipole transition in the $^{169}$Tm atom at the wavelength of $1.14\\,\\mu$m as a candidate for a 2D optical lattice clock. Calculating dynamic polarizabilities of the two clock levels $[\\text{Xe}]4f^{13}6s^2 (J=7/2)$ and $[\\text{Xe}]4f^{13}6s^2 (J=5/2)$ in the spectral range from $250\\,$nm to $1200\\,$nm, we suggest the "magic" wavelength for the optical lattice at $807\\,$nm. Frequency shifts due to black-body radiation (BBR), the van der Waals interaction, the magnetic dipole-dipole interaction and other effects which can perturb the transition frequency are calculated. The transition at $1.14\\,\\mu$m demonstrates low sensitivity to the BBR shift corresponding to $8\\times10^{-17}$ in fractional units at room temperature which makes it an interesting candidate for high-performance optical clocks. The total estimated frequency uncertainty is less than $5 \\times 10^{-18}$ in fractional units. By direct excitation of the $1.14\\,\\mu$m transition in Tm atoms loaded into an optical dipole ...

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

    International Nuclear Information System (INIS)

    We consider, for atoms from 55Cs to 80Hg, the effective atomic radius (rear), 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 He2. The values of rear are about 50% larger than the mean radius of the outermost occupied orbital of 6s, . The value of rear decreases from 55Cs to 56Ba and undergoes increases and decreases with rising nuclear charge from 57La to 70Y b. In fact rear is understood as comprising two interlaced sequences; one consists of 57La, 58Ce, and 64Gd, which have electronic configuration (4fn−1)(5d1)(6s2), and the remaining atoms have configuration (4fn)(6s2). The sphere defined by rear contains 85%–90% of the 6s electrons. From 71Lu to 80Hg the radius rear also involves two sequences, corresponding to the two configurations 5dn+16s1 and 5dn6s2. The radius rear according to the present methodology is considerably larger than rvdW obtained by other investigators, some of who have found values of rvdW close to

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

    Directory of Open Access Journals (Sweden)

    Hiroshi Tatewaki

    2015-06-01

    Full Text Available We consider, for atoms from 55Cs to 80Hg, the effective atomic radius (rear, 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 He2. The values of rear are about 50% larger than the mean radius of the outermost occupied orbital of 6s, . The value of rear decreases from 55Cs to 56Ba and undergoes increases and decreases with rising nuclear charge from 57La to 70Y b. In fact rear is understood as comprising two interlaced sequences; one consists of 57La, 58Ce, and 64Gd, which have electronic configuration (4fn−1(5d1(6s2, and the remaining atoms have configuration (4fn(6s2. The sphere defined by rear contains 85%–90% of the 6s electrons. From 71Lu to 80Hg the radius rear also involves two sequences, corresponding to the two configurations 5dn+16s1 and 5dn6s2. The radius rear according to the present methodology is considerably larger than rvdW obtained by other investigators, some of who have found values of rvdW close to .

  19. L X-ray energy shifts and intensity ratios in tantalum with C and N ions – multiple vacancies in M, N and O shells

    Indian Academy of Sciences (India)

    Y Ramakrishna; K Ramachandra Rao; G J Naga Raju; K Bhaskara Rao; V Seshagiri Rao; P Venkateswarlu; S Bhuloka Reddy

    2002-10-01

    The energy shifts and intensity ratios of different L X-ray components in tantalum element due to 10 MeV carbon and 12 MeV nitrogen ions are estimated. From the observed energy shifts, the possible number of simultaneous vacancies in M shell are estimated. A comparison of L/L 2,15, L 1/L 1 and L 2,3/L 4,4 with the ratios due to Scofield theoretical transition rates indicate that the number of multiple vacancies in N shell are higher than the vacancies in M and O shell. Employing Larkin’s statistical scaling procedure, the number of possible multiple vacancies in N and O shells are estimated quantitatively.

  20. The thermal Casimir-Polder interaction of an atom with spherical plasma shell

    CERN Document Server

    Khusnutdinov, Nail R

    2012-01-01

    The van der Waals and Casimir-Polder interaction energy of an atom with an infinitely thin sphere with finite conductivity is investigated in the framework of the hydrodynamic approach at finite temperature. The Lifshits approach is used to find the free energy. We find the close expression for the free energy and make the analysis of it for i) high and low temperatures, ii) large radii of sphere and ii) short distance from sphere. At low temperatures the thermal part of the free energy tends to zero as forth power of the temperature while for high temperatures it is proportional to the first degree of the temperature. We show that the entropy of this system is positive for small radii of sphere and it becomes negative at low temperatures and for large radii of the sphere.

  1. Inner-shell correlations and Sturm expansions in coupled perturbation calculations of atomic systems

    Energy Technology Data Exchange (ETDEWEB)

    Sherstyuk, A.I.; Solov`eva, G.S. [Vavilov State Optical Institute, St. Petersburg (Russian Federation)

    1995-04-01

    It is shown that virtual Hartree-Fock orbitals in Sturm-type expansions can be used to calculate the response of atomic systems to an external field within the framework of the coupled perturbation theory with allowance for correlation effects. The corrected electron-electron interaction in a system with field-distorted orbitals is considered by adding a nonlocal potential to a one-electron Hartree-Fock operator within each group of equivalent elections. The remaining correlation effects are calculated by solving a system of equations for corrections to the radial functions. The system is solved iteratively, with each subsequent iteration corresponding to a correction of an increasingly higher order in the electron--electron interaction. The explicit expression derived for the polarizability contains one-and two-particle radial integrals of the Sturm functions.

  2. Inner-shell correlations and Sturm expansions in coupled perturbation calculations of atomic systems

    International Nuclear Information System (INIS)

    It is shown that virtual Hartree-Fock orbitals in Sturm-type expansions can be used to calculate the response of atomic systems to an external field within the framework of the coupled perturbation theory with allowance for correlation effects. The corrected electron-electron interaction in a system with field-distorted orbitals is considered by adding a nonlocal potential to a one-electron Hartree-Fock operator within each group of equivalent elections. The remaining correlation effects are calculated by solving a system of equations for corrections to the radial functions. The system is solved iteratively, with each subsequent iteration corresponding to a correction of an increasingly higher order in the electron--electron interaction. The explicit expression derived for the polarizability contains one-and two-particle radial integrals of the Sturm functions

  3. 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 .

  4. Anomalous elastic scattering of linearly polarized X-ray radiation by multicharged atomic ions in the range of the ionization threshold of the 1s-shell

    Energy Technology Data Exchange (ETDEWEB)

    Hopersky, A.N. E-mail: phys@rgups.ru; Novikov, S.A.; Chuvenkov, V.V

    2002-04-01

    The absolute values and shape of differential cross-section of the process of the anomalous elastic scattering for non-zero angle are investigated within non-relativistic approximation for linearly polarized X-ray radiation scattered by multicharged atomic ions Ne{sup 6+} in the range of the ionization threshold of 1s-shell. The many-particle effects of radial rearrangement of electron shells in the field of an inner 1s-vacancy and the effect of vacancy stabilization are taken into account. The results of the work are predictions.

  5. Multifunctional antitumor magnetite/chitosan-l-glutamic acid (core/shell) nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Daniela P. [University of Sao Paulo State, UNESP, Institute of Chemistry (Brazil); Ruiz, M. Adolfina; Gallardo, Visitacion [University of Granada, Department of Pharmacy and Pharmaceutical Technology, Faculty of Pharmacy (Spain); Zanoni, Maria Valnice B. [University of Sao Paulo State, UNESP, Institute of Chemistry (Brazil); Arias, Jose L., E-mail: jlarias@ugr.es [University of Granada, Department of Pharmacy and Pharmaceutical Technology, Faculty of Pharmacy (Spain)

    2011-09-15

    The development of anticancer drug delivery systems based on biodegradable nanoparticles has been intended to maximize the localization of chemotherapy agents within tumor interstitium, along with negligible drug distribution into healthy tissues. Interestingly, passive and active drug targeting strategies to cancer have led to improved nanomedicines with great tumor specificity and efficient chemotherapy effect. One of the most promising areas in the formulation of such nanoplatforms is the engineering of magnetically responsive nanoparticles. In this way, we have followed a chemical modification method for the synthesis of magnetite/chitosan-l-glutamic acid (core/shell) nanostructures. These magnetic nanocomposites (average size Almost-Equal-To 340 nm) exhibited multifunctional properties based on its capability to load the antitumor drug doxorubicin (along with an adequate sustained release) and its potential for hyperthermia applications. Compared to drug surface adsorption, doxorubicin entrapment into the nanocomposites matrix yielded a higher drug loading and a slower drug release profile. Heating characteristics of the magnetic nanocomposites were investigated in a high-frequency alternating magnetic gradient: a stable maximum temperature of 46 Degree-Sign C was successfully achieved within 40 min. To our knowledge, this is the first time that such kind of stimuli-sensitive nanoformulation with very important properties (i.e., magnetic targeting capabilities, hyperthermia, high drug loading, and little burst drug release) has been formulated for combined antitumor therapy against cancer.

  6. Implementation and Application of the Relativistic Equation of Motion Coupled-cluster Method for the Excited States of Closed-shell Atomic Systems

    CERN Document Server

    Nandy, D K; Sahoo, B K

    2014-01-01

    We report the implementation of equation-of-motion coupled-cluster (EOMCC) method in the four-component relativistic framework with the spherical atomic potential to generate the excited states from a closed-shell atomic configuration. This theoretical development will be very useful to carry out high precision calculations of varieties of atomic properties in many atomic systems. We employ this method to calculate excitation energies of many low-lying states in a few Ne-like highly charged ions, such as Cr XV, Fe XVII, Co XVIII and Ni XIX ions, and compare them against their corresponding experimental values to demonstrate the accomplishment of the EOMCC implementation. The considered ions are apt to substantiate accurate inclusion of the relativistic effects in the evaluation of the atomic properties and are also interesting for the astrophysical studies. Investigation of the temporal variation of the fine structure constant (\\alpha) from the astrophysical observations is one of the modern research problems...

  7. K, L, and M shell datasets for PIXE spectrum fitting and analysis

    Science.gov (United States)

    Cohen, David D.; Crawford, Jagoda; Siegele, Rainer

    2015-11-01

    Routine PIXE analysis programs, like GUPIX, GEOPIXE and PIXAN generally perform at least two key functions firstly, the fitting of K, L and M characteristic lines X-ray lines to a background, including unfolding of overlapping lines and secondly, the use of a fitted primary Kα, Lα or Mα line area to determine the elemental concentration in a given matrix. To achieve these two results to better than 3-5% the data sets for fluorescence yields, emission rates, Coster-Kronig transitions and ionisation cross sections should be determined to better than 3%. There are many different theoretical and experimental K, L and M datasets for these parameters. How they are applied and used in analysis programs can vary the results obtained for both fitting and concentration determinations. Here we discuss several commonly used datasets for fluorescence yields, emission rates, Coster-Kronig transitions and ionisation cross sections for K, L and M subshells and suggests an optimum set to obtain consistent results for PIXE analyses across a range of elements with atomic numbers from 5 ⩽ Z ⩽ 100.

  8. Quasi-atomic model of bacteriophage t7 procapsid shell: insights into the structure and evolution of a basic fold.

    Science.gov (United States)

    Agirrezabala, Xabier; Velázquez-Muriel, Javier A; Gómez-Puertas, Paulino; Scheres, Sjors H W; Carazo, José M; Carrascosa, José L

    2007-04-01

    The existence of similar folds among major structural subunits of viral capsids has shown unexpected evolutionary relationships suggesting common origins irrespective of the capsids' host life domain. Tailed bacteriophages are emerging as one such family, and we have studied the possible existence of the HK97-like fold in bacteriophage T7. The procapsid structure at approximately 10 A resolution was used to obtain a quasi-atomic model by fitting a homology model of the T7 capsid protein gp10 that was based on the atomic structure of the HK97 capsid protein. A number of fold similarities, such as the fitting of domains A and P into the L-shaped procapsid subunit, are evident between both viral systems. A different feature is related to the presence of the amino-terminal domain of gp10 found at the inner surface of the capsid that might play an important role in the interaction of capsid and scaffolding proteins. PMID:17437718

  9. Core-shell Si@TiO2 nanosphere anode by atomic layer deposition for Li-ion batteries

    Science.gov (United States)

    Bai, Ying; Yan, Dong; Yu, Caiyan; Cao, Lina; Wang, Chunlei; Zhang, Jinshui; Zhu, Huiyuan; Hu, Yong-Sheng; Dai, Sheng; Lu, Junling; Zhang, Weifeng

    2016-03-01

    Silicon (Si) has been regarded as next-generation anode for high-energy lithium-ion batteries (LIBs) due to its high Li storage capacity (4200 mA h g-1). However, the mechanical degradation and resultant capacity fade critically hinder its practical application. In this regard, we demonstrate that nanocoating of Si spheres with a 3 nm titanium dioxide (TiO2) layer via atomic layer deposition (ALD) can utmostly balance the high conductivity and the good structural stability to improve the cycling stability of Si core material. The resultant sample, Si@TiO2-3 nm core-shell nanospheres, exhibits the best electrochemical performance of all with a highest initial Coulombic efficiency and specific charge capacity retention after 50 cycles at 0.1C (82.39% and 1580.3 mA h g-1). In addition to making full advantage of the ALD technique, we believe that our strategy and comprehension in coating the electrode and the active material could provide a useful pathway towards enhancing Si anode material itself and community of LIBs.

  10. FROM THE HISTORY OF PHYSICS: L D Landau in the Soviet Atomic Project: a documentary study

    Science.gov (United States)

    Kiselev, G. V.

    2008-09-01

    The article presents information about the participation of Academician L D Landau in the Soviet Atomic Project and is based on a study of archive documents of the First Main Directorate. Their analysis points to L D Landau's important contribution to the development of the theory of heterogeneous nuclear reactors and to the computational justification of the first designs of atomic and hydrogen bombs. Many of the quoted documents have never been published before.

  11. L D Landau in the Soviet Atomic Project: a documentary study

    International Nuclear Information System (INIS)

    The article presents information about the participation of Academician L D Landau in the Soviet Atomic Project and is based on a study of archive documents of the First Main Directorate. Their analysis points to L D Landau's important contribution to the development of the theory of heterogeneous nuclear reactors and to the computational justification of the first designs of atomic and hydrogen bombs. Many of the quoted documents have never been published before. (from the history of physics)

  12. 18. Within the atom economical electronic "s, p, d, f Type electron hull shell" forming principle and spin Elliptical orbit parameters variation analysis

    Directory of Open Access Journals (Sweden)

    Huang Zhenqiang and Huang Yuxiang

    2013-10-01

    Full Text Available In chapter 16 we have about three of hydrogen, lithium, helium atoms "s type ball shell electron cloud" describes forming principle and calculation. Therefore: each electronic in nucleus and other electronic electric, magnetic field force, not only along the spin elliptical orbits around the nucleus, there are different degrees of lateral additional movement, as shown in figure 18.2, 18.4, 18.6... As shown. It formed the spin elliptical orbit revolving curved surface. When same layer n of rotating ellipsoid surface "electron hull shell" under the action of electric field repelling force symmetry respectively to different space position and direction, were composed "s, p, d, f type electron hull shell". From (1.2-1 type, electronic wave radius:

  13. Machines géantes pour sonder l'univers de l'atome

    CERN Multimedia

    Wilde, M, S

    1966-01-01

    To always more deeply explore the infinitely small world of the atom, Science is paradoxically brought to build buildings and machines increasingly larger - Giant accelerators producing high energy particle beams that can dissociate the structures of the atomic nucleus

  14. Laboratory Measurements of the K-shell transition energies in L-shell ions of Si and S

    CERN Document Server

    Hell, N; Wilms, J; Grinberg, V; Clementson, J; Liedahl, D; Porter, F S; Kelley, R L; Kilbourne, C A; Beiersdorfer, P

    2016-01-01

    We have measured the energies of the strongest 1s-2ell (ell=s,p) transitions in He- through Ne-like silicon and sulfur ions to an accuracy of better than 1eV using Lawrence Livermore National Laboratory's electron beam ion traps, EBIT-I and SuperEBIT, and the NASA/GSFC EBIT Calorimeter Spectrometer (ECS). We identify and measure the energies of 18 and 21 X-ray features from silicon and sulfur, respectively. The results are compared to new Flexible Atomic Code calculations and to semi-relativistic Hartree Fock calculations by Palmeri et al. (2008). These results will be especially useful for wind diagnostics in high mass X-ray binaries, such as Vela X-1 and Cygnus X-1, where high-resolution spectral measurements using Chandra's high energy transmission grating has made it possible to measure Doppler shifts of 100km/s. The accuracy of our measurements is consistent with that needed to analyze Chandra observations, exceeding Chandra's 100km/s limit. Hence, the results presented here not only provide benchmarks f...

  15. Antioxidant and Free Radical Scavenging Capacity of Seed and Shell Essential Oils Extracted from Abrus precatorius (L)

    OpenAIRE

    Sunday O. Okoh; Asekun, Olayinka T.; Familoni, Oluwole B.; Afolayan, Anthony J.

    2014-01-01

    Essential oils from plants have been proven safe as natural antioxidants, and few are already marketed as digestive enhancers as well as in prevention of several degenerative diseases. This study evaluated the antioxidant capacity of seed and shell essential oils of Abrus precatorius (L), a herb used for ethno-medicinal practices in Nigeria. The essential oils were obtained by hydro-distillation. The ability of the oils to act as hydrogen/electrons donor or scavenger of radicals were determin...

  16. Open M-shell Opacity of Bromine Plasma in Comparison of the Detailed Level Accounting Model with the Average Atom Model

    Institute of Scientific and Technical Information of China (English)

    JIN Feng-Tao; YUAN Jian-Min

    2005-01-01

    @@ The open M-shell opacity of a hot bromine plasma has been calculated by using a detailed level accounting (DLA )model. One-electron orbitals obtained by solving the fully relativistic Dirac-Fock equations are used to obtain the atomic levels and the radiative transition oscillator strengths. Only the level mixing within the same electron configuration is considered to reduce the complexity of the calculations. Detailed comparisons have been made between the results of the DLA and average atom (AA) models. Good agreements are found for both the M-shell transition arrays and the Planck mean opacity but there are differences for the line positions in the 2p → 3d absorption region due to the statistical treatment for the one-electron orbitals in the AA model.

  17. K-, L- and M-shell x-ray production cross sections by 1–1.3 MeV protons

    Energy Technology Data Exchange (ETDEWEB)

    Batyrbekov, E., E-mail: batyrbekov@nnc.kz [National Nuclear Centre, Krasnoarmeyskaya 2, Kurchatov 071100 (Kazakhstan); Gorlachev, I., E-mail: I.Gorlachev@gmail.com [Institute of Nuclear Physics, Ibragimov 1, Alatau 050032, Almaty (Kazakhstan); Ivanov, I., E-mail: mind_slide@mail.ru [Institute of Nuclear Physics, Ibragimov 1, Alatau 050032, Almaty (Kazakhstan); Platov, A., E-mail: platov@inp.kz [Institute of Nuclear Physics, Ibragimov 1, Alatau 050032, Almaty (Kazakhstan)

    2014-04-01

    In 2012, our institute had initiated a series of research activities aimed to measure the characteristic x-ray production cross-section, arising from interaction of accelerated particles with target atoms. This paper presents the data of x-ray production cross-sections under excitation of K-, L- and M-shells of target atoms in the range of mass from Mg to Bi by protons of the energies in the range of 1–1.3 MeV. We used the approach based on calculation of x-ray production cross sections through the cross-section of Rutherford backscattering, which can be calculated with high accuracy from the Rutherford formula. Such approach reduces the measurement errors of x-ray cross-sections and thus improves the accuracy of the obtained data. It is further planned to expand the area of research to protons of other energies and heavy charged particles in the energy range of 0.5–1.7 MeV/nucleon.

  18. 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)

    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)

  19. Atoms

    Institute of Scientific and Technical Information of China (English)

    刘洪毓

    2007-01-01

    Atoms(原子)are all around us.They are something like the bricks (砖块)of which everything is made. The size of an atom is very,very small.In just one grain of salt are held millions of atoms. Atoms are very important.The way one object acts depends on what

  20. Photogenerated carriers transport behaviors in L-cysteine capped ZnSe core-shell quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Shan, Qingsong; Li, Kuiying, E-mail: kuiyingli@ysu.edu.cn; Lin, Yingying; Yin, Hua; Zhu, Ruiping [State Key Laboratory of Metastable Materials Manufacture Technology and Science, Yanshan University, Qinhuangdao 066004 (China); Xue, Zhenjie [Beijing National Laboratory for Molecular Sciences, Key Laboratory of Analytical Chemistry for Living Biosystems, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190 (China)

    2016-02-07

    The photoexcited carrier transport behavior of zinc selenide (ZnSe) quantum dots (QDs) with core–shell structure is studied because of their unique photoelectronic characteristics. The surface photovoltaic (SPV) properties of self-assembled ZnSe/ZnS/L-Cys core–shell QDs were probed via electric field induced surface photovoltage and transient photovoltage (TPV) measurements supplemented by Fourier transform infrared, laser Raman, absorption, and photoluminescence spectroscopies. The ZnSe QDs displayed p-type SPV characteristics with a broader stronger SPV response over the whole ultraviolet-to-near-infrared range compared with those of other core–shell QDs in the same group. The relationship between the SPV phase value of the QDs and external bias was revealed in their SPV phase spectrum. The wide transient photovoltage response region from 3.3 × 10{sup −8} to 2 × 10{sup −3} s was closely related to the long diffusion distance of photoexcited free charge carriers in the interfacial space–charge region of the QDs. The strong SPV response corresponding to the ZnSe core mainly originated from an obvious quantum tunneling effect in the QDs.

  1. Photogenerated carriers transport behaviors in L-cysteine capped ZnSe core-shell quantum dots

    International Nuclear Information System (INIS)

    The photoexcited carrier transport behavior of zinc selenide (ZnSe) quantum dots (QDs) with core–shell structure is studied because of their unique photoelectronic characteristics. The surface photovoltaic (SPV) properties of self-assembled ZnSe/ZnS/L-Cys core–shell QDs were probed via electric field induced surface photovoltage and transient photovoltage (TPV) measurements supplemented by Fourier transform infrared, laser Raman, absorption, and photoluminescence spectroscopies. The ZnSe QDs displayed p-type SPV characteristics with a broader stronger SPV response over the whole ultraviolet-to-near-infrared range compared with those of other core–shell QDs in the same group. The relationship between the SPV phase value of the QDs and external bias was revealed in their SPV phase spectrum. The wide transient photovoltage response region from 3.3 × 10−8 to 2 × 10−3 s was closely related to the long diffusion distance of photoexcited free charge carriers in the interfacial space–charge region of the QDs. The strong SPV response corresponding to the ZnSe core mainly originated from an obvious quantum tunneling effect in the QDs

  2. Photogenerated carriers transport behaviors in L-cysteine capped ZnSe core-shell quantum dots

    Science.gov (United States)

    Shan, Qingsong; Li, Kuiying; Xue, Zhenjie; Lin, Yingying; Yin, Hua; Zhu, Ruiping

    2016-02-01

    The photoexcited carrier transport behavior of zinc selenide (ZnSe) quantum dots (QDs) with core-shell structure is studied because of their unique photoelectronic characteristics. The surface photovoltaic (SPV) properties of self-assembled ZnSe/ZnS/L-Cys core-shell QDs were probed via electric field induced surface photovoltage and transient photovoltage (TPV) measurements supplemented by Fourier transform infrared, laser Raman, absorption, and photoluminescence spectroscopies. The ZnSe QDs displayed p-type SPV characteristics with a broader stronger SPV response over the whole ultraviolet-to-near-infrared range compared with those of other core-shell QDs in the same group. The relationship between the SPV phase value of the QDs and external bias was revealed in their SPV phase spectrum. The wide transient photovoltage response region from 3.3 × 10-8 to 2 × 10-3 s was closely related to the long diffusion distance of photoexcited free charge carriers in the interfacial space-charge region of the QDs. The strong SPV response corresponding to the ZnSe core mainly originated from an obvious quantum tunneling effect in the QDs.

  3. Resonant electron transfer and L-shell excitation for 26Fe19+ and 30Zn23+ ions

    OpenAIRE

    RAMADAN, Hassan

    2012-01-01

    Resonant transfer and excitation (RTE) involving simultaneous electron capture and projectile L-shell excitation has been calculated for Fe19+ and Zn23+ ions, in charge states ranging from nitrogen-like to oxygen-like incident on molecular hydrogen over an energy range 0--250 MeV. By the same way the calculations have been performed with helium over an energy range 0--300 MeV. The calculations are carried out using the angular momentum average (AMA) scheme in the isolated resonance app...

  4. Atoms

    International Nuclear Information System (INIS)

    Completed by recent contributions on various topics (atoms and the Brownian motion, the career of Jean Perrin, the evolution of atomic physics since Jean Perrin, relationship between scientific atomism and philosophical atomism), this book is a reprint of a book published at the beginning of the twentieth century in which the author addressed the relationship between atomic theory and chemistry (molecules, atoms, the Avogadro hypothesis, molecule structures, solutes, upper limits of molecular quantities), molecular agitation (molecule velocity, molecule rotation or vibration, molecular free range), the Brownian motion and emulsions (history and general features, statistical equilibrium of emulsions), the laws of the Brownian motion (Einstein's theory, experimental control), fluctuations (the theory of Smoluchowski), light and quanta (black body, extension of quantum theory), the electricity atom, the atom genesis and destruction (transmutations, atom counting)

  5. Selected K and L X-Ray mass attenuation coefficients for low atomic number materials

    International Nuclear Information System (INIS)

    X-ray attenuation coefficients for low atomic mumbers elements were obtained for characteristic K and L X-ray of a number of selected elements using the fitting of a third degree polynomial to the values tabulated by Storm and Israel

  6. Computation of triple differential cross-sections with the inclusion of exchange effects in atomic K-shell ionization by relativistic electrons for symmetric geometry

    Indian Academy of Sciences (India)

    S Dhar; M R Alam

    2007-09-01

    The triple differential cross-section for K-shell ionization of silver and copper atoms by relativistic electrons have been computed in the coplanar symmetric geometry with the inclusion of exchange effects following the multiple scattering theory of Das and Seal [1] multiplied by suitable spinors. Present computed results are marginally improved in some cases from the previous computed results [2]. Present results are compared with measured values [3] and with previous computation results [2]. Some other theoretical computational results are also presented here for comparison.

  7. Kβ to Kα X-ray intensity ratios and K to L shell vacancy transfer probabilities of Co, Ni, Cu, and Zn

    International Nuclear Information System (INIS)

    The K to L shell total vacancy transfer probabilities of low Z elements Co, Ni, Cu, and Zn are estimated by measuring the Kβ to Kα intensity ratio adopting the 2π-geometry. The target elements were excited by 32.86 keV barium K-shell X-rays from a weak 137Cs γ-ray source. The emitted K-shell X-rays were detected using a low energy HPGe X-ray detector coupled to a 16 k MCA. The measured intensity ratios and the total vacancy transfer probabilities are compared with theoretical results and others’ work, establishing a good agreement

  8. De l'atome antique à l'atome quantique à la recherche des mystères de la matière

    CERN Document Server

    Gruber, Christian

    2013-01-01

    Les atomes et les molécules constituent les éléments fondamentaux de la matière. Cet état de fait, aujourd'hui admis par tous, repose toutefois sur un paradoxe : nul n'est en mesure d'en percevoir immédiatement la réalité. 500 ans avant notre ère, Démocrite pose pourtant les bases de ce qui deviendra la théorie atomique ; suivront vingt-cinq siècles d'interrogations et de recherches dans l'espoir de percer les secrets de l'invisible. C'est à la découverte de cette épopée scientifique et humaine que cet ouvrage invite le lecteur. Il décrit, depuis la philosophie naturelle antique jusqu'à la révolution quantique actuelle, la soif de savoir qui a guidé l'homme sur les traces de la nature ultime de la matière. Synthétique, didactique et tout spécialement conçu pour un lectorat non scientifique, il présente les principaux concepts théoriques et les expériences fondatrices qui ont progressivement transformé l'hypothèse atomique en une réalité scientifique. Un livre rare, jusqu'à pré...

  9. Diffusivities and atomic mobilities in disordered fcc and ordered L12 Ni–Al–W alloys

    International Nuclear Information System (INIS)

    Highlights: • The atomic mobilities for fcc Al–W, fcc Ni–W, fcc Ni–Al–W and L12 Ni–Al–W alloys were critically assessed. • The impurity diffusivity of W in fcc-Al was obtained via first-principles calculations. • The calculated results agree well with the diffusivities available in the literature. • Two fcc/L12-type diffusion couples were prepared and the concentration-distance profiles were measured. • The model-predicted concentration profiles agree well with the experimental data in the literature and in the present work. - Abstract: Based on various experimentally measured diffusivities available in the literature together with the reported thermodynamic parameters, the atomic mobilities for disordered fcc and ordered L12 Ni–Al–W alloys were assessed on the basis of a recently developed phenomenological model incorporated in the DICTRA software. In order to provide the missing impurity diffusion coefficients of W in fcc-Al, first-principles calculations were utilized in the present work. Comprehensive comparisons between the calculated and experimental diffusion coefficients show that all the experimental data can be well reproduced by the atomic mobilities obtained in the present work. In order to further verify the reliability of the presently obtained atomic mobilities, two fcc/L12-type diffusion couples (i.e., Ni–5 at.% Al–5 at.% W/Ni–20 at.% Al–4 at.% W and Ni/Ni–22 at.% Al–2 at.% W) were prepared and the concentration-distance profiles after annealing at 1323 K for 86.4 ks were measured. The excellent agreement between the model-predicted concentration-distance profiles and the experimental data indicates that the presently obtained atomic mobilities in fcc/L12 Ni–Al–W alloys are reliable

  10. L2 discretization of atomic and molecular electronic continua: moment, quadrature and J-matrix techniques

    International Nuclear Information System (INIS)

    A review of the process of extraction of continuum information from operators discretized in finite sets of square integrable (L2) basis functions is given, with emphasis on the close relationships between the Stieltjes method and Gaussian integration. Examples of recent applications are given in the areas of atomic and molecular photoabsorption (He, Ne*, H2, Ar2*), Stieltjes determination of e- -atom/molecule resonances (He, He-, Mg-, N2-) and e+ -H scattering at intermediate energies. Finally, photoabsorption of H- leading to H+ + 2e is discussed using the J-matrix technique, which involves an infinite L2 expansion, and combines advantages of the finite L2 methods with those of the traditional close coupling method. (Auth.)

  11. Determination of rare earth elements, thorium, and uranium in mussel, ark shell, and coral by inductively coupled plasma atomic emission spectrometry

    International Nuclear Information System (INIS)

    The determination of rare earth elements, thorium, and uranium in mussel, ark shell, and coral was made by inductively coupled plasma atomic emission spectrometry(ICP-AES). Four samples of mussels, original mussles, and mussels powdered by the original standard method, were dissolved with a mixture of HNO3 and HClO4. For one part of the sample solution, coprecipitation by ferric hydroxide was applied. Analytical values obtained with and without coprecipitation showed good agreement. The sample solutions for shells and coral were prepared by acid decomposition, and the elements to be determined were separated from calcium by coprecipitation to eliminate spectral interference by calcium. Analytical values were obtained from the calibration curves made with standard solutions containing matrix components at concentrations similar to those for real samples solutions. The concentrations of rare earth elements, Th and U in sample solutions of mussel ranged from 0.001 μg/g to 0.2 μg/g. The concentrations of rare earth elements and Th in mussel, shells, and coral are 2000 -- 15000 times higher than those in sea water. (author)

  12. Inner-shell ionization of heavy atoms by slow ions. A study of electronic relativistic effects and projectile Coulomb deflection in the Semiclassical Approximation

    International Nuclear Information System (INIS)

    Several investigations have been made on K and L shell ionization of the heavy collision partner in slow asymmetric collisions based on the SCA. The use of the SCA can only be defended for slow collisions if the projectile has a charge much less than the target. Thus this approximation should first be tested for proton impact on very heavy target elements. For these elements the inner shell electrons move sufficiently fast for a relativistic description to be mandatory. These relativistic effects are in themselves of some interest, as they can be quite large. After discussion of the formulation of the SCA used throughout this work, a further introduction is given on relativistic effects in Coulomb ionisation. Two papers on electronic relativistic effects in K and L shell ionization follow. The next two papers discuss calculations with an exact Coulomb projectile path. The latter of these also touches upon the inclusion of corrections to the SCA from terms beyond first order perturbation theory. In the last paper of this thesis it is shown how the theoretical apparatus developed for the SCA- calculations can immediately be used also for making calculations of more symmetric systems with the Briggs model. Thus, at least for direct ionization in very slow collisions a unification of the SA and MO approaches has apparently been reached. (JIW)

  13. Electronic structure of the 3d metals. An investigation by L-shell-photoionisation

    Energy Technology Data Exchange (ETDEWEB)

    Richter, T.S.

    2007-12-03

    The 3d transition metal elements from Sc to Cu have been investigated by both photo electron emission and photo absorption. Experimental spectra in the 2p energy range are discussed based on atomic multiplet models and Hartree- Fock calculations. The samples have been evaporated from an electron bombardment crucible and excited/ionized by monochromatized synchrotron radiation. Fundamental effects and the main interactions which govern the electronic structure of the 3d metal atoms are covered. Common spectral features and trends in the series are discussed as well as the importance of many body electron correlation effects. (orig.)

  14. De-excitation decay following 1s and 2p shell ionization in Potassium and Calcium atoms using Monte Carlo method

    International Nuclear Information System (INIS)

    Full text; Relative abundance of charged ions and mean charged ions are calculated following 1s and 2p vacancy production in potassium and calcium atoms. The calculations are performed with Monte Carlo simulation method. The simulation based on the tracing of all possible radiation, non-radiation transitions and electron shake off probabilities after inner shell vacancy creation. The radiative transition rates and electron shakes off processes are obtained with Multiconfiguration-Dirac-Fock (MCDF) wave functions model. The non-radiation transition rates are carried out using Dirac-Fock-Slater (DFS) wave functions. At 1s hole states in Potassium atom, the yield of K5+ ions are the prominent produces. The doubly charged K2+ ions predominate over K3+ ions after 2p shell ionization in potassium. On the other hand, the Ca3+ ions dominate over Ca2+ ions in Calcium. The considerations of closing some Coster-Kronig channels and electron shake off processes through the simulation improve the results of charged ions with the experimental data. The results of electron shake off probabilities are compared with other theoretical calculation. The results of relative abundance of charged ions agree well with the experimental data. (author)

  15. Preparation of (Ba,Sr)TiO{sub 3}-polystrene core-shell nanoparticles by solvent-free surface-initiated atom transfer radical polymerization

    Energy Technology Data Exchange (ETDEWEB)

    Yang Xiaowei [State Key Laboratory of Materials-Oriented Chemical Engineering, School of Materials Science and Engineering, Nanjing University of Technology, 5 New model Road, Nanjing 210009 (China); Zeng Yanwei, E-mail: zengyanwei@tom.com [State Key Laboratory of Materials-Oriented Chemical Engineering, School of Materials Science and Engineering, Nanjing University of Technology, 5 New model Road, Nanjing 210009 (China); Cai Tongxiang; Hu Zhenxing [State Key Laboratory of Materials-Oriented Chemical Engineering, School of Materials Science and Engineering, Nanjing University of Technology, 5 New model Road, Nanjing 210009 (China)

    2012-07-15

    The polystyrene shells have been successfully grown on the barium strontium titanate (BST) nanocrystals, which were synthesized by microwave-activated glycothermal method, via a solvent-free surface-initiated atom transfer radical polymerization (SI-ATRP) after the 2-bromo-2-methylpropionic acid molecules (Br-MPA) were anchored at the surface of BST nanocrystals through ligand exchange with hydroxyl groups on their surfaces. These surface modified BST nanocrystals can then be perfectly dispersed in styrene monomer and act as macroinitiators for ATRP to yield BST-PS core-shell structured nanoparticles, which endow the BST nanocrystals with exceptionally good dispersibility and stability in hydrophobic solvents. The BST-PS core-shell structures were characterized by X-ray diffraction (XRD) technique and transmission electron microscopy (TEM). Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy (Raman), differential scanning calorimetry (DSC) and gel permeation chromatography were also employed to probe the Br-MPA and PS on the BST nanocrystals. It has been shown that after the BST nanocrystals are surface-modified with Br-MPA, the polymerization of styrene can steadily occur at the surface of BST nanocrystals to form a uniform polystyrene shell and its thickness can reach {approx}10 nm when the polymerization reaction is extended to 36 h, while no changes are found to take place with the BST nanocrystals. Compared with typical high molecular weight PS (M{sub n} = 6700), the as-obtained PS possess a relatively low molecular weight (M{sub n} = 5473) and a lower glass transition temperature (T{sub g} {approx} 93 Degree-Sign C). The research results demonstrate a viable strategy for the preparation of polymer-coated functional metal oxides nanocrystals, potentially useful in biological and nanoelectronic applications.

  16. Preparation of (Ba,Sr)TiO3-polystrene core-shell nanoparticles by solvent-free surface-initiated atom transfer radical polymerization

    International Nuclear Information System (INIS)

    The polystyrene shells have been successfully grown on the barium strontium titanate (BST) nanocrystals, which were synthesized by microwave-activated glycothermal method, via a solvent-free surface-initiated atom transfer radical polymerization (SI-ATRP) after the 2-bromo-2-methylpropionic acid molecules (Br-MPA) were anchored at the surface of BST nanocrystals through ligand exchange with hydroxyl groups on their surfaces. These surface modified BST nanocrystals can then be perfectly dispersed in styrene monomer and act as macroinitiators for ATRP to yield BST-PS core-shell structured nanoparticles, which endow the BST nanocrystals with exceptionally good dispersibility and stability in hydrophobic solvents. The BST-PS core-shell structures were characterized by X-ray diffraction (XRD) technique and transmission electron microscopy (TEM). Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy (Raman), differential scanning calorimetry (DSC) and gel permeation chromatography were also employed to probe the Br-MPA and PS on the BST nanocrystals. It has been shown that after the BST nanocrystals are surface-modified with Br-MPA, the polymerization of styrene can steadily occur at the surface of BST nanocrystals to form a uniform polystyrene shell and its thickness can reach ∼10 nm when the polymerization reaction is extended to 36 h, while no changes are found to take place with the BST nanocrystals. Compared with typical high molecular weight PS (Mn = 6700), the as-obtained PS possess a relatively low molecular weight (Mn = 5473) and a lower glass transition temperature (Tg ∼ 93 °C). The research results demonstrate a viable strategy for the preparation of polymer-coated functional metal oxides nanocrystals, potentially useful in biological and nanoelectronic applications.

  17. Alignment Studies for Tungsten Near L3 Sub-Shell Threshold Via Theoretical, Experimental and Empirical Methods

    Directory of Open Access Journals (Sweden)

    Ajay Sharma

    2013-08-01

    Full Text Available Alignment studies are made for tungsten near L3 sub-shell threshold using theoretical, experimental and empirical approaches. Experimentally to measure alignment parameter, the angular distribution of L x-rays of tungsten (W-74 is measured in the angular range 0° to 120°, where maximum anisotropy is expected. The experimental measurements are performed in XRF laboratories of Raja Ramanna Center for Advanced Technology (RRCAT, Indore, India using a three-dimensional double reflection set-up. The weighted average of alignment values with 10% error comes 0.155 ± 0.009. Theoretically, the value of alignment parameter A20 is calculated using non-relativistic dipole approximation in a point Coulomb potential and is found 0.151 at L3 threshold energy (10.676 keV. For empirical A20 evaluations, IGELCS interpolated experimental LXRF cross-section σ*Lg (g = α,  values of Mann et al with 8% reported errors are used along with the radiative decay rates. The comparison among theoretical, experimental and empirical values are similar and values being >0.1 at L3 threshold energy are certainly higher than the 5 to 8 percent uncertainties quoted in earlier experimental results.

  18. Alignment and orientation of atomic outer shells induced by electron and ion impact: Some recent developments and remaining problems

    International Nuclear Information System (INIS)

    Alignment and orientation of atoms in collision experiments with planar symmetry have now been studied for about 15 years and close to 500 papers have been produced, mainly devoted to S->P excitation. Despite the large variety of electron-atom, ion-atom and atom-atom collision systems considered, a unified framework for description of these phenomena is now emerging. This framework is a generalization of the original ideas of Macek and Jaecks and is based on consideration of symmetries, conservation laws, etc. The key parameters are directly related to the shape and dynamics of the charge cloud of the excited electron as well as to experimental observables. A brief review is given of this framework, and some current problems and prospects for the future are discussed. (orig.)

