WorldWideScience

Sample records for atomic shells k

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

    Indian Academy of Sciences (India)

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

    2004-06-01

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

  2. 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.

  3. Double K-shell photoionization of atomic beryllium

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-11-15

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

  4. 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.

  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. 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)

  7. 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)

  8. 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.

  9. 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

  10. 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.

  11. 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)

  12. 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...

  13. 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.

  14. 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)

  15. 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)

  16. 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.

  17. 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.

  18. 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.

  19. 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

  20. 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

  1. K-shell Photoabsorption of Oxygen Ions

    CERN Document Server

    García, J; Bautista, M A; Gorczyca, T W; Kallman, T R; Palmeri, P

    2004-01-01

    Extensive calculations of the atomic data required for the spectral modelling of the K-shell photoabsorption of oxygen ions have been carried out in a multi-code approach. The present level energies and wavelengths for the highly ionized species (electron occupancies 2 4, lack of measurements, wide experimental scatter, and discrepancies among theoretical values are handicaps in reliable accuracy assessments. The radiative and Auger rates are expected to be accurate to 10% and 20%, respectively, except for transitions involving strongly mixed levels. Radiative and Auger dampings have been taken into account in the calculation of photoabsorption cross sections in the K-threshold region, leading to overlapping lorentzian shaped resonances of constant widths that cause edge smearing. The behavior of the improved opacities in this region has been studied with the XSTAR modelling code using simple constant density slab models, and is displayed for a range of ionization parameters.

  2. 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)

  3. 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

  4. 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.

  5. 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.

  6. 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

  7. K-shell ionization by antiprotons

    International Nuclear Information System (INIS)

    We present first calculations for the impact parameter dependence of K-shell ionization rates in anti pCu and in anti pAg collisions at various projectile energies. We show that the effect of the attractive Coulomb potential on the Rutherford trajectory and the anti-binding effect caused by the negative charge of the antiproton result in a considerable increase of the ionization probability. Total ionization cross-sections for proton and antiproton projectiles are compared with each other and with experimental ionization cross-sections for protons. (orig.)

  8. Observation of $\\pi^- K^+$ and $\\pi^+ K^-$ atoms

    CERN Document Server

    Adeva, B; The PS212 collaboration; Allkofer, Y.; Amsler, C.; Anania, A.; Aogaki, S.; Benelli, A.; Brekhovskikh, V.; Cechak, T.; Chiba, M.; Chliapnikov, P.; Doskarova, P.; Drijard, D.; Dudarev, A.; Dumitriu, D.; Fluerasu, D.; Gorin, A.; Gorchakov, O.; Gritsay, K.; Guaraldo, C.; Gugiu, M.; Hansroul, M.; Hons, Z.; Horikawa, S.; Iwashita, Y.; Karpukhin, V.; Kluson, J.; Kobayashi, M.; Kruglov, V.; Kruglova, L.; Kulikov, A.; Kulish, E.; Kuptsov, A.; Lamberto, A.; Lanaro, A.; Lednicky, R.; Marinas, C.; Martincik, J.; Nikitin, M.; Okada, K.; Olchevskii, V.; Pentia, M.; Penzo, A.; Plo, M.; Prusa, P.; Rappazzo, G.; Vidal, A.Romero; Ryazantsev, A.; Rykalin, V.; Saborido, J.; Sidorov, A.; Smolik, J.; Takeutchi, F.; Tauscher, L.; Trojek, T.; Trusov, S.; Urban, T.; Vrba, T.; Yazkov, V.; Yoshimura, Y.; Zhabitsky, M.; Zrelov, P.

    2016-01-01

    The observation of hydrogen-like $\\pi K$ atoms, consisting of $\\pi^- K^+$ or $\\pi^+ K^-$ mesons, is presented. The atoms have been produced by 24 GeV/$c$ protons from the CERN PS accelerator, interacting with platinum or nickel foil targets. The breakup (ionisation) of $\\pi K$ atoms in the same targets yields characteristic $\\pi K$ pairs, called ``atomic pairs'', with small relative momenta in the pair centre-of-mass system. The upgraded DIRAC experiment has observed $349\\pm62$ such atomic $\\pi K$ pairs, corresponding to a signal of 5.6 standard deviations.

  9. K-shell photoionization of Li-like Ti XX

    Science.gov (United States)

    Liang, Liang; Lu, Xu-yang; Zhou, Chao; Qing, Pang

    2015-04-01

    K-shell photoionization of Li-like Ti XX ions from ground state and first excited state has been studied using the R-matrix method. Through the combination of R-matrix and QB methods, we have not only studied the K-shell photoionization cross section between the first and ninth ionization threshold of Ti XX, but also identified the energy levels of K-shell excited state due to the twelve autoionization Rydberg series.

  10. K-shell photoionization of Li-like Ti XX

    International Nuclear Information System (INIS)

    K-shell photoionization of Li-like highly ionized ions can introduce rich absorption lines that can be used for fusion plasma diagnostics. In this paper K-shell photoionization of Li-like Ti XX ions from the ground state and the first excited state (1s22p 2P) has been studied using the R-matrix method. Through the combination of R-matrix and QB methods, we have not only studied the K-shell photoionization cross section between the first and ninth ionization threshold of Ti XX, but also identified the energy levels of K-shell excited state due to the twelve autoionization Rydberg series

  11. Observation of $\\pi^- K^+$ and $\\pi^+ K^-$ atoms

    OpenAIRE

    DIRAC Collaboration

    2016-01-01

    The observation of hydrogen-like $\\pi K$ atoms, consisting of $\\pi^- K^+$ or $\\pi^+ K^-$ mesons, is presented. The atoms have been produced by 24 GeV/$c$ protons from the CERN PS accelerator, interacting with platinum or nickel foil targets. The breakup (ionisation) of $\\pi K$ atoms in the same targets yields characteristic $\\pi K$ pairs, called "atomic pairs", with small relative momenta in the pair centre-of-mass system. The upgraded DIRAC experiment has observed $349\\pm62$ such atomic $\\pi...

  12. K-SHELL PHOTOABSORPTION OF MAGNESIUM IONS

    Energy Technology Data Exchange (ETDEWEB)

    Hasoğlu, M. F. [Department of Computer Engineering, Hasan Kalyoncu University, 27100 Sahinbey, Gaziantep (Turkey); Abdel-Naby, Sh. A. [Department of Physics, Auburn University, Auburn, AL 36849 (United States); Gatuzz, E.; Mendoza, C. [Centro de Física, Instituto Venezolano de Investigaciones Científicas, Caracas 1020 (Venezuela, Bolivarian Republic of); García, J. [Harvard-Smithsonian Center for Astrophysics, MS-6, 60 Garden Street, Cambridge, MA 02138 (United States); Kallman, T. R. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Gorczyca, T. W. [Department of Physics, Western Michigan University, Kalamazoo, MI 49008-5252 (United States)

    2014-09-01

    X-ray photoabsorption cross sections have been computed for all magnesium ions with three or more electrons using the R-matrix method. A comparison with other available data for Mg II-Mg X shows good qualitative agreement in the resultant resonance shapes. However, for the lower ionization stages, and for singly ionized Mg II in particular, the previous R-matrix results overestimate the K-edge position due to the neglect of important orbital relaxation effects, and a global shift downward in photon energy of those cross sections is therefore warranted. We have found that the cross sections for Mg I and Mg II are further complicated by the M-shell (n = 3) occupancy. As a result, the treatment of spectator Auger decay of 1s → np resonances using a method based on multichannel quantum defect theory and an optical potential becomes problematic, making it necessary to implement an alternative, approximate treatment of Auger decay for neutral Mg I. The new cross sections are used to fit the Mg K edge in XMM-Newton spectra of the low-mass X-ray binary GS 1826-238, where most of the interstellar Mg is found to be in ionized form.

