WorldWideScience

Sample records for atomic shells m

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. 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

  6. 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.

  7. 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

  8. 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

  9. 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.

  10. 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

  11. 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)

  12. 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

  13. 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.

  14. 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.

  15. 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.

  16. 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...

  17. 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

  18. 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.

  19. 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.

  20. 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.

  1. 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)

  2. New empirical formulae for calculation of average M-shell fluorescence yields

    International Nuclear Information System (INIS)

    We have calculated and reviewed in a table form the average bulk M-shell fluorescence yield previously measured by different groups covering the period from 1955 to 2005. We have interpolated the weighted and unweighted mean values of the experimental data by using the analytical function (ω¯M/(1−ω¯M))1/4 as a function of the atomic number (Z) to deduce the empirical average M-shell fluorescence yield in the atomic range of 70≤Z≤92. Also, we used the famous formula ω¯M=A(Z−13)4 to generalize the average M-shell fluorescence yield for elements with 19≤Z≤100. The results have been compared with other theoretical, experimental and empirical values reported in the literature and a reasonable agreement has been obtained. - Highlights: • The collected average M-shell fluorescence yields cover the period from 1955 to 2005. • Three procedures are followed to deduce the average M-shell fluorescence yield. • The obtained results are compared with others works. • Reasonable agreement was typically obtained between our result and other works

  3. 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...

  4. 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.

  5. 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.

  6. Endohedral metallofullerenes, M@C60 (M = Ca, Na, Sr): selective adsorption and sensing of open-shell NOx gases.

    Science.gov (United States)

    Tawfik, Sherif Abdulkader; Cui, X Y; Ringer, S P; Stampfl, C

    2016-08-21

    Based on density-functional theory and non-equilibrium Green's function calculations, we demonstrate that endohedral metallofullerenes (EMFs) are reactive to open-shell gases, and therefore have the potential application as selective open-shell gas sensors. The adsorption of eight gas species (CO, H2O, H2S, NO2, NO, SO2, O2 and NH3) on three EMFs (M@C60, M = Ca, Na and Sr) shows that the adsorption energies of the EMFs towards NO2 and NO are significantly higher than the closed-shell species. Moreover, the high selectivity appears relatively insensitive to the inserted metal atoms. The calculated current-voltage characteristics of gold-M@C60-gold structures (M = Ca, Na) show that the adsorption of NO2 leads to significant change in conductivity, suggesting a potential application as an EMF gas resistive sensing device. PMID:27426253

  7. Average M shell fluorescence yields for elements with 70≤Z≤92

    International Nuclear Information System (INIS)

    The theoretical, experimental and analytical methods for the calculation of average M-shell fluorescence yield (ω¯M) of different elements are very important because of the large number of their applications in various areas of physical chemistry and medical research. In this paper, the bulk of the average M-shell fluorescence yield measurements reported in the literature, covering the period 1955 to 2005 are interpolated by using an analytical function to deduce the empirical average M-shell fluorescence yield in the atomic range of 70≤Z≤92. The results were compared with the theoretical and fitted values reported by other authors. Reasonable agreement was typically obtained between our result and other works

  8. Average M shell fluorescence yields for elements with 70≤Z≤92

    Energy Technology Data Exchange (ETDEWEB)

    Kahoul, A., E-mail: ka-abdelhalim@yahoo.fr [Department of Materials Science, Faculty of Sciences and Technology, Mohamed El Bachir El Ibrahimi University, Bordj-Bou-Arreridj 34030 (Algeria); LPMRN laboratory, Department of Materials Science, Faculty of Sciences and Technology, Mohamed El Bachir El Ibrahimi University, Bordj-Bou-Arreridj 34030 (Algeria); Deghfel, B. [Physics Department, Faculty of Sciences, M’Sila University, 28000 M’Sila (Algeria); Laboratory of materials physics and their applications, Physics Department, Faculty of Sciences, University of Mohamed Boudiaf, 28000 M’sila (Algeria); Aylikci, V. [Department of Metallurgical and Materials Engineering, Faculty of Technology, Mustafa Kemal University, Hatay 31040 (Turkey); Aylikci, N. K. [Department of Physics, Faculty of Sciences, Karadeniz Technical University, Trabzon 61080,Turkey (Turkey); Nekkab, M. [Physics Department, Faculty of Sciences, M’Sila University, 28000 M’Sila (Algeria); LESIMS laboratory, Faculty of Sciences, Ferhat Abbas University, Setif,19000 (Algeria)

    2015-03-30

    The theoretical, experimental and analytical methods for the calculation of average M-shell fluorescence yield (ω{sup ¯}{sub M}) of different elements are very important because of the large number of their applications in various areas of physical chemistry and medical research. In this paper, the bulk of the average M-shell fluorescence yield measurements reported in the literature, covering the period 1955 to 2005 are interpolated by using an analytical function to deduce the empirical average M-shell fluorescence yield in the atomic range of 70≤Z≤92. The results were compared with the theoretical and fitted values reported by other authors. Reasonable agreement was typically obtained between our result and other works.

  9. 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

  10. 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.

  11. 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...

  12. 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)

  13. 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)

  14. 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

  15. 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)

  16. 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.)

  17. 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.)

  18. 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...

  19. 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...

  20. 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.

  1. 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.

  2. 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)

  3. 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.

  4. 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)

  5. 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

  6. 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...

  7. 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...

  8. 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...

  9. 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)

  10. 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)

  11. Experimental Study on Performance of Concrete M30 with Partial Replacement of Coarse Aggregate with Sea Shells and Coconut Shells

    Directory of Open Access Journals (Sweden)

    Gurikini Lalitha

    2014-08-01

    Full Text Available In this research work experiments have been conducted with collection of materials required and the data required for mix design are obtained by sieve analysis and specific gravity test. Sieve analysis is carried out from various fine aggregates (FA and coarse aggregates (CA samples and the sample which suits the requirement is selected. Specific gravity tests are carried out for fine and coarse aggregate. The various materials used were tested as per Indian standard specifications. On the basis of the experimental studies carried out on M30 grade concrete as partial replacement of coarse aggregates with sea shells and coconut shells, the following conclusions are drawn from the above experiment we conclude that comparing to traditional concrete, compressive strength of 10% (5% + 5% of coconut shells (5% and sea shells (5% increased. whereas the compressive strength of the concrete cubes has gradually decreased from addition of 10% (5% + 5% of coconut shells and sea shells. Hence for economical view 10% is preferable and in the perspective of compressive strength 10% is suggested. Thus, 10% replacement coconut shells and sea shells are recommended for both heavy weight and light weight concrete production.

  12. Structure, energetic and phase transition of multi shell icosahedral bimetallic nanostructures: A molecular dynamics study of Ni{sub m}Pd{sub n} (n + m = 55 and 147)

    Energy Technology Data Exchange (ETDEWEB)

    Hewage, Jinasena W., E-mail: jinasena@chem.ruh.ac.lk

    2015-01-15

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

  13. 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.

  14. 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)

  15. 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.

  16. 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.

  17. 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.

  18. 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)

  19. 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)

  20. 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)

  1. 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

  2. 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

  3. 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...

  4. 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.

  5. 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

  6. 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.

  7. 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.

  8. 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...

  9. 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.

  10. 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

  11. 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.

  12. 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

  13. 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.

  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. 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.

  16. 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

  17. 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

  18. 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

  19. Integrated shell approach to vertical position control on PBX-M

    International Nuclear Information System (INIS)

    The PBX-M device produces highly shaped discharges that, because of the negative external magnetic field decay index required, are vertically unstable. Vertical positional stability in PBX-M has been achieved by directly controlling the n = 0 component of the eddy current in the passive shell instead of the commonly used function of magnetic flux signals. Because the active coil is controlled via currents in the passive shell we call this an ''integrated shell'' approach to vertical position control. We present results of these experiments and make comparisons between the two methods of control

  20. 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)

  1. 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 .

  2. 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)

  3. 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.)

  4. 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...

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. M-shell X-ray production cross sections for PIXE applications

    International Nuclear Information System (INIS)

    M-shell X-ray production cross sections by protons of energies 0.1-4.0 MeV are reported for the most intense Mαβ(M4,5N6,7), Mγ(M3N4,5) and M3O4,5 M-X ray transitions appearing in PIXE spectra. The cross sections have been measured systematically for selected heavy elements between Ta and Th (Z2=73-90). Measured M-X-ray production cross sections were found to be universal with respect of M-shell scaled velocity ξM. The data are compared with available theoretical calculations of M-shell ionization by charged particles based on the plane-wave Born approximation (PWBA) and the semiclassical approximation (SCA), as well as the ECPSSR theory and relativistic RPWBA-BC which are going beyond the first order treatment. Simple parameterization of experimental proton induced M-X-ray cross sections is proposed for PIXE applications. This parameterization, being accurate within ±5%, can be used for precise determination of heavy metal concentrations by PIXE technique

  10. 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)

  11. 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

  12. 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

  13. 13m cantilever retaining wall with arch effect of cylindrical shell; Ento shell no arch koka wo riyo shita fukasa 13m no jiritsu yamadome heki

    Energy Technology Data Exchange (ETDEWEB)

    Maeda, T.; Matsuura, N. [Obayashigumi Research Inst., Tokyo (Japan)

    1997-10-01

    Concerning the Sub-Arena being a part of the Osaka City Central Gymnasium which acted as the main meeting place of `Namihaya Athletics Meet` in 1997, its construction and results of predictive analyses were introduced in this paper. This area (Maishima isle) is covered with reclaimed soil until -6m in ground line (GL) and then with clay layer until -36m. The lower part from the above line is gravel layer, and the natural water level is GL-3m. Though the spherical shell roof assembled by PC can be found on the ground, the main body is a cylindrical earth self-retaining wall whose upper fringe is 0m in GL. The wall was composed of RC elements (thickness 1.2m) and made up a circle whose dia. was 52m by means of connection applying rigid joints. Though the bottom surface was GL-13m, the wall whose overall height was 39m was penetrated into gravel layer. Regarding predictive analyses for stress and deformation at the time of excavation, calculation factors were decided in accordance with guide-lines for basic design about underground connected wall by Obayashi-gumi Ltd. and the Japan Road Association. Deformation of the face of wall has been about 30mm at maximum at the most upper part whose value was about three times of analyzed value, and also increased about 5mm by the Hanshin earthquake. 3 refs., 12 figs.

  14. 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

  15. 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 ...

  16. Shell-like structure in 41.9 + 58, a powerful supernova remnant in M82

    International Nuclear Information System (INIS)

    An EVN map of the compact radio source 41.9 + 58 in M82 reveals a distorted shell-like structure with dimensions 0.56 x 0.32 pc. This map, together with a limit on the present expansion velocity and the steady decay of the flux density convinces us that 41.9 + 58 is a powerful supernova remnant whose progenitor probably exploded 40-50 yr ago. (author)

  17. 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.

  18. Ytterbium to thorium semi-empirical average M-shell fluorescence yields

    International Nuclear Information System (INIS)

    By using the weighted and unweighted mean values of the experimental average M-shell fluorescence yield reported in the literature covering the period from 1955 to 2005 and the theoretical values based on the non-relativistic Hartree–Fock–Slater (HFS) calculations of McGuire (1972), we produce good estimations for the semi-empirical values of elements in the range of 70≤Z≤90. These values are obtained by the interpolation of the normalized weighted and unweighted mean values to their corresponding theoretical ones. The results have been compared to other theoretical, empirical and experimental data reported in the literature. Reasonable agreement has been obtained between our result and other works. - Highlights: • The average M-shell fluorescence yields covering the period from 1955 to 2005 are used. • We used the weighted and unweighted mean values to deduce the semi-empirical average M-shell fluorescence yield. • The obtained results are compared with others works. • Reasonable agreement was typically obtained between our result and other works

  19. M-shell satellite structure of 74W x-ray emission lines

    International Nuclear Information System (INIS)

    The spectra of the x-ray emission lines have a complex structure due to the presence of additional holes in the outer shell, which accompany the main transition. The additional holes are called spectator holes, and the induced transitions which are slightly shifted, usually on the higher energy side of the diagram line, are called satellite lines. Although the origin of these satellite lines can been explained by various mechanisms, there are few experimental studies which actually consider the presence of the satellite lines in the spectra on a theoretical ground. Compared to L-shell x-ray emission spectra, the spectra of M-shell x-ray spectra have a far more complicated structure, as the spectator holes can be created by an increased number of channels, such as shake-off, Auger, Coster-Kronig and super-Coster-Kronig transitions. In the present work we attempt to identify the contribution of the Coster-Kronig induced satellites in the M-shell spectra of 74W, both experimentally and theoretically. The 74W Mα,β emission lines generated by electron bombardment from a rotary target x-ray generator were measured by a high resolution single crystal spectrometer, using the (400) plane of a RAP single crystal. The spectra were fitted into Lorentzians; the satellite structure observed on the higher energy side of the corresponding diagram line in a energy range of 2-18 eV, is compared with the experimental results obtained by Munier. In order to identify the transition of the satellites, the transition energy was calculated by means of relativistic density-functional calculations for the case of single spectator holes which can accompany the diagram transition by subsequent Coster-Kronig transitions. The Coster-Kronig induced satellites have been found to be very close to their parent line (0.7 - 4.4 eV). The higher energy satellite structure which goes up to 18 eV apart from the parent line is considered to be due to M-shell spectator holes which can be created mainly

  20. 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.

  1. 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

  2. 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.

  3. 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.

  4. 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

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

    International Nuclear Information System (INIS)

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

  6. 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. 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.

  8. Off-shell M5 brane, perturbed Seiberg-Witten theory, and metastable vacua

    International Nuclear Information System (INIS)

    We demonstrate that, in an appropriate limit, the off-shell M5-brane worldvolume action effectively captures the scalar potential of Seiberg-Witten theory perturbed by a small superpotential and, consequently, any nonsupersymmetric vacua that it describes. This happens in a similar manner to the emergence from M5's of the scalar potential describing certain type IIB flux configurations [J. Marsano, K. Papadodimas, M. Shigemori, Nonsupersymmetric brane/antibrane configurations in type IIA and M theory, Nucl. Phys. B 789 (2008) 294, (arXiv: 0705.0983 [hep-th])]. We then construct exact nonholomorphic M5 configurations in the special case of SU(2) Seiberg-Witten theory deformed by a degree six superpotential which correspond to the recently discovered metastable vacua of Ooguri, Ookouchi, Park [H. Ooguri, Y. Ookouchi, C.S. Park, Metastable vacua in perturbed Seiberg-Witten theories, (arXiv: 0704.3613 [hep-th])], and Pastras [G. Pastras, Non-supersymmetric metastable vacua in N=2 SYM softly broken to N=1, (arXiv: 0705.0505 [hep-th])]. These solutions take the approximate form of a holomorphic Seiberg-Witten geometry with harmonic embedding along a transverse direction and allow us to obtain geometric intuition for local stability of the gauge theory vacua. As usual, dynamical processes in the gauge theory, such as the decay of nonsupersymmetric vacua, take on a different character in the M5 description which, due to issues of boundary conditions, typically involves runaway behavior in MQCD

  9. Three supernova shells around a young star cluster in M33

    CERN Document Server

    Camps-Fariña, Artemi; Font, Joan; Borlaff, Alejandro; Zaragoza-Cardiel, Javier; Amram, Philippe

    2016-01-01

    Using a specialized technique sensitive to the presence of expanding ionized gas we have detected a set of three concentric expanding shells in an HII region in the nearby spiral galaxy M33. After mapping the kinematics in H{\\alpha} with Fabry-Perot spectroscopy we used slit spectra to measure the intensities of the [SII] doublet at {\\lambda}{\\lambda} 671.9, 673.1 nm and the [NII] doublet at {\\lambda}{\\lambda} 645.8, 658.3 nm to corroborate the kinematics and apply diagnostic tests using line ratios. These showed that the expanding shells are shock dominated as would be the case if they had originated with supernova explosions. Estimating their kinetic energies we find fairly low values, indicating a fairly advanced stage of evolution. We obtain density, mass and parent star mass estimates, which, along with the kinetic energies, are inconsistent with the simplest models of shock-interstellar medium interaction. We propose that the presence and properties of an inhomogeneous medium offer a scenario which can ...

  10. 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)

  11. Atomic mechanisms of formation and structure relaxation of Fe83M17 (M: C, B, P) metallic glass

    International Nuclear Information System (INIS)

    The individual characteristic properties of local atomic ordering of structure forming in Fe83M17 (M: C, B, P) metallic glass have been indicated by a computer simulation method. It is proved that carbon atoms 'prefer' to take up the interstitial positions in atomic configurations based on a distorted octahedron and trigonal prism while boron atoms tend to occupy the centres of a distorted Archymedian antiprism. Phosphorus atoms are able to take up both the interstitial and the substitutional positions and the short-range ordering around them is mainly icosahedrical. The interrelationship between the atomic structure of Fe83M17 (M: C, B, P) amorphous metallic alloys and their vitrification ability has been determined

  12. 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

  13. Nonquenched Isoscalar Spin-M1 Excitations in sd-Shell Nuclei.

    Science.gov (United States)

    Matsubara, H; Tamii, A; Nakada, H; Adachi, T; Carter, J; Dozono, M; Fujita, H; Fujita, K; Fujita, Y; Hatanaka, K; Horiuchi, W; Itoh, M; Kawabata, T; Kuroita, S; Maeda, Y; Navrátil, P; von Neumann-Cosel, P; Neveling, R; Okamura, H; Popescu, L; Poltoratska, I; Richter, A; Rubio, B; Sakaguchi, H; Sakaguchi, S; Sakemi, Y; Sasamoto, Y; Shimbara, Y; Shimizu, Y; Smit, F D; Suda, K; Tameshige, Y; Tokieda, H; Yamada, Y; Yosoi, M; Zenihiro, J

    2015-09-01

    Differential cross sections of isoscalar and isovector spin-M1 (0(+)→1(+)) transitions are measured using high-energy-resolution proton inelastic scattering at E(p)=295  MeV on (24)Mg, (28)Si, (32)S, and (36)Ar at 0°-14°. The squared spin-M1 nuclear transition matrix elements are deduced from the measured differential cross sections by applying empirically determined unit cross sections based on the assumption of isospin symmetry. The ratios of the squared nuclear matrix elements accumulated up to E(x)=16  MeV compared to a shell-model prediction are 1.01(9) for isoscalar and 0.61(6) for isovector spin-M1 transitions, respectively. Thus, no quenching is observed for isoscalar spin-M1 transitions, while the matrix elements for isovector spin-M1 transitions are quenched by an amount comparable with the analogous Gamow-Teller transitions on those target nuclei. PMID:26382672

  14. 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

  15. 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.

  16. 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)

  17. 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...

  18. Synthesis of Co/MFe2O4 (M=Fe, Mn) core/shell nanocomposite particles

    International Nuclear Information System (INIS)

    Monodispersed cobalt nanoparticles (NPs) with controllable size (8-14 nm) have been synthesized using thermal decomposition of dicobaltoctacarbonyl in organic solvent. The as-synthesized high magnetic moment (125 emu/g) Co NPs are dispersible in various organic solvents, and can be easily transferred into aqueous phase by surface modification using phospholipids. However, the modified hydrophilic Co NPs are not stable as they are quickly oxidized, agglomerated in buffer. Co NPs are stabilized by coating the MFe2O4 (M=Fe, Mn) ferrite shell. Core/shell structured bimagnetic Co/MFe2O4 nanocomposites are prepared with tunable shell thickness (1-5 nm). The Co/MFe2O4 nanocomposites retain the high magnetic moment density from the Co core, while gaining chemical and magnetic stability from the ferrite shell. Compared to Co NPs, the nanocomposites show much enhanced stability in buffer solution at elevated temperatures, making them promising for biomedical applications. - Graphical abstract: The 10 nm/3 nm Co/MFe2O4 (M=Fe, Mn) bimagnetic core/shell nanocomposites are synthesized from the surface coating of ferrite shell over 10 nm Co nanoparticle seeds. The nanocomposites show much enhanced chemical and magnetic stability in solid state, organic solution and aqueous phase, and are promising for biomedical applications

  19. 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)

  20. Francis M. Pipkin Award Talk - Precision Measurement with Atom Interferometry

    Science.gov (United States)

    Müller, Holger

    2015-05-01

    Atom interferometers are relatives of Young's double-slit experiment that use matter waves. They leverage light-atom interactions to masure fundamental constants, test fundamental symmetries, sense weak fields such as gravity and the gravity gradient, search for elusive ``fifth forces,'' and potentially test properties of antimatter and detect gravitational waves. We will discuss large (multiphoton-) momentum transfer that can enhance sensitivity and accuracy of atom interferometers several thousand fold. We will discuss measuring the fine structure constant to sub-part per billion precision and how it tests the standard model of particle physics. Finally, there has been interest in light bosons as candidates for dark matter and dark energy; atom interferometers have favorable sensitivity in searching for those fields. As a first step, we present our experiment ruling out chameleon fields and a broad class of other theories that would reproduce the observed dark energy density.

  1. 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...

  2. 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

  3. 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.

  4. 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

  5. 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)

  6. 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.

  7. Wooden shell of M2-F1 being assembled at El Mirage

    Science.gov (United States)

    1962-01-01

    Wooden shell of the M2-F1 being assembled at El Mirage, CA. While Flight Research Center technicians built the internal steel structure of the M2-F1, sailplane builder Gus Briegleb built the vehicle's outer wooden shell. Its skin was 3/32-inch mahogany plywood, with 1/8-inch mahogany rib sections reinforced with spruce. The wingless, lifting body aircraft design was initially conceived as a means of landing an aircraft horizontally after atmospheric reentry. The absence of wings would make the extreme heat of re-entry less damaging to the vehicle. In 1962, Dryden management approved a program to build a lightweight, unpowered lifting body as a prototype to flight test the wingless concept. It would look like a 'flying bathtub,' and was designated the M2-F1, the 'M' referring to 'manned' and 'F' referring to 'flight' version. It featured a plywood shell placed over a tubular steel frame crafted at Dryden. Construction was completed in 1963. The first flight tests of the M2-F1 were over Rogers Dry Lake at the end of a tow rope attached to a hopped-up Pontiac convertible driven at speeds up to about 120 mph. This vehicle needed to be able to tow the M2-F1 on the Rogers Dry Lakebed adjacent to NASA's Flight Research Center (FRC) at a minimum speed of 100 miles per hour. To do that, it had to handle the 400-pound pull of the M2-F1. Walter 'Whitey' Whiteside, who was a retired Air Force maintenance officer working in the FRC's Flight Operations Division, was a dirt-bike rider and hot-rodder. Together with Boyden 'Bud' Bearce in the Procurement and Supply Branch of the FRC, Whitey acquired a Pontiac Catalina convertible with the largest engine available. He took the car to Bill Straup's renowned hot-rod shop near Long Beach for modification. With a special gearbox and racing slicks, the Pontiac could tow the 1,000-pound M2-F1 110 miles per hour in 30 seconds. It proved adequate for the roughly 400 car tows that got the M2-F1 airborne to prove it could fly safely and to

  8. Kinetic evaluation of new generation of column packed with 1.3 μm core-shell particles.

    Science.gov (United States)

    Fekete, Szabolcs; Guillarme, Davy

    2013-09-20

    The goal of this study was to critically evaluate a new generation of columns packed with 1.3 μm core-shell particles. The practical possibilities and limitations of this column technology were assessed and performance was compared with other reference columns packed with 1.7, 2.6 and 5 μm core-shell particles. The column efficiency achieved with 1.3 μm core-shell particles was indeed impressive, Hmin value of only 1.95 μm was achieved, this would correspond to an efficiency of more than 500,000 plates/m. The separation impedance of this column was particularly low, Emin=2000, mostly due to a reduced plate height, h of 1.50. Comparing the kinetic performance of 1.3 μm core-shell particles to that of other particle dimensions tested in this study revealed that the 1.3 μm material could provide systematically the shortest analysis time in a range of below 30,000 theoretical plates (Nlimitations of current instrumentation in terms of upper pressure limit and extra-column band broadening: (1) even at 1,200 bar, it was not possible to reach an optimal linear velocity showing minimal plate height value, due to the low permeability of this column (Kv=1.7×10(-11)cm(2)), and (2) for these short narrow bore columns packed with 1.3 μm core shell particles, which is mandatory for performing fast-analysis and preventing the influence of frictional heat on column performance in UHPLC, it was observed that the extra-column band broadening could have a major impact on the apparent kinetic performance. In the present work, significant plate count loss was noticed for retention factors of less than 5, even with the best system on the market (σ(2)ec=2 μL(2)). PMID:23953620

  9. Effects of single atom doping on the ultrafast electron dynamics of M1Au24(SR)18 (M = Pd, Pt) nanoclusters

    Science.gov (United States)

    Zhou, Meng; Qian, Huifeng; Sfeir, Matthew Y.; Nobusada, Katsuyuki; Jin, Rongchao

    2016-03-01

    Atomically precise, doped metal clusters are receiving wide research interest due to their synergistic properties dependent on the metal composition. To understand the electronic properties of doped clusters, it is highly desirable to probe the excited state behavior. Here, we report the ultrafast relaxation dynamics of doped M1@Au24(SR)18 (M = Pd, Pt; R = CH2CH2Ph) clusters using femtosecond visible and near infrared transient absorption spectroscopy. Three relaxation components are identified for both mono-doped clusters: (1) sub-picosecond relaxation within the M1Au12 core states; (2) core to shell relaxation in a few picoseconds; and (3) relaxation back to the ground state in more than one nanosecond. Despite similar relaxation pathways for the two doped nanoclusters, the coupling between the metal core and surface ligands is accelerated by over 30% in the case of the Pt dopant compared with the Pd dopant. Compared to Pd doping, the case of Pt doping leads to much more drastic changes in the steady state and transient absorption of the clusters, which indicates that the 5d orbitals of the Pt atom are more strongly mixed with Au 5d and 6s orbitals than the 4d orbitals of the Pd dopant. These results demonstrate that a single foreign atom can lead to entirely different excited state spectral features of the whole cluster compared to the parent Au25(SR)18 cluster. The detailed excited state dynamics of atomically precise Pd/Pt doped gold clusters help further understand their properties and benefit the development of energy-related applications.Atomically precise, doped metal clusters are receiving wide research interest due to their synergistic properties dependent on the metal composition. To understand the electronic properties of doped clusters, it is highly desirable to probe the excited state behavior. Here, we report the ultrafast relaxation dynamics of doped M1@Au24(SR)18 (M = Pd, Pt; R = CH2CH2Ph) clusters using femtosecond visible and near infrared

  10. 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

  11. 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 .

  12. Effects of single atom doping on the ultrafast electron dynamics of M1Au24(SR)18 (M = Pd, Pt) nanoclusters.

    Science.gov (United States)

    Zhou, Meng; Qian, Huifeng; Sfeir, Matthew Y; Nobusada, Katsuyuki; Jin, Rongchao

    2016-03-24

    Atomically precise, doped metal clusters are receiving wide research interest due to their synergistic properties dependent on the metal composition. To understand the electronic properties of doped clusters, it is highly desirable to probe the excited state behavior. Here, we report the ultrafast relaxation dynamics of doped M1@Au24(SR)18 (M = Pd, Pt; R = CH2CH2Ph) clusters using femtosecond visible and near infrared transient absorption spectroscopy. Three relaxation components are identified for both mono-doped clusters: (1) sub-picosecond relaxation within the M1Au12 core states; (2) core to shell relaxation in a few picoseconds; and (3) relaxation back to the ground state in more than one nanosecond. Despite similar relaxation pathways for the two doped nanoclusters, the coupling between the metal core and surface ligands is accelerated by over 30% in the case of the Pt dopant compared with the Pd dopant. Compared to Pd doping, the case of Pt doping leads to much more drastic changes in the steady state and transient absorption of the clusters, which indicates that the 5d orbitals of the Pt atom are more strongly mixed with Au 5d and 6s orbitals than the 4d orbitals of the Pd dopant. These results demonstrate that a single foreign atom can lead to entirely different excited state spectral features of the whole cluster compared to the parent Au25(SR)18 cluster. The detailed excited state dynamics of atomically precise Pd/Pt doped gold clusters help further understand their properties and benefit the development of energy-related applications. PMID:26967673

  13. 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

  14. 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.

  15. 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.

  16. 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

  17. 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 .

  18. 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.

  19. Hafnium to thorium M-shell X-ray production cross sections by proton impact

    Directory of Open Access Journals (Sweden)

    B. Deghfel

    2014-10-01

    Full Text Available Theoretical M-shell X-ray production cross sections have been calculated within the ECPSSR model. The semi-empirical cross sections are then deduced by fitting the available experimental data normalized to their corresponding theoretical values for elements with 72 ≤ Z ≤ 90 by proton in the energy range 0.1–4.0 MeV. Also, an analytical formula has been used to calculate the empirical X-ray production cross sections by direct fitting of the same experimental data, which are found to be universal, both for individual and collective fits. On the other hand, based on the individual fitting which gives the reliable cross sections, we attempt to deduce another new empirical cross sections by assuming that the ratio empirical to ECPSSR of the cross sections is roughly the same for all elements. In addition, our results are presented for selected heavy elements, namely 74W, 79Au and 83Bi, being the most extensively studied. Finally, a comparison is made between the different procedures followed here and the experimental data.

  20. 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...

  1. Core–shell monodisperse spherical mSiO2/Gd2O3:Eu3+@mSiO2 particles as potential multifunctional theranostic agents

    International Nuclear Information System (INIS)

    Core–shell nanoparticles with diameters in the range 100–500 nm have been synthesized as monodisperse spherical mesoporous (pore diameter 3 nm) silica particles with size deviation of less than 4 %, filled with gadolinium and europium oxides and coated with a mesoporous silica shell. It is shown that the melt technique developed for filling with gadolinium and europium oxides provides a nearly maximum filling of mesopores in a single-run impregnation, with gadolinium and europium uniformly distributed within the particles and forming no bulk oxides on their surface. The coating with a shell does not impair the monodispersity and causes no coagulation. The coating technique enables controlled variation of the shell thickness within the range 5–100 % relative to the core diameter. The thus produced nanoparticles are easily dispersed in water, have large specific surface area (300 m2 g−1) and pore volume (0.3 cm3 g−1), and are bright solid phosphor with superior stability in aqueous media. The core–shell structured particles can be potentially used for cancer treatment as a therapeutic agent (gadolinium neutron-capture therapy and drug delivery system) and, simultaneously, as a multimodal diagnostic tool (fluorescence and magnetic resonance imaging), thereby serving as a multifunctional theranostic agent

  2. 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:

  3. Fabrication of Fe3O4@mSiO2 Core-Shell Composite Nanoparticles for Drug Delivery Applications

    Science.gov (United States)

    Uribe Madrid, Sergio I.; Pal, Umapada; Kang, Young Soo; Kim, Junghoon; Kwon, Hyungjin; Kim, Jungho

    2015-05-01

    We report the synthesis of Fe3O4@mSiO2 nanostructures of different meso-silica (mSiO2) shell thickness, their biocompatibility and behaviors for loading and release of a model drug ibuprofen. The composite nanostructures have superparamagnetic magnetite cores of 208 nm average size and meso-silica shells of 15 to 40 nm thickness. A modified Stöber method was used to grow the meso-silica shells over the hydrothermally grown monodispersed magnetite particles. The composite nanoparticles show very promising drug holding and releasing behaviors, which depend on the thickness of meso-silica shell. The biocompatibility of the meso-silica-coated and uncoated magnetite nanoparticles was tested through cytotoxicity assay on breast cancer (MCF-7), ovarian cancer (SKOV3), normal human lung fibroblasts MRC-5, and IMR-90 cells. The high drug holding capacity and reasonable biocompatibility of the nanostructures make them ideal agents for targeted drug delivery applications in human body.