  19. Anticoagulant surface of 316 L stainless steel modified by surface-initiated atom transfer radical polymerization.

    Science.gov (United States)

    Guo, Weihua; Zhu, Jian; Cheng, Zhenping; Zhang, Zhengbiao; Zhu, Xiulin

    2011-05-01

    Polished 316 L stainless steel (SS) was first treated with air plasma to enhance surface hydrophilicity and was subsequently allowed to react with 2-(4-chlorosulfonylphenyl)ethyltrimethoxysilane to introduce an atom transfer radical polymerization (ATRP) initiator. Accordingly, the surface-initiated atom transfer radical polymerization of polyethylene glycol methacrylate (PEGMA) was carried out on the surface of the modified SS. The grafting progress was monitored by water contact angle measurements, X-ray photoelectron spectroscopy and atomic force microscopy. The polymer thickness as a function different polymerization times was characterized using a step profiler. The anticoagulative properties of the PEGMA modified SS surface were investigated. The results showed enhanced anticoagulative to acid-citrate-dextrose (ACD) blood after grafting PEGMA on the SS surface. PMID:21528878

  20. Systematic study of L-shell ionization of some rare earth elements by light ion bombardment

    International Nuclear Information System (INIS)

    Thin targets of La, Pr, Nd, Eu, Tb, Ho and Er were bombarded by 1H, 2H, 3H, 4He and 7Li projectiles. The production cross sections for the Lα1,2, Lβ1,3,4, Lβ2,5,7, Lγ1,5, Lγ2,3,6 and Ll transitions have been extracted and corresponding ionization cross sections for L1-, L2- and L3- subshells have been calculated and tabulated. 9 figs., 13 tabs., 37 refs. (author)

  1. Characterization of atomized extract of Opuntia ficusindica (L.) Mill. and assessment of its pharmaceutical potential

    OpenAIRE

    Cinthya Maria Pereira de Souza; Fernanda Silva Almeida; Valdir Florêncio Veiga Junior; Bolívar Ponciano Goulart de Lima Damasceno; Ana Cláudia Dantas Medeiros; Davi Pereira de Santana; José Alexsandro Silva

    2014-01-01

    Given the many traditional uses of Opuntia ficus-indica (L.) Mill. and the widespread employment of dry extracts in herbal medicine and phytocosmetics, the aim of this study is to characterize an atomized extract of O. ficus-indica cladodes, as well as to analyze its phytochemical composition and assay the total phenol content. In addition, the antioxidant, antimicrobial and photoprotective activities of the extract and its capacity to inhibit the enzyme tyrosinase wer...

  2. X-ray and inner-shell processes: Their impact on our understanding of atomic physics and atoms interacting with solids

    International Nuclear Information System (INIS)

    Atomic physics and the basic concepts of quantum theory have been probed in the last fifty years by using the techniques of optics and lasers in the visible range. The new powerful accelerators, storage rings, and various large scale devices, such as ion beams, synchrotron radiation, plasma confinement machines, powerful lasers, etc. developed by the nuclear physicists and high technology engineers have allowed, in the past three decades, new, unexpected and more general insights of atomic structure and more accurate checks of quantum mechanics. It is now possible to prepare any kind of atom or ion, having any number of electrons in any quantum states (atomic manipulations), and to trap or set them in defined places on surfaces. The study of these atomic species having electrons in any deep, or highly excited levels requires the use of electromagnetic transitions in a much wider range of wavelengths than in optics, and, because most of the time they are in autoionizing states, of Auger spectrometry. It is the purpose of this talk to review some of the most salient discoveries in the field since this time, to present some of the most recent and exciting results obtained in the last decade, and future prospects

  3. L-shell ionization studies of Pb and Bi with α particles

    International Nuclear Information System (INIS)

    Ionization cross sections for the L subshells of Pb and Bi by α-particle bombardment (2.2--8.2 MeV) have been determined from the experimental data and the currently available radiative transition probabilities, fluorescence yields, and Coster-Kronig factors. The measured ionization cross sections and their ratios are compared with the results of ECPSSR calculations [ECPSSR denotes perturbed-stationary-state (PSS) theory with energy-loss (E), Coulomb deflection (C), and relativistic (R) corrections]. The measured individual cross sections for L1 and L2 subshells deviated in opposite directions from the theory, whereas their sum shows good agreement. The L3 and total ionization cross sections obtained from the data also show good agreement with the ECPSSR theory. The ionization cross-section ratios σL1/σL2 and σL3/σL2 show large deviations from the ECPSSR theory. The experimental x-ray production cross-section ratios are found to be in better agreement with the theoretical results obtained from using ECPSSR ionization cross sections and the decay yield data of Xu and Xu [J. Phys. B 25, 695 (1992)] rather than those obtained from using the decay yield data of Krause [J. Phys. Chem. Ref. Data 8, 307 (1979)]. The x-ray production cross sections, however, are in better agreement with the theoretical results obtained from using the decay yield data of Krause. The measured centroid energy of the Lγ lines of Pb shows large deviations at high projectile energy, whereas for Bi large deviations are found at the low-energy region

  4. Atom-photon entanglement in the system with competing k-photon and l-photon transitions

    Institute of Scientific and Technical Information of China (English)

    Wu Qin; Fang Mao-Fa; Hu Yao-Hua

    2007-01-01

    We have investigated the evolution of the atomic quantum entropy and the entanglement of atom-photon in the system with competing k-photon and l-photon transitions by means of fully quantum theory, and examined the effects of competing photon numbers (k and l), the relative coupling strength between the atom and the two-mode field(λ/g),and the initial photon number of the field on the atomic quantum entropy and the entanglement of atom-photon.The results show that the multiphoton competing transitions or the large relative coupling strength can lead to the strong entanglement between atoms and photons. The maximal atom-photon entanglement can be prepared via the appropriate selection of system parameters and interaction time.

  5. 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.

  6. Atomic electronic states: the L-S and j-j coupling schemes and their correlation

    CERN Document Server

    Li, Wai-Kee

    2014-01-01

    In the first part of this paper, we review the assumption of the L-S coupling scheme, with which we derive the electronic states arising from a given atomic configuration. Then, with the aid of the spectral data of Group 15 elements, it becomes clear that the assumption of the L-S coupling scheme is no longer valid as we go farther and farther down the Periodic Table. In the second part, we introduce the j-j coupling scheme, which is seldom covered in standard inorganic chemistry texts, and contrast the assumptions of the two schemes. Next, we use two worked examples to demonstrate the derivation of electronic states with the j-j coupling scheme. Finally, the correlation between the states derived by L-S and j-j schemes is pictorially shown. It is believed a student, by also studying j-j coupling schemes (by no means a difficult task) along with the L-S scheme, will gain a better understanding of the concept of atomic electronic states.

  7. Experimental demonstration of direct L-shell x-ray fluorescence imaging of gold nanoparticles using a benchtop x-ray source

    OpenAIRE

    Manohar, Nivedh; Reynoso, Francisco J.; Cho, Sang Hyun

    2013-01-01

    Purpose: To develop a proof-of-principle L-shell x-ray fluorescence (XRF) imaging system that locates and quantifies sparse concentrations of gold nanoparticles (GNPs) using a benchtop polychromatic x-ray source and a silicon (Si)-PIN diode x-ray detector system.

  8. Origin and shape evolution of core-shell nanoparticles in Au-Pd: from few atoms to high Miller index facets

    Energy Technology Data Exchange (ETDEWEB)

    Bhattarai, Nabraj; Casillas, Gilberto; Khanal, Subarna; Velazquez Salazar, J. Jesus; Ponce, Arturo; Jose-Yacaman, Miguel, E-mail: miguel.yacaman@utsa.edu [University of Texas at San Antonio, Department of Physics and Astronomy (United States)

    2013-06-15

    Au-Pd core-shell nanocubes and triangular nanoparticles were systematically synthesized from a few Pd layers up to fully grown morphologies by a modified seed-mediated growth method. The shape evolution of Au-Pd core-shell nanoparticles from single crystal and singly twinned seed to final concave nanocube and triangular plates are presented at atomic level by Cs-corrected scanning transmission electron microscopy (STEM). The growth mechanism of both morphologies was studied throughout different sizes. It was found that the concave nanocubes grew from octahedral Au seeds due to fast growth along Left-Pointing-Angle-Bracket 111 Right-Pointing-Angle-Bracket directions; while the triangular nanoparticles grew from singly twinned Au seeds, growing twice as fast in Left-Pointing-Angle-Bracket 110 Right-Pointing-Angle-Bracket directions along the twin boundary; compared to the Left-Pointing-Angle-Bracket 111 Right-Pointing-Angle-Bracket direction perpendicular to the twin boundary. Both the concave nanocubes and triangular nanoparticles presented high index facet (HIF) surfaces that will increase the catalytic activity of different reactions.

  9. Origin and shape evolution of core–shell nanoparticles in Au–Pd: from few atoms to high Miller index facets

    International Nuclear Information System (INIS)

    Au–Pd core–shell nanocubes and triangular nanoparticles were systematically synthesized from a few Pd layers up to fully grown morphologies by a modified seed-mediated growth method. The shape evolution of Au–Pd core–shell nanoparticles from single crystal and singly twinned seed to final concave nanocube and triangular plates are presented at atomic level by Cs-corrected scanning transmission electron microscopy (STEM). The growth mechanism of both morphologies was studied throughout different sizes. It was found that the concave nanocubes grew from octahedral Au seeds due to fast growth along 〈111〉 directions; while the triangular nanoparticles grew from singly twinned Au seeds, growing twice as fast in 〈110〉 directions along the twin boundary; compared to the 〈111〉 direction perpendicular to the twin boundary. Both the concave nanocubes and triangular nanoparticles presented high index facet (HIF) surfaces that will increase the catalytic activity of different reactions.

  10. Time-resolved fluorescence spectroscopy of matrix-isolated silver atoms after pulsed excitation of inner-shell transitions

    Science.gov (United States)

    Hebert, T.; Wiggenhauser, H.; Schriever, U.; Kolb, D. M.

    1990-02-01

    The energy dissipation in matrix-isolated silver atoms after pulsed vacuum ultraviolet (VUV) excitation of 4d-5p transitions has been studied by time-resolved fluorescence spectroscopy. The decay behavior of the various fluorescence bands has been analyzed and a model for the relaxation process proposed within the framework of a two-dimensional configuration-coordinate diagram. If minute quantities of Ag2 are present in the matrix, the analysis requires consideration of energy transfer between silver atoms and dimers.

  11. The effect of phenomenological modeling of z-pinch implosions on the scaling of k-shell emission with atomic number and mass

    International Nuclear Information System (INIS)

    Recent 1-D phenomenological modeling of plasma turbulence by enhancing transport coefficients has shown that it is possible to achieve good agreement with experimental plasma conditions at stagnation, especially when compared to previous laminar flow calculations. Since this original phenomenological study focused upon only a single Physics International Inc. argon experiment, it is important to build a stronger foundation for this modeling. This is accomplished by: (1) including turbulence effects phenomenologically in the 1-D, radiation, MHD average fluid description of the turbulent flow by enhancing the resistivity Ω, viscosity υ, and heat conductivity κ transport coefficients; (2) finding a set of (κ,υ,Ω) coefficients that reasonably produces the stagnation temperatures and densities of a Physics International Inc. aluminum experiment; (3) this choice of transport coefficients is then tested for dependence on mass loading m and atomic number Z by comparing calculated implosion conditions with those found in a variety of PI aluminum and argon experiments. The authors find that the choice of enhanced transport coefficients that produces good agreement with the stagnation temperatures and densities of the single PI aluminum experiment also gives acceptable agreement for the other aluminum and argon experiments. Based on the presumption that a better representation of plasma conditions at stagnation also gives rise to more realistic K-shell yield scaling with atomic number, the minimum load mass and kinetic energy (machine energy) requirements needed to efficiently produce K-shell emission are calculated for aluminum and argon using enhanced transport calculations. These results are then extrapolated to other Z materials and compared with predictions of the original laminar flow scaling study. Implications of this work for large current machines will be presented

  12. Shell Venster

    International Nuclear Information System (INIS)

    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

  13. Investigation of the radiation properties of L- and M-shell X-pinch plasma x-ray sources using a transmission grating spectrometer

    International Nuclear Information System (INIS)

    A transmission grating spectrometer (TGS) with one dimensional spatial resolution was used to investigate the radiative properties of X-pinch plasmas produced using wires made of NiCr and CoNiCr alloys, and Mo. Experiments were carried out on the Cornell XP machine. The TGS was used to estimate of the energy yields of L-shell Cr and Ni, and M-shell Mo radiation. The absolute energy yields in the wavelength range 1042 A. The results are compared with data obtained previously with the TGS on a 1 MA pulse powered machine Zebra

  14. A Modern Approach to L-S Coupling in the Theory of Atomic Spectra

    Science.gov (United States)

    Doggett, Graham; Sutcliffe, Brian

    1998-01-01

    In a recent article on the theory of atomic spectroscopy (1), Haigh remarks that "Many introductory textbooks on spectroscopy give satisfactory accounts of Russell-Saunders (LS) coupling, but their treatment of jj coupling is generally very brief." Although we do not wish to dissent from his sentiments on j-j coupling, we wonder whether the treatment of L-S coupling usually offered in introductory texts for term enumeration is not too old-fashioned to still be considered entirely satisfactory. In this article we present an approach to the construction of L-S terms that makes contact with modern group theoretical and tensorial approaches to the theory of atomic spectra and is as easy to present and to comprehend as is the old microstates approach (2, 3). We believe that it is at least as easy to use as the approach of Guofan and Elizey (4) presented in this Journal some ten years ago: in fact, we have been teaching the enumeration of L-S terms for the past ten years using the methods presented in Section 2.

  15. High-precision atomic clocks with highly charged ions: nuclear spin-zero $f^{12}$-shell ions

    OpenAIRE

    Dzuba, V. A.; Derevianko, A; Flambaum, V. V.

    2012-01-01

    Optical atomic clocks using highly-charged ions hold an intriguing promise of metrology at the 19th significant figure. Here we study transitions within the $4f^{12}$ ground-state electronic configuration of highly charged ions. We consider isotopes lacking hyperfine structure and show that the detrimental effects of coupling of electronic quadrupole moments to gradients of trapping electric field can be effectively reduced by using specially chosen virtual clock transitions. The estimated sy...

  16. K{sub β} to K{sub α} X-ray intensity ratios and K to L shell vacancy transfer probabilities of Co, Ni, Cu, and Zn

    Energy Technology Data Exchange (ETDEWEB)

    Anand, L. F. M.; Gudennavar, S. B., E-mail: shivappa.b.gudennavar@christuniversity.in; Bubbly, S. G. [Christ University Bengaluru, Department of Physics (India); Kerur, B. R. [Gulbarga University Kalaburgi, Department of Physics (India)

    2015-12-15

    The K to L shell total vacancy transfer probabilities of low Z elements Co, Ni, Cu, and Zn are estimated by measuring the K{sub β} to K{sub α} intensity ratio adopting the 2π-geometry. The target elements were excited by 32.86 keV barium K-shell X-rays from a weak {sup 137}Cs γ-ray source. The emitted K-shell X-rays were detected using a low energy HPGe X-ray detector coupled to a 16 k MCA. The measured intensity ratios and the total vacancy transfer probabilities are compared with theoretical results and others’ work, establishing a good agreement.

  17. A combined DFT and restricted open-shell configuration interaction method including spin-orbit coupling: Application to transition metal L-edge X-ray absorption spectroscopy

    Science.gov (United States)

    Roemelt, Michael; Maganas, Dimitrios; DeBeer, Serena; Neese, Frank

    2013-05-01

    A novel restricted-open-shell configuration interaction with singles (ROCIS) approach for the calculation of transition metal L-edge X-ray absorption spectra is introduced. In this method, one first calculates the ground state and a number of excited states of the non-relativistic Hamiltonian. By construction, the total spin is a good quantum number in each of these states. For a ground state with total spin S excited states with spin S' = S, S - 1, and S + 1 are constructed. Using Wigner-Eckart algebra, all magnetic sublevels with MS = S, …, -S for each multiplet of spin S are obtained. The spin-orbit operator is represented by a mean-field approximation to the full Breit-Pauli spin-orbit operator and is diagonalized over this N-particle basis. This is equivalent to a quasi-degenerate treatment of the spin-orbit interaction to all orders. Importantly, the excitation space spans all of the molecular multiplets that arise from the atomic Russell-Saunders terms. Hence, the method represents a rigorous first-principles approach to the complicated low-symmetry molecular multiplet problem met in L-edge X-ray absorption spectroscopy. In order to gain computational efficiency, as well as additional accuracy, the excitation space is restricted to single excitations and the configuration interaction matrix is slightly parameterized in order to account for dynamic correlation effects in an average way. To this end, it is advantageous to employ Kohn-Sham rather than Hartree-Fock orbitals thus defining the density functional theory/ROCIS method. However, the method can also be used in an entirely non-empirical fashion. Only three global empirical parameters are introduced and have been determined here for future application of the method to any system containing any transition metal. The three parameters were carefully calibrated using the L-edge X-ray absorption spectroscopy spectra of a test set of coordination complexes containing first row transition metals. These

  18. A combined DFT and restricted open-shell configuration interaction method including spin-orbit coupling: Application to transition metal L-edge X-ray absorption spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Roemelt, Michael; Maganas, Dimitrios; Neese, Frank [Max-Planck Institute for Chemical Energy Conversion, Stiftstrasse 34-36, D-45470 Muelheim an der Ruhr (Germany); DeBeer, Serena [Max-Planck Institute for Chemical Energy Conversion, Stiftstrasse 34-36, D-45470 Muelheim an der Ruhr (Germany); Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853 (United States)

    2013-05-28

    A novel restricted-open-shell configuration interaction with singles (ROCIS) approach for the calculation of transition metal L-edge X-ray absorption spectra is introduced. In this method, one first calculates the ground state and a number of excited states of the non-relativistic Hamiltonian. By construction, the total spin is a good quantum number in each of these states. For a ground state with total spin S excited states with spin S Prime = S, S - 1, and S + 1 are constructed. Using Wigner-Eckart algebra, all magnetic sublevels with M{sub S}= S, Horizontal-Ellipsis , -S for each multiplet of spin S are obtained. The spin-orbit operator is represented by a mean-field approximation to the full Breit-Pauli spin-orbit operator and is diagonalized over this N-particle basis. This is equivalent to a quasi-degenerate treatment of the spin-orbit interaction to all orders. Importantly, the excitation space spans all of the molecular multiplets that arise from the atomic Russell-Saunders terms. Hence, the method represents a rigorous first-principles approach to the complicated low-symmetry molecular multiplet problem met in L-edge X-ray absorption spectroscopy. In order to gain computational efficiency, as well as additional accuracy, the excitation space is restricted to single excitations and the configuration interaction matrix is slightly parameterized in order to account for dynamic correlation effects in an average way. To this end, it is advantageous to employ Kohn-Sham rather than Hartree-Fock orbitals thus defining the density functional theory/ROCIS method. However, the method can also be used in an entirely non-empirical fashion. Only three global empirical parameters are introduced and have been determined here for future application of the method to any system containing any transition metal. The three parameters were carefully calibrated using the L-edge X-ray absorption spectroscopy spectra of a test set of coordination complexes containing first row

  19. A combined DFT and restricted open-shell configuration interaction method including spin-orbit coupling: Application to transition metal L-edge X-ray absorption spectroscopy

    International Nuclear Information System (INIS)

    A novel restricted-open-shell configuration interaction with singles (ROCIS) approach for the calculation of transition metal L-edge X-ray absorption spectra is introduced. In this method, one first calculates the ground state and a number of excited states of the non-relativistic Hamiltonian. By construction, the total spin is a good quantum number in each of these states. For a ground state with total spin S excited states with spin S′= S, S − 1, and S + 1 are constructed. Using Wigner-Eckart algebra, all magnetic sublevels with MS= S, …, −S for each multiplet of spin S are obtained. The spin-orbit operator is represented by a mean-field approximation to the full Breit-Pauli spin-orbit operator and is diagonalized over this N-particle basis. This is equivalent to a quasi-degenerate treatment of the spin-orbit interaction to all orders. Importantly, the excitation space spans all of the molecular multiplets that arise from the atomic Russell-Saunders terms. Hence, the method represents a rigorous first-principles approach to the complicated low-symmetry molecular multiplet problem met in L-edge X-ray absorption spectroscopy. In order to gain computational efficiency, as well as additional accuracy, the excitation space is restricted to single excitations and the configuration interaction matrix is slightly parameterized in order to account for dynamic correlation effects in an average way. To this end, it is advantageous to employ Kohn-Sham rather than Hartree-Fock orbitals thus defining the density functional theory/ROCIS method. However, the method can also be used in an entirely non-empirical fashion. Only three global empirical parameters are introduced and have been determined here for future application of the method to any system containing any transition metal. The three parameters were carefully calibrated using the L-edge X-ray absorption spectroscopy spectra of a test set of coordination complexes containing first row transition metals. These

  20. A combined DFT and restricted open-shell configuration interaction method including spin-orbit coupling: application to transition metal L-edge X-ray absorption spectroscopy.

    Science.gov (United States)

    Roemelt, Michael; Maganas, Dimitrios; DeBeer, Serena; Neese, Frank

    2013-05-28

    A novel restricted-open-shell configuration interaction with singles (ROCIS) approach for the calculation of transition metal L-edge X-ray absorption spectra is introduced. In this method, one first calculates the ground state and a number of excited states of the non-relativistic Hamiltonian. By construction, the total spin is a good quantum number in each of these states. For a ground state with total spin S excited states with spin S' = S, S - 1, and S + 1 are constructed. Using Wigner-Eckart algebra, all magnetic sublevels with MS = S,..., -S for each multiplet of spin S are obtained. The spin-orbit operator is represented by a mean-field approximation to the full Breit-Pauli spin-orbit operator and is diagonalized over this N-particle basis. This is equivalent to a quasi-degenerate treatment of the spin-orbit interaction to all orders. Importantly, the excitation space spans all of the molecular multiplets that arise from the atomic Russell-Saunders terms. Hence, the method represents a rigorous first-principles approach to the complicated low-symmetry molecular multiplet problem met in L-edge X-ray absorption spectroscopy. In order to gain computational efficiency, as well as additional accuracy, the excitation space is restricted to single excitations and the configuration interaction matrix is slightly parameterized in order to account for dynamic correlation effects in an average way. To this end, it is advantageous to employ Kohn-Sham rather than Hartree-Fock orbitals thus defining the density functional theory∕ROCIS method. However, the method can also be used in an entirely non-empirical fashion. Only three global empirical parameters are introduced and have been determined here for future application of the method to any system containing any transition metal. The three parameters were carefully calibrated using the L-edge X-ray absorption spectroscopy spectra of a test set of coordination complexes containing first row transition metals. These

  1. Algebraic tools for dealing with the atomic shell model. I. Wavefunctions and integrals for hydrogen-like ions

    Science.gov (United States)

    Surzhykov, Andrey; Koval, Peter; Fritzsche, Stephan

    2005-01-01

    Today, the 'hydrogen atom model' is known to play its role not only in teaching the basic elements of quantum mechanics but also for building up effective theories in atomic and molecular physics, quantum optics, plasma physics, or even in the design of semiconductor devices. Therefore, the analytical as well as numerical solutions of the hydrogen-like ions are frequently required both, for analyzing experimental data and for carrying out quite advanced theoretical studies. In order to support a fast and consistent access to these (Coulomb-field) solutions, here we present the DIRAC program which has been developed originally for studying the properties and dynamical behavior of the (hydrogen-like) ions. In the present version, a set of MAPLE procedures is provided for the Coulomb wave and Green's functions by applying the (wave) equations from both, the nonrelativistic and relativistic theory. Apart from the interactive access to these functions, moreover, a number of radial integrals are also implemented in the DIRAC program which may help the user to construct transition amplitudes and cross sections as they occur frequently in the theory of ion-atom and ion-photon collisions. Program summaryTitle of program:DIRAC Catalogue number: ADUQ Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADUQ Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Licensing provisions: None Computer for which the program is designed and has been tested: All computers with a license of the computer algebra package MAPLE [1] Program language used: Maple 8 and 9 No. of lines in distributed program, including test data, etc.:2186 No. of bytes in distributed program, including test data, etc.: 162 591 Distribution format: tar gzip file CPC Program Library subprograms required: None Nature of the physical problem: Analytical solutions of the hydrogen atom are widely used in very different fields of physics [2,3]. Despite of the rather simple structure

  2. Major role of multielectronic K-L inter-shell resonant recombination processes in Li- to O-like ions of Ar, Fe, and Kr

    CERN Document Server

    Beilmann, C; Mokler, P H; Bernitt, S; Keitel, C H; Ullrich, J; López-Urrutia, J R Crespo

    2013-01-01

    Dielectronic and higher-order resonant electron recombination processes including a K-shell excitation were systematically measured at high resolution in electron beam ion traps. Storing highly charged Ar, Fe, and Kr ions, the dependence on atomic number Z of the contribution of these processes to the total recombination cross section was studied and compared with theoretical calculations. Large higher-order resonant recombination contributions are found, especially for systems with 10shell quadruelectronic recombination were also observed. The experimental data obtained for the He-like to O-like isoelectronic sequences compare well with the results of advanced relativistic distorted-wave calculations employing multiconfiguration Dirac-Fock bound state wave fu...

  3. Lead determination at ng/mL level by flame atomic absorption spectrometry using a tantalum coated slotted quartz tube atom trap.

    Science.gov (United States)

    Demirtaş, İlknur; Bakırdere, Sezgin; Ataman, O Yavuz

    2015-06-01

    Flame atomic absorption spectrometry (FAAS) still keeps its importance despite the relatively low sensitivity; because it is a simple and economical technique for determination of metals. In recent years, atom traps have been developed to increase the sensitivity of FAAS. Although the detection limit of FAAS is only at the level of µg/mL, with the use of atom traps it can reach to ng/mL. Slotted quartz tube (SQT) is one of the atom traps used to improve sensitivity. In atom trapping mode of SQT, analyte is trapped on-line in SQT for few minutes using ordinary sample aspiration, followed by the introduction of a small volume of organic solvent to effect the revolatilization and atomization of analyte species resulting in a transient signal. This system is economical, commercially available and easy to use. In this study, a sensitive analytical method was developed for the determination of lead with the help of SQT atom trapping flame atomization (SQT-AT-FAAS). 574 Fold sensitivity enhancement was obtained at a sample suction rate of 3.9 mL/min for 5.0 min trapping period with respect to FAAS. Organic solvent was selected as 40 µL of methyl isobutyl ketone (MIBK). To obtain a further sensitivity enhancement inner surface of SQT was coated with several transition metals. The best sensitivity enhancement, 1650 fold enhancement, was obtained by the Ta-coated SQT-AT-FAAS. In addition, chemical nature of Pb species trapped on quartz and Ta surface, and the chemical nature of Ta on quartz surface were investigated by X-ray photoelectron spectroscopy (XPS) and Raman Spectroscopy. Raman spectrometric results indicate that tantalum is coated on SQT surface in the form of Ta2O5. XPS studies revealed that the oxidation state of Pb in species trapped on both bare and Ta coated SQT surfaces is +2. For the accuracy check, the analyses of standard reference material were performed by use of SCP SCIENCE EnviroMAT Low (EU-L-2) and results for Pb were to be in good agreement with

  4. Measurements of L-shell X-ray production cross-sections of Ag and Sb by low-energy electron impact

    Science.gov (United States)

    Zhao, J. L.; An, Z.; Zhu, J. J.; Tan, W. J.; Liu, M. T.

    2016-05-01

    The total L-shell X-ray production cross-sections of Ag and Sb elements were measured by detecting the characteristic X-rays induced by the electron impact in the energy range of 6-28 keV. In this experiment, the thin films with thick aluminum substrates were used as the targets, and the experimental setup was improved. The influence of multiple scattering of electrons penetrating the targets films, electrons reflected from the thick aluminum substrates and bremsstrahlung photons produced when incident electrons impacted the targets were corrected by using the Monte Carlo method. The experimental results determined in this paper were compared with some theoretical models and other available experimental data in the literature. It was shown that the L-shell X-ray production cross-sections of Ag and Sb elements measured in this paper were in good agreement with the theoretical predictions within the uncertainties.

  5. Interaction de l'atome d'hydrogene avec un champ laser intense et bref a derive de frequence

    Science.gov (United States)

    Ba, Harouna Sileye

    Nous presentons dans ce document une etude theorique de l'interaction entre l'atome d'hydrogene et un champ laser intense et bref a derive de frequence. Dans un premier temps, nous etablissons une methode basee sur les fonctions B-splines qui permet de decrire avec precision l'ensemble de la structure energetique du systeme atomique. Dans le second temps, nous developpons une approche non perturbative de type spectrale, basee sur la resolution exacte de l'equation de Schrodinger dependante du temps, pour decrire l'atome d'hydrogene en interaction avec un champ laser. Nous proposons particulierement une representation realiste d'une impulsion laser a derive de frequence. Finalement, nous etudions le processus d'ionisation au dessus du seuil de l'atome d'hydrogene soumis a une impulsion a derive de frequence. Nos resultats montrent que la derive de frequence laser permet de controler et d'optimiser le transfert de population de l'etat fondamental vers les etats electroniques intermediaires impliques dans le processus d'ionisation. Mots-cles : Atome d'hydrogene Fonctions B-splines Methode non perturbative spectrale Impulsion laser intense et breve Parametre de derive de frequence laser lonisation multiphotonique

  6. Radiation trapping and L\\'{e}vy flights in atomic vapours: an introductory review

    CERN Document Server

    Chevrollier, Martine

    2013-01-01

    Multiple scattering is a process in which a particle is repeatedly deflected by other particles. In an overwhelming majority of cases, the ensuing random walk can successfully be described through Gaussian, or normal, statistics. However, like a (growing) number of other apparently inofensive systems, diffusion of light in dilute atomic vapours eludes this familiar interpretation, exhibiting a superdiffusive behavior. As opposed to normal diffusion, whereby the particle executes steps in random directions but with lengths slightly varying around an average value (like a drunkard whose next move is unpredictable but certain to within a few tens of centimeters), superdiffusion is characterized by sudden abnormally long steps (L\\'{e}vy flights) interrupting sequences of apparently regular jumps which, although very rare, determine the whole dynamics of the system. The formal statistics tools to describe superdiffusion already exist and rely on stable, well understood distributions. As scientists become aware of,...

  7. Characterization of atomized extract of Opuntia ficusindica (L. Mill. and assessment of its pharmaceutical potential

    Directory of Open Access Journals (Sweden)

    Cinthya Maria Pereira Souza

    2014-04-01

    Full Text Available Given the many traditional uses of Opuntia ficus-indica (L. Mill. and the widespread employment of dry extracts in herbal medicine and phytocosmetics, the aim of this study is to characterize an atomized extract of O. ficus-indica cladodes, as well as to analyze its phytochemical composition and assay the total phenol content. In addition, the antioxidant, antimicrobial and photoprotective activities of the extract and its capacity to inhibit the enzyme tyrosinase were assessed, with a view to its pharmaceutical use. The physicochemical characterization was performed by pharmacopoeial tests, thermal analysis and infrared spectroscopy. Phytochemicals were analyzed by thin layer chromatography and total phenols by spectroscopy in the visible region. Antioxidant activity was detected by the method of free radical (DPPH● scavenging and antimicrobial activity by the agar diffusion method, while inhibition of tyrosinase was estimated by the diphenolase activity assay and photoprotective activity by a spectrophotometric method. The pharmacopeial tests, IR spectroscopy and thermal analysis enabled the atomized extract to be characterized. Concerning the potential for pharmaceutical use, it was found that, under the study conditions, the extract did not show any antioxidant, antimicrobial or photoprotective activity. However, it did show a modest tyrosinase inhibitory capacity. The originality of the proposed research on O. ficus-indica in the pharmaceutical field should be emphasized, as it opens new prospects for the study of a species that is so abundant and adapted to Brazilian semi-arid regions.

  8. Fabrication and characterization of heparin-grafted poly-L-lactic acid-chitosan core-shell nanofibers scaffold for vascular gasket.

    Science.gov (United States)

    Wang, Ting; Ji, Xuyuan; Jin, Lin; Feng, Zhangqi; Wu, Jinghang; Zheng, Jie; Wang, Hongyin; Xu, Zhe-Wu; Guo, Lingling; He, Nongyue

    2013-05-01

    Electrospun nanofibers were widely studied to be applied as potential materials for tissue engineering. A new technology to make poly-l-lactic acid/chitosan core/shell nanofibers from heterologous solution by coaxial electrospinning technique was designed for vascular gasket. Chitosan surface was cross-linked by genipin and modified by heparin. Different ratios of PLA/CS in heterologous solution were studied to optimize the surface morphology of fibers. Clean core-shell structures formed with a PLA/CS ratio at 1:3. Superior biocompatibility and mechanical properties were obtained by optimizing the core-shell structure morphology and surface cross-linking of chitosan. UE7T-13 cells grew well on the core-shell structure fibers as indicated by methylthiazolyldiphenyl-tetrazolium bromide (MTT) results and scanning electron microscopy (SEM) images. Compared with the pure PLA fiber meshes and commercial vascular patch, PLA/CS core-shell fibers had better mechanical strength. The elastic modulus was as high as 117.18 MPa, even though the yield stress of the fibers was lower than that of the commercial vascular patch. Attachment of red blood cell on the fibers was evaluated by blood anticoagulation experiments and in vitro blood flow experiments. The activated partial thromboplastin time (APTT) and prothrombin time (PT) value from PLA/CS nanofibers were significantly longer than that of pure PLA fibers. SEM images indicated there were hardly any red blood cells attached to the fibers with chitosan coating and heparin modification. This type of fiber mesh could potentially be used as vascular gasket. PMID:23586670

  9. Absolute L-shell ionization and X-ray production cross sections of Lead and Thorium by 16-45 keV electron impact

    CERN Document Server

    Rahangdale, H V; De, S; Santos, J P; Mitra, D; Guerra, M; Saha, S

    2015-01-01

    The absolute L subshell specific electron impact ionization cross sections near the ionization threshold (16 < E < 45 keV) of Lead and Thorium are obtained from the measured L X-ray production cross sections. Monte Carlo simulation is done to account for the effect of the backscattered electrons and the final experimental results are compared with calculations performed using distorted wave Born approximation and the modified relativistic binary encounter Bethe model.The sensitivity of the results on the atomic parameters is explored. Observed agreements and discrepancies between the experimental results and theoretical estimates, and their dependence on the specific atomic parameters are reported.

  10. Influence of binder system and temperature on rheological properties of water atomized 316L powder injection moulding feedstocks

    OpenAIRE

    Uğur GÖKMEN; Türker, Mehmet; ÇİNİCİ, Hanifi

    2016-01-01

    In order to obtain a proper powder injection molding the rheological behavior of feedstocks should be known. To determine the binder effect on the rheological behavior of 316L stainless steel powders feedstock two different feedstock were prepared. In the current experiments water atomized 316L stainless steel powders (-20 µm) were used. Two types of binders, one of which is mainly paraffin wax can be dissolved in heptane and the other Polietilenglikol (PEG) based and can be dissolved in wate...

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

    KAUST Repository

    Wang, Ruiqi

    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.

  12. THE ACCUMULATION AND DEPURATION OF NO. 2 FUEL OIL BY THE SOFT SHELL CLAM, 'MYA ARENARIA L.'

    Science.gov (United States)

    Young soft shell clams, Mya arenaria, were exposed to subacute concentrations of No. 2 fuel oil-in-water emulsions under simulated winter (4 C) spill conditions. A pattern of accumulation and discharge of petroleum constituents, an experimental depuration time (biological half li...

  13. Facile synthesis and characterization of highly fluorescent and biocompatible N-acetyl-l-cysteine capped CdTe/CdS/ZnS core/shell/shell quantum dots in aqueous phase

    International Nuclear Information System (INIS)

    The synthesis of water-soluble quantum dots (QDs) in aqueous phase has received much attention recently. To date various kinds of QDs such as CdTe, CdSe, CdTe/CdS and CdSe/ZnS have been synthesized by aqueous methods. However, generally poor-quality QDs (photoluminescent quantum yield (PLQY) lower than 30%) are obtained via this method and the 3-mercaptopropionic acid stabilizer is notorious for its toxicity and awful odor. Here we introduce a novel thiol ligand, N-acetyl-l-cysteine, as an ideal stabilizer that is successfully employed to synthesize high-quality CdTe/CdS/ZnS QDs via a simple aqueous phase. The core/shell/shell structures of the CdTe/CdS/ZnS QDs were verified by x-ray photoelectron spectroscopy, energy dispersive x-ray spectroscopy, x-ray powder diffraction and transmission electron microscopy. These QDs not only possess a high PLQY but also have excellent photostability and favorable biocompatibility, which is vital for many biological applications. This type of water-dispersed QD is a promising candidate for fluorescent probes in biological and medical fields. (paper)

  14. In situ study by atomic force microscopy of localised corrosion on a 304L stainless steel

    International Nuclear Information System (INIS)

    At this time, the understanding of the initiation of localized corrosion on stainless steels (SS) is still limited. In this context, the present work aimed at observing in situ by Atomic Force Microscopy (AFM) the initiation of corrosion pits and stress corrosion cracking (SCC) cracks. In order to complete the project, a new technique associating an AFM, an electrochemical cell and a traction platform as been developed. It allows in situ imaging of the surface evolutions of a 304L SS at the nano-scale. under controlled potential and/or under stress conditions. We show that corrosion pits initiate preferentially in relation with nano-metric defects of the surface. For the first time, a real-time kinetic study of the first steps of nano-metric pits growth has been performed. This study corroborates the 'point-defect' model (vertical pit growth speed of 0.18 angstrom.s-1, current densities inside pits evaluated to 73 μjA.cm-2. Combined with the EBSD technique (Electron Backscattered Diffraction), the AFM allows a total indexing of the activated slip systems during deformation and give information about the number of emerged dislocations (few units). The effect of strain hardening at the nano-scale on pitting susceptibility has been investigated: 70% of the pits set up at strain hardened areas. To explain this phenomenon, we propose a simple model based on the modification of the local work function of the surface due to local stress gradients. Concerning SCC, the first in situ observations seem to validate Magnin's mechanism: crack initiation appears at strain concentration spots. Observed after anodization of our 304L surface, organized arrays of nano-cavities (period of 50-100 nm) have been analyzed. In collaboration with an INSERM team, we showed that such nano-structured surfaces increase the adhesion and differentiation of bone cells. (author)

  15. QUARK DYNAMICS IN ATOMIC NUCLEI AND QUARK SHELLS Динамика кварков в атомных ядрах и кварковые оболочки

    Directory of Open Access Journals (Sweden)

    Trunev A. P.

    2013-02-01

    Full Text Available In this article, we consider a system of Dirac equations describing the dynamics of quarks in the metric of the atomic nuclei. We found out, that the binding energy of the nucleons for all known nuclides depends on the content of the quarks. The resulting dependence of the energy of the nucleons shows a quark shells, similar electron shells

  16. QUARK DYNAMICS IN ATOMIC NUCLEI AND QUARK SHELLS Динамика кварков в атомных ядрах и кварковые оболочки

    Directory of Open Access Journals (Sweden)

    Trunev A. P.

    2013-02-01

    Full Text Available In this paper we consider a system of Dirac equations describing the dynamics of quarks in the metric of the atomic nuclei. We found out, that the binding energy of the nucleons for all known nuclides depends on the content of the quarks. The resulting dependence of the energy of the nucleons shows a quark shells, similar to electron shells. Our basic assumption is that each nucleon in the nucleus loses its individuality by dissociation to individual quarks that form quark shells. These shells are filled sequentially, just as filled electron shells. Since the nucleons are composed of two types of quarks, there are two types of shells that are filled with u and d quarks, respectively. In this case, the binding energy per nucleon depends on the concentration of quarks in the shells and the energy of the interaction of quarks.

  17. AGILE as a particle detector: Magnetospheric measurements of 10-100 MeV electrons in L shells less than 1.2

    Science.gov (United States)

    Argan, A.; Piano, G.; Tavani, M.; Trois, A.

    2016-04-01

    We study the capability of the AGILE gamma ray space mission in detecting magnetospheric particles (mostly electrons) in the energy range 10-100 MeV. Our measurements focus on the inner magnetic shells with L ≲ 1.2 in the magnetic equator. The instrument characteristics and a quasi-equatorial orbit of ˜500 km altitude make it possible to address several important properties of the particle populations in the inner magnetosphere. We review the on board trigger logic and study the acceptance of the AGILE instrument for particle detection. We find that the AGILE effective geometric factor (acceptance) is R≃50 cm2 sr for particle energies in the range 10-100 MeV. Particle event reconstruction allows to determine the particle pitch angle with the local magnetic field with good accuracy. We obtain the pitch angle distributions for both the AGILE "pointing" phase (July 2007 to October 2009) and the "spinning" phase (November 2009 to present). In spinning mode, the whole range (0-180 degrees) is accessible every 7 min. We find a pitch angle distribution of the "dumbbell" type with a prominent depression near α = 90° which is typical of wave-particle resonant scattering and precipitation in the inner magnetosphere. Most importantly, we show that AGILE is not affected by solar particle precipitation events in the magnetosphere. The satellite trajectory intersects magnetic shells in a quite narrow range (1.0 ≲ L ≲ 1.2); AGILE then has a high exposure to a magnetospheric region potentially rich of interesting phenomena. The large particle acceptance in the 10-100 MeV range, the pitch angle determination capability, the L shell exposure, and the solar-free background make AGILE a unique instrument for measuring steady and transient particle events in the inner magnetosphere.