  13. K shell parameters of some lanthanide elements using bremsstrahlung

    International Nuclear Information System (INIS)

    The spectrum of external bremsstrahlung (EB) transmitted through Tb and Ho is measured using a HPGe detector spectrometer. A sudden drop in transmitted intensity at K shell binding energy has been used to determine the K shell photoelectric parameters. The unwanted characteristic K x-ray photons generated just below the K edge has been avoided by carrying out a separate experiment in the same geometry. The measured values of K shell parameters have been compared with FFAST values. - Highlights: • Bremsstrahlung attenuation in Tb and Ho targets is measured. • At K edge a sharp decrease in intensity is used to determine the K shell parameters. • The K x-ray photons appear just below the K edge hinders the precise measurement. • This hindrance is avoided using monochromatic gamma source. • Measured values are compared with those obtained from FFAST tabulations

  14. 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

  15. 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.

  16. 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)

  17. 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

  18. 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)

  19. 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

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

    Science.gov (United States)

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

    2008-04-01

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

  1. Double K-shell ionization probability in 54Mn

    International Nuclear Information System (INIS)

    We have measured the probability of double K-shell vacancy production in the electron capture decay of 54Mn to the 835-keV level of 54Cr. The probability was deduced from the number of triple coincidences among the Cr hypersatellite and satellite x rays emitted in filling the double vacancy and the 835-keV γ ray. The probability of double K-shell vacancy production per K-shell electron capture (PKK) was found to be (2.3-0.5+0.8)x10-4. Comparisons to previous experimental results and theoretical calculations are discussed

  2. Relativistic K shell decay rates and fluorescence yields for Zn, Cd and Hg

    OpenAIRE

    C. Casteleiro; Parente, F.; Indelicato, Paul; P. Marques, J.

    2009-01-01

    In this work we use the multiconfiguration Dirac-Fock method to calculate the transition probabilities for all possible decay channels, radiative and radiationless, of a K shell vacancy in Zn, Cd and Hg atoms. The obtained transition probabilities are then used to calculate the corresponding fluorescence yields which are compared to existing theoretical, semi-empirical and experimental results.

  3. Effects of lowly ionized ions on silicon K-shell absorption spectra

    Science.gov (United States)

    Wei, H. G.; Shi, J. R.; Liang, G. Y.; Wang, F. L.; Zhong, J. Y.; Zhao, G.

    2016-05-01

    Context. In both astrophysical and laboratory plasmas, K-shell absorption spectra have become powerful diagnostic tools to investigate electron density and temperature. These spectra are also widely used to verify the opacity codes in laboratory settings. Aims: We report the effects of the low ionization silicon ions, namely from Si I to Si V, which have rarely been considered in previous models, on the K-shell silicon absorption spectra. Methods: The Si K-shell atomic data were calculated with the flexible atomic code, which is a fully relativistic atomic program with configuration interaction taken into consideration. Detailed level accounting models were employed to calculate the absorption spectra. Results: We calculate the Si absorption spectra in local thermodynamic equilibrium conditions with temperature and density ranges of 20-70 eV and ~1020 cm-3 to ~1022 cm-3, respectively, and show the contributions of the lowly ionized ions to the K-shell absorption spectra of silicon. We also investigate the effects of the different atomic data on the absorption spectra. We find good agreement between our results and these from OPLIB. Conclusions: We find that the contributions from these lowly ionized ions cannot be neglected at relative low temperatures. Accurate experimental measurements are needed to benchmark the theoretical calculations.

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

    Science.gov (United States)

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

    2015-08-01

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

  5. 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.

  6. Calculation of K-shell fluorescence yields for low-Z elements

    International Nuclear Information System (INIS)

    The analytical methods based on X-ray fluorescence are advantageous for practical applications in a variety of fields including atomic physics, X-ray fluorescence surface chemical analysis and medical research and so the accurate fluorescence yields (ωK) are required for these applications. In this contribution we report a new parameters for calculation of K-shell fluorescence yields (ωK) of elements in the range of 11≤Z≤30. The experimental data are interpolated by using the famous analytical function (ωk/(1−ωk))1/q (were q=3, 3.5 and 4) vs Z to deduce the empirical K-shell fluorescence yields. A comparison is made between the results of the procedures followed here and those theoretical and other semi-empirical fluorescence yield values. Reasonable agreement was typically obtained between our result and other works

  7. Calculation of K-shell fluorescence yields for low-Z elements

    Energy Technology Data Exchange (ETDEWEB)

    Nekkab, M., E-mail: mohammed-nekkab@yahoo.com [Physics Department, Faculty of Sciences, University of Mohamed Boudiaf, 28000 M’Sila (Algeria); LESIMS laboratory, Physics Department, Faculty of Sciences, University of Setif 1, 19000 Setif (Algeria); Kahoul, A. [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, University of Mohamed Boudiaf, 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, N. Küp [Department of Metallurgical and Materials Engineering, Faculty of Technology, Mustafa Kemal University, Hatay 31040 (Turkey); Aylikçi, V. [Department of Energy Systems Engineering, Faculty of Technology, Mustafa Kemal University, 31040 Hatay (Turkey)

    2015-03-30

    The analytical methods based on X-ray fluorescence are advantageous for practical applications in a variety of fields including atomic physics, X-ray fluorescence surface chemical analysis and medical research and so the accurate fluorescence yields (ω{sub K}) are required for these applications. In this contribution we report a new parameters for calculation of K-shell fluorescence yields (ω{sub K}) of elements in the range of 11≤Z≤30. The experimental data are interpolated by using the famous analytical function (ω{sub k}/(1−ω{sub k})){sup 1/q} (were q=3, 3.5 and 4) vs Z to deduce the empirical K-shell fluorescence yields. A comparison is made between the results of the procedures followed here and those theoretical and other semi-empirical fluorescence yield values. Reasonable agreement was typically obtained between our result and other works.

  8. K-shell processes in heavy-ion collisions in solids and the local plasma approximation

    Science.gov (United States)

    Kadhane, Umesh; Montanari, C. C.; Tribedi, Lokesh C.

    2003-03-01

    We have investigated K-shell vacancy production due to ionization and electron transfer processes, in collisions of highly charged oxygen ions with various solid targets such as Cl, K, Ti, Fe, and Cu at energies between 1.5 and 6.0 MeV/u. The K-shell ionization cross sections were derived from the measured K x-ray cross sections. An ab initio theoretical model based on the local plasma approximation (LPA), which is an extension of the dielectric formalism to consider core electrons, provides an explanation of the measured data only qualitatively. In case of asymmetric collisions (Zp/Ztion-atom collisions agree quite well with the data for different combinations of target and projectile elements. In addition, we have also measured the K(target)-K(projectile) electron transfer cross sections and compared them with a model based on perturbed-stationary-state approximation.