  4. 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.

  5. Synthesis and properties MFe2O4 (M = Fe, Co) nanoparticles and core-shell structures

    Science.gov (United States)

    Yelenich, O. V.; Solopan, S. O.; Greneche, J. M.; Belous, A. G.

    2015-08-01

    Individual Fe3-xO4 and CoFe2O4 nanoparticles, as well as Fe3-xO4/CoFe2O4 core/shell structures were synthesized by the method of co-precipitation from diethylene glycol solutions. Core/shell structure were synthesized with CoFe2O4-shell thickness of 1.0, 2.5 and 3.5 nm. X-ray diffraction patterns of individual nanoparticles and core/shell are similar and indicate that all synthesized samples have a cubic spinel structure. Compares Mössbauer studies of CoFe2O4, Fe3-xO4 nanoparticles indicate superparamagnetic properties at 300 K. It was shown that individual magnetite nanoparticles are transformed into maghemite through oxidation during the synthesis procedure, wherein the smallest nanoparticles are completely oxidized while a magnetite core does occur in the case of the largest nanoparticles. The Mössbauer spectra of core/shell nanoparticles with increasing CoFe2O4-shell thickness show a gradual decrease in the relative intensity of the quadrupole doublet and significant decrease of the mean isomer shift value at both RT and 77 K indicating a decrease of the superparamagnetic relaxation phenomena. Specific loss power for the prepared ferrofluids was experimentally calculated and it was determined that under influence of ac-magnetic field magnetic fluid based on individual CoFe2O4 and Fe3-xO4 particles are characterized by very low heating temperature, when magnetic fluids based on core/shell nanoparticles demonstrate higher heating effect.

  6. 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.

  7. M-shell ionization cross sections by proton impact on gold in the binary-encounter approximation

    International Nuclear Information System (INIS)

    The M-subshell ionization cross sections by proton impact on gold have been calculated in the binary-encounter approximation. The momentum distribution of target electron is estimated nonrelativistically and relativistically by the use of the hydrogenic model and the Hartree–Fock method. The obtained subshell ionization cross sections are converted into the M-X-ray production cross sections and compared with experimental data and other theoretical calculations. The electronic relativistic effect and the wave-function effect on M-shell ionization cross sections are discussed

  8. M-shell ionization cross sections by proton impact on gold in the binary-encounter approximation

    Energy Technology Data Exchange (ETDEWEB)

    Mukoyama, Takeshi, E-mail: mukoyama@atomki.mta.hu

    2015-07-01

    The M-subshell ionization cross sections by proton impact on gold have been calculated in the binary-encounter approximation. The momentum distribution of target electron is estimated nonrelativistically and relativistically by the use of the hydrogenic model and the Hartree–Fock method. The obtained subshell ionization cross sections are converted into the M-X-ray production cross sections and compared with experimental data and other theoretical calculations. The electronic relativistic effect and the wave-function effect on M-shell ionization cross sections are discussed.

  9. 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)

  10. 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 86atom impact studies.

  11. 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

  12. 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.

  13. Effect of atom dimension of metalloid on structure of metallic glasses Fe83M17 (M: C, B, P)

    International Nuclear Information System (INIS)

    With the use of molecular dynamics and static relaxation methods a computer experiment is accomplished aimed to study the influence of nonmetal atomic size on the structure of iron base amorphous alloys Fe83M17 (M - C, B, P). Experimental results show that the absence of vitrification in Fe-C binary alloys unlike easily vitrifying Fe-B and Fe-P alloys is explained by the occurrence of similar local structural units as in crystal so in amorphous states

  14. 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)

  15. Role of the stabilizing shell in high-β, low-q disruptions in PBX-M

    International Nuclear Information System (INIS)

    The characteristics of high-β, low-q disruptions have been studied in PBX-M, a device with a nearby conducting shell. The coupling between the wall and the plasma was varied by choosing different plasma shapes, including nearly circular plasmas, D-shaped plasmas and bean-shaped plasmas (indented on the midplane), and by increasing the effective coverage of the plasma by the shell. Disruption precursors were observed to have a strong dependence on the coupling between the plasma and the shell. Measured mode growth times vary from between several times the Alfven time-scale (∼ 100 μs) to the L/R time-scale of the wall (∼ 20 ms). The behaviour of observed disruption precursors is interpreted in terms of the resistive wall mode theory of ideal plasmas, and a detail calculation of the stability of a strongly coupled bean configuration using the NOVA-W linear stability code is presented. The experimental observations are in good agreement with the theoretical predictions. (author). 32 refs, 13 figs, 2 tabs

  16. M(H) dependence and size distribution of SPIONs measured by atomic magnetometry

    CERN Document Server

    Colombo, Simone; Grujic, Zoran D; Dolgovskiy, Vladimir; Weis, Antoine

    2016-01-01

    We demonstrate that the quasistatic recording of the magnetic excitation function M(H) of superparamagnetic iron oxide magnetic nanoparticle (SPION) suspensions by an atomic magnetometer allows a precise determination of the sample's iron mass content mFe and the particle size distribution.

  17. Disentangling the Biological and Environmental Control of M. edulis Shell Chemistry

    OpenAIRE

    Heinemann, Agnes; Hiebenthal, Claas; Fietzke, Jan; Eisenhauer, Anton; Wahl, Martin

    2011-01-01

    Blue mussel individuals (Mytilus edulis) were cultured at four different salinities (17, 20, 29, and 34). During the course of the experiment, temperature was gradually increased from 6°C to 14°C. Mg/Ca and Sr/Ca ratios of the shell calcite portions produced during the 9 weeks of experimental treatment as well parts that were precipitated before the treatment phase were measured by laser ablation–multicollector–inductively coupled plasma–mass spectrometry. Mg/Ca ratios show a positive correla...

  18. Atom Localization in two and three dimensions via level populations in an M-type atomic system

    CERN Document Server

    Chaudhari, Nilesh

    2014-01-01

    Schemes for two-dimensional (2D) and three-dimensional (3D) atomic states localization in a five level M-type system using standing-wave laser fields are presented. In the upper two levels of the system we see a `coupled' localization for both 2D and 3D case. Here, the state in which majority of population will be found depends on the sign of the detunings between the upper levels and the intermediate level. The experimental implementation of the scheme using the D2 line of Rb is also proposed.

  19. Density functional calculations on 13-atom Pd12M (M=Sc-Ni) bimetallic clusters

    Institute of Scientific and Technical Information of China (English)

    Tang Chun-Mei; Chen Sheng-Wei; Zhu Wei-Hua; Tao Cheng-Jun; Zhang Ai-Mei; Gong Jiang-Feng; Zou Hua; Liu Ming-Yi; Zhu Feng

    2012-01-01

    The geometric structures,electronic and magnetic properties of the 3d transition metal doped clusters Pd12M (M =Sc Ni) are studied using the semi-core pseudopots density functional theory.The groundstate geometric structure of the Pd12M cluster is probably of pseudoicosahedron.The Ih-Pd12M cluster has the most thermodynamic stability in five different symmetric isomers.The energy gap shows that Pd12M cluster is partly metallic.Both the absolutely predominant metal bond and very weak covalent bond might exist in the Pd12M cluster.The magnetic moment of Pd12M varies from 0 to 5 μB' implying that it has a potential application in new nanomaterials with tunable magnetic properties.

  20. 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.

  1. A quantum sensor for atom-surface interactions below 10 $\\mu$m

    CERN Document Server

    Sorrentino, F; Ferrari, G; Ivanov, V V; Poli, N; Schioppo, M; Tino, G M

    2008-01-01

    We report about the realization of a quantum device for force sensing at micrometric scale. We trap an ultracold $^{88}$Sr atomic cloud with a 1-D optical lattice, then we place the atomic sample close to a test surface using the same optical lattice as an elevator. We demonstrate precise positioning of the sample at the $\\mu$m scale. By observing the Bloch oscillations of atoms into the 1-D optical standing wave, we are able to measure the total force on the atoms along the lattice axis, with a spatial resolution of few microns. We also demonstrate a technique for transverse displacement of the atoms, allowing to perform measurements near either transparent or reflective test surfaces. In order to reduce the minimum distance from the surface, we compress the longitudinal size of the atomic sample by means of an optical tweezer. Such system is suited for studies of atom-surface interaction at short distance, such as measurement of Casimir force and search for possible non-Newtonian gravity effects.

  2. Inelastic resonant M-scattering of X-rays from Gd metal with inner-shell excitation

    International Nuclear Information System (INIS)

    The paper presents results on resonant inner-shell scattering in Gd across the M5 threshold; the scattering channel with formally a 4 p hole in the final state is studied. Two scattering channels are in competition: one at constant transferred energy and another at constant outgoing energy. The branching ratio of the process at constant transferred energy is about 5%. It's isolated the many-body satellite structure of the formally 4p3/2 final hole state and it's discussed the importance of the multiplet splitting and of the super Coster-Kronig conversion of this state into another final state with two 4 d holes. The results with resonant M5 excitation are also compared with those of non-resonant excitation well above the M4 threshold. Guidelines for future research are briefly presented

  3. Design and characterization of core-shell mPEG-PLGA composite microparticles for development of cell-scaffold constructs

    DEFF Research Database (Denmark)

    Wen, Yanhong; Gallego, Monica Ramos; Nielsen, Lene Feldskov;

    2013-01-01

    combined drug delivery/scaffold system. Composite microparticles were produced by incorporating either alginate/dermatan sulfate (Alg/DS) or alginate/chitosan/dermatan sulfate (Alg/CS/DS) particles in mPEG-PLGA microparticles using coaxial ultrasonic atomization. The encapsulation and distribution of Alg...

  4. Scaled-energy spectroscopy of a |M|=1 Rydberg barium atom in an electric field

    Institute of Scientific and Technical Information of China (English)

    Wang Lei; Quan Wei; Shen Li; Yang Hai-Feng; Shi Ting-Yun; Liu Xiao-Jun; Liu Hong-Ping; Zhan Ming-Sheng

    2009-01-01

    We observe strong energy-dependent quantum defects in the scaled-energy Stark spectra for |M|=1 Rydberg states of barium atoms at three scaled energies: ε= -2.000, ε= -2.500 and ε=-3.000. In an attempt to explain the observations, theoretical calculations of closed orbit theory based on a model potential including core effect are performed for non-hydrogenic atoms. While such a potential has been uniformly successful for alkali atoms with a single valence electron, it fails to match experimental results for barium atoms in the 6snp Rydberg states with two valence electrons. Our study points out that this discrepancy is due to the strong perturbation from the 5d8p state, which voids the simple approximation for constant quantum defects of principle quantum number n.

  5. The simple ontology of kalăm atomism: an outline.

    Science.gov (United States)

    Sabra, A I

    2009-01-01

    This paper aims to present concisely the Islamic kalăm atomism as an alternative philosophy to Hellenizing falsafa. Kalăm is a theological-philosophical discourse which, first (in the third/ninth century) ventured to rival the falsafa represented early by al-Kindĭ (d.ca. 252/866), then by al-Fărăbĭ and Avicenna in the fourth/tenth and fifth/ eleventh centuries, and which eventually (in the sixth/twelfth century and after) appeared to be inclined to propose a mingling of the kalăm discourse with falsafa in a series of varied "syntheses".--Focusing on the simple ontology of the basic kalăm atomism, and noting the hybrid character of kalăm, the aim of this paper is to help to clarify the inevitable problematic consequences of those late ventures of Islamic intellectualism. PMID:19831225

  6. 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)

  7. 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

  8. 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)

  9. Projectile charge state dependence of M-shell ionization of Au, Pb, Bi, and U by 1.42-MeV/amu fluorine ions

    International Nuclear Information System (INIS)

    The present study was undertaken to determine the direct ionization and electron capture contributions to vacancy production in the M-shells of 79Au, 82Pb, 83Bi and 92U for incident 199F ions. M-shell x-ray production cross sections have been measured for 1.42-MeV/amu 199Fq+ ions for q = 4,5,6,8,9. Enhancements in the target x-ray production cross sections were observed for projectiles with one and two K-shell vacancies over those without K-shell vacancies. Direct ionization and electron capture contributions to the vacancy production were extracted from the data and compared to the plane wave Born approximation and to the Oppenheimer-Brinkman-Kramers calculations of Nikolaev, respectively

  10. 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.

  11. 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.

  12. 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)

  13. 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.)

  14. M-shell electron capture and direct ionization of gold by 25-MeV carbon and 32-MeV oxygen ions

    International Nuclear Information System (INIS)

    M-shell x-ray production cross sections have been measured for thin solid targets of Au for 25 MeV 12C/sup q+/ (q = 4, 5, 6) and for 32 MeV 16O/sup q+/ (q = 5, 7, 8). The microscopic cross sections were determined from measurements made with targets ranging in thickness from 0.5 to 100 μg/cm2. For projectiles with one or two K-shell vacancies, the M-shell x-ray production cross sections are found to be enhanced over those by projectiles without a K-shell vacancy. The sum of direct ionization to the continuum (DI) and 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. PWBA for DI and OBK of Nikolaev for EC and the ECPSSR approach that accounts for energy loss, Coulomb deflection and relativistic effects in the perturbed stationary state theory. 25 references, 3 figures, 1 table

  15. Charge Exchange Produced Emission of Carbon in the Iron M-shell Dominated 150-200 Å Extreme Ultraviolet Region

    Science.gov (United States)

    Lepson, Jaan K.; Beiersdorfer, Peter; Bitter, Manfred; Roquemore, A. Lane; Kaita, Robert

    2015-08-01

    We report on emission spectra in the extreme ultraviolet region 150-200 Å recorded at the National Spherical Torus Experiment (NSTX). This region is typically dominated by M-shell iron emission that is used extensively for solar observations, e.g. Hinode and the Solar Dynamics Observatory, and stellar atmospheres, e.g., the Extreme Ultraviolet Explorer (EUVE). We find that significant emission occurs from several heretofore unmeasured lines, which can persist throughout the plasma duration. We attribute these lines to emission from K-shell carbon ions (C V and C VI). Spectral modeling of collisional excitation fails to account for these lines, but modeling of charge exchange provides a good match with the observation. Our spectral model shows that the lines are formed by charge exchange of bare and hydrogenlike carbon with neutral hydrogen. The high abundance of bare and hydrogenlike carbon in the solar wind suggests that these lines may be formed in the heliosphere and may be part of the soft X-ray background. They may thus be observed by energy dispersive instruments, such as microcalorimeters.This work was supported by the DOE General Plasma Science program. Work was performed by Lawrence Livermore National Laboratory and Princeton Plasma Physics Laboratory under the auspices of the U. S. Department of Energy under Contracts DEAC52-07NA27344 and DE-AC02-09CH11466.

  16. Robust spatial coherence 5 μ m from a room-temperature atom chip

    Science.gov (United States)

    Zhou, Shuyu; Groswasser, David; Keil, Mark; Japha, Yonathan; Folman, Ron

    2016-06-01

    We study spatial coherence near a classical environment by loading a Bose-Einstein condensate into a magnetic lattice potential and observing diffraction. Even very close to a surface (5 μ m ), and even when the surface is at room temperature, spatial coherence persists for a relatively long time (≥500 ms ). In addition, the observed spatial coherence extends over several lattice sites, a significantly greater distance than the atom-surface separation. This opens the door for atomic circuits, and may help elucidate the interplay between spatial dephasing, interatomic interactions, and external noise.

  17. 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

  18. Atomic diffusion and mixing in old stars VI: The lithium content of M30

    DEFF Research Database (Denmark)

    Gruyters, Pieter; Lind, Karin; Richard, Olivier; Grundahl, Frank; Asplund, Martin; Casagrande, Luca; Charbonnel, Corinne; Milone, Antonino; Primas, Francesca; Korn, Andreas J.

    2016-01-01

    stars observed today had undergone photospheric depletion of lithium. The cause of this depletion is investigated by accurately tracing the behaviour of the lithium abundances as a function of effective temperature. Globular clusters are ideal laboratories for such an abundance analysis as the relative...... turnoff and early subgiant stars form a thin plateau that is broken off abruptly in the middle of the SGB as a result of the onset of Li dilution caused by the first dredge-up. Abundance trends with effective temperature for Fe and Ca are observed and compared to predictions from stellar structure models...... including atomic diffusion and ad hoc additional mixing below the surface convection zone. The comparison shows that the stars in M30 are affected by atomic diffusion and additional mixing. After applying a conservative correction for atomic diffusion, we find an initial Li abundance of A(Li) = $2.48\\pm0...

  19. Atomic mechanisms of formation and structure relaxation of Fe{sub 83}M{sub 17} (M: C, B, P) metallic glass

    Energy Technology Data Exchange (ETDEWEB)

    Evteev, A.V.; Kosilov, A.T.; Levtchenko, E.V

    2003-05-23

    The individual characteristic properties of local atomic ordering of structure forming in Fe{sub 83}M{sub 17} (M: C, B, P) metallic glass have been indicated by a computer simulation method. It is proved that carbon atoms 'prefer' to take up the interstitial positions in atomic configurations based on a distorted octahedron and trigonal prism while boron atoms tend to occupy the centres of a distorted Archymedian antiprism. Phosphorus atoms are able to take up both the interstitial and the substitutional positions and the short-range ordering around them is mainly icosahedrical. The interrelationship between the atomic structure of Fe{sub 83}M{sub 17} (M: C, B, P) amorphous metallic alloys and their vitrification ability has been determined.

  20. 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.

  1. Total M-shell X-ray yields from a thick Pt target irradiated by 10–25 keV electrons

    International Nuclear Information System (INIS)

    Highlights: ► X-ray spectra of a thick Pt element have been obtained in electron impact of 10–25 keV. ► L-shell of Pt consist of well resolved Ll, Lα, Lβ, Lγ lines while M-shell has unresolved Mξ, Mα,β,γ and M3-O1,4,5 dominant transition lines. ► Total M-shell X-ray yields Y(E0) is extracted from X-ray spectra of Pt obtained in electron impact. ► Monte Carlo calculation using PENELOPE code is made to calculate M-shell X-ray yield under distorted wave Born approximation. ► A good agreement is obtained between experiment and simulation for M-shell X-ray yields. - Abstract: We present the measurements of total M-shell X-ray yields Y(E0) of a pure thick Pt element produced by electron impact in the energy range of E0 = 10–25 keV. Measurements are performed by employing a Si-PIN photo diode X-ray detector as an energy-dispersive spectrometer (EDS). The experimental data for Y(E0) are compared with the corresponding predictions from Monte Carlo (MC) calculations using the general purpose MC code PENELOPE. A good agreement is obtained between the experiment and the MC calculations for the variation of Y(E0) with impact energy both in shape and in magnitude within the experimental uncertainty of about 12.5%.

  2. 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.

  3. 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.

  4. Wavelengths, transition probabilities, and oscillator strengths for M-shell transitions in Co-, Ni-, Cu-, Zn-, Ga-, Ge-, and Se-like Au ions

    International Nuclear Information System (INIS)

    Wavelengths, transition probabilities, and oscillator strengths have been calculated for M-shell electric dipole transitions in Co-, Ni-, Cu-, Zn-, Ga-, Ge-, and Se-like Au ions. The fully relativistic multiconfiguration Dirac–Fock method, taking quantum electrodynamical effects and the Breit correction into account, was used in the calculations. Calculated energy levels of M-shell excited states for Cu-, Zn-, Ga-, Ge-, and Se-like Au ions from the method were compared with available theoretical and experimental results, and good agreement with them was achieved

  5. 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.

  6. 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

  7. Molecular and Atomic Excitation Stratification in the Outflow of the Planetary Nebula M27

    CERN Document Server

    McCandliss, S R; Lupu, R E; Burgh, E B; Sembach, K; Kruk, J; Andersson, B G; Feldman, P D; Candliss, Stephan R. Mc; France, Kevin; Lupu, Roxana E.; Burgh, Eric B.; Sembach, Kenneth; Kruk, Jeffrey; Feldman, Paul D.

    2007-01-01

    High resolution spectroscopy with FUSE and STIS of atomic and molecular velocity stratification in the nebular outflow of M27 challenge models for the abundance kinematics in planetary nebulae. The simple picture of a very high speed (~ 1000 km/s), high ionization, radiation driven stellar wind surrounded by a slower (~ 10 km/s) mostly molecular outflow, with low ionization and neutral atomic species residing at the wind interaction interface, is not supported... We find ...there is a fast (33 -- 65 km/s) low ionization zone, surrounding a slower ( H_2^+ + e -> H(1s) + H (nl)), which ultimately produces fluorescence of Ha and Lya. In the optically thin limit at the inferred radius of the velocity transition we find dissociation of H_2 by stellar Lyc photons is an order of magnitude more efficient than spontaneous dissociation by far-UV photons. We suggest that the importance of this H_2 destruction process in HII regions has been overlooked.

  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. 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...

  10. The stress–strain state of the cracked welded joint between the header and the shell of PGV-1000M steam generator

    OpenAIRE

    Ban’ko, S. M.; Kobel’skii, S. V.; Samardžić, I.

    2014-01-01

    The three-dimensional elastoplastic stress–strain state of the cracked welded joint between the “hot” header and the shell of PGV-1000M steam generator is numerically analyzed. The crack is located on the inside surface of the connector pipe, near the fillet. The effect of the loading history on the crack-tip stress-intensity factor is assessed.

  11. 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

  12. Synthesis and photoluminescence properties of in-situ synthesized core–shell (m-VC@C) nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Mahajan, Mani [School of Physics and Materials Science, Thapar University, Patiala 147004 (India); Lalla, N.P. [UGC-DAE Consortium for Scientific Research, University Campus, Indore 452017 (India); Singh, K. [School of Physics and Materials Science, Thapar University, Patiala 147004 (India); Pandey, O.P., E-mail: oppandey@thapar.edu [School of Physics and Materials Science, Thapar University, Patiala 147004 (India)

    2015-06-15

    Core–shell structure of mesoporous vanadium carbide nanoparticles encapsulated with carbon layers (m-VC@C) have been successfully synthesized by single-step, non-toxic and economical route. The texture, morphology and optical properties of the obtained product were studied by various characterization techniques. X-ray diffraction analysis shows that the optimization of reaction time facilitates the reduction process of the precursor and hence carburization. High resolution transmission electron microscopy analysis reveals that the synthesized vanadium carbide nanoparticles with average size of 30–40 nm were encapsulated in 20–22 layers of carbon. High thermal stability of the obtained product was found at high temperatures. N{sub 2} adsorption/desorption isotherm shows that the sample has a specific surface area of 62.4560 m{sup 2}/g and pore volume 0.30 cm{sup 3}/g with pore size in the mesoporous range (3–14 nm). The formation mechanism of carbide and carbon layer has been explained on the basis of experimental results. The as-obtained m-VC@C shows good absorption and luminescence properties. Its application in photocatalytic degradation of the organic pollutant has been studied. - Highlights: • VC@C nanocomposite has been synthesized using in situ chemical-reduction route. • The synthesis of VC@C powder through this technique is our first reporting. • The VC@C is stable at higher temperatures than the reported ones. • PL emission intensity shows that the VC@C is luminescent material.

  13. M1 and E2 transitions in the ground-state configuration of atomic manganese

    International Nuclear Information System (INIS)

    Using the multiconfiguration Hartree-Fock approximation within the framework of the Breit-Pauli Hamiltonian (MCHF+BP) and the relativistic Hartree-Fock (HFR) approximation, we have calculated the forbidden transition (M1 and E2) parameters such as transition energies, logarithmic weighted oscillator strengths and transition probabilities between the fine-structure levels in the ground-state configuration of 3d54s2 for atomic manganese (Mn I, Z = 25). A discussion of these calculations for manganese using MCHF+BP and HFR methods is given here. (author)

  14. 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

  15. Atomic and molecular physics - Ions in solids - Laser systems. Courses, corrected exercises and problems Level M1/M2

    International Nuclear Information System (INIS)

    This document proposes the table of contents and a brief presentation of a course book for students in atomic and molecular physics. After some generalities on energy quantification and on photon momentum / Compton Effect, the different chapters address topics like hydrogen and helium atoms, alkalis, alkaline-earth, atoms with several valence electrons, the atom-radiation interaction, molecule and ion spectroscopy in solids, and the most significant laser systems using an active media based on atoms, ions or molecules in a diluted environment. Each chapter contains exercises and problems

  16. Charge-state dependence of M-shell x-ray production in 67Ho by 2--12-MeV carbon ions

    International Nuclear Information System (INIS)

    Charge-state dependence of M-shell x-ray production cross sections of 67Ho bombarded by 2--12-MeV carbon ions, with and without K-shell vacancies, were measured using a windowless Si(Li) x-ray detector with a full-width-at-half-maximum resolution of 135 eV at 5.9 keV. Carbon ions of different charge states were produced using a postacceleration, nitrogen gas stripping cell. The carbon ions were then magnetically analyzed to select the desired charge state and energy before entering the target chamber. The total M-shell and Mζ, Mα,β, and Mγ x-ray cross sections were measured. The electron-capture (EC) contributions as well as the direct-ionization (DI) contributions can be determined by making a comprehensive study of the projectile-charge-state dependence of the target x-ray production cross sections for targets in which the single-collision realm is maintained. In this paper, both EC and DI contributions and the total M-shell x-ray production cross sections are compared to both the first Born theory and to the perturbed-stationary-state theory with energy-loss, Coulomb-deflection, and relativistic corrections

  17. Enhancement of the oxygen reduction on nitride stabilized pt-M (M=Fe, Co, and Ni) core–shell nanoparticle electrocatalysts

    KAUST Repository

    Kuttiyiel, Kurian A.

    2015-04-01

    Given the harsh operating conditions in hydrogen/oxygen fuel cells, the stability of catalysts is one of the critical questions affecting their commercialization. We describe a distinct class of oxygen reduction (ORR) core–shell electrocatalysts comprised of nitride metal cores enclosed by thin Pt shells that is easily synthesized. The synthesis is reproducible and amenable to scale up. Our theoretical analysis and the experimental data indicate that metal nitride nanoparticle cores could significantly enhance the ORR activity as well as the durability of the core–shell catalysts as a consequence of combined geometrical, electronic and segregation effects on the Pt shells. In addition to its fuel cells application, this class of catalysts holds promise to significantly contribute in resolving the problem of platinum scarcity and furthermore indicates the guidelines for future research and development.

  18. Diffuse Atomic and Molecular Gas in the Interstellar Medium of M82 toward SN 2014J

    CERN Document Server

    Ritchey, Adam M; Dahlstrom, Julie A; York, Donald G

    2014-01-01

    We present a comprehensive analysis of interstellar absorption lines seen in moderately-high resolution, high S/N ratio optical spectra of SN 2014J in M82. Our observations were acquired over the course of six nights, covering the period from ~7 days before to ~29 days after the supernova reached its maximum V-band brightness. Complex interstellar absorption is observed from Na I, Ca II, K I, Ca I, CH+, CH, and CN, much of which arises from gas in the interstellar medium of M82, although absorption features associated with the Galactic disk and halo are also observed. We detect Li I absorption over a range in velocity consistent with that exhibited by the strongest Na I and K I components associated with M82; this is the first detection of interstellar Li in a galaxy outside of the Local Group. There are no significant temporal variations in the absorption-line profiles over the 37 days sampled by our observations. The relative abundances of the observed atomic and molecular species reveal that the ISM of M82...

  19. Excitation of the {sup 229m}Th nuclear isomer via resonance conversion in ionized atoms

    Energy Technology Data Exchange (ETDEWEB)

    Karpeshin, F. F., E-mail: fkarpeshin@gmail.com [D.I. Mendeleev Institute for Metrology (VNIIM) (Russian Federation); Trzhaskovskaya, M. B. [National Research Center Kurchatov Institute, Petersburg Nuclear Physics Institute (Russian Federation)

    2015-09-15

    Pressing problems concerning the optical pumping of the 7.6-eV {sup 229m}Th nuclear isomer, which is a candidate for a new nuclear optical reference point for frequencies, are examined. Physics behind the mechanism of the two-photon optical pumping of the isomer is considered. It is shown that, irrespective of the pumping scheme, a dominant contribution comes, in accord with what was proven earlier for the 3.5-eV isomer, from the resonance 8s–7s transition. Details of an optimum experimental scheme are discussed. It is shown that, after isomer excitation, the atom involved remains with a high probability in an excited state at an energy of about 0.5 eV rather than in the ground state, the required energy of the two photons being equal to the energy of the nuclear level plus the energy of the lowest 7s state of the atom. The estimated pumping time is about 1.5 s in the case where the field strength of each laser is 1 V/cm.

  20. Atomic diffusion and mixing in old stars. VI. The lithium content of M30

    Science.gov (United States)

    Gruyters, Pieter; Lind, Karin; Richard, Olivier; Grundahl, Frank; Asplund, Martin; Casagrande, Luca; Charbonnel, Corinne; Milone, Antonino; Primas, Francesca; Korn, Andreas J.

    2016-04-01

    Context. The prediction of the Planck-constrained primordial lithium abundance in the Universe is in discordance with the observed Li abundances in warm Population II dwarf and subgiant stars. Among the physically best motivated ideas, it has been suggested that this discrepancy can be alleviated if the stars observed today had undergone photospheric depletion of lithium. Aims: The cause of this depletion is investigated by accurately tracing the behaviour of the lithium abundances as a function of effective temperature. Globular clusters are ideal laboratories for such an abundance analysis as the relative stellar parameters of their stars can be precisely determined. Methods: We performed a homogeneous chemical abundance analysis of 144 stars in the metal-poor globular cluster M30, ranging from the cluster turnoff point to the tip of the red giant branch. Non-local thermal equilibrium (NLTE) abundances for Li, Ca, and Fe were derived where possible by fitting spectra obtained with VLT/FLAMES-GIRAFFE using the quantitative-spectroscopy package SME. Stellar parameters were derived by matching isochrones to the observed V vs. V-I colour-magnitude diagram. Independent effective temperatures were obtained from automated profile fitting of the Balmer lines and by applying colour-Teff calibrations to the broadband photometry. Results: Li abundances of the turnoff and early subgiant stars form a thin plateau that is broken off abruptly in the middle of the SGB as a result of the onset of Li dilution caused by the first dredge-up. Abundance trends with effective temperature for Fe and Ca are observed and compared to predictions from stellar structure models including atomic diffusion and ad hoc additional mixing below the surface convection zone. The comparison shows that the stars in M30 are affected by atomic diffusion and additional mixing, but we were unable to determine the efficiency of the additional mixing precisely. This is the fourth globular cluster (after NGC

  1. Atomic diffusion and mixing in old stars. VI. The lithium content of M30

    Science.gov (United States)

    Gruyters, Pieter; Lind, Karin; Richard, Olivier; Grundahl, Frank; Asplund, Martin; Casagrande, Luca; Charbonnel, Corinne; Milone, Antonino; Primas, Francesca; Korn, Andreas J.