  18. Investigation of the radiation properties of L- and M-shell X-pinch plasma x-ray sources using a transmission grating spectrometer

    Science.gov (United States)

    Fedin, D. A.; Kantsyrev, V. L.; Shlyaptseva, A. S.; Mitchell, M. D.; Song, B. M.; Pikuz, S. A.; Shelkovenko, T. A.; Chandler, K. M.; Hammer, D. A.; Maxson, L. M.

    2004-10-01

    A transmission grating spectrometer (TGS) with one dimensional spatial resolution was used to investigate the radiative properties of X-pinch plasmas produced using wires made of NiCr and CoNiCr alloys, and Mo. Experiments were carried out on the Cornell XP machine. The TGS was used to estimate of the energy yields of L-shell Cr and Ni, and M-shell Mo radiation. The absolute energy yields in the wavelength range 10NiCr, and 20-50 J for M-shell Mo). An analysis of the spatial structure of X-pinch emission regions in different wavelength ranges shows that the source structure is changing with wavelength and the size varies from less than 0.1 up to 1 mm. For example, in one Mo X-pinch test shown, three separate soft x-ray sources radiating in the wavelength range λ42 Å. The results are compared with data obtained previously with the TGS on a 1 MA pulse powered machine Zebra.

  19. Diffusivities and atomic mobilities in disordered fcc and ordered L1{sub 2} Ni–Al–W alloys

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Chong [State Key Lab of Powder Metallurgy, Central South University, Changsha, Hunan 410083 (China); Zhang, Lijun, E-mail: xueyue168@gmail.com [State Key Lab of Powder Metallurgy, Central South University, Changsha, Hunan 410083 (China); Xin, Jinghua; Wang, Yaru [State Key Lab of Powder Metallurgy, Central South University, Changsha, Hunan 410083 (China); Du, Yong, E-mail: yong-du@csu.edu.cn [State Key Lab of Powder Metallurgy, Central South University, Changsha, Hunan 410083 (China); Luo, Fenghua [State Key Lab of Powder Metallurgy, Central South University, Changsha, Hunan 410083 (China); Zhang, Zhongjian; Xu, Tao; Long, Jianzhan [State Key Lab of Cemented Carbides, Zhuzhou, Hunan 412000 (China)

    2015-10-05

    Highlights: • The atomic mobilities for fcc Al–W, fcc Ni–W, fcc Ni–Al–W and L1{sub 2} Ni–Al–W alloys were critically assessed. • The impurity diffusivity of W in fcc-Al was obtained via first-principles calculations. • The calculated results agree well with the diffusivities available in the literature. • Two fcc/L1{sub 2}-type diffusion couples were prepared and the concentration-distance profiles were measured. • The model-predicted concentration profiles agree well with the experimental data in the literature and in the present work. - Abstract: Based on various experimentally measured diffusivities available in the literature together with the reported thermodynamic parameters, the atomic mobilities for disordered fcc and ordered L1{sub 2} Ni–Al–W alloys were assessed on the basis of a recently developed phenomenological model incorporated in the DICTRA software. In order to provide the missing impurity diffusion coefficients of W in fcc-Al, first-principles calculations were utilized in the present work. Comprehensive comparisons between the calculated and experimental diffusion coefficients show that all the experimental data can be well reproduced by the atomic mobilities obtained in the present work. In order to further verify the reliability of the presently obtained atomic mobilities, two fcc/L1{sub 2}-type diffusion couples (i.e., Ni–5 at.% Al–5 at.% W/Ni–20 at.% Al–4 at.% W and Ni/Ni–22 at.% Al–2 at.% W) were prepared and the concentration-distance profiles after annealing at 1323 K for 86.4 ks were measured. The excellent agreement between the model-predicted concentration-distance profiles and the experimental data indicates that the presently obtained atomic mobilities in fcc/L1{sub 2} Ni–Al–W alloys are reliable.

  20. Spectroscopic atom symbolism

    International Nuclear Information System (INIS)

    Quantum numbers are introduced of the individual electrons of a multi-electron atom as are the concepts of electron configuration and configuration state diagram. An atom is described in Russell-Saunders approximation using the vector model concept. Overall quantum numbers are introduced for the electron shell and their relationships are discussed to the quantum numbers of the individual shell electrons. (author)

  1. Richard L. Greene Dissertation Award in Experimental Condensed Matter or Materials Physics Talk: Towards single atom magnets

    Science.gov (United States)

    Baumann, Susanne

    Magnetic anisotropy is a fundamental property of magnetic materials that governs the stability and directionality of their magnetization. At the atomic level, magnetic anisotropy originates from anisotropy in the orbital angular momentum (L) and the spin-orbit coupling that connects the spin moment of a magnetic atom to the spatial symmetry of its ligand field environment. Generally, the ligand field, that is necessary for the anisotropy, also quenches the orbital moment and reduces the total magnetic moment of the atom to its spin component. However, careful design of the coordination geometry of a single atom can restore the orbital moment while inducing uniaxial anisotropy, as we present here for single atoms deposited on top of a thin MgO film. Scanning tunneling spectroscopy and x-ray absorption spectroscopy measurements show a large magnetic anisotropy of 19 meV for iron and 58 meV for cobalt, as well as relaxation times of many milliseconds. These results offer a strategy, based on symmetry arguments and careful tailoring of the interaction with the environment, for the rational design of nanoscopic permanent magnets and single atom magnets.

  2. Atomes une exploration visuelle de tous les éléments connus dans l'univers

    CERN Document Server

    Gray, Theodore

    2013-01-01

    Quelle est leur température critique ? Qu'est-ce que la masse atomique, la densité d'un matériau, l'ordre de remplissage des électrons ? Cet ouvrage invite avec pédagogie et humour à un passionnant voyage au pays des éléments, à partir de leur tableau périodique universel. Soutenue par une exploration visuelle qui montre l'élément à l'état pur mais aussi ses composés et ses applications les plus caractéristiques dans la vie quotidienne, cette approche pratique offre une combinaison parfaite de science chimique et de photographies, qui séduira les lecteurs les plus avertis comme tous les autres habitants sensibles de l'univers.

  3. Theoretical description of atomic photoionization by attosecond XUV pulses in a strong laser field: the case of p-shell ionization

    International Nuclear Information System (INIS)

    A theoretical description of attosecond photoionization in the presence of a strong laser field, based on the numerical solution of the Schroedinger equation, is extended to the case of p-shell ionization. In particular, Ar(3p) photoionization is considered. The main difference between this case and the previously considered case of s-shell ionization stems from the interference of the two dipole allowed channels of p-shell photoionization, which determines the angular distribution of photoelectrons in the absence of the laser field. The latter additionally distorts the angular distributions. We also extend to the initial p-shell case the model based on the strong-field approximation (SFA), which has been suggested earlier. At high photoelectron energy and low laser intensity both calculations give similar results. However, at low electron energy the SFA is inadequate. The dependence of the angular distribution on the carrier-envelope phase and the effects of orbital polarization are considered

  4. L-series X-ray yields of kaonic 3He and 4He atoms in gaseous targets

    International Nuclear Information System (INIS)

    The SIDDHARTA experiment measured X-rays from kaonic helium atoms using, for the first time, gaseous 3He and 4He targets. Clear patterns of the L-series X-rays of kaonic 3He and 4He atoms were observed. By using accurate Monte Carlo simulations, the absolute yields of these X-ray transitions were determined to be Y(3d → 2p) = 25.0-5.8+6.7 % for 3He (0.96 g/l), Y(3d → 2p) = 23.1-4.2+6.0 % for 4He (1.65 g/l), and Y(3d → 2p) = 17.2-9.5+2.6 % for 4He (2.15g/l). In addition, the yields Y (nd → 2p), with n > 3 were also determined. The measured yields provide valuable information for understanding the cascade processes of kaonic helium atoms as a function of the target density. (orig.)

  5. L-series X-ray yields of kaonic 3He and 4He atoms in gaseous targets

    Science.gov (United States)

    Bazzi, M.; Beer, G.; Berucci, C.; Bragadireanu, A. M.; Cargnelli, M.; Curceanu, C.; d'Uffizi, A.; Fiorini, C.; Ghio, F.; Guaraldo, C.; Hayano, R. S.; Iliescu, M.; Ishiwatari, T.; Iwasaki, M.; Sandri, P. Levi; Marton, J.; Okada, S.; Pietreanu, D.; Ponta, T.; Quaglia, R.; Romero Vidal, A.; Sbardella, E.; Scordo, A.; Shi, H.; Sirghi, D. L.; Sirghi, F.; Tatsuno, H.; Vazquez Doce, O.; Wünschek, B.; Widmann, E.; Zmeskal, J.

    2014-05-01

    The SIDDHARTA experiment measured X-rays from kaonic helium atoms using, for the first time, gaseous 3He and 4He targets. Clear patterns of the L-series X-rays of kaonic 3He and 4He atoms were observed. By using accurate Monte Carlo simulations, the absolute yields of these X-ray transitions were determined to be Y(3 d → 2 p) = 25.0{-5.8/+6.7}% for 3He (0.96 g/l), Y(3 d → 2 p) = 23.1{-4.2/+6.0}% for 4He (1.65 g/l), and Y(3 d → 2 p) = 17.2{-9.5/+2.6}% for 4He (2.15g/l). In addition, the yields Y ( nd → 2 p), with n > 3 were also determined. The measured yields provide valuable information for understanding the cascade processes of kaonic helium atoms as a function of the target density.

  6. L-series X-ray yields of kaonic {sup 3}He and {sup 4}He atoms in gaseous targets

    Energy Technology Data Exchange (ETDEWEB)

    Bazzi, M.; Curceanu, C.; D' Uffizi, A.; Guaraldo, C.; Iliescu, M.; Sandri, P.L.; Sbardella, E.; Scordo, A.; Tatsuno, H. [Laboratori Nazionali di Frascati, INFN, Via E. Fermi 40, C.P. 13, Frascati (Italy); Beer, G. [University of Victoria, Department of Physics and Astronomy, STN CNC, P.O. Box 1700, Victoria (Canada); Berucci, C. [Laboratori Nazionali di Frascati, INFN, Via E. Fermi 40, C.P. 13, Frascati (Italy); Stefan-Meyer-Institut fuer subatomare Physik, Wien (Austria); Bragadireanu, A.M.; Pietreanu, D.; Sirghi, D.L.; Sirghi, F. [Laboratori Nazionali di Frascati, INFN, Via E. Fermi 40, C.P. 13, Frascati (Italy); IFIN-HH, Institutul National pentru Fizica si Inginerie Nucleara Horia Hulubei, Magurele (Romania); Cargnelli, M.; Ishiwatari, T.; Marton, J.; Shi, H.; Wuenschek, B.; Widmann, E.; Zmeskal, J. [Stefan-Meyer-Institut fuer subatomare Physik, Wien (Austria); Fiorini, C.; Quaglia, R. [Politecnico di Milano, Dipartimento di Elettronica, Informazione e Bioingegneria, Milano (Italy); INFN, Sezione di Milano, Milano (Italy); Ghio, F. [INFN, Sezione di Roma I (Italy); Instituto Superiore di Sanita, Roma (Italy); Hayano, R.S. [University of Tokyo, Hongo, Bunkyo-ku, Tokyo (Japan); Iwasaki, M.; Okada, S. [RIKEN, Institute of Physical and Chemical Research, 2-1 Hirosawa, Wako, Saitama (Japan); Ponta, T. [IFIN-HH, Institutul National pentru Fizica si Inginerie Nucleara Horia Hulubei, Magurele (Romania); Romero Vidal, A. [Universidade de Santiago de Compostela, Santiago de Compostela (Spain); Vazquez Doce, O. [Laboratori Nazionali di Frascati (Italy); INFN, Frascati (Italy); Technische Universitaet Muenchen, Excellence Cluster Universe, Garching (Germany); Collaboration: The SIDDHARTA Collaboration

    2014-05-15

    The SIDDHARTA experiment measured X-rays from kaonic helium atoms using, for the first time, gaseous {sup 3}He and {sup 4}He targets. Clear patterns of the L-series X-rays of kaonic {sup 3}He and {sup 4}He atoms were observed. By using accurate Monte Carlo simulations, the absolute yields of these X-ray transitions were determined to be Y(3d → 2p) = 25.0{sub -5.8} {sup +6.7} % for {sup 3}He (0.96 g/l), Y(3d → 2p) = 23.1{sub -4.2} {sup +6.0} % for {sup 4}He (1.65 g/l), and Y(3d → 2p) = 17.2{sub -9.5} {sup +2.6} % for {sup 4}He (2.15g/l). In addition, the yields Y (nd → 2p), with n > 3 were also determined. The measured yields provide valuable information for understanding the cascade processes of kaonic helium atoms as a function of the target density. (orig.)

  7. Studies of L-shell x-ray production for fast ions on elements with Z greater than or equal to 58

    International Nuclear Information System (INIS)

    Studies of L-shell and L-subshell ionization of elements with Z greater than or equal to 58 were accomplished using Si(Li) detector systems in which the major transitions may be resolved. The transitions observed populate the LI-, LII-, and LIII-subshells following ionization by ion species H, He, Li, C and O. Comparison to the nonrelativistic theories which employ screened hydrogenic wave functions has established trends which indicate that the inclusion of effects for increased binding of the target electrons and hyperbolic trajectories for the incident ions give improved agreement between theory and experiment. The inclusion of such effects as suggested by W. Brandt and G. Lapicki for the PWBA will be discussed

  8. Core–shell photoanode developed by atomic layer deposition of Bi2O3 on Si nanowires for enhanced photoelectrochemical water splitting

    International Nuclear Information System (INIS)

    Core–shell nanowire (NW) arrays, which feature a vertically aligned n-type Si NW core and a p-type α-Bi2O3 shell, are developed as a highly efficient photoanode that is suitable for water splitting. The morphology and structure of the heterostructure were characterized by scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDS), high-resolution transmission electron microscopy (HRTEM), x-ray photoelectron spectroscopy (XPS), and x-ray diffraction (XRD). The deposition of Bi2O3 nanolayers on the surface of the smooth Si NWs causes the surface of the NWs to become rough. The as-prepared core–shell NW photoelectrode has a relatively low reflectance in the visible light region, suggesting good light absorption. The core–shell NW arrays show greatly improved photoelectrochemical water-splitting performance. Photoelectrochemical stability for over 16 h under constant light illumination and fixed bias potential was achieved, illustrating the good stability of this core–shell NW photoanode. These Si/Bi2O3 core–shell NW arrays effectively combine the light absorption ability of the Si NWs and the wide energy gap and chemical stability of Bi2O3 for water splitting. This study furthers the attempts to design photoanodes from low-cost, abundant materials for applications in water splitting and photovoltaics. (paper)

  9. Attempt at elucidation of the role of fatty acids in the resistance of Pinus silvestris L. seeds to infection by damping-off fungi in dependence on the colour of their seed shells

    Directory of Open Access Journals (Sweden)

    Andrzej Grzywacz

    2015-05-01

    Full Text Available The seed shells of the pine (Pinus silvestris L. contain in dependence on their colour different amounts of the particular fatty acids. Some of the latter are toxic to the fungi causing damping-off of seedlings. The difference in content of toxic fatty acids between the black and the fallow seed shells may explain the mechanism of their different resistance to infection by damping-off fungi.

  10. Attempt at elucidation of the role of fatty acids in the resistance of Pinus silvestris L. seeds to infection by damping-off fungi in dependence on the colour of their seed shells

    OpenAIRE

    Andrzej Grzywacz; Jadwiga Rosochacka

    2015-01-01

    The seed shells of the pine (Pinus silvestris L.) contain in dependence on their colour different amounts of the particular fatty acids. Some of the latter are toxic to the fungi causing damping-off of seedlings. The difference in content of toxic fatty acids between the black and the fallow seed shells may explain the mechanism of their different resistance to infection by damping-off fungi.

  11. L-shell x-ray production cross sections in Nd, Gd, Ho, Yb, Au and Pb for 25-MeV carbon and 32-MeV oxygen ions

    International Nuclear Information System (INIS)

    L-shell x-ray production cross sections in 60Nd, 64Gd, 67Ho, 70Yb, 79Au and 82Pb have been measured for incident 25 MeV 612C/sup +q/(q = 4,5,6) and 32 MeV 816O/sup +q/(q = 5,7,8) ions. Measurements were made on targets ranging in thickness from 1 to 100 μg/cm2. Echancement in the L-shell x-ray production cross section for projectiles with one or two K-shell vacancies over those for projectiles with no K-shell vacancies is observed. The sum of direct ionization to the continuum (DI) plus electron capture (EC) to the L,M,N ... shells and EC to the K-shell of the projectile have been extracted from the data. Calculations in the first Born approximation are approx. 10 times larger than the data. Predictions of the ECPSSR theory that accounts for the energy-loss, Coulomb deflection, perturbed-stationary state, and relativistic effects are in good agreement with the data for both ions

  12. L-shell X-ray production cross sections in Nd, Gd, Ho, Yb, Au and Pb for 25-MeV carbon and 32-MeV oxygen ions

    International Nuclear Information System (INIS)

    L-shell X-ray production cross sections in 60Nd, 64Gd, 67Ho, 70Yb, 79Au and 82Pb have been measured for incident 25 MeV 612Csup(+q) (q=4, 5, 6) and 32 Me V816Osup(+q) (q=5, 7, 8) ions. Measurements were made on targets ranging in thickness from 1 to 100μg/cm2. Enhancement in the L-shell X-ray production cross-sections for projectiles with one or two K-shell vacancies over those for projectiles with no K-shell vacancies is observed. The sum of direct ionization to the continuum (DI) plus electron capture (EC) to the L, M, N... shells and EC to the K-shell of the projectile have been extracted from the data. Calculations in the first Born approximation are proportional 10 times larger than the data. Predictions of the ECPSSR theory that accounts for the energy-loss, Coulomb deflection, perturbed-stationary state and relativistic effects are in good agreement with the data for both ions. (orig.)

  13. l- and n-changing collisions during interaction of a pulsed beam of Li Rydberg atoms with CO2

    International Nuclear Information System (INIS)

    The pulsed Li atomic beam produced in our experiment is based on controlled transversely-excited-atmospheric CO2 laser-induced ablation of a Li metal target. The atomic beam is propagated in vacuum or in CO2 gas at low pressure. Atoms in the beam are probed by laser-induced fluorescence spectroscopy. This allows the determination of time-of-flight and velocity distributions. Li Rydberg states (n=5--13) are populated in the beam by two-step pulsed-laser excitation. The excited atoms interact with CO2 molecules. l- and n-changing cross sections are deduced from the time evolution of the resonant or collision-induced fluorescence following this selective excitation. l-changing cross sections of the order of 104 A2 are measured; they increase with n as opposed to the plateau observed for Li/sup */ colliding with a diatomic molecule. This behavior is qualitatively well explained in the framework of the free-electron model. n yields n' changing processes with large cross sections (10--100 A2) are also observed even in the case of large electronic energy change (ΔE/sub nn'/>103 cm/sup -1/). These results can be interpreted in terms of resonant-electronic to vibrational energy transfers between Li Rydberg states and CO2 vibrational modes

  14. l- and n-changing collisions during interaction of a pulsed beam of Li Rydberg atoms with CO2

    Science.gov (United States)

    Dubreuil, B.; Harnafi, M.

    1989-07-01

    The pulsed Li atomic beam produced in our experiment is based on controlled transversely-excited-atmospheric CO2 laser-induced ablation of a Li metal target. The atomic beam is propagated in vacuum or in CO2 gas at low pressure. Atoms in the beam are probed by laser-induced fluorescence spectroscopy. This allows the determination of time-of-flight and velocity distributions. Li Rydberg states (n=5-13) are populated in the beam by two-step pulsed-laser excitation. The excited atoms interact with CO2 molecules. l- and n-changing cross sections are deduced from the time evolution of the resonant or collision-induced fluorescence following this selective excitation. l-changing cross sections of the order of 104 AṦ are measured; they increase with n as opposed to the plateau observed for Li* colliding with a diatomic molecule. This behavior is qualitatively well explained in the framework of the free-electron model. n-->n' changing processes with large cross sections (10-100 AṦ) are also observed even in the case of large electronic energy change (ΔEnn'>103 cm-1). These results can be interpreted in terms of resonant-electronic to vibrational energy transfers between Li Rydberg states and CO2 vibrational modes.

  15. The generation and accumulation of interstitial atoms and vacancies in alloys with L1{sub 2} superstructure

    Energy Technology Data Exchange (ETDEWEB)

    Pantyukhova, Olga, E-mail: Pantyukhova@list.ru; Starenchenko, Vladimir, E-mail: star@tsuab.ru; Starenchenko, Svetlana, E-mail: sve-starenchenko@yandex.ru; Solov’ev, Artem, E-mail: tsk-san@mail.ru; Solov’eva, Yulia, E-mail: j-sol@yandex.ru [Tomsk State University of Architecture and Building, 2 Solyanaya Sq., Tomsk, 634003 (Russian Federation)

    2016-01-15

    The dependences of the point defect concentration (interstitial atoms and vacancies) on the deformation degree were calculated for the L1{sub 2} alloys with the high and low antiphase boundaries (APB) energy in terms of the mathematical model of the work and thermal strengthening of the alloys with the L1{sub 2} structure; the concentration of the point defects generated and annihilated in the process of deformation was estimated. It was found that the main part of the point defects generating during plastic deformation annihilates, the residual density of the deformation point defects does not exceed 10{sup −5}.

  16. V. S. Lebedev and I. L. Beigman, Physics of Highly Excited Atoms and Ions

    Science.gov (United States)

    Mewe, R.

    1999-07-01

    This book contains a comprehensive description of the basic principles of the theoretical spectroscopy and experimental spectroscopic diagnostics of Rydberg atoms and ions, i.e., atoms in highly excited states with a very large principal quantum number (n≫1). Rydberg atoms are characterized by a number of peculiar physical properties as compared to atoms in the ground or a low excited state. They have a very small ionization potential (∝1/n2), the highly excited electron has a small orbital velocity (∝1/n), the radius (∝n2) is very large, the excited electron has a long orbital period (∝n3), and the radiation lifetime is very long (∝n3-5). At the same time the R. atom is very sensitive to perturbations from external fields in collisions with charged and neutral targets. In recent years, R. atoms have been observed in laboratory and cosmic conditions for n up to ˜1000, which means that the size amounts to about 0.1 mm, ˜106 times that of an atom in the ground state. The scope of this monograph is to familiarize the reader with today's approaches and methods for describing isolated R. atoms and ions, radiative transitions between highly excited states, and photoionization and photorecombination processes. The authors present a number of efficient methods for describing the structure and properties of R. atoms and calculating processes of collisions with neutral and charged particles as well as spectral-line broadening and shift of Rydberg atomic series in gases, cool and hot plasmas in laboratories and in astrophysical sources. Particular attention is paid to a comparison of theoretical results with available experimental data. The book contains 9 chapters. Chapter 1 gives an introduction to the basic properties of R. atoms (ions), Chapter 2 is devoted to an account of general methods describing an isolated Rydberg atom. Chapter 3 is focussed on the recent achievements in calculations of form factors and dipole matrix elements of different types of

  17. L'ultime atome de Démocrite au boson de Higgs et au-delà

    CERN Document Server

    Klein, Etienne

    2016-01-01

    L'enjeu de ce dialogue entre un spécialiste de la pensée antique, Heinz Wismann, et un théoricien de la physique moderne, Etienne Klein, est de retracer la longue histoire de l'idée de l'atome qui n'a cessé de hanter l'imagination des chercheurs. Il ressort de cette reconstruction des étapes successives de l'atomisme que, même si les moyens de vérification changent d'une époque à l'autre, c'est le génie créatif des savants qui, d'hypothèses en hypothèses, fait progresser les découvertes. De Démocrite, qui au Ve siècle avant notre ère pense au vide dynamique, à la théorie moderne de l'atome, ce sont des hypothèses spéculatives qui ont fait bouger les lignes ; pour progresser, la science a besoin de "penser". Avec ces deux complices, il sera démontré de façon vivante et passionnante que la jonction se fait entre la science la plus avancée et la culture, que tout commence toujours par la pensée, la spéculation, c'est-à-dire quelque chose qui n'est pas encore schématisé.

  18. Cohort life tables for a population of the soft-shell clam, Mya arenaria L., in the White Sea

    Science.gov (United States)

    Gerasimova, Alexandra V.; Maximovich, Nikolay V.; Filippova, Nadezhda A.

    2015-06-01

    The Mya arenaria generation in the White Sea was observed for almost the whole life cycle (around 25 years). Using the data on this generation dynamics, the cohort life table was built. The main purpose of the research is analysis of age-specific mortality in this soft-shell clam population. The mortality rate was found to change more than tenfold throughout the study period. No regular changes in its value were observed. Periods of low mortality alternated with periods of much higher mortality. Several reasons for the increase in M. arenaria mortality rate during its life cycle are proposed: (a) living in the surface sediment layer at early stages of life cycle (unstable environment, high mortality of non-viable clams, predator impact); (b) intense intraspecific relationships in dense aggregations of young clams; (c) increased intraspecific competition during periods of the rapid individual growth; (d) ageing (clam mortality increases with older age—achievement of an average and a maximum lifespan).

  19. L- and M-shell x-ray production cross sections of neodymium, gadolinium, holmium, ytterbium, gold, and lead by 25-MeV carbon and 32-MeV oxygen ions

    International Nuclear Information System (INIS)

    L- and M-shell x-ray production cross sections were measured for thin solid targets of neodymium, gadolinium, holmium, ytterbium, gold, and lead by 25-MeV 12C/sup q+/ (q = 4,5,6) and by 32-MeV 16O/sup q+/ (q = 5,7,8). The cross sections were determined from measurements made with thin targets (2). For projectiles with one or two K-shell vacancies, the target x-ray production cross sections were found to be enhanced over those for projectiles without a K-shell vacancy. The sum of direct ionization to the continuum (DI) plus electron capture (EC) to the L, M, N... shells and EC to the K shell of the projectile were extracted from the data. The results are compared to the predictions of first Born theories, i.e., plane-wave Born approximation for DI and Oppenheimer-Brinkman-Kramers formula of Nikolaev for EC and to the ECPSSR approach that accounts for energy loss and Coulomb deflection of the projectile as well as for relativistic and perturbed stationary states of inner-shell electrons

  20. L- and M-shell x-ray production cross sections of Nd, Gd, Ho, Yb, Au, and Pb by 25-MeV carbon and 32-MeV oxygen ions

    International Nuclear Information System (INIS)

    L- and M-shell x-ray production cross sections have been measured for thin solid targets of neodymium, gadolinium, holmium, ytterbium, gold, and lead by 25-MeV /sub //sub 62C/sup q/+ (q = 4,5,6) and by 32-MeV /sub //sub 86O/sup q/+ (q = 5,7,8). The cross sections were determined from measurements made with thin targets (less than 2.25 μg/cm2). For projectiles with one or two K-shell vacancies, the target x-ray production cross sections were found to be enhanced over those for projectiles without a K-shell vacancy. The sum of direct ionization to the continuum (DI) plus electron capture (EC) to the L,M,N,. . . shells and EC to the K shell of the projectile have been extracted from the data. The results are compared to the predictions of first Born theories, i.e., plane-wave Born approximation for DI and Oppenheimer-Brinkman-Kramers formula of Nikolaev for EC, and to the ECPSSR that accounts for energy loss and Coulomb deflection of the projectile as well as for relativistic and perturbed stationary states of inner-shell electrons

  1. Densification behavior of gas and water atomized 316L stainless steel powder during selective laser melting

    International Nuclear Information System (INIS)

    The densification during selective laser melting (SLM) process is an important factor determining the final application of SLM-part. In the present work, the densifications under different processing conditions were investigated and the densification mechanisms were elucidated. It was found that the higher laser power, lower scan speed, narrower hatch spacing and thinner layer thickness could enable a much smoother melting surface and consequently a higher densification. The gas atomized powder possessed better densification than water atomized powder, due to the lower oxygen content and higher packing density of gas atomized powder. A large number of regular-shaped pores can be generated at a wider hatch spacing, even if the scanning track is continuous and wetted very well. The densification mechanisms were addressed and the methods for building dense metal parts were also proposed as follows: inhibiting the balling phenomenon, increasing the overlap ratio of scanning tracks and reducing the micro-cracks.

  2. K-, L- and M-shell X-ray productions induced by argon ions in the 0.8-1.6 MeV/amu range

    Science.gov (United States)

    Gluchshenko, N.; Gorlachev, I.; Ivanov, I.; Kireyev, A.; Kozin, S.; Kurakhmedov, A.; Platov, A.; Zdorovets, M.

    2016-04-01

    The X-ray emissions induced by argon ions for the elements from Mg to Bi were measured on mono-elemental thin films. K-, L- and M-shells X-ray production cross section were obtained for the 40Ar projectile energies of 32, 40, 48, 56 and 64 MeV, considering absorption corrections. For the most of target elements the approach used is based on the calculation of X-ray production cross sections through the cross section of Rutherford backscattering. The efficiency of the X-ray detector was determined using standard calibrated radioactive sources. The experimental results are compared to the predictions of the ECPSSR and PWBA theories calculated with the ISICS code.

  3. L electron populations of hollow ions produced in collisions of energetic Ar ions with metallic targets

    International Nuclear Information System (INIS)

    In this work, we studied hollow ions produced in collisions of Ar ions with metallic targets of atomic numbers 12 ∝ 73, at incident energies 43 ∝ 95 MeV. We observed Kα hypersatellites and satellites of Ar ions and obtained L shell electron populations with vacant and half vacant K shell. The results are very different to those reported for hollow atoms formed in slow collisions. (orig.)

  4. Calculations of electron screening in muonic atoms

    International Nuclear Information System (INIS)

    The electron screening in mounic atoms (O, Al, Fe, In, Ho, Au, Th) has been calculated for p3/2, d5/2 and f7/2 levels with nμ=3/2, d5/2 and f7/2 muons up to nμ=30. Screening corrections are also given for electron configurations with holes in the K and L3 shell. (orig.)

  5. ANALYSIS OF INTERNAL RESONANCE OF COMPOSITE CIRCULAR CYLINDRICAL SHELLS BASED ON THE MULTIDIMENSIONAL L-P METHOD%基于多元L-P法的复合材料圆柱壳内共振分析

    Institute of Scientific and Technical Information of China (English)

    王延庆; 梁力; 郭星辉; 杨坤

    2012-01-01

    A composite circular cylindrical shell made from different materials is investigated. Based on Donnell's shallow shell theory and classical laminated shell theory, nonlinear vibrating equation is derived, in which the effects of dynamic Young's modulus and geometric large-amplitude are considered. Galerkin method is used to disperse the vibrating equation. The nonlinear vibrating responses of the system with the participation of two neighboring axial modes are solved by applying the multidimensional L-P method. And complex frequency-response curves indicating internal resonance are obtained, showing that the energy is transferred between the two modes which affect each other, and there is 1:1 internal resonance phenomenon in the system. Result of multiple scales method is compared with that of multidimensional L-P method, and the same conclusion is drawn.%以不同材料构成的复合材料圆柱壳作为研究模型,考虑几何非线性,动态弹性模量等因素,根据Dormell’s简化壳理论及经典层合壳理论建立其非线性振动方程。采用Galerkin方法对振动方程进行离散化,应用多元L-P法求解了系统包含两个相邻轴向模态的非线性振动响应,得到了反映复杂内共振的幅频特性曲线,表明能量在两个模态之间相互传递,彼此影响牵制,系统存在1:1内共振现象。最后利用多尺度法与多元L-P法所得结果进行比较,得到了相同的结论。

  6. Improved atomic data for electron-transport predictions by the codes TIGER and TIGERP. I. Inner-shell ionization by electron collision

    International Nuclear Information System (INIS)

    The inner-shell ionization data for electron-target collisions now in use in the TIGER and TIGERP electron-transport codes are extracted and compared with other data for these processes. The TIGER cross sections for K-shell ionization by electron collisions are found to be seriously in error for large-Z targets and incident electron energies greater than 1 MeV. A series of TIGER and TIGERP runs were carried out with and without improved K-shell electron ionization cross section data replacing that now in use. The relative importance of electron-impact and photon ionization of the various subshells was also extracted from these runs. In general, photon ionization dominated in the examples studied so the sensitivity of many predicted properties to errors in the electron-impact subshell ionization data was not large. However, some differences were found and, as all possible applications were not covered in this study, it is recommended that these electron-impact data now in TIGER and TIGERP be replaced. Cross section data for the processes under study are reviewed and those that are most suitable for this application are identified. 19 references, 9 figures, 2 tables

  7. Atomic force microscopy of surface relief in individual grains of fatigued 316L austenitic stainless steel

    Czech Academy of Sciences Publication Activity Database

    Man, Jiří; Obrtlík, Karel; Blochwitz, C.; Polák, Jaroslav

    2002-01-01

    Roč. 50, č. 15 (2002), s. 3767-3780. ISSN 1359-6454 R&D Projects: GA ČR GA106/00/D055; GA ČR GA106/01/0376 Institutional research plan: CEZ:AV0Z2041904 Keywords : fatigue * persistent slip band * atomic force microscopy Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 3.104, year: 2002

  8. Penetapan Kadar Kalsium, Kalium, Dan Natrium Dalam Buah Sirsak (Annona Muricata L) Secara Spektrofotometri Serapan Atom

    OpenAIRE

    Luthvia

    2015-01-01

    Soursop is fruits that is quite popular because of it tastes sweet acidity. It contains many important elements that needed by the body, that are carbohydrate, protein, fat, vitamins, and minerals such as calcium, potassium, magnesium, sodium, phosphorus, iron, and zinc. The purpose of this research was to know the level of calcium, potassium, and sodium in soursop. The determination of these metal was done by using atomic absorption spectrophotometry with the wavelength at 422.7 nm for calci...

  9. 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)

    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

  10. Ab initio Bethe-Salpeter calculations of the x-ray absorption spectra of transition metals at the L-shell edges

    Science.gov (United States)

    Vinson, J.; Rehr, J. J.

    2012-11-01

    We present ab initio Bethe-Salpeter equation (BSE) calculations of the L2,3 edges of several insulating and metallic compounds containing Ca, V, Fe, Co, Ni, and Cu, spanning a range of 3d-electron occupations. Our approach includes the key ingredients of a unified treatment of both extended states and atomic multiplet effects, i.e., Bloch states, self-consistent crystal potentials, ground-state magnetism, GW self-energy corrections, spin-orbit terms, and Coulomb interactions between the L2 and L3 levels. The method is implemented in the ocean package, which uses plane-wave pseudopotential wave functions as a basis, a projector-augmented-wave construction for the transition matrix elements, and a resolvent formalism for the BSE calculation. The results are in near quantitative agreement with experiment, including both fine structure at the edges and the nonstatistical L3/L2 ratios observed for these systems. Approximations such as time-dependent density-functional theory are shown to be less accurate.

  11. Broad line emission from iron K- and L-shell transitions in the active galaxy 1H 0707-495.

    Science.gov (United States)

    Fabian, A C; Zoghbi, A; Ross, R R; Uttley, P; Gallo, L C; Brandt, W N; Blustin, A J; Boller, T; Caballero-Garcia, M D; Larsson, J; Miller, J M; Miniutti, G; Ponti, G; Reis, R C; Reynolds, C S; Tanaka, Y; Young, A J

    2009-05-28

    Since the 1995 discovery of the broad iron K-line emission from the Seyfert galaxy MCG-6-30-15 (ref. 1), broad iron K lines have been found in emission from several other Seyfert galaxies, from accreting stellar-mass black holes and even from accreting neutron stars. The iron K line is prominent in the reflection spectrum created by the hard-X-ray continuum irradiating dense accreting matter. Relativistic distortion of the line makes it sensitive to the strong gravity and spin of the black hole. The accompanying iron L-line emission should be detectable when the iron abundance is high. Here we report the presence of both iron K and iron L emission in the spectrum of the narrow-line Seyfert 1 galaxy 1H 0707-495. The bright iron L emission has enabled us to detect a reverberation lag of about 30 s between the direct X-ray continuum and its reflection from matter falling into the black hole. The observed reverberation timescale is comparable to the light-crossing time of the innermost radii around a supermassive black hole. The combination of spectral and timing data on 1H 0707-495 provides strong evidence that we are witnessing emission from matter within a gravitational radius, or a fraction of a light minute, from the event horizon of a rapidly spinning, massive black hole. PMID:19478778

  12. D, L-Sulforaphane Loaded Fe3O4@ Gold Core Shell Nanoparticles: A Potential Sulforaphane Delivery System.

    Science.gov (United States)

    Kheiri Manjili, Hamidreza; Ma'mani, Leila; Tavaddod, Sharareh; Mashhadikhan, Maedeh; Shafiee, Abbas; Naderi-Manesh, Hossein

    2016-01-01

    A novel design of gold-coated iron oxide nanoparticles was fabricated as a potential delivery system to improve the efficiency and stability of d, l-sulforaphane as an anticancer drug. To this purpose, the surface of gold-coated iron oxide nanoparticles was modified for sulforaphane delivery via furnishing its surface with thiolated polyethylene glycol-folic acid and thiolated polyethylene glycol-FITC. The synthesized nanoparticles were characterized by different techniques such as FTIR, energy dispersive X-ray spectroscopy, UV-visible spectroscopy, scanning and transmission electron microscopy. The average diameters of the synthesized nanoparticles before and after sulforaphane loading were obtained ∼ 33 nm and ∼ 38 nm, respectively, when ∼ 2.8 mmol/g of sulforaphane was loaded. The result of cell viability assay which was confirmed by apoptosis assay on the human breast cancer cells (MCF-7 line) as a model of in vitro-cancerous cells, proved that the bare nanoparticles showed little inherent cytotoxicity, whereas the sulforaphane-loaded nanoparticles were cytotoxic. The expression rate of the anti-apoptotic genes (bcl-2 and bcl-xL), and the pro-apoptotic genes (bax and bak) were quantified, and it was found that the expression rate of bcl-2 and bcl-xL genes significantly were decreased when MCF-7 cells were incubated by sulforaphane-loaded nanoparticles. The sulforaphane-loaded into the designed gold-coated iron oxide nanoparticles, acceptably induced apoptosis in MCF-7 cells. PMID:26982588

  13. D, L-Sulforaphane Loaded Fe3O4@ Gold Core Shell Nanoparticles: A Potential Sulforaphane Delivery System

    Science.gov (United States)

    Kheiri Manjili, Hamidreza; Ma’mani, Leila; Tavaddod, Sharareh; Mashhadikhan, Maedeh; Shafiee, Abbas; Naderi-Manesh, Hossein

    2016-01-01

    A novel design of gold-coated iron oxide nanoparticles was fabricated as a potential delivery system to improve the efficiency and stability of d, l-sulforaphane as an anticancer drug. To this purpose, the surface of gold-coated iron oxide nanoparticles was modified for sulforaphane delivery via furnishing its surface with thiolated polyethylene glycol-folic acid and thiolated polyethylene glycol-FITC. The synthesized nanoparticles were characterized by different techniques such as FTIR, energy dispersive X-ray spectroscopy, UV-visible spectroscopy, scanning and transmission electron microscopy. The average diameters of the synthesized nanoparticles before and after sulforaphane loading were obtained ∼ 33 nm and ∼ 38 nm, respectively, when ∼ 2.8 mmol/g of sulforaphane was loaded. The result of cell viability assay which was confirmed by apoptosis assay on the human breast cancer cells (MCF-7 line) as a model of in vitro-cancerous cells, proved that the bare nanoparticles showed little inherent cytotoxicity, whereas the sulforaphane-loaded nanoparticles were cytotoxic. The expression rate of the anti-apoptotic genes (bcl-2 and bcl-xL), and the pro-apoptotic genes (bax and bak) were quantified, and it was found that the expression rate of bcl-2 and bcl-xL genes significantly were decreased when MCF-7 cells were incubated by sulforaphane-loaded nanoparticles. The sulforaphane-loaded into the designed gold-coated iron oxide nanoparticles, acceptably induced apoptosis in MCF-7 cells. PMID:26982588

  14. The study of the action of self-friction field on the atom and molecular structures by using combined Hartree-Fock-Roothaan theory for closed and open shells of any symmetry

    Science.gov (United States)

    Mamedov, B. A.; Çopuroğlu, E.

    2016-06-01

    In this work, we study the effects of self-friction field on the states of a single configuration of closed and open shells by using the Combined Hartree-Fock-Roothaan equations for atomic-molecular and nuclear systems. Here, we present a program that implements the evaluation of the various properties of atoms and molecular systems with respect to the various values of self-friction quantum numbers. An especially fast and accurate algorithm for the calculation of the self-friction multicenter molecular integrals is obtained by using one-range addition theorems. To demonstrate the action of self-friction field on the atomic and molecular systems we have performed the calculations of H2O, CH3, CH2 and NH3 molecules. For the derivations of the orbital, kinetic and total energies and linear combination coefficients, the results are given for various values of self-friction quantum numbers. For various values of self-friction quantum numbers the obtained results of the orbital, kinetic and total energies and linear combination coefficients have been analyzed.