  9. Molecular single photon double K-shell ionization

    Energy Technology Data Exchange (ETDEWEB)

    Penent, F., E-mail: francis.penent@upmc.fr [UPMC, Université Paris 06, LCPMR, 11 rue P. et M. Curie, 75231 Paris Cedex 05 (France); CNRS, LCPMR (UMR 7614), 11 rue P. et M. Curie, 75231 Paris Cedex 05 (France); Nakano, M. [Photon Factory, Institute of Materials Structure Science, Oho, Tsukuba 305-0801 (Japan); Department of Chemistry, Tokyo Institute of Technology, O-okayama, Tokyo 152-8551 (Japan); Tashiro, M. [Institute for Molecular Science, Okazaki 444-8585 (Japan); Grozdanov, T.P. [Institute of Physics, University of Belgrade, Pregrevica 118, 11080 Belgrade (Serbia); Žitnik, M. [Jožef Stefan Institute, P.O. Box 3000, SI-1001 Ljubljana (Slovenia); Carniato, S.; Selles, P.; Andric, L.; Lablanquie, P.; Palaudoux, J. [UPMC, Université Paris 06, LCPMR, 11 rue P. et M. Curie, 75231 Paris Cedex 05 (France); CNRS, LCPMR (UMR 7614), 11 rue P. et M. Curie, 75231 Paris Cedex 05 (France); Shigemasa, E.; Iwayama, H. [Institute for Molecular Science, Okazaki 444-8585 (Japan); Hikosaka, Y.; Soejima, K. [Department of Environmental Science, Niigata University, Niigata 950-2181 (Japan); Suzuki, I.H. [Photon Factory, Institute of Materials Structure Science, Oho, Tsukuba 305-0801 (Japan); Kouchi, N. [Department of Chemistry, Tokyo Institute of Technology, O-okayama, Tokyo 152-8551 (Japan); Ito, K. [Photon Factory, Institute of Materials Structure Science, Oho, Tsukuba 305-0801 (Japan)

    2014-10-15

    We have studied single photon double K-shell ionization of small molecules (N{sub 2}, CO, C{sub 2}H{sub 2n} (n = 1–3), …) and the Auger decay of the resulting double core hole (DCH) molecular ions thanks to multi-electron coincidence spectroscopy using a magnetic bottle time-of-flight spectrometer. The relative cross-sections for single-site (K{sup −2}) and two-site (K{sup −1}K{sup −1}) double K-shell ionization with respect to single K-shell (K{sup −1}) ionization have been measured that gives important information on the mechanisms of single photon double ionization. The spectroscopy of two-site (K{sup −1}K{sup −1}) DCH states in the C{sub 2}H{sub 2n} (n = 1–3) series shows important chemical shifts due to a strong dependence on the C-C bond length. In addition, the complete cascade Auger decay following single site (K{sup −2}) ionization has been obtained.

  10. 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.

  11. 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.

  12. 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)

  13. Multiphoton inner-shell ionization of the carbon atom

    OpenAIRE

    Rey, H. F.; Hart, H W

    2015-01-01

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

  14. 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

  15. Contrasts in the application of distortion in calculations of the K-shell ionization cross section

    International Nuclear Information System (INIS)

    Two models which describe the proton-induced ionization from the K shell of an atom are contrasted in terms of the differing forms of distortion employed. Results of calculations of both total and differential cross section are seen to be surprisingly close despite the large disparity between the models. Some consequences are discussed, particularly with regard to the use of pseudostates to represent continuum states. (orig.)

  16. High-Resolution Spectroscopy of K-shell Praseodymium with a High-Energy Calorimeter

    Energy Technology Data Exchange (ETDEWEB)

    Thorn, D B; Brown, G V; Clementson, J T; Chen, H; Chen, M H; Beiersdorfer, P; Boyce, K R; Kilbourne, C A; Porter, F S; Kelley, R L

    2007-06-05

    We present a measurement of the K-shell spectrum of He-like through Be-like praseodymium ions trapped in the Livermore SuperEBIT electron beam ion trap using a bismuth absorber pixel on the XRS/EBIT microcalorimeter. This measurement is the first of its kind where the n=2 to n=1 transitions of the various charge states are spectroscopically resolved. The measured transition energies are compared with theoretical calculations from several atomic codes.

  17. 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.

  18. Laboratory Measurement and Theoretical Modeling of K-shell X-ray Lines from Inner-shell Excited and Ionized Ions of Oxygen

    Energy Technology Data Exchange (ETDEWEB)

    Gu, M; Schmidt, M; Beiersdorfer, P; Chen, H; Thorn, D B; Tr?bert, E; Behar, E; Kahn, S M

    2005-02-05

    We present high resolution laboratory spectra of K-shell X-ray lines from inner-shell excited and ionized ions of oxygen, obtained with a reflection grating spectrometer on the electron beam ion trap (EBIT-I) at the Lawrence Livermore National Laboratory. Only with a multi-ion model including all major atomic collisional and radiative processes, are we able to identify the observed K-shell transitions of oxygen ions from O III to O VI. The wavelengths and associated errors for some of the strongest transitions are given, taking into account both the experimental and modeling uncertainties. The present data should be useful in identifying the absorption features present in astrophysical sources, such as active galactic nuclei and X-ray binaries. They are also useful in providing benchmarks for the testing of theoretical atomic structure calculations.

  19. Copper fine-structure K-shell electron impact ionization cross sections for fast-electron diagnostic in laser-solid experiments

    International Nuclear Information System (INIS)

    The K-shell electron impact ionization (EII) cross section, along with the K-shell fluorescence yield, is one of the key atomic parameters for fast-electron diagnostic in laser-solid experiments through the K-shell emission cross section. In addition, copper is a material that has been often used in those experiments because it has a maximum total K-shell emission yield. Furthermore, in a campaign dedicated to the modeling of the K lines of astrophysical interest (Palmeri et al., 2012), the K-shell fluorescence yields for the K-vacancy fine-structure atomic levels of all the copper isonuclear ions have been calculated. In this study, the K-shell EII cross sections connecting the ground and the metastable levels of the parent copper ions to the daughter ions K-vacancy levels considered in Palmeri et al. (2012) have been determined. The relativistic distorted-wave (DW) approximation implemented in the FAC atomic code has been used for the incident electron kinetic energies up to 10 times the K-shell threshold energies. Moreover, the resulting DW cross sections have been extrapolated at higher energies using the asymptotic form proposed by Davies et al. (2013)

  20. Electronic factors for K-shell-electron conversion probability and electron-positron pair formation probability in electric monopole transitions

    International Nuclear Information System (INIS)

    This paper presents, in tabular form, the electronic factors ΩK,π(Z,k) of the electric monopole transition probability associated with the internal conversion of an electron from the atomic K shell (IC;K) and with the internal pair formation(IPF;π). The Ωπ values are calculated by taking the nuclear Coulomb effects into account. The corrections to ΩK due to finite nuclear size and bound-state atomic screening are not included in the present calculations. The calculated ratio of the K-shell-electron conversion probability to the electron-positron pair formation probability is found to be in good agreement with the available experimental data for Z-<40

  1. Measurement of K Shell Photoelectric Cross Sections at a K Edge--A Laboratory Experiment

    Science.gov (United States)

    Nayak, S. V.; Badiger, N. M.

    2007-01-01

    We describe in this paper a new method for measuring the K shell photoelectric cross sections of high-Z elemental targets at a K absorption edge. In this method the external bremsstrahlung (EB) photons produced in the Ni target foil by beta particles from a weak[superscript 90]Sr-[superscript 90]Y beta source are passed through an elemental target…

  2. 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.

  3. 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.

  4. 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

  5. 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

  6. K-shell fluorescence yields of barium and lanthanum

    International Nuclear Information System (INIS)

    K-shell fluorescence yields for barium and lanthanum have been measured adopting simple 2π geometrical configuration and employing a weak 57Co radioactive source. A scintillation spectrometer with an NaI(Tl) detector of dimensions 44.5 mm diameterx50 mm thickness was employed for the detection and measurement of radiation. The results obtained are in good agreement with the best-fitted values of and also with the other experimental values, indicating that our simple method can be extended to determine fluorescence parameters of high Z materials.