    2016-05-01

    Context. The prediction of the Planck-constrained primordial lithium abundance in the Universe is in discordance with the observed Li abundances in warm Population II dwarf and subgiant stars. Among the physically best motivated ideas, it has been suggested that this discrepancy can be alleviated if the stars observed today had undergone photospheric depletion of lithium. Aims: The cause of this depletion is investigated by accurately tracing the behaviour of the lithium abundances as a function of effective temperature. Globular clusters are ideal laboratories for such an abundance analysis as the relative stellar parameters of their stars can be precisely determined. Methods: We performed a homogeneous chemical abundance analysis of 144 stars in the metal-poor globular cluster M30, ranging from the cluster turnoff point to the tip of the red giant branch. Non-local thermal equilibrium (NLTE) abundances for Li, Ca, and Fe were derived where possible by fitting spectra obtained with VLT/FLAMES-GIRAFFE using the quantitative-spectroscopy package SME. Stellar parameters were derived by matching isochrones to the observed V vs. V-I colour-magnitude diagram. Independent effective temperatures were obtained from automated profile fitting of the Balmer lines and by applying colour-Teff calibrations to the broadband photometry. Results: Li abundances of the turnoff and early subgiant stars form a thin plateau that is broken off abruptly in the middle of the SGB as a result of the onset of Li dilution caused by the first dredge-up. Abundance trends with effective temperature for Fe and Ca are observed and compared to predictions from stellar structure models including atomic diffusion and ad hoc additional mixing below the surface convection zone. The comparison shows that the stars in M30 are affected by atomic diffusion and additional mixing, but we were unable to determine the efficiency of the additional mixing precisely. This is the fourth globular cluster (after NGC

  2. M_T2-assisted on-shell reconstruction of missing momenta and its application to spin measurement at the LHC

    CERN Document Server

    Cho, Won Sang; Kim, Yeong Gyun; Park, Chan Beom

    2008-01-01

    We propose a scheme to assign 4-momenta to the WIMP pair in the LHC event producing a pair of mother particles that decay to visible particles and a pair of invisible weakly interacting massive particles (WIMP). The transverse components are given by the values that determine the event variable M_T2, while the longitudinal components are determined by the on-shell condition on the mother particle. Although it does not give the true WIMP momenta in general, this M_T2-assisted on-shell reconstruction of missing momenta can provide kinematic variables with which one can probe spin correlations. We apply this scheme to some processes to measure the mother particle spin, and find that spin determination is possible even without a good knowledge of the mother particle and WIMP masses.

  3. Experimental studies of atomic inner shell ionization phenomena. Progress report V, 1 August 1983-1 July 1984

    International Nuclear Information System (INIS)

    Since last year's progress report (August 1984), we have analyzed most of the data taken up to that time. This has revealed some problems and led to repeating the Si11+ on He and Ar experiments over a wider energy range. In the case of the He data four points in the RTE region were taken at Brookhaven by M. Clark, J. Tanis and collaborators, with a different Si(Li) detector. This will serve as a good check on the absolute cross sections at TUNL compared to those measured at Brookhaven

  4. Core–shell monodisperse spherical mSiO{sub 2}/Gd{sub 2}O{sub 3}:Eu{sup 3+}@mSiO{sub 2} particles as potential multifunctional theranostic agents

    Energy Technology Data Exchange (ETDEWEB)

    Eurov, Daniil A., E-mail: edan@mail.ru; Kurdyukov, Dmitry A.; Kirilenko, Demid A.; Kukushkina, Julia A.; Nashchekin, Alexei V.; Smirnov, Alexander N.; Golubev, Valery G. [Ioffe Physical–Technical Institute (Russian Federation)

    2015-02-15

    Core–shell nanoparticles with diameters in the range 100–500 nm have been synthesized as monodisperse spherical mesoporous (pore diameter 3 nm) silica particles with size deviation of less than 4 %, filled with gadolinium and europium oxides and coated with a mesoporous silica shell. It is shown that the melt technique developed for filling with gadolinium and europium oxides provides a nearly maximum filling of mesopores in a single-run impregnation, with gadolinium and europium uniformly distributed within the particles and forming no bulk oxides on their surface. The coating with a shell does not impair the monodispersity and causes no coagulation. The coating technique enables controlled variation of the shell thickness within the range 5–100 % relative to the core diameter. The thus produced nanoparticles are easily dispersed in water, have large specific surface area (300 m{sup 2} g{sup −1}) and pore volume (0.3 cm{sup 3} g{sup −1}), and are bright solid phosphor with superior stability in aqueous media. The core–shell structured particles can be potentially used for cancer treatment as a therapeutic agent (gadolinium neutron-capture therapy and drug delivery system) and, simultaneously, as a multimodal diagnostic tool (fluorescence and magnetic resonance imaging), thereby serving as a multifunctional theranostic agent.

  5. The stress–strain state of the cracked welded joint between the header and the shell of PGV-1000M steam generator

    Directory of Open Access Journals (Sweden)

    S. M. Ban’ko

    2014-10-01

    Full Text Available The three-dimensional elastoplastic stress–strain state of the cracked welded joint between the “hot” header and the shell of PGV-1000M steam generator is numerically analyzed. The crack is located on the inside surface of the connector pipe, near the fillet. The effect of the loading history on the crack-tip stress-intensity factor is assessed.

  6. Des atomes éphémères, mais exotiques

    CERN Multimedia

    Boucard, Stéphane

    2005-01-01

    By remplacing, in the atoms, electrons by an other particle, physcists create new, but fleeting buildings. Thanks to these atoms, they explore some parts of subatomic particles and their interactions (6 pages)

  7. Effective actions and topological strings. Off-shell mirror symmetry and mock modularity of multiple M5-branes

    Energy Technology Data Exchange (ETDEWEB)

    Hecht, Michael

    2011-10-20

    This thesis addresses two different topics within the field of string theory. In the first part it is shown how Hodge-theoretic methods in conjunction with open string mirror symmetry can be used to compute non-perturbative effective superpotential couplings for type II/F-theory compactifications with D-branes and fluxes on compact Calabi-Yau manifolds. This is achieved by studying the at structure of operators which derives from the open/closed {beta}-model geometry. We analyze the variation of mixed Hodge structure of the relative cohomology induced by a family of divisors, which is wrapped by a D7-brane. This leads to a Picard-Fuchs system of differential operators, which can be used to compute the moduli dependence of the superpotential couplings as well as the mirror maps at various points in the open/closed deformation space. These techniques are used to obtain predictions for genuine A-model Ooguri-Vafa invariants of special Lagrangian submanifolds in compact Calabi-Yau geometries and real enumerative invariants of on-shell domain wall tensions. By an open/closed duality the system of differential equations can also be obtained from a gauged linear {sigma}-model, which describes a non-compact Calabi-Yau four-fold compactification without branes. This is used in the examples of multi-parameter models to study the various phases of the combined open/closed deformation space. It is furthermore shown how the brane geometry can be related to a F-theory compactification on a compact Calabi-Yau four-fold, where the Hodge-theoretic techniques can be used to compute the G-flux induced Gukov-Vafa-Witten potential. The dual F-theory picture also allows to conjecture the form of the Kaehler potential on the full open/closed deformation space. In the second part we analyze the background dependence of theories which derive from multiple wrapped M5-branes. Using the Kontsevich-Soibelman wall-crossing formula and the theory of mock modular forms we derive a holomorphic

  8. 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

  9. Generation of 99-mW continuous-wave 285-nm radiation for magneto-optical trapping of Mg atoms

    DEFF Research Database (Denmark)

    Madsen, Dorte Nørgaard; Yu, Ping; Balslev, Søren;

    2002-01-01

    We have developed a tunable intense narrow-band 285 nm light source based on frequency doubling of 570 nm light in BBO. At input powers of 840 mW (including 130 mW used for locking purposes) we generate 99 mW UV radiation with an intensity profile suitable for laser-cooling experiments. The light...... is used for laser cooling of neutral magnesium atoms in a magneto-optical trap (MOT). We capture about 5 x 10(6) atoms directly from a thermal beam and find that the major loss mechanism of the magnesium MOT is a near-resonant two-photon ionization process....

  10. Generation of 99-mW continuous-wave 285-nm radiation for magneto-optical trapping of Mg atoms

    DEFF Research Database (Denmark)

    Madsen, D. N; Yu, P.; Balslev, S.;

    2002-01-01

    We have developed a tunable intense narrow-band 285 nm light source based on frequency doubling of 570 nm light in BBO. At input powers of 840 mW (including 130 mW used for locking purposes) we generate 99 mW UV radiation with an intensity profile suitable for laser-cooling experiments. The light...... is used for laser cooling of neutral magnesium atoms in a magneto-optical trap (MOT). We capture about 5×106 atoms directly from a thermal beam and find that the major loss mechanism of the magnesium MOT is a near-resonant two-photon ionization process....

  11. 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.

  12. DIFFUSE ATOMIC AND MOLECULAR GAS IN THE INTERSTELLAR MEDIUM OF M82 TOWARD SN 2014J

    International Nuclear Information System (INIS)

    We present a comprehensive analysis of interstellar absorption lines seen in moderately high resolution, high signal-to-noise ratio optical spectra of SN 2014J in M82. Our observations were acquired over the course of six nights, covering the period from ∼6 days before to ∼30 days after the supernova reached its maximum B-band brightness. We examine complex absorption from Na I, Ca II, K I, Ca I, CH+, CH, and CN, arising primarily from diffuse gas in the interstellar medium (ISM) of M82. We detect Li I absorption over a range in velocity consistent with that exhibited by the strongest Na I and K I components associated with M82; this is the first detection of interstellar Li in a galaxy outside of the Local Group. There are no significant temporal variations in the absorption-line profiles over the 37 days sampled by our observations. The relative abundances of the various interstellar species detected reveal that the ISM of M82 probed by SN 2014J consists of a mixture of diffuse atomic and molecular clouds characterized by a wide range of physical/environmental conditions. Decreasing N(Na I)/N(Ca II) ratios and increasing N(Ca I)/N(K I) ratios with increasing velocity are indicative of reduced depletion in the higher-velocity material. Significant component-to-component scatter in the N(Na I)/N(Ca II) and N(Ca I)/N(Ca II) ratios may be due to variations in the local ionization conditions. An apparent anti-correlation between the N(CH+)/N(CH) and N(Ca I)/N(Ca II) ratios can be understood in terms of an opposite dependence on gas density and radiation field strength, while the overall high CH+ abundance may be indicative of enhanced turbulence in the ISM of M82. The Li abundance also seems to be enhanced in M82, which supports the conclusions of recent gamma-ray emission studies that the cosmic-ray acceleration processes are greatly enhanced in this starburst galaxy

  13. DIFFUSE ATOMIC AND MOLECULAR GAS IN THE INTERSTELLAR MEDIUM OF M82 TOWARD SN 2014J

    Energy Technology Data Exchange (ETDEWEB)

    Ritchey, Adam M. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States); Welty, Daniel E.; York, Donald G. [Department of Astronomy and Astrophysics, University of Chicago, 5640 S. Ellis Ave., Chicago, IL 60637 (United States); Dahlstrom, Julie A., E-mail: aritchey@astro.washington.edu [Department of Physics and Astronomy, Carthage College, 2001 Alford Park Dr., Kenosha, WI 53140 (United States)

    2015-02-01

    We present a comprehensive analysis of interstellar absorption lines seen in moderately high resolution, high signal-to-noise ratio optical spectra of SN 2014J in M82. Our observations were acquired over the course of six nights, covering the period from ∼6 days before to ∼30 days after the supernova reached its maximum B-band brightness. We examine complex absorption from Na I, Ca II, K I, Ca I, CH{sup +}, CH, and CN, arising primarily from diffuse gas in the interstellar medium (ISM) of M82. We detect Li I absorption over a range in velocity consistent with that exhibited by the strongest Na I and K I components associated with M82; this is the first detection of interstellar Li in a galaxy outside of the Local Group. There are no significant temporal variations in the absorption-line profiles over the 37 days sampled by our observations. The relative abundances of the various interstellar species detected reveal that the ISM of M82 probed by SN 2014J consists of a mixture of diffuse atomic and molecular clouds characterized by a wide range of physical/environmental conditions. Decreasing N(Na I)/N(Ca II) ratios and increasing N(Ca I)/N(K I) ratios with increasing velocity are indicative of reduced depletion in the higher-velocity material. Significant component-to-component scatter in the N(Na I)/N(Ca II) and N(Ca I)/N(Ca II) ratios may be due to variations in the local ionization conditions. An apparent anti-correlation between the N(CH{sup +})/N(CH) and N(Ca I)/N(Ca II) ratios can be understood in terms of an opposite dependence on gas density and radiation field strength, while the overall high CH{sup +} abundance may be indicative of enhanced turbulence in the ISM of M82. The Li abundance also seems to be enhanced in M82, which supports the conclusions of recent gamma-ray emission studies that the cosmic-ray acceleration processes are greatly enhanced in this starburst galaxy.

  14. Diffuse Atomic and Molecular Gas in the Interstellar Medium of M82 toward SN 2014J

    Science.gov (United States)

    Ritchey, Adam M.; Welty, Daniel E.; Dahlstrom, Julie A.; York, Donald G.

    2015-02-01

    We present a comprehensive analysis of interstellar absorption lines seen in moderately high resolution, high signal-to-noise ratio optical spectra of SN 2014J in M82. Our observations were acquired over the course of six nights, covering the period from ~6 days before to ~30 days after the supernova reached its maximum B-band brightness. We examine complex absorption from Na I, Ca II, K I, Ca I, CH+, CH, and CN, arising primarily from diffuse gas in the interstellar medium (ISM) of M82. We detect Li I absorption over a range in velocity consistent with that exhibited by the strongest Na I and K I components associated with M82; this is the first detection of interstellar Li in a galaxy outside of the Local Group. There are no significant temporal variations in the absorption-line profiles over the 37 days sampled by our observations. The relative abundances of the various interstellar species detected reveal that the ISM of M82 probed by SN 2014J consists of a mixture of diffuse atomic and molecular clouds characterized by a wide range of physical/environmental conditions. Decreasing N(Na I)/N(Ca II) ratios and increasing N(Ca I)/N(K I) ratios with increasing velocity are indicative of reduced depletion in the higher-velocity material. Significant component-to-component scatter in the N(Na I)/N(Ca II) and N(Ca I)/N(Ca II) ratios may be due to variations in the local ionization conditions. An apparent anti-correlation between the N(CH+)/N(CH) and N(Ca I)/N(Ca II) ratios can be understood in terms of an opposite dependence on gas density and radiation field strength, while the overall high CH+ abundance may be indicative of enhanced turbulence in the ISM of M82. The Li abundance also seems to be enhanced in M82, which supports the conclusions of recent gamma-ray emission studies that the cosmic-ray acceleration processes are greatly enhanced in this starburst galaxy.

  15. mTOR signalling in the nucleus accumbens shell is critical for augmented effect of TFF3 on behavioural response to cocaine.

    Science.gov (United States)

    Luo, Yi-Xiao; Han, Hua; Shao, Juan; Gao, Yuan; Yin, Xi; Zhu, Wei-Li; Han, Ying; Shi, Hai-Shui

    2016-01-01

    Neuropeptides play important roles in modulating the rewarding value of abused drugs. Trefoil factor 3 (TFF3) was recently reported to modulate withdrawal syndrome of morphine, but the effects of TFF3 on the cocaine-induced behavioral changes are still elusive. In the present study, cocaine-induced hyperlocomotion and conditioned place preference (CPP) rat paradigms were provided to investigate the role of TFF3 in the reward response to cocaine. High-performance liquid chromatography (HPLC) analysis was used to analyse the dopamine concentration. The results showed that systemic TFF3 administration (0.1 mg/kg i.p.) significantly augmented cocaine- induced hyperlocomotion and CPP formation, without any effects on locomotor activity and aversive or rewarding effects per se. TFF3 significantly augmented the increment of the dopamine concentration in the NAc and the activity of the mTOR signalling pathway induced by acute cocaine exposure (10 mg/kg, i.p.) in the NAc shell, but not the core. The Intra-NAc shell infusion of rapamycin blocked TFF3-induced hyperactivity in cocaine-treatment rats. These findings indicated that TFF3 could potentiate behavioural response to cocaine, which may be associated with regulating dopamine concentration. Furthermore, the findings indicated that mTOR signalling pathway in the NAc shell is important for TFF3-induced enhancement on the cocaine-induced behavioral changes. PMID:27282818

  16. 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.

  17. Magnetically driven anisotropic structural changes in the atomic laminate M n2GaC

    Science.gov (United States)

    Dahlqvist, M.; Ingason, A. S.; Alling, B.; Magnus, F.; Thore, A.; Petruhins, A.; Mockute, A.; Arnalds, U. B.; Sahlberg, M.; Hjörvarsson, B.; Abrikosov, I. A.; Rosen, J.

    2016-01-01

    Inherently layered magnetic materials, such as magnetic Mn +1A Xn (MAX) phases, offer an intriguing perspective for use in spintronics applications and as ideal model systems for fundamental studies of complex magnetic phenomena. The MAX phase composition Mn+1A Xn consists of Mn +1Xn blocks separated by atomically thin A -layers where M is a transition metal, A an A-group element, X refers to carbon and/or nitrogen, and n is typically 1, 2, or 3. Here, we show that the recently discovered magnetic M n2GaC MAX phase displays structural changes linked to the magnetic anisotropy, and a rich magnetic phase diagram which can be manipulated through temperature and magnetic field. Using first-principles calculations and Monte Carlo simulations, an essentially one-dimensional (1D) interlayer plethora of two-dimensioanl (2D) Mn-C-Mn trilayers with robust intralayer ferromagnetic spin coupling was revealed. The complex transitions between them were observed to induce magnetically driven anisotropic structural changes. The magnetic behavior as well as structural changes dependent on the temperature and applied magnetic field are explained by the large number of low energy, i.e., close to degenerate, collinear and noncollinear spin configurations that become accessible to the system with a change in volume. These results indicate that the magnetic state can be directly controlled by an applied pressure or through the introduction of stress and show promise for the use of M n2GaC MAX phases in future magnetoelectric and magnetocaloric applications.

  18. M_T2-assisted on-shell reconstruction of missing momenta and its application to spin measurement at the LHC

    OpenAIRE

    Cho, Won Sang; Choi, Kiwoon; Kim, Yeong Gyun; Park, Chan Beom

    2008-01-01

    We propose a scheme to assign a 4-momentum to each WIMP in new physics event producing a pair of mother particles each of which decays to an invisible weakly interacting massive particle (WIMP) plus some visible particle(s). The transverse components are given by the value that determines the event variable M_T2, while the longitudinal component is determined by the on-shell condition on the mother particle. Although it does not give the true WIMP momentum in general, this M_T2-assisted on-sh...

  19. 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

  20. 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.

  1. Combined SCaM-XAFS and advanced photon source. XAFS of single atoms

    International Nuclear Information System (INIS)

    At the beam-line BL10XU of SPring-8 Facility, it has been proposed to construct a Capacitance XAFS (X-ray Absorption Fine Structure) in which absorption of a photon from an X-ray beam by defects in a solid followed by emission of localized and bound electrons can be monitored by capacitance change to obtain a XAFS spectrum specific only to the site of the defects. The capacitance XAFS method allows to measure zero-dimensional (corresponding to point defects) and one-dimensional (corresponding to dislocation) X-ray absorption coefficients of a three-dimensional sample solid. These LDAC (Low Dimensional Absorption Coefficient) may be denoted as 0/3 and 1/3 in the above cases. The present study may be extended to obtain capacitance XAFS from such interfaces as for example metal-insulator and insulator-semiconductor, etc, (which can be denoted as 0/2 and 1/2), and the required photon intensity for the SCaM study is discussed. Of these, 0/2 spectrum corresponds to a single atom XAFS. (S.Ohno)

  2. Characterization of oxidation resistant Fe@M (M=Cr, Ni) core@shell nanoparticles prepared by a modified reverse micelle reaction

    Science.gov (United States)

    Naik, Sweta H.; Carroll, Kyler J.; Carpenter, Everett E.

    2011-04-01

    Iron-based nanoparticles are the forerunners in the field of nanotechnology due to their high magnetization saturation and biocompability which affords them use in a variety of applications. However, iron-based nanoparticles, due to a high surface-to-volume ratio, suffer from oxidation and limit its practicality by lowering the magnetic moment significantly. To avoid this oxidation, the surfaces of the particles have to be passivated. One such way to accomplish this passivation is to synthesize core@shell nanoparticles that have a surface treatment of chromium or nickel. These core@shell nanoparticles have been synthesized using a reverse micelle technique. The Cr and Ni passivated iron nanoparticles were characterized by x-ray diffraction, transmission electron microscopy, vibrating sample magnetometry, and x-ray photoelectron spectroscopy to determine their phase, morphology, surface properties, and magnetization saturation. A high magnetization saturation of 160 and 165 emu/g for Cr and Ni passivated iron core@shell nanoparticles was achieved.

  3. Assembly and Loading of LQS01, a Shell-Based 3.7 m Long Nb3Sn Quadrupole Magnet for LARP

    Energy Technology Data Exchange (ETDEWEB)

    Ferracin, P.; Ambrosio, G.; Anerella, M.; Bingham, B.; Bossert, R.; Caspi, S.; Cheng, D. W.; Chlachidze, G.; Felice, H.; Hafalia, A. R.; Hannaford, C. R.; Mumper, W.; Nobrega, F.; Prestemon, S.; Sabbi, G. L.; Schmalzle, J.; Sylvester, C.; Tartaglia, M.; Wanderer, P.; Zlobin, A.

    2009-10-19

    The LHC Accelerator Research Program (LARP) has been engaged in the fabrication of the 3.7 m long quadrupole magnet LQS01 in order to demonstrate that Nb{sub 3}Sn magnets are a viable option for future LHC Luminosity upgrades. The LQS01 design, a scale-up of the 1 m long Technology Quadrupole TQS, includes four 3.4 m long cos(theta) coils contained in a support structure based on four 1 m long aluminum shells pre-tensioned with water-pressurized bladders (shell-type structure). In order to verify assembly procedures and loading operations, the structure was pre-stressed around solid aluminum 'dummy coils' and cooled-down to 77 K. Mechanical behavior and stress variations were monitored with strain gauges mounted on the structure and on the dummy coils. The dummy coils were then replaced with Nb{sub 3}Sn coils in a second assembly and loading procedure, in preparation for the cool-down and test. This paper reports on the cool-down test with dummy coils and on the assembly and loading of LQS01, with a comparison between 3D finite element model predictions and strain gauge data.

  4. 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)

  5. 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

  6. 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)

  7. Short-ranged potential effects on the recurrence spectra of lithium M = 1 atoms in parallel electric and magnetic fields

    Institute of Scientific and Technical Information of China (English)

    Wang Wen-Peng; Li Hong-Yun; Wang Shu-Bao; Lin Sheng-Lu

    2008-01-01

    This paper presents recurrence spectra of highly excited lithium atoms with M = 1 state in parallel electric and magnetic fields at a fixed scaled energy ε = -0.03. Short-ranged potentials including ionic core potential and centrifugal barrier are taken into account. Their effects on the states and photo-absorption spectrum are analysed in detail. This demonstrates that the geometric features of classical orbits are of special importance for modulations of the spectral pattern. Thus the weak polarization as well as the reduction of correlation of electrons induced by short-ranged potentials give rise to the recurrence spectra of lithium M = 1 atoms more compact than that of the M = 0 one, which is in good agreement with the experimental prediction.

  8. Atomic resolution structure of the double mutant (K53,56M) of bovine pancreatic phospholipase A2

    International Nuclear Information System (INIS)

    The atomic resolution crystal structure of the double mutant (K53,56M) of bovine pancreatic phospholipase A2 is reported. The structure of the double mutant K53,56M has previously been refined at 1.9 Å resolution using room-temperature data. The present paper reports the crystal structure of the same mutant K53,56M refined against 1.1 Å data collected using synchrotron radiation. A total of 116 main-chain atoms from 29 residues and 44 side chains are modelled in alternate conformations. Most of the interfacial binding residues are found to be disordered and alternate conformations could be recognized. The second calcium ion-binding site residue Glu92 adopts two alternate conformations. The minor and major conformations of Glu92 correspond to the second calcium ion bound and unbound states

  9. Palomar/triplespec observations of Spitzer/MIPSGAL 24 μm circumstellar shells: Unveiling the natures of their central sources

    Energy Technology Data Exchange (ETDEWEB)

    Flagey, N. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Noriega-Crespo, A. [Infrared Processing and Analysis Center, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Petric, A. [California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Geballe, T. R., E-mail: nflagey@jpl.nasa.gov [Gemini North Observatory, 670 North A' ohoku Place, Hilo, HI 96720 (United States)

    2014-08-01

    We present near-IR spectroscopic observations of the central sources in 17 circumstellar shells from a sample of more than 400 'bubbles' discovered in the Spitzer/MIPSGAL 24 μm survey of the Galactic plane and in the Cygnus-X region. To identify the natures of these shells, we have obtained J, H, and K band spectra with a resolution of ∼2600 of the stars at their centers. We observed 14 MIPSGAL bubbles (MBs), WR149, and 2 objects in the Cygnus-X region (WR138a and BD+43 3710), our sample being about 2.5 mag fainter in the K band than previous studies of the central sources of MBs. We use spectroscopic diagnostics and spectral libraries of late- and early-type stars to constrain the natures of our targets. We find five late-type giants. The equivalent widths of their CO 2.29 μm features allow us to determine the spectral types of the stars and hence derive the extinction along the line of sight, distance, and physical size of the shells. We also find 12 early-type stars: in 9 MBs and the 3 comparison objects. We find that the subtype inferred from the near-IR for WR138a (WN9h) and WR149 (WN5h) agrees with that derived from optical observations. A careful analysis of the literature and the environment of BD+43 3710 allows us to rule out the carbon star interpretation previously suggested. Our near-IR spectrum suggests that it is a B5 supergiant. At the centers of the nine MBs, we find a WC5-6 star possibly of low mass, a candidate O5-6 V star, a B0 supergiant, a B/A-type giant, and five luminous blue variable (LBV) candidates. We also report the detections of emission lines arising from at least two shells with typical extents (∼10''), in agreement with those in the mid-IR. We summarize the findings on the natures of the MBs since their discovery, with 30% of them now known. Most MBs with central sources detected in the near- to mid-IR have been identified and are red and blue giants, supergiants, or stars evolving toward these phases

  10. Aislamiento rápido del virus dengue 3 por el método de shell vial en el brote de dengue en Lima

    OpenAIRE

    Victoria Gutiérrez P; Miryam Palomino R; Marcela Olivares S; Gissella Noroña C

    2005-01-01

    El aislamiento de virus dengue con los métodos tradicionales demora hasta un mes, en situaciones de emergencia como el brote de dengue clásico en el distrito de Comas-Lima entre abril y mayo de 2005, es necesario un diagnóstico precoz. Se procesaron 117 muestras de sueros de pacientes con diagnóstico clínico de dengue clásico en fase virémica procedentes la zona del brote, mediante el método de shell vial para el aislamiento del virus dengue en la línea celular C6-36, se identificó el serotip...

  11. Measurements of extremely low level 152Eu and new evaluation method of Atomic Bomb neutrons using 108mAg

    International Nuclear Information System (INIS)

    Ultra low background gamma spectrometry was applied at Ogoya Underground Laboratory to measure extremely low level 152Eu induced by Atomic-Bomb in 1945. Result of 152Eu measurements extracted from kg-scale of granite sample agreed well with theoretical values based on the DS02 system up to 1.2 km from the hypocenter of Hiroshima. New method was proposed to evaluate Atomic Bomb neutrons by using 108mAg (half-life: 418 y). The 108mAg method was proved to be more than 2-3 orders of magnitude sensitive than 152Eu method and can be applied more than 1000 years in future. Furthermore better, individual neutron dose can be evaluated if finger ring or rosary of the victim was available. (author)

  12. [M9C4O]I8 (M = Y, Ho, Er, Lu), reduced rare-earth iodides with waved metal double layers and two different interstitial atoms

    International Nuclear Information System (INIS)

    [M6C4O]I8 (M=Y, Ho, Er, Lu) are examples of reduced rare-earth iodides with two different interstitial atoms. The compounds were syntehsized from appropriate mixtures of MI3, M, C and M2O3 at 1050 C in arc-welded tanatalum containers. The X-ray structure analysis of a single crystal of [Y9C4O]I8 (orthorhombic, Pmmm (Nr.59), Z=2, a=2912.7(6) pm, b=384.17(4) pm, c=1080.29(9) pm, R=0.084, Rw=0.053) exhibits octahedrally coordinated carbon in ''plane'' sections besides tetrahedrally coordinated oxygen in the ''bend'' of waved metal doubel layers. These double layers are stacked atlernately with waved iodine double layers along [001]. (orig.)

  13. 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.

  14. Black-body radiation shift of atomic energy-levels:The $ (Z \\alpha)^2\\alpha T^2/m $ correction

    CERN Document Server

    Zhou, Wanping; Lu, Jingjun; Qiao, Haoxue

    2016-01-01

    The next-to-leading order black-body radiation(BBR) shift to atomic energy-levels, namely $ (Z\\alpha)^2\\alpha T^2/m $ correction, was studied by using the nonrelativistic quantum electrodynamics(NRQED) at first. This $T^{2}$-dependent correction has not been investigated before, and only contains the contribution of eletric-dipole of thermal photon. In order to study the contribution of multipolar. We estimate the two-loop contributions of BBR-shift by using quantum electrodynamics approach(QED), and find both one-loop and two-loop diagram contribute to the $ (Z\\alpha)^2\\alpha T^2/m $ correction. Integrating the results which are obtained by these two approaches, the $ (Z\\alpha)^2\\alpha T^2/m $ correction we derived is in principle applicable to multi-electron atoms and contains the contribution of multipolar. The order of magnitude BBR-shift indicates this next-to-leading order BBR-shift may be as significant as the leading order in the multi-electron atoms or cold ones.