  15. Linear Depenedences of Van Der Waals, Covalent and Valence Shell Radii of Atoms of Groups 1a - 8a on their Bohr Radii

    OpenAIRE

    Heyrovska, Raji

    2007-01-01

    An earlier finding that the van der waals radii are related to their de broglie wavelengths for some non-metallic elements has been extended here to show that in fact, they vary linearly with the ground state bohr radii for all the elements of groups 1a to 8 a. Similarly, the valence shell radii and the covalent radii are shown to be linearly dependent on the bohr radii. One table of data and 5 figures have been provided here showing that all the above radii are sums of two lengths, one of wh...

  16. Atomic ordering and magnetic properties of polycrystalline L10-FePd dot arrays

    International Nuclear Information System (INIS)

    The polycrystalline L10-FePd (0 0 1) films considering a highly ordered dot array with various sizes have been successfully prepared by using a microfabrication process. The lateral size of square dots was changed in between 1 and 10 μm. The coercivity (Hc) of patterned L10-ordered FePd films was found to be slightly reduced compared to that of continuous film. Furthermore, Hc was slightly decreased after annealing at 500 deg. C. In the pinning mechanism, Hc can be determined by strong pinning sites for domain walls, which are the grain boundary regions in L10-ordered polycrystalline FePd films. These results indicate that the dot size dependence of Hc before and after annealing may be related to the pinning mechanism. The long-range ordering parameter (S) was increased after annealing. This demonstrates that post-annealing accelerates L10-FePd ordering, but there is no clear correlation between S and Hc.

  17. Shell supports

    DEFF Research Database (Denmark)

    Almegaard, Henrik

    2004-01-01

    A new statical and conceptual model for membrane shell structures - the stringer system - has been found. The principle was first published at the IASS conference in Copenhagen (OHL91), and later the theory has been further developed (ALMO3)(ALMO4). From the analysis of the stringer model it can be...... concluded that all membrane shells can be described by a limited number of basic configurations of which quite a few have free edges....

  18. Effect of five year storage on total phenolic content and antioxidant capacity of almond (Amygdalus communisL. hull and shell from different genotypes

    Directory of Open Access Journals (Sweden)

    Khadijeh Sadat Moosavi Dolatabadi

    2014-12-01

    Full Text Available Objectives: Almond (Prunus amygdalus hull and shell are agricultural by-products that are a source of phenolic compounds.The processing of almond produce shell and hull, accounts for more than 50% by dry weight of the almond fruits. Recently, more studies have focused on the influence of storage conditions and postharvest handling on the nutritional quality of fruits, especially the antioxidant phenolics. In this study, influence of long-term storage (five years on the total phenolic and antioxidant capacity of almond hull and shell from different genotypes was evaluated. Materials and Methods: The fruits of subjected genotypes were collected and their hull and shell were separated. They were dried and reduced to fine powder. This powder stored at room temperature for five years. The total phenolic content (TPC and bioactivities (antioxidant potential: DPPH and ABTS radical scavenging and reducing power of extracts were evaluated using spectrophotometric methods. Results: It was found that TPC content and bioactivity levels in the stored almond hull and shell were different, compared to the hulls and shells which were evaluated in 2007. S1-4 genotype had the highest TPC and reducing power in its hull and shell.Low correlation coefficient was observed between phenolic content and the DPPH radical scavenging percentage in hull and shell extract. Conclusions: For the first time, results of this investigation showed that storage can influence the antioxidant and antiradical potential of almond hull and shell.

  19. Particle size dependence of atomic ordering and magnetic properties of L10-FePd nanoparticles

    International Nuclear Information System (INIS)

    L10-type FePd nanoparticles with mean sizes between 4 and 15 nm in diameter have been fabricated by electron beam evaporation. Coercivity and remanence of FePd nanoparticles with sizes less than about 8 nm were quite low compared to the values for 10-nm-sized FePd nanoparticles. Both coercivity and remanence increased with decreasing the temperature, indicating the large suppression of the thermal agitation of the magnetic moment at lower temperatures. Superparamagnetic behavior appeared in zero-field-cooled (ZFC) and field-cooled (FC) temperature dependence of magnetization for about 6-nm-sized FePd nanoparticles. Disappearance of the hard magnetic properties in smaller sized FePd nanoparticles is attributed to the reduction of the long-range order (LRO) parameter of the L10-structure as well as the thermal agitation of magnetic moment

  20. IFPM theory and coupled-channels calculations of K/sup n/L/sup v/ multiple vacancy distributions in ion-atom collisions

    International Nuclear Information System (INIS)

    Multiple L-shell vacancy production in the target can be very copious when the impact parameter, B, is near or within the L-shell radius. Small B values can be selected either by detecting K-shell vacancies (x-ray or Auger satellites (K1) or hypersatellites (K2)) or by detecting the projectile at a relatively large scattering angle. There are plentiful data for L-vacancy distributions of satellites, but very few for K0 or K2. Until our recent work, the satellite data had been interpreted mainly in terms of a binomial distribution (or product of them) at each B, a model in which the emissions of electrons are statistically independent. For the related problem of electron transfer in coincidence with a K vacancy we have found that, even in the independent Fermi particle model (IFPM), correlation effects from interference of amplitudes grow with the projectile charge, Z/sub p/, and become quite significant for Z/sub p/ greater than or equal to 3. Consequently, we formulated the IFPM theory of multiple vacancy production to investigate the degree of breakdown of statistical independence

  1. Shelled opisthobranchs.

    Science.gov (United States)

    Mikkelsen, Paula M

    2002-01-01

    In his contributions to the monographic series "Manual of Conchology", Henry Pilsbry reviewed the subgroup Tectibranchiata, comprising those opisthobranch snails that (at least primitively) still possess a shell (Pilsbry, 1894-1896). Exemplified by the Cephalaspidea (bubble shells), others included in this group at Pilsbry's time and since were Anaspidea (sea hares) and the shelled members of Notaspidea (side-gilled slugs) and Sacoglossa (leaf slugs). Pilsbry (and others since his time) considered tectibranchs to be the "root stock" from which more advanced gastropods such as Nudibranchia and Pulmonata were derived. Tectibranch systematics is firmly based on conchology and most species were originally described from empty shells. However, soft-anatomical characters were acknowledged quite early on as equally important in tectibranchs, due to the reduction of their shells and their evolutionary proximity to unshelled gastropods. Today, Tectibranchiata is not recognized as a natural taxon although the word "tectibranch" (like "prosobranch" and "mesogastropod") continues in vernacular use. Shelled opisthobranchs have been redistributed among various taxa, including several new ones--the unresolved basal opisthobranchs (Architectibranchia) and the "lower Heterobranchia", an enigmatic and currently much-studied group of families considered basal to all of Euthyneura (Opisthobranchia and landsnails (Pulmonata)). Despite their polyphyletic status, shelled opisthobranchs remain important subjects in evolutionary studies of gastropods--as the most basal members of nearly every opisthobranch clade and as organisms with mosaic combinations of primitive and derived features within evolutionary "trends" (e.g., loss of the shell, detorsion, concentration of the nervous system, ecological specialization, etc.). Although they play a pivotal role, the shelled opisthobranchs have received minimal attention in more comprehensive gastropod studies, often relegated to token

  2. Artificial neural network (ANN) approach for modeling of Pb(II) adsorption from aqueous solution by Antep pistachio (Pistacia Vera L.) shells.

    Science.gov (United States)

    Yetilmezsoy, Kaan; Demirel, Sevgi

    2008-05-30

    A three-layer artificial neural network (ANN) model was developed to predict the efficiency of Pb(II) ions removal from aqueous solution by Antep pistachio (Pistacia Vera L.) shells based on 66 experimental sets obtained in a laboratory batch study. The effect of operational parameters such as adsorbent dosage, initial concentration of Pb(II) ions, initial pH, operating temperature, and contact time were studied to optimise the conditions for maximum removal of Pb(II) ions. On the basis of batch test results, optimal operating conditions were determined to be an initial pH of 5.5, an adsorbent dosage of 1.0 g, an initial Pb(II) concentration of 30 ppm, and a temperature of 30 degrees C. Experimental results showed that a contact time of 45 min was generally sufficient to achieve equilibrium. After backpropagation (BP) training combined with principal component analysis (PCA), the ANN model was able to predict adsorption efficiency with a tangent sigmoid transfer function (tansig) at hidden layer with 11 neurons and a linear transfer function (purelin) at output layer. The Levenberg-Marquardt algorithm (LMA) was found as the best of 11 BP algorithms with a minimum mean squared error (MSE) of 0.000227875. The linear regression between the network outputs and the corresponding targets were proven to be satisfactory with a correlation coefficient of about 0.936 for five model variables used in this study. PMID:17980484

  3. Linear Depnedences of Van Der Waals, Covalent and Valence Shell Radii of Atoms of Groups 1a - 8a on their Bohr Radii

    CERN Document Server

    Heyrovska, Raji

    2007-01-01

    An earlier finding that the van der waals radii are related to their de broglie wavelengths for some non-metallic elements has been extended here to show that in fact, they vary linearly with the ground state bohr radii for all the elements of groups 1a to 8 a. Similarly, the valence shell radii and the covalent radii are shown to be linearly dependent on the bohr radii. One table of data and 5 figures have been provided here showing that all the above radii are sums of two lengths, one of which is a multiple of the bohr radius and the other, a positive or negative constant for each group of elements.

  4. The red atom. The help of german scientists to USSR between 1945-1961; L'atome rouge. L'aide a l'Urss des savants allemands entre 1945-1961

    Energy Technology Data Exchange (ETDEWEB)

    Andurand, R

    2009-03-15

    In this issue is tackled the cooperation between German and Russian scientists in nuclear energy from 1945 to 1961 and especially about the uranium enrichment by gaseous diffusion of uranium hexafluoride in cascade. The problems they encountered and their solutions are related until the explosion of the first Russian atomic bomb even if it was not a bomb with enriched uranium but with plutonium got in a nuclear reactor. (N.C.)

  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. The role of atomic hydrogen and hydrogen-induced martensites in hydrogen embrittlement of type 304L stainless steel

    Institute of Scientific and Technical Information of China (English)

    潘川; 褚武扬; 李正邦; 梁东图; 宿彦京; 乔利杰

    2002-01-01

    The role of atomic hydrogen and hydrogen-induced martensites in hydrogen embrittlement in slow strain rate tensile tests and hydrogen-induced delayed cracking (HIC) in sustained load tests for type 304 L stainless steel was quantitatively studied.The results indicated that hydrogen-induced martensites formed when hydrogen concentration C0 exceeded 30 ppm,and increased with an increase in C0,i.e.M(vol%)=62-82.5exp(-C0/102).The relative plasticity loss caused by the martensites increased linearly with increasing amount of the martensites,i.e.Iδ(M),%=0.45M(vol %)=27.9-37.1 exp(-C0/102).The plasticity loss caused by atomic hydrogen Iδ(H) increased with an increase in C0 and reached a saturation value Iδ(H)max=40% when C0>100 ppm.Iδ(H) decreased with an increase in strain rate ,i.e.Iδ(H),%=-21.9-9.9,and was zero when ≥c=0.032/s.HIC under sustained load was due to atomic hydrogen,and the threshold stress intensity for HIC decreased linearly with lnC0,i.e.KIH(Mpam1/2)=91.7-10.1 lnC0(ppm).The fracture surface of HIC was dimple if KI was high or/and C0 was low,otherwise it was quasi-cleavage.The boundary line between ductile and brittle fracture surface was KI-54+25exp(-C0/153)=0.``

  7. Particles and Shells

    CERN Document Server

    Palazzi, P

    2003-01-01

    The current understanding of particle masses in terms of quarks and their binding energy is not satisfactory. Both in atoms and in nuclei the organizing principle of stability is the shell structure, while this does not seem to play any role for particles. In order to explore the possibility that shells might also be relevant at this inner level of aggregation, atomic and nuclear stability are expressed by "stablines", alignments of the 1/3 power of the total number of constituents of the most stable configurations. Could similar patterns be found in the particle spectrum? By analyzing the distribution of particle lifetimes as a function of mass, stability peaks are recognized for mesons and for baryons and indeed the cube roots of their masses follow two distinct stablines. Such alignments would be a strong indication that the particles themselves are shell structured assuming only that each constituent contributes a constant amount to the total mass. This is incompatible with the prevalent view that the par...

  8. Atomic Bremsstrahlung in ion-atom collisions (stripping)

    International Nuclear Information System (INIS)

    Atomic Bremsstrahlung produced in high energy (non relativistic) ion-atom collisions including retardation effects is studied. Mechanical states of the system are described by the symmetrical eikonal approximation and Hartree-Fock electronic wave functions for the calculation of the shape factor of each atom. Photon energy spectra are presented for collisions of protons against noble gases, Ne, Ar, Kr and Xe. The contribution of each atomic shell to these spectra is studied, where lowest shell (1s) corresponds to the hard X-ray region and the higher shells correspond to lower photon energies. (Author)

  9. Knowledge Led Master Code Search for Atomic and Electronic Structures of LaF3 Nanoclusters on Hybrid Rigid Ion-Shell Model-DFT Landscapes

    OpenAIRE

    Woodley, S. M.

    2013-01-01

    Stable and metastable atomic configurations of stoichiometric (LaF3)n nanoclusters are obtained for n = 1 to 6 using Monte Carlo global optimization techniques implemented in newly developed software. All configurations are refined using an all-electron DFT approach with the PBEsol exchange and correlation functional. To reduce the computational cost, approximate configurations were initially filtered out using a basin hopping algorithm that was biased toward finding either the global minimum...

  10. Generation of iodine L-shell X-rays under excitation of large CF{sub 3}I clusters by femtosecond laser radiation

    Energy Technology Data Exchange (ETDEWEB)

    Gordienko, Vyacheslav M; Dzhidzhoev, M S; Zhvaniya, I A; Pribytkov, Andrei V; Trubnikov, Dmitrii N; Fedorov, D O

    2012-11-30

    The use of clusters of polyatomic molecules with a relatively low ionisation energy ({approx}10 eV) is proposed for the efficient production of X-ray radiation. We have observed for the first time the generation of characteristic X-ray radiation due to L transitions in iodine atoms under the high-intensity femtosecond laser irradiation of molecular CF{sub 3}I clusters, which were a small admixture to Ar carrier gas. The X-ray conversion efficiency amounts to {approx}10{sup -6} (for a yield of {approx}10{sup 7} photons per pulse), which is an order of magnitude higher than the efficiency we obtained in the case of argon clusters under comparable conditions. (letters)

  11. Atomic data from the Iron project L2. electron excitation of Ni+24

    International Nuclear Information System (INIS)

    This paper reports on the calculation of collision strengths for electron induced transitions in the beryllium-like ion Ni XXV whose ground state is 1s22s21S0. We make use of the R-matrix method in conjunction with the intermediate frame coupling transformation (IFCT). The target has 98 fine structure states 1s2nln'l'SLJ corresponding to n = 2 and n' = 2, 3, 4. Our calculation extends up to 440 Ry with respect to the ground state. In order to obtain reliable rate coefficients at high temperatures (T above 2*107 K) we have extended our collision strengths to much higher energies by using a variety of techniques, including use of Burgess's interactive code OmeUps. The effective collision strength is tabulated against log T for the 45 transitions linking the lowest 10 levels. We also give results for 5 transitions in the X-ray region which are needed in solar studies. The temperature range 6.3 ≤ log T ≤ 8.3 is centred on log T = 7.1 which is where this ion has its maximum coronal abundance. (authors)

  12. Influence of binder system and temperature on rheological properties of water atomized 316L powder injection moulding feedstocks

    Directory of Open Access Journals (Sweden)

    Uğur GÖKMEN

    2016-02-01

    Full Text Available In order to obtain a proper powder injection molding the rheological behavior of feedstocks should be known. To determine the binder effect on the rheological behavior of 316L stainless steel powders feedstock two different feedstock were prepared. In the current experiments water atomized 316L stainless steel powders (-20 µm were used. Two types of binders, one of which is mainly paraffin wax can be dissolved in heptane and the other Polietilenglikol (PEG based and can be dissolved in water, were used. Polypropylene was used as binder and steric acid was used as lubricant for both binder systems as skeleton binder. Dry binder system were mixed for 30 min in a three dimensional Turbola. Capillary rheometer was used to characterize the rheological properties of feed stocks at 150-200 °C and a pressures of 0.165-2.069 MPa. Powder loading capacity of PEG and PW based feed stocks were found to be %55 and %61 respectively. The lowest viscosity of PEG and PW based feed stocks were found to be 304.707 Pa.s and 48.857 Pa.s respectively.Keywords: PIM, Binder, Rheological properties

  13. Cross Sections for Inner-Shell Ionization by Electron Impact

    International Nuclear Information System (INIS)

    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

  14. Atomic structures of symmetrical and asymmetrical facets in a near {sigma} = 9{l_brace}2 2 1{r_brace} tilt grain boundary in copper

    Energy Technology Data Exchange (ETDEWEB)

    Hardouin Duparc, Olivier [LSI, CEA-X-CNRS, UMR 7642, Ecole Polytechnique, 91128 Palaiseau Cedex (France)]. E-mail: olivier.hardouinduparc@polytechnique.edu; Couzinie, Jean-Philippe [CECM, CNRS, UPR 2801, 15 rue Georges Urbain, 94407 Vitry Sur Seine (France); Thibault-Penisson, Jany [TECSEN, CNRS, UMR 6122, Universite Paul Cezanne Aix-Marseille III, 13397 Marseille Cedex (France); Lartigue-Korinek, Sylvie [CECM, CNRS, UPR 2801, 15 rue Georges Urbain, 94407 Vitry Sur Seine (France); Decamps, Brigitte [LCMTR, CNRS, UPR 209, 2-8 rue Henri Dunant, 94320 Thiais (France); Priester, Louisette [CECM, CNRS, UPR 2801, 15 rue Georges Urbain, 94407 Vitry Sur Seine (France)

    2007-03-15

    Atomic structures in a {sigma} = 9{l_brace}2 2 1{r_brace} tilt grain boundary (GB) grown by Bridgman solidification of a tricrystal are determined through high-resolution transmission electron microscopy and numerical simulation. Atomic models are simulated via molecular dynamics annealing using an n-body potential fitted on copper properties including its stacking fault energy. Symmetrical and asymmetrical facets are thus identified. Mainly asymmetrical facets are observed, namely {sigma} = 9{l_brace}11, 11, 1{r_brace}||{l_brace}1 1 1{r_brace} and also small parts of incommensurate {l_brace}1 1 0{r_brace}||{l_brace}1 1 1{r_brace}. The symmetrical facets are described by a quasi-mirror plane atomic structure. A specific GB structural unit is recognized as a Lomer unit. Its GB Burgers vector depends on the GB structure itself. Further analyses of these models and of accommodating dislocations are successfully carried out at the atomic level within the framework of the continuous structural unit approach.

  15. L-shell X-ray production cross sections induced by protons and alpha-particles in the 0.7–2.0 MeV/amu range for Ru and Ag

    Energy Technology Data Exchange (ETDEWEB)

    Bertol, A.P.L., E-mail: anapaula.bertol@gmail.com [Instituto de Física, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS (Brazil); Trincavelli, J. [Facultad de Matemática, Astronomía y Física, Universidad Nacional de Córdoba (Argentina); Instituto Enrique Gaviola, CONICET (Argentina); Hinrichs, R. [Instituto de Geociências, UFRGS, Porto Alegre, RS (Brazil); Vasconcellos, M.A.Z. [Instituto de Física, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS (Brazil)

    2014-01-01

    The X-ray emissions induced by protons and alpha-particles of the elements Ag and Ru were measured on mono-elemental thin films. L-shell X-ray production cross sections were obtained for the three L-subshells, considering absorption corrections. The Ag X-ray production cross sections agree with experimental data of other authors and with theoretical models, and were used to endorse the quality of the experimental values for Ru, that were not found in the literature.

  16. L-shell X-ray production cross sections induced by protons and alpha-particles in the 0.7-2.0 MeV/amu range for Ru and Ag

    Science.gov (United States)

    Bertol, A. P. L.; Trincavelli, J.; Hinrichs, R.; Vasconcellos, M. A. Z.

    2014-01-01

    The X-ray emissions induced by protons and alpha-particles of the elements Ag and Ru were measured on mono-elemental thin films. L-shell X-ray production cross sections were obtained for the three L-subshells, considering absorption corrections. The Ag X-ray production cross sections agree with experimental data of other authors and with theoretical models, and were used to endorse the quality of the experimental values for Ru, that were not found in the literature.

  17. Use of the Bethe equation for inner-shell ionization by electron impact

    Science.gov (United States)

    Powell, Cedric J.; Llovet, Xavier; Salvat, Francesc

    2016-05-01

    We analyzed calculated cross sections for K-, L-, and M-shell ionization by electron impact to determine the energy ranges over which these cross sections are consistent with the Bethe equation for inner-shell ionization. Our analysis was performed with K-shell ionization cross sections for 26 elements, with L-shell ionization cross sections for seven elements, L3-subshell ionization cross sections for Xe, and M-shell ionization cross sections for three elements. The validity (or otherwise) of the Bethe equation could be checked with Fano plots based on a linearized form of the Bethe equation. Our Fano plots, which display theoretical cross sections and available measured cross sections, reveal two linear regions as predicted by de Heer and Inokuti [in Electron Impact Ionization, edited by T. D. Märk and G. H. Dunn, (Springer-Verlag, Vienna, 1985), Chap. 7, pp. 232-276]. For each region, we made linear fits and determined values of the two element-specific Bethe parameters. We found systematic variations of these parameters with atomic number for both the low- and the high-energy linear regions of the Fano plots. We also determined the energy ranges over which the Bethe equation can be used.

  18. Geometrical Characteristics and Atomic Charge Variations of Pd(II) Complexes [Pd(L)Cl{sub 2}] with an Axial (Pd...O) Interaction

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jong Keun [Pusan National University, Busan (Korea, Republic of); Cho, Yong Guk; Lee, Shim Sung; Kim, Bong Gon [Gyeongsang National University, Jinju (Korea, Republic of)

    2004-01-15

    Geometrical structures of [Pd(L)Cl{sub 2}] with oxathia macrocycles have been calculated using ab initio second order Moller-Plesset (MP2) and Density Functional Theory (DFT) methods with triple zeta plus polarization (TZP) basis set level. In optimized Pd(L)Cl{sub 2} complexes, Pd(II) locates at the center surrounded by a square planar array of two sulfurs on an oxathia macrocycle and two chlorides. The endo-Pd(II) complexes with an axial (Pd...O) interaction are more stable than the exo-Pd(II) complexes without the interaction. In the endo- Pd(II) complexes, the atomic charge of the oxygen atom moves to Pd(II) via the axial (Pd...O) interaction and then, the charge transfer from Pd(II) to the S-atoms occurs stepwise via {pi}-acceptors of the empty d-orbitals

  19. Shell worlds

    Science.gov (United States)

    Roy, Kenneth I.; Kennedy, Robert G., III; Fields, David E.

    2013-02-01

    The traditional concept of terraforming assumes ready availability of candidate planets with acceptable qualities: orbiting a star in its "Goldilocks zone", liquid water, enough mass, years longer than days, magnetic field, etc. But even stipulating affordable interstellar travel, we still might never find a good candidate elsewhere. Whatever we found likely would require centuries of heavy terraforming, just as Mars or Venus would here. Our increasing appreciation of the ubiquity of life suggests that any terra nova would already possess it. We would then face the dilemma of introducing alien life forms (us, our microbes) into another living world. Instead, we propose a novel method to create habitable environments for humanity by enclosing airless, sterile, otherwise useless planets, moons, and even large asteroids within engineered shells, which avoids the conundrum. These shells are subject to two opposing internal stresses: compression due to the primary's gravity, and tension from atmospheric pressure contained inside. By careful design, these two cancel each other resulting in zero net shell stress. Beneath the shell an Earth-like environment could be created similar in almost all respects to that of Home, except for gravity, regardless of the distance to the sun or other star. Englobing a small planet, moon, or even a dwarf planet like Ceres, would require astronomical amounts of material (quadrillions of tons) and energy, plus a great deal of time. It would be a quantum leap in difficulty over building Dyson Dots or industrializing our solar system, perhaps comparable to a mission across interstellar space with a living crew within their lifetime. But when accomplished, these constructs would be complete (albeit small) worlds, not merely large habitats. They could be stable across historic timescales, possibly geologic. Each would contain a full, self-sustaining ecology, which might evolve in curious directions over time. This has interesting implications

  20. Inner-shell ionization by relativistic radiation pressure

    International Nuclear Information System (INIS)

    Absolute inner-shell ionization cross sections have been measured in the energy range 15 0 <= 65 [MeV] for elements with atomic numbers between 18 and 92 to study the interaction of relativistic electrons with bound electrons. Up to now no measurements were available in that energy range. In experiments concerning K-shells the measurement accuracy was about 4%. The deviations between the experimental data and the theoretical cross sections calculated on the basis of a relativistic quantum mechanical inonization theory are less then 10%. All measured data are covered within a variational width of 8% by a scaling law derived from a simple model. Using the measured X-ray spectra intensity ratios of characteristic L-lines could be determined. The method of X-ray fluorescence analysis with high energetic electrons in the MeV range has been used for the first time to analyze trace amounts of elements. (KBE)

  1. 银杏壳中类黄酮的提取工艺研究%Extraction Technology of Flavonoids from Ginkgo biloba L Shells

    Institute of Scientific and Technical Information of China (English)

    梁晓锋

    2012-01-01

    [Objective] To study the extraction technology of flavonoids from Ginkgo biloba L. shells. [Method] With ethanol solution as the extraction solvent, flavonoids were extracted from G. biloba shells. Effects of ethanol concentration, solid-liquid ratio, extraction time and extraction temperature on the extraction rate of flavonoids were studied by single factor test. The optimal conditions of traditional ethanol extraction and microwave-assisted extraction were researched by orthogonal test. [ Result] The optimal condition of traditional ethanol extraction was .as follows; 60 t extraction temperature, 75% elhanol concentration, 1*45 solid-liquid ratio (W/V,g/ml), and 2 h extraction time. Under this condition, the extraction rate of flavonoids reached 0.503 4%. The optimal condition of microwave-assisted extraction was as follows: 60 V. extraction temperature, 45% ethanol concentration, 1:30 solid-liquid ratio, and 480 s extraction time. Under this condition, the extraction rate of flavonoids reached 0. 815%. [Conclusion] Microwave-assisted extraction was rapid, simple and high-efficient. As a new extraction technology, microwave-assisted extraction was superior to traditional ethano) extraction in certain extent.%[目的]研究银杏壳中类黄酮的提取工艺条件.[方法]采用乙醇水溶液作提取溶剂来提取银杏壳中的类黄酮,通过单因素试验考察提取时间、乙醇浓度、料液比和提取温度等主要因素对银杏类黄酮提取的影响,并采用正交试验确定传统醇提取法和微波协同萃取法提取银杏壳中类黄酮的最佳工艺条件.[结果]传统醇提取法的最佳条件为:提取温度为60℃,乙醇浓度为75%,料液比为1∶45(W/V,g/ml,下同),提取时间为2 h;在此条件下,类黄酮的得率为0.503 4%.微波法提取银杏壳中类黄酮的最佳条件为:微波温度为60℃,乙醇浓度45%,料液比1∶30,微波提取时间480 s;在此条件下,类黄酮得率为0.815%.[结论]微

  2. Atomic density functions: atomic physics calculations analyzed with methods from quantum chemistry

    CERN Document Server

    Borgoo, Alex; Geerlings, P

    2011-01-01

    This contribution reviews a selection of findings on atomic density functions and discusses ways for reading chemical information from them. First an expression for the density function for atoms in the multi-configuration Hartree--Fock scheme is established. The spherical harmonic content of the density function and ways to restore the spherical symmetry in a general open-shell case are treated. The evaluation of the density function is illustrated in a few examples. In the second part of the paper, atomic density functions are analyzed using quantum similarity measures. The comparison of atomic density functions is shown to be useful to obtain physical and chemical information. Finally, concepts from information theory are introduced and adopted for the comparison of density functions. In particular, based on the Kullback--Leibler form, a functional is constructed that reveals the periodicity in Mendeleev's table. Finally a quantum similarity measure is constructed, based on the integrand of the Kullback--L...

  3. Nanoscale characterization of effect of L-arginine on Streptococcus mutans biofilm adhesion by atomic force microscopy.

    Science.gov (United States)

    Sharma, Shivani; Lavender, Stacey; Woo, JungReem; Guo, Lihong; Shi, Wenyuan; Kilpatrick-Liverman, LaTonya; Gimzewski, James K

    2014-07-01

    A major aetiological factor of dental caries is the pathology of the dental plaque biofilms. The amino acid L-arginine (Arg) is found naturally in saliva as a free molecule or as a part of salivary peptides and proteins. Plaque bacteria metabolize Arg to produce alkali and neutralize glycolytic acids, promoting a less cariogenous oral microbiome. Here, we explored an alternative and complementary mechanism of action of Arg using atomic force microscopy. The nanomechanical properties of Streptococcus mutans biofilm extracellular matrix were characterized under physiological buffer conditions. We report the effect of Arg on the adhesive behaviour and structural properties of extracellular polysaccharides in S. mutans biofilms. High-resolution imaging of biofilm surfaces can reveal additional structural information on bacterial cells embedded within the surrounding extracellular matrix. A dense extracellular matrix was observed in biofilms without Arg compared to those grown in the presence of Arg. S. mutans biofilms grown in the presence of Arg could influence the production and/or composition of extracellular membrane glucans and thereby affect their adhesion properties. Our results suggest that the presence of Arg in the oral cavity could influence the adhesion properties of S. mutans to the tooth surface. PMID:24763427

  4. High efficiency n-Si/ p-Cu2O core-shell nanowires photodiode prepared by atomic layer deposition of Cu2O on well-ordered Si nanowires array

    Science.gov (United States)

    Kim, Hangil; Kim, Soo-Hyun; Ko, Kyung Yong; Kim, Hyungjun; Kim, Jaehoon; Oh, Jihun; Lee, Han-Bo-Ram

    2016-05-01

    A highly efficient n-Si/ p-Cu2O core-shell (C-S) nanowire (NW) photodiode was fabricated using Cu2O grown by atomic layer deposition (ALD) on a well-ordered Si NW array. Ordered Si nanowires arrays were fabricated by nano-sphere lithography to pattern metal catalysts for the metal-assisted etching of silicon, resulting in a Si NW arrays with a good arrangement, smooth surface and small diameter distribution. The ALD-Cu2O thin films were grown using a new non-fluorinated Cu precursor, bis(1-dimethylamino-2-methyl-2-butoxy)copper (C14H32N2O2Cu), and water vapor (H2O) at 140°C. Transmission electron microscopy equipped with an energy dispersive spectrometer confirmed that p-Cu2O thin films had been coated over arrayed Si NWs with a diameter of 150 nm (aspect ratio of ˜7.6). The C-S NW photodiode exhibited more sensitive photodetection performance under ultraviolet illumination as well as an enhanced photocurrent density in the forward biasing region than the planar structure diode. The superior performance of C-S NWs photodiode was explained by the lower reflectance of light and the effective carrier separation and collection originating from the C-S NWs structure. [Figure not available: see fulltext.

  5. Atom interferometry with lithium atoms: theoretical analysis and design of an interferometer, applications; Interferometrie atomique avec l'atome de lithium: analyse theorique et construction d'un interferometre, applications

    Energy Technology Data Exchange (ETDEWEB)

    Champenois, C

    1999-12-01

    This thesis is devoted to studies which prepared the construction of an atom Mach-Zehnder interferometer. In such an interferometer, the propagating waves are spatially separated, and the internal state of the atom is not modified. The beam-splitters are diffraction gratings, consisting of standing optical waves near-resonant with an atomic transition. We use the Bloch functions to define the atom wave inside the standing wave grating and thus explain the diffraction process in different cases. We developed a nearly all-analytical model for the propagation of an atom wave inside a Mach-Zehnder interferometer. The contrast of the signal is studied for many cases: phase or amplitude gratings, effects of extra paths, effects of the main mismatches, monochromatic or lightly polychromatic sources. Finally, we discuss three interferometric measurements we think very interesting. The first, the index of refraction of gas for atomic waves, is studied in detail, with numerical simulations. The other measures we propose deal with the electrical properties of lithium. We discuss the ultimate limit for the measure of the static electric polarizability of lithium by atomic interferometry. Then, we discuss how one could measure the possible charge of the lithium atom. We conclude that an optically cooled and collimated atom beam would improve precision. (author)

  6. 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...

  7. Multiple-cascade model for the filling of hollow Ne atoms moving below an Al surface

    International Nuclear Information System (INIS)

    Analytic expressions for a multiple-cascade model were derived to study the filling of L and K vacancies of hollow Ne atoms moving in shallow layers of an Al surface. The model requires cross sections for charge transfer into the L shell of the projectile that were determined from molecular-orbital calculations including screening effects of hollow atoms and asymptotic solid-state energies. The analysis accounts for mechanisms of Landau-Zener curve crossing and Fano-Lichten promotion. To describe the transport of the electrons within the solid, absorption and buildup effects were taken into account. The results from the cascade model show good agreement with angular distributions of Ne K Auger electrons recently measured. Attenuation effects were found to produce shifts in the K Auger spectra at varying observation angles. The significant difference previously observed for the mean L-shell occupation numbers during L and K Auger emission is explained by the present model

  8. Expériences d interférométrie atomique avec l'atome de lithium

    OpenAIRE

    Jacquey, Marion

    2006-01-01

    This study presents the tuning of a Mach Zehnder atom interferometer and its operation for interferometric measurements. A supersonic beam of lithium is coherently manipulated by elastic Bragg diffraction on laser standing waves almost resonant with the first resonance transition of lithium atom at 671 nm. A model of the interferometer, based on simulations of the diffraction process, is used to precisely describe the selectivity with respect to atom velocity and incidence angle. The apparatu...

  9. Origines et limites du modèle de l'atome artificiel pour une boîte quantique de semiconducteurs

    OpenAIRE

    Cassabois, Guillaume

    2006-01-01

    Le modèle de l'atome artificiel est l'image physique intuitive qui découle de la discrétisation du spectre énergétique des électrons, qui sont confinés dans les trois directions de l'espace dans une boîte quantique de semiconducteurs. Cette analogie avec les systèmes atomiques s'est révélée commode et fructueusepour étudier les propriétés électroniques et optiques des boîtes quantiques de semiconducteurs. Elle a conduit à des expériences élégantes qui utilisent les concepts de base de la phys...

  10. Cascade of negative muons in atoms

    International Nuclear Information System (INIS)

    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

  11. ZnSe/ZnS/L-Cys核壳结构量子点光声与表面光伏特性∗%Photoacoustic and surface photovoltaic characteristics of L-Cysteine-capp ed ZnSe quantum dots with a core-shell structure

    Institute of Scientific and Technical Information of China (English)

    林莹莹; 李葵英; 单青松; 尹华; 朱瑞苹

    2016-01-01

    ZnSe量子点光电子特性的研究对于其微观电子结构探测和应用领域的扩展具有重要的意义。本文结合表面光伏与光声技术以及激光Raman研究了不同回流温度下制备L-半胱氨酸(L-Cys)为配体核壳结构ZnSe量子点的微结构和光声与表面光伏特性。结果发现,具有n-型光伏特性的ZnSe 量子点在近紫外到可见光范围内展示出优良的表面光伏性质。尤其在波长为350—550 nm范围内光子能量绝大部分用于产生表面光伏效应,而不是用于无辐射跃迁导致的晶格热振动,同时证实了光声与表面光伏效应之间的能量互补关系。实验指认ZnSe量子点在300—350 nm短波区域出现的光声信号和在1120,1340和1455 cm−1高频区域出现的Raman峰与配体L-Cys的多声子振动模式密切相关。实验结果表明,随着回流温度的降低, ZnSe量子点的平均粒径有减小趋势,这在改善样品的表面效应和小尺寸效应的同时,有利于提高核壳结构ZnSe量子点的光伏转换效率。%The study on photoelectronic characteristics of ZnSe quantum dots (QDs) is of significance for investigating its microelectronic structure and expanding its potential applications because ZnSe QDs has low biologic toxicity. In the present paper, the surface photovoltaic and photoacoustic technologies, and laser Raman, X-ray diffraction, transmission electron microscopy and Foureier transform infrared spectroscopy spectrum are jointly used to probe the microstructures, the photoacoustic and surface photovoltaic characteristics of L-Cysteine-capped ZnSe QDs prepared by water-phase synthesis at different reflux temperatures. The results indicate that the ZnSe QDs with a mean grain size of about 3 nm has a core-shell ZnSe/ZnS/L-Cys structure, in which the sulfhydryl groups in ligand prefer reacting with Zn atom at the (220) face to form the ZnS shell layer between the core-ZnSe and ligand L-Cys. The results show that the QDs with n

  12. Shell corrections in stopping powers

    Science.gov (United States)

    Bichsel, H.

    2002-05-01

    One of the theories of the electronic stopping power S for fast light ions was derived by Bethe. The algorithm currently used for the calculation of S includes terms known as the mean excitation energy I, the shell correction, the Barkas correction, and the Bloch correction. These terms are described here. For the calculation of the shell corrections an atomic model is used, which is more realistic than the hydrogenic approximation used so far. A comparison is made with similar calculations in which the local plasma approximation is utilized. Close agreement with the experimental data for protons with energies from 0.3 to 10 MeV traversing Al and Si is found without the need for adjustable parameters for the shell corrections.

  13. Circular polarisation measurements of the L sub. alpha. cascade radiation for the 3 sup 2 D sub j states of atomic hydrogen, excited by electron impact

    Energy Technology Data Exchange (ETDEWEB)

    Farrell, D.; Slevin, J. (Saint Patrick' s Coll., Maynooth (Ireland)); Chwirot, S. (Uniwersytet Mikolaja Kopernika, Torun (Poland). Inst. Fizyki); Srivastava, R. (Roorkee Univ. (India). Dept. of Physics)

    1990-01-28

    Measurements are reported for the circular polarisation of the L{sub {alpha}} radiation arising from the cascade of the 3{sup 2}D{sub j} states of atomic hydrogen to the 2{sup 2}P{sub j} states detected in coincidence with electrons with n = 3 energy loss. Data for the atomic orientation parameter L {sub perpendicular} are presented at incident electron energies of 54.4 and 100 eV and at scattering angles {theta}{sub e} of 20{sup 0} and 25{sup 0}. These data, together with previous measurements for this transition, constitute a determination of the complete parameter set {l brace}{gamma}, P{sub 1}, {rho}{sub 00}, L {sub perpendicular}{r brace} for 3{sup 2}D{sub j} excitations in this dynamic range. Calculations for P{sub 3} and L {sub perpendicular} using distorted-wave approximation theory are also performed. The theoretical results are presented and compared with the experimental data. (author).