  7. Vanadium fine-structure K-shell electron impact ionization cross sections for fast-electron diagnostic in laser–solid experiments

    International Nuclear Information System (INIS)

    The K-shell electron impact ionization (EII) cross section, along with the K-shell fluorescence yield, is one of the key atomic parameters for fast-electron diagnostic in laser–solid experiments through the K-shell emission cross section. In addition, in a campaign dedicated to the modeling of the K lines of astrophysical interest (Palmeri et al. (2012)), the K-shell fluorescence yields for the K-vacancy fine-structure atomic levels of all the vanadium isonuclear ions have been calculated. In this study, the K-shell EII cross sections connecting the ground and the metastable levels of the parent vanadium ions to the daughter ions K-vacancy levels considered in Palmeri et al. (2012) have been determined. The relativistic distorted-wave (DW) approximation implemented in the FAC atomic code has been used for the incident electron kinetic energies up to 20 times the K-shell threshold energies. Moreover, the resulting DW cross sections have been extrapolated at higher energies using the asymptotic behavior of the modified relativistic binary encounter Bethe model (MRBEB) of Guerra et al. (2012) with the density-effect correction proposed by Davies et al. (2013)

  8. Vanadium fine-structure K-shell electron impact ionization cross sections for fast-electron diagnostic in laser–solid experiments

    Energy Technology Data Exchange (ETDEWEB)

    Palmeri, P., E-mail: patrick.palmeri@umons.ac.be [Astrophysique et Spectroscopie, Université de Mons - UMONS, B-7000 Mons (Belgium); Quinet, P., E-mail: pascal.quinet@umons.ac.be [Astrophysique et Spectroscopie, Université de Mons - UMONS, B-7000 Mons (Belgium); IPNAS, Université de Liège, B-4000 Liège (Belgium); Batani, D., E-mail: batani@celia.u-bordeaux1.fr [CELIA, Université de Bordeaux, F-33400 Talence (France)

    2015-09-15

    The K-shell electron impact ionization (EII) cross section, along with the K-shell fluorescence yield, is one of the key atomic parameters for fast-electron diagnostic in laser–solid experiments through the K-shell emission cross section. In addition, in a campaign dedicated to the modeling of the K lines of astrophysical interest (Palmeri et al. (2012)), the K-shell fluorescence yields for the K-vacancy fine-structure atomic levels of all the vanadium isonuclear ions have been calculated. In this study, the K-shell EII cross sections connecting the ground and the metastable levels of the parent vanadium ions to the daughter ions K-vacancy levels considered in Palmeri et al. (2012) have been determined. The relativistic distorted-wave (DW) approximation implemented in the FAC atomic code has been used for the incident electron kinetic energies up to 20 times the K-shell threshold energies. Moreover, the resulting DW cross sections have been extrapolated at higher energies using the asymptotic behavior of the modified relativistic binary encounter Bethe model (MRBEB) of Guerra et al. (2012) with the density-effect correction proposed by Davies et al. (2013)

  9. 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.)

  10. Empirical K-shell ionization cross-sections of elements from 4Be to 92U by proton impact

    International Nuclear Information System (INIS)

    A large database containing about 5400 experimental K-shell ionization cross-sections by protons for elements from Be to U is collected from various sources and compilations available in the literature from 1953 to 1999. The data are divided into groups corresponding to their atomic numbers and fitted separately by analytical functions to deduce empirical K-shell ionization cross-sections. The deduced empirical K-shell ionization cross-sections are presented together with the reference ones obtained by Paul and Sacher for selected elements [H. Paul, J. Sacher, At. Data Nucl. Data Tables 42 (1989) 105]. The two sets of results are compared to the calculations within the ECPSSR theory and discussed.

  11. 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)

  12. K-shell ionization under zone axis electron diffraction conditions

    International Nuclear Information System (INIS)

    A comprehensive theoretical treatment for the inelastic scattering of fast electrons in a crystalline environment is applied to account for variations in characteristic x-ray emission rates from spinel and chromia under zone axis diffraction conditions for 300 keV electrons. X-ray counts as well as backscattered electron contrast are recorded as the beam is tilted by about 70 mrad on a two-dimensional scan raster. Calculated K-shell ionization and backscattering cross sections, based on a model which takes into account interaction delocalization, thermal diffuse scattering and the consequent thickness dependent channelling effects in a realistic way, are in good agreement with experiment. 43 refs., 13 figs

  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. 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)

  15. 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 .

  16. Evidence for $\\pi K$-atoms with DIRAC

    CERN Document Server

    Adeva, B; Allkofer, Y; Amsler, C; Anania, A; Benelli, A; Brekhovskikh, V; Caragheorgheopol, G; Cechak, T; Chiba, M; Chliapnikov, P; Ciocarlan, C; Constantinescu, S; Curceanu, C; Detraz, C; Dreossi, D; Drijard, D; Dudarev, A; Duma, M; Dumitriu, D; Fungueiriño, J L; Gerndt, J; Gorin, A; Gorchakov, O; Gritsay, K; Guaraldo, C; Gugiu, M; Hansroul, M; Hons, Z; Horikawa, S; Iliescu, M; Karpukhin, V; Kluson, J; Kobayashi, M; Komarov, V; Kruglov, V; Kruglova, L; Kulikov, A; Kuptsov, A; Kurochkin, I; Lamberto, A; Lanaro, A; Lapshin, V; Lednicky, R; Levi Sandri, P; Lopez Aguera, A; Lucherinie, V; Manuilov, I; Mariñas, C; Nemenov, L; Nikitin, M; Okada, K; Olchevskii, V; Pentia, M; Penzo, A; Pló, M; Rappazzo, G F; Regenfus, C; Rochet, J; Romero, A; Ronjin, V; Ryazantsev, A; Rykalin, V; Saborido, J; Schacher, J; Sidorov, A; Smolik, J; Sugimoto, S; Takeutchi, F; Tarasov, A; Tauscher, L; Trojek, T; Trusov, S; Utkin, V; Vázquez Doce, o, O; Vrba, T; Yazkov, V; Yoshimura, Y; Zhabitsky, M

    2009-01-01

    We present evidence for the first observation of electromagnetically bound $\\pi^\\pm K^\\mp$-pairs ($\\pi K$-atoms) with the DIRAC experiment at the CERN-PS. The $\\pi K$-atoms are produced by the 24 GeV/c proton beam in a thin Pt-target and the $\\pi^\\pm$ and $K^\\mp$-mesons from the atom dissociation are analyzed in a two-arm magnetic spectrometer. The observed enhancement at low relative momentum corresponds to the production of 173 $\\pm$ 54 $\\pi K$-atoms. The mean life of $\\pi K$-atoms is related to the s-wave $\\pi K$-scattering lengths, the measurement of which is the goal of the experiment. From these first data we derive a lower limit for the mean life of 0.8 fs at 90% confidence level.