  15. Towards a shell-model description of the low-energy structure of deformed nuclei II. Electromagnetic properties of collective M1 bands

    International Nuclear Information System (INIS)

    A shell-model theory, called the pseudo SU(3) model, which was proposed previously for giving the structure of low-lying states in heavy deformed nuclei is used to predict the number of 1+ states with strong M1 transitions to ground states for the nuclei /sup 154/Sm, /sup 156//sup --//sup 160/Gd, /sup 164/Dy, /sup 168/Er, /sup 174/Yb of the rare earth region and the actinide species /sup 232/Th, /sup 234//sup --//sup 240/U, /sup 242/Pu. Results are also given for E2 and M3 transition strengths in these nuclei. The measures provide a rigorous test of the theory, which in reality is a many-particle Nilsson scheme, because the real M1, E2, and M3 operators are used in the calculations. It is found that the results for E2 strengths using the real quadrupole operator Q-script differ by less than 5 from those of calculations that use the operator Q which is a generator of the pseudo SU(3) symmetry. This is so even for weak interband transitions. To further test the theory additional experimental information on the 2+/sub γ/ states is necessary. In particular, the 1+ → 2+/sub γ/ decay strengths are needed to differentiate between theories for the structure of the giant M1 states. copyright 1987 Academic Press, Inc

  16. 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

  17. 570 mV photovoltage, stabilized n-Si/CoO_x heterojunction photoanodes fabricated using atomic layer deposition

    OpenAIRE

    Zhou, Xinghao; Liu, Rui; Sun, Ke; Papadantonakis, Kimberly M.; Brunschwig, Bruce S.; Lewis, Nathan S.

    2016-01-01

    Heterojunction photoanodes, consisting of n-type crystalline Si(100) substrates coated with a thin ∼50 nm film of cobalt oxide fabricated using atomic-layer deposition (ALD), exhibited photocurrent-onset potentials of −205 ± 20 mV relative to the formal potential for the oxygen-evolution reaction (OER), ideal regenerative solar-to-O_2(g) conversion efficiencies of 1.42 ± 0.20%, and operated continuously for over 100 days (∼2500 h) in 1.0 M KOH(aq) under simulated solar illumination. The ALD C...

  18. Magnetic core–bilayer shell complex of magnetite nanoparticle stabilized with mPEG–polyester amphiphilic block copolymer

    International Nuclear Information System (INIS)

    In this article, we report the synthesis of magnetite nanoparticles (Fe3O4) coated with methoxy poly(ethylene glycol) (mPEG)–polyester amphiphilic block copolymers. The coating polymer layer contains a hydrophobic inner layer of polyester and a hydrophilic corona of mPEG. The copolymers were first prepared via a direct condensation between diacid, diol compounds and mPEG oligomer to obtain a hydrophobic polyester block and hydrophilic mPEG block and then “grafted onto” a magnetite nanoparticle surface. The copolymer composition was varied by changing the structure of the diacid, diol, and the molecular weight ( M-bar n ) of the mPEG such that particles with good dispersibility and stability in water were obtained. It was found that the copolymer prepared from 1,6-hexanediol can effectively stabilize the particles in water regardless of the types of diacid and M-bar n of mPEG used. The particle size was approximately 10 nm in diameter, and the particle dispersibility in water was quite dependent on the type and concentration of the copolymer used. Thermogravimetric analysis revealed the presence of less than 37 % Fe3O4 and about 48–53 % of the copolymer in the complexes. The percent entrapment efficiency and loading efficiency of indomethacin model drug in the copolymer-coated magnetite nanoparticles were 19 and 77 %, respectively

  19. Magnetic core–bilayer shell complex of magnetite nanoparticle stabilized with mPEG–polyester amphiphilic block copolymer

    Energy Technology Data Exchange (ETDEWEB)

    Mekkapat, Supachai; Thong-On, Bandit; Rutnakornpituk, Boonjira; Wichai, Uthai; Rutnakornpituk, Metha, E-mail: methar@nu.ac.th [Naresuan University, Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science (Thailand)

    2013-11-15

    In this article, we report the synthesis of magnetite nanoparticles (Fe{sub 3}O{sub 4}) coated with methoxy poly(ethylene glycol) (mPEG)–polyester amphiphilic block copolymers. The coating polymer layer contains a hydrophobic inner layer of polyester and a hydrophilic corona of mPEG. The copolymers were first prepared via a direct condensation between diacid, diol compounds and mPEG oligomer to obtain a hydrophobic polyester block and hydrophilic mPEG block and then “grafted onto” a magnetite nanoparticle surface. The copolymer composition was varied by changing the structure of the diacid, diol, and the molecular weight ( M-bar {sub n} ) of the mPEG such that particles with good dispersibility and stability in water were obtained. It was found that the copolymer prepared from 1,6-hexanediol can effectively stabilize the particles in water regardless of the types of diacid and M-bar {sub n} of mPEG used. The particle size was approximately 10 nm in diameter, and the particle dispersibility in water was quite dependent on the type and concentration of the copolymer used. Thermogravimetric analysis revealed the presence of less than 37 % Fe{sub 3}O{sub 4} and about 48–53 % of the copolymer in the complexes. The percent entrapment efficiency and loading efficiency of indomethacin model drug in the copolymer-coated magnetite nanoparticles were 19 and 77 %, respectively.

  20. 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

  1. 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

  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. Atomic resolution scanning tunneling microscopy in a cryogen free dilution refrigerator at 15 mK

    Energy Technology Data Exchange (ETDEWEB)

    Haan, A. M. J. den, E-mail: arthur.denhaan@gmail.com; Wijts, G. H. C. J.; Galli, F.; Oosterkamp, T. H. [Department of Interface Physics, Leiden University, Niels Bohrweg 2, 2333CA Leiden (Netherlands); Usenko, O. [Leiden Cryogenics, Kenauweg 11, 2331BA Leiden (Netherlands); Baarle, G. J. C. van; Zalm, D. J. van der [Leiden Spin Imaging (LSI), J.H. Oortweg 21, 2333CH Leiden (Netherlands)

    2014-03-15

    Pulse tube refrigerators are becoming more common, because they are cost efficient and demand less handling than conventional (wet) refrigerators. However, a downside of a pulse tube system is the vibration level at the cold-head, which is in most designs several micrometers. We implemented vibration isolation techniques which significantly reduced vibration levels at the experiment. These optimizations were necessary for the vibration sensitive magnetic resonance force microscopy experiments at milli-kelvin temperatures for which the cryostat is intended. With these modifications we show atomic resolution scanning tunneling microscopy on graphite. This is promising for scanning probe microscopy applications at very low temperatures.

  4. Atomic resolution scanning tunneling microscopy in a cryogen free dilution refrigerator at 15 mK.

    Science.gov (United States)

    den Haan, A M J; Wijts, G H C J; Galli, F; Usenko, O; van Baarle, G J C; van der Zalm, D J; Oosterkamp, T H

    2014-03-01

    Pulse tube refrigerators are becoming more common, because they are cost efficient and demand less handling than conventional (wet) refrigerators. However, a downside of a pulse tube system is the vibration level at the cold-head, which is in most designs several micrometers. We implemented vibration isolation techniques which significantly reduced vibration levels at the experiment. These optimizations were necessary for the vibration sensitive magnetic resonance force microscopy experiments at milli-kelvin temperatures for which the cryostat is intended. With these modifications we show atomic resolution scanning tunneling microscopy on graphite. This is promising for scanning probe microscopy applications at very low temperatures. PMID:24689625

  5. Atomic resolution STM in a cryogen free dilution refrigerator at 15 mK

    CERN Document Server

    Haan, A M J den; Galli, F; Usenko, O; van Baarle, G J C; van der Zalm, D J; Oosterkamp, T H

    2013-01-01

    Pulse tube refrigerators are becoming more common, because they are cost efficient and demand less handling than conventional (wet) refrigerators. However, a downside of a pulse tube system is the vibration level at the cold-head, which is in most designs several micrometers. We implemented vibration isolation techniques which significantly reduced vibration levels at the experiment. These optimizations were necessary for the vibration sensitive Magnetic Resonance Force Microscopy experiments (MRFM) at milli-kelvin temperatures for which the cryostat is intended. With these modifications we show atomic resolution STM on graphite. This is promising for scanning probe microscopy applications at very low temperatures.

  6. Atomic resolution scanning tunneling microscopy in a cryogen free dilution refrigerator at 15 mK

    International Nuclear Information System (INIS)

    Pulse tube refrigerators are becoming more common, because they are cost efficient and demand less handling than conventional (wet) refrigerators. However, a downside of a pulse tube system is the vibration level at the cold-head, which is in most designs several micrometers. We implemented vibration isolation techniques which significantly reduced vibration levels at the experiment. These optimizations were necessary for the vibration sensitive magnetic resonance force microscopy experiments at milli-kelvin temperatures for which the cryostat is intended. With these modifications we show atomic resolution scanning tunneling microscopy on graphite. This is promising for scanning probe microscopy applications at very low temperatures

  7. Atomic resolution scanning tunneling microscopy in a cryogen free dilution refrigerator at 15 mK

    Science.gov (United States)

    den Haan, A. M. J.; Wijts, G. H. C. J.; Galli, F.; Usenko, O.; van Baarle, G. J. C.; van der Zalm, D. J.; Oosterkamp, T. H.

    2014-03-01

    Pulse tube refrigerators are becoming more common, because they are cost efficient and demand less handling than conventional (wet) refrigerators. However, a downside of a pulse tube system is the vibration level at the cold-head, which is in most designs several micrometers. We implemented vibration isolation techniques which significantly reduced vibration levels at the experiment. These optimizations were necessary for the vibration sensitive magnetic resonance force microscopy experiments at milli-kelvin temperatures for which the cryostat is intended. With these modifications we show atomic resolution scanning tunneling microscopy on graphite. This is promising for scanning probe microscopy applications at very low temperatures.

  8. 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)

  9. 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

  10. mülmüs Atom Potansiyeli Kullanarak CuNi Alasımının Moleküler Dinamik Simulasyonu

    Directory of Open Access Journals (Sweden)

    Eşe Ergün AKPINAR

    2009-04-01

    Full Text Available Bu çalısmada, CuNi alasımının moleküler dinamik simulasyonu, Sutton-Chen (SC potansiyeli kullanılarak incelendi. Bu potansiyel Cu, Ni ve CuNi in deneysel bilgilerinin fonksiyon parametrelerine fit edilmesiyle elde edildi. CuNi alasımının kristalizasyon sürecini atomik olarak tanımlamak için, gömülmüs atom yöntemini esas alan sabit basınç, sabit sıcaklık (NPT moleküler dinamik simulasyonu uygulandı. Sıvı fazda iken 4x1011 K/s sogutma hızında sogutulan CuNi alasımının yapısı ve kristallesme olusum yetenegi radyal dagılım fonksiyonuyla incelendi. Simulasyon, üç temel dogrultu boyunca periyodik sınır sartlarını saglayan kübik bir hücrede 1024 atom içeren sistemle gerçeklestirildi. Hareket denklemleri Verlet algoritması kullanılarak sayısal olarak çözüldü. Sogutma deneyi için sıvı hal baslangıcı, katının sıvı sıcaklıgına ısıtılmasıyla elde edildi. Sistem 1300-1550K sıvılasma bölgesi üzerindeki sıcaklıkta eritildi ve homojenize edildi ve hızla oda sıcaklıgına sogutuldu.

  11. 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

  12. Highly Stretchable Conductive Fibers from Few-Walled Carbon Nanotubes Coated on Poly(m-phenylene isophthalamide) Polymer Core/Shell Structures.

    Science.gov (United States)

    Jiang, Shujuan; Zhang, Hongbo; Song, Shaoqing; Ma, Yanwen; Li, Jinghua; Lee, Gyeong Hee; Han, Qiwei; Liu, Jie

    2015-10-27

    A core/shell stretchable conductive composite of a few-walled carbon nanotube network coated on a poly(m-phenylene isophthalamide) fiber (FWNT/PMIA) was fabricated by a dip-coating method and an annealing process that greatly enhanced interactions between the FWNT network and PMIA core as well as within the FWNT network. The first strain-conductivity test of the as-prepared FWNT/PMIA fiber showed a stretching-induced alignment of nanotubes in the shell during the deformation process and a good conductivity stability with a slight conductivity drop from 109.63 S/cm to 98.74 S/cm (Δσ/σ0 = 10%) at a strain of ∼150% (2.5 times the original length). More importantly, after the first stretching process, the fiber can be recovered with a slight increase in length but a greatly improved conductivity of 167.41 S/cm through an additional annealing treatment. The recovered fiber displays a similarly superb conductivity stability against stretching, with a decrease of only ∼13 S/cm to 154.49 S/cm (Δσ/σ0 = 8%) at a strain of ∼150%. We believe that this conductivity stability came from the formation and maintaining of aligned nanotube structures during the stretching process, which ensures the good tube-tube contacts and the elongation of the FWNT network without losing its conductivity. Such stable conductivity in stretchable fibers will be important for applications in stretchable electronics. PMID:26390200

  13. Black-body radiation shift of atomic energy-levels:The $ (Z \\alpha)^2\\alpha T^2/m $ correction

    OpenAIRE

    Zhou, Wanping; Mei, Xuesong; Lu, Jingjun; Qiao, Haoxue

    2016-01-01

    The next-to-leading order black-body radiation(BBR) shift to atomic energy-levels, namely $ (Z\\alpha)^2\\alpha T^2/m $ correction, was studied by using the nonrelativistic quantum electrodynamics(NRQED). We also estimate the one-loop contribution of quadrupole and the two-loop contributions of BBR-shift of the thermal(real) photon. These corrections have not been investigated before. The order of magnitude BBR-shift indicates the one-loop contribution of quadrupole is stronger than the previou...

  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. Large low-energy $M1$ strength for $^{56,57}$Fe within the nuclear shell model

    OpenAIRE

    Brown, B. Alex; Larsen, A.C.

    2014-01-01

    A strong enhancement at low $\\gamma$-ray energies has recently been discovered in the $\\gamma$-ray strength function of $^{56,57}$Fe. In this work, we have for the first time obtained theoretical $\\gamma$ decay spectra for states up to $\\approx 8$ MeV in excitation for $^{56,57}$Fe. We find large $B(M1)$ values for low $\\gamma$-ray energies that provide an explanation for the experimental observations. The role of mixed $E2$ transitions for the low-energy enhancement is addressed theoreticall...

  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. Atomic Resolution Structure of the Double Mutant (K53,56M) of Bovine Pancreatic Phospholipase A2

    Energy Technology Data Exchange (ETDEWEB)

    Sekar,K.; Yogavel, M.; Gayathri, D.; Velmurugan, D.; Krishna, R.; Poi, M.; Dauter, Z.; Dauter, M.; Tsai, M.

    2006-01-01

    The structure of the double mutant K53,56M has previously been refined at 1.9 Angstroms resolution using room-temperature data. The present paper reports the crystal structure of the same mutant K53,56M refined against 1.1 Angstroms data collected using synchrotron radiation. A total of 116 main-chain atoms from 29 residues and 44 side chains are modeled in alternate conformations. Most of the interfacial binding residues are found to be disordered and alternate conformations could be recognized. The second calcium ion-binding site residue Glu92 adopts two alternate conformations. The minor and major conformations of Glu92 correspond to the second calcium ion bound and unbound states.

  19. Core–shell heterostructures of SnM (M = (Fe, Ni, and Cr) or Cu) alloy nanowires @ CNTs on metallic substrates

    Energy Technology Data Exchange (ETDEWEB)

    Zhong, Yu; Zhang, Yong [Department of Mechanical and Materials Engineering, University of Western Ontario, London, Ontario, N6A 5B9 (Canada); Cai, Mei; Balogh, Michael P. [General Motors Research and Development Center, Warren, MI 48090-9055 (United States); Li, Ruying [Department of Mechanical and Materials Engineering, University of Western Ontario, London, Ontario, N6A 5B9 (Canada); Sun, Xueliang, E-mail: xsun@eng.uwo.ca [Department of Mechanical and Materials Engineering, University of Western Ontario, London, Ontario, N6A 5B9 (Canada)

    2013-04-01

    Sn alloy nanowires encapsulated in carbon nanotubes (SnM (M = (Fe, Ni, and Cr) or Cu) @ CNTs) were prepared in situ by a chemical vapor deposition (CVD) method, in which Sn came from a vaporized precursor while the alloy elements were supplied by the substrate. The heterostructures were grown on two types of substrates including stainless steel with high catalytic effectiveness and Cu substrates with low catalytic effectiveness for generating graphite layers, respectively. Pure Sn powder and C{sub 2}H{sub 4} were employed to provide Sn and carbon precursors. The products were investigated by scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM) and scanning transmission electron microscopy–energy dispersive X-ray spectroscopy (STEM–EDS) mapping. The morphology, structure and composition of the nanomaterials depended significantly on the surface conditions of the substrates. While SnCu alloy nanowires encapsulated in carbon nanotubes were grown on the Cu substrate, carbon nanotubes filled with alloy nanowires and porous carbon fibers decorated internally with alloy particles were observed on the stainless steel substrate. The growth mechanisms of the heterostructures were proposed.

  20. Core–shell heterostructures of SnM (M = (Fe, Ni, and Cr) or Cu) alloy nanowires @ CNTs on metallic substrates

    International Nuclear Information System (INIS)

    Sn alloy nanowires encapsulated in carbon nanotubes (SnM (M = (Fe, Ni, and Cr) or Cu) @ CNTs) were prepared in situ by a chemical vapor deposition (CVD) method, in which Sn came from a vaporized precursor while the alloy elements were supplied by the substrate. The heterostructures were grown on two types of substrates including stainless steel with high catalytic effectiveness and Cu substrates with low catalytic effectiveness for generating graphite layers, respectively. Pure Sn powder and C2H4 were employed to provide Sn and carbon precursors. The products were investigated by scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM) and scanning transmission electron microscopy–energy dispersive X-ray spectroscopy (STEM–EDS) mapping. The morphology, structure and composition of the nanomaterials depended significantly on the surface conditions of the substrates. While SnCu alloy nanowires encapsulated in carbon nanotubes were grown on the Cu substrate, carbon nanotubes filled with alloy nanowires and porous carbon fibers decorated internally with alloy particles were observed on the stainless steel substrate. The growth mechanisms of the heterostructures were proposed.

  1. Core-shell heterostructures of SnM (M = (Fe, Ni, and Cr) or Cu) alloy nanowires @ CNTs on metallic substrates

    Science.gov (United States)

    Zhong, Yu; Zhang, Yong; Cai, Mei; Balogh, Michael P.; Li, Ruying; Sun, Xueliang

    2013-04-01

    Sn alloy nanowires encapsulated in carbon nanotubes (SnM (M = (Fe, Ni, and Cr) or Cu) @ CNTs) were prepared in situ by a chemical vapor deposition (CVD) method, in which Sn came from a vaporized precursor while the alloy elements were supplied by the substrate. The heterostructures were grown on two types of substrates including stainless steel with high catalytic effectiveness and Cu substrates with low catalytic effectiveness for generating graphite layers, respectively. Pure Sn powder and C2H4 were employed to provide Sn and carbon precursors. The products were investigated by scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM) and scanning transmission electron microscopy-energy dispersive X-ray spectroscopy (STEM-EDS) mapping. The morphology, structure and composition of the nanomaterials depended significantly on the surface conditions of the substrates. While SnCu alloy nanowires encapsulated in carbon nanotubes were grown on the Cu substrate, carbon nanotubes filled with alloy nanowires and porous carbon fibers decorated internally with alloy particles were observed on the stainless steel substrate. The growth mechanisms of the heterostructures were proposed.

  2. M-proteinemia in atomic bomb survivors in Hiroshima and Nagasaki

    International Nuclear Information System (INIS)

    A comparative analysis of monoclonal gammopathy (M proteinemia) in A-bomb survivors, detected during the period from October 1979 through September 1981 (the first survey) and the period from June 1985 through May 1987 (the second survey), was made by using the 1986 dosimetry system. M-proteinemia was detected in 33 (0.38%) of 8,796 participants in the first survey and in 69 (0.94%) of 7,350 participants in the second survey; the prevalence of M-proteinemia was 2.5 times higher in the second survey than the first survey. It occurred more frequently with aging, especially in the 70 years and older age group. In 9 (27%) of 33 patients detected at the first survey, death was confirmed at the second survey; it was attributable to malignant tumor in 4, multiple myeloma in 2, and colon cancer, lung cancer and prostatic cancer in one each. Follow-up, available in 8 patients diagnosed as benign monoclonal gammopathy at the first survey, revealed the occurrence of immunoglobulin suppression in 4 patients. The relative risk between the persons exposed to 0.01 Gy or more and non-exposed persons was 2.0 for monoclonal gammopathy of undetermined significance and 1.3 for benign monoclonal gammopathy; however, this was not statistically significant. (N.K.) 50 refs

  3. Trumpeting M dwarfs with CONCH-SHELL: a catalogue of nearby cool host-stars for habitable exoplanets and life

    Science.gov (United States)

    Gaidos, E.; Mann, A. W.; Lépine, S.; Buccino, A.; James, D.; Ansdell, M.; Petrucci, R.; Mauas, P.; Hilton, E. J.

    2014-09-01

    We present an all-sky catalogue of 2970 nearby (d ≲ 50 pc), bright (J stars, 86 per cent of which have been confirmed by spectroscopy. This catalogue will be useful for searches for Earth-size and possibly Earth-like planets by future space-based transit missions and ground-based infrared Doppler radial velocity surveys. Stars were selected from the SUPERBLINK proper motion catalogue according to absolute magnitudes, spectra, or a combination of reduced proper motions and photometric colours. From our spectra, we determined gravity-sensitive indices, and identified and removed 0.2 per cent of these as interloping hotter or evolved stars. 13 per cent of the stars exhibit Hα emission, an indication of stellar magnetic activity and possible youth. The mean metallicity is [Fe/H] = -0.07 with a standard deviation of 0.22 dex, similar to nearby solar-type stars. We determined stellar effective temperatures by least-squares fitting of spectra to model predictions calibrated by fits to stars with established bolometric temperatures, and estimated radii, luminosities, and masses using empirical relations. Six per cent of stars with images from integral field spectra are resolved doubles. We inferred the planet population around M dwarfs using Kepler data and applied this to our catalogue to predict detections by future exoplanet surveys.

  4. 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

  5. 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.

  6. Set-up of a High-Resolution 300 mK Atomic Force Microscope in an Ultra-High Vacuum Compatible 3He/10T Cryostat

    CERN Document Server

    von Allwörden, Henning; Köhler, Arne; Eelbo, Thomas; Schwarz, Alexander; Wiesendanger, Roland

    2016-01-01

    The design of an atomic force microscope with an all-fiber interferometric detection scheme capable of atomic resolution at about 500 mK is presented. The microscope body is connected to a small pumped 3He reservoir with a base temperature of about 300 mK. The bakeable insert with the cooling stage can be moved from its measurement position inside the bore of a superconducting 10 T magnet into an ultra-high vacuum chamber, where tip and sample can be exchanged in-situ. Moreover, single atoms or molecules can be evaporated onto a cold substrate located inside the microscope. Two side chambers are equipped with standard surface preparation and surface analysis tools. The performance of the microscope at low temperatures is demonstrated by resolving single Co atoms on Mn/W(110) and by showing atomic resolution on NaCl(001).

  7. Set-up of a high-resolution 300 mK atomic force microscope in an ultra-high vacuum compatible (3)He/10 T cryostat.

    Science.gov (United States)

    von Allwörden, H; Ruschmeier, K; Köhler, A; Eelbo, T; Schwarz, A; Wiesendanger, R

    2016-07-01

    The design of an atomic force microscope with an all-fiber interferometric detection scheme capable of atomic resolution at about 500 mK is presented. The microscope body is connected to a small pumped (3)He reservoir with a base temperature of about 300 mK. The bakeable insert with the cooling stage can be moved from its measurement position inside the bore of a superconducting 10 T magnet into an ultra-high vacuum chamber, where the tip and sample can be exchanged in situ. Moreover, single atoms or molecules can be evaporated onto a cold substrate located inside the microscope. Two side chambers are equipped with standard surface preparation and surface analysis tools. The performance of the microscope at low temperatures is demonstrated by resolving single Co atoms on Mn/W(110) and by showing atomic resolution on NaCl(001). PMID:27475560

  8. Set-up of a high-resolution 300 mK atomic force microscope in an ultra-high vacuum compatible 3He/10 T cryostat

    Science.gov (United States)

    von Allwörden, H.; Ruschmeier, K.; Köhler, A.; Eelbo, T.; Schwarz, A.; Wiesendanger, R.

    2016-07-01

    The design of an atomic force microscope with an all-fiber interferometric detection scheme capable of atomic resolution at about 500 mK is presented. The microscope body is connected to a small pumped 3He reservoir with a base temperature of about 300 mK. The bakeable insert with the cooling stage can be moved from its measurement position inside the bore of a superconducting 10 T magnet into an ultra-high vacuum chamber, where the tip and sample can be exchanged in situ. Moreover, single atoms or molecules can be evaporated onto a cold substrate located inside the microscope. Two side chambers are equipped with standard surface preparation and surface analysis tools. The performance of the microscope at low temperatures is demonstrated by resolving single Co atoms on Mn/W(110) and by showing atomic resolution on NaCl(001).

  9. 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...

  10. 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)

  11. Set-up of a High-Resolution 300 mK Atomic Force Microscope in an Ultra-High Vacuum Compatible 3He/10T Cryostat

    OpenAIRE

    von Allwörden, Henning; Ruschmeier, Kai; Köhler, Arne; Eelbo, Thomas; Schwarz, Alexander; Wiesendanger, Roland

    2016-01-01

    The design of an atomic force microscope with an all-fiber interferometric detection scheme capable of atomic resolution at about 500 mK is presented. The microscope body is connected to a small pumped 3He reservoir with a base temperature of about 300 mK. The bakeable insert with the cooling stage can be moved from its measurement position inside the bore of a superconducting 10 T magnet into an ultra-high vacuum chamber, where tip and sample can be exchanged in-situ. Moreover, single atoms ...

  12. Atomic diffusion and mixing in old stars VI: The lithium content of M30

    CERN Document Server

    Gruyters, Pieter; Richard, Olivier; Grundahl, Frank; Asplund, Martin; Casagrande, Luca; Charbonnel, Corinne; Milone, Antonino; Primas, Francesca; Korn, Andreas J

    2016-01-01

    The prediction of the PLANCK-constrained primordial lithium abundance in the Universe is in discordance with the observed Li abundances in warm Population II dwarf and subgiant stars. Among the physically best motivated ideas, it has been suggested that this discrepancy can be alleviated if the stars observed today had undergone photospheric depletion of lithium. The cause of this depletion is investigated by accurately tracing the behaviour of the lithium abundances as a function of effective temperature. Globular clusters are ideal laboratories for such an abundance analysis as the relative stellar parameters of their stars can be precisely determined. We performed a homogeneous chemical abundance analysis of 144 stars in the metal-poor globular cluster M30, ranging from the cluster turnoff point to the tip of the red giant branch. NLTE abundances for Li, Ca, and Fe were derived where possible. Stellar parameters were derived by matching isochrones to the observed V vs V-I colour-magnitude diagram. Independ...

  13. 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...

  14. Laplace-transformed atomic orbital-based M{\\o}ller-Plesset perturbation theory for relativistic two-component Hamiltonians

    CERN Document Server

    Helmich-Paris, Benjamin; Visscher, Lucas

    2016-01-01

    We present a formulation of Laplace-transformed atomic orbital-based second-order M{\\o}ller-Plesset perturbation theory (MP2) energies for two-component Hamiltonians in the Kramers-restricted formalism. This low-order scaling technique can be used to enable correlated relativistic calculations for large molecular systems. We show that the working equations to compute the relativistic MP2 energy differ by merely a change of algebra (quaternion instead of real) from their non-relativistic counterparts. With a proof-of-principle implementation we study the effect of the nuclear charge on the magnitude of half-transformed integrals and show that for light elements spin-free and spin-orbit MP2 energies are almost identical. Furthermore, we investigate the effect of separation of charge distributions on the Coulomb and exchange energy con- tributions, which show the same long-range decay with the inter-electronic / atomic distance as for non-relativistic MP2. A linearly scaling implementation is possible if the pro...

  15. Detection of a large fraction of atomic gas not associated with star-forming material in M17 SW

    CERN Document Server

    Perez-Beaupuits, J P; Ossenkopf, V; Spaans, M; Gusten, R; Wiesemeyer, H

    2015-01-01

    We probe the column densities and masses traced by the ionized and neutral atomic carbon with spectrally resolved maps, and compare them to the diffuse and dense molecular gas traced by [C I] and low-$J$ CO lines toward the star-forming region M17SW. We mapped a 4.1pc x 4.7pc region in the [C I] 609 m$\\mu$ line using the APEX telescope, as well as the CO isotopologues with the IRAM 30m telescope. We analyze the data based on velocity channel maps that are 1 km/s wide. We correlate their spatial distribution with that of the [C II] map obtained with SOFIA/GREAT. Optically thin approximations were used to estimate the column densities of [C I] and [C II] in each velocity channel. The spatial distribution of the [C I] and all CO isotopologues emission was found to be associated with that of [C II] in about 20%-80% of the mapped region, with the high correlation found in the central (15-23 km/s ) velocity channels. The excitation temperature of [C I] ranges between 40 K and 100 K in the inner molecular region of ...

  16. Diffuse Interstellar Bands vs. Known Atomic and Molecular Species in the Interstellar Medium of M82 toward SN 2014J

    CERN Document Server

    Welty, Daniel E; Dahlstrom, Julie A; York, Donald G

    2014-01-01

    We discuss the absorption due to various constituents of the interstellar medium of M82 seen in moderately high resolution, high signal-to-noise ratio optical spectra of SN 2014J. Complex absorption from M82 is seen, at velocities 45 $\\le$ $v_{\\rm LSR}$ $\\le$ 260 km s$^{-1}$, for Na I, K I, Ca I, Ca II, CH, CH$^+$, and CN; many of the diffuse interstellar bands (DIBs) are also detected. Comparisons of the column densities of the atomic and molecular species and the equivalent widths of the DIBs reveal both similarities and differences in relative abundances, compared to trends seen in the ISM of our Galaxy and the Magellanic Clouds. Of the ten relatively strong DIBs considered here, six (including $\\lambda$5780.5) have strengths within $\\pm$20% of the mean values seen in the local Galactic ISM, for comparable N(K I); two are weaker by 20--45% and two (including $\\lambda$5797.1) are stronger by 25--40%. Weaker than "expected" DIBs [relative to N(K I), N(Na I), and E(B-V)] in some Galactic sight lines and towar...

  17. 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

  18. Y2O3:Yb,Er@mSiO2-Cu(x)S double-shelled hollow spheres for enhanced chemo-/photothermal anti-cancer therapy and dual-modal imaging.