  14. Study on atomic layer deposition preparation of core-shell structured nanometer materials%原子层沉积方法制备核-壳型纳米材料研究

    Institute of Scientific and Technical Information of China (English)

    李勇; 李惠琪; 夏洋; 刘邦武

    2013-01-01

    Monocrystal Pt nanoparticles, amorphous Al2O3 thin film, polycrystalline ZnO and TiO2 thin films were fabricated on black carbon nanoparticles by means of atomic layer deposition (ALD). Using high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectrometer (XPS), energy dispersive spectroscopy (EDS), We have characterized and analyzed the surface morphology, crystal structure and composition of the ranopasticles and thin filins. Results indicate that the ALD method is an ideal method to prepare core-shell stuctured nanometer materials. In addition, the reasons why the formation of ALD films with different crystal morphologies, such as monocrystal, amorphous, polycrystalline, were discussed.%采用原子层沉积方法在碳黑纳米颗粒表面分别沉积Al2 O3, ZnO, TiO2和Pt,成功制备出核-壳型纳米材料。通过高分辨率透射电子显微镜、X射线光电子能谱仪、能谱仪对材料的表面形貌、晶体结构、薄膜成分进行了表征和分析。结果表明,原子层沉积方法是制备核壳型纳米材料的理想方法。此外,还分析了采用原子层沉积方法沉积不同材料,所生长的薄膜材料有单晶、多晶、非晶等多种存在形式的形成原因。

  15. Atomic inner shell ionization: a new method of nuclear interaction lifetimes in the range 10-16-10-18 second. Lifetime measurement of the compound nucleus in the reaction 106Cd+p (Ep=10 and 12 MeV)

    International Nuclear Information System (INIS)

    A new method to measure the lifetime of the compound nucleus formed in the reaction 106Cd+p at Ep=10 and 12 MeV is described. The nuclear lifetime is compared to the known lifetime of an atomic inner shell vacancy created in the entrance channel of the nuclear reaction. If the ionization probability in he way-in of the nuclear reaction is kown the compound nucleus lifetime is deduced by a simple relation from the number of compound X-rays measured in coincidence with one of the reaction products. A large number of ionization probability values measured in very small impact parameter collisions induced by H+, He+, D+ on Al, Cu, S, Ti, Si, Ag, Cd are reported. The data are interpreted in terms of the corrected SCA theory of ionization. New effects such as angular dependence and trajectory effect (hair-pin-curve effect) are shown experimentally. The influence of a nuclear delay time on the ionization probability value is considered; the effect on a nuclear reaction of the energy losses by the projectile during the ionization process is analysed in detail. The yield curve of the resonant nuclear reaction 27Al(p,γ)28Si is taken as an example. A detailed analysis of the compound nucleus 107In lifetimes is given. Attention has been paid to competitive processes leading to X ray emission of same energy as the compound X rays. Extensions of the method to measure compound nucleus lifetimes in collision induced by heavy ions and to separate the shape elastic and compound elastic mechanisms are presented

  16. Determination of silver at ng mL-1 levels by preconcentration on a W-coil trap and hydride generation atomic absorption spectrometry

    International Nuclear Information System (INIS)

    Complete text of publication follows. A classical hydride generation atomic absorption spectrometry flow system consists of a reaction coil, a stripping coil, a gas liquid separator (GLS) and a heated quartz T-tube atomizer. There have been some studies for determination of Ag by using this classical hydride generation system; however, only mg L-1 levels could be determined. In this study, three types of gas-liquid separators, namely, U-shape, cylindrical and a novel large volume device were used. It was possible to determine Ag in ng mL-1 level when stripping coil was eliminated from the system. The calibration plot was linear in the range of 50 to 500 ng mL-1 using a U-shape GLS. The 3s limit of detection (LOD) is 29 ng mL-1 and characteristic concentration value, C0, were found to be 15.3 ng mL-1. The similar set-up was used also with a cylindrical GLS; it was observed that the efficiency of this GLS is about 10 fold higher than the U-shape GLS; linear working range was 5.0 to 50 ng mL-1. LOD (3s) and C0 values were found to be 3.0 ng mL-1 and 2.9 ng mL-1, respectively. In order to minimize the memory effects, a 10% (v/v) solution of dichlorodimethylsilane in toluene was used to silanize both gas liquid separators to deactivate their internal surfaces. In addition to these studies, a novel large volume GLS was used. In this device 15.0 mL of mixed acidic analyte solution and NaBH4 were placed. Argon gas was passed through this mixture for 90 seconds and formed volatile analyte species were sent to a W-coil trap heated at an optimized temperature. The calibration plot was linear between 0.10 and 0.75 ng mL-1; the LOD (3s) and C0 were found to be 0.049 ng mL-1 and 0.050 ng mL-1, respectively.

  17. The Hanbury Brown ant Twiss effect for cold atoms; L'effet Hanbury Brown et Twiss pour les atomes froids

    Energy Technology Data Exchange (ETDEWEB)

    Schellekens, M

    2007-05-15

    This thesis deals with the measurement of the quantum intensity correlations in gases of metastable Helium. The measurement has been performed on thermal gases of bosonic He{sup 4} and fermionic He{sup 3}, as well as on Bose-Einstein condensates. In 1956, Robert Hanbury Brown et Richard Twiss measured the correlation between photons emitted from a single thermal source. The consequently demonstrated that the photons emitted by such a source tend to arrive grouped on a detector (Hanbury Brown and Twiss effect). This bunching characterizes bosons from a non-coherent source. Fermions show an anti-bunching behaviour in the same conditions. By using metastable Helium atoms, that can be detected individually through the use of micro-channel plates, we have been able to show a similar bunching of bosons He{sup 4} from thermal sources around the micro-kelvin. As expected, the coherence of the Bose-Einstein condensates did not produce a particular correlation. The measurement on thermal gases of fermionic He{sup 3} has demonstrated the anti-bunching. Particular effort has been employed in describing the micro-channel plate based delay-line detector, the key to the experiment. (author)

  18. A novel analytical system involving hydride generation and gold-coated W-coil trapping atomic absorption spectrometry for selenium determination at ng l-1 level

    International Nuclear Information System (INIS)

    A novel analytical technique was developed where gaseous hydrogen selenide formed by sodium tetrahydroborate reduction is transported to and trapped on a resistively heated gold-coated W-coil atom trap for in situ preconcentration. Gold coating on W-coil was prepared by using an organic solution of Au. The atom trap is held at 165 oC during the collection stage and is heated up to 675 deg. C for revolatilization; analyte species formed are transported to an externally heated quartz T-tube where the atomization takes place and the transient signal is obtained. The carrier gas consisted of 112.5 ml min-1 Ar with 75 ml min-1 H2 during the collection step and 112.5 ml min-1 Ar with 450 ml min-1 H2 in the revolatilization step. The half width of the transient signal obtained is less than 0.5 s. The RSD for the measurements was found to be 3.9% (n = 11) for 0.10 μg l-1 Se using peak height measurements. The calibration plot for 27.0 ml of sample collected in 4.0 min using a flow rate of 6.75 ml min-1 was linear between 0.13 and 2.0 μg l-1 of Se. The limit of detection (3 s) is 39 ng l-1. The enhancement factor for the characteristic concentration (Co) was found to be 20.1 when compared to conventional hydride generation atomic absorption spectrometry system without trap. In order to check the accuracy of the method, standard reference material, natural water NIST 1640 was employed; the result was found to be in good agreement with the certified value at the 95% confidence level

  19. Experimental and theoretical studies of metal vapor atoms

    International Nuclear Information System (INIS)

    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

  20. L-tyrosine immobilized on multiwalled carbon nanotubes: a new substrate for thallium separation and speciation using stabilized temperature platform furnace-electrothermal atomic absorption spectrometry.

    Science.gov (United States)

    Pacheco, Pablo H; Gil, Raúl A; Smichowski, Patricia; Polla, Griselda; Martinez, Luis D

    2009-12-10

    An approach for the separation and determination of inorganic thallium species is described. A new sorbent, L-tyrosine-carbon nanotubes (L-tyr-CNTs), was used and applied to the analysis of tap water samples. At pH 5.0, L-tyr was selective only towards Tl(III), while total thallium was determined directly by stabilized temperature platform furnace-electrothermal atomic absorption spectrometry (STPF-ETAAS). The Tl(III) specie, which was retained by L-tyrosine, was quantitatively eluted from the column with 10% of nitric acid. An on-line breakthrough curve was used to determine the column capacity, which resulted to be 9.00 micromol of Tl(III) g(-1) of L-tyr-CNTs with a molar ratio of 0.14 (moles of Tl bound to moles of L-tyr at pH 5). Transient peak areas revealed that Tl stripping from the column occurred instantaneously. Effects of sample flow rate, concentration and flow rate of the eluent, and interfering ions on the recovery of the analyte were systematically investigated. The detection limit for the determination of total thallium (3sigma) by STPF-ETAAS was 150 ng L(-1). The detection limit (3sigma) for Tl(III) employing the separation system was 3 ng L(-1), with an enrichment factor of 40. The precision of the method expressed as the relative standard deviation (RSD) resulted to be 3.4%. The proposed method was applied to the speciation and determination of inorganic thallium in tap water samples. The found concentrations were in the range of 0.88-0.91 microg L(-1) of Tl(III), and 3.69-3.91 microg L(-1) of total thallium. PMID:19932812

  1. Updated Atomic Data and Calculations for X-ray Spectroscopy

    CERN Document Server

    Foster, A R; Smith, R K; Brickhouse, N S

    2012-01-01

    We describe the latest release of AtomDB, version 2.0.2, a database of atomic data and a plasma modeling code with a focus on X-ray astronomy. This release includes several major updates to the fundamental atomic structure and process data held within AtomDB, incorporating new ionization balance data, state-selective recombination data, and updated collisional excitation data for many ions, including the iron L-shell ions from Fe$^{+16}$ to Fe$^{+23}$ and all of the hydrogen- and helium-like sequences. We also describe some of the effects that these changes have on calculated emission and diagnostic line ratios, such as changes in the temperature implied by the He-like G-ratios of up to a factor of 2.

  2. Grazing incidence collisions of ions and atoms with surfaces: from charge exchange to atomic diffraction; Collisions rasantes d'ions ou d'atomes sur les surfaces: de l'echange de charge a la diffraction atomique

    Energy Technology Data Exchange (ETDEWEB)

    Rousseau, P

    2006-09-15

    This thesis reports two studies about the interaction with insulating surfaces of keV ions or atoms under grazing incidence. The first part presents a study of charge exchange processes occurring during the interaction of singly charged ions with the surface of NaCl. In particular, by measuring the scattered charge fraction and the energy loss in coincidence with electron emission, the neutralization mechanism is determined for S{sup +}, C{sup +}, Xe{sup +}, H{sup +}, O{sup +}, Kr{sup +}, N{sup +}, Ar{sup +}, F{sup +}, Ne{sup +} and He{sup +}. These results show the importance of the double electron capture as neutralization process for ions having too much potential energy for resonant capture and not enough for Auger neutralization. We have also studied the ionisation of the projectile and of the surface, and the different Auger-like neutralization processes resulting in electron emission, population of conduction band or excited state. For oxygen scattering, we have measured an higher electron yield in coincidence with scattered negative ion than with scattered atom suggesting the transient formation above the surface of the oxygen doubly negative ion. The second study deals with the fast atom diffraction, a new phenomenon observed for the first time during this work. Due to the large parallel velocity, the surface appears as a corrugated wall where rows interfere. Similarly to the Thermal Atom Scattering the diffraction pattern corresponds to the surface potential and is sensitive to vibrations. We have study the H-NaCl and He-LiF atom-surface potentials in the 20 meV - 1 eV range. This new method offers interesting perspectives for surface characterisation. (author)

  3. First-principles all-electron theory of atomic short-range ordering in metallic alloys: D022- versus L12-like correlations

    International Nuclear Information System (INIS)

    We use a ''first-principles'' concentration-wave approach based on a finite-temperature, electronic density-functional, mean-field, grand potential of the random alloy to investigate the high-temperature atomic short-range order (ASRO) in Ni75V25 and Pd75V25 solid solutions. Experimentally, these similar alloys both develop D022-type long-range order at low temperatures but different ASRO at high temperatures. Our calculations describe the measured ASRO well. We compare these results with those found for a hypothetical Co75Ti25 solid solution. Since this alloy orders directly from the melt into the L12 phase, it should exhibit strong L12-like ASRO, as we find in our calculations. We analyze the features in the calculated diffuse intensities in terms of various factors in each alloy's electronic structure. Because we have assumed that the atoms are fixed to the Bravais lattice, we discuss two additional examples, Al75Ti25 and Ni50Pt50, to show the limitations of neglecting atomic displacements. Notably, the Onsager cavity fields have been incorporated into the theory to conserve the diffuse scattering intensity over the Brillouin zone and to provide a better description of the long-ranged, electrostatic screening effects

  4. Coupling experimental and field-based approaches to decipher carbon sources in the shell of the great scallop, Pecten maximus (L.)

    Science.gov (United States)

    Marchais, V.; Richard, J.; Jolivet, A.; Flye-Sainte-Marie, J.; Thébault, J.; Jean, F.; Richard, P.; Paulet, Y.-M.; Clavier, J.; Chauvaud, L.

    2015-11-01

    This research investigated how the carbon isotopic composition of food source (δ13Cfood) and dissolved inorganic carbon (δ13CDIC) influences the carbon isotopic composition of Pecten maximus shells (δ13Cshell) under both experimental and natural conditions. The objectives are to better understand the relationship between P. maximus and its environment, and to specifically distinguish conditions under which calcification is influenced by respired CO2 derived from food sources versus conditions in which calcification uses inorganic carbon from seawater. Laboratory experiment investigated carbon incorporation into shell carbonates by maintaining scallops under conditions where the stable carbon isotopic composition of food sources was considerably depleted (-54‰), relative to values observed in the natural environment (-21‰). Laboratory experiment ran for 78 days under three temperature conditions, 15 °C, 21 °C and 25 °C. A survey of the environmental parameters and stable carbon isotopic composition into shell carbonate of natural population of P. maximus was also realized during the same year in the Bay of Brest, France. Data collected from both laboratory experiment and the natural environment confirmed that both δ13CDIC and δ13Cfood influence δ13Cshell values and that organic carbon incorporation (CM) averages about 10% (4.3-6.8% under experimental conditions and 1.9-16.6% in the natural environment). The shift in stable carbon isotopic composition from the uptake of depleted food sources under experimental conditions realized a marked divergence in the predicted equilibrium between calcium carbonate and ambient bicarbonate, relative to the natural environment. This offset was 1.7 ± 0.6‰ for scallops in their natural environment and 2.5 ± 0.5 and 3.2 ± 0.9‰ for scallops under experimental conditions at water temperatures of 15 °C and 21 °C, respectively. The offset of 3‰ for scallops subjected to laboratory experiment could not be explained

  5. Open shells in reduced-density-matrix-functional theory

    OpenAIRE

    Lathiotakis, N. N.; Helbig, N.; Gross, E. K. U.

    2005-01-01

    Reduced-density-matrix-functional theory is applied to open-shell systems. We introduce a spin-restricted formulation by appropriately expressing approximate correlation-energy functionals in terms of spin-dependent occupation numbers and spin-independent natural orbitals. We demonstrate that the additional constraint of total-spin conservation is indispensable for the proper treatment of open-shell systems. The formalism is applied to the first-row open-shell atoms. The obtained ground-state...

  6. A study of the kinetic energy density functional for atoms

    International Nuclear Information System (INIS)

    This paper studies the rigorous kinetic energy density functional at the level of the Hartree-Fock method for closed electron shell atoms. The behaviour of the kinetic energy and its components, is analysed as the atomic number N increases. It is shown that the increments of the specific energies for two consecutive closed electron shells atoms depend distinctly on the electron configuration of the last electron shell. 35 refs, 1 fig., 4 tabs

  7. Growth morphology of {l_brace}1 1 0{r_brace} faces of manganese mercury thiocyanate crystals investigated by atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Geng, Y.L. [State Key Laboratory of Crystal Materials, Institute of Crystal Materials, Shandong University, Jinan 250100 (China)]. E-mail: ylgeng@icm.sdu.edu.cn; Xu, D. [State Key Laboratory of Crystal Materials, Institute of Crystal Materials, Shandong University, Jinan 250100 (China)]. E-mail: xdoffice@sdu.edu.cn; Wang, X.Q. [State Key Laboratory of Crystal Materials, Institute of Crystal Materials, Shandong University, Jinan 250100 (China); Du, W. [State Key Laboratory of Crystal Materials, Institute of Crystal Materials, Shandong University, Jinan 250100 (China); Liu, H.Y. [State Key Laboratory of Crystal Materials, Institute of Crystal Materials, Shandong University, Jinan 250100 (China); Zhang, G.H. [State Key Laboratory of Crystal Materials, Institute of Crystal Materials, Shandong University, Jinan 250100 (China)

    2006-04-10

    Atomic force microscopy is employed to investigate the surface morphology of the {l_brace}1 1 0{r_brace} faces of MMTC crystals grown at 40 deg. C at a supersaturation of {sigma} = 0.5. Growth hillocks generated by dislocation sources often appear in groups, which leads to faster growth of the local area and forming layers with large height difference up to 30 nm. Growth centers operate nearly equally during the growth process. Serried and sparse monolayer steps dominate alternately on the surface, which is thought to be distinct phenomenon of the two-metal-centered complex compounds family.

  8. Teaching Valence Shell Electron Pair Repulsion (VSEPR) Theory

    Science.gov (United States)

    Talbot, Christopher; Neo, Choo Tong

    2013-01-01

    This "Science Note" looks at the way that the shapes of simple molecules can be explained in terms of the number of electron pairs in the valence shell of the central atom. This theory is formally known as valence shell electron pair repulsion (VSEPR) theory. The article explains the preferred shape of chlorine trifluoride (ClF3),…

  9. Vessel for cryogenic liquid with a flexible vacuum shell

    International Nuclear Information System (INIS)

    A 100 l vessel for a cryogenic liquid is described. Specific feature of its design is the substitution of a rigid cylindrical shell of vacuum jacket with a flexible shell made of 0.34 mm lawsan foil. Heat influx for a 82 l hydrogen vessel was 65 Wt. Inside the vessel an additional shell is mounted which diminishes 6 fold the heat influx to liquid hydrogen at an instant filling up of a vacuum space with air

  10. Theoretical study of inner-shell ionization by heavy-particle impact

    International Nuclear Information System (INIS)

    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, L3-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 Ef = 0 and angular momentum lf = 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 ψi(r)dr, for arbitrary final state energy Ef and angular momentum lf. The ψk(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 approximation (SCA

  11. L-半胱氨酸-原子荧光法测定食品中的硒%Determination of selenium in food by L-Cysteine atomic fluorescence spectrometry

    Institute of Scientific and Technical Information of China (English)

    牛晓梅

    2011-01-01

    目的:利用氢化物发生-原子荧光光谱法,在L-半胱氨酸存在下,测定食品中的硒.方法:样品经酸加热消化后,用2%盐酸溶液做载流,原子荧光分光光度计进行测定.结果:方法的测定范围为10.0μg/L~50.0μg/L,相对标准偏差为0.70%~1.90%,回收率为93.0%~101.0%,检出限为0.051μg/L.结论:由于L-半胱氨酸的存在,改善了氢化物发生条件,增敏光谱测定信号,降低了溶液的酸度,金属离子的干扰显著地得到了抑制,适用于食品中硒的测定.%Objective: In this paper, we give a method for determination of selenium in food by hydride generation -atomic fluorescence spectrometry in the presence of L- Cysteine.Methods: Using 2% hydrochloric acid as carrier liquid, the samples were determined by atomic fluorescence spectrometry after been digested by heating in acid.Results: The measurement range of this method was 10.0 μg/L ~ 50.0 μg/L, the RSD 0.7 % ~ 1.9%, the recoveries were in the range of 93.0% ~ 101.0% and the detection limits of this method were found to be 0.051 μg/L.Conclusion: In the presence of L - Cysteine, the hydride generation conditions were improved, the spectrometric signal was enhanced, and the acidity of solution was reduced.In addition, the interferences of the metal elements were significantly inhibited.The method can be used to determine seleium in food.

  12. Nuclear and atomic models

    International Nuclear Information System (INIS)

    A theorem concerning fermion interaction is postulated and applied to the problems of atomic (electronic) and nuclear physics. Model building based solely upon the postulate that adjacent like fermions must be singlet paired accounts for the closed shells of both nuclear and atomic structure. The implied antiferromagnetic FCC lattice of protons and neutrons in alternating layers has been found by previous workers to be the lowest-energy solid configuration of nuclear matter (N = P). The buildup of the FCC lattice from a central tetrahedron reproduces all of the shells and subshells of the isotropic harmonic oscillator, which is the basis for the shell model. In atomic structure, the singlet pairing of adjacent electrons implies closed-shell structures uniquely at the six noble gases and the three noble metals, Ni, Pd, and Pt. The basis for the postulate concerning fermions is found in terms of classical electrodynamics; it is a microscopic corollary of Biot-Savart's law that parallel currents attract whereas antiparallel currents repel. (author)

  13. Shell ontogeny in radiolarians

    Digital Repository Service at National Institute of Oceanography (India)

    Anderson, O.R.; Gupta, S.M.

    The ontogeny of the shells in modern and ancient radiolarian species, Acrosphaera cyrtodon were observed by scanning and transmission electron microscopy. The shells of A. cyrtodon were obtained from core samples collected from the Central Indian...

  14. K-shell vacancy production and sharing in (0.2-1.75) MeV/u Fe, Co + Cr collisions

    International Nuclear Information System (INIS)

    K-shell ionization cross sections measured in the near-symmetric collision systems Fe, Co + Cr at 0.2-1.75 MeV/u energies are reported. The cross section values have been corrected for multiple ionization in the outer (L, M) shells using the energy and yield shift method. Mean ionization probabilities per electron in the outer shells have been estimated. In the Fano-Lichten model of quasimolecular excitation, 2pσ molecular orbital (MO) ionization cross sections and mean 2pσ -1sσ MO vacancy sharing probabilities were obtained. A one-step process calculation (Briggs model using SCA calculations with relativistic hydrogenic wave functions and binding correction) is in good agreement with the 2pσ MO ionization cross sections at higher bombarding energies (≥1 MeV/u). The remaining discrepancy at lower energies could not be reduced by considering the contribution of single collision two step or multiple collision processes. The vacancy sharing results show that an exponential dependence of the vacancy sharing in function of reciprocal velocity is less fulfilled at higher (≥1.5 MeV/u) energies. Concerning the present multiple ionization data, the Cr M-shell probability is comparable with that of the Cr L-shell for both collision systems, in contrast with the results for the projectile. In the latter case, a larger M-shell multiple ionization in comparison with that of the L-shell is found. The result for the target atom could be qualitatively explained by a rapid partially filling of the M-shell vacancies within the solid target. (authors)

  15. Determination of air Stannum in Workplace by L-cysteine and Atomic Fluorescence Spectrometry%工作场所空气中锡的L-半胱氨酸-原子荧光测定法

    Institute of Scientific and Technical Information of China (English)

    牛晓梅

    2011-01-01

    [Objective]To determine the air stannum in workplaces by hydride generation-atomic fluorescence spectrometry, with the existence of L-cysteine. [ Methods ] After digested by hydrochloric acid, the samples were determined by atomic fluorescence spectrometer with 2% hydrochloric acid as carrier liquid. [ Results] The range of measurement was 5. 0 ~ 200.0 μg/L, the RSD was 2.15% ~ 3.40%, the recoveries ranged from 92. 5% ~ 103.5% ,and the detection limits of this method was 0. 71 μg/L [ Conclusion] Due to the presence of L-cysteine, the hydride generation conditions are improved, the spectrometric signal is enhanced, and the acidity of solution is reduced. In addition, the interferences of the metal elements are significantly inhibited. The method is suitable for determination of air stannum in workplace.%目的 利用氢化物发生-原子荧光光谱法,在L-半胱氨酸存在的情况下,测定工作场所空气中的锡.方法 样品经盐酸消解,用2%盐酸溶液做载流,原子荧光分光光度计进行测定.结果 方法的测定范围为5.0~200.0 μg/L,相对标准偏差为2.15%~3.40%,回收率为92.5%~103.5%,检出限为0.71 μg/L.结论 由于L-半胱氨酸的存在,改善了氢化物发生条件,增敏光谱测定信号,降低了溶液的酸度,金属离子的干扰显著地得到了抑制,适用于工作场所空气中锡的测定.

  16. Collisional-radiative modeling of the L-shell emission of Mo30+ to Mo33+ emitted from a high-temperature endash low-density tokamak plasma

    International Nuclear Information System (INIS)

    The x-ray spectra of several highly stripped molybdenum ions have been recorded between 0.6 and 5.5 A in the Frascati tokamak upgrade with a rotating crystal spectrometer. Detailed, quasi-steady-state collisional-radiative models have been used to interpret emission features from inner shell, electron impact excitations in molybdenum ions near the neonlike charge state and to characterize the charge state distribution in the plasma. Processes such as resonant excitation, excitation autoionization, and dielectronic recombination have been included in the models of the molybdenum ions close-quote emission features. Introducing the excitation-autoionization process into ionization equilibrium calculations brings agreement between observations and calculations of the relative ionization equilibrium fractions of highly stripped molybdenum ions. Absolutely calibrated spectra and detailed models for the excitation processes in these molybdenum ions allow us to calculate crucial plasma parameters, such as the concentration of impurity ions in the plasma and the amount of power lost from the plasma through impurity line radiation. copyright 1996 The American Physical Society

  17. Monitoring of the Phenix reactor conic shell

    International Nuclear Information System (INIS)

    The Safety Authority (DSIN) asked the monitoring of Phenix reactor core support structures. In this framework the cea developed a method to control by ultrasonic testing the welded joints of the core support shell, in stainless steel-316L, immersed in sodium. The method and the inspection are presented in this paper. (A.L.B.)

  18. Assessment of productivity and water use efficiency in three maize (zea mays L.) varieties in Kwabenya-Atomic area

    International Nuclear Information System (INIS)

    The production of rain-fed maize in the Kwabenya-Atomic area of the coastal savannah environment of Ghana is limited by low and erratic rainfall. Enhancing maize production in the area will require the use of maize varieties efficient in the use of soil moisture. The study was, therefore, conducted to evaluate three recently released maize varieties (Obatanpa, Mamaba, and Golden Crystal) for their efficiency in the use of soil moisture for total dry matter and grain production and consequently identify the maize varieties suitable for rain-fed production in the Kwabenya-Atomic area. Field experiments were conducted m 2008 during the major and minor cropping seasons at Kwabenya-Atomic area in Ghana using three maize varieties grown at a planting distance of 0.4 m within rows and 0.8 m between rows. The experimental design used was the randomised complete block design in four replicates. Plants were sampled every two weeks throughout the maize growing seasons. Access tubes installed in each sub-plot facilitated simultaneous moisture monitoring with the aid of a neutron probe (CPN(R) 503 Hydroprobe) in a 120 cm soil profile. The moisture content values were used for the estimation of actual evapotranspiration of the maize crop using the water balance approach. Grain yield (GY) and its associated water use efficiency (WUEGY) were significantly different (P ≤ 0.05) among the maize varieties during the major cropping season with Mamaba producing the highest grain yield of 7250.0 kg ha-1 and WUEGY of 13.2 kg ha-1 mm-1. For the minor cropping season, no significant difference was observed in grain yield, which ranged between 5800.0 and 7200.0 kg ha-1, with Obatanpa producing the highest grain yield. No significant difference was observed in WUEGY during the minor cropping season which ranged between 14.6 and 19.1 kg ha-1 mm-1 with Obatanpa having the highest WUEGY. The maize genotype produced similar total dry matter (TDM) during each of the cropping seasons. However, a

  19. Atom clusters and vibrational excitations in chemically-disordered Pt357Fe

    International Nuclear Information System (INIS)

    Inelastic nuclear resonant scattering spectra of 57Fe atoms were measured on crystalline alloys of Pt357Fe that were chemically disordered, partially ordered, and L12 ordered. Phonon partial density of states curves for 57Fe were obtained from these spectra. Upon disordering, about 10% of the spectral intensity underwent a distinct shift from 25 to 19 meV. This change in optical modes accounted for most of the change of the vibrational entropy of disordering contributed by Fe atoms, which was (+0.10 ± 0.03) kB (Fe atom)-1. Prospects for parametrizing the vibrational entropy with low-order cluster variables were assessed. To calculate the difference in vibrational entropy of the disordered and ordered alloys, the clusters must be large enough to account for the abundances of several of the atom configurations of the first-nearest-neighbor shell about the 57Fe atoms. (c) 2000 The American Physical Society

  20. Antiprotonic Helium Atoms

    OpenAIRE

    Kartavtsev, O. I.

    1995-01-01

    Metastable antiprotonic helium atoms $^{3,4}\\! H\\! e\\bar pe$ have been discovered recently in experiments of the delayed annihilation of antiprotons in helium media. These exotic atoms survive for an enormous time (about tens of microseconds) and carry the extremely large total angular momentum $L\\sim 30-40$. The theoretical treatment of the intrinsic properties of antiprotonic helium atoms, their formation and collisions with atoms and molecules is discussed.

  1. Calculation of the energy loss of swift H and He ions in Ag using the dielectric formalism: the role of inner-shell ionization

    OpenAIRE

    Abril Sánchez, Isabel; Moreno Marín, Juan Carlos; Fernández Varea, José M.; Denton Zanello, Cristian D.; Heredia Ávalos, Santiago; García Molina, Rafael

    2007-01-01

    The electronic energy loss of swift H and He ions in solid Ag is studied theoretically within the dielectric formalism, considering the different equilibrium charge states of the projectile inside the target. Excitation of the weakly-bound (outer) electrons is described by a superposition of Mermin-type energy-loss functions, whereas the contribution to the projectile energy loss due to the ionization of the K, L and M shells of the Ag atoms is included through hydrogenic or numerical general...

  2. Interaction of a slow monopole with a hydrogen atom

    OpenAIRE

    Shnir, Ya. M.

    1996-01-01

    The electric dipole moment of the hydrogen-like atom induced by a monopole moving outside the electron shell is calculated. The correction to the energy of the ground state of the hydrogen atom due to this interaction is calculated.

  3. Application of l-cystine modified zeolite for preconcentration and determination of ultra-trace levels of cadmium by flame atomic absorption spectrometry.

    Science.gov (United States)

    Rezvani, Seyyed Ahmad; Soleymanpour, Ahmad

    2016-03-01

    A very convenient, sensitive and precise solid phase extraction (SPE) system was developed for enrichment and determination of ultra-trace of cadmium ion in water and plant samples. This method was based on the retention of cadmium(II) ions by l-cystine adsorbed in Y-zeolite and carry out in a packed mini-column. The retained cadmium ions then were eluted and determined by flame atomic absorption spectrometry. The scanning electron microscopy (SEM), powder X-ray diffraction (XRD) and Fourier Transform Infrared (FT-IR) spectroscopy techniques were applied for the characterization of cystine modified zeolite (CMZ). Some experimental conditions affecting the analytical performance such as pH, eluent type, concentration of sample, eluent flow rate and also the presence of interfering ions were investigated. The calibration graph was linear within the range of 0.1-7.5ngmL(-1) and limit of detection was obtained 0.04ngmL(-1) with the preconcentration factor of 400. The relative standard deviation (RSD) was obtained 1.4%, indicating the excellent reproducibility of this method. The proposed method was successfully applied for the extraction and determination of cadmium(II) ion in black tea, cigarette's tobacco and also various water samples. PMID:26852265

  4. Simple and Onion-type Fullerenes shells as resonators and amplifiers

    CERN Document Server

    Amusia, M Ya

    2009-01-01

    We discuss the influence of a single or double fullerenes shell upon photoionization and vacancy decay of an atom, stuffed inside the fullerenes construction. The main manifestations of this influence are additional structures in the photoionization cross-section and variation of the vacancy decay probability. The main mechanisms, with which fullerenes shells affect the processes in caged atoms is the scattering of the outgoing electrons by the fullerenes shell and modification of the photon beam due to fullerenes shell polarization. General consideration will be illustrated by numeric calculations where C60 and C240 will be chosen as fullerenes and Ar and Xe as caged atoms.

  5. Deeply bound pionic atom

    International Nuclear Information System (INIS)

    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, 2Heπ-) 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.)

  6. Atomic physics with highly charged ions

    International Nuclear Information System (INIS)

    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

  7. Atomic force microscopy studies on growth mechanisms and defect formations on {l_brace}110{r_brace} faces of cadmium mercury thiocyanate crystals

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, X.N.; Xu, D.; Yuan, D.R.; Sun, D.L.; Lu, M.K.; Zhang, G.H.; Guo, S.Y. [Shandong Univ., Jinan, SD (China). Inst. of Crystal Materials

    2001-07-01

    Growth mechanisms and defect formations on {l_brace}110{r_brace} faces of cadmium mercury thiocyanate crystals grown at 30 C ({sigma} = 0.24) were investigated by using atomic force microscopy (AFM). It was found that, under this condition, spiral dislocation controlled mechanism and 2D nucleation mechanism operates simultaneously and equally during growth, which is completely different from the traditional 2D nucleation and dislocation source controlled mechanisms. A number of 2D nucleus are formed at the large step terraces generated by dislocation sources, leading to the unequal growth rates of the elementary steps and thereby ''step bunches'' are caused. Various defects are formed under this growth condition, which is assumed to result from the incongruence between the steps generated by different sources. A new kind of 2D defect, corresponding to one growth layer in height, was observed for the first time. (orig.)

  8. Financial and operational information 1988-1992: Royal Dutch/Shell Group of Companies

    International Nuclear Information System (INIS)

    This booklet supplements the 1992 annual reports of the Royal Dutch Petroleum Company and the Shell Transport Trading company, p.l.c., which contain financial statements and information on the Royal Dutch/Shell Group of companies

  9. Atomic far-IR fine-structure line mapping of L1630, M17, and W3: Comparison of (O I) and (C II) distributions

    Science.gov (United States)

    Howe, J. E.; Jaffe, Dan T.; Zhou, Shudong

    1995-01-01

    We mapped the distribution of atomic far-IR line emission from (O I) and (C II) over parsec scales in the Galactic star-forming regions L1630, M17, and W3 using the MPE Far-Infrared Fabry-Perot Imaging spectrometer (FIFI) on board the NASA Kuiper Airborne Observatory. The lines mapped include (O I) 63 microns, (O I) 146 microns, and (C II) 158 microns. Comparison of the intensities and ratios of these lines with models of photodissociation regions (e.g., Tielens & Hollenbach 1985, ApJ, 344, 770) allows us to derive temperatures and densities of the primarily neutral atomic gas layers lying on the surfaces of UV-illuminated molecular gas. In general, the (C II) line arises ubiquitously throughout the molecular clouds while the (O I) lines are mainly confined to warm, dense gas (T is greater than 100 K, n is greater than 10(exp 4)/cu cm) near the sites of O and B stars. The distribution of (C II) in the star-forming clouds implies that the (C II) emission arises on the surfaces of molecular clumps throughout the clouds, rather than only at the boundary layer between molecular gas and H II regions.

  10. Point defects and irradiation in oxides: simulations at the atomic scale; Defauts ponctuels et irradiation dans les oxydes: simulation a l'echelle atomique

    Energy Technology Data Exchange (ETDEWEB)

    Crocombette, J.P

    2005-12-15

    The studies done by Jean-Paul Crocombette between 1996 and 2005 in the Service de Recherches de Metallurgie Physique of the Direction de l'Energie Nucleaire in Saclay are presented in this Habilitation thesis. These works were part of the material science researches on the ageing, especially under irradiation, of oxides of interest for the nuclear industry. In this context simulation studies at the atomic scale were performed on two elementary components of ageing under irradiation : point defects and displacement cascades ; using two complementary simulation techniques : ab initio electronic structure calculations and empirical potential molecular dynamics. The first part deals with point defects : self defects (vacancies or interstitials) or hetero-atomic dopants. One first recalls the energetics of such defects in oxides, the specific features of defects calculations and the expected accuracy of these calculations. Then one presents the results obtained on uranium dioxide, oxygen in silver and amorphous silica. The second part tackles the modelling of disintegration recoil nuclei in various?displacement cascades created by crystalline matrices for actinide waste disposal. Cascade calculations give access to the amorphization mechanisms under irradiation of these materials. One thus predicts that the amorphization in zircon takes place directly in the tracks whereas in lanthanum zirconate, the amorphization proceeds through the accumulation of point defects. Finally the prospects of these studies are discussed. (author)

  11. Simple and Onion-type Fullerenes shells as resonators and amplifiers

    OpenAIRE

    Amusia, M. Ya.

    2009-01-01

    We discuss the influence of a single or double fullerenes shell upon photoionization and vacancy decay of an atom, stuffed inside the fullerenes construction. The main manifestations of this influence are additional structures in the photoionization cross-section and variation of the vacancy decay probability. The main mechanisms, with which fullerenes shells affect the processes in caged atoms is the scattering of the outgoing electrons by the fullerenes shell and modification of the photon ...

  12. Methylmercury in water samples at the pg/L level by online preconcentration liquid chromatography cold vapor-atomic fluorescence spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Brombach, Christoph-Cornelius [Trace Element Speciation Laboratory, Department of Chemistry, Meston Walk, University of Aberdeen, Aberdeen AB24 3UE (United Kingdom); Chen, Bin; Corns, Warren T. [PS Analytical, Arthur House, Crayfields Industrial Estate, Main Road, Orpington, Kent BR5 3HP (United Kingdom); Feldmann, Jörg [Trace Element Speciation Laboratory, Department of Chemistry, Meston Walk, University of Aberdeen, Aberdeen AB24 3UE (United Kingdom); Krupp, Eva M., E-mail: e.krupp@abdn.ac.uk [Trace Element Speciation Laboratory, Department of Chemistry, Meston Walk, University of Aberdeen, Aberdeen AB24 3UE (United Kingdom)

    2015-03-01

    Ultra-traces of methylmercury at the sub-ppt level can be magnified in the foodweb and is of concern. In environmental monitoring a routine robust analytical method is needed to determine methylmercury in water. The development of an analytical method for ultra-trace speciation analysis of methylmercury (MeHg) in water samples is described. The approach is based on HPLC-CV-AFS with on-line preconcentration of water samples up to 200 mL, resulting in a detection limit of 40 pg/L (ppq) for MeHg, expressed as Hg. The unit consists of an optimized preconcentration column filled with a sulfur-based sorption material, on which mercury species are preconcentrated and subsequently eluted, separated and detected via HPLC-CV-AFS (high performance liquid chromatography–cold vapor atomic fluorescence spectrometry). During the method development a type of adsorbate material, the pH dependence, the sample load rate and the carry-over were investigated using breakthrough experiments. The method shows broad pH stability in the range of pH 0 to 7, without the need for buffer addition and shows limited matrix effects so that MeHg is quantitatively recovered from sewage, river and seawater directly in the acidified samples without sample preparation. - Highlights: • We demonstrate that a novel mixture of thiourea-thiolsilica shows an excellent trapping of MeHg between a broad pH range 1–6. • We develop the method so that it can potentially be automated for inorganic and methyl-mercury. • The method is matrix independent with highly accurate results for MeHg in hair CRM extracts and spiked water samples • The limit of detection is around 40 pg/L when just 200 mL sample is used, without any intensive preparation.

  13. Methylmercury in water samples at the pg/L level by online preconcentration liquid chromatography cold vapor-atomic fluorescence spectrometry

    International Nuclear Information System (INIS)

    Ultra-traces of methylmercury at the sub-ppt level can be magnified in the foodweb and is of concern. In environmental monitoring a routine robust analytical method is needed to determine methylmercury in water. The development of an analytical method for ultra-trace speciation analysis of methylmercury (MeHg) in water samples is described. The approach is based on HPLC-CV-AFS with on-line preconcentration of water samples up to 200 mL, resulting in a detection limit of 40 pg/L (ppq) for MeHg, expressed as Hg. The unit consists of an optimized preconcentration column filled with a sulfur-based sorption material, on which mercury species are preconcentrated and subsequently eluted, separated and detected via HPLC-CV-AFS (high performance liquid chromatography–cold vapor atomic fluorescence spectrometry). During the method development a type of adsorbate material, the pH dependence, the sample load rate and the carry-over were investigated using breakthrough experiments. The method shows broad pH stability in the range of pH 0 to 7, without the need for buffer addition and shows limited matrix effects so that MeHg is quantitatively recovered from sewage, river and seawater directly in the acidified samples without sample preparation. - Highlights: • We demonstrate that a novel mixture of thiourea-thiolsilica shows an excellent trapping of MeHg between a broad pH range 1–6. • We develop the method so that it can potentially be automated for inorganic and methyl-mercury. • The method is matrix independent with highly accurate results for MeHg in hair CRM extracts and spiked water samples • The limit of detection is around 40 pg/L when just 200 mL sample is used, without any intensive preparation

  14. Atomic Layer-by-Layer Deposition of Pt on Pd Nanocubes for Catalysts with Enhanced Activity and Durability toward Oxygen Reduction

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Shuifen; Choi, Sang; Lu, Ning; Roling, Luke T.; Herron, Jeffrey A.; Zhang, Lei; Park, Jinho; Wang, Jinguo; Kim, Moon J.; Xie, Zhaoxiong; Mavrikakis, Manos; Xia, Younan

    2014-06-11

    An effective strategy for reducing the Pt content while retaining the activity of a Pt-based catalyst is to deposit the Pt atoms as ultrathin skins of only a few atomic layers thick on nanoscale substrates made of another metal. During deposition, however, the Pt atoms often take an island growth mode because of a strong bonding between Pt atoms. Here we report a versatile route to the conformal deposition of Pt as uniform, ultrathin shells on Pd nanocubes in a solution phase. The introduction of the Pt precursor at a relatively slow rate and high temperature allowed the deposited Pt atoms to spread across the entire surface of a Pd nanocube to generate a uniform shell. The thickness of the Pt shell could be controlled from one to six atomic layers by varying the amount of Pt precursor added into the system. Compared to a commercial Pt/C catalyst, the Pd@PnL (n = 1-6) core-shell nanocubes showed enhancements in specific activity and durability toward the oxygen reduction reaction (ORR). Density functional theory (DFT) calculations on model (100) surfaces suggest that the enhancement in specific activity can be attributed to the weakening of OH binding through ligand and strain effects, which, in turn, increases the rate of OH hydrogenation. A volcano-type relationship between the ORR specific activity and the number of Pt atomic layers was derived, in good agreement with the experimental results. Both theoretical and experimental studies indicate that the ORR specific activity was maximized for the catalysts based on Pd@Pt2-3L nanocubes. Because of the reduction in Pt content used and the enhancement in specific activity, the Pd@Pt1L nanocubes showed a Pt mass activity with almost three-fold enhancement relative to the Pt/C catalyst.

  15. Engineered inorganic core/shell nanoparticles

    International Nuclear Information System (INIS)

    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

  16. Elastic Platonic Shells

    OpenAIRE

    Yong, Ee; Nelson, David R.; Mahadevan, Lakshminarayanan

    2013-01-01

    On microscopic scales, the crystallinity of flexible tethered or cross-linked membranes determines their mechanical response. We show that by controlling the type, number, and distribution of defects on a spherical elastic shell, it is possible to direct the morphology of these structures. Our numerical simulations show that by deflating a crystalline shell with defects, we can create elastic shell analogs of the classical platonic solids. These morphologies arise via a sharp buckling transit...