  17. Evidence for {pi}K-atoms with DIRAC

    Energy Technology Data Exchange (ETDEWEB)

    Adeva, B. [IGFAE, Santiago de Compostela University (Spain); Afanasyev, L. [JINR Dubna (Russian Federation); Allkofer, Y. [Physik-Institut der Universitaet Zuerich (Switzerland); Amsler, C. [Physik-Institut der Universitaet Zuerich (Switzerland)], E-mail: claude.amsler@cern.ch; Anania, A. [INFN, Messina University, Messina (Italy); Benelli, A. [Physik-Institut der Universitaet Zuerich (Switzerland); Brekhovskikh, V. [IHEP Protvino (Russian Federation); Caragheorgheopol, G. [IFIN-HH, National Institute for Physics and Nuclear Engineering, Bucharest (Romania); Cechak, T. [Czech Technical University, Prague (Czech Republic); Chiba, M. [Tokyo Metropolitan University (Japan); Chliapnikov, P. [IHEP Protvino (Russian Federation); Ciocarlan, C.; Constantinescu, S. [IFIN-HH, National Institute for Physics and Nuclear Engineering, Bucharest (Romania); Curceanu, C. [INFN, Laboratori Nazionali di Frascati, Frascati (Italy); Detraz, C. [CERN, Geneva (Switzerland); Dreossi, D. [INFN, Trieste University, Trieste (Italy); Drijard, D. [CERN, Geneva (Switzerland); Dudarev, A. [JINR Dubna (Russian Federation); Duma, M.; Dumitriu, D. [IFIN-HH, National Institute for Physics and Nuclear Engineering, Bucharest (Romania)] (and others)

    2009-04-06

    We present evidence for the first observation of electromagnetically bound {pi}{sup {+-}}K{sup {+-}}-pairs ({pi}K-atoms) with the DIRAC experiment at the CERN-PS. The {pi}K-atoms are produced by the 24 GeV/c proton beam in a thin Pt-target and the {pi}{sup {+-}} and K{sup {+-}}-mesons from the atom dissociation are analyzed in a two-arm magnetic spectrometer. The observed enhancement at low relative momentum corresponds to the production of 173{+-}54{pi}K-atoms. The mean life of {pi}K-atoms is related to the s-wave {pi}K-scattering lengths, the measurement of which is the goal of the experiment. From these first data we derive a lower limit for the mean life of 0.8 fs at 90% confidence level.

  18. Theoretical ionization cross-sections in the K-shell - Hydrogenic model and beyond

    International Nuclear Information System (INIS)

    The K-shell ionization cross-sections are studied in a semiclassical model that takes into account the projectile kinematics in the field of nucleus and atomic electrons, and considers the time evolution of the wave functions within a simplified coupled-channel approach. The wave functions are Dirac hydrogenic, though a correction of using the Hartree-Fock field is proposed. The calculation is non-hydrogenic in the estimate of the continuum-continuum interaction. A comparison with the experiment was performed for the elements that exhibit a large number of measured points, and for the reference data. With respect to the united atom semiclassical model, the present calculation provides a more realistic description of the binding effect and agrees better with the experimental data in lighter atoms. As for the ECPSSR theory, general validity of this method in light and medium atoms was confirmed, though the present model, on account of precise projectile kinematics, reproduces better the adiabatic region of heavy elements

  19. New analytical relativistic formulae for the total photoeffect cross section for the K-shell electrons

    International Nuclear Information System (INIS)

    Full text: We present a new analytical relativistic result for the total photoeffect cross section for the K-shell electrons, in the lowest order of perturbation theory. In the cases of low atomic number values, the well known Sauters formula is recovered as a rough approximation of the exact relativistic result. For high atomic numbers, due to the specific behavior at small distances from the nucleus of the ground state Dirac spinor, some subtle relativistic effects are revealed near the photoeffect threshold. Also, our formulae contain all terms contributing at high energies in the next order of the perturbation theory, obtaining in the limit of infinite photon energy the correction term due to Pratt and Gavrila. In the nonrelativistic limit, we get the right result involving all the multipoles and retardation terms without the spurious singularities presented by Fischer's formula. Numerical evaluations of these formulae give very good predictions, within 5 % for photon energies up to 5 MeV, comparing with accurate relativistic calculations existing in the literature. Using the Green function method we obtain the imaginary part of the forward elastic scattering amplitude which provides via the optical theorem the photoeffect cross section and also the pair production cross section with the electron created in the K shell. Our formalism allows including the screening effects which may be important near the photoeffect threshold, by using an effective nuclear charge Zeff depending on the photon energy ω. Taking into account the screening effects, the obtained photoeffect cross sections present an even better agreement with the experimental cross sections and other relativistic calculations in the region near the threshold. We point out that cross section for the K-shell electrons provides, in the high energy regime, the most important contribution to the total cross section of the whole atom. Thus, our formulae are useful for an important range of the gamma

  20. K-shell ionization in the positron decay of 65Zn

    International Nuclear Information System (INIS)

    The probability for K-shell ionization in the positron decay of 65Zn, P/sub K/(#betta#+) has been studied by recording coincidences between the annihilation radiation produced subsequent to the positron decay and the Cu K x rays produced when the K-shell vacancy is filled. This probability was found to be (16.1 +- 3.0) x 10-4, which is approximately three times larger than recent theoretical predictions of Law and Suzuki

  1. Double K-shell vacancy production in the electron capture decay of 139Ce

    International Nuclear Information System (INIS)

    The probability of double K-shell vacancy production in the electron capture decay of 139Ce to the 166-keV level of 139La has been investigated. Triple coincidences between the 166-keV gamma ray, the La satellite Kα x ray, and the La hypersatellite Kα x ray were measured using two intrinsic Ge detectors. We looked for the sum of two of the three radiations in one detector in coincidence with the third radiation in the other detector. The probability of double K-shell vacancy production per K-shell electron capture (PKK) was found to be (2.0±1.6)x10-6. From this and the known PKK for 131Cs we estimate a probability for zero K-shell vacancy production (shakedown) per K-shell electron capture of approx-lt 2.4x10-5 for 139Ce

  2. K-shell ionization in the electron and positron decays of 64Cu

    International Nuclear Information System (INIS)

    The total K-ionization probabilities accompanying the β+ and β- decays of 64Cu, P/sub K/(β+), and P/sub K/(β-) were determined from coincidence and singles K x-ray spectra of Ni and Zn to be (13.2 +- 0.8) x 10-4 and (11.9 +- 0.8) x 10-4, respectively, using a high resolution Si(Li) photon spectrometer. P/sub K/(β+)/P/sub K/(β-) was measured directly and independently to be 1.26 +- 0.10, in fair agreement with the ratio of the separate measurements 1.11 +- 0.10. While the average ratio is in agreement with the shaking theory of Isozumi, Shimizu, and Mukoyama, the individual values are a factor of approx. 1.5 larger than their predictions. A similar approximately twofold excess over the Isozumi, Shimizu, and Mukoyama hydrogenic-wave-function-based predictions has been observed for almost all cases of K-shell shaking in β- decay, and now also for this first reported measurement in β+ decay. The measured ratio is the first experimental evidence affirming the previously recognized and acknowledged error of a factor of 2 (excess) for shakeoff in β- decay (but not in β+ decay) in the theory of Law and Campbell. No evidence was found for a postulated Ni K vacancy production mechanism, in which the positron annihilates with a K electron internal to the parent atom, exceeding a few percent of K shaking in positron decay

  3. 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

  4. K-shell fluorescence yields and their uncertainties for use in hybrid K-edge densitometry

    International Nuclear Information System (INIS)

    Hybrid K-edge densitometry (HKED) is a nondestructive analytical assay technique used to provide rapid determination of actinide concentration in tank solutions. Of special interest for HKED is the estimation, along with associated uncertainties, of the ratio of the fluorescence yields, ωK, of uranium and plutonium. Limited experimental data for ωK(Z) as a function of atomic number, Z, exist and the data are subject to experimental uncertainty. Previous studies have provided values for ωK(Z) with uncertainty estimates but have not included covariance information. We use a phenomenological model with a bootstrapping method to generate the ratio ωK(94)/ωK(92) and associated uncertainty. (author)