    Science.gov (United States)

    Yang, Dan; Yang, Guixin; Wang, Xingmei; Lv, Ruichan; Gai, Shili; He, Fei; Gulzar, Arif; Yang, Piaoping

    2015-07-28

    Multifunctional composites have gained significant interest due to their unique properties which show potential in biological imaging and therapeutics. However, the design of an efficient combination of multiple diagnostic and therapeutic modes is still a challenge. In this contribution, Y2O3:Yb,Er@mSiO2 double-shelled hollow spheres (DSHSs) with up-conversion fluorescence have been successfully prepared through a facile integrated sacrifice template method, followed by a calcination process. It is found that the double-shelled structure with large specific surface area and uniform shape is composed of an inner shell of luminescent Y2O3:Yb,Er and an outer mesoporous silica shell. Ultra small Cu(x)S nanoparticles (about 2.5 nm) served as photothermal agents, and a chemotherapeutic agent (doxorubicin, DOX) was then attached onto the surface of mesoporous silica, forming a DOX-DSHS-Cu(x)S composite. The composite exhibits high anti-cancer efficacy due to the synergistic photothermal therapy (PTT) induced by the attached Cu(x)S nanoparticles and the enhanced chemotherapy promoted by the heat from the Cu(x)S-based PTT when irradiated by 980 nm near-infrared (NIR) light. Moreover, the composite shows excellent in vitro and in vivo X-ray computed tomography (CT) and up-conversion fluorescence (UCL) imaging properties owing to the doped rare earth ions, thus making it possible to achieve the target of imaging-guided synergistic therapy. PMID:26132588

  19. 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.

  20. 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...

  1. 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)

  2. Detection of a large fraction of atomic gas not associated with star-forming material in M17 SW⋆

    Science.gov (United States)

    Pérez-Beaupuits, J. P.; Stutzki, J.; Ossenkopf, V.; Spaans, M.; Güsten, R.; Wiesemeyer, H.

    2015-03-01

    Context. The [C II] 158 μm line is one of the dominant coolants of the ISM, and an important probe with which to study the star formation process. Recent Herschel/HIFI and SOFIA/GREAT observations showed that assuming the total velocity-integrated intensity of this line is directly associated with the star-forming material is inadequate. Aims: We probe the column densities and masses traced by the ionized and neutral atomic carbon with spectrally resolved maps, and compare them to the diffuse and dense molecular gas traced by [C I] and low-J CO lines toward the star-forming region M17 SW. Methods: We mapped a 4.1 pc × 4.7 pc region in the [C I] 609 μm line using the APEX telescope, as well as the CO isotopologues with the IRAM 30 m telescope. Because of the velocity-resolved spectra, we analyze the data based on velocity channel maps that are 1 km s-1 wide. We correlate their spatial distribution with that of the [C II] map obtained with SOFIA/GREAT. Optically thin approximations were used to estimate the column densities of [C I] and [C II] in each velocity channel. Results: The distribution of the emission from the isotopologues 13CO, C17O, and C18O resembles more closely that of the [C I] emission than that of the 12CO emission. The spatial distribution of the [C I] and all CO isotopologues emission was found to be associated with that of [C II] in about 20%-80% of the mapped region, with the high correlation found in the central (15-23 km s-1) velocity channels. Conclusions: The excitation temperature of [C I] ranges between 40 K and 100 K in the inner molecular region of M17 SW. Excitation temperatures up to 200 K are found along the ridge. Column densities in 1 km s-1 channels between ~1015 cm-2 and ~1017 cm-2 were found for [C I]. Just ~20 % of the velocity range (~40 km s-1) that the [C II] line spans is associated with the star-forming material traced by [C I] and CO. The total (integrated over the 0-40 km s-1 velocity range) gas mass estimated from the

  3. Diffuse Interstellar Bands versus Known Atomic and Molecular Species in the Interstellar Medium of M82 toward SN 2014J

    Science.gov (United States)

    Welty, Daniel E.; Ritchey, Adam M.; Dahlstrom, Julie A.; York, Donald G.

    2014-09-01

    We discuss the absorption due to various constituents of the interstellar medium (ISM) of M82 seen in moderately high-resolution, high signal-to-noise ratio optical spectra of SN 2014J. Complex absorption from M82 is seen, at velocities 45 <~ v LSR <~ 260 km s-1, for Na I, K I, Ca I, Ca II, CH, CH+, and CN; many of the diffuse interstellar bands (DIBs) are also detected. Comparisons of the column densities of the atomic and molecular species and the equivalent widths of the DIBs reveal both similarities and differences in relative abundances, compared to trends seen in the ISM of our Galaxy and the Magellanic Clouds. Of the 10 relatively strong DIBs considered here, 6 (including λ5780.5) have strengths within ±20% of the mean values seen in the local Galactic ISM, for comparable N(K I); 2 are weaker by 20%-45% and 2 (including λ5797.1) are stronger by 25%-40%. Weaker than "expected" DIBs (relative to N(K I), N(Na I), and E(B - V)) in some Galactic sight lines and toward several other extragalactic supernovae appear to be associated with strong CN absorption and/or significant molecular fractions. While the N(CH)/N(K I) and N(CN)/N(CH) ratios seen toward SN 2014J are similar to those found in the local Galactic ISM, the combination of high N(CH+)/N(CH) and high W(5797.1)/W(5780.5) ratios has not been seen elsewhere. The centroids of many of the M82 DIBs are shifted relative to the envelope of the K I profile—likely due to component-to-component variations in W(DIB)/N(K I) that may reflect the molecular content of the individual components. We compare estimates for the host galaxy reddening E(B - V) and visual extinction A V derived from the various interstellar species with the values estimated from optical and near-IR photometry of SN 2014J.

  4. Diffuse interstellar bands versus known atomic and molecular species in the interstellar medium of M82 toward SN 2014J

    International Nuclear Information System (INIS)

    We discuss the absorption due to various constituents of the interstellar medium (ISM) of M82 seen in moderately high-resolution, high signal-to-noise ratio optical spectra of SN 2014J. Complex absorption from M82 is seen, at velocities 45 ≲ v LSR ≲ 260 km s–1, for Na I, K I, Ca I, Ca II, CH, CH+, and CN; many of the diffuse interstellar bands (DIBs) are also detected. Comparisons of the column densities of the atomic and molecular species and the equivalent widths of the DIBs reveal both similarities and differences in relative abundances, compared to trends seen in the ISM of our Galaxy and the Magellanic Clouds. Of the 10 relatively strong DIBs considered here, 6 (including λ5780.5) have strengths within ±20% of the mean values seen in the local Galactic ISM, for comparable N(K I); 2 are weaker by 20%-45% and 2 (including λ5797.1) are stronger by 25%-40%. Weaker than 'expected' DIBs (relative to N(K I), N(Na I), and E(B – V)) in some Galactic sight lines and toward several other extragalactic supernovae appear to be associated with strong CN absorption and/or significant molecular fractions. While the N(CH)/N(K I) and N(CN)/N(CH) ratios seen toward SN 2014J are similar to those found in the local Galactic ISM, the combination of high N(CH+)/N(CH) and high W(5797.1)/W(5780.5) ratios has not been seen elsewhere. The centroids of many of the M82 DIBs are shifted relative to the envelope of the K I profile—likely due to component-to-component variations in W(DIB)/N(K I) that may reflect the molecular content of the individual components. We compare estimates for the host galaxy reddening E(B – V) and visual extinction A V derived from the various interstellar species with the values estimated from optical and near-IR photometry of SN 2014J.

  5. Diffuse interstellar bands versus known atomic and molecular species in the interstellar medium of M82 toward SN 2014J

    Energy Technology Data Exchange (ETDEWEB)

    Welty, Daniel E.; York, Donald G. [Department of Astronomy and Astrophysics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States); Ritchey, Adam M. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States); Dahlstrom, Julie A., E-mail: dwelty@oddjob.uchicago.edu [Department of Physics and Astronomy, Carthage College, 2001 Alford Park Drive, Kenosha, WI 53140 (United States)

    2014-09-10

    We discuss the absorption due to various constituents of the interstellar medium (ISM) of M82 seen in moderately high-resolution, high signal-to-noise ratio optical spectra of SN 2014J. Complex absorption from M82 is seen, at velocities 45 ≲ v {sub LSR} ≲ 260 km s{sup –1}, for Na I, K I, Ca I, Ca II, CH, CH{sup +}, and CN; many of the diffuse interstellar bands (DIBs) are also detected. Comparisons of the column densities of the atomic and molecular species and the equivalent widths of the DIBs reveal both similarities and differences in relative abundances, compared to trends seen in the ISM of our Galaxy and the Magellanic Clouds. Of the 10 relatively strong DIBs considered here, 6 (including λ5780.5) have strengths within ±20% of the mean values seen in the local Galactic ISM, for comparable N(K I); 2 are weaker by 20%-45% and 2 (including λ5797.1) are stronger by 25%-40%. Weaker than 'expected' DIBs (relative to N(K I), N(Na I), and E(B – V)) in some Galactic sight lines and toward several other extragalactic supernovae appear to be associated with strong CN absorption and/or significant molecular fractions. While the N(CH)/N(K I) and N(CN)/N(CH) ratios seen toward SN 2014J are similar to those found in the local Galactic ISM, the combination of high N(CH{sup +})/N(CH) and high W(5797.1)/W(5780.5) ratios has not been seen elsewhere. The centroids of many of the M82 DIBs are shifted relative to the envelope of the K I profile—likely due to component-to-component variations in W(DIB)/N(K I) that may reflect the molecular content of the individual components. We compare estimates for the host galaxy reddening E(B – V) and visual extinction A {sub V} derived from the various interstellar species with the values estimated from optical and near-IR photometry of SN 2014J.

  6. Atomic and electronic structure of free niobium nanoclusters: Simulation of the M{sub 4,5}-XANES spectrum of Nb{sub 13}{sup +}

    Energy Technology Data Exchange (ETDEWEB)

    Kravtsova, Antonina N., E-mail: akravtsova@sfedu.ru [Research Center for Nanoscale Structure of Matter, Southern Federal University, Sorge str. 5, 344090 Rostov-on-Don (Russian Federation); Lomachenko, Kirill A. [Research Center for Nanoscale Structure of Matter, Southern Federal University, Sorge str. 5, 344090 Rostov-on-Don (Russian Federation); Department of Chemistry and NIS Centre of Excellence, University of Turin, Via P. Giuria 7, 10125 Turin (Italy); Soldatov, Alexander V., E-mail: soldatov@sfedu.ru [Research Center for Nanoscale Structure of Matter, Southern Federal University, Sorge str. 5, 344090 Rostov-on-Don (Russian Federation); Meyer, Jennifer; Niedner-Schatteburg, Gereon [Technische Universität Kaiserslautern, Fachbereich Chemie und Forschungszentrum OPTIMAS, Erwin-Schrödinger-Straße 52, 67663 Kaiserslautern (Germany); Peredkov, Sergey [Helmholtz-Zentrum Berlin für Materialien und Energie, Wilhelm-Conrad-Röntgen-Campus Adlershof, Elektronenspeicherring BESSY II, Albert-Einstein-Straße 15, Berlin (Germany); Eberhardt, Wolfgang [Technische Universität Berlin, IOAP, Straße des 17. Juni 135, 10623 Berlin (Germany); Neeb, Matthias, E-mail: matthias.neeb@helmholtz-berlin.de [Helmholtz-Zentrum Berlin für Materialien und Energie, Wilhelm-Conrad-Röntgen-Campus Adlershof, Elektronenspeicherring BESSY II, Albert-Einstein-Straße 15, Berlin (Germany)

    2014-08-15

    Highlights: • M{sub 4,5}-XANES spectra have been calculated for several structural models of free Nb{sub 13}{sup +} cluster. • Theoretical M{sub 4,5}-XANES have been compared with the experimental spectrum of free Nb{sub 13}{sup +}. • Icosahedral structure of Nb{sub 13}{sup +} shows better agreement with experiment than the “amorphous” one. • Distance between Nb atoms in the icosahedral cluster is distinctly reduced as compared to the bulk phase. - Abstract: The atomic and electronic structure of free niobium nanoclusters has been studied on the basis of X-ray absorption near-edge structure (XANES) spectroscopy and density functional theory. M{sub 4,5}-XANES spectra have been calculated for several structural models of the 13-atomic niobium cluster. The calculations have been done on the basis of both full multiple scattering theory within the muffin-tin approximation for a potential and full-potential finite difference method. The comparison of the experimental M{sub 4,5}-edge XANES spectrum (Peredkov et al., J. Electron Spectros. Relat. Phenomena 184 (2011) 113–118) with the simulated X-ray absorption spectra of Nb{sub 13}{sup +} hints to a highly-symmetric icosahedral structure of the cluster. An internuclear distance of 2.2 ± 0.1 Å between neighboring “surface” atoms of the icosahedron and 2.09 Å between the central “bulk” atom and “surface” atoms, respectively, has been found upon comparison of the experimental and theoretical XANES spectra.

  7. 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

  8. 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.

  9. Core/shell composites with polystyrene cores and meso-silica shells as abrasives for improved chemical mechanical polishing behavior

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Yang, E-mail: cy.jpu@126.com; Qin, Jiawei; Wang, Yayun; Li, Zefeng [Changzhou University, School of Material Science and Engineering (China)

    2015-09-15

    The core/shell-structured organic/inorganic composite abrasive has an important potential application in damage-free chemical mechanical polishing (CMP) due to its non-rigid mechanical property. In this work, the PS/{sub M}SiO{sub 2} composites, containing polystyrene (PS) sphere (211 ± 4 nm) cores and mesoporous silica shells (31 ± 3 nm in thickness) were synthesized through directed surface sol–gel process of tetraethylorthosilicate on the polymer cores in the presence of the cetyltrimethylammonium bromide surfactant. For comparison, the conventional core/shell PS/{sub N}SiO{sub 2} composites with non-porous silica shells were also prepared via a modified Stöber procedure that involved the hydrolysis of TEOS under acidic condition. The physical properties of the samples were examined by small-angle X-ray diffraction, fourier transform infrared spectroscopy, thermogravimetric analysis, transmission electron microscopy, field emission scanning electron microscopy, and nitrogen adsorption–desorption. As novel abrasives, the core/shell-structured PS/{sub M}SiO{sub 2} composites were introduced into the CMP process for silicon oxide films. The oxide-CMP performance among conventional solid silica particles, PS/{sub N}SiO{sub 2} composites, and novel PS/{sub M}SiO{sub 2} composites was explored by atomic force microscopy. Polishing results indicated that the substrate revealed a comparable root-mean-square surface roughness (0.25 ± 0.03 and 0.22 ± 0.02 nm, respectively) after CMP with PS/{sub N}SiO{sub 2} and PS/{sub M}SiO{sub 2} abrasives under the same polishing conditions. However, the material removal rate of the PS/{sub M}SiO{sub 2} composites (123 ± 15 nm/min) was about three times larger than that of the PS/{sub N}SiO{sub 2} composites (47 ± 13 nm/min). The reduced surface roughness and improved removal rate might be due to the optimization of the physical and/or chemical environments in the local contacting region between abrasives

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

    Science.gov (United States)

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

    2012-07-01

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

  11. Fabrication of the novel core-shell MCM-41@mTiO2 composite microspheres with large specific surface area for enhanced photocatalytic degradation of dinitro butyl phenol (DNBP)

    Science.gov (United States)

    Wei, Xiao-Na; Wang, Hui-Long; Li, Zhen-Duo; Huang, Zhi-Qiang; Qi, Hui-Ping; Jiang, Wen-Feng

    2016-05-01

    The mesoporous MCM-41@mTiO2 core-shell composite microspheres were synthesized successfully by combining sol-gel and simple hydrothermal treatment. The morphology and microstructure characteristics of the synthesized materials were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption-desorption measurements, X-ray powder diffraction (XRD), UV-vis diffuse reflectance spectra (UV-vis/DRS) and Fourier transform infrared spectroscopy (FT-IR). The results indicate that the composite material possesses obvious core/shell structure, a pure mesoporous and well-crystallized TiO2 layer (mTiO2), high specific surface area (316.8 m2/g), large pore volume (0.42 cm3/g) and two different pore sizes (2.6 nm and 11.0 nm). The photocatalytic activity of the novel MCM-41@mTiO2 composite was evaluated by degrading 2-sec-butyl-4,6-dinitrophenol (DNBP) in aqueous suspension under UV and visible light irradiation. The results were compared with commercial anatase TiO2 and Degussa P25 and the enhanced degradation were obtained with the synthesized MCM-41@mTiO2 composite under the same conditions, which meant that this material can serve as an efficient photocatalyst for the degradation of hazardous organic pollutants in wastewaters.

  12. Elemental Analysis of Shells by Nuclear Technique

    International Nuclear Information System (INIS)

    Quantitative analysis of strontium(Sr) and calcium(Ca) in fresh water shell and sea shell was studied by X-ray Fluorescence (XRF) technique with Emission-Transmission(E-T) method, using isotope X-ray sources of plutonium-238(Pu-238) and americium-241(Am-241), and comparing with Neutron Activation Analysis technique in TRR-1/M1 reactor. The results show that the calcium content in both types of shells are almost the same, but strontium in sea shell is 3-4 times higher than that in fresh water shell. Moreover, the results can verify the region that used to be the river or ocean. The high ratio of strontium to calcium in many types of the shells from Wat Jaedeehoi, Patumthanee province show the specific character of sea shell.So it can be concluded that this region used to be the ocean in the past

  13. Stability of core–shell nanowires in selected model solutions

    Energy Technology Data Exchange (ETDEWEB)

    Kalska-Szostko, B., E-mail: kalska@uwb.edu.pl; Wykowska, U.; Basa, A.; Zambrzycka, E.

    2015-03-30

    Highlights: • Stability of the core–shell nanowires in environmental solutions were tested. • The most and the least aggressive solutions were determined. • The influence of different solutions on magnetic nanowires core was found out. - Abstract: This paper presents the studies of stability of magnetic core–shell nanowires prepared by electrochemical deposition from an acidic solution containing iron in the core and modified surface layer. The obtained nanowires were tested according to their durability in distilled water, 0.01 M citric acid, 0.9% NaCl, and commercial white wine (12% alcohol). The proposed solutions were chosen in such a way as to mimic food related environment due to a possible application of nanowires as additives to, for example, packages. After 1, 2 and 3 weeks wetting in the solutions, nanoparticles were tested by Infrared Spectroscopy, Atomic Absorption Spectroscopy, Transmission Electron Microscopy and X-ray diffraction methods.

  14. Stability of core–shell nanowires in selected model solutions

    International Nuclear Information System (INIS)

    Highlights: • Stability of the core–shell nanowires in environmental solutions were tested. • The most and the least aggressive solutions were determined. • The influence of different solutions on magnetic nanowires core was found out. - Abstract: This paper presents the studies of stability of magnetic core–shell nanowires prepared by electrochemical deposition from an acidic solution containing iron in the core and modified surface layer. The obtained nanowires were tested according to their durability in distilled water, 0.01 M citric acid, 0.9% NaCl, and commercial white wine (12% alcohol). The proposed solutions were chosen in such a way as to mimic food related environment due to a possible application of nanowires as additives to, for example, packages. After 1, 2 and 3 weeks wetting in the solutions, nanoparticles were tested by Infrared Spectroscopy, Atomic Absorption Spectroscopy, Transmission Electron Microscopy and X-ray diffraction methods

  15. Experimental study of thermohydraulic processes and gas distribution in a model of the containment shell of the AST-500 reactor

    International Nuclear Information System (INIS)

    Experiments were made on a setup consisting of a large-scale twin-assembly model of the primary circuit of an integral reactor and of a model of a containment shell which is a means for confining the outflow of coolant from the reactor. The large-scale model of an AST-500 reactor has vertical dimensions close to the actual dimensions and similar coefficients of hydraulic resistance and volume ratios of the principal elements the circuit with natural circulation. The model of the containment shell is a vertical cylindrical vessel with a size of 426 x 12 mm, a height of 9.78 m, and a volume of 1.24 m3. The volume scale of the reactor model and of the model of the containment shell is 1:170. The elements of the latter model are made from steel 20. The models of the reactor and of the containment shell are joined through two pipelines with a size of 57 x 3.5 mm and shut-off valves with a diameter of 50 mm mounted thereon. A total of 70 experiments were made to simulate leakage of the primary circuit of the integrated reactor and the outflow of coolant into the containment shell. The authors have provided detailed information on the large-scale model, have described the experimental conditions, and have reported on the main results of their study of the development of an accident involving the loss of coolant in the reactor-containment shell system. The present article reports on a study of the thermohydraulic processes and the gas distribution in the containment shell. Since the designs of the model and of the actual containment shell of the AST-500 reactor are not identical, the authors assume that the results reported can be used in appropriate computer programs describing the processes which occur in containment vessels of atomic power stations (containment shells, protective shells, sealed assemblies)

  16. 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。

  17. 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

  18. Atomic site preferences and its effect on magnetic structure in the intermetallic borides M2Fe(Ru0.8T0.2)5B2 (M=Sc, Ti, Zr; T=Ru, Rh, Ir)

    International Nuclear Information System (INIS)

    The site preference for a class of intermetallic borides following the general formula M2Fe(Ru0.8T0.2)5B2 (M=Sc, Ti, Zr; T=Ru, Rh, Ir), has been explored using ab initio and semi-empirical electronic structure calculations. This intermetallic boride series contains two potential sites, the Wyckoff 2c and 8j sites, for Rh or Ir to replace Ru atoms. Since the 8j site is a nearest neighbor to the magnetically active Fe atom, whereas the 2c site is a next nearest neighbor, the substitution pattern should play an important role in the magnetic structure of these compounds. The substitution preference is analyzed based on the site energy and bond energy terms, both of which arise from a tight-binding evaluation of the electronic band energy, and are known to influence the locations of atoms in extended solids. According to these calculations, the valence electron-rich Rh and Ir atoms prefer to occupy the 8j site, a result also corroborated by experimental evidence. Additionally, substitution of Rh or Ir at the 8j site results in a modification of the magnetic structure that ultimately results in larger local magnetic moment on the Fe atoms. - Graphical abstract: The site preference for electron rich atoms to occupy the 8j (gray) site is identified in these intermetallic borides, while the magnetic structure is modified as a function of the substituted atoms band center. Highlights: ► We identify the energetics dictating the site preference in a series of intermetallic borides. ► Establish substitution rules for use in future directed synthetic preparations. ► Identified changes in magnetic structure that accompany the site preference.

  19. mJ mixing and multipole relaxation in 6 2P rubidium atoms induced by He, Ne, and Ar collisions

    International Nuclear Information System (INIS)

    Rubidium vapor, contained together with a buffer gas in a quartz cell located in a 4.75-T magnetic field, was irradiated with light from a pulsed dye laser producing selective excitation of each 6 2P Zeeman substate in turn. Collisions of the excited and polarized atoms with the ground-state He, Ne, or Ar atoms and the resulting Zeeman mixing produced a population of the whole Zeeman manifold and resulted in the emission of a Zeeman fluorescence spectrum that was resolved with a scanning Fabry-Perot interferometer and recorded with a photomultiplier and a multichannel scaler. Measurements of the relative intensities of the fluorescence components in relation to the buffer-gas pressures yielded the absolute (thermally averaged) cross sections for Zeeman mixing and cross sections for relaxation of the atomic multipole moments for collisions with He, Ne, and Ar

  20. Yields and ionization probabilities of sputtered In {sub n} particles under atomic and polyatomic Au {sub m} {sup -} ion bombardment

    Energy Technology Data Exchange (ETDEWEB)

    Samartsev, A.V. [Physics Department, University of Duisburg-Essen, 47048 Duisburg (Germany); Wucher, A. [Physics Department, University of Duisburg-Essen, 47048 Duisburg (Germany)]. E-mail: wucher@uni-essen.de

    2006-07-30

    The emission of neutral and charged atoms and clusters from a polycrystalline indium surface under bombardment with 5 and 10 keV Au, Au{sub 2}, Au{sub 3} and Au{sub 5} projectiles was investigated. Single photon laser postionization was utilized for the detection of sputtered neutral particles. Secondary ions were detected without the laser under otherwise exactly the same experimental conditions. The relative cluster yields were found to be enhanced under polyatomic projectile bombardment, more so the larger the number of atoms in the sputtered cluster. The ionization probability strongly increases with increasing cluster size, but is essentially independent of the projectile impact energy. At a fixed impact energy, the ionization probability of sputtered monomers was found to decrease with increasing number of constituent gold atoms per projectile, but there was no detectable effect for sputtered dimers and larger clusters.

  1. A model of Kirkendall hollowing of core–shell nanowires and nanoparticles controlled by short-circuit diffusion

    International Nuclear Information System (INIS)

    We propose a model for the hollowing of the core–shell nanowires caused by the Kirkendall effect during chemical reaction (oxidation) on the nanowire surface. We consider the self-diffusion of the atoms of the core along the grain boundaries in the shell, on the exposed surface of the core, and along the core–shell interface as the main factors controlling the hollowing kinetics. The model relies on the variational method of calculating the chemical potential of the metal atoms diffusing along the core–shell interphase boundary. A comparison of model predictions with the results of hollowing studies of Ni–NiO core–shell nanoparticles [J.G. Railsback et al., ACS Nano 4 (2010) 1913–1920] gave a value for the self-diffusion coefficient of Ni along the grain boundaries in NiO at 573 K of 3 × 10−20 m2 s−1, in good agreement with the literature data. We demonstrate that high values of the contact angle of the core on the shell promote pore instability and formation of secondary side pores (pores multiplication)

  2. Design, fabrication and testing of a prototype stressed-shell fuel isolation container

    International Nuclear Information System (INIS)

    Atomic Energy of Canada Limited is conducting and coordinating research into the development of engineered barriers for the disposal of unreprocessed irradiated fuel within a deep, stable geologic vault. In one approach, a containment shell of corrosion-resistant metal is proposed as the principal barrier to radionuclide release, giving a high probability of containment for at least 300 years, thus ensuring isolation of nearly all fission products for their hazardous lives. The simplest concept is the 'stressed-shell' container, designed with sufficient shell thickness to withstand the hydrostatic pressure within a 1000-m deep disposal vault postulated to have flooded with groundwater. This report describes the design, fabrication, analysis and hydrostatic testing of a full-scale stressed-shell prototype. The report concludes that the deformation and collapse performance of stressed-shell designs, based on short-term mechanical properties be modelled adequately by BOSOR 5, a commercially available stress-strain computer program. If the stressed-shell concept is retained as a viable fuel isolation concept, future analyses should include an assessment of the role of material creep on long-term container performance

  3. 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

  4. Technical Aspects of Atomic and Molecular Data Processing and Exchange, 22nd Meeting of the A+M Data Centres Network. Summary Report of an IAEA Technical Meeting

    International Nuclear Information System (INIS)

    This report summarizes the proceedings of the IAEA Technical Meeting on ''Technical Aspects of Atomic and Molecular Data Processing and Exchange'' (22nd Meeting of the A+M Data Centres Network) on 4-6 September 2013. Twelve participants from 8 data centres of 6 Member States attended the three-day meeting held at the IAEA Headquarters in Vienna. The report includes discussions on the data issues, meeting conclusions and recommendations and the abstracts of presentations presented in the meeting. (author)

  5. Atomic layer epitaxy of (CdTe) sub m (ZnTe) sub n -ZnTe multiquantum wells on (001)GaAs substrate

    Energy Technology Data Exchange (ETDEWEB)

    Li Jie; He Li; Shan Wei; Cheng Xingyu; Yuan Shixin (Shanghai Inst. of Technical Physics, Academia Sinica (China))

    1991-05-01

    (CdTe){sub m}(ZnTe){sub n}-ZnTe multiquantum well structure has been proposed and grown on (001)GaAs substrate by atomic layer epitaxy. Growth has been investigated using reflection high energy electron diffraction. Material characterizations have been performed by X-ray diffraction and photoluminescence. With this structure, great improvements have been made in crystalline quality compared with CdTe-ZnTe multiquantum wells, due to the reduction of misfit dislocations. (orig.).

  6. Magnetic ordering and exchange interactions in structural modifications of M n3Ga alloys: Interplay of frustration, atomic order, and off-stoichiometry

    Science.gov (United States)

    Khmelevskyi, Sergii; Ruban, Andrei V.; Mohn, Peter

    2016-05-01

    Mn-Ga alloys close to the M n3Ga stoichiometry can be synthesized in three different crystal modifications: hexagonal, tetragonal, and face-centered cubic, both in bulk and in thin-film forms. The magnetic ordering of these modifications is varying from noncollinear antiferromagnetic in the hexagonal case to ferrimagnetic order in the tetragonal one, whereas it is still unknown for the atomically disordered fcc structure. Here we study the onset of magnetic order at finite temperatures in these systems on a first-principles basis calculating the interatomic magnetic exchange interactions in the high-temperature paramagnetic regime. We employ the disordered local moment formalism and the magnetic force theorem within the framework of the local spin-density approximation and Monte Carlo simulations taking also the effects of atomic disorder in fcc alloys into account. In particular we find the origin of the stabilization of the noncollinear 3 k structure in competition between antiferromagnetic inter- and in-plane couplings of frustrated kagome planes in hexagonal M n3Ga and predict the antiferromagnetic-1 collinear order due to frustration in fcc alloys. Special attention is paid to the effects of the off-stoichiometry and the consequences of atomic disorder. We calculate the site-preference energy of Ga antisite atoms in the tetragonal structures in the range of the compositions from M n3Ga to M n2Ga and slightly beyond and confirm the earlier explanation of the effect of magnetization increase due to Ga preferentially occupying one of the Mn sites.