  17. Chemical effects correlated to nitrogen content of iron nitride films observed in the Fe L-shell X-rays induced by 5-keV electrons

    Energy Technology Data Exchange (ETDEWEB)

    Hinrichs, R., E-mail: ruth.hinrichs@ufrgs.br [Instituto de Geociências, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS (Brazil); Bertol, A.P.L. [Instituto de Física, UFRGS, Porto Alegre, RS (Brazil); Jacobsen, S.D. [Pós-graduação em Ciência dos Materiais, UFRGS, Porto Alegre, RS (Brazil); Castellano, G. [Facultad de Matemática, Astronomía y Física, Universidad Nacional de Córdoba (Argentina); Instituto Enrique Gaviola, CONICET (Argentina); Vasconcellos, M.A.Z. [Instituto de Física, UFRGS, Porto Alegre, RS (Brazil)

    2014-01-01

    Iron nitride thin films, produced by reactive magnetron sputtering, were characterized with grazing incidence X-ray diffraction, X-ray reflectometry, Rutherford backscattering spectrometry (RBS) and conversion electron Mössbauer spectroscopy. Their characteristic L-X-rays spectra, obtained with an electron microprobe analyzer equipped with a wavelength dispersive spectrometer, were compared to the spectrum of an iron standard. The spectra from the nitrides presented several chemical effects: change in the relative peak areas and shifts of the positions of the Lα{sub 1,2} and the Lβ{sub 1} peaks (chemical shift). The change in relative peak areas, namely the ratio between the Lβ{sub 1} and the Lα{sub 1,2} peaks, correlated well with the nitrogen content measured with RBS.

  18. Shell-like structures

    CERN Document Server

    Altenbach, Holm

    2011-01-01

    In this volume, scientists and researchers from industry discuss the new trends in simulation and computing shell-like structures. The focus is put on the following problems: new theories (based on two-dimensional field equations but describing non-classical effects), new constitutive equations (for materials like sandwiches, foams, etc. and which can be combined with the two-dimensional shell equations), complex structures (folded, branching and/or self intersecting shell structures, etc.) and shell-like structures on different scales (for example: nano-tubes) or very thin structures (similar

  19. Fisher Information and Atomic Structure

    CERN Document Server

    Chatzisavvas, K Ch; Panos, C P; Moustakidis, Ch C

    2013-01-01

    We present a comparative study of several information and statistical complexity measures in order to examine a possible correlation with certain experimental properties of atomic structure. Comparisons are also carryed out quantitatively using Pearson correlation coefficient. In particular, we show that Fisher information in momentum space is very sensitive to shell effects, and is directly associated with some of the most characteristic atomic properties, such as atomic radius, ionization energy, electronegativity, and atomic dipole polarizability. Finally we present a relation that emerges between Fisher information and the second moment of the probability distribution in momentum space i.e. an energy functional of interest in (e,2e) experiments.

  20. Inner-shell vacancy production and multiple ionization effects in 0.1-1.75 MeV/u Mn, Fe, Co, Ni, Cu + Au, Bi collisions

    International Nuclear Information System (INIS)

    Vacancy production in 0.1-1.75 MeV/u Mn, Fe, Co, Ni, Cu + Au, Bi collisions has been studied by measuring integral inner-shell ionization cross sections and average outer-shell ionization probabilities at the Van de Graaff tandem accelerator of NIPNE, Bucharest. X-ray spectra induced by ion beams of Mn, Fe, Co, Ni and Cu impinging on solid-foil targets of Au and Bi of 100 μg/cm2 thickness have been measured. The average multiple ionization probabilities of the outer-shells were obtained by measuring the yield and energy shifts of the X-rays and compared with calculations in the independent electron approximation. We report here total ionization cross sections for the K-shell of the projectile and Li subshells (i=1,2,3) of the target as well as vacancy sharing probabilities corrected for the effect of multiple ionization. Some specific effects for these heavy collision systems in the K-L level matching region or due to the high charge state of the ion inside the solid target can be observed. These result in high inner-shell ionization cross sections and strong perturbation of the atomic shells of both collision partners. The experimental results are discussed in terms of simple model calculations. (authors)

  1. Electronic states in the presence of the inner-shell hole studied by the method of DV-Xα

    Science.gov (United States)

    Yoshihiro, Ohmura; Takashi, Ikeda; Hirohide, Nakamatsu; Takeshi, Mukoyama

    1994-04-01

    The molecular orbital theory by the method of DV-Xα is applied to investigate electronic states of electrons in the presence of the inner-shell hole. The hole is assumed to be at the center of the cluster which is composed of nine ions in the bcc structure. Using the present model, the hole potential born by missing an outermost inner-shell hole is found not to be atomic but extended to the cluster size. The result is applied to investigate the anomalous edge of absorption spectra and the related problem of heavy alkali metals with the inner-shell hole in the final state. Phase shifts for l = 2 and l = 3 of wavefunctions of conduction electrons due to the presence of the inner-shell hole in the final state are found to be negative. For Cs, we could not obtain phase shifts that are consistent with both the results of experiments on X-ray absorption and XPS.

  2. Thin shell model revisited

    CERN Document Server

    Gao, Sijie

    2014-01-01

    We reconsider some fundamental problems of the thin shell model. First, we point out that the "cut and paste" construction does not guarantee a well-defined manifold because there is no overlap of coordinates across the shell. When one requires that the spacetime metric across the thin shell is continuous, it also provides a way to specify the tangent space and the manifold. Other authors have shown that this specification leads to the conservation laws when shells collide. On the other hand, the well-known areal radius $r$ seems to be a perfect coordinate covering all regions of a spherically symmetric spacetime. However, we show by simple but rigorous arguments that $r$ fails to be a coordinate covering a neighborhood of the thin shell if the metric across the shell is continuous. When two spherical shells collide and merge into one, we show that it is possible that $r$ remains to be a good coordinate and the conservation laws hold. To make this happen, different spacetime regions divided by the shells must...

  3. Arithmetic aspects of atomic structures

    International Nuclear Information System (INIS)

    The purpose of this presentation is to give an updated account of some on-going work related to the theory of large atoms in the context of large-Z asymptotics, which began over the last decade or so. The goal of that work is to produce a refined version of the Thomas-Fermi theory that accounts for observed physical features such as electronic orbitals or an atomic shell structure. This presents similarities with issues in quantum chaos. (orig.)

  4. A green sorbent of esterified egg-shell membrane for highly selective uptake of arsenate and speciation of inorganic arsenic.

    Science.gov (United States)

    Chen, Ming-Li; Gu, Cui-Bo; Yang, Ting; Sun, Yan; Wang, Jian-Hua

    2013-11-15

    Egg-shell membrane (ESM) is a promising adsorbent for heavy metal uptake. However, carboxylic groups on ESM surface barrier arsenic adsorption. Herein, ESM is modified by esterification and the methyl esterified egg-shell membrane (MESM) possesses positive charge within pH 1-9. As a novel green sorbent material, MESM exhibits 200-fold improvement on sorption capacity of arsenate with respect to bare ESM. It presents an ultra-high selectivity of 256:1 toward arsenate against arsenite. At pH 6, 100% sorption efficiency is achieved for 2 μg L(-1) As(V) by 10 mg MESM, while virtually no adsorption of As(III) is observed. This provides great potential for selective sorption of arsenate in the presence of arsenite. By loading 4.0 mL sample within 0.05-5.00 μg L(-1) As(V) followed by elution with 300 μL HCl (1.5 mol L(-1)), a detection limit of 15 ng L(-1) is obtained along with a RSD of 3.5% at 0.5 μg L(-1). Total inorganic arsenic is achieved by converting As(III) to As(V) and following the same sorption process. This procedure is applied for arsenate determination and inorganic arsenic speciation in Hijiki and water samples. The results are confirmed by graphite furnace atomic absorption spectrometry and spiking recovery. PMID:24148462

  5. Synthesis and Characterization of Monodisperse Metallodielectric SiO2@Pt@SiO2 Core-Shell-Shell Particles.

    Science.gov (United States)

    Petrov, Alexey; Lehmann, Hauke; Finsel, Maik; Klinke, Christian; Weller, Horst; Vossmeyer, Tobias

    2016-01-26

    Metallodielectric nanostructured core-shell-shell particles are particularly desirable for enabling novel types of optical components, including narrow-band absorbers, narrow-band photodetectors, and thermal emitters, as well as new types of sensors and catalysts. Here, we present a facile approach for the preparation of submicron SiO2@Pt@SiO2 core-shell-shell particles. As shown by transmission and scanning electron microscopy, the first steps of this approach allow for the deposition of closed and almost perfectly smooth platinum shells onto silica cores via a seeded growth mechanism. By choosing appropriate conditions, the shell thickness could be adjusted precisely, ranging from ∼3 to ∼32 nm. As determined by X-ray diffraction, the crystalline domain sizes of the polycrystalline metal shells were ∼4 nm, regardless of the shell thickness. The platinum content of the particles was determined by atomic absorption spectroscopy and for thin shells consistent with a dense metal layer of the TEM-measured thickness. In addition, we show that the roughness of the platinum shell strongly depends on the storage time of the gold seeds used to initiate reductive platinum deposition. Further, using polyvinylpyrrolidone as adhesion layer, it was possible to coat the metallic shells with very homogeneous and smooth insulating silica shells of well-controlled thicknesses between ∼2 and ∼43 nm. After depositing the particles onto silicon substrates equipped with interdigitated electrode structures, the metallic character of the SiO2@Pt particles and the insulating character of the SiO2 shells of the SiO2@Pt@SiO2 particles were successfully demonstrated by charge transport measurements at variable temperatures. PMID:26731341

  6. Conversion probabilities of low-energy (ℎω≤3 keV) nuclear transitions in the electron shells of free atoms. Article translated from Journal Yadernye Konstanty (Nuclear Constants). Series: Nuclear Constants, Issue No. 1, 1987

    International Nuclear Information System (INIS)

    Conversion of some low-energy transitions (ℎω≤3 keV) in the nuclei 90Nb, 99Tc, 103Ru, 110Ag, 140Pr, 142Pr, 153Gd, 159Gd, 160Tb, 165Tm, 171Lu, 173W, 188Re, 193Pt, 201Hg, 205Pb, 236Pa and 250Bk are investigated for the case of an isolated atom. The conversion transition probabilities are calculated using the electron wave functions, obtained through numerical integration of the Dirac equations in the atomic field within the framework of the Hartree-Fock-Slater method. The calculation is carried out for the normal configuration of the valence band of the aforementioned atoms. The calculation results are tabulated in this paper. (author)

  7. New polymer target-shell properties and characterizations

    International Nuclear Information System (INIS)

    A method for characterizing ICF target shells is presented, based on measurement of the gas released from a single shell into a small volume. It utilizes cryogenic permeation systems developed in connection with our work on ICF targets containing nuclear spin-polarized deuterium. Permeation rates for polystyrene and parylene-coated-polystyrene shells are measured at temperatures from 350K down to 180K. Burst or implosion pressure can be determined over a full temperature range down to 20K. Shell temperature is calculated from its gas leakage rate, calibrated by permeation measurements over the temperature range. Lag of shell temperature compared with sample-chamber temperature during warming of the latter is attributed to the weakness of the thermal link provided by both radiative heat transfer and free molecular conduction with small accommodation coefficients for helium and deuterium gas at the structure to which the shell is conductively linked, or at the surface of a conductively isolated shell. Quantification of this lag can provide a measure of atomic scale roughness of the shell outer surface. Also presented are reversible pre-rupture leakage phenomena for polystyrene and parylene-coated-polystyrene shells

  8. Composite shells with interlaminar imperfections

    OpenAIRE

    Wozniak, Czeslaw; Wozniak, Margaret

    1993-01-01

    In this contribution the effect of interlaminar initial imperfections on a composite shell behavior is investigated. The constitutive equations for shells with initial interlaminar bonding imperfections are obtained.

  9. K- and L-edge X-ray absorption spectrum calculations of closed-shell carbon, silicon, germanium, and sulfur compounds using damped four-component density functional response theory.

    Science.gov (United States)

    Fransson, Thomas; Burdakova, Daria; Norman, Patrick

    2016-05-21

    X-ray absorption spectra of carbon, silicon, germanium, and sulfur compounds have been investigated by means of damped four-component density functional response theory. It is demonstrated that a reliable description of relativistic effects is obtained at both K- and L-edges. Notably, an excellent agreement with experimental results is obtained for L2,3-spectra-with spin-orbit effects well accounted for-also in cases when the experimental intensity ratio deviates from the statistical one of 2 : 1. The theoretical results are consistent with calculations using standard response theory as well as recently reported real-time propagation methods in time-dependent density functional theory, and the virtues of different approaches are discussed. As compared to silane and silicon tetrachloride, an anomalous error in the absolute energy is reported for the L2,3-spectrum of silicon tetrafluoride, amounting to an additional spectral shift of ∼1 eV. This anomaly is also observed for other exchange-correlation functionals, but it is seen neither at other silicon edges nor at the carbon K-edge of fluorine derivatives of ethene. Considering the series of molecules SiH4-XFX with X = 1, 2, 3, 4, a gradual divergence from interpolated experimental ionization potentials is observed at the level of Kohn-Sham density functional theory (DFT), and to a smaller extent with the use of Hartree-Fock. This anomalous error is thus attributed partly to difficulties in correctly emulating the electronic structure effects imposed by the very electronegative fluorines, and partly due to inconsistencies in the spurious electron self-repulsion in DFT. Substitution with one, or possibly two, fluorine atoms is estimated to yield small enough errors to allow for reliable interpretations and predictions of L2,3-spectra of more complex and extended silicon-based systems. PMID:27136720

  10. Study of K, L vacancies production mechanisms by X spectrometry in the interaction induced by a few MeV/A charged particles

    International Nuclear Information System (INIS)

    The analysis of different mechanisms producing electronic inner shell vacancies in ion atom collisions at a few MeV/A charged is presented. The mutual influence of nuclear and atomic excitation in the ionization probability has been discussed. The 106Cd(p,p')106Cd reaction (Ep=10 MeV) has been particularly investigated from this point. The investigation is followed up by the description of the theoretical and experimental methods which permit the determination of the total and/or differential X rays production cross section for different interaction. The gold sub-shell L1, L2, L3 ionization probability has been studied in the Au(H+,H+)Au reaction at Ep=1 MeV. In the second part of the manuscript we investigate in detail the influence of the charge exchange process on inner shell vacancy production. The N2, Ar, Kr targets have been produced by a system jet gas and bombarded by 0.828Si14+ ions at E=125 MeV. The cross section for the capture of an electron in K shell, L shell and total charge exchange have been measured and compared to the CDW theory (Continuum Distorted Wave). In the CDW validity domain the experimental and theoretical results are a good agreement. In the collisions induced by H+, ionization is found to be the main excitation process. On the contrary, in collisions induced by 28Si14+ charge exchange is dominant compared to ionization

  11. New interpretations, anomalous degeneracies, and SO(4) theory for electron correlation in first-row atoms and multiply-excited states

    International Nuclear Information System (INIS)

    Geometrical and computational interpretations are offered for configuration-mixed α (1s/sup d/2s22p/sup m/) + β (1s/sup d/2p/sup m/+2) (where d = 0 or 2) valence states based on new profiles of L-shell mixing coefficients, correlation energies, and pair-function angular distributions for both ground and excited states. When viewed for species having the same degree of ionization Z-N, the profiles constructed for the internal and semi-internal ''nondynamical'' correlation energies computed by Sinanoglu's ''non-closed-shell many-electron theory'' are found to display a striking, approximate particle-hole symmetry with respect to total L-shell occupancy. Near-degeneracy-type correlation energy for 3P and 1D levels of C-like atoms becomes exactly degenerate when the same radial functions are used for both states. The mixing structure for all L-shell states is described accurately by an N-electron operator Λ (N) = Σ/sub i/2 with single-particle SO(4) generators A/sub i/ like the Runge-Lenz vector. Λ (N) represents an approximate ''correlation invariant'' for L-shell mixings

  12. Photonic, Electronic and Atomic Collisions

    Science.gov (United States)

    Fainstein, Pablo D.; Lima, Marco Aurelio P.; Miraglia, Jorge E.; Montenegro, Eduardo C.; Rivarola, Roberto D.

    2006-11-01

    . Absolute total cross sections for electron-CH[symbol] scattering at intermediate energies / M. C. A. Lopes ... [et al.]. Electron-CO[symbol] scattering in a cluster environment / I. I. Fabrikant. Isomer effect in electron collisions with small hydrocarbons / M. H. F. Bettega ... [et al.]. Low energy electron interactions with bio-molecules / B. P. Marinković ... [et al.]. Narrow resonances in dissociative electron attachment and vibrational excitation in H[symbol] / M. Číček. (e, 2e) experiments with randomly oriented and fixed-in-space hydrogen molecules / M. Takahashi. Initial and final state correlation effects in (e, 3e) processes / G. Gasaneo, S. Otranto and K. V. Rodríguez. An (e, 2˙e) experiment for simultaneous ionization-excitation of helium to the He[symbol](2p)[symbol]P states by electron impact / A. Dorn ... [et al.] -- Collisions involving exotic particles. Antihydrogen in the laboratory / M. Charlton. Atomic collisions involving positrons / H. R. J. Walters and C. Starret. Ionization and positronium formation in noble gases / J. P. Marler, J. P. Sullivan and C. M. Surko. Study of inner-shell ionization by low-energy positron impact / Y. Nagashima ... [et al.]. Positron-atom bound states and interactions / M. W. J. Bromley. Extraction of ultra-slow antiproton beams for single collision experiments / H. A. Torii ... [et al.]. Positronium formation from valence and inner shells in noble gases / L. J. M. Dunlop and G. F. Gribakin. Molecular effects in neutrino mass measurements / N. Doss ... [et al.] -- Collisions involving heavy projectiles. Probing the solar wind with cometary X-ray and far-ultraviolet emission / R. Hoekstra ... [et al.]. Production of O[symbol] + neutrals from the collision of C[symbol] with water / H. Luna ... [et al.]. Vector correlation of fragment ions produced by collision of Ar[symbol] with dimethyldisulfide / T. Matsuoka ... [et al.]. Slow multiply charged ion-molecule collision dynamics studied through a multi

  13. Snap-Through Buckling Problem of Spherical Shell Structure

    Directory of Open Access Journals (Sweden)

    Sumirin

    2015-01-01

    Full Text Available This paper presents results of a numerical study on the nonlinear behavior of shells undergoing snap-through instability. This research investigates the problem of snap-through buckling of spherical shells applying nonlinear finite element analysis utilizing ANSYS Program. The shell structure was modeled by axisymmetric thin shell of finite elements. Shells undergoing snap-through buckling meet with significant geometric change of their physical configuration, i.e. enduring large deflections during their deformation process. Therefore snap-through buckling of shells basically is a nonlinear problem. Nonlinear numerical operations need to be applied in their analysis. The problem was solved by a scheme of incremental iterative procedures applying Newton-Raphson method in combination with the known line search as well as the arc- length methods. The effects of thickness and depth variation of the shell is taken care of by considering their geometrical parameter l. The results of this study reveal that spherical shell structures subjected to pressure loading experience snap-through instability for values of l≥2.15. A form of ‘turn-back’ of the load-displacement curve took place at load levels prior to the achievement of the critical point. This phenomenon was observed for values of l=5.0 to l=7.0.

  14. Nuclear shell theory

    CERN Document Server

    de-Shalit, Amos; Massey, H S W

    1963-01-01

    Nuclear Shell Theory is a comprehensive textbook dealing with modern methods of the nuclear shell model. This book deals with the mathematical theory of a system of Fermions in a central field. It is divided into three parts. Part I discusses the single particle shell model. The second part focuses on the tensor algebra, two-particle systems. The last part covers three or more particle systems. Chapters on wave functions in a central field, tensor fields, and the m-Scheme are also presented. Physicists, graduate students, and teachers of nuclear physics will find the book invaluable.

  15. The splitting of atomic orbitals with a common principal quantum number revisited: np vs. ns.

    Science.gov (United States)

    Katriel, Jacob

    2012-04-14

    Atomic orbitals with a common principal quantum number are degenerate, as in the hydrogen atom, in the absence of interelectronic repulsion. Due to the virial theorem, electrons in such orbitals experience equal nuclear attractions. Comparing states of several-electron atoms that differ by the occupation of orbitals with a common principal quantum number, such as 1s(2) 2s vs. 1s(2) 2p, we find that although the difference in energies, ΔE, is due to the interelectronic repulsion term in the Hamiltonian, the difference between the interelectronic repulsions, ΔC, makes a smaller contribution to ΔE than the corresponding difference between the nuclear attractions, ΔL. Analysis of spectroscopic data for atomic isoelectronic sequences allows an extensive investigation of these issues. In the low nuclear charge range of pertinent isoelectronic sequences, i.e., for neutral atoms and mildly positively charged ions, it is found that ΔC actually reverses its sign. About 96% of the nuclear attraction difference between the 6p (2)P and the 6s (2)S states of the Cs atom is cancelled by the corresponding interelectronic repulsion difference. From the monotonic increase of ΔE with Z it follows (via the Hellmann-Feynman theorem) that ΔL > 0. Upon increasing the nuclear charge along an atomic isoelectronic sequence with a single electron outside a closed shell from Z(c), the critical charge below which the outmost electron is not bound, to infinity, the ratio ΔC/ΔL increases monotonically from lim(Z→Z(c)(+))ΔC/ΔL=-1 to lim(Z→∞)ΔC/ΔL=1. These results should allow for a more nuanced discussion than is usually encountered of the crude electronic structure of many-electron atoms and the structure of the periodic table. PMID:22502506

  16. Existence of near-zero minima in elastic photon-atom scattering

    International Nuclear Information System (INIS)

    We consider elastic photon-atom in the vicinity of resonances, in particular the region of resonant transitions involving the K shell. We use a relativistic S-matrix code to calculate the scattering cross section. In the case of scattering from ground-states of atoms there is a near-zero minimum in the scattering cross section as the K resonance region is approached from below. For more exotic targets, such as hollow atoms (with inner shells completely vacated), the S-matrix code predicts other types of near-zero minima: for example, in the case of a hollow atom with all electrons present in the L shell (i.e. completely vacant K shell) there is a near-zero minimum in the cross section just above the position of the downward L to K bound-bound transition. Understanding near-zeroes in scattering is potentially important, given the possibility of using synchrotron radiation in medical applications. The cross section associated with a high-Z trace element would be very sensitive to the frequency of the radiation in the vicinity of a real near-zero, while the cross section associated with surrounding bone and tissue would be comparatively insensitive. However the present S-matrix code performs an averaging over magnetic substates, weighted over the number of electrons actually present in each subshell, at the level of the scattering amplitude. This method is exact only for closed shells, and is approximate in the case of partially-filled subshells. A more proper approach is to average the cross sections for all possible magnetic substate occupations. We compare results using these two approaches and consider the consequences for the existence of near-zero minima in the cross section. The near-zero seen below the resonance region for scattering from ground-state atoms survives in the more proper treatment. However other types of near-zeros, such as those seen in the case of hollow atoms, can be spurious, depending on the details of the configuration. (author)

  17. Al K-shell x-ray production cross section induced by proton and highly charged heavy ions

    International Nuclear Information System (INIS)

    Al K-shell x-ray production cross sections induced by 50–250 keV protons and 1–3 MeV Ar11+ ions were measured. It was found that 3–4 L-shell electrons of the Al atom were multiply ionized by Ar11+ ion impact. The x-ray production cross sections were deduced from the experimental yield data and compared with binary encounter approximation (BEA), plane wave Born approximation and energy-loss Coulomb-repulsion perturbed-stationary-state relativistic (ECPSSR) theoretical predictions. For proton impact, the ECPSSR theory gave an accurate prediction of the experimental result. However, taking into account the multiple-ionization effect on fluorescence yield, the BEA model presented better agreement with the cross section data produced by Ar11+ ions. (paper)

  18. C-Shell Cookbook

    Science.gov (United States)

    Currie, Malcolm J.

    This cookbook describes the fundamentals of writing scripts using the UNIX C shell. It shows how to combine Starlink and private applications with shell commands and constructs to create powerful and time-saving tools for performing repetitive jobs, creating data-processing pipelines, and encapsulating useful recipes. The cookbook aims to give practical and reassuring examples to at least get you started without having to consult a UNIX manual. However, it does not offer a comprehensive description of C-shell syntax to prevent you from being overwhelmed or intimidated. The topics covered are: how to run a script, defining shell variables, prompting, arithmetic and string processing, passing information between Starlink applications, obtaining dataset attributes and FITS header information, processing multiple files and filename modification, command-line arguments and options, and loops. There is also a glossary.

  19. Continuum Shell Model

    OpenAIRE

    Volya, Alexander; Zelevinsky, Vladimir

    2005-01-01

    The Continuum Shell Model is an old but recently revived method that traverses the boundary between nuclear many-body structure and nuclear reactions. The method is based on the non-Hermitian energy-dependent effective Hamiltonian. The formalism, interpretation of solutions and practical implementation of calculations are discussed in detail. The results of the traditional shell model are fully reproduced for bound states; resonance parameters and cross section calculations are presented for ...

  20. Dynamic Analysis of Shells

    Directory of Open Access Journals (Sweden)

    Charles R. Steele

    1995-01-01

    Full Text Available Shell structures are indispensable in virtually every industry. However, in the design, analysis, fabrication, and maintenance of such structures, there are many pitfalls leading to various forms of disaster. The experience gained by engineers over some 200 years of disasters and brushes with disaster is expressed in the extensive archival literature, national codes, and procedural documentation found in larger companies. However, the advantage of the richness in the behavior of shells is that the way is always open for innovation. In this survey, we present a broad overview of the dynamic response of shell structures. The intention is to provide an understanding of the basic themes behind the detailed codes and stimulate, not restrict, positive innovation. Such understanding is also crucial for the correct computation of shell structures by any computer code. The physics dictates that the thin shell structure offers a challenge for analysis and computation. Shell response can be generally categorized by states of extension, inextensional bending, edge bending, and edge transverse shear. Simple estimates for the magnitudes of stress, deformation, and resonance in the extensional and inextensional states are provided by ring response. Several shell examples demonstrate the different states and combinations. For excitation frequency above the extensional resonance, such as in impact and acoustic excitation, a fine mesh is needed over the entire shell surface. For this range, modal and implicit methods are of limited value. The example of a sphere impacting a rigid surface shows that plastic unloading occurs continuously. Thus, there are no short cuts; the complete material behavior must be included.

  1. The Nonlinear Instability Modes of Dished Shallow Shells under Circular Line Loads

    OpenAIRE

    Liu Chang-Jiang; Zheng Zhou-Lian; Huang Cong-Bing; He Xiao-Ting; Sun Jun-Yi; Chen Shan-Lin

    2011-01-01

    This paper investigated the nonlinear stability problem of dished shallow shells under circular line loads. We derived the dimensionless governing differential equations of dished shallow shell under circular line loads according to the nonlinear theory of plates and shells and solved the governing differential equations by combing the free-parameter perturbation method (FPPM) with spline function method (SFM) to analyze the nonlinear instability modes of dished shallow shell under circular l...

  2. Shells in the Magellanic System

    OpenAIRE

    Stanimirovic, Snezana

    2006-01-01

    The Magellanic System harbors >800 expanding shells of neutral hydrogen, providing a unique opportunity for statistical investigations. Most of these shells are surprisingly young, 2--10 Myr old, and correlate poorly with young stellar populations. I summarize what we have learned about shell properties and particularly focus on the puzzling correlation between the shell radius and expansion velocity. In the framework of the standard, adiabatic model for shell evolution this tight correlation...

  3. Atomic-resolution studies of epitaxial strain release mechanisms in L a1.85S r0.15Cu O4 /L a0.67C a0.33Mn O3 superlattices

    Science.gov (United States)

    Biškup, N.; Das, S.; Gonzalez-Calbet, J. M.; Bernhard, C.; Varela, M.

    2015-05-01

    In this paper we present an atomic-resolution electron microscopy study of superlattices (SLs) where the colossal magnetoresistant manganite L a0.67C a0.33Mn O3 (LCMO) and the high critical temperature superconducting cuprate L a1.85S r0.15Cu O4 (LSCO) are combined. Although good quality epitaxial growth can be achieved, both the choice of substrate and the relatively large lattice mismatch between these materials (around 2%) have a significant impact on the system properties [Phys. C 468, 991 (2008), 10.1016/j.physc.2008.05.001; Nature (London) 394, 453 (1998), 10.1038/28810]. Our samples, grown by pulsed laser deposition, are epitaxial and exhibit high structural quality. By means of cutting-edge electron microscopy and spectroscopy techniques we still find that the epitaxial strain is accommodated by a combination of defects, such as interface steps and antiphase boundaries in the manganite. These defects result in inhomogeneous strain fields through the samples. Also, some chemical inhomogeneities are detected, up to the point that novel phases nucleate. For example, at the LCMO/LSCO interface the AB O3 -type manganite adopts a tetragonal LSCO-like structure forming localized layers that locally resemble the composition of L a2 /3C a4 /3Mn O4 . Structural distortions are detected in the cuprate as well, which may extend over lateral distances of several unit cells. Finally, we also analyze the influence of the substrate-induced strain by examining superlattices grown on two different substrates: (LaAlO3) 0.3(Sr2AlTaO6 ) 0.7 (LSAT) and LaSrAl O4 (LSAO). We observe that SLs grown on LSAT, which are nonsuperconducting, present reduced values of the c axis compared to superlattices grown on LSAO (which are fully superconducting). This finding points to the fact that the proper distance between copper planes in LSCO is essential in obtaining superconductivity in cuprates.

  4. O-shell emission of uranium in a high temperature, low density plasma

    International Nuclear Information System (INIS)

    We present models for the soft X ray emission spectra of UXXIV, UXXV, UXXX, UXXXI and UXXXII under tokamak conditions. The spectra are calculated from collisional-radiative models and cover the 60 to 200 Angstrom range. A fully relativistic parametric potential code has been used for the ab initio atomic structure calculations, and electron impact excitation rates have been computed in the distorted wave approximation. The ions considered here display a range of spectroscopic phenomena to be found in the O-shell of heavy elements, that can be compared with experimental observations. These include the configuration interaction between 5s25p65dk-15f and 5s25p55dk+1 in ions with 5s25p65dk ground configurations, represented by UXXIV (k=l); configuration interaction between 5s25pk-15d and 5s25pk+l in ions with 5s25pk ground configurations, such as UXXX (k=l); the unique system of satellite emission lines to the resonant 5s-5p transitions in UXXXII arising from highly metastable 4f135s2 levels; and the bright, isolated resonant lines associated with the closed shell UXXXI and systems

  5. Method development for the determination of iron in milligram amounts of rice plants (Oryza sativa L.) from cultivation experiments using graphite furnace atomic absorption spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Marcia M.; Vale, Maria Goreti R.; Damin, Isabel C. Ferreira [Instituto de Quimica, Universidade Federal do Rio Grande do Sul (UFRGS), Av. Bento Goncalves 9500, 91501-970, Porto Alegre RS (Brazil); Welz, Bernhard [Departamento de Quimica, Universidade Federal de Santa Catarina (UFSC), 88040-900, Florianopolis SC (Brazil); Mandaji, Marcos; Fett, Janette P. [Departamento de Botanica e Centro de Biotecnologia, Instituto de Biociencias, Universidade Federal do Rio Grande do Sul (UFRGS), Av. Bento Goncalves 9500, 91501-970, Porto Alegre RS (Brazil)

    2003-09-01

    The amount of sample that is available for analysis in laboratory plant cultivation experiments is usually very limited. Highly sensitive analytical techniques are therefore required, even for elements that are present in the plants at mg g{sup -1} concentrations, and graphite furnace atomic absorption spectrometry (GFAAS) was chosen in this work because of its micro-sampling capability, and its relatively simple operation. Four micro-methods were investigated for the determination of iron in roots and leaves of rice plants: (i) a micro-digestion with nitric and hydrochloric acids, (ii) a slurry procedure using tetramethylammonium hydroxide (TMAH) tissue solubilizer, (iii) a slurry prepared in 1.4 mol L{sup -1} nitric acid, and treated in an ultrasonic bath, and (iv) the direct analysis of solid samples. The micro-digestion was suffering from high blank values and contamination problems, so that it could not be recommended for routine purposes. The TMAH method exhibited poor precision and occasional low recoveries, particularly for real samples. Direct solid sampling analysis gave results similar to those obtained with the slurry technique with ultrasonic agitation for the determination of iron in certified reference materials with iron content up to about 100 {mu}g g{sup -1}, but was too sensitive for the investigated rice plants, which had an iron content up to several mg g{sup -1}. The slurry technique with ultrasonic treatment of the samples, suspended in dilute nitric acid, was finally adopted as the method of choice. The method was then applied for the determination of iron in the leaves and in different compartments of the roots of two rice cultivars, one sensitive to iron toxicity, an important nutritional disorder, and the other one resistant to iron toxicity. The results suggest that the higher resistance to iron toxicity of the second cultivar is due to a smaller uptake of iron from the soil, resulting in lower iron levels in all compartments of the

  6. Multi-Shell Hollow Nanogels with Responsive Shell Permeability

    Science.gov (United States)

    Schmid, Andreas J.; Dubbert, Janine; Rudov, Andrey A.; Pedersen, Jan Skov; Lindner, Peter; Karg, Matthias; Potemkin, Igor I.; Richtering, Walter

    2016-03-01

    We report on hollow shell-shell nanogels with two polymer shells that have different volume phase transition temperatures. By means of small angle neutron scattering (SANS) employing contrast variation and molecular dynamics (MD) simulations we show that hollow shell-shell nanocontainers are ideal systems for controlled drug delivery: The temperature responsive swelling of the inner shell controls the uptake and release, while the thermoresponsive swelling of the outer shell controls the size of the void and the colloidal stability. At temperatures between 32 °C < T < 42 °C, the hollow nanocontainers provide a significant void, which is even larger than the initial core size of the template, and they possess a high colloidal stability due to the steric stabilization of the swollen outer shell. Computer simulations showed, that temperature induced switching of the permeability of the inner shell allows for the encapsulation in and release of molecules from the cavity.

  7. Synergetic effect of organic cores and inorganic shells for core/shell structured composite abrasives for chemical mechanical planarization

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Yang, E-mail: cy.jpu@126.com [School of Materials Science and Engineering, Changzhou University, Changzhou, Jiangsu 213164 (China); Li, Zhina [School of Materials Science and Engineering, Changzhou University, Changzhou, Jiangsu 213164 (China); Miao, Naiming [School of Mechanical Engineering, Changzhou University, Changzhou, Jiangsu 213016 (China)

    2014-09-30

    Highlights: • The damage-free polishing mechanism of core/shell composite abrasive was explored. • The organic core is help to decrease surface roughness and mechanical damages. • The inorganic shell is in favor of improving material removal rate. • The enhanced CMP behavior is due to the synergistic effect between core and shell. - Abstract: Core/shell structured organic/inorganic composite microspheres has an important potential application in efficient and damage-free chemical mechanical planarization/polishing (CMP) as a kind of novel abrasive due to its uniform non-rigid mechanical property. However, the synergistic effect of material removal between organic cores and inorganic shells of composite abrasives is ambiguous. In this work, oxide-CMP performances of various slurries, containing polystyrene (PS) spheres, solid abrasives (SiO{sub 2} or CeO{sub 2}), mixed abrasives ((PS + SiO{sub 2}) or (PS + CeO{sub 2})), core/shell composites (PS/SiO{sub 2} or PS/CeO{sub 2}), were investigated by atomic force microscopy. Experiment results indicated that the surfaces polished by composite abrasives exhibited lower surface roughness, fewer scratches as well as lower topographical variations than those by other type of abrasives. The core/shell structure of composite abrasives plays an important role in improving CMP behavior. Moreover, the organic cores are mainly beneficial to decrease surface roughness and mechanical damages, and the inorganic shells are in favor of improving material removal rate.

  8. Synergetic effect of organic cores and inorganic shells for core/shell structured composite abrasives for chemical mechanical planarization

    International Nuclear Information System (INIS)

    Highlights: • The damage-free polishing mechanism of core/shell composite abrasive was explored. • The organic core is help to decrease surface roughness and mechanical damages. • The inorganic shell is in favor of improving material removal rate. • The enhanced CMP behavior is due to the synergistic effect between core and shell. - Abstract: Core/shell structured organic/inorganic composite microspheres has an important potential application in efficient and damage-free chemical mechanical planarization/polishing (CMP) as a kind of novel abrasive due to its uniform non-rigid mechanical property. However, the synergistic effect of material removal between organic cores and inorganic shells of composite abrasives is ambiguous. In this work, oxide-CMP performances of various slurries, containing polystyrene (PS) spheres, solid abrasives (SiO2 or CeO2), mixed abrasives ((PS + SiO2) or (PS + CeO2)), core/shell composites (PS/SiO2 or PS/CeO2), were investigated by atomic force microscopy. Experiment results indicated that the surfaces polished by composite abrasives exhibited lower surface roughness, fewer scratches as well as lower topographical variations than those by other type of abrasives. The core/shell structure of composite abrasives plays an important role in improving CMP behavior. Moreover, the organic cores are mainly beneficial to decrease surface roughness and mechanical damages, and the inorganic shells are in favor of improving material removal rate

  9. Atom Chips

    CERN Document Server

    Folman, R; Cassettari, D; Hessmo, B; Maier, T; Schmiedmayer, J; Folman, Ron; Krüger, Peter; Cassettari, Donatella; Hessmo, Björn; Maier, Thomas

    1999-01-01

    Atoms can be trapped and guided using nano-fabricated wires on surfaces, achieving the scales required by quantum information proposals. These Atom Chips form the basis for robust and widespread applications of cold atoms ranging from atom optics to fundamental questions in mesoscopic physics, and possibly quantum information systems.

  10. Dynamical polarizability of atoms

    International Nuclear Information System (INIS)

    The frequency-dependent polarizability of a closed-shell atom is considered in an RPA type approximation. This is usually done using many-body perturbation theory but can also be recast into the form of equations for the density oscillations as previously shown by the authors. The latter approach is known to lead to a non-hermitian problem because of the structure of the interaction kernel. This note shows that this is also true if using the reaction matrix method. The main result is to derive the expression for the polarizability function taking into account the non-hermitian nature of the problem. (author)

  11. Formulation of the Strutinsky's averaging method in Hartree-Fock-Roothaan framework: Open Shell Systems

    International Nuclear Information System (INIS)

    Strutinsky's shell-correction method is applied in the framework of the Hartree-Fock method developed by Roothaan (HFR) in the atoms and ions with an open shell. Applying the Strutinsky energy averaging to the density matrix define a self-consistently average HFR system as a solution of the variational problem. We derive the explicit expressions for the shell corrections. 3 refs. (author)

  12. Photo-induced valence change of the sulfur atom in an L-cysteine thin film grown on a silver metal substrate in a saliva-emulated aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Tsujibayashi, Toru [Department of Physics, Osaka Dental University, 8-1 Kuzuha-hanazono, Hirakata, Osaka 573-1121 (Japan); Azuma, Junpei; Yamamoto, Isamu; Takahashi, Kazutoshi; Kamada, Masao [Synchrotron Light Application Center, Saga University, 1 Honjo, Saga, Saga 840-8502 (Japan)

    2015-04-27

    A thin film of L-cysteine (HSCH{sub 2}CH(NH{sub 2})COOH) is grown on a silver substrate in saliva-emulated aqueous solution. X-ray photoemission spectroscopic measurements have revealed that the sulfur atom shows valence change under IR laser irradiation at 825 nm. The valence change maintains for about a minute at room temperature and more than an hour between 110 and 250 K after stopping the laser irradiation. It is not observed at all at temperatures lower than 110 K. This temperature-dependent behavior indicates that the photo-excited electronic change should be accompanied by a conformational change in the L-cysteine molecule. It is strongly suggested that the reversible valence change of the sulfur atom is applicable to a memory used around room temperature.