  5. Evidence for πK-atoms with DIRAC

    Science.gov (United States)

    Adeva, B.; Afanasyev, L.; Allkofer, Y.; Amsler, C.; Anania, A.; Benelli, A.; Brekhovskikh, V.; Caragheorgheopol, G.; Cechak, T.; Chiba, M.; Chliapnikov, P.; Ciocarlan, C.; Constantinescu, S.; Curceanu, C.; Detraz, C.; Dreossi, D.; Drijard, D.; Dudarev, A.; Duma, M.; Dumitriu, D.; Fungueiriño, J. L.; Gerndt, J.; Gorin, A.; Gorchakov, O.; Gritsay, K.; Guaraldo, C.; Gugiu, M.; Hansroul, M.; Hons, Z.; Horikawa, S.; Iliescu, M.; Karpukhin, V.; Kluson, J.; Kobayashi, M.; Komarov, V.; Kruglov, V.; Kruglova, L.; Kulikov, A.; Kuptsov, A.; Kurochkin, I.; Lamberto, A.; Lanaro, A.; Lapshin, V.; Lednicky, R.; Levi Sandri, P.; Lopez Aguera, A.; Lucherini, V.; Manuilov, I.; Mariñas, C.; Nemenov, L.; Nikitin, M.; Okada, K.; Olchevskii, V.; Pentia, M.; Penzo, A.; Pló, M.; Rappazzo, G. F.; Regenfus, C.; Rochet, J.; Romero, A.; Ronjin, V.; Ryazantsev, A.; Rykalin, V.; Saborido, J.; Schacher, J.; Sidorov, A.; Smolik, J.; Sugimoto, S.; Takeutchi, F.; Tarasov, A.; Tauscher, L.; Trojek, T.; Trusov, S.; Utkin, V.; Vázquez Doce, O.; Vrba, T.; Yazkov, V.; Yoshimura, Y.; Zhabitsky, M.; Zrelov, P.

    2009-04-01

    We present evidence for the first observation of electromagnetically bound π±K∓-pairs (πK-atoms) with the DIRAC experiment at the CERN-PS. The πK-atoms are produced by the 24 GeV / c proton beam in a thin Pt-target and the π± and K∓-mesons from the atom dissociation are analyzed in a two-arm magnetic spectrometer. The observed enhancement at low relative momentum corresponds to the production of 173 ± 54πK-atoms. The mean life of πK-atoms is related to the s-wave πK-scattering lengths, the measurement of which is the goal of the experiment. From these first data we derive a lower limit for the mean life of 0.8 fs at 90% confidence level.

  6. Spectroscopy and Dynamics of K Atoms on Argon Clusters.

    Science.gov (United States)

    Douady, J; Awali, S; Poisson, L; Soep, B; Mestdagh, J M; Gervais, B

    2015-06-11

    We present a combined experimental and simulation study of the 4s → 4p photoexcitation of the K atom trapped at the surface of ArN clusters made of a few hundred Ar atoms. Our experimental method based on photoelectron spectroscopy allows us to firmly establish that one single K atom is trapped at the surface of the cluster. The absorption spectrum is characterized by the splitting of the atomic absorption line into two broad bands, a Π band associated with p orbitals parallel to the cluster surface and a Σ band associated with the perpendicular orientation. The spectrum is consistent with observations reported for K atoms trapped on lighter inert gas clusters, but the splitting between the Π and Σ bands is significantly larger. We show that a large amount of K atoms are transiently stuck and eventually lost by the Ar cluster, in contrast with previous observations reported for alkaline earth metal systems. The excitation in the Σ band leads systematically to the ejection of the K atom from the Ar cluster. On the contrary, excitation in the Π band leads to the formation of a bound state. In this case, the analysis of the experimental photoelectron spectrum by means of nonadiabatic molecular dynamics simulation shows that the relaxation drives the system toward a basin where the coordination of the K atom is 2.2 Ar atoms on the average, in a poorly structured surface. PMID:25854161

  7. 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)

  8. 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.)

  9. 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

  10. 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.)

  11. 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...

  12. K-shell electron shakeoff in the positron decay of 58Co

    International Nuclear Information System (INIS)

    The probability for K-shell electron shakeoff in the positron decay of 58Co has been measured by recording coincidences between the annihilation radiation produced subsequent to the positron decay and the Fe K x rays produced when the K-shell vacancy is filled. This probability was found to be (13.8 +- 2.4) x 10-4, which is approximately 2 times larger than recent theoretical predictions by Law and Suzuki

  13. 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...

  14. 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.

  15. Structure determination in 55-atom Li-Na and Na-K nanoalloys.

    Science.gov (United States)

    Aguado, Andrés; López, José M

    2010-09-01

    The structure of 55-atom Li-Na and Na-K nanoalloys is determined through combined empirical potential (EP) and density functional theory (DFT) calculations. The potential energy surface generated by the EP model is extensively sampled by using the basin hopping technique, and a wide diversity of structural motifs is reoptimized at the DFT level. A composition comparison technique is applied at the DFT level in order to make a final refinement of the global minimum structures. For dilute concentrations of one of the alkali atoms, the structure of the pure metal cluster, namely, a perfect Mackay icosahedron, remains stable, with the minority component atoms entering the host cluster as substitutional impurities. At intermediate concentrations, the nanoalloys adopt instead a core-shell polyicosahedral (p-Ih) packing, where the element with smaller atomic size and larger cohesive energy segregates to the cluster core. The p-Ih structures show a marked prolate deformation, in agreement with the predictions of jelliumlike models. The electronic preference for a prolate cluster shape, which is frustrated in the 55-atom pure clusters due to the icosahedral geometrical shell closing, is therefore realized only in the 55-atom nanoalloys. An analysis of the electronic densities of states suggests that photoelectron spectroscopy would be a sufficiently sensitive technique to assess the structures of nanoalloys with fixed size and varying compositions. PMID:20831313

  16. 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)

  17. 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.

  18. New version: GRASP2K relativistic atomic structure package

    Science.gov (United States)

    Jönsson, P.; Gaigalas, G.; Bieroń, J.; Fischer, C. Froese; Grant, I. P.

    2013-09-01

    comprehensive user manual in pdf format for the program package has been added. Restrictions: The packing algorithm restricts the maximum number of orbitals to be ≤214. The tables of reduced coefficients of fractional parentage used in this version are limited to subshells with j≤9/2 [5]; occupied subshells with j>9/2 are, therefore, restricted to a maximum of two electrons. Some other parameters, such as the maximum number of subshells of a CSF outside a common set of closed shells are determined by a parameter.def file that can be modified prior to compile time. Unusual features: The bioscl3 program reports transition data in the same format as in Atsp2K [6], and the data processing program tables of the latter package can be used. The tables program takes a name.lsj file, usually a concatenated file of all the .lsj transition files for a given atom or ion, and finds the energy structure of the levels and the multiplet transition arrays. The tables posted at the website http://atoms.vuse.vanderbilt.edu are examples of tables produced by the tables program. With the extension of coefficients of fractional parentage to j=9/2, calculations for the lanthanides and actinides become possible. Running time: CPU time required to execute test cases: 70.5 s.

  19. Atomic layer deposition of high-k oxides on graphene

    OpenAIRE

    Alles, Harry; Aarik, Jaan; Kozlova, Jekaterina; Niilisk, Ahti; Rammula, Raul; Sammelselg, Väino

    2011-01-01

    Comment: Graphene - Synthesis, Characterization, Properties and Applications, Jian Ru Gong (Ed.), ISBN: 978-953-307-292-0, InTech, Available from: http://www.intechopen.com/articles/show/title/atomic-layer-deposition-of-high-k-oxides-on-graphene

  20. 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...