  7. Direct observation of transient fluorine atoms with 25-μm wavelength-stabilized diode laser absorption

    International Nuclear Information System (INIS)

    Through the use of continuous diode laser absorption, detection of transient fluorine atoms with an initial number density in the range of 1014 cm-3 has been demonstrated. A crucial part of the continuous-detection technique was laser frequency stabilization with a reference cell of atomic fluorine with Zeeman modulation of the absorption lines to generate a feedback signal. Long-term wavelength stability was demonstrated with second-harmonic phase-sensitive detection of the second-derivative signal for periods up to several hours. For determination of the short-term wavelength stability in the range of microseconds to seconds, a transient signal was generated by photolysis of F2 with an excimer laser at 308 nm. The initial diode laser absorption was compared to a calculated value obtained from the measured excimer laser fluence, the known dissociation cross section of F2, and the atomic fluorine absorption cross section, which included a statistical population distribution, the finite bandwidth of the laser diode, and the effects of pressure broadening. The observed absorption was approximately 33% less than the calculated value, possibly because of the diode laser's wavelength instability on the time scale of a few seconds, which is consistent with an observed amplitude instability from pulse to pulse when pulsed at 1--10 Hz

  8. Y2O3:Yb,Er@mSiO2-CuxS double-shelled hollow spheres for enhanced chemo-/photothermal anti-cancer therapy and dual-modal imaging

    Science.gov (United States)

    Yang, Dan; Yang, Guixin; Wang, Xingmei; Lv, Ruichan; Gai, Shili; He, Fei; Gulzar, Arif; Yang, Piaoping

    2015-07-01

    Multifunctional composites have gained significant interest due to their unique properties which show potential in biological imaging and therapeutics. However, the design of an efficient combination of multiple diagnostic and therapeutic modes is still a challenge. In this contribution, Y2O3:Yb,Er@mSiO2 double-shelled hollow spheres (DSHSs) with up-conversion fluorescence have been successfully prepared through a facile integrated sacrifice template method, followed by a calcination process. It is found that the double-shelled structure with large specific surface area and uniform shape is composed of an inner shell of luminescent Y2O3:Yb,Er and an outer mesoporous silica shell. Ultra small CuxS nanoparticles (about 2.5 nm) served as photothermal agents, and a chemotherapeutic agent (doxorubicin, DOX) was then attached onto the surface of mesoporous silica, forming a DOX-DSHS-CuxS composite. The composite exhibits high anti-cancer efficacy due to the synergistic photothermal therapy (PTT) induced by the attached CuxS nanoparticles and the enhanced chemotherapy promoted by the heat from the CuxS-based PTT when irradiated by 980 nm near-infrared (NIR) light. Moreover, the composite shows excellent in vitro and in vivo X-ray computed tomography (CT) and up-conversion fluorescence (UCL) imaging properties owing to the doped rare earth ions, thus making it possible to achieve the target of imaging-guided synergistic therapy.Multifunctional composites have gained significant interest due to their unique properties which show potential in biological imaging and therapeutics. However, the design of an efficient combination of multiple diagnostic and therapeutic modes is still a challenge. In this contribution, Y2O3:Yb,Er@mSiO2 double-shelled hollow spheres (DSHSs) with up-conversion fluorescence have been successfully prepared through a facile integrated sacrifice template method, followed by a calcination process. It is found that the double-shelled structure with large

  9. 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.

  10. Application of Bloch oscillations and atomic interferometry for the measurement of the h/m ratio and the determination of the fine structure constant

    International Nuclear Information System (INIS)

    It is possible to determine the h/mRb ratio between the Planck constant and the mass of the atoms, and then to deduce a value of the fine structure constant alpha, from the accurate measurement of the recoil velocity of an atom absorbing a photon. To perform this measurement we combine the high efficiency of Bloch oscillations with the high sensitivity of a Ramsey-Borde interferometer. The Bloch oscillations technic allows us to transfer a large number of recoils to the atoms (up to 1600 recoil momenta). An interferometric Ramsey-Borde velocity sensor, based on velocity selective Raman transitions, allows us to measure the momentum transferred to the atoms. A measurement with a statistical uncertainty of 3 ppb (3*10-9), in conjunction with a careful study of systematic effects (3.4 ppb), lead us to a determination of alpha with a relative uncertainty of 4.8 ppb. The value of α-1 is 137.03599887(65). It is the best determination of alpha, independent from quantum electrodynamics

  11. 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...

  12. Novel search for heavy ν mixing from the β+ decay of K38m confined in an atom trap

    International Nuclear Information System (INIS)

    A new technique, full neutrino momentum reconstruction, is used to set limits on the admixture of heavy neutrinos into the electron neutrino. We measure coincidences between nuclear recoils and positrons from the beta decay of trapped radioactive atoms and deduce the neutrino momentum. A search for peaks in the reconstructed recoil time-of-flight spectrum as a function of positron energy is performed. The admixture upper limits range from 4x10-3 to 2x10-2 and are the best direct limits for neutrinos (as opposed to antineutrinos) for the mass region of 0.7 to 3.5 MeV

  13. 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

  14. Shell-in-Shell TiO2 hollow microspheres and optimized application in light-trapping perovskite solar cells

    Science.gov (United States)

    Sun, Hongxia; Ruan, Peng; Bao, Zhongqiu; Chen, Lei; Zhou, Xingfu

    2015-02-01

    The shell-in-shell structured TiO2 hollow microspheres with enhanced light scattering ability were synthesized via a facile one step hydrothermal process. The diameter of the microsphere is about 1.5 μm, the core of the unique shell-in-shell structure is composed of TiO2 nanoparticles with a diameter of about 15 nm, while the shell is constructed with ∼50 nm TiO2 nanocubes. The hollow space between the outer shell and the inner shell is about 230 nm. The formation mechanism of the unique shell-in-shell structure is interpreted. The design and the optimized application of shell-in-shell structured TiO2 hollow microspheres in the light-trapping perovskite solar cells are also investigated. Owing to the light scattering properties of the shell-in-shell structure of the hollow microsphere, the optimized photoelectrode exhibits an enhanced photoelectric conversion efficiency of 4.29% using perovskite CH3NH3PbI3 as the sensitizer. The shell-in-shell hollow TiO2 microsphere shows a 21.2% increase in conversion efficiency when compared with P25 nanoparticels photoanode. The conversion efficiency enhancement is mainly attributed to the increase of short-current density induced by the light scattering effect.

  15. INVESTIGATION OF PRECAUST PRESTRESSED SHELL

    Directory of Open Access Journals (Sweden)

    Alexander S. Zhiv

    2008-02-01

    Full Text Available  The paper focuses on construction, production and erection of elements, methodology of testing and researching results of precaust prestressed shell from light concrete with dimensions 12×24m, which is used for covering of industrial building.

  16. 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),…

  17. 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)

  18. 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...

  19. 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.

  20. Technical Aspects of Atomic and Molecular Data Processing and Exchange, 21. Meeting of the A+M Data Centres Network. Summary Report of an IAEA Technical Meeting

    International Nuclear Information System (INIS)

    This report summarizes the proceedings of the IAEA Technical Meeting on 'Technical Aspects of Atomic and Molecular Data Processing and Exchange' (21st Meeting of the A+M Data Centres Network) on 7-9 September 2011. Fourteen participants from 12 data centres of 7 Member States and 2 International Organizations attended the three-day meeting held at the IAEA Headquarters in Vienna. The report includes discussions on the data issues, meeting conclusions and recommendations and the abstracts of presentations presented in the meeting. (author)

  1. Large reduction in thermal conductivity for SiGe alloy nanowire wrapped with a Ge nanoparticle-embedded SiO2 shell.

    Science.gov (United States)

    Lee, Jong Woon; Lee, Junho; Jung, Su-Ho; Jang, Yamujin; Choi, Byoung Lyong; Yang, Cheol-Woong; Whang, Dongmok; Lee, Eun Kyung

    2016-07-29

    We demonstrate silicon germanium (SiGe) alloy nanowires (NWs) with Ge nanoparticles (GeNPs) embedded in a SiO2 shell as a material for decreasing thermal conductivity. During thermal oxidation of SiGe NWs to form SiGe-SiO2 core-shell structures, Ge atoms were diffused into the SiO2 shell to relax the strain in the SiGe core, and agglomerated as a few nanometer-sized particles. This structure leads to a large reduction in thermal conductivity due to the GeNP-phonon interaction, while electrical conductivity is sustained because the core of the SiGe alloy NW provides a current path for the charged carriers. The thermal conductivity of the SiGe alloy NWs wrapped with a GeNP-embedded SiO2 shell is 0.41 W m(-1) K(-1) at 300 K. PMID:27306569

  2. Atomic electron motion for Møller polarimetry in a double-arm mode

    CERN Document Server

    Afanasiev, A M; Afanasev, Andrei; Glamazdin, Alexander

    1996-01-01

    We analyse an effect of electron Fermi motion at atomic shells on the accuracy of electron beam polarization measurements with a M\\"oller polarimeter operating in a double--arm mode. It is demonstrated that the effect can result in either {\\it increase} or {\\it decrease} of the measured polarization depending on the detector positions. The effect is simulated for the M\\"oller polarimeter to be installed at CEBAF Hall A.

  3. E(A+M)PEC - An OpenCL Atomic & Molecular Plasma Emission Code For Interstellar Medium Simulations

    CERN Document Server

    de Avillez, Miguel A; Breitschwerdt, Dieter

    2011-01-01

    E(A+M)PEC traces the ionization structure, cooling and emission spectra of plasmas. It is written in OpenCL, runs in NVIDIA Graphics Processor Units and can be coupled to any HD or MHD code to follow the dynamical and thermal evolution of any plasma in, e.g., the interstellar medium (ISM).

  4. 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.

  5. Atomic resolution (0.97 Å) structure of the triple mutant (K53,56,121M) of bovine pancreatic phospholipase A2

    International Nuclear Information System (INIS)

    The crystal structure of a triple mutant (K53,56,121M) of bovine pancreatic phospholipase A2 has been solved at atomic resolution (0.97 Å) and the refined model features the presence of a second calcium ion and a chloride ion. The enzyme phospholipase A2 catalyzes the hydrolysis of the sn-2 acyl chain of phospholipids, forming fatty acids and lysophospholipids. The crystal structure of a triple mutant (K53,56,121M) of bovine pancreatic phospholipase A2 in which the lysine residues at positions 53, 56 and 121 are replaced recombinantly by methionines has been determined at atomic resolution (0.97 Å). The crystal is monoclinic (space group P2), with unit-cell parameters a = 36.934, b = 23.863, c = 65.931 Å, β = 101.47°. The structure was solved by molecular replacement and has been refined to a final R factor of 10.6% (Rfree = 13.4%) using 63 926 unique reflections. The final protein model consists of 123 amino-acid residues, two calcium ions, one chloride ion, 243 water molecules and six 2-methyl-2,4-pentanediol molecules. The surface-loop residues 60–70 are ordered and have clear electron density

  6. Magnetocaloric effect of RM2 (R = rare earth, M = Ni, Al) intermetallic compounds made by centrifugal atomization process for magnetic refrigerator

    International Nuclear Information System (INIS)

    RM2 (R = rare earth, M = Al, Ni and Co) compounds have large entropy change and magnetic transition temperatures can be controlled by change of R and/or M so that are suitable to a magnetic refrigerator for hydrogen liquefaction under development. In order to improve refrigerator performance, spherical powdered HoAl2, DyAl2, and GdNi2 compounds with submillimeter diameter were synthesized by centrifugal atomization process. By measuring the magnetization and heat capacity, we obtained entropy change by magnetic fields and entropy as functions of temperature and magnetic field, which are essential for analysing the magnetic refrigeration cycle. All samples showed sharp magnetic transitions and had good potentials for use in magnetic refrigeration.

  7. Atomic displacements due to interstitial hydrogen in Cu and Pd

    Indian Academy of Sciences (India)

    Hitesh Sharma; S Prakash

    2007-08-01

    The density functional theory (DFT) is used to study the atomic interactions in transition metal-based interstitial alloys. The strain field is calculated in the discrete lattice model using Kanzaki method. The total energy and hence atomic forces between interstitial hydrogen and transition metal hosts are calculated using DFT. The norm-conserving pseudopotentials for H, Cu and Pd are generated self-consistently. The dynamical matrices are evaluated considering interaction up to first nearest neighbors whereas impurity-induced forces are calculated with M32H shell (where M = Cu and Pd). The atomic displacements produced by interstitial hydrogen at the octahedral site in Cu and Pd show displacements of 7.36% and 4.3% of the first nearest neighbors respectively. Both Cu and Pd lattices show lattice expansion due to the presence of hydrogen and the obtained average lattice expansion / = 0.177 for Cu and 0.145 for Pd.

  8. 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.

  9. 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

  10. 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

  11. 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.)

  12. 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

  13. 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 ...

  14. Gyroidal mesoporous multifunctional nanocomposites via atomic layer deposition

    Science.gov (United States)

    Werner, Jörg G.; Scherer, Maik R. J.; Steiner, Ullrich; Wiesner, Ulrich

    2014-07-01

    We demonstrate the preparation of rationally designed, multifunctional, monolithic and periodically ordered mesoporous core-shell nanocomposites with tunable structural characteristics. Three-dimensionally (3D) co-continuous gyroidal mesoporous polymer monoliths are fabricated from a solution-based triblock terpolymer-resol co-assembly and used as the functional templates for the fabrication of free-standing core-shell carbon-titania composites using atomic layer deposition (ALD). The deposition depth into the torturous gyroidal nanonetwork is investigated as a function of ALD conditions and the resulting composites are submitted to different thermal treatments. Results suggest that ALD can homogenously coat mesoporous templates with well defined pore sizes below 50 nm and thicknesses above 10 μm. Structural tunability like titania shell thickness and pore size control is demonstrated. The ordered nanocomposites exhibit triple functionality; a 3D continuous conductive carbon core that is coated with a crystalline titania shell that in turn is in contact with a 3D continuous mesopore network in a compact monolithic architecture. This materials design is of interest for applications including energy conversion and storage. Gyroidal mesoporous titania monoliths can be obtained through simultaneous titania crystallization and template removal in air.We demonstrate the preparation of rationally designed, multifunctional, monolithic and periodically ordered mesoporous core-shell nanocomposites with tunable structural characteristics. Three-dimensionally (3D) co-continuous gyroidal mesoporous polymer monoliths are fabricated from a solution-based triblock terpolymer-resol co-assembly and used as the functional templates for the fabrication of free-standing core-shell carbon-titania composites using atomic layer deposition (ALD). The deposition depth into the torturous gyroidal nanonetwork is investigated as a function of ALD conditions and the resulting composites are

  15. The study of the adductor muscle-shell interface structure in three Mollusc species

    Institute of Scientific and Technical Information of China (English)

    ZHU Yaoyao; SUN Chengjun; SONG Yingfei; JIANG Fenghua; YIN Xiaofei; TANG Min; DING Haibing

    2016-01-01

    The adductor muscle scar (AMS) is the fixation point of adductor muscle to the shell. It is an important organic-inorganic interface and stress distribution area. Despite recent advances, our understanding of the structure and composition of the AMS remain limited. Here, we report study on the AMS of three bivalves:Mytilus coruscus, Chlamys farreri andRuditapes philippinarum. Results showed that there were significant differences among their AMS structures. BothM. coruscus andC. farreri were found to have a columnar layer above the nacreous platelet shell structure at the AMS and this layer was more organized inM. coruscus. There was no distinguishable two-layer structure inR. philippinarum. Atomic force microscopy (AFM) and Fourier transform infrared spectroscopy (FT-IR) results showed that the AMS was much smoother than the nacreous inner shell in all the three species and the AMS had minor different compositions from the nacreous shell layer. SDS-PAGE (sodium dodecyl-sulfate polyacrylamide gel electophoresis) study of the proteins isolated from the interface indicated that there was a 70 kDa protein which seemed to be specifically located to the highly organized columnar AMS structure inMytilus coruscus. Further analysis of this protein showed it contained high level of Asx (Asp+Asn), Glx (Glu+Gln) and Gly. The special structure and composition of the AMS might play important roles in the stability, adhesion and function at this stress distribution site.

  16. Systematic study of structural, electronic, and optical properties of atomic-scale defects in the two-dimensional transition metal dichalcogenides M X2 (M = Mo , W; X = S , Se, Te)

    Science.gov (United States)

    Haldar, Soumyajyoti; Vovusha, Hakkim; Yadav, Manoj Kumar; Eriksson, Olle; Sanyal, Biplab

    2015-12-01

    In this work, we have systematically studied structural, electronic, and magnetic properties of atomic-scale defects in 2D transition metal dichalcogenides M X2 (M = Mo and W; X = S , Se, and Te) by density functional theory. Various types of defects, e.g., X vacancy, X interstitial, M vacancy, M interstitial, and M X and X X double vacancies, have been considered. It has been found that the X interstitial has the lowest formation energy (˜1 eV) for all the systems in the X -rich condition, whereas for the M -rich condition, X vacancy has the lowest formation energy except for M Te2 systems. Both these defects have very high equilibrium defect concentrations at growth temperatures (1000-1200 K) reported in literature. A pair of defects, e.g., two X vacancies or one M and one X vacancies, tend to occupy the nearest possible distance. No trace of magnetism has been found for any one of the defects considered. Apart from X interstitial, all other defects have defect states appearing in the band gap, which can greatly affect the electronic and optical properties of the pristine systems. Our calculated optical properties show that the defect states cause optical transitions at ˜1.0 eV, which can be beneficial for light emitting devices. The results of our systematic study are expected to guide the experimental nanoengineering of defects to achieve suitable properties related to band gap modifications and characterization of defect fingerprints via optical absorption measurements.

  17. 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)

  18. 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.

  19. Mesoporous core–shell Fenton nanocatalyst: a mild, operationally simple approach to the synthesis of adipic acid.

    Science.gov (United States)

    Patra, Astam K; Dutta, Arghya; Bhaumik, Asim

    2013-09-01

    Mesoporous nanoparticles composed of γ-Al2O3 cores and α-Fe2O3 shells were synthesized in aqueous medium. The surface charge of γ-Al2O3 helps to form the core–shell nanocrystals. The core–shell structure and formation mechanism have been investigated by wide-angle XRD, energy-dispersive X-ray spectroscopy, and elemental mapping by ultrahigh-resolution (UHR) TEM and X-ray photoelectron spectroscopy. The N2 adsorption–desorption isotherm of this core–shell materials, which is of type IV, is characteristic of a mesoporous material having a BET surface area of 385 m2 g(−1) and an average pore size of about 3.2 nm. The SEM images revealed that the mesoporosity in this core–shell material is due to self-aggregation of tiny spherical nanocrystals with sizes of about 15–20 nm. Diffuse-reflectance UV/Vis spectra, elemental mapping by UHRTEM, and wide-angle XRD patterns indicate that the materials are composed of aluminum oxide cores and iron oxide shells. These Al2O3@Fe2O3 core–shell nanoparticles act as a heterogeneous Fenton nanocatalyst in the presence of hydrogen peroxide, and show high catalytic efficiency for the one-pot conversion of cyclohexanone to adipic acid in water. The heterogeneous nature of the catalyst was confirmed by a hot filtration test and analysis of the reaction mixture by atomic absorption spectroscopy. The kinetics of the reaction was monitored by gas chromatography and 1H NMR spectroscopy. The new core–shell catalyst remained in a separate solid phase, which could easily be removed from the reaction mixture by simple filtration and the catalyst reused efficiently. PMID:24167824

  20. 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)

  1. Thermally Stable Nanocatalyst for High Temperature Reactions: Pt-Mesoporous Silica Core-Shell Nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Joo, Sang Hoon; Park, J.Y.; Tsung, C.-K.; Yamada, Y.; Yang, P.; Somorjai, G.A.

    2008-10-25

    Recent advances in colloidal synthesis enabled the precise control of size, shape and composition of catalytic metal nanoparticles, allowing their use as model catalysts for systematic investigations of the atomic-scale properties affecting catalytic activity and selectivity. The organic capping agents stabilizing colloidal nanoparticles, however, often limit their application in high-temperature catalytic reactions. Here we report the design of a high-temperature stable model catalytic system that consists of Pt metal core coated with a mesoporous silica shell (Pt{at}mSiO{sub 2}). While inorganic silica shells encaged the Pt cores up to 750 C in air, the mesopores directly accessible to Pt cores made the Pt{at}mSiO{sub 2} nanoparticles as catalytically active as bare Pt metal for ethylene hydrogenation and CO oxidation. The high thermal stability of Pt{at}mSiO{sub 2} nanoparticles permitted high-temperature CO oxidation studies, including ignition behavior, which was not possible for bare Pt nanoparticles because of their deformation or aggregation. The results suggest that the Pt{at}mSiO{sub 2} nanoparticles are excellent nanocatalytic systems for high-temperature catalytic reactions or surface chemical processes, and the design concept employed in the Pt{at}mSiO{sub 2} core-shell catalyst can be extended to other metal-metal oxide compositions.

  2. 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

  3. 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...

  4. 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

  5. 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.

  6. Corrosion behaviour of groundnut shell ash and silicon carbide hybrid reinforced Al-Mg-Si alloy matrix composites in 3.5% NaCl and 0.3M H2SO4 solutions

    Directory of Open Access Journals (Sweden)

    Kenneth Kanayo ALANEME

    2015-05-01

    Full Text Available The corrosion behaviour of Al-Mg-Si alloy based composites reinforced with groundnut shell ash (GSA and silicon carbide (SiC was investigated. The aim is to assess the corrosion properties of Al-Mg-Si alloy based hybrid reinforced composites developed using different mix ratios of GSA (a cheaply processed agro waste derivative which served as partial replacement for SiC and SiC as reinforcing materials. GSA and SiC mixed in weight ratios 0:1, 1:3, 1:1, 3:1, and 1:0 were utilized to prepare 6 and 10 wt% of the reinforcing phase with Al‐Mg‐Si alloy as matrix using two‐step stir casting method. Mass loss and corrosion rate measurement was used to study the corrosion behaviour of the produced composites in 3.5% NaCl and 0.3M H2SO4 solutions. The results show that the Al-Mg-Si alloy based composites containing 6 and 10 wt% GSA and SiC in varied weight ratios were resistant to corrosion in 3.5% NaCl solution. The composites were however more susceptible to corrosion in 0.3M H2SO4 solution (in comparison with the 3.5% NaCl solution. It was noted that the Al-Mg-Si/6 wt% GSA-SiC hybrid composite grades containing GSA and SiC in weight ratio 1:3 and 3:1 respectively exhibited superior corrosion resistance in the 0.3M H2SO4 solution compared to other composites produced for this series. In the case of the Al-Mg-Si/10 wt% GSA-SiC hybrid composite grades, the corrosion resistance was relatively superior for the composites containing a greater weight ratio of GSA (75% and 100% in 0.3M H2SO4 solution.

  7. 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

  8. Trumpeting M Dwarfs with CONCH-SHELL: a Catalog of Nearby Cool Host-Stars for Habitable ExopLanets and Life

    CERN Document Server

    Gaidos, E; Lepine, S; Buccino, A; James, D; Ansdell, M; Petrucci, R; Mauas, P; Hilton, E J

    2014-01-01

    We present an all-sky catalog of 2970 nearby ($d \\lesssim 50$ pc), bright ($J< 9$) M- or late K-type dwarf stars, 86% of which have been confirmed by spectroscopy. This catalog will be useful for searches for Earth-size and possibly Earth-like planets by future space-based transit missions and ground-based infrared Doppler radial velocity surveys. Stars were selected from the SUPERBLINK proper motion catalog according to absolute magnitudes, spectra, or a combination of reduced proper motions and photometric colors. From our spectra we determined gravity-sensitive indices, and identified and removed 0.2% of these as interloping hotter or evolved stars. Thirteen percent of the stars exhibit H-alpha emission, an indication of stellar magnetic activity and possible youth. The mean metallicity is [Fe/H] = -0.07 with a standard deviation of 0.22 dex, similar to nearby solar-type stars. We determined stellar effective temperatures by least-squares fitting of spectra to model predictions calibrated by fits to sta...

  9. IBM symmetries in realistic shell model states

    International Nuclear Information System (INIS)

    An approximate dynamical symmetry referring to IBM-type bosons is shown to be latent in the shell model eigenfunctions for 54Cr and 56Fe. No symmetry is assumed in the approach, which invokes only a realistic shell model interaction and an interpretation of the bosons as nucleon pairs. Particular emphasis is placed on the levels involved in M1 excitation. 25 refs., 4 tabs., 1 fig

  10. 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

  11. Atoms Talking to SQUIDs

    OpenAIRE

    2011-01-01

    We present a scheme to couple trapped $^{87}$Rb atoms to a superconducting flux qubit through a magnetic dipole transition. We plan to trap atoms on the evanescent wave outside an ultrathin fiber to bring the atoms to less than 10 $\\mu$m above the surface of the superconductor. This hybrid setup lends itself to probing sources of decoherence in superconducting qubits. Our current plan has the intermediate goal of coupling the atoms to a superconducting LC resonator.

  12. 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...

  13. 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.)

  14. 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

  15. Cloaking by shells with radially inhomogeneous anisotropic permittivity.

    Science.gov (United States)

    Reshetnyak, V Yu; Pinkevych, I P; Sluckin, T J; Evans, D R

    2016-01-25

    We model electromagnetic cloaking of a spherical or cylindrical nanoparticle enclosed by an optically anisotropic and optically inhomogeneous symmetric shell, by examining its electric response in a quasi-static uniform electric field. When the components of the shell permittivity are radially anisotropic and power-law dependent (ε~rm) whereris distance to the shell center, and m a positive or negative exponent which can be varied), the problem is analytically tractable. Formulas are calculated for the degree of cloaking in the general case, allowing the determination of a dielectric condition for the shells to be used as an invisibility cloak. Ideal cloaking is known to require that homogeneous shells exhibit an infinite ratio of tangential and radial components of the shell permittivity, but for radially inhomogeneous shells ideal cloaking can occur even for finite values of this ratio. PMID:26832575

  16. Optimizing a ultrahigh pressure liquid chromatography-time of flight-mass spectrometry approach using a novel sub-2μm core-shell particle for in depth lipidomic profiling of Caenorhabditis elegans.

    Science.gov (United States)

    Witting, Michael; Maier, Tanja Verena; Garvis, Steve; Schmitt-Kopplin, Philippe

    2014-09-12

    Lipid profiling or lipidomics is currently applied in many different research fields. It refers to the global analysis of a samples lipid content using different analytical chemistry methods, with mass spectrometry as the mostly employed technology. We developed a comprehensive in-depth analysis method for the lipidome of the soil-dwelling nematode Caenorhabitis elegans, a widely used model organism. Four different columns were compared with a generic gradient and a novel sub-2-μm core-shell column, Waters Cortecs C18, showed superior performance in case of chromatographic peak characteristics, e.g. plate numbers and number of detected lipid features. Retention time deviation was generally less than 1% within one column and below 5% for columns from different batches. Intensity variation was lower than 30% for most detected features. Improved chromatographic separation showed enhanced resolution for isomeric lipids and allowed collection of highly detailed MS/MS spectra for lipid identification. In total 1304 lipid features were detected in positive ionization mode and 265 in negative mode. Lipids from different classes were annotated and MS/MS spectra obtained by data dependent fragmentation were used for identification purposes. PMID:25074420

  17. 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)

  18. Effect of Growth Parameters and Substrate Surface Preparation for High-Density Vertical GaAs/GaAsSb Core-Shell Nanowires on Silicon with Photoluminescence Emission at 1.3 μm

    Science.gov (United States)

    Kasanaboina, Pavan Kumar; Ojha, Sai Krishna; Sami, Shifat Us; Lewis Reynolds, C.; Liu, Yang; Iyer, Shanthi

    2016-04-01

    GaAs/GaAsSb nanowire (NW) arrays are ideally suited to meet the demands of the next generation infrared (IR) photodetectors with potential for improving detection. NWs in a core-shell geometry have the advantage of providing axial direction for a long optical path for enhanced optical absorption and a short radial path for charge diffusion and collection. For the Ga-assisted molecular beam epitaxial growth of vertical, dense and uniform GaAs core NWs on Si (111), the effects of substrate surface preparation in combination with growth parameter variation were examined. On the epiready substrate without any surface preparation, both initial Ga shutter opening duration and V/III beam equivalent pressure ratio play a vital role in achieving almost all vertical NWs with moderate density ~107 cm-2. Also the spatial uniformity of the NWs was poor. Substrate surface preparation by chemical cleaning followed by oxidation in air led to highly vertical and uniform NWs with high density (8 × 108 cm-2). The GaAsSb shell was then successfully grown around the highly dense and vertical core GaAs NWs at growth temperatures ranging from 550°C to 590°C. It was found that growth temperature has a strong influence on Sb incorporation in the NWs and, hence, the NW morphology and 4K photoluminescence (PL) spectra. The presence of x-ray diffraction peaks corresponding to (111) reflection only and its higher-order reflections attest to the vertical alignment of NWs. Strain in the NWs as estimated using the Williamson-Hall isotropic strain model increases with Sb incorporation, which results in bending of the NWs with increasing Sb. Structural properties of these NWs using scanning transmission electron microscopy (STEM) are also presented. The temperature dependence PL of the NWs exhibited "S-curve" behavior, which is a well-known signature of localized excitons and a room temperature band edge PL emission occurring at ~1.3 μm.

  19. 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

  20. 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.

  1. Stability of core-shell nanowires in selected model solutions

    Science.gov (United States)

    Kalska-Szostko, B.; Wykowska, U.; Basa, A.; Zambrzycka, E.

    2015-03-01

    This paper presents the studies of stability of magnetic core-shell nanowires prepared by electrochemical deposition from an acidic solution containing iron in the core and modified surface layer. The obtained nanowires were tested according to their durability in distilled water, 0.01 M citric acid, 0.9% NaCl, and commercial white wine (12% alcohol). The proposed solutions were chosen in such a way as to mimic food related environment due to a possible application of nanowires as additives to, for example, packages. After 1, 2 and 3 weeks wetting in the solutions, nanoparticles were tested by Infrared Spectroscopy, Atomic Absorption Spectroscopy, Transmission Electron Microscopy and X-ray diffraction methods.

  2. Shell appraising deepwater discovery off Philippines

    Energy Technology Data Exchange (ETDEWEB)

    Scherer, M. (Shell Philippines Exploration, Manila (Philippines)); Lambers, E.J.T.; Steffens, G.S. (Shell International Petroleum Co. Ltd., London (United Kingdom))

    1993-05-10

    Shell International Petroleum Co. Ltd. negotiated a farmout in 1990 from Occidental International Exploration and Production Co. for Block SC-38 in the South China Sea off Palawan, Philippines, following Oxy's discovery of gas in 1989 in a Miocene Nido limestone buildup. Under the terms of the farmout agreement, Shell became operator with a 50% share. Following the disappointing well North Iloc 1, Shell was successful in finding oil and gas in Malampaya 1. Water 700-1,000 m deep, remoteness, and adverse weather conditions have imposed major challenges for offshore operations. The paper describes the tectonic setting; the Nido limestone play; the Malampaya discovery; and Shell's appraisal studies.

  3. Atomic dynamics with attosecond VUV pulses

    International Nuclear Information System (INIS)

    Full text: Dynamical information on inner-shell processes was hitherto extracted from linewidths in the energy-domain. The recent realization of attosecond pulses with high photon energies now permits a time-based view of the extremely rapid relaxation processes that follow the creation of an atomic core hole. Extension of the pump-probe technique for this purpose requires i) ultrashort well isolated pulses of sufficiently high photon energy, and ii) a method for sampling the time of the emission of an electron with respect to the photoexcitation event. The exciting (pump) VUV pulses are generated as high harmonics of few-cycle (2-3 cycles of 2.5 fs) laser pulses (hv = 1.6 eV) in a neon medium at intensities exceeding 1014 W/cm2. Proper spectral filtering with dedicated multilayer reflectors at the harmonic cut-off results in VUV radiation bursts as short 250. The generated photon energies of about 100 eV are sufficiently energetic for creating vacancies in atoms, e.g. the M-shell of krypton, with the subsequent core-hole relaxation giving rise to emission of Auger electrons. A delayed (probe) laser ld acts as an ultrafast gate by exchanging momentum with the electron at the instant of its ejection, thus modulating the electrons kinetic energy. Analysis of the formed delay-dependent spectral sidebands reveals the evolution of the Auger wave packet. As the technique does not rely on particular transitions, a wide range of electron-emission processes following inner-shell photoexcitation will become accessible to time-resolved studies

  4. On the Highest Oxidation States of Metal Elements in MO4 Molecules (M = Fe, Ru, Os, Hs, Sm, and Pu).

    Science.gov (United States)

    Huang, Wei; Xu, Wen-Hua; Schwarz, W H E; Li, Jun

    2016-05-01

    Metal tetraoxygen molecules (MO4, M = Fe, Ru, Os, Hs, Sm, Pu) of all metal atoms M with eight valence electrons are theoretically studied using density functional and correlated wave function approaches. The heavier d-block elements Ru, Os, Hs are confirmed to form stable tetraoxides of Td symmetry in (1)A1 electronic states with empty metal d(0) valence shell and closed-shell O(2-) ligands, while the 3d-, 4f-, and 5f-elements Fe, Sm, and Pu prefer partial occupation of their valence shells and peroxide or superoxide ligands at lower symmetry structures with various spin couplings. The different geometric and electronic structures and chemical bonding types of the six iso-stoichiometric species are explained in terms of atomic orbital energies and orbital radii. The variations found here contribute to our general understanding of the periodic trends of oxidation states across the periodic table. PMID:27074099

  5. 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

  6. 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

  7. 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...