  13. Photo-induced valence change of the sulfur atom in an L-cysteine thin film grown on a silver metal substrate in a saliva-emulated aqueous solution

    International Nuclear Information System (INIS)

    A thin film of L-cysteine (HSCH2CH(NH2)COOH) is grown on a silver substrate in saliva-emulated aqueous solution. X-ray photoemission spectroscopic measurements have revealed that the sulfur atom shows valence change under IR laser irradiation at 825 nm. The valence change maintains for about a minute at room temperature and more than an hour between 110 and 250 K after stopping the laser irradiation. It is not observed at all at temperatures lower than 110 K. This temperature-dependent behavior indicates that the photo-excited electronic change should be accompanied by a conformational change in the L-cysteine molecule. It is strongly suggested that the reversible valence change of the sulfur atom is applicable to a memory used around room temperature

  14. Inner-shell couplings in transiently formed superheavy quasimolecules

    Energy Technology Data Exchange (ETDEWEB)

    Verma, P [Kalindi College, University of Delhi, New Delhi 110008 (India); Mokler, P H [Max-Planck-Institut fuer Kernphysik, 69117 Heidelberg (Germany); Braeuning-Demian, A; Kozhuharov, C; Braeuning, H; Bosch, F; Hagmann, S; Liesen, D [GSI Helmholzzentrum fuer Schwerionenforschung, 64291 Darmstadt (Germany); Anton, J; Fricke, B [Universitaet Kassel, 34109 Kassel (Germany); Stachura, Z [Institute for Nuclear Physics, Cracow PL 31342 (Poland); Wahab, M A, E-mail: p.verma.du@gmail.com [Jamia Millia Islamia, Jamia Nagar, New Delhi 110025 (India)

    2011-06-15

    The inner-shell couplings for U{sup q+}-ions (73{<=}q{<=}91) moving moderately slow at {approx}69 MeV u{sup -1} and bombarding thin Au targets have been investigated. Having established the definite survival probability of incoming projectile K vacancies in these targets in an earlier publication, the transfer of these vacancies to the target K-shell due to inner-shell couplings has been studied. As the system is in the quasiadiabatic collision regime for the K-shell of collision partners, advanced SCF-DFS (self-consistent field-Dirac-Fock-Slater) multielectron level diagrams have been used for interpretation. Using a simple model, the L-K shell coupling interaction distance has been estimated and compared with level diagram calculations.

  15. Stabilization of the resistive shell mode in tokamaks

    International Nuclear Information System (INIS)

    The stability of current-driven external-kink modes is investigated in a tokamak plasma surrounded by an external shell of finite electrical conductivity. According to conventional theory, the ideal mode can be stabilized by placing the shell sufficiently close to the plasma, but the non-rotating ''resistive shell mode,'' which grows on the characteristic L/R time of the shell, always persists. It is demonstrated, using both analytic and numerical techniques, that a combination of strong edge plasma rotation and dissipation somewhere inside the plasma is capable of stabilizing the resistive shell mode. This stabilization mechanism does not necessarily depend on toroidicity or presence of resonant surfaces inside the plasma

  16. Atom Probe Tomographic Mapping Directly Reveals the Atomic Distribution of Phosphorus in Resin Embedded Ferritin

    Science.gov (United States)

    Perea, Daniel E.; Liu, Jia; Bartrand, Jonah; Dicken, Quinten; Thevuthasan, S. Theva; Browning, Nigel D.; Evans, James E.

    2016-02-01

    Here we report the atomic-scale analysis of biological interfaces within the ferritin protein using atom probe tomography that is facilitated by an advanced specimen preparation approach. Embedding ferritin in an organic polymer resin lacking nitrogen provided chemical contrast to visualise atomic distributions and distinguish the inorganic-organic interface of the ferrihydrite mineral core and protein shell, as well as the organic-organic interface between the ferritin protein shell and embedding resin. In addition, we definitively show the atomic-scale distribution of phosphorus as being at the surface of the ferrihydrite mineral with the distribution of sodium mapped within the protein shell environment with an enhanced distribution at the mineral/protein interface. The sample preparation method is robust and can be directly extended to further enhance the study of biological, organic and inorganic nanomaterials relevant to health, energy or the environment.

  17. An efficient, selective collisional ejection mechanism for inner-shell population inversion in laser-driven plasmas

    International Nuclear Information System (INIS)

    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 248 nm ultraviolet radiation (McPherson A et al 1994 Nature 370 631-4). 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 Xe27+(2p53d10) and Xe28+(2p53d9) 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 ∼λ-6 pump-laser wavelength dependence of the efficiency of inner-shell (2p) vacancy production in Xe clusters excited in underdense plasmas (Kondo K et al 1997 J. Phys. B: At. Mol. Opt. Phys. 30 2707-16). (author)

  18. A study of K shell X-ray intensity ratios of NixCr1−x alloys in external magnetic field and determination of effective atomic numbers of these alloys

    International Nuclear Information System (INIS)

    In this study, the effect of external magnetic field on the Kβ/Kα X-ray intensity ratios of various alloy compositions of Ni–Cr transition metal alloys has been investigated. The Kα and Kβ emission spectra of Ni, Cr and NixCr1−x (x=0.40; 0.50; 0.60; 0.80) alloys were measured by using a Si (Li) solid-state detector. Kβ/Kα X-ray intensity ratios of Ni, Cr and NixCr1−x alloys without magnetic field and in 0.5 and 1 T external magnetic field have been measured following excitation by 59.5 keV γ-rays from a 200 mCi241Am radioisotope point source. When the experimental data obtained in external magnetic field have been compared with data without external magnetic field, deviations have been observed in Kβ/Kα X-ray intensity ratios for Ni and Cr in different alloy compositions. Thus, results of these measurements have shown that Kβ/Kα X-ray intensity ratios of Ni and Cr in NixCr1−x alloys are dependent on the external magnetic field. Also the total mass attenuation coefficients for pure 3d transition metals and their alloys at different compositions were measured and theoretically estimated using mixture rule for selected photon energy. Later on, total atomic and electronic cross-sections and effective atomic number for alloys are determined experimentally and theoretically using these mass attenuation coefficients. When these parameters are examined depending on the alloy compositions, thereof have been found to vary with the alloy composition. - Highlights: • The external magnetic field effect on the K X-ray intensity ratios of some Ni–Cr alloys is investigated. • The changes on Kβ/Kα X-ray intensity ratios of the alloys are observed depending on concentrations of the elements constituting the alloys and external magnetic field intensity. • The Ze is depending on the concentrations of the elements constituting the alloys

  19. Search for next neutron shell closure in superheavy region

    International Nuclear Information System (INIS)

    The stability of the heaviest and superheavy elements have been a long-standing fundamental question in nuclear science. Theoretically, the mere existence of the heaviest elements with Z > 104 is entirely due to the quantal shell effects. If the heaviest nuclei were governed by the classical liquid drop model, they would fission immediately from their ground states due to the large electric charge. However in the mid 1960s, with the invention of the shell-correction method, it was realized that atomic numbers could exist due to the strong shell stabilization. Most of the heaviest elements found recently are believed to be well deformed. Since in the region of superheavy elements the single particle level density is relatively large, small shifts in position of single particle gaps and be crucial for determining the shell stability of the nucleus

  20. Metal shell technology based upon hollow jet instability

    International Nuclear Information System (INIS)

    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

  1. MUTA calculations of a laser-produced Mg hollow atom spectrum

    International Nuclear Information System (INIS)

    A study is made of the spectra produced from a short-wavelength long-pulse (nanosecond) laser incident on a Mg plasma. A very complex experimental spectrum is analyzed in detail by comparison with large-scale atomic kinetics calculations using the recently developed mixed-UTA (MUTA) model. We find that the experimental spectrum appears to contain lines from many inner-shell transitions from ions ranging from neutral Mg to Li-like Mg. Lines from transitions such as 1s-3l, 1s-4l, and from hollow atoms (where in this context hollow atoms refer to ions with an empty 1s shell) are observed. The inclusion of very small fractions of hot electrons is demonstrated to make significant differences to the spectra. Although it is found that the calculations do not match perfectly the experimental spectra, reasonable agreement between the experiment and the theory can be obtained if temperature and density gradients are assumed present in the experimental conditions

  2. Investigation of physical vapor deposition techniques of conformal shell coating for core/shell structures by Monte Carlo simulations

    International Nuclear Information System (INIS)

    Vertically aligned core/shell nanowire (nanorod) arrays are favorable candidates in many nano-scale devices such as solar cells, detectors, and integrated circuits. The quality of the shell coating around nanowire arrays is as crucial as the quality of the nanowires in device applications. For this reason, we worked on different physical vapor deposition (PVD) techniques and conducted Monte Carlo simulations to estimate the best deposition technique for a conformal shell coating. Our results show that a small angle (≤ 45°) between incoming flux of particles and the substrate surface normal is necessary for PVD techniques with a directional incoming flux (e.g. thermal or e-beam evaporation) for a reasonable conformal coating. On the other hand, PVD techniques with an angular flux distribution (e.g. sputtering) can provide a fairly conformal shell coating around nanowire arrays without a need of small angle deposition. We also studied the shape effect of the arrays on the conformality of the coating and discovered that arrays of the tapered-top nanorods and the pyramids can be coated with a more conformal and thicker coating compared to the coating on the arrays of flat-top nanowires due to their larger openings in between structures. Our results indicate that conventional PVD techniques, which offer low cost and large scale thin film fabrication, can be utilized for highly conformal and uniform shell coating formation in core/shell nanowire device applications. - Highlights: • We examined the shell coating growth in core/shell nanostructures. • We investigated the effect of physical vapor deposition method on the conformality of the shell. • We used Monte Carlo simulations to simulate the shell growth on nanowire templates. • Angular atomic flux (i.e., sputtering at high pressure) leads to conformal and uniform coatings. • A small angle (< 45°) to the directional flux needs to be introduced for conformal coatings

  3. Investigation of physical vapor deposition techniques of conformal shell coating for core/shell structures by Monte Carlo simulations

    Energy Technology Data Exchange (ETDEWEB)

    Cansizoglu, H., E-mail: hxis@ualr.edu; Yurukcu, M.; Cansizoglu, M.F.; Karabacak, T.

    2015-05-29

    Vertically aligned core/shell nanowire (nanorod) arrays are favorable candidates in many nano-scale devices such as solar cells, detectors, and integrated circuits. The quality of the shell coating around nanowire arrays is as crucial as the quality of the nanowires in device applications. For this reason, we worked on different physical vapor deposition (PVD) techniques and conducted Monte Carlo simulations to estimate the best deposition technique for a conformal shell coating. Our results show that a small angle (≤ 45°) between incoming flux of particles and the substrate surface normal is necessary for PVD techniques with a directional incoming flux (e.g. thermal or e-beam evaporation) for a reasonable conformal coating. On the other hand, PVD techniques with an angular flux distribution (e.g. sputtering) can provide a fairly conformal shell coating around nanowire arrays without a need of small angle deposition. We also studied the shape effect of the arrays on the conformality of the coating and discovered that arrays of the tapered-top nanorods and the pyramids can be coated with a more conformal and thicker coating compared to the coating on the arrays of flat-top nanowires due to their larger openings in between structures. Our results indicate that conventional PVD techniques, which offer low cost and large scale thin film fabrication, can be utilized for highly conformal and uniform shell coating formation in core/shell nanowire device applications. - Highlights: • We examined the shell coating growth in core/shell nanostructures. • We investigated the effect of physical vapor deposition method on the conformality of the shell. • We used Monte Carlo simulations to simulate the shell growth on nanowire templates. • Angular atomic flux (i.e., sputtering at high pressure) leads to conformal and uniform coatings. • A small angle (< 45°) to the directional flux needs to be introduced for conformal coatings.

  4. Shell's deep thinkers

    International Nuclear Information System (INIS)

    In a bid to improve delivery of best practice in deepwater operations to all its companies around the globe, Shell has just set up 'centres of excellence' on both sides of the Atlantic. The author has been asking each of the men heading up those centres how big a change all this is. (author)

  5. Evanescent Wave Atomic Mirror

    Science.gov (United States)

    Ghezali, S.; Taleb, A.

    2008-09-01

    A research project at the "Laboratoire d'électronique quantique" consists in a theoretical study of the reflection and diffraction phenomena via an atomic mirror. This poster presents the principle of an atomic mirror. Many groups in the world have constructed this type of atom optics experiments such as in Paris-Orsay-Villetaneuse (France), Stanford-Gaithersburg (USA), Munich-Heidelberg (Germany), etc. A laser beam goes into a prism with an incidence bigger than the critical incidence. It undergoes a total reflection on the plane face of the prism and then exits. The transmitted resulting wave out of the prism is evanescent and repulsive as the frequency detuning of the laser beam compared to the atomic transition δ = ωL-ω0 is positive. The cold atomic sample interacts with this evanescent wave and undergoes one or more elastic bounces by passing into backward points in its trajectory because the atoms' kinetic energy (of the order of the μeV) is less than the maximum of the dipolar potential barrier ℏΩ2/Δ where Ω is the Rabi frequency [1]. In fact, the atoms are cooled and captured in a magneto-optical trap placed at a distance of the order of the cm above the prism surface. The dipolar potential with which interact the slow atoms is obtained for a two level atom in a case of a dipolar electric transition (D2 Rubidium transition at a wavelength of 780nm delivered by a Titane-Saphir laser between a fundamental state Jf = l/2 and an excited state Je = 3/2). This potential is corrected by an attractive Van der Waals term which varies as 1/z3 in the Lennard-Jones approximation (typical atomic distance of the order of λ0/2π where λ0 is the laser wavelength) and in 1/z4 if the distance between the atom and its image in the dielectric is big in front of λ0/2π. This last case is obtained in a quantum electrodynamic calculation by taking into account an orthornormal base [2]. We'll examine the role of spontaneous emission for which the rate is inversely

  6. Sequential multiphoton multiple ionization of atomic argon and xenon irradiated by x-ray free-electron laser pulses from SACLA

    International Nuclear Information System (INIS)

    We have investigated multiphoton multiple ionization of argon and xenon atoms at 5 keV using a new x-ray free electron laser (XFEL) facility, the SPring-8 Angstrom Compact free electron LAser (SACLA) in Japan. The experimental results are compared with the new theoretical results presented here. The absolute fluence of the XFEL pulse has been determined with the help of the calculations utilizing two-photon processes in the argon atom. The high charge states up to +22 observed for Xe in comparison with the calculations point to the occurrence of sequential L-shell multiphoton absorption and of resonance-enabled x-ray multiple ionization. (paper)

  7. Atomic energy

    CERN Multimedia

    1996-01-01

    Interviews following the 1991 co-operation Agreement between the Department of Atomic Energy (DAE) of the Government of India and the European Organization for Nuclear Research (CERN) concerning the participation in the Large Hadron Collider Project (LHC) . With Chidambaram, R, Chairman, Atomic Energy Commission and Secretary, Department of Atomic Energy, Department of Atomic Energy (DAE) of the Government of India and Professor Llewellyn-Smith, Christopher H, Director-General, CERN.

  8. Atom chips

    CERN Document Server

    Reichel, Jakob

    2010-01-01

    This book provides a stimulating and multifaceted picture of a rapidly developing field. The first part reviews fundamentals of atom chip research in tutorial style, while subsequent parts focus on the topics of atom-surface interaction, coherence on atom chips, and possible future directions of atom chip research. The articles are written by leading researchers in the field in their characteristic and individual styles.

  9. Stability of charged thin shells

    International Nuclear Information System (INIS)

    In this article we study the mechanical stability of spherically symmetric thin shells with charge, in Einstein-Maxwell and Einstein-Born-Infeld theories. We analyze linearized perturbations preserving the symmetry, for shells around vacuum and shells surrounding noncharged black holes.

  10. Temporal structures in shell models

    DEFF Research Database (Denmark)

    Okkels, F.

    2001-01-01

    The intermittent dynamics of the turbulent Gledzer, Ohkitani, and Yamada shell-model is completely characterized by a single type of burstlike structure, which moves through the shells like a front. This temporal structure is described by the dynamics of the instantaneous configuration of the shell...

  11. Simulation for double shell pinch

    Institute of Scientific and Technical Information of China (English)

    Wang Gang-Hua; Hu Xi-Jing; Sun Cheng-Wei

    2004-01-01

    Basic shock phenomena are presented in a composite pinch, a hybrid of the Z-pinch. The successive transfer of current within the plasma structure is demonstrated by our calculations. Properties of the shock wave are described.The current distribution between the two shells after the outer shell hitting the inner shell is also discussed.

  12. Recent Advances in Shell Evolution with Shell-Model Calculations

    CERN Document Server

    Utsuno, Yutaka; Tsunoda, Yusuke; Shimizu, Noritaka; Honma, Michio; Togashi, Tomoaki; Mizusaki, Takahiro

    2014-01-01

    Shell evolution in exotic nuclei is investigated with large-scale shell-model calculations. After presenting that the central and tensor forces produce distinctive ways of shell evolution, we show several recent results: (i) evolution of single-particle-like levels in antimony and cupper isotopes, (ii) shape coexistence in nickel isotopes understood in terms of configuration-dependent shell structure, and (iii) prediction of the evolution of the recently established $N=34$ magic number towards smaller proton numbers. In any case, large-scale shell-model calculations play indispensable roles in describing the interplay between single-particle character and correlation.

  13. L X-ray emission induced by heavy ions

    Science.gov (United States)

    Pajek, M.; Banaś, D.; Braziewicz, J.; Majewska, U.; Semaniak, J.; Fijał-Kirejczyk, I.; Jaskóła, M.; Czarnacki, W.; Korman, A.; Kretschmer, W.; Mukoyama, T.; Trautmann, D.

    2015-11-01

    Particle-induced X-ray emission (PIXE) technique is usually applied using typically 1 MeV to 3 MeV protons or helium ions, for which the ion-atom interaction is dominated by the single ionization process. For heavier ions the multiple ionization plays an increasingly important role and this process can influence substantially both the X-ray spectra and atomic decay rates. Additionally, the subshell coupling effects are important for the L- and M-shells ionized by heavy ions. Here we discuss the main features of the X-ray emission induced by heavy ions which are important for PIXE applications, namely, the effects of X-ray line shifts and broadening, vacancy rearrangement and change of the fluorescence and Coster-Kronig yields in multiple ionized atoms. These effects are illustrated here by the results of the measurements of L X-ray emission from heavy atoms bombarded by 6 MeV to 36 MeV Si ions, which were reported earlier. The strong L-subshell coupling effects are observed, in particular L2-subshell, which can be accounted for within the coupling subshell model (CSM) developed within the semiclassical approximation. Finally, the prospects to use heavy ions in PIXE analysis are discussed.

  14. The Effects of Low-Temperature Dielectronic Recombination on the Relative Populations of the Fe M-Shell States

    Science.gov (United States)

    Kraemer, S. B.; Ferland, G. J.; Gabel, J. R.

    2004-04-01

    We examine the effects of low-temperature, or Δn=0, dielectronic recombination (DR) on the ionization balance of the Fe M shell (Fe IX-Fe XVI). Since Δn=0 rates are not available for these ions, we have derived estimates based on the existing rates for the first four ionization states of the CNO sequence and newly calculated rates for L-shell ions of third-row elements and Fe. For a range of ionization parameter and column density applicable to the intrinsic absorbers detected in ASCA, Chandra, and XMM-Newton observations of Seyfert galaxies, we generated two grids of photoionization models, with and without DR. The results show that the ionization parameter at which the population of an Fe M-shell ion peaks can increase in some cases by a factor of more than 2 when these rates are included. More importantly, there are dramatic changes in the range in ionization parameter over which individual M-shell ions contain significant fractions of the total Fe (e.g., >10%) in the plasma. These results may explain the mismatch between the range of Fe ionization states detected in the X-ray spectra of Seyfert galaxies, identified by the energies of the M-shell unresolved transition array, and those predicted by photoionization models of the X-ray absorbers that reproduce lines of second- and third-row elements. The results suggest that care should be taken in using third- and fourth-row ions to constrain the physical conditions in photoionized X-ray plasmas until accurate DR rates are available. This underscores the importance of atomic physics in interpreting astronomical spectroscopy.

  15. 7 CFR 51.2002 - Split shell.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Split shell. 51.2002 Section 51.2002 Agriculture... Standards for Grades of Filberts in the Shell 1 Definitions § 51.2002 Split shell. Split shell means a shell... of the shell, measured in the direction of the crack....

  16. Atomic polarizabilities

    Energy Technology Data Exchange (ETDEWEB)

    Safronova, M. S. [Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States); Mitroy, J. [School of Engineering, Charles Darwin University, Darwin NT 0909 (Australia); Clark, Charles W. [Joint Quantum Institute, National Institute of Standards and Technology and the University of Maryland, Gaithersburg, Maryland 20899-8410 (United States); Kozlov, M. G. [Petersburg Nuclear Physics Institute, Gatchina 188300 (Russian Federation)

    2015-01-22

    The atomic dipole polarizability governs the first-order response of an atom to an applied electric field. Atomic polarization phenomena impinge upon a number of areas and processes in physics and have been the subject of considerable interest and heightened importance in recent years. In this paper, we will summarize some of the recent applications of atomic polarizability studies. A summary of results for polarizabilities of noble gases, monovalent, and divalent atoms is given. The development of the CI+all-order method that combines configuration interaction and linearized coupled-cluster approaches is discussed.

  17. Atomic Physics

    CERN Document Server

    Foot, Christopher J

    2007-01-01

    This text will thoroughly update the existing literature on atomic physics. Intended to accompany an advanced undergraduate course in atomic physics, the book will lead the students up to the latest advances and the applications to Bose-Einstein Condensation of atoms, matter-wave inter-ferometry and quantum computing with trapped ions. The elementary atomic physics covered in the early chapters should be accessible to undergraduates when they are first introduced to the subject. To complement. the usual quantum mechanical treatment of atomic structure the book strongly emphasizes the experimen

  18. Atomic polarizabilities

    International Nuclear Information System (INIS)

    The atomic dipole polarizability governs the first-order response of an atom to an applied electric field. Atomic polarization phenomena impinge upon a number of areas and processes in physics and have been the subject of considerable interest and heightened importance in recent years. In this paper, we will summarize some of the recent applications of atomic polarizability studies. A summary of results for polarizabilities of noble gases, monovalent, and divalent atoms is given. The development of the CI+all-order method that combines configuration interaction and linearized coupled-cluster approaches is discussed

  19. Ethanol production of banana shell and cassava starch

    International Nuclear Information System (INIS)

    In this work the acid hydrolysis of the starch was evaluated in cassava and the cellulose shell banana and its later fermentation to ethanol, the means of fermentation were adjusted for the microorganisms saccharomyces cerevisiae nrrl y-2034 and zymomonas mobilis cp4. The banana shell has been characterized, which possesses a content of starch, cellulose and hemicelluloses that represent more than 80% of the shell deserve the study of this as source of carbon. The acid hydrolysis of the banana shell yield 20g/l reducing sugar was obtained as maximum concentration. For the cassava with 170 g/l of starch to ph 0.8 in 5 hours complete conversion is achieved to you reducing sugars and any inhibitory effect is not noticed on the part of the cultivations carried out with banana shell and cassava by the cyanide presence in the cassava and for the formation of toxic compounds in the acid hydrolysis the cellulose in banana shell. For the fermentation carried out with saccharomyces cerevisiae a concentration of ethanol of 7.92± 0.31% it is achieved and a considerable production of ethanol is not appreciated (smaller than 0.1 g/l) for none of the means fermented with zymomonas mobilis

  20. Deterministic tuning of slow-light in photonic-crystal waveguides through the C and L bands by atomic layer deposition

    CERN Document Server

    Chen, Charlton J; Meric, Inanc; Shepard, Ken L; Wong, Chee Wei; Green, William M J; Vlasov, Yurii A; Assefa, Solomon

    2009-01-01

    We demonstrate digital tuning of the slow-light regime in silicon photonic-crystal waveguides by performing atomic layer deposition of hafnium oxide. The high group-index regime was deterministically controlled (red-shift of 140 +/- 10 pm per atomic layer) without affecting the group-velocity dispersion and third-order dispersion. Additionally, differential tuning of 110 +/- 30 pm per monolayer of the slow-light TE-like and TM-like modes was observed. This passive post-fabrication process has potential applications including the tuning of chip-scale optical interconnects, as well as Raman and parametric amplification.

  1. Atom interferometry

    International Nuclear Information System (INIS)

    We will first present a development of the fundamental principles of atom interferometers. Next we will discuss a few of the various methods now available to split and recombine atomic De Broglie waves, with special emphasis on atom interferometers based on optical pulses. We will also be particularly concerned with high precision interferometers with long measurement times such those made with atomic fountains. The application of atom interferometry to the measurement of the acceleration due to gravity will be detailed. We will also develop the atom interferometry based on adiabatic transfer and we will apply it to the measurement of the photon recoil in the case of the Doppler shift of an atomic resonance caused by the momentum recoil from an absorbed photon. Finally the outlook of future developments will be given. (A.C.)

  2. Shell funds chair

    Science.gov (United States)

    The Shell Companies Foundation, Inc., of Houston, Tex., has given $750,000 to the University of Texas at Austin to establish the Shell Distinguished Chair in Geophysics. The 5-year, $150,000-per-year grant will support the studies of John G. Sclater. Sclater, currently a professor at the Massachusetts Institute of Technology, has accepted a joint position that begins July 1 in the geological sciences department and in the Institute for Geophysics at UT Austin.Sclater's research into the formation of ocean basins has applications for understanding the way petroleum deposits mature. He has studied the reconstruction of movements of the continents and the subsidence of ocean basins. He is considered an expert in the interpretation of geothermal and seismic data.

  3. Giant atoms for the production of nuclear fuel

    International Nuclear Information System (INIS)

    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 U235 and U238. (orig.)

  4. Fe3O4 and CdS based bifunctional core–shell nanostructure

    International Nuclear Information System (INIS)

    Highlights: ► First report on a room temperature aqueous process for growth of a hybrid core shell nanostructure containing a magnetic core and a semiconducting shell. ► Formation of distinct core shell nanostructure revealed by high resolution transmission electron microscopy. ► A bifunctional nature combining magnetic as well as photoresponce for the as synthesised core shell nanostructures demonstrated. ► A tendency towards self organisation of the core–shell nanostructure. ► Possible applications including purification and isolation of biological materials, drug delivery system, bio-labels, spintronics, etc. -- Abstract: A room temperature solution process for synthesis of Fe3O4 nanoparticles and their hybrid core shell nanostructures using CdS as the shell material has been described. The as grown particles have been characterised using XRD, Rietveld refinement, high resolution transmission electron microscopy, atomic force microscopy, superconducting quantum interference device, optical absorbance and photoluminescence spectroscopy. A superparamagnetic response revealed from the magnetisation measurements of the as synthesised magnetite nanoparticles was retained even after the growth of the CdS shell. From luminescence and high resolution atomic force microscopy measurements, it is shown that the core–shell structures advantageously combine magnetic as well as fluorescence response with a tendency towards self-organization.

  5. Quantum electrodynamics tests and X-rays standards using pionic atoms and highly charged ions; Tests d'electrodynamique quantique et etalons de rayons-X a l'aide des atomes pioniques et des ions multicharges

    Energy Technology Data Exchange (ETDEWEB)

    Martino, Trassinelli

    2005-12-15

    The object of this thesis is to present a new measurement of the pion mass using pionic nitrogen X-ray spectroscopy and results on helium-like argon and sulphur spectroscopy. The new pion mass has been measured with an accuracy of 1.7 ppm, 30% better that the present world average value, and it is obtained from Bragg spectroscopy of 5 ->4 pionic nitrogen transitions using the theoretical predictions provided by quantum electrodynamics. We have got: m({pi}{sup -}) = (139.571042 {+-} 0.000210 {+-} 0.000110) where the first error is due to the statistics and the second is the systematic error. I present the calculation of the hyperfine structure and recoil corrections for pionic atoms using a new perturbation method for the Klein-Gordon equation. The spectrometer used for this measurement has been characterized with the relativistic M1 transitions from helium-like ions produced with a new device, the Electron-Cyclotron-Resonance Ion Trap. High statistics spectra from these ions have enabled us to measure transition energies with an accuracy of some ppm which has allowed us to compare theoretical predictions with experiment data. X-ray emission from pionic atoms and multicharged ions can be used to define new types of X-ray standards for energies of a few keV.

  6. Ionization cross section measurement of heavy atom L levels (Z>=72) with Americium 241 γ radiation at 59.6 keV

    International Nuclear Information System (INIS)

    The cross-sections for L X-ray production by the 59.6 keV γ radiation of 241Am have been measured for heavy elements (Z > 70). The L subshell ionization cross-sections have been calculated on the basis of these measurements

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

    International Nuclear Information System (INIS)

    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 26Mg and 27Al. (Auth./C.F.)

  8. Atomic Energy Commission (Amendment) Law, 1993

    International Nuclear Information System (INIS)

    The Atomic Energy Commission (Amendment) Law, 1993 (P.N.D.C.L. 308) seeks to amend the Atomic Energy Commission Act of 1963 (Act 204) so as to provide for the establishment of a Radiation Protection Board and other institutes under the Ghana Atomic Energy Commission. The Law further repeats the Atomic Energy Commission (Amendment) Law of 1982 (P.N.D.C.L. 37). (EAA)

  9. Schroedinger atom

    International Nuclear Information System (INIS)

    Features of an electrodynamical interpretation suggested by Schroedinger for the wave function are discribed. According to this conception electron charges are continuously distributed all over the volume of an atomic system. The proof is given that classical electrodynamics keeps its action inside atom. Schroedinger's atom has been shown to be the only model in which electrones do not lose their energy for emission when they move around nucleus. A significance of the distributed electron charge self-field is estimated. Practical applications of this conception have been noted including the new trend in quantum electrodynamics. Experimental and theoretical corroborations of the atom model with a continuous electron charge are adduced

  10. Atomic physics

    International Nuclear Information System (INIS)

    Research activities in atomic physics at Lawrence Berkeley Laboratory during 1976 are described. Topics covered include: experiments on stored ions; test for parity violation in neutral weak currents; energy conservation and astrophysics; atomic absorption spectroscopy, atomic and molecular detectors; theoretical studies of quantum electrodynamics and high-z ions; atomic beam magnetic resonance; radiative decay from the 23Po,2 levels of helium-like argon; quenching of the metastable 2S/sub 1/2/ state of hydrogen-like argon in an external electric field; and lifetime of the 23Po level of helium-like krypton

  11. First Principles Study of Core-Shell Semiconductor Nanocrystals

    Science.gov (United States)

    Vasiliev, Igor

    2011-03-01

    Core-shell nanocrystals composed of two different semiconductors have recently attracted considerable attention. These structures provide enhanced functionality and possess more degrees of freedom than single-component semiconductor nanocrystals and quantum dots. I present the results of ab initio density functional calculations for the structures, electronic densities of states, and optical absorption gaps of core-shell nanocrystals composed of group II-VI semiconductors, such as CdSe, CdTe, ZnSe, and ZnTe. The outer surfaces of the nanocrystals are passivated using partially charged hydrogen atoms. The calculations are performed for ``traditional'' core-shell nanocrystals, in which a core a narrow gap semiconductor is covered with a shell of a wide gap material, and ``inverted'' core-shell nanocrystals, in which a wide-gap core is enclosed in a narrow-gap shell. Supported by the Donors of the American Chemical Society Petroleum Research Fund under Grant No. PRF-48556-AC10 and by the U. S. Department of Energy under Grant No. DE-FG36-08GO88008.

  12. Experimental studies of ions and atoms interaction with insulating surface; Etude experimentale de l'interaction rasante d'atomes et d'ions sur des surfaces isolantes

    Energy Technology Data Exchange (ETDEWEB)

    Villette, J

    2000-10-15

    Grazing collisions (<3 deg.) of keV ions and atoms: H{sup +}, Ne{sup +}, Ne{sup 0}, Na{sup +} on LiF (001) single crystal, an ionic insulator, are investigated by a time of flight technique. The incident beam is chopped and the scattered particles are collected on a position sensitive detector providing differential cross section while the time of flight gives the energy loss. Deflection plates allow the charge state analysis. Secondary electrons are detected in coincidence allowing direct measurements of electron emission yield, angular and energetic distribution through time of flight measurements. The target electronic structure characterized by a large band gap, governs the collisional processes: charge exchange, electronic excitations and electron emission. In particular, these studies show that the population of local target excitations surface excitons is the major contribution to the kinetic energy transfer (stopping power). Auger neutralization of Ne{sup +} and He{sup +} ions reveals the population of quasi-molecular excitons, an exciton bound on two holes. Referenced in the literature as trion. A direct energy balance determines the binding energy associated with these excited states of the surface. Besides these electronic energy loss processes, two nuclear energy loss mechanisms are characterized. These processes imply momentum transfer to individual target atoms during close binary collisions or, if the projectile is charged, to collective mode of optical phonons induced by the projectile coulomb field. The effect of the temperature on the scattering profile, the contribution of topological surface defects to the energy loss profile and to skipping motion on the surface are analyzed in view of classical trajectory simulations. (author)

  13. Radiative shell thinning in intense laser-driven blast waves

    International Nuclear Information System (INIS)

    The structural evolution of blast waves launched by intense laser pulses in gases is investigated. These blast waves exhibit significant energy loss through radiation while propagating in xenon as evidenced by interferometric imaging revealing radiative precursors and deceleration parameters well below those of an energy-conserving wave. Thinning of the blast wave shell from radiative cooling is observed through comparison of shocks launched in gases of differing atomic number. Shell thinning is also measured when the gas density is altered, indicating the influence of conditions within the preshock medium. These results are compared with radiative-hydrodynamic simulations.

  14. Effect of the shell on the transport properties of poly(glycerol) and Poly(ethylene imine) nanoparticles

    International Nuclear Information System (INIS)

    Dendritic core-shell architectures containing poly (glycerol) and poly (ethylene imine) cores and poly(lactide) shell (PG-PLA and PEI-PLA respectively) were synthesized. Analogous of these core-shell architectures containing the same cores but poly (L-lactide) shell (PG-PLLA and PEI-PLLA, respectively) were also synthesized. In this work PG and PEI were used as macroinitiator for ring opening polymerization of the lactid and L-lactide monomers. Different molar ratios of monomer to end functional groups of PG ([LA]/[OH]) and PEI ([LA]/[NHn] (n = 1 or 2)) were used to prepare the core-shell architectures with different shell thickness. These core-shell architectures were able to encapsulate and transport the small guest molecules. Their transport capacity (TC) depended on the type and thickness of the shells. TC of core-shell architectures containing PLLA shell was higher than that for their analogs containing PLA shell. The diameter of core-shell architectures was between 20-80 nm. The rate of release of guest molecules from chloroform solution of nanocarriers to water phase was investigated and it depended on the type of the core, shell and solvent

  15. On-shell equivalence of two formulations for superstring field theory

    CERN Document Server

    Goto, Keiyu

    2015-01-01

    In this paper we derive the condition providing the on-shell equivalence of $L_{\\infty}$-type and WZW-like formulations for superstring field theory. We construct the NS string products $L= \\{L_{n}\\}_{n=1}^{\\infty}$ of $L_{\\infty}$-type formulation and the shifted BRST operator $Q_{\\mathcal{G}}$ in WZW-like formulation by the similarity transformations of the BRST operator $Q$. Utilizing the similarity transformations, we can consider a morphism connecting the $L_{\\infty}$-algebras on both sides. It naturally induces the field redefinitions and guarantees the equivalence of the on-shell conditions in two formulations. In addition, we have confirmed up to quartic order that the on-shell equivalence condition also provides the off-shell equivalence. Then partial-gauge-fixing conditions giving $L_{\\infty}$-relations in WZW-like formulation naturally appear.

  16. Multi-Shell Shell Model for Heavy Nuclei

    OpenAIRE

    Sun, Yang; Wu, Cheng-Li

    2003-01-01

    Performing a shell model calculation for heavy nuclei has been a long-standing problem in nuclear physics. Here we propose one possible solution. The central idea of this proposal is to take the advantages of two existing models, the Projected Shell Model (PSM) and the Fermion Dynamical Symmetry Model (FDSM), to construct a multi-shell shell model. The PSM is an efficient method of coupling quasi-particle excitations to the high-spin rotational motion, whereas the FDSM contains a successful t...

  17. Multi-shell effective interactions

    CERN Document Server

    Tsunoda, Naofumi; Hjorth-Jensen, Morten; Otsuka, Takaharu

    2013-01-01

    Background: Effective interactions, either derived from microscopic theories or based on fitting selected properties of nuclei in specific mass regions, are widely used inputs to shell-model studies of nuclei. Until recently, most shell-model calculations have been confined to a single oscillator shell. Recent interest in nuclei away from the stability line, requires however larger shell-model spaces. Since the derivation of microscopic effective interactions has been limited to degenerate model spaces, there are both conceptual and practical limits to present shell-model calculations that utilize such interactions. Purpose: The aim of this work is to present a novel microscopic method to calculate effective interactions for the nuclear shell model. Its main difference from existing theories is that it can be applied not only to degenerate model spaces but also to non-degenerate model spaces. Methods: The formalism is presented in the form of many-body perturbation theory based on the recently developed Exten...

  18. Wrinkling of Pressurized Elastic Shells

    KAUST Repository

    Vella, Dominic

    2011-10-01

    We study the formation of localized structures formed by the point loading of an internally pressurized elastic shell. While unpressurized shells (such as a ping-pong ball) buckle into polygonal structures, we show that pressurized shells are subject to a wrinkling instability. We study wrinkling in depth, presenting scaling laws for the critical indentation at which wrinkling occurs and the number of wrinkles formed in terms of the internal pressurization and material properties of the shell. These results are validated by numerical simulations. We show that the evolution of the wrinkle length with increasing indentation can be understood for highly pressurized shells from membrane theory. These results suggest that the position and number of wrinkles may be used in combination to give simple methods for the estimation of the mechanical properties of highly pressurized shells. © 2011 American Physical Society.

  19. Plate shell structures of glass

    DEFF Research Database (Denmark)

    Bagger, Anne

    . Together with Ghent University, a script has been developed for an automated generation of a given plate shell geometry and a corresponding finite element (FE) model. A suitable FE modelling technique is proposed, suggesting a relatively simple method of modelling the connection detail's stiffness......This thesis is a study of plate shell structures -- a type of shell structure with a piecewise plane geometry, organized so that the load bearing system is constituted by distributed in-plane forces in the facets. The high stiffness-to-weight ratio of smoothly curved shell structures is mainly due...... to their curved shape. A plate shell structure maintains a high stiffness-to-weight ratio, while facilitating the use of plane structural elements. The study focuses on using laminated glass panes for the load bearing facets. Various methods of generating a plate shell geometry are suggested...

  20. Shell structure from nuclear observables

    CERN Document Server

    Bentley, I; Cunningham, S; Aprahamian, A

    2016-01-01

    The appearance and disappearance of shells and subshells are determined using a previously introduced method of structural analysis. This work extends the approach and applies it to protons, in addition to neutrons, in an attempt to provide a more complete understanding of shell structure in nuclei. Experimental observables including the mean-square charge radius, as well as other spectroscopic and mass related quantities are analyzed for extrema. This analysis also uses differential observables among adjacent even-even nuclei to serve as the derivatives for these quantities of interest. Local extrema in these quantities indicate shell structure and the lack of local extrema indicate missing shell closures. The shell structure of low-mass nuclei is inconsistent likely as a consequence of the single-particle structure. Additionally, multiple shell features occurring in midshell regions are determined by combining information from two or more observables. Our results near stability complement previous observati...

  1. Shell structure from nuclear observables

    Science.gov (United States)

    Bentley, I.; Rodríguez, Y. Colón; Cunningham, S.; Aprahamian, A.

    2016-04-01

    The appearance and disappearance of shells and subshells are determined using a previously introduced method of structural analysis. This work extends the approach and applies it to protons, in addition to neutrons, in an attempt to provide a more complete understanding of shell structure in nuclei. Experimental observables including the mean-square charge radius, as well as other spectroscopic and mass related quantities are analyzed for extrema. This analysis also uses differential observables among adjacent even-even nuclei to serve as the derivatives for these quantities of interest. Local extrema in these quantities indicate shell structure and the lack of local extrema indicate missing shell closures. The shell structure of low-mass nuclei is inconsistent likely as a consequence of the single-particle structure. Additionally, multiple shell features occurring in midshell regions are determined by combining information from two or more observables. Our results near stability complement previous observations further out.

  2. Properties of few-electron artificial atoms

    OpenAIRE

    Varga, K.; Navratil, P.; Usukura, J.; Suzuki, Y

    2000-01-01

    The spectra of quantum dots of different geometry (``quantum ring'', ``quantum cylinder'', ``spherical square-well'' and ``parabolic confinement'') are studied. The stochastic variational method on correlated Gaussian basis functions and a large scale shell-model approach have been used to investigate these ``artificial'' atoms and their properties in magnetic field. Accurate numerical results are presented for $N$=2-8 electron systems.

  3. Atomic physics

    CERN Document Server

    Born, Max

    1989-01-01

    The Nobel Laureate's brilliant exposition of the kinetic theory of gases, elementary particles, the nuclear atom, wave-corpuscles, atomic structure and spectral lines, electron spin and Pauli's principle, quantum statistics, molecular structure and nuclear physics. Over 40 appendices, a bibliography, numerous figures and graphs.

  4. The notes on thin shells

    CERN Document Server

    Iofa, Mikhail Z

    2016-01-01

    Geometry of the spacetime with a spherical shell embedded in it is studied in two coordinate systems - in Kodama-Schwarzschild coordinates and in Gaussian normal coordinates. We consider transformations between the coordinate systems as in the 4D spacetime so as at the surface $\\S$ swept in the spacetime by the spherical shell. Extrinsic curvatures of the surface swept by the shell are calculated in both coordinate systems. Applications to the Israel junction conditions are discussed.

  5. Shell Joint Venture IT Framework

    OpenAIRE

    Evert Ruijs

    2013-01-01

    Dit artikel is alleen beschikbaar in het Nederlands. Shell's wereldwijde productie van olie en gas gaat voor een groot deel via Joint Ventures. Deze Joint Ventures werken in meer of mindere mate onder het management van Shell, vaak optioneel gebruik makend van Shell's processen, standaarden, gemeenschappelijke portfolio van applicaties en technologie. Om de vele soorten van applicaties en versies van implementaties beheersbaar te houden in de 'extended enterprise' is een goed raamwerk nodig. ...