  1. 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...

  2. K-shell spectroscopy in hot plasmas: Stark effect, Breit interaction and QED corrections

    CERN Document Server

    Pain, Jean-Christophe; Comet, Maxime; Gilles, Dominique

    2016-01-01

    The broadening of lines by Stark effect is widely used for inferring electron density and temperature in plasmas. Stark-effect calculations often rely on atomic data (transition rates, energy levels,...) not always exhaustive and/or valid only for isolated atoms. In this work, we first present a recent development in the detailed opacity code SCO-RCG for K-shell spectroscopy. The approach is adapted from the work of Gilles and Peyrusse. Neglecting non-diagonal terms in dipolar and collision operators, the line profile is expressed as a sum of Voigt functions associated to the Stark components. The formalism relies on the use of parabolic coordinates and the relativistic fine-structure of Lyman lines is included by diagonalizing the hamiltonian matrix associated to quantum states having the same principal quantum number n. The SCO-RCG code enables one to investigate plasma environment effects, the impact of the microfield distribution, the decoupling between electron and ion temperatures and the role of satell...

  3. Si K-shell ionization and electron transfer cross sections: Solid targets

    International Nuclear Information System (INIS)

    The Si K x-ray production cross sections for F/sup q/+(q = 3--9) ion impact in the energy range of 0.4--2.2 MeV/amu are determined in the limit of a vanishingly thin target from the observed target thickness dependence of the x-ray yields. The ionization cross sections are deduced from the measured x-ray production cross sections using an average fluorescence yield (omega-tilde = 1.5ω0, where ω0 is the fluorescence yield for an atom with single K vacancy) determined from high-resolution x-ray spectra and configuration fluorescence yields. For F/sup q/+ (q 9+ ions and those for F/sup q/+ ions (q < or = 6). The results are compared with the prediction based on the two-state atomic-expansion method and that based on the modified Oppenheimer-Brinkman-Kramers approximation. A comparison is also made between the Si solid-target measurements with those obtained for gaseous Ne and Ar gas targets. The solid-target and gas-target data are consistent at 1.58 MeV/amu. Finally, from a comparison between the measured equilibrium x-ray yields and the calculated x-ray yields using the equilibrium charge distribution of projectiles after passing through foils, it is found that the projectiles have a considerably larger number of K-shell vacancies inside solids than after passing through solids at lower-impact energies

  4. Evidence for $\\pi K$ -atoms with DIRAC-II

    CERN Document Server

    Allkofer, Yves

    2008-01-01

    DIRAC-II is a fixed-target experiment at the CERN Proton Synchroton (PS) which has been designed to search for piK atoms, a bound state of a pi±K± pair, and measure their lifetime. These atoms are observed through an excess of low energetic piK pairs over the background, detected in the two spectrometer arms. This excess comes from the ionization of piK atoms in the target and can be related to their mean life. The piK S-wave scattering length combination |a1/2 - a3/2| (for isospin 1/2 and 3/2) can be related to the latter. The aim of the upgraded DIRAC-II experiment is a measurement of the scattering length combination |a1/2 - a3/2| with a precision of 5%. piK atoms have not been observed so far. The original DIRAC experiment was designed to measure the scattering lengths of pipi atoms. So far, close to 15 000 atoms have been detected, leading to a precision on |a0 - a2| which is better than 10%. In chiral perturbation theories (ChPT) the pipi scattering lengths have been calculated with 2% precision a...

  5. 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...

  6. 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)

  7. 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)

  8. Energy and decay width of the pi-K atom

    CERN Document Server

    Jallouli, H

    2006-01-01

    The energy and decay width of the pi-K atom are evaluated in the framework of the quasipotential-constraint theory approach. The main electromagnetic and isospin symmetry breaking corrections to the lowest-order formulas for the energy shift from the Coulomb binding energy and for the decay width are calculated. They are estimated to be of the order of a few per cent. We display formulas to extract the strong interaction S-wave pi-K scattering lengths from future experimental data concerning the pi-K atom.

  9. Chemical effect on the K shell fluorescence yield of Fe, Mn, Co, Cr and Cu compounds

    Indian Academy of Sciences (India)

    U Turgut

    2004-11-01

    Chemical effects on the K shell fluorescence yields of Fe, Mn, Co, Cr and Cu compounds were investigated. Samples were excited using 59.5 keV energy photons from a 241Am radioisotope source. K X-rays emitted by samples were counted by a Si(Li) detector with a resolution 160 eV at 5.9 keV. Chemical effects on the K shell fluorescence yields (K) for Fe, Mn, Co, Cr and Cu compounds were observed. The values are compared with theoretical, semiempirical fit and experimental ones for the pure elements.

  10. Charge exchange produced K-shell x-ray emission from Ar16+ in a tokamak plasma with neutral beam injection

    Energy Technology Data Exchange (ETDEWEB)

    Beiersdorfer, P; Bitter, M; Marion, M; Olson, R E

    2004-12-27

    High-resolution spectroscopy of hot tokamak plasma seeded with argon ions and interacting with an energetic, short-pulse neutral hydrogen beam was used to obtain the first high-resolution K-shell x-ray spectrum formed solely by charge exchange. The observed K-shell emission of Ar{sup 16+} is dominated by the intercombination and forbidden lines, providing clear signatures of charge exchange. Results from an ab initio atomic cascade model provide excellent agreement, validating a semiclassical approach for calculating charge exchange cross sections.

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

    International Nuclear Information System (INIS)

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-12-15

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

  13. K-shell fluorescence yields for elements with 6≤Z≤99

    International Nuclear Information System (INIS)

    In this study, empirical K-shell fluorescence yields (ωK) from the available experimental data for elements with 6≤Z≤99 were calculated. The experimental data are fitted using the quantity (ωK/(1-ωK))1/q (where q=3, 3.5 and 4) vs. Z to deduce the empirical fluorescence yields. A comparison is made between the results of the procedures followed here and the literature theoretical and empirical values.

  14. Spectra and decays of pi pi and pi K atoms

    OpenAIRE

    J. Schweizer

    2004-01-01

    We describe the spectra and decays of pi pi and pi K atoms within a non-relativistic effective field theory. The evaluations of the energy shifts and widths are performed at next-to-leading order in isospin symmetry breaking. We provide general formulae for all S-states, and discuss the states with angular momentum one in some detail. The prediction for the lifetime of the pi K atom in its ground-state yields tau = (3.7 \\pm 0.4) * 10^{-15} sec.

  15. Interaction of atomic hydrogen with charcoal at 77 K

    International Nuclear Information System (INIS)

    Full text: When the inner surface of the ITER pumping duct is covered with a thin αN-tilde:H film, the hydrogen recombination coefficient can be reduced. In this case, atomic hydrogen can reach the cryopump region and interact with charcoal cryosorbent. The interaction of thermal hydrogen molecules and atoms with charcoal has been analyzed by sorption measurements and TDS at 77 K. A stream quartz reactor with H2 RF discharge was used for the production of H atoms. The ratio of H and H2 in mixture in the afterglow zone was 1/10000. After exposure in H/H2 mixture the tube section with charcoal was warmed up to 300 K. In reference experiments the same sample of charcoal was exposed successively in H2 and CH4. After sample exposure in H/H2 mixture, the TD peak shifted to higher temperatures from 125 K (peak temperature after exposure in H2) to 150 K. The high temperature shoulder of this peak coincided with the temperature of methane release. The wide spectrum of heavy hydrocarbons formed at 77 K was registered by mass-spectrometry at charcoal heating up to 700 K. The specific adsorption volume of charcoal measured by N2 adsorption at 77 K decreased by 10-15%. (author)

  16. 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...