  8. Internal conversion coefficients for E5 and M5 nuclear transitions, 30< or =Z< or =104

    International Nuclear Information System (INIS)

    Presented here are internal conversion coefficients (ICC) for E5- and M5-multipolarities of nuclear gamma rays for 75 values of atomic number Z in the range 30< or =Z< or =104. The tables provide the missing data for E5 and M5 transitions in the Hager and Seltzer tables. These tables contain M-shell ICC, which those of Sliv and Band do not, and are calculated in a better atomic field (Hartree-Fock-Slater). The calculations are relativistic with finite nuclear size effect taken into account. K-shell ICC for 20 values of the transition energy up to 6 MeV, L-subshell ICC for 25--26 values of the transition energy up to 2 MeV, and M-subshell ICC for 18 values of the transition energy up to approx. =0.2 MeV are given

  9. High-energy collision-induced dissociation of [M+Na]+ ions desorbed by fast atom bombardment of ceramides isolated from the starfish Distolasterias nipon.

    Science.gov (United States)

    Yoo, Ji Sun; Park, Taeseong; Bang, Geul; Lee, Chulhyun; Rho, Jung-Rae; Kim, Young Hwan

    2013-02-01

    Ten ceramides and four cerebrosides were extracted from the starfish Distolasterias nipon by solvent extraction, silica gel column chromatography and reversed-phase high-performance liquid chromatography. Structural identification was conducted using tandem mass spectrometry of monosodiated ions desorbed by fast atom bombardment. The complete structures of four cerebrosides were determined by a previously reported method. The high-energy collision-induced dissociation (CID) spectral characteristics of ceramides with various structures depend on the number and positions of double bonds on both the N-acyl and sphingoid chains, the presence of a hydroxyl group or a double bond at the C-4 position of the sphingoid chain and the presence of an α-hydroxy group on the N-acyl chain. The high-energy CID of the monosodiated ion, [M+Na](+), of each ceramide molecular species generated abundant ions, providing information on the composition of the fatty acyl chains and sphingoid long-chain bases. Each homologous ion series along the fatty acyl group and aliphatic chain of the sphingoid base was used for locating the double-bond positions of both chains and hydroxyl groups on the sphingoid base chain. The double-bond positions were also confirmed by the m/z values of abundant allylic even- and odd-electron ions, and the intensity ratio of the T ion peak relative to the O ion peak. This technique could determine the complete structures of ceramides and cerebrosides in an extract mixture and has great potential for determining other sphingolipids isolated from various biological sources. PMID:23378088

  10. 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.

  11. 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 ...

  12. 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.

  13. Atomic approaches in metastable antiprotonic helium atoms. REPLY to 'analysis of the lifetimes and fractions of antiprotons trapped in metastable antiprotonic-helium states' by I. Shimamura and M. Kimura

    International Nuclear Information System (INIS)

    In the present note the authors clarify the purpose of YO and complement its essential points, thus showing that the criticisms of SK are inappropriate. The paper YO [1] was aimed at discussing some new aspects related to the metastability of hadronic helium atoms which had been discovered when negative kaons [2], negative pions [3] and antiprotons [4] were stopped in liquid helium. The delayed fraction, time spectrum shape and lifetimes were the observables. Further experimental studies are in progress [5], and as of today there is no successful explanation for these interesting phenomena. So, YO tried to give brief and rather qualitative estimates for the observations in an intuitive way, considering only the leading terms. The following problems are discussed in as simple a manner as possible, starting from the exotic-atom viewpoints of Condo [6] and Russell [7]: i)the atomic core polarization effect, ii)the structure and radiative lifetimes, iii)the non-statistical distribution of the angular momentum and an estimate of the delayed fraction, and iv)the isotope effect, though the title represents only i). To respond to the comments of SK, it is important to consider the correspondence between the atomic approach and the molecular approach for the metastable antiprotonic helium atom of Condo-Russell. We therefore begin this note with a discussion of this aspect. (author)

  14. 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...

  15. On the identity of broad-shelled mussels (Mollusca, Bivalvia, Mytilus) from the Dutch delta region

    OpenAIRE

    Groenenberg, D.S.J.; Wesselingh, F.P.; Rajagopal, S.; Jansen, J.M.; Bos, M.M.

    2011-01-01

    Late Quaternary (Eemian) deposits of the Netherlands contain shells that resemble those of living Mytilus galloprovincialis. Similar broad-shelled mytilids also occur in estuaries of the southwestern Netherlands together with slender individuals typical of M. edulis. We sampled living mussels along a depth gradient in the Oosterschelde to a) investigate whether a relation exists between shell shape and depth, b) test if the broad-shelled specimens might represent M. galloprovincialis (or a hy...

  16. 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.

  17. «Auferstehen müssen die Toten». Atomare Apokalypse in Kurt Becsis «Atom vor Christus»

    OpenAIRE

    Emilia Fiandra

    2015-01-01

    The atomic play Atom vor Christus (1952) by the Viennese playwright Kurt Becsi (1920-1988) is one of the very numerous works on the subject of the nuclear threat that appeared in German-speaking countries in the 1950s and ’60s. This article investigates the complex Christian religious discourse that embeds the dramatization of atomic issues and apocalyp­tic ideas of the End in Becsi’s play. Special focus is given to such aspects as the struggle between generations and, in particular, the conf...

  18. 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.

  19. 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

  20. Shell model description of band structure in 48Cr

    International Nuclear Information System (INIS)

    The band structure for normal and abnormal parity bands in 48Cr are described using the m-scheme shell model. In addition to full fp-shell, two particles in the 1d3/2 orbital are allowed in order to describe intruder states. The interaction includes fp-, sd- and mixed matrix elements

  1. 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.

  2. Testing MOND gravity in the shell galaxy NGC 3923

    Science.gov (United States)

    Bílek, M.; Jungwiert, B.; Jílková, L.; Ebrová, I.; Bartošková, K.; Křížek, M.

    2013-11-01

    Context. The elliptical galaxy NGC 3923 is surrounded by numerous stellar shells that are concentric arcs centered on the Galactic core. They are very likely a result of a minor merger and they consist of stars in nearly radial orbits. For a given potential, the shell radii at a given time after the merger can be calculated and compared to observations. The MOdified Newtonian Dynamics (MOND) is a theory that aims to solve the missing mass problem by modifying the laws of classical dynamics in the limit of small accelerations. Hernquist & Quinn (1987, ApJ, 312, 1) claimed that the shell distribution of NGC 3923 contradicted MOND, but Milgrom (1988, ApJ, 332, 86) found several substantial insufficiencies in their work. Aims: We test whether the observed shell distribution in NGC 3923 is consistent with MOND using the current observational knowledge of the shell number and positions and of the host galaxy surface brightness profile, which supersede the data available in the 1980s when the last (and negative) tests of MOND viability were performed on NGC 3923. Methods: Using the 3.6 μm bandpass image of NGC 3923 from the Spitzer space telescope we construct the mass profile of the galaxy. The evolution of shell radii in MOND is then computed using analytical formulae. We use 27 currently observed shells and allow for their multi-generation formation, unlike the Hernquist & Quinn one-generation model that used the 18 shells known at the time. Results: Our model reproduces the observed shell radii with a maximum deviation of ~5% for 25 out of 27 known shells while keeping a reasonable formation scenario. A multi-generation nature of the shell system, resulting from successive passages of the surviving core of the tidally disrupted dwarf galaxy, is one of key ingredients of our scenario supported by the extreme shell radial range. The 25 reproduced shells are interpreted as belonging to three generations.

  3. Controlling core/shell Au/FePt nanoparticle electrocatalysis via changing the core size and shell thickness

    Science.gov (United States)

    Sun, Xiaolian; Li, Dongguo; Guo, Shaojun; Zhu, Wenlei; Sun, Shouheng

    2016-01-01

    Using a modified seed-mediated method, we synthesized core/shell Au/FePt nanoparticles (NPs) with Au sizes of 4, 7, and 9 nm and the FePt shell was controlled to have similar FePt compositions and 0.5, 1, and 2 nm thickness. We studied both core and shell effects on electrochemical and electrocatalytic properties of the Au/FePt NPs, and found that the Au core did change the redox chemistry of the FePt shell and promoted its electrochemical oxidation of methanol. The catalytic activity was dependent on the FePt thicknesses, but not much on the Au core sizes, and the 1 nm FePt shell was found to be the optimal thickness for catalyzing methanol oxidation in 0.1 M HClO4 + 0.1 M methanol, offering not only high activity (1.19 mA cm-2 at 0.5 V vs. Ag/AgCl), but also enhanced stability. Our studies demonstrate a general approach to the design and tuning of shell catalysis in the core/shell structure to achieve optimal catalysis for important electrochemical reactions.Using a modified seed-mediated method, we synthesized core/shell Au/FePt nanoparticles (NPs) with Au sizes of 4, 7, and 9 nm and the FePt shell was controlled to have similar FePt compositions and 0.5, 1, and 2 nm thickness. We studied both core and shell effects on electrochemical and electrocatalytic properties of the Au/FePt NPs, and found that the Au core did change the redox chemistry of the FePt shell and promoted its electrochemical oxidation of methanol. The catalytic activity was dependent on the FePt thicknesses, but not much on the Au core sizes, and the 1 nm FePt shell was found to be the optimal thickness for catalyzing methanol oxidation in 0.1 M HClO4 + 0.1 M methanol, offering not only high activity (1.19 mA cm-2 at 0.5 V vs. Ag/AgCl), but also enhanced stability. Our studies demonstrate a general approach to the design and tuning of shell catalysis in the core/shell structure to achieve optimal catalysis for important electrochemical reactions. Electronic supplementary information (ESI

  4. 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)

  5. Technical aspects of atomic and molecular data processing and exchange, 20. meeting of the A+M Data Centres and ALADDIN Network. Summary report of an IAEA technical meeting

    International Nuclear Information System (INIS)

    The proceedings of the IAEA Advisory Group Meeting on Technical Aspects of Atomic and Molecular Data Processing and Exchange (20th Meeting of A+M Data Centres Network), 7-9 September 2009 at IAEA Headquarters in Vienna, are summarized. The meeting conclusions and recommendations on priorities in A+M data compilation and evaluation and on technical aspects of data processing and exchange are also presented. (author)

  6. IAEA advisory group meeting on 'Technical Aspects of Atomic and Molecular Data Processing and Exchange' (14th meeting of the A + M data centres and ALADDIN network). Summary report

    International Nuclear Information System (INIS)

    The proceedings of the IAEA Advisory Group Meeting on ''Technical Aspects of Atomic and Molecular Data Processing and Exchange (14th Meeting of A + M Data Centres and ALADDIN Network)'', held on July 21-22, 1997 in Vienna, Austria are briefly described. The meeting conclusions and recommendations on the priorities in A + M data compilation and evaluation, and on the technical aspects of data processing and exchange are also presented. The document includes 15 reports from various Data Centres

  7. Technical aspects of atomic and molecular data processing and exchange. 19. meeting of the A+M Data Centres and ALADDIN Network. Summary report of an IAEA technical meeting

    International Nuclear Information System (INIS)

    The proceedings of the IAEA Technical Meeting on Technical Aspects of Atomic and Molecular Data Processing and Exchange (19th Meeting of A+M Data Centres and ALADDIN Network), held on 3-5 October, 2007 in Vienna, Austria, are briefly described. Conclusions and recommendations are presented concerning various proposed projects and their priorities involving A+M data compilation and evaluation and technical aspects of data processing, exchange, and distribution. (author)

  8. IAEA advisory group meeting on technical aspects of atomic and molecular data processing and exchange (15. meeting of the A+M data centres and ALADDIN network). Summary report

    International Nuclear Information System (INIS)

    The proceedings of the IAEA Advisory Group Meeting on 'Technical Aspects of Atomic and Molecular Data Processing and Exchange' (15th Meeting of A+M Data Centres and ALADDIN Network), held on September 13-14, 1999 in Vienna, Austria are briefly described. The meeting conclusions and recommendations on the priorities in A+M data compilation and evaluation, and on the technical aspects of data processing, exchange, and distribution are also presented. (author)

  9. Summary report of IAEA technical meeting on technical aspects of atomic and molecular data processing and exchange - 18th meeting of the A+M Data Centres and ALADDIN Network

    International Nuclear Information System (INIS)

    The IAEA Technical Meeting on 'Technical Aspects of Atomic and Molecular Data Processing and Exchange - 18th Meeting of A+M Data Centres and ALADDIN Network' was held on 10-11 October 2005, in Vienna, Austria. The discussions and presentations focused on the priorities in A+M data compilation and evaluation, and are summarized in this report. Conclusions and recommendations on the technical aspects of data processing, exchange and distribution are also presented. (author)

  10. IAEA advisory group meeting on technical aspects of atomic and molecular data processing and exchange (16. meeting of the A+M Data Centres and ALADDIN network). Summary report

    International Nuclear Information System (INIS)

    The proceedings of the IAEA Advisory group meeting on technical aspects of atomic and molecular data processing and exchange (16. meeting of A+M Data centers and ALADDIN Network), held on September 10-11, 2001 in Vienna, Austria are briefly described. The meeting conclusions and recommendations on the priorities in A+M data compilation and evaluation, and on the technical aspects of data processing, exchange and distribution are also presented. (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. Moving Single Atoms

    Science.gov (United States)

    Stuart, Dustin

    2016-05-01

    Single neutral atoms are promising candidates for qubits, the fundamental unit of quantum information. We have built a set of optical tweezers for trapping and moving single Rubidium atoms. The tweezers are based on a far off-resonant dipole trapping laser focussed to a 1 μm spot with a single aspheric lens. We use a digital micromirror device (DMD) to generate dynamic holograms of the desired arrangement of traps. The DMD has a frame rate of 20 kHz which, when combined with fast algorithms, allows for rapid reconfiguration of the traps. We demonstrate trapping of up to 20 atoms in arbitrary arrangements, and the transport of a single-atom over a distance of 14 μm with continuous laser cooling, and 5 μm without. In the meantime, we are developing high-finesse fibre-tip cavities, which we plan to use to couple pairs of single atoms to form a quantum network.

  13. Conformally Invariant Off-shell Strings

    CERN Document Server

    Myers, R C

    1993-01-01

    Recent advances in non-critical string theory allow a unique continuation of critical Polyakov string amplitudes to off-shell momenta, while preserving conformal invariance. These continuations possess unusual, apparently stringy, characteristics, as we illustrate with our results for three-point functions. (Talk by R.C.M. at Strings '93)

  14. Hydrodynamic experiments on dacryoconarid shell telescoping

    Czech Academy of Sciences Publication Activity Database

    Hladil, Jindřich; Šimčík, Miroslav; Růžička, Marek; Kulaviak, Lukáš; Lisý, Pavel

    2014-01-01

    Roč. 47, č. 3 (2014), s. 376-396. ISSN 0024-1164 R&D Projects: GA ČR GAP210/10/2351 Institutional support: RVO:67985831 ; RVO:67985858 Keywords : dacryoconarid shells * experimental fluid mechanics * narrow cones * Palaeozoic * telescoping Subject RIV: DB - Geology ; Mineralogy; CI - Industrial Chemistry, Chemical Engineering (UCHP-M) Impact factor: 1.454, year: 2014

  15. Has the Crab a radio shell?

    International Nuclear Information System (INIS)

    Comparison of 1.38 and 2.08-cm RATAN-600 observations against Velusamy's (1985) 20-cm VLA map indicates that the spectral index alpha holds constant along drift scans across the entire Crab Nebula source. Measurements of wide dynamic range with the high-sensitivity 7.6-cm RATAN-600 radiometer place a new upper limit on the surface brightness of any circumnebular shell of 10 to the -22nd W/sq m sr Hz on 14-60 arcmin scales, contravening the existence of a radio shell around the Crab. 26 references

  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. Fabricating a Homogeneously Alloyed AuAg Shell on Au Nanorods to Achieve Strong, Stable, and Tunable Surface Plasmon Resonances

    KAUST Repository

    Huang, Jianfeng

    2015-08-13

    Colloidal metal nanocrystals with strong, stable, and tunable localized surface plasmon resonances (SPRs) can be useful in a corrosive environment for many applications including field-enhanced spectroscopies, plasmon-mediated catalysis, etc. Here, a new synthetic strategy is reported that enables the epitaxial growth of a homogeneously alloyed AuAg shell on Au nanorod seeds, circumventing the phase segregation of Au and Ag encountered in conventional synthesis. The resulting core–shell structured bimetallic nanorods (AuNR@AuAg) have well-mixed Au and Ag atoms in their shell without discernible domains. This degree of mixing allows AuNR@AuAg to combine the high stability of Au with the superior plasmonic activity of Ag, thus outperforming seemingly similar nanostructures with monometallic shells (e.g., Ag-coated Au NRs (AuNR@Ag) and Au-coated Au NRs (AuNR@Au)). AuNR@AuAg is comparable to AuNR@Ag in plasmonic activity, but that it is markedly more stable toward oxidative treatment. Specifically, AuNR@AuAg and AuNR@Ag exhibit similarly strong signals in surface-enhanced Raman spectroscopy that are some 30-fold higher than that of AuNR@Au. When incubated with a H2O2 solution (0.5 m), the plasmonic activity of AuNR@Ag immediately and severely decayed, whereas AuNR@AuAg retained its activity intact. Moreover, the longitudinal SPR frequency of AuNR@AuAg can be tuned throughout the red wavelengths (≈620–690 nm) by controlling the thickness of the AuAg alloy shell. The synthetic strategy is versatile to fabricate AuAg alloyed shells on different shaped Au, with prospects for new possibilities in the synthesis and application of plasmonic nanocrystals.

  18. 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

  19. 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

  20. 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

  1. 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.

  2. 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.

  3. 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)

  4. Multi-shelled porous LiNi0.5Mn1.5O4 microspheres as a 5 V cathode material for lithium-ion batteries

    International Nuclear Information System (INIS)

    Multi-shelled porous LiNi0.5Mn1.5O4 microspheres have been successfully synthesized by a co-precipitation approach combined with high-temperature calcinations. The compositions and structures of multi-shelled LiNi0.5Mn1.5O4 microspheres have been investigated by a variety of characterization methods. The LiNi0.5Mn1.5O4 microspheres are composed of a lot of concentric circular porous shells with constant O, Mn, and Ni concentration, which is ascribed to the fast outward diffusion of Mn and Ni atoms and the slow inward diffusion of O and Li atoms during the calcination process. Electrochemical measurements show that LiNi0.5Mn1.5O4 microspheres deliver good cycling stability and rate capability with discharge capacities of 137.1 (0.1 C), 133.9 (0.2 C), 124.2 (0.5 C), 114.9 (1 C), and 96.0 mAh g−1 (2 C). The LiNi0.5Mn1.5O4 microspheres synthesized by the facile method may be a promising cathode candidate for high energy density lithium-ion batteries. - Highlights: • Multi-shelled LiNi0.5Mn1.5O4 microspheres were prepared by a co-precipitation method. • The formation mechanism of multi-shelled LiNi0.5Mn1.5O4 microspheres was illustrated. • Multi-shelled LiNi0.5Mn1.5O4 microspheres exhibited good electrochemical performances

  5. Loading chromium atoms in a magnetic guide

    OpenAIRE

    Greiner, A; Sebastian, J.; Rehme, P.; Aghajani-Talesh, A.; Griesmaier, A.; Pfau, T.

    2007-01-01

    We have realized a magnetic guide for ultracold chromium atoms by continuously loading atoms directly from a Zeeman slower into a horizontal guide. We observe an atomic flux of $2 \\cdot 10^7$ atoms/s and are able to control the mean velocity of the guided atoms between 0 m/s and 3 m/s. We present our experimental results on loading and controlling the mean velocity of the guided atoms and discuss the experimental techniques that are used.

  6. 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.

  7. 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.

  8. 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.

  9. 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...

  10. 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.

  11. 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.

  12. Atomic Dark Matter

    OpenAIRE

    Kaplan, David E.; Krnjaic, Gordan Z.; Rehermann, Keith R.; Wells, Christopher M.

    2009-01-01

    We propose that dark matter is dominantly comprised of atomic bound states. We build a simple model and map the parameter space that results in the early universe formation of hydrogen-like dark atoms. We find that atomic dark matter has interesting implications for cosmology as well as direct detection: Protohalo formation can be suppressed below $M_{proto} \\sim 10^3 - 10^6 M_{\\odot}$ for weak scale dark matter due to Ion-Radiation interactions in the dark sector. Moreover, weak-scale dark a...

  13. Shell matrix proteins of the clam, Mya truncata: Roles beyond shell formation through proteomic study.

    Science.gov (United States)

    Arivalagan, Jaison; Marie, Benjamin; Sleight, Victoria A; Clark, Melody S; Berland, Sophie; Marie, Arul

    2016-06-01

    Mya truncata, a soft shell clam, is presented as a new model to study biomineralization through a proteomics approach. In this study, the shell and mantle tissue were analysed in order to retrieve knowledge about the secretion of shell matrix proteins (SMPs). Out of 67 and 127 shell and mantle proteins respectively, 16 were found in both shell and mantle. Bioinformatic analysis of SMP sequences for domain prediction revealed the presence of several new domains such as fucolectin tachylectin-4 pentraxin-1 (FTP), scavenger receptor, alpha-2-macroglobulin (α2 M), lipocalin and myosin tail along with previously reported SMP domains such as chitinase, carbonic anhydrase, tyrosinase, sushi, and chitin binding. Interestingly, these newly predicted domains are attributed with molecular functions other than biomineralization. These findings suggest that shells may not only act as protective armour from predatory action, but could also actively be related to other functions such as immunity. In this context, the roles of SMPs in biomineralization need to be looked in a new perspective. PMID:27068305

  14. 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....

  15. 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.

  16. 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

  17. 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

  18. N.M.R. study of organo-phosphorus compounds: non equivalence of methylenic protons in the α position of an asymmetric phosphorus atom. Application to study of coupling constants JP,H and JH,H

    International Nuclear Information System (INIS)

    Non-equivalent methylenic protons, with respect to an asymmetric center, have been observed in the n.m.r. spectra of some three- and tetra-coordinated phosphorus compounds. The analysis of these spectra yield the following results: in the studied secondary phosphines, the inversion rate at the phosphorus atom is slow on the n.m.r. time scale; the geminal coupling constant, for a free-rotating methylene group attached to a phosphorus atom, is negative; in phosphines the non equivalence of methylenic protons reveals two 2JP-C-H coupling constants which differ by about 5 Hz. This result is in agreement with previous studies on cyclic phosphines. In phosphine oxides, the 2JP-C-H values are negative. The 3JH-P-C-H coupling constant is positive in both phosphines and phosphine oxides. In phosphines, the non-equivalent methylenic protons exhibit two nearly equal values for this coupling constant. (author)

  19. 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.)

  20. Calculations of effective atomic number

    Energy Technology Data Exchange (ETDEWEB)

    Kaliman, Z. [Department of Physics, Faculty of Arts and Sciences, Omladinska 14, Rijeka (Croatia); Orlic, N. [Department of Physics, Faculty of Arts and Sciences, Omladinska 14, Rijeka (Croatia)], E-mail: norlic@ffri.hr; Jelovica, I. [Department of Physics, Faculty of Arts and Sciences, Omladinska 14, Rijeka (Croatia)

    2007-09-21

    We present and discuss effective atomic number (Z{sub eff}) obtained by different methods of calculations. There is no unique relation between the computed values. This observation led us to the conclusion that any Z{sub eff} is valid only for given process. We illustrate calculations for different subshells of atom Z=72 and for M3 subshell of several other atoms.

  1. Celestial mechanics of planet shells

    Science.gov (United States)

    Barkin, Yu V.; Vilke, V. G.

    2004-06-01

    The motion of a planet consisting of an external shell (mantle) and a core (rigid body), which are connected by a visco-elastic layer and mutually gravitationally interact with each other and with an external celestial body (considered as a material point), is studied (Barkin, 1999, 2002a,b; Vilke, 2004). Relative motions of the core and mantle are studied on the assumption that the centres of mass of the planet and external body move on unperturbed Keplerian orbits around the general centre of mass of the system. The core and mantle of the planet have axial symmetry and have different principal moments of inertia. The differential action of the external body on the core and mantle cause the periodic relative displacements of their centres of mass and their relative turns. An approximate solution of the problem was obtained on the basis of the linearization, averaging and small-parameter methods. The obtained analytical results are applied to the study of the possible relative displacements of the core and mantle of the Earth under the gravitational action of the Moon. For the suggested two-body Earth model and in the simple case of a circular (model) lunar orbit the new phenomenon of periodic translatory-rotary oscillations of the core with a fortnightly period the mantle was observed. The more remarkable phenomenon is the cyclic rotation with the same period (13.7 days) of the core relative to the mantle with a ‘large’ amplitude of 152 m (at the core surface).The results obtained confirm the general concept described by Barkin (1999, 2002a,b) that induced relative shell oscillations can control and dictate the cyclic and secular processes of energization of the planets and satellites in definite rhythms and on different time scales.The results obtained mean that giant moments and forces produce energy which causes in particular deformations of the viscoelastic layer between planet shells. This process is realized with different intensities on different time

  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. Metalloporphyrins with all the pyrrole nitrogens replaced with phosphorus atoms, MP(P)4 (M = Sc, Ti, Fe, Ni, Cu, Zn)

    International Nuclear Information System (INIS)

    Highlights: • First systematic DFT study of the MP(P)4 compounds with increasing number of d-electrons. • Complete substitution of pyrrole nitrogens by P-atoms does not change the ground spin state. • Complete substitution of pyrrole nitrogens by P-atoms results in a bowl-like shape. • Significant stabilization of the MP(P)4 LUMOs compared to the MP counterparts. • MP(P)4 HOMO/LUMO gaps are smaller than the MP HOMO/LUMO gaps. - Abstract: We performed first systematic DFT study of the structures and electronic features (frontier orbitals energies, HOMO/LUMO and optical gaps, IPs and EAs) of the MP(P)4 compounds, with increasing number of d-electrons: 3d14s2 (Sc) → 3d24s2 (Ti) → 3d64s2 (Fe) → 3d84s2 (Ni) → 3d104s1 (Cu) → 3d104s2 (Zn). We performed systematic comparison with the tetrapyrrole MP counterparts. Complete substitution of the pyrrole nitrogens by P-atoms does not change the calculated ground spin state of the compound. All the MP(P)4 species adopt a bowl-like shape, compared to generally planar or slightly distorted shapes of their MP counterparts. Significant positive charge accumulates on P-atoms in MP(P)4. Positive charges on the metals in MP(P)4 are noticeably lower than in the MP counterparts. The calculated MP(P)4 HOMO/LUMO gaps and optical gaps are noticeably smaller than the corresponding gaps in their MP counterparts, which is explained by stabilization of the MP(P)4 LUMOs

  5. Metalloporphyrins with all the pyrrole nitrogens replaced with phosphorus atoms, MP(P){sub 4} (M = Sc, Ti, Fe, Ni, Cu, Zn)

    Energy Technology Data Exchange (ETDEWEB)

    Kuznetsov, Aleksey E., E-mail: aleksey73kuznets@gmail.com

    2015-02-02

    Highlights: • First systematic DFT study of the MP(P){sub 4} compounds with increasing number of d-electrons. • Complete substitution of pyrrole nitrogens by P-atoms does not change the ground spin state. • Complete substitution of pyrrole nitrogens by P-atoms results in a bowl-like shape. • Significant stabilization of the MP(P){sub 4} LUMOs compared to the MP counterparts. • MP(P){sub 4} HOMO/LUMO gaps are smaller than the MP HOMO/LUMO gaps. - Abstract: We performed first systematic DFT study of the structures and electronic features (frontier orbitals energies, HOMO/LUMO and optical gaps, IPs and EAs) of the MP(P){sub 4} compounds, with increasing number of d-electrons: 3d{sup 1}4s{sup 2} (Sc) → 3d{sup 2}4s{sup 2} (Ti) → 3d{sup 6}4s{sup 2} (Fe) → 3d{sup 8}4s{sup 2} (Ni) → 3d{sup 10}4s{sup 1} (Cu) → 3d{sup 10}4s{sup 2} (Zn). We performed systematic comparison with the tetrapyrrole MP counterparts. Complete substitution of the pyrrole nitrogens by P-atoms does not change the calculated ground spin state of the compound. All the MP(P){sub 4} species adopt a bowl-like shape, compared to generally planar or slightly distorted shapes of their MP counterparts. Significant positive charge accumulates on P-atoms in MP(P){sub 4}. Positive charges on the metals in MP(P){sub 4} are noticeably lower than in the MP counterparts. The calculated MP(P){sub 4} HOMO/LUMO gaps and optical gaps are noticeably smaller than the corresponding gaps in their MP counterparts, which is explained by stabilization of the MP(P){sub 4} LUMOs.

  6. Measurement of the parameters of shell targets for laser fusion by means of X-ray Schlieren technique

    International Nuclear Information System (INIS)

    An X-ray Schlieren technique is suggested to be used for control of shell targets designed for experiments on laser fusion which utilizes a two-crystal diffractometer. One-dimensional magnified photographs of shell targets produced by this method demonstrate that shell thicknesses of (>=) 3 μm may be determined with an accuracy of +-0.15 μm

  7. MB82- (M=Be,Mg,Ca,Sr,and Ba):Planar octacoordinate alkaline earth metal atoms enclosed by boron rings

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Complexes involving planar octacoordinate alkaline earth metal atoms in the centers of eight-membered boron rings have been investigated by two density functional theory (DFT) methods.BeB82-with D8h symmetry is predicted to be stable,both geometrically and electronically,since a good match is achieved between the size of the central beryllium atom and the eight-membered boron ring.By contrast,the other alkaline earth metal atoms cannot be stabilized in the center of a planar eight-membered boron ring because of their large radii.By following the out-of-plane imaginary vibrational frequency,pyramidal C8v MgB82-,CaB82-,SrB82-,and BaB82-structures are obtained.The presence of delocalized π and σ valence molecular orbitals in D8h BeB82-gives rise to aromaticity,which is reflected by the value of the nucleus-independent chemical shift.The D8h BeB82-structure is confirmed to be the global minimum on the potential energy surface.