  6. Creep analysis of orthotropic shells

    International Nuclear Information System (INIS)

    A method of creep analysis of orthotropic cylindrical shells subjected to axisymmetric loads has been developed. A general study of creep behaviour of cylindrical shells subjected to a uniform internal pressure has been conducted for a wide range of values of anisotropy coefficients and creep law exponent. Analysis includes determination of stress re-distribution, strain rates, stationary state stresses. Application of reference stress technique has been extended to analysis of shells. (author)

  7. Thermoluminescence measurement of calcite shells

    International Nuclear Information System (INIS)

    Thermoluminescence (TL) measurements of calcite derived from shells or shell fragments are relevant to the detection of irradiated shellfish for enforcement of food labelling regulations, and to dating of archaeological and fossil materials. The bio-inorganic nature of the material, which is both micro-porous and an intimate mixture of organic and inorganic phases, presents problems for direct TL measurements. This paper discusses the optimal conditions for direct TL measurements on dried, powdered samples from modern shells. (Author)

  8. The direct manipulation shell

    International Nuclear Information System (INIS)

    Accelerator controls systems provide parameter display pages which allow the operator to monitor and manipulate selected control points in the system. Display pages are generally implemented as either hand-crafted, purpose-built programs; or by using a specialized display page layout tool. These two methods of display page development exhibit the classic trade-off between functionality vs. ease of implementation. In the Direct Manipulation Shell we approach the process of developing a display page in a manifestly object-oriented manner. This is done by providing a general framework for interactively instantiating and manipulating display objects. (author)

  9. Report realized on behalf of the Foreign Affairs Commission, of Defense and Armed Forces on the law project allowing the additional protocol ratification to the agreement between France, European Community of the atomic energy and the International Atomic Energy Agency relative to the guaranties application in France; Rapport fait au nom de la commission des affaires etrangeres, de la defense et des forces armees sur le projet de loi autorisant la ratification du protocole additionnel a l'accord entre la France, la Communaute europeenne de l'energie atomique et l'Agence internationale de l'energie atomique relatif a l'application de garanties en France

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2002-07-01

    In a first part the author presents the International Atomic Energy Agency and its missions in the nuclear non proliferation policy especially in the agreements with the states of the TNP (Treaty of Nuclear non Proliferation). the today position of France is then analyzed towards the IAEA and the novations added by the additional protocol. (A.L.B.)

  10. PREONS SHELLS AND ATOMIC STRUCTURE Преоновые оболочки и структура атома

    Directory of Open Access Journals (Sweden)

    Trunev A. P.

    2013-03-01

    Full Text Available We consider the model of the structure of electrons and quarks, in which these particles are presented consisting of elementary particles preons. From this model, the theory of electron shells, as a continuation of the quark nuclear shells has been proposed

  11. Atomic structure calculations and identification of EUV and SXR spectral lines in Sr XXX

    Science.gov (United States)

    Goyal, Arun; Khatri, Indu; Aggarwal, Sunny; Singh, A. K.; Mohan, Man

    2015-08-01

    We report an extensive theoretical study of atomic data for Sr XXX in a wide range with L-shell electron excitations to the M-shell. We have calculated energy levels, wave-function compositions and lifetimes for lowest 113 fine structure levels and wavelengths of an extreme Ultraviolet (EUV) and soft X-ray (SXR) transitions. We have employed multi-configuration Dirac Fock method (MCDF) approach within the framework of Dirac-Coulomb Hamiltonian including quantum electrodynamics (QED) and Breit corrections. We have also presented the radiative data for electric and magnetic dipole (E1, M1) and quadrupole (E2, M2) transitions from the ground state. We have made comparisons with available energy levels compiled by NIST and achieve good agreement. But due to inadequate data in the literature, analogous relativistic distorted wave calculations have also been performed using flexible atomic code (FAC) to assess the reliability and accuracy of our results. Additionally, we have provided new atomic data for Sr XXX which is not published elsewhere in the literature and we believe that our results may be beneficial in fusion plasma research and astrophysical investigations and applications.

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

    Science.gov (United States)

    Wang, Xinqin; Cui, Yingqi; Yu, Shengping; Zeng, Qun; Yang, Mingli

    2016-04-01

    The structural, electronic, and optical properties of core-shell nanoclusters, (CdSe)x@(CdSe)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.

  13. 7 CFR 51.2289 - Shell.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Shell. 51.2289 Section 51.2289 Agriculture Regulations... Standards for Shelled English Walnuts (Juglans Regia) Definitions § 51.2289 Shell. Shell means the outer shell and/or the woody partition from between the halves of the kernel, and any fragments of either....

  14. Atomic physics at high brilliance synchrotron sources: Proceedings

    International Nuclear Information System (INIS)

    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

  15. Preparation and Characterization of Nucleus/Shell TiO2/HAP Complex Nanophotocatalyst

    Institute of Scientific and Technical Information of China (English)

    Hongfei LIU; Xiaonong CHENG; Juan YANG; Xuehua YAN; Hebin SHI

    2007-01-01

    A rapid and more efficient method was developed to prepare nucleus/shell titania/hydroxyapatite (TiO2/HAP)complex nanophotocatalyst. Hydroxyapatite (5μm) which had been dissolved with 0.1 mol/L HCI was formed on the surface of the nanosized anatase titania powders by increasing the pH value of the solution at 90℃ in the water bath for only several hours .The microstructure and morphology of the resulting sample were investigated by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy dispersive spectrum (EDS) and atomic force microscope (AFM). The results indicated that nucleus/shell structural TiO2/HAP was formed in our experiments, and the thickness of the coating layer was about 5 nm. Photocatalytic decomposition of methyl orange was utilized to test the photocatalysis of the resulting samples and the result was compared with that of pure anatase titania powders (about 20 nm). It was shown that the photocatalytic activity of the sample was not decreased due to the coating of HAP.

  16. Novel thermo-sensitive core-shell nanoparticles for targeted paclitaxel delivery

    International Nuclear Information System (INIS)

    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.

  17. Detection of positron-atom bound states through resonant annihilation

    CERN Document Server

    Dzuba, V A; Gribakin, G F

    2010-01-01

    A method is proposed for detecting positron-atom bound states by observing Feshbach resonances in positron annihilation at electron volt energies. The method is applicable to a range of open-shell transition metal atoms which are likely to bind the positron: Si, Fe, Co, Ni, Ge, Tc, Ru, Rh, Sn, Sb, Ta, W, Os, Ir, and Pt.

  18. QED theory of the nuclear recoil effect in atoms

    CERN Document Server

    Shabaev, V M

    1998-01-01

    The quantum electrodynamic theory of the nuclear recoil effect in atoms to all orders in \\alpha Z is formulated. The nuclear recoil corrections for atoms with one and two electrons over closed shells are considered in detail. The problem of the composite nuclear structure in the theory of the nuclear recoil effect is discussed.

  19. Explanation of the recent results on photoionization of endohedral atoms

    CERN Document Server

    Amusia, M Ya; Drukarev, E G

    2014-01-01

    We suggest an explanation of the recently observed discrepancy between the experimental and theoretical results on ionization of atoms, encapsulated into the fullerenes by photons with the energies of about 80-190eV. On the ground of previous theoretical considerations we conclude that the photoionization of the caged atom without excitation of the fullerene shell has low probability.

  20. QED theory of the nuclear recoil effect in atoms

    OpenAIRE

    Shabaev, V. M.

    1997-01-01

    The quantum electrodynamic theory of the nuclear recoil effect in atoms to all orders in \\alpha Z is formulated. The nuclear recoil corrections for atoms with one and two electrons over closed shells are considered in detail. The problem of the composite nuclear structure in the theory of the nuclear recoil effect is discussed.

  1. Contribution of high-nl shells to electron-impact ionization processes

    CERN Document Server

    Jonauskas, V; Merkelis, G; Gaigalas, G; Kisielius, R; Kučas, S; Masys, Š; Radžiūtė, L; Rynkun, P

    2015-01-01

    The contribution to electron-impact ionization cross sections from excitations to high-nl shells and a consequent autoionization is investigated. We perform relativistic subconfiguration-average and detailed level-to-level calculations for this process. Ionization cross sections for the W27+ ion are presented to illustrate the large influence of the high shells (n >= 9) and orbitals (l >= 4) in the excitation-autoionization process. The obtained results show that the excitations to the high shells (n >= 9) increase cross sections of the indirect ionization process by a factor of 2 compared to the excitations to the lower shells (n <= 8). The excitations to the shells with orbital quantum number l = 4 give the largest contribution comparedwith the other orbital quantum numbers l. Radiative damping reduces the cross sections of the indirect process approximately twofold in the case of the level-to-level calculations. Determined data show that the excitation-autoionization process contributes approximately 40...

  2. Performances evaluation of the PHARAO atomic fountain: participation to the study of the PHARAO space clock; Evaluation des performances de la fontaine atomique PHARAO, participation a l'etude de l'horloge spatiale PHARAO

    Energy Technology Data Exchange (ETDEWEB)

    Abgrall, M

    2003-01-01

    The performances of an atomic frequency standard depend drastically on the observation time of the atoms. The interrogation of laser cooled atoms allows to obtain about half a second interaction time in a fountain geometry. This duration could be much more varied in absence of gravity, and would allow a better trade-off between stability and accuracy. The application of this principle is the aim of the PHARAO project, that should attend to the ACES mission planned in 2006 onboard the International Space Station. The first part of this thesis deals with the cold Cs{sup 133} PHARAO fountain. This clock stems from the transformation of a space clock prototype previously tested in microgravity. A detailed evaluation of the whole frequency shifts has been carried out, reaching a 7.7 10{sup -16} accuracy and a 1.7 10{sup -13}{tau}{sup -1/2} short term stability. These values are obtained for 4 10{sup 5} detected atoms, that provides a good stability-accuracy trade-off. This transportable fountain, built at BNM-SYRTE, has been operating at MPQ in Munich (Germany). The collaboration between the 2 laboratories gave a {approx} 10 improvement factor on the measurement accuracy (1.8 10{sup -14}) for the 1S - 2S two photons hydrogen transition. In a second part of this thesis, we present the characterisation of 2 elements of the PHARAO space clock: the construction of a standard extended cavity laser and the test of the phase symmetry between the two interrogating areas of the space cavity. (author)

  3. Dynamics study of green AuNP formation and their basis for Au-Pt core-shell nanostructure synthesis

    DEFF Research Database (Denmark)

    Engelbrekt, Christian; Seselj, Nedjeljko; Ulstrup, Jens; Zhang, Jingdong

    details of nanoparticle formation has been developed employing readily available electrochemical and optical techniques. The aim is to understand which parameters control the growth and shape and at which stages of the synthesis. The gold nanoparticles (AuNPs) studied are further used as seeds for size...... controlled AuNPs and Au - Pt core - shell NPs with an atomically thin Pt shell...

  4. Photoionization modelling of metal-enriched nova shells

    International Nuclear Information System (INIS)

    A photoionization model has been developed to investigate the physical conditions in old nova shells with large metal abundances. Atomic rates at low temperatures are included in the model so that the evolution of shells can be traced from their hot, early stages to their later cool phases. X-ray processes are also included. A situation in which a region of lowest temperature but highest ionization can exist at the inner edge of a nebula is demonstrated. A non-uniform density distribution is compared with a uniform density and the observational consequences discussed. The shell of the old nova, CVP Pup, is analysed in detail and its evolution during its constant-luminosity phase traced. (author)

  5. Multi-major-shell shell model for heavy nuclei–an extended projected shell model

    International Nuclear Information System (INIS)

    The projected shell model (PSM) in its original version is an efficient shell model truncation scheme for well deformed nuclei. However, the model is applicable only to rotational motion, but not collective vibrations. In this paper, we discuss a scheme that extends the PSM applicability to low-lying rotational and vibrational states possibly in all kinds of heavy nuclei (from deformed via transitional to spherical), thus rendering it to be a more general multi-major-shell shell model for heavy nuclei. Three known types of vibration (β, γ, and scissors-mode) are discussed. (author)

  6. Biomechanics of turtle shells: how whole shells fail in compression.

    Science.gov (United States)

    Magwene, Paul M; Socha, John J

    2013-02-01

    Turtle shells are a form of armor that provides varying degrees of protection against predation. Although this function of the shell as armor is widely appreciated, the mechanical limits of protection and the modes of failure when subjected to breaking stresses have not been well explored. We studied the mechanical properties of whole shells and of isolated bony tissues and sutures in four species of turtles (Trachemys scripta, Malaclemys terrapin, Chrysemys picta, and Terrapene carolina) using a combination of structural and mechanical tests. Structural properties were evaluated by subjecting whole shells to compressive and point loads in order to quantify maximum load, work to failure, and relative shell deformations. The mechanical properties of bone and sutures from the plastral region of the shell were evaluated using three-point bending experiments. Analysis of whole shell structural properties suggests that small shells undergo relatively greater deformations before failure than do large shells and similar amounts of energy are required to induce failure under both point and compressive loads. Location of failures occurred far more often at sulci than at sutures (representing the margins of the epidermal scutes and the underlying bones, respectively), suggesting that the small grooves in the bone created by the sulci introduce zones of weakness in the shell. Values for bending strength, ultimate bending strain, Young's modulus, and energy absorption, calculated from the three-point bending data, indicate that sutures are relatively weaker than the surrounding bone, but are able to absorb similar amounts of energy due to higher ultimate strain values. PMID:23203474

  7. Opportunities for atomic physics with hard synchrotron radiation

    International Nuclear Information System (INIS)

    The construction of third-generation synchrotron radiation facilities places atomic and molecular scientists at the threshold of extraordinary opportunities. Areas of potential interest for the APS in atomic physics are: (1) exploration of relativistic and QED effects which become prominent in inner shells and at high Z; (2) total photon interaction cross sections; (3) scattering; (4) fluorescence; (5) photo- and Auger-electron spectrometries; and (6) ion spectrometry. A special regime in which the APS will lend access to unprecedented exploration is atomic inner-shell phenomena

  8. Excitation Potentials and Shell Corrections for the Elements Z2=20 to Z2=30

    DEFF Research Database (Denmark)

    Andersen, H.H.; Sørensen, H.; Vadja, P.

    1969-01-01

    Excitation potentials and shell corrections for the elements Z 2=20 to Z2=30 are evaluated from experimental stopping-power data for 5-12-MeV protons and deuterons. Use is made of Walske's K- and L-shell corrections and shell corrections calculated by Bonderup (1967) on the basis of the Thomas-Fe...... found by means of Bonderup's shell corrections. Within the Z2 interval treated here, it is found that I/Z2 increases with increasing Z2, contrary to the general trend through the periodic system of elements......Excitation potentials and shell corrections for the elements Z 2=20 to Z2=30 are evaluated from experimental stopping-power data for 5-12-MeV protons and deuterons. Use is made of Walske's K- and L-shell corrections and shell corrections calculated by Bonderup (1967) on the basis of the Thomas...

  9. Atomic and molecular spectroscopy of transition metals in condensed helium

    International Nuclear Information System (INIS)

    Full text: We investigated laser induced fluorescence spectra of copper and gold atoms and dimers thereof isolated in solid and liquid 4He. Among the atomic spectral lines the most interesting ones are forbidden transitions that involve electrons from inner d-shells which are screened from the surrounding He atoms by the outer s-shell and are therefore much less affected by the interaction with the He matrix. Indeed, the observed spectral lineshapes are much narrower than those of transitions involving outer shell electrons. Another important result is the observation of well resolved vibrational structures in five molecular bands of the Au2 and Cu2 dimers. We expect that the analysis of those spectra will significantly advance our understanding of impurity atoms and molecules in condensed He. (author)

  10. Expert system development (ESD) shell

    International Nuclear Information System (INIS)

    An Expert System Development (ESD) Shell design implementation is desribed in detail. The shell provides high-level generic facilities for Knowledge Representation (KR) and inferencing and tools for developing user interfaces. Powerful set of tools in the shell relieves much of the programming burden in the ES development. The shell is written in PROLOG under IBM PC/AT. KR facilities are based on two very powerful formalisms namely, frames and rules. Inference Engine (IE) draws most of its power from unification and backward reasoning strategy in PROLOG. This basic mechanism is enhanced further by incorporating both forward and backward chaining of rules and frame-based inferencing. Overall programming style integrates multiple paradigms including logic, object oriented, access-oriented and imperative programming. This permits ES designer a lot of flexibility in organizing inference control. Creation and maintainance of knowledge base is a major activity. The shell, therefore, provides number of facilities to simplify these tasks. Shell design also takes note of the fact that final success of any system depends on end-user satisfaction and hence provides features to build use-friendly interfaces. The shell also provides a set of interfacing predicates so that it can be embedded within any PROLOG program to incorporate functionalilty of the shell in the user program. (author). 10 refs., 8 figs

  11. Shell model and spectroscopic factors

    International Nuclear Information System (INIS)

    In these lectures, I introduce the notion of spectroscopic factor in the shell model context. A brief review is given of the present status of the large scale applications of the Interacting Shell Model. The spectroscopic factors and the spectroscopic strength are discussed for nuclei in the vicinity of magic closures and for deformed nuclei. (author)

  12. Strength of protective ferroconcrete shells with an internal explosive load

    International Nuclear Information System (INIS)

    Ferroconcrete cylindrical containment vessels of height equal to the diameter with an elliptical lid are most widely used at Russian atomic power stations. They are designed to withstand the action of internal static pressure. Although the action of explosive internal loads on their internal surface is possible in an accident, no experimental studies of this situation are known. As a first approximation, the integral characteristic K = M/mex used to estimate the permissible explosive load of ferroconcrete explosion chambers was suggested as a first approximation in estimating the dynamic strength of shells under an explosive load; here M is the mass of the shell and mex is the mass of the explosive charge. Practical experience with explosion chambers indicates that they remain intact under multiple explosions if K ≥ 103. In their work, the failure of cylindrical ferroconcrete shells (rings) under an internal explosive load is experimentally studied, and the results are used to predict the explosion stability of the containment vessels of atomic power plants. In the pressure-momentum plane of the load, there are regions corresponding to damage to the ring at three levels: the presence of partial and through cracks and failure of the reinforcement. The boundaries of the regions (isodamage curves) are the geometric loci of all possible combinations of load parameters corresponding to the same final state of the ring on the chosen scale. A procedure has been described for plotting isodamage curves for thin rings of arbitrary radius on the basis of the experimental results. By plotting such curves for the example of a hypothetical cylindrical shell close in size to the cylindrical section of the containment vessel at the fifth unit of the Novo-Voronezh atomic power plant (Ro = 23 m, H = 40 m, σ = 1.2 m), it has been shown that this shell remains intact under the explosion of a TNT charge of mass up to 3.5 ton

  13. 78 FR 25623 - Importation of Fresh Beans, Shelled or in Pods, From Jordan Into the Continental United States

    Science.gov (United States)

    2013-05-02

    ... distributed within the United States. Currently, we do not allow the importation of fresh beans (Phaseolus... accessing Regulations.gov ). The PRA, titled ``Importation of Fresh Beans (Phaseolus vulgaris L.), Shelled... allow the importation of commercial shipments of fresh beans (Phaseolus vulgaris L.), shelled or in...

  14. Composite shell spacecraft seat

    Science.gov (United States)

    Barackman, Victor J. (Inventor); Pulley, John K. (Inventor); Simon, Xavier D. (Inventor); McKee, Sandra D. (Inventor)

    2008-01-01

    A two-part seat (10) providing full body support that is specific for each crew member (30) on an individual basis. The two-part construction for the seat (10) can accommodate many sizes and shapes for crewmembers (30) because it is reconfigurable and therefore reusable for subsequent flights. The first component of the two-part seat construction is a composite shell (12) that surrounds the crewmember's entire body and is generically fitted to their general size in height and weight. The second component of the two-part seat (10) is a cushion (20) that conforms exactly to the specific crewmember's entire body and gives total body support in more complex environment.

  15. Studi Tentang Kandungan Timbal (Pb) Dan Kadmium (Cd) Dalam Wortel (Daucus Carota L) Di Pasar Kota Medan Secara Spektrofotometri Serapan Atom

    OpenAIRE

    Chandra, Deva

    2014-01-01

    Carrot (Daucus carota L.) is a tuber vegetable that has an important role in the provision of food, especially the provision of vitamins and minerals. Carrot contain vitamin A and many other substances which have medicinal effect, so it is favored by the people. Crops especially vegetables, is a mediator for metal absorption. Because of its widespread utilization, carrot should be free of all contaminants that can harm humans, including heavy metals. The purpose of this study was to determin...

  16. Penetapan Kadar Mineral Besi, Magnesium Dan Seng Pada Daun Bangun-Bangun (Plectranthus Amboinicus L.) Segar Dan Yang Direbus Secara Spektrofotometri Serapan Atom

    OpenAIRE

    Pasaribu, Jusia Marluga

    2015-01-01

    Bangun-bangun leaf (Plectranthus amboinicus L.) is a plant that can use as a herb traditional in Indonesia. Batak women who are breastfeeding in Simalungun District, North Sumatera Province, has a tradition of consuming Bangun-bangun leaf in the form of vegetable soap for a month after born. They belive that by consuming the Bangun-bangun leaf soup, milk production will be increase. This Bangun-bangun leaf contain nutrient, especially iron, calsium, zinc, and magnesium. After observation fr...

  17. Thermal stability of Cu@Ag core–shell nanoparticles

    International Nuclear Information System (INIS)

    Highlights: •Thermal stability of Cu@Ag core–shell NPs upon heating was evaluated. •Oxidation of nanoparticles was monitored by synchrotron radiation X-ray diffraction. •Phase transitions and morphological evolution were investigated. •Mechanisms for the coalescence of Cu cores and ripening of Ag shell were explained. -- Abstract: In this study, the structural evolution and oxidation of Cu@Ag core–shell nanoparticle deposits (with average particle diameter of 25 nm and Ag/Cu atomic ratio of 1/8) upon heating in air were investigated quantitatively via in situ synchrotron radiation X-ray diffraction. With an increasing temperature, the coalescence of Cu cores and ripening of Ag shell occurred simultaneously, resulting in discrete Ag nanonodules and unprotected Cu microparticles. Due to the protection of the thin Ag shell, the formation temperatures of the Cu oxides for Cu@Ag NPs were higher than those for pure Cu nanoparticles with similar size by at least 150 °C

  18. Polymer and protein interfacial competition in a shell production process

    Science.gov (United States)

    Willard, Emma; Randall, Greg

    2015-11-01

    We are exploring oil-in-aqueous polymer compound droplet formulations to UV polymerize into shells while in a strong AC electric field (kV/cm, 20 MHz). The electric field drives the drops to adopt a concentric configuration so that a ``perfect'' spherical shell can be polymerized with a uniform wall thickness. In our previous study of oil-in-water droplet centering, we determined that droplet stretching in the electric field was a problem, which we overcame by using protein additives to strengthen the oil/water interface. However, adding polymer to the shell fluid has been shown to weaken the droplet interface and further complicates T junction droplet generation. In this work, we study the adsorption competition between bovine serum albumin and polyethylene glycol diacrylate with the pendant drop method to generate a polymer/protein shell formulation that will resist stretching in the centering electric field. Furthermore, we explore droplet generation of polymer/protein shell formulations in a double T junction and stretching in an electric field. Work supported by General Atomics IR&D funds.

  19. Shell structure of pancakes and the absorption spectra of quasars

    International Nuclear Information System (INIS)

    The formation of the absorption lines of atomic hydrogen in the spectra of distant quasars is considered. A model is constructed of the formation of shells of a pancake formed in the adiabatic picture of the generation of the large-scale structure of the universe. It is shown that the absorption lines can form doublets and the equivalent widths of the corresponding lines are calculated. The physical conditions corresponding to the observed heavy-element absorption spectra are discussed

  20. Use of magnetic core/polymer shell nanoparticles in biomedicine

    Czech Academy of Sciences Publication Activity Database

    Horák, Daniel

    Los Angeles: Cedars-Sinai Medical Center , Department of Neurosurgery, 2015. RECOOP L5. [Nanomedicine for Imaging and Treatment Conference /3./, CSMC - RECOOP Nanomedicine Workshop. 13.03.2015-16.03.2015, Los Angeles] R&D Projects: GA MŠk(CZ) LH14318 Institutional support: RVO:61389013 Keywords : nanoparticles * magnetic * core/shell Subject RIV: CD - Macromolecular Chemistry

  1. Oxidation state specific generation of arsines from methylated arsenicals based on L-cysteine treatment in buffered media for speciation analysis by hydride generation-automated cryotrapping-gas chromatography-atomic absorption spectrometry with the multiatomizer

    International Nuclear Information System (INIS)

    An automated system for hydride generation-cryotrapping-gas chromatography-atomic absorption spectrometry with the multiatomizer is described. Arsines are preconcentrated and separated in a Chromosorb filled U-tube. An automated cryotrapping unit, employing nitrogen gas formed upon heating in the detection phase for the displacement of the cooling liquid nitrogen, has been developed. The conditions for separation of arsines in a Chromosorb filled U-tube have been optimized. A complete separation of signals from arsine, methylarsine, dimethylarsine, and trimethylarsine has been achieved within a 60 s reading window. The limits of detection for methylated arsenicals tested were 4 ng l-1. Selective hydride generation is applied for the oxidation state specific speciation analysis of inorganic and methylated arsenicals. The arsines are generated either exclusively from trivalent or from both tri- and pentavalent inorganic and methylated arsenicals depending on the presence of L-cysteine as a prereductant and/or reaction modifier. A TRIS buffer reaction medium is proposed to overcome narrow optimum concentration range observed for the L-cysteine modified reaction in HCl medium. The system provides uniform peak area sensitivity for all As species. Consequently, the calibration with a single form of As is possible. This method permits a high-throughput speciation analysis of metabolites of inorganic arsenic in relatively complex biological matrices such as cell culture systems without sample pretreatment, thus preserving the distribution of tri- and pentavalent species

  2. Atomic secrecy

    International Nuclear Information System (INIS)

    An article, The H-Bomb Secret: How We Got It, Why We're Telling It, by Howard Morland was to be published in The Progressive magazine in February, 1979. The government, after learning of the author's and the editors' intention to publish the article and failing to persuade them to voluntarily delete about 20% of the text and all of the diagrams showing how an H-bomb works, requested a court injunction against publication. Acting under the Atomic Energy Act of 1954, US District Court Judge Robert W. Warren granted the government's request on March 26. Events dealing with the case are discussed in this publication. Section 1, Progressive Hydrogen Bomb Case, is discussed under the following: Court Order Blocking Magazine Report; Origins of the Howard Morland Article; Author's Motives, Defense of Publication; and Government Arguments Against Disclosure. Section 2, Access to Atomic Data Since 1939, contains information on need for secrecy during World War II; 1946 Atomic Energy Act and its effects; Soviet A-Bomb and the US H-Bomb; and consequences of 1954 Atomic Energy Act. Section 3, Disputed Need for Atomic Secrecy, contains papers entitled: Lack of Studies on H-Bomb Proliferation; Administration's Position on H-Bombs; and National Security Needs vs Free Press

  3. Ion-atom collisions study by cross section measurement of K and L X-ray production with 100 to 300 keV heavy particles

    International Nuclear Information System (INIS)

    Aluminium and copper targets have been irradiated by 100-250 keV protons and 250 keV Ne+ and Ar+ ions. Total cross section for the K and L X-ray emission have been measured and the ionisation mechanism is discussed. Transitions which are forbidden in the framework of the initial orbital molecular formalism have been observed; some hypothesis and specially the so called solid effects have been suggested to explain their presence. In the conclusion it is shown that, in a next future, the solid effects will be eliminated by using a gazeous stream which has been realized during the present work

  4. 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

  5. Manipulation of individual double-walled carbon nanotubes packed in a casing shell

    International Nuclear Information System (INIS)

    Controlled placement of carbon nanotubes is important for carbon-based nanodevice assembly. However, it is difficult to manipulate individual nanotubes because of their extremely small dimensions. Ultra-fine tubes are often in the form of bundles and are hard to efficiently move on a surface due to the strong adhesion among themselves and between the tubes and the substrate. This paper presents a novel manipulation approach of individual double-walled carbon nanotubes encased in a thick amorphous carbon shell. With an atomic force microscope, we are able to freely displace the nanotubes within a casing shell, and unpack it from the shell on a silicon surface. The theoretical analysis demonstrates that the unpacking process is determined by the difference of the static friction between the shell and the substrate and the resistance force between the shell and the embedded nanotube.

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

    International Nuclear Information System (INIS)

    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.

  7. A novel method for measuring K-shell photoelectric parameters of high-Z elements

    Science.gov (United States)

    Nayak, S. V.; Badiger, N. M.

    2006-06-01

    The K-shell jump ratio, jump factor and the ratio of total to K-shell photoelectric cross section at K edge have been determined for Hf, Ta, Au and Pb by adopting a novel method. In this method, continuous external bremsstrahlung (EB) photons are produced in a thin nickel elemental converter by beta particles from a 90Sr-90Y weak beta source. The spectrum of EB photons transmitted through the elemental targets of Hf, Ta, Au and Pb is recorded with an HPGe detector coupled to an 8K multichannel analyser. The transmitted spectrum shows a sharp decrease in intensity at the K-shell binding energy of the target atom. The region of sharp decrease is fitted to a sigmoidal function and the K-shell jump ratio, jump factor and the ratio of total to the K-shell photoelectric cross section at K edge are determined. The measured values are compared with the theoretical values.

  8. 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.

  9. Characterising the surface and interior chemistry of core-shell nanoparticles using scanning transmission electron microscopy

    International Nuclear Information System (INIS)

    A method for extracting core and shell spectra from core-shell particles with varying core to shell volume fractions is described. The method extracts the information from a single EELS spectrum image of the particle. The distribution of O and N was correctly reproduced for a nanoparticle with a TiN core and Ti-oxide shell. In addition, the O distribution from a nanoparticle with a Cu core and a Cu-oxide shell was obtained, and the extracted Cu L2,3-core and shell spectra showed the required change in EELS near edge fine structure. The extracted spectra can be used for multiple linear least squares fitting to the raw data in the spectrum image. The effect of certain approximations on numerical accuracy, such as treating the nanoparticle as a perfect sphere, as well as the intrinsic detection limits of the technique have also been explored. The technique is most suitable for qualitative, rather than quantitative, work. -- Research Highlights: → A new method for extracting core and shell EELS spectra from a core-shell nanoparticle is developed. → The technique utilises spectrum imaging in a scanning transmission electron microscope (STEM). → The composition and bonding environment at the core and shell regions can be analysed.→ The method is applied to TiN/Ti-oxide and Cu/Cu-oxide core-shell nanoparticles.→ Numerical accuracy and intrinsic limits of the technique are also discussed.

  10. 1: the atom. 2: radioactivity. 3: man and radiations. 4: the energy. 5: nuclear energy: fusion and fission. 6: the operation of a nuclear reactor. 7: the nuclear fuel cycle; 1: l'atome. 2: la radioactivite. 3: l'homme et les rayonnements. 4: l'energie. 5: l'energie nucleaire: fusion et fission. 6: le fonctionnement d'un reacteur nucleaire. 7: le cycle du combustible nucleaire

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2002-07-01

    This series of 7 digest booklets present the bases of the nuclear physics and of the nuclear energy: 1 - the atom (structure of matter, chemical elements and isotopes, the four fundamental interactions, nuclear physics); 2 - radioactivity (definition, origins of radioelements, applications of radioactivity); 3 - man and radiations (radiations diversity, biological effects, radioprotection, examples of radiation applications); 4 - energy (energy states, different forms of energy, characteristics); 5 - nuclear energy: fusion and fission (nuclear energy release, thermonuclear fusion, nuclear fission and chain reaction); 6 - operation of a nuclear reactor (nuclear fission, reactor components, reactor types); 7 - nuclear fuel cycle (nuclear fuel preparation, fuel consumption, reprocessing, wastes management). (J.S.)

  11. Novel copper (Cu) loaded core-shell silica nanoparticles with improved Cu bioavailability: synthesis, characterization and study of antibacterial properties.

    Science.gov (United States)

    Maniprasad, Pavithra; Santra, Swadeshmukul

    2012-08-01

    We report synthesis of a novel core-shell silica based antimicrobial nanoparticles where the silica shell has been engineered to accommodate copper (Cu). Synthesis of the core-shell Cu-silica nanoparticle (C-S CuSiO2NP) involves preparation of base-hydrolyzed Stöber silica "seed" particles first, followed by the acid-catalyzed seeded growth of the Cu-silica shell layer around the core. The Scanning Electron Microscopy (SEM) and the Transmission Electron Microscopy (TEM) measured the seed particle size to be -380 nm and the shell thickness to be -35 nm. The SEM particle characterization confirms formation of highly monodispersed particles with smooth surface morphology. Characterization of particle size distribution in solution by Dynamic Light Scattering (DLS) technique was fairly consistent with the electron microscopy results. Loading of Cu to nanoparticles was confirmed by the SEM-Energy Dispersive X-Ray Spectroscopy (EDS) and Atomic Absorption Spectroscopy (AAS). The Cu loading was estimated to be 0.098 microg of metallic copper per mg of C-S CuSiO2NP material by the AAS technique. Antibacterial efficacy of C-S CuSiO2NP was evaluated against E. coli and B. subtilis using Cu hydroxide ("Insoluble" Cu compound, sub-micron size particles) as positive control and silica "seed" particles (without Cu loading) as negative control. Bacterial growth in solution was measured against different concentrations of C-S CuSiO2NP to determine the Minimum Inhibitory Concentration (MIC) value. The estimated MIC values were 2.4 microg metallic Cu/mL for both E. coli and B. subtilis. Bac-light fluorescence microscopy based assay was used to count relative population of the live and dead bacteria cells. Antibacterial study clearly shows that C-S CuSiO2NP is more effective than insoluble Cu hydroxide particles at equivalent metallic Cu concentration, suggesting improvement of Cu bioavailability (i.e., more soluble Cu) in C-SCuSiO2NP material due to its core-shell design. PMID

  12. Synthesis of Core-Shell SiOx/Carbon Nano fibers on Silicon Substrates by Ultrasonic Spray Pyrolysis

    International Nuclear Information System (INIS)

    We synthesized the core-shell SiOx/carbon nano fibers with diameters of 200-300 nm using ultrasonic spray pyrolysis with a phosphorus/ethanol mixture. High-resolution transmission electron microscopy (HRTEM) and energy-dispersive spectroscopy (EDS) investigations confirmed the core-shell structure, which consisted of a core of SiOx and a shell of amorphous carbon. The phosphorus atoms corroded the entire silicon substrate surface, and the Si-P liquid-catalyzed the solid-liquid-solid mechanism is proposed to explain the growth of the core-shell SiOx/carbon nano fibers.

  13. Calculation of Al-Zn diagram from central atoms model

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    A slightly modified central atoms model was proposed. The probabilities of various clusters with the central atoms and their nearest neighboring shells can be calculated neglecting the assumption of the param eter of energy in the central atoms model in proportion to the number of other atoms i (referred with the central atom). A parameter Pα is proposed in this model, which equals to reciprocal of activity coefficient of a component, therefore, the new model can be understood easily. By this model, the Al-Zn phase diagram and its thermodynamic properties were calculated, the results coincide with the experimental data.

  14. Optimum rotationally symmetric shells for flywheel rotors

    Science.gov (United States)

    Blake, Henry W.

    2000-01-01

    A flywheel rim support formed from two shell halves. Each of the shell halves has a disc connected to the central shaft. A first shell element connects to the disc at an interface. A second shell element connects to the first shell element. The second shell element has a plurality of meridional slits. A cylindrical shell element connects to the second shell element. The cylindrical shell element connects to the inner surface of the flywheel rim. A flywheel rim support having a disc connected an outer diameter of a shaft. Two optimally shaped shell elements connect to the optimally shaped disc at an interface. The interface defines a discontinuity in a meridional slope of said support. A cylindrical shell element connects to the two shell elements. The cylindrical shell element has an outer surface for connecting to the inner surface of the flywheel rim. A flywheel rim casing includes an annular shell connected to the central shaft. The annular shell connects to the flywheel rim. A composite shell surrounds the shaft, annular shell and flywheel rim.

  15. 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

  16. Dynamical symmetries of the shell model

    International Nuclear Information System (INIS)

    The applications of spectrum generating algebras and of dynamical symmetries in the nuclear shell model are many and varied. They stretch back to Wigner's early work on the supermultiplet model and encompass important landmarks in our understanding of the structure of the atomic nucleus such as Racah's SU(2) pairing model and Elliot's SU(3) rotational model. One of the aims of this contribution has been to show the historical importance of the idea of dynamical symmetry in nuclear physics. Another has been to indicate that, in spite of being old, this idea continues to inspire developments that are at the forefront of today's research in nuclear physics. It has been argued in this contribution that the main driving features of nuclear structure can be represented algebraically but at the same time the limitations of the symmetry approach must be recognised. It should be clear that such approach can only account for gross properties and that any detailed description requires more involved numerical calculations of which we have seen many fine examples during this symposium. In this way symmetry techniques can be used as an appropriate starting point for detailed calculations. A noteworthy example of this approach is the pseudo-SU(3) model which starting from its initial symmetry Ansatz has grown into an adequate and powerful description of the nucleus in terms of a truncated shell model. (author)

  17. Dynamical symmetries of the shell model

    Energy Technology Data Exchange (ETDEWEB)

    Van Isacker, P

    2000-07-01

    The applications of spectrum generating algebras and of dynamical symmetries in the nuclear shell model are many and varied. They stretch back to Wigner's early work on the supermultiplet model and encompass important landmarks in our understanding of the structure of the atomic nucleus such as Racah's SU(2) pairing model and Elliot's SU(3) rotational model. One of the aims of this contribution has been to show the historical importance of the idea of dynamical symmetry in nuclear physics. Another has been to indicate that, in spite of being old, this idea continues to inspire developments that are at the forefront of today's research in nuclear physics. It has been argued in this contribution that the main driving features of nuclear structure can be represented algebraically but at the same time the limitations of the symmetry approach must be recognised. It should be clear that such approach can only account for gross properties and that any detailed description requires more involved numerical calculations of which we have seen many fine examples during this symposium. In this way symmetry techniques can be used as an appropriate starting point for detailed calculations. A noteworthy example of this approach is the pseudo-SU(3) model which starting from its initial symmetry Ansatz has grown into an adequate and powerful description of the nucleus in terms of a truncated shell model. (author)

  18. K-shell Photoabsorption of Oxygen Ions

    CERN Document Server

    García, J; Bautista, M A; Gorczyca, T W; Kallman, T R; Palmeri, P

    2004-01-01

    Extensive calculations of the atomic data required for the spectral modelling of the K-shell photoabsorption of oxygen ions have been carried out in a multi-code approach. The present level energies and wavelengths for the highly ionized species (electron occupancies 2 4, lack of measurements, wide experimental scatter, and discrepancies among theoretical values are handicaps in reliable accuracy assessments. The radiative and Auger rates are expected to be accurate to 10% and 20%, respectively, except for transitions involving strongly mixed levels. Radiative and Auger dampings have been taken into account in the calculation of photoabsorption cross sections in the K-threshold region, leading to overlapping lorentzian shaped resonances of constant widths that cause edge smearing. The behavior of the improved opacities in this region has been studied with the XSTAR modelling code using simple constant density slab models, and is displayed for a range of ionization parameters.

  19. Atomic theories

    CERN Document Server

    Loring, FH

    2014-01-01

    Summarising the most novel facts and theories which were coming into prominence at the time, particularly those which had not yet been incorporated into standard textbooks, this important work was first published in 1921. The subjects treated cover a wide range of research that was being conducted into the atom, and include Quantum Theory, the Bohr Theory, the Sommerfield extension of Bohr's work, the Octet Theory and Isotopes, as well as Ionisation Potentials and Solar Phenomena. Because much of the material of Atomic Theories lies on the boundary between experimentally verified fact and spec

  20. Evolution of three-shell onion-like and core-shell structures in (AgCo)201 bimetallic clusters

    Institute of Scientific and Technical Information of China (English)

    Wang Qiang; Li Guo-Jian; Li Dong-Gang; Lv Xiao; He Ji-Cheng

    2009-01-01

    This paper studies the structural evolution of (AgCo)201 clusters with different Co concentrations under various temperature conditions by using molecular dynamics with the embedded atom method. The most stable position for Co atoms in the cluster is the subsurface layer at low temperature (lower than 200 K for the Ag200Co1 cluster). The position changes to the core layer with the increase of temperature, but there is an energy barrier in the middle layer. This makes the Ag-Co cluster form an Ag-Co-Ag three-shell onion-like configuration. When the temperature is high enough [higher than 800 K for (AgCo)201 clusters with 50% Co], Co atoms can obtain enough energy to overcome the energy barrier and the duster forms an Ag-Co core-shell configuration. Amorphization for the onion-like and core-shell clusters is induced by the large lattice misfit at Ag-Co interfaces. The structural evolution in the Ag-Co cluster is related to the release of excess energy.