  8. Structural and energetic properties of closed shell XF(n) (X = Cl, Br, and I; n = 1-7) and XO(n)F(m) (X = Cl, Br, and I; n = 1-3; m = 0-6) molecules and ions leading to stability predictions for yet unknown compounds.

    Science.gov (United States)

    Thanthiriwatte, K Sahan; Vasiliu, Monica; Dixon, David A; Christe, Karl O

    2012-10-15

    Atomization energies at 0 K and heats of formation at 0 and 298 K were predicted for the closed shell compounds XF, XF(2)(-), XF(2)(+), XF(3), XF(4)(-), XF(4)(+), XF(5), XF(6)(-), XF(6)(+) (X = Cl and Br) and XO(+), XOF, XOF(2)(-), XOF(2)(+), XOF(3), XOF(4)(-), XOF(4)(+), XOF(5), XOF(6)(-), XO(2)(+), XO(2)F, XO(2)F(2)(-), XO(2)F(2)(+), XO(2)F(3), XO(2)F(4)(-), XO(3)(+), XO(3)F, XO(3)F(2)(-) (X = Cl, Br, and I) using a composite electronic structure approach based on coupled cluster CCSD(T) calculations extrapolated to the complete basis set limit with additional corrections. The calculated heats of formation are in good agreement with the available experimental data. The calculated heats of formation were used to predict fluoride affinities, fluorine cation affinities, and F(2) binding energies. On the basis of our results, BrOF(5) and BrO(2)F(3) are predicted to be stable against spontaneous loss of F(2) and should be able to be synthesized, whereas BrF(7), ClF(7), BrOF(6)(-), and ClOF(6)(-) are unstable by a very wide margin. The stability of ClOF(5) is a borderline case. Although its F(2) loss is predicted to be exothermic by 4.4 kcal/mol, it may have a sufficiently large barrier toward decomposition and be preparable. This situation would resemble ClO(2)F(3) which was successfully synthesized in spite of being unstable toward F(2) loss by 3.3 kcal/mol. On the other hand, the ClOF(4)(+) and BrOF(4)(+) cations are less likely to be preparable with F(2) loss exothermicities of -17.5 and -9.3 kcal/mol, respectively. On the basis of the F(-) affinities of ClOF (45.4 kcal/mol), BrOF (58.7 kcal/mol), and BrO(2)F(3) (65.7 kcal/mol) and their predicted stabilities against loss of F(2), the ClOF(2)(-), BrOF(2)(-), and BrO(2)F(4)(-) anions are excellent targets for synthesis. Our previous failure to prepare the ClO(2)F(4)(-) anion can be rationalized by the predicted high exothermicity of -17.4 kcal/mol for the loss of F(2). PMID:23009656

  9. 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.

  10. Models for Self-Gravitating Photon Shells and Geons

    CERN Document Server

    Andréasson, Håkan; Thaller, Maximilian

    2015-01-01

    We prove existence of spherically symmetric, static, self-gravitating photon shells as solutions to the massless Einstein-Vlasov system. The solutions are highly relativistic in the sense that the ratio $2m(r)/r$ is close to $8/9$, where $m(r)$ is the Hawking mass and $r$ is the area radius. In 1955 Wheeler constructed, by numerical means, so called idealized spherically symmetric geons, i.e. solutions of the Einstein-Maxwell equations for which the energy momentum tensor is spherically symmetric on a time average. The structure of these solutions is such that the electromagnetic field is confined to a thin shell for which the ratio $2m/r$ is close to $8/9$, i.e., the solutions are highly relativistic photon shells. The solutions presented in this work provide an alternative model for photon shells or idealized spherically symmetric geons.

  11. Preparation of hollow shell ICF targets using a depolymerizing model

    International Nuclear Information System (INIS)

    A new technique for producing hollow shell laser fusion capsules was developed that starts with a depolymerizable mandrel. In this technique we use poly(alpha-methylstyrene) (PAMS) beads or shells as mandrels which are overcoated with plasma polymer. The PAMS mandrel is thermally depolymerized to gas phase monomer, which diffuses through the permeable and thermally more stable plasma polymer coating, leaving a hollow shell. We have developed methods for controlling the size of the PAMS mandrel by either grinding to make smaller sizes or melt sintering to form larger mandrels. Sphericity and surface finish are improved by heating the PAMS mandrels in hot water using a surfactant to prevent aggregation. Using this technique we have made shells from 200 μm to 5 mm diameter with 15 to 100 μm wall thickness having sphericity better than 2 μm and surface finish better than 10 nm RMS

  12. 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.

  13. A large metabolic carbon contribution to the δ 13C record in marine aragonitic bivalve shells

    Science.gov (United States)

    Gillikin, David P.; Lorrain, Anne; Meng, Li; Dehairs, Frank

    2007-06-01

    It is well known that the incorporation of isotopically light metabolic carbon (C M) significantly affects the stable carbon isotope (δ 13C) signal recorded in biogenic carbonates. This can obscure the record of δ 13C of seawater dissolved inorganic carbon (δ 13C DIC) potentially archived in the shell carbonate. To assess the C M contribution to Mercenaria mercenaria shells collected in North Carolina, USA, we sampled seawater δ 13C DIC, tissue, hemolymph and shell δ 13C. All shells showed an ontogenic decrease in shell δ 13C, with as much as a 4‰ decrease over the lifespan of the clam. There was no apparent ontogenic change in food source indicated by soft tissue δ 13C values, therefore a change in the respired δ 13C value cannot be the cause of this decrease. Hemolymph δ 13C, on the other hand, did exhibit a negative relationship with shell height indicating that respired CO 2 does influence the δ 13C value of internal fluids and that the amount of respired CO 2 is related to the size or age of the bivalve. The percent metabolic C incorporated into the shell (%C M) was significantly higher (up to 37%, with a range from 5% to 37%) than has been found in other bivalve shells, which usually contain less than 10%C M. Interestingly, the hemolymph did contain less than 10%C M, suggesting that complex fractionation might occur between hemolymph and calcifying fluids. Simple shell biometrics explained nearly 60% of the observed variability in %C M, however, this is not robust enough to predict %C M for fossil shells. Thus, the metabolic effect on shell δ 13C cannot easily be accounted for to allow reliable δ 13C DIC reconstructions. However, there does seem to be a common effect of size, as all sites had indistinguishable slopes between the %C M and shell height (+0.19% per mm of shell height).

  14. Single beam atom sorting machine

    International Nuclear Information System (INIS)

    We create two overlapping one-dimensional optical lattices using a single laser beam, a spatial light modulator and a high numerical aperture lens. These lattices have the potential to trap single atoms, and using the dynamic capabilities of the spatial light modulator may shift and sort atoms to a minimum atom-atom separation of 1.52 μm. We show how a simple feedback circuit can compensate for the spatial light modulator's intensity modulation

  15. Characteristics of cobalt removal by crab shell particles

    International Nuclear Information System (INIS)

    The characteristics of cobalt removal by raw crab shell particles was investigated. The removal efficiency of cobalt was dependent on contact time, solution pH, crab shell dose and ionic strength. Approximately 99% of the cobalt was removed within 6 hour after contact with crab shell particles. The removal efficiency was slightly affected by initial solution pH over 5.0 and the final solution pH changed to 10 spontaneously. In addition, optimum [H range of cobalt removal was broaden by the effect of crab shell addition. Maximum uptake of cobalt was 510 mg Co/g crab shell at initial pH 5.0. The removal efficiency was affected slightly by ionic strength up to 2.0 M of NaCl. From the results of scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS), the removal of cobalt by crab shell was mainly through the dissolution of CaCO3 followed by precipitation of Co(OH)2 and CoCO3 and then the precipitates were adsorbed to the chitin on the surface of crab shell particles. Compared to the results with activated carbon column, the addition of crab shell to activated carbon column increased the removal efficiency dramatically.(author)

  16. 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.)

  17. 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

  18. 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

  19. 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.

  20. High flux source of cold rubidium atoms

    International Nuclear Information System (INIS)

    We report on the production of a continuous, slow, and cold beam of 87Rb atoms with an extremely high flux of 3.2x1012 atoms/s, a transverse temperature of 3 mK, and a longitudinal temperature of 90 mK. We describe the apparatus created to generate the atom beam. Hot atoms are emitted from a rubidium candlestick atomic beam source and transversely cooled and collimated by a 20 cm long atomic collimator section, boosting overall beam flux by a factor of 50. The Rb atomic beam is then decelerated and longitudinally cooled by a 1 m long Zeeman slower

  1. High flux source of cold rubidium atoms

    Science.gov (United States)

    Slowe, Christopher; Vernac, Laurent; Hau, Lene Vestergaard

    2005-10-01

    We report on the production of a continuous, slow, and cold beam of Rb87 atoms with an extremely high flux of 3.2×1012atoms/s, a transverse temperature of 3mK, and a longitudinal temperature of 90mK. We describe the apparatus created to generate the atom beam. Hot atoms are emitted from a rubidium candlestick atomic beam source and transversely cooled and collimated by a 20cm long atomic collimator section, boosting overall beam flux by a factor of 50. The Rb atomic beam is then decelerated and longitudinally cooled by a 1m long Zeeman slower.

  2. 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.

  3. Nanostructued core–shell Sn nanowires @ CNTs with controllable thickness of CNT shells for lithium ion battery

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • Sn nanowires encapsulated in CNTs directly grew on current collectors. • The thickness of CNTs were controlled via growth time, gas flow rate and synthesis temperature. • Thick CNTs contributed to a better capacity retention while thin CNTs led to a higher capacity. • The core–shell structures formed in one-step CVD process. - Abstract: Core–shell structure of Sn nanowires encapsulated in amorphous carbon nanotubes (Sn@CNTs) with controlled thickness of CNT shells was in situ prepared via chemical vapor deposition (CVD) method. The thickness of CNT shells was accurately controlled from 4 to 99 nm by using different growth time, flow rate of hydrocarbon gas (C2H4) and synthesis temperature. The microstructure and composition of the coaxial Sn@CNTs were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and high resolution transmission electron microscopy (HRTEM) techniques. Moreover, the Sn@CNTs were studied as anode materials for Li-ion batteries and showed excellent cycle performance. The capacity was affected by the thickness of outer CNT shells: thick CNT shells contributed to a better retention while thin CNT shells led to a higher capacity. The thin CNT shell of 6 nm presented the highest capacity around 630 mAh g−1

  4. 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...

  5. PRODUCTION OF HIGHER STRENGTH THIN WALLED GLOW DISCHARGE POLYMER SHELLS FOR CRYOGENIC EXPERIMENTS AT OMEGA

    International Nuclear Information System (INIS)

    OAK A271 PRODUCTION OF HIGHER STRENGTH THIN WALLED GLOW DISCHARGE POLYMER SHELLS FOR CRYOGENIC EXPERIMENTS AT OMEGA. Thin walled polymer shells are needed for OMEGA cryogenic laser experiments. These capsules need to be about 900 (micro)m in diameter and as thin as possible (approx 1-2 (micro)m), while having enough strength to be filled with DT as fast as possible to about 1000 atm. The authors have found that by optimizing the coating parameters in the glow discharge polymer (GDP) deposition system, traditionally used for making ICF targets, they can routinely make robust, ∼ 1.5 (micro)m thick, 900 (micro)m diameter GDP shells with buckle strengths of over 0.3 atm. This is twice the strength of shells made prior to the optimization and is comparable to values quoted for polyimide shells. In addition, these shells were found to be approximately three times more permeable and over 20% denser than previously made GDP shells. The combination of higher strength and permeability is ideal for direct drive cryogenic targets at OMEGA. Shells as thin as 0.5 (micro)m have been made. In this paper, the authors discuss the shell fabrication process, effects of modifying various GDP deposition parameters on shell properties and chemical composition

  6. Polarimetry of nacre in iridescent shells

    Science.gov (United States)

    Metzler, R. A.; Burgess, C.; Regan, B.; Spano, S.; Galvez, E. J.

    2014-09-01

    We investigate the light transmitted or reflected from nacre (mother of pearl) taken from the iridescent shell of the bivalve Pinctad a fucata. These nacre surfaces have a rich structure, composed of aragonite crystals arranged as tablets or bricks, 5 μm wide and 400-500 nm thick, surrounded by 30nm thick organic mortar. The light reflected from these shell surfaces, or transmitted through thin polished layers, is rich in its polarization content, exhibiting a space dependent variation in the state of polarization with a high density of polarization singularities. Our goal is to use the polarization information to infer the structure of the biominerals and the role of the organic layer in determining the orientation of the crystals. In the experiments we send the light from a laser with a uniform state of polarization onto the shell, and analyze the light that is either transmitted or reflected, depending on the type of experiment, imaging it after its passage through polarization filters. We use the images from distinct filters to obtain the Stokes parameters, and hence the state of polarization, of each image point. We also construct the Mueller matrix for each imaged point, via 36 measurements. We do this for distinct physical and chemical treatments of the shell sample. Preliminary data shows that the organic layer may be responsible for organizing a multi-crystalline arrangement of aragonite tablets.

  7. 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...

  8. 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.

  9. 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...

  10. 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...

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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. ...

  16. 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)

  17. 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)

  18. 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)

  19. Electron spin resonance dating of shells from the sambaqui (shell mound) Capelinha, Sao Paulo, Brazil

    Energy Technology Data Exchange (ETDEWEB)

    Kinoshita, A. [Sao Paulo Univ., Ribeirao Preto, SP (Brazil). Faculdade de Filosofia, Ciencias e Letras. Dept. de Fisica e Matematica; Universidade do Sagrado Coracao, Bauru, SP (Brazil); Figuty, L. [Sao Paulo Univ., SP (Brazil). Museu de Arqueologia e Etnologia. Setor de Arqueologia; Baffa, O. [Sao Paulo Univ., Ribeirao Preto, SP (Brazil). Faculdade de Filosofia, Ciencias e Letras. Dept. de Fisica e Matematica

    2006-03-15

    Capelinha is a fluvial sambaqui (Brazilian Shell Mound) located in the Ribeira Valley in the State of Sao Paulo that is being studied. It is one of the oldest sambaquis located along a river dated so far in this region. The use of ESR to date other shells stimulated our group to apply this method to the Capelinha site. Shells from land snails (Megalobulimus sp.) obtained in two levels of excavations were analyzed; one of them was in contact with a skeleton that was dated by C-14. The archaeological doses obtained were (8.05{+-}0.07) Gy and (9.50{+-}0.03) Gy. Since the last site was previously dated by C-14 (Beta -Analytics, Beta 153988) giving: 8860 +/- 60 years BP (conventional age) and 10180 to 9710 years BP (calibrated age), the archaeological dose found for this shell was used to determine the local rate of (0.93 to 0.98) mGy/year, that aggress with other surveys done in the region. Using this dose rate the age of the second shell was found to be 8.14 to 8.73 ky BP that agrees with the stratigraphy of the site. (author)

  20. Electron spin resonance dating of shells from the sambaqui (shell mound) Capelinha, Sao Paulo, Brazil

    International Nuclear Information System (INIS)

    Capelinha is a fluvial sambaqui (Brazilian Shell Mound) located in the Ribeira Valley in the State of Sao Paulo that is being studied. It is one of the oldest sambaquis located along a river dated so far in this region. The use of ESR to date other shells stimulated our group to apply this method to the Capelinha site. Shells from land snails (Megalobulimus sp.) obtained in two levels of excavations were analyzed; one of them was in contact with a skeleton that was dated by C-14. The archaeological doses obtained were (8.05±0.07) Gy and (9.50±0.03) Gy. Since the last site was previously dated by C-14 (Beta -Analytics, Beta 153988) giving: 8860 +/- 60 years BP (conventional age) and 10180 to 9710 years BP (calibrated age), the archaeological dose found for this shell was used to determine the local rate of (0.93 to 0.98) mGy/year, that aggress with other surveys done in the region. Using this dose rate the age of the second shell was found to be 8.14 to 8.73 ky BP that agrees with the stratigraphy of the site. (author)

  1. 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

  2. AGM: 16. A+M data Centres and ALADDIN network. Atomic and Molecular Data Unit, Nuclear Data Section. Report of activities: September 1999 - September 2001

    International Nuclear Information System (INIS)

    Dr. Stephens presented a report of activities of the IAEA A+M Data Unit. The activities consisted of data evaluation and recommendation, WWW database developments, AMDIS services, coordinated research programmes, and A+M Data Center Network coordination. Dr. Stephens also presented and demonstrated a new ALADDIN database server

  3. 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.

  4. Extraction of Polyphenols from Cashew Nut Shell

    Directory of Open Access Journals (Sweden)

    Mathew Obichukwu EDOGA

    2006-07-01

    Full Text Available Cashew nut shell liquid (CNSL was extracted from cashew nut shell by indirect leaching process using soxhlet extraction equipment. Normal hexane (n-hexane was used as solvent. The operating conditions for the extraction were 680C and 1 atmosphere in every 100g of cashew nut shell used for the extraction, 35gCNSL was obtained. The CNSL was further separated into cardol, cardanol and anacardic acid (polyphenol using an amine extractant (alanine with the aid of shake-out separation equipment. Subsequently, the polyphenol was further separated into dihydric phenols (resorcinol and monohydric phenol (phenol.The physical separation of the CNSL showed that it consisted of about 10% cardol (dicarboxy- pentadica-dienylbenzene, 50% cardanol and 30% anacardic acid (carbopenta-dica dienylphenol (with the remainder being made up of other substances whose boiling points and specific gravities were 900C and 0.9g/m3 1750C and 1.1g/m3 and 1790C and 1.2g/m3.

  5. On the identity of broad-shelled mussels (mollusca, bivalvia, mytilus) from the Dutch delta region

    OpenAIRE

    Groenenberg, D.S.J.; Wesselingh, F.P.; Rajagopal, S.; Jansen, J.M.; Bos, M.M.; Van De Velde, G; Gittenberger, E; Hoeksema, B.W.; Raad, H.; Hummel, H

    2011-01-01

    Late Quaternary (Eemian) deposits of the Netherlands contain shells that resemble those of living Mytilus galloprovincialis. Similar broad-shelled mytilids also occur in estuaries of the southwestern Netherlands together with slender individuals typical of M. edulis. We sampled living mussels along a depth gradient in the Oosterschelde to a) investigate whether a relation exists between shell shape and depth, b) test if the broadshelled specimens might represent M. galloprovincialis (or a hyb...

  6. 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....

  7. 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

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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...

  13. 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)

  14. 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)

  15. Radiation from collapsing shells, semiclassical backreaction, and black hole formation

    International Nuclear Information System (INIS)

    We provide a detailed analysis of quantum field theory around a collapsing shell and discuss several conceptual issues related to the emission of radiation flux and formation of black holes. Explicit calculations are performed using a model for a collapsing shell, which turns out to be analytically solvable. We use the insights gained in this model to draw reliable conclusions regarding more realistic models. We first show that any shell of mass M, which collapses to a radius close to r=2M, will emit approximately thermal radiation for a period of time. In particular, a shell that collapses from some initial radius to a final radius 2M(1-ε2)-1 (where ε2). Later on (t>>Mln(1/ε2)), the flux from such a shell will decay to zero exponentially. We next study the effect of backreaction computed using the vacuum expectation value of the stress tensor on the collapse. We find that, in any realistic collapse scenario, the backreaction effects do not prevent the formation of the event horizon. The time at which the event horizon is formed is, of course, delayed due to the radiated flux--which decreases the mass of the shell--but this effect is not sufficient to prevent horizon formation. We also clarify several conceptual issues and provide pedagogical details of the calculations in the Appendices to the paper.

  16. 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

  17. 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

  18. Structural and chemical characterization of complex nanomaterials at atomic resolution

    Science.gov (United States)

    Sanchez, Sergio I.

    Catalytic and energetic nanomaterials are analyzed chemically and structurally in atomistic detail. Examination of the prototypical industrial catalyst Pt catalysts supported on gamma-Al2O3 using X-ray absorption spectroscopy (XAS) and scanning transmission electron microscopy (STEM) revealed non-bulk-like behavior. Anomalous, temperature-dependent structural dynamics were characterized in the form of negative thermal expansion (NTE) and abnormal levels of disorder. To examine a less complex system, electrocatalytically-active, core-shell nanostructures assembled from Pt and Pd were synthesized and subsequently examined using spherical aberration-corrected STEM (Cs-STEM) and high-energy X-ray diffraction (XRD). Atomically resolved micrographs provide significant insight into the differences in crystallinity and metal-atom bonding between Pt and Pd. The apparent structural dichotomy between Pt and Pd was extended to studying the differences in nanostructure between other third row fcc transition metals (3M -- Ir, Pt, and Au) and their second row counterparts (2M -- Rh, Pd, and Ag). With the use of Cs-STEM and atomic pair distribution function (PDF) measurements it was determined that the Au, Pt and Ir nanocrystals were more crystalline than their Ag, Pd and Rh analogues and that the 3M series was capable of imparting its crystal structure onto the atoms from the 2M series. Lastly, we looked at highly-reactive Al crystals and their successive passivation by secondary transition metals (Cu, Ni, Ag, Pd, Au and Pt). Rather than affording a uniform, monolayer coverage, C s-STEM, XRD and energy dispersive X-ray spectroscopy revealed unalloyed, particulate deposits of the secondary metal on the Al.

  19. Linear atomic quantum coupler

    CERN Document Server

    El-Orany, Faisal A A

    2009-01-01

    In this paper, we develop the notion of the linear atomic quantum coupler. This device consists of two modes propagating into two waveguides, each of them includes a localized and/or a trapped atom. These waveguides are placed close enough to allow exchanging energy between them via evanescent waves. Each mode interacts with the atom in the same waveguide in the standard way, i.e. as the Jaynes-Cummings model (JCM), and with the atom-mode in the second waveguide via evanescent wave. We present the Hamiltonian for the system and deduce the exact form for the wavefunction. We investigate the atomic inversions and the second-order correlation function. In contrast to the conventional linear coupler, the atomic quantum coupler is able to generate nonclassical effects. The atomic inversions can exhibit long revival-collapse phenomenon as well as subsidiary revivals based on the competition among the switching mechanisms in the system. Finally, under certain conditions, the system can yield the results of the two-m...

  20. Coherent Atom Optics with fast metastable rare gas atoms

    Science.gov (United States)

    Grucker, J.; Baudon, J.; Karam, J.-C.; Perales, F.; Bocvarski, V.; Vassilev, G.; Ducloy, M.

    2006-12-01

    Coherent atom optics experiments making use of an ultra-narrow beam of fast metastable atoms generated by metastability exchange are reported. The transverse coherence of the beam (coherence radius of 1.7 μm for He*, 1.2 μm for Ne*, 0.87 μm for Ar*) is demonstrated via the atomic diffraction by a non-magnetic 2μm-period reflection grating. The combination of the non-scalar van der Waals (vdW) interaction with the Zeeman interaction generated by a static magnetic field gives rise to "vdW-Zeeman" transitions among Zeeman sub-levels. Exo-energetic transitions of this type are observed with Ne*(3P2) atoms traversing a copper micro-slit grating. They can be used as a tunable beam splitter in an inelastic Fresnel bi-prism atom interferometer.

  1. 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)

  2. 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

  3. 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)

  4. 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

  5. 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.

  6. Shell tension forces propel Dictyostelium slugs forward

    International Nuclear Information System (INIS)

    The Dictyostelium slug is an excellent model system for studying collective movements, as it is comprised of about 105 cells all moving together in the same direction. It still remains unclear how this movement occurs and what the physical mechanisms behind it are. By applying our recently developed 3D traction force microscopy, we propose a simple explanation for slug propulsion. Most of the forces are exerted by the sheath surrounding the slug. This secreted shell is under a rather uniform tension (around 50 mN m−1) and will give rise to a tissue under pressure. Finally, we propose that this pressure will naturally push the slug tip forwards if a gradient of shell mechanical properties takes place in the very anterior part of the raised tip. (paper)

  7. Performance Tests of Shell and Plate Type Evaporator for OTEC

    Science.gov (United States)

    Nakaoka, Tsutomu; Uehara, Haruo

    Performance tests on a shell and plate type evaporator (total surface area = 21.95m2, length = 1450mm, width = 235mm, plate number = 100) for ocean thermal energy conversion (OTEC) plants. Freon 22 (R22) and ammonia (NH3) are used as working fluid. The empirical correlations are proporsed in order to predict the boiling heat transfer when using R22 and NH3 and water side heat transfer coefficients for a shell and plate type evaporator. The water side pressure drop is about 3 m at the warm water velocity of 0.7 m/s. The water side friction factor is obtained.

  8. A study of the valence shell electronic structure and photoionisation dynamics of meta-dichlorobenzene and meta-bromochlorobenzene

    International Nuclear Information System (INIS)

    Highlights: ► Electronic structure and photoionisation dynamics of mDCB and mBCB have been studied. ► Dynamics affected by halogen atom Cooper minimum. ► Many-body effects influence inner valence shell ionisation. - Abstract: A combined experimental and theoretical investigation has been performed to study the valence shell electronic structure and photoionisation dynamics of meta-dichlorobenzene and meta-bromochlorobenzene. Angle resolved photoelectron spectra of meta-dichlorobenzene have been recorded using synchrotron radiation in the photon energy range from close to threshold to 100 eV. These have enabled photoelectron anisotropy parameters and branching ratios to be derived. The continuum multiple scattering approach has been employed to calculate photoionisation partial cross-sections and photoelectron angular distributions of the outer valence orbitals of meta-dichlorobenzene. A comparison between the corresponding experimental and theoretical results has demonstrated that ionisation from some of the orbitals is influenced by the Cooper minimum associated with the chlorine atom. Ionisation energies and spectral intensities evaluated with the third-order algebraic diagrammatic construction approximation for the one-particle Green’s function and the outer valence Green’s function approaches have allowed the features observed in the complete valence shell photoelectron spectra of meta-dichlorobenzene and meta-bromochlorobenzene to be interpreted. Many-body phenomena strongly influence ionisation from the inner valence orbitals and lead to the intensity associated with a particular orbital being redistributed amongst numerous satellites. High resolution photoelectron spectra have been recorded with HeI radiation. Vibrational structure has been observed in some of the photoelectron bands and tentative assignments have been proposed

  9. 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

  10. 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.

  11. 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

  12. Manufacturing of glassy thin shell for adaptive optics: results achieved

    Science.gov (United States)

    Poutriquet, F.; Rinchet, A.; Carel, J.-L.; Leplan, H.; Ruch, E.; Geyl, R.; Marque, G.

    2012-07-01

    Glassy thin shells are key components for the development of adaptive optics and are part of future & innovative projects such as ELT. However, manufacturing thin shells is a real challenge. Even though optical requirements for the front face - or optical face - are relaxed compared to conventional passive mirrors, requirements concerning thickness uniformity are difficult to achieve. In addition, process has to be completely re-defined as thin mirror generates new manufacturing issues. In particular, scratches and digs requirement is more difficult as this could weaken the shell, handling is also an important issue due to the fragility of the mirror. Sagem, through REOSC program, has recently manufactured different types of thin shells in the frame of European projects: E-ELT M4 prototypes and VLT Deformable Secondary Mirror (VLT DSM).

  13. Influences of organic matter and calcification rate on trace elements in aragonitic estuarine bivalve shells

    Science.gov (United States)

    Takesue, Renee K.; Bacon, Charles R.; Thompson, Janet K.

    2008-11-01

    A suite of elements (B, Na, Mg, S, K, Ca, V, Mn, Cr, Sr, and Ba) was measured in aragonitic shells of the estuarine bivalve Corbula amurensis, the Asian clam, using the Sensitive High-Resolution Ion MicroProbe with Reverse Geometry (SHRIMP RG). Our initial intent was to explore potential geochemical proxy relationships between shell chemistry and salinity (freshwater inflow) in northern San Francisco Bay (SFB). In the course of this study we observed variations in shell trace element to calcium ([M]/Ca) ratios that could only be attributed to internal biological processes. This paper discusses the nature and sources of internal trace element variability in C. amurensis shells related to the shell organic fraction and shell calcification rates. The average organic content of whole C. amurensis shells is 19%. After treating whole powdered shells with an oxidative cleaning procedure to remove organic matter, shells contained on average 33% less total Mg and 78% less total Mn. Within our analytical uncertainty, Sr and Ba contents were unchanged by the removal of organic matter. These results show that aragonitic C. amurensis shells have a large component of non-lattice-bound Mg and Mn that probably contribute to the dissimilarity of [M]/Ca profiles among five same-sized shells. Non-lattice-bound trace elements could complicate the development and application of geochemical proxy relationships in bivalve shells. Because B, Ba and Sr occur exclusively in shell aragonite, they are good candidates for external proxy relationships. [M]/Ca ratios were significantly different in prismatic and nacreous aragonite and in two valves of the same shell that had different crystal growth rates. Some part of these differences can be attributed to non-lattice-bound trace elements associated with the organic fraction. The differences in [M]/Ca ratios were also consistent with the calcification rate-dependent ion transport model developed by Carré et al. [Carré M., Bentaleb I

  14. Effects of alga polysaccharide capsule shells on in-vivo bioavailability and disintegration

    Institute of Scientific and Technical Information of China (English)

    LI Ting; GUO Shuju; MA Lin; YUAN Yi; HAN Lijun

    2012-01-01

    Gelatin has been used in hard capsule shells for more than a century,and some shortcomings have appeared,such as high moisture content and risk of transmitting diseases of animal origin to people.Based on available studies regarding gelatin and vegetable shells,we developed a new type of algal polysaccharide capsule (APPC) shells.To test whether our products can replace commercial gelatin shells,we measured in-vivo plasma concentration of 12 selected volunteers with a model drug,ibuprofen,using high performance liquid chromatography (HPLC),by calculating the relative bioavailability of APPC and Qualicaps(R) referenced to gelatin capsules and assessing bioequivalence of the three types of shells,and calculated pharmacokinetic parameters with the software DAS 2.0 (China).The results show that APPC shells possess bioequivalence with Qualicaps(R) and gelatin shells.Moreover,the disintegration behavior of four types of shells (APPC,Vegcaps(R),Qualicaps(R) and gelatin shells) with the content of lactose and radioactive element (99mTc) was observed via gamma-scintigraphic images.The bioavailability and gamma-scintigraphic studies showed that APPC was not statistically different from other vegetable and gelatin capsule shells with respect to in-vivo behavior.Hence,it can be concluded that APPCs are exchangeable with other vegetable and gelatin shells.

  15. 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

  16. 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

  17. 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.

  18. 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.

  19. 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.

  20. 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.