  17. 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.

  18. 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.

  19. 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)

  20. 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.

  1. 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.

  2. 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.

  3. Carbon K-shell photoelectron angular distribution from fixed-in-space CO2 molecules

    International Nuclear Information System (INIS)

    Measurements of photoelectron angular distributions for carbon K-shell ionization of fixed-in-space CO2 molecules with the molecular axis oriented along, perpendicular and at 45 degrees to the electric vector of the light are reported. The major features of these measured spectra are fairly well reproduced by calculations employing a relaxed-core Hartree-Fock approach. In contrast to the angular distribution for K-shell ionization of N2, which exhibits a rich structure dominated by the f-wave (l=3) at the shape resonance, the angular distribution for carbon K-shell photoionization of CO2 is quite unstructured over the entire observed range across the shape resonance. (letter to the editor)

  4. K-shell spectroscopic diagnosis of suprathermal electrons at fusion-relevant environmental conditions

    Science.gov (United States)

    Renner, O.; Šmíd, M.; Khaghani, D.; Rosmej, F. B.

    2016-03-01

    Fast-electron-induced changes in the ion charge distribution lead to a substantial modification of radiative properties of x-ray emitting systems. We report Cu K-shell spectra emitted from 1.5-μm-thick Cu foils irradiated by laser intensities up to 5×1016 W/cm2 using the fundamental and frequency tripled radiation of the Prague iodine laser system PALS, i.e., at conditions characteristic for laser spikes anticipated in the shock ignition scheme. The emission of the lower-ionization-stage ions observed as a fine structure merged with the Cu Kα12 doublet and spectral lines corresponding to transitions in He-like to Ne-like Cu atoms were identified. The spectra analysis based on a combination of MULTI2D hydrodynamic modelling of the plasma evolution and its emissivity synthesized by collisional-radiative code FLYCHK provides information on distribution of hot electron fractions at low plasma temperatures. The procedure used for interpretation of experimental data contributes to a development of alternative methods for diagnosis of suprathermal electrons.

  5. Biological effects induced by K photoionization in the DNA atoms

    International Nuclear Information System (INIS)

    An experiment has been made at the Lure using ultra soft X radiations (340 eV) to check the hypothesis that the K ionizations of DNA atoms could be the critical events at the origin of ionizing radiations lethality and then despite of a low probability. (N.C.)

  6. Exotic atoms, K-nucleus scattering and hypernuclei

    International Nuclear Information System (INIS)

    Recent progress in exotic atom physics, kaon-nucleus scattering, and hypernuclear physics is reviewed. Specific problems discussed include searches for muon-nucleon interactions beyond QED, a comparison of data and recent calculation of K+- + 12C elastic and inelastic scattering, as well as recent studies of Σ and Λ hypernuclei including new data on the level structure of 13C/Λ

  7. Inner-shell photodetachment from the K- ion

    International Nuclear Information System (INIS)

    We have measured the relative cross section for photodetachment from the K- ion for the process K- + hν→ K+ + 2e- over the photon energy range 21- 24.5 eV. The structures in the measured cross section are associated with correlated processes involving the detachment or excitation of a 3p core electron, processes which are often accompanied by the excitation of one or more valence electrons. The most prominent feature in the cross section is a strong resonance arising from the excitation of a 3p electron from the core and a 4s valence electron. As in previous experiments on double excitation of valence electrons, electron correlation is seen to play an important role in the dynamics of negative ions

  8. K-shell jump ratios and jump factors for molybdenum and silver by using 2D-geometrical configuration and a weak gamma source

    International Nuclear Information System (INIS)

    The article presents a simple method of measuring K-shell absorption jump ratios and jump factors for elements in the field of X-ray spectroscopy. The K-shell jump ratios and jump factors for Molybdenum and Silver are measured by adopting 2ŏ-geometrical configuration and a weak gamma source. The characteristic K X-ray photons are excited in the targets using 32.8 keV barium X-ray photons from a weak 137Cs radioactive source that is produced due to the internal conversion of cesium nucleus (IC). The fluorescent K X-ray photons are detected using low energy Si(Li) detector coupled to a 8k multichannel analyser. The K X-ray intensity ratios from X-ray fluorescent spectrum are measured experimentally, the total atomic attenuation cross section and the total atomic scattering cross sections are calculated using WinXcom software. The K-shell jump factor and jump ratio are computed using the measured K X-ray intensity ratios and the calculated Ka, X-ray production cross section. The computed values of K-shell jump factor and jump ratio for molybdenum and silver are compared with the theoretical values and others' experimental data and are presented. The amount of uncertainty in the experimental measurement of K X-ray intensity ratios is less than 5%. Thus the 2ŏ-geometrical configuration method with weak gamma source can be an alternative simple method to measure the jump factors and the jump ratios of pure elements in the field of X-ray spectroscopy. (author)

  9. Observation of Tri-photon K-Shell X-Rays

    Institute of Scientific and Technical Information of China (English)

    CHENG Yao; XIA Bing; LI Jin

    2006-01-01

    @@ We report the observation of coincidence of three K-shell x-rays generated from the long-lived rhodium isomer excited by bremsstrahlung irradiation. Our previous report revealed that the E3 Mossbauer transition has anisotropic emission due to anisotropic gravitational acceleration [Chin. Phys. Lett. 22 (2005) 2530]. Now, from broader energy-resolved spectra, we further discover abnormal coincidences and abnormalsum energies of the three K-shell x-rays. The coincidence cannot be explained by currently understood photon statistics, since the measured tri-photon count and the pile-up estimate differ by three orders of magnitude.

  10. Interaction of atomic hydrogen with charcoal at 77 K

    International Nuclear Information System (INIS)

    Charcoal is a working material of sorption cryopumps in the ITER project. The interaction of thermal hydrogen molecules and atoms with charcoal has been analyzed by TDS (77-300 K) and sorption measurements at 77 K. A stream quartz reactor with an H2 RF discharge was used for the production of H atoms. The ratio of H and H2 in the gas mixture in the afterglow zone was ∼10-4, hydrogen flow and inlet pressure were 6.9 sccm and 30 Pa, respectively. After exposure in the H/H2 mixture during 1 hour the marked change in the shape of the TD spectra and decrease of the charcoal sorption capacity for hydrogen and nitrogen were detected. A wide spectrum of hydrocarbon fragments formed at 77 K was registered by mass-spectrometry at charcoal heating up to 700 K. The specific adsorption volume of charcoal, which was measured by N2 adsorption at 77 K, decreased directly as amount of H atoms passed through the section with charcoal. (author)

  11. Cross Sections for K-shell X-ray Production by Hydrogen and Helium Ions in Elements from Beryllium to Uranium

    International Nuclear Information System (INIS)

    Experimental cross sections for K-shell x-ray production by hydrogen and helium ions (Z1 = 1,2) in target atoms from beryllium to uranium (Z2 = 4--92 ) are tabulated as compiled (7418 cross sections) from the literature (161 references were found) with the search for the data terminated in January 1988. These cross sections are compared with predictions of the first Born approximation and ECPSSR theory for inner-shell ionization. The ECPSSR accounts for the energy loss (E) and Coulomb deflection (C) of the projectile ion as well as for the perturbed stationary state (PSS) and relativistic (R) nature of the target's inner-shell electron.While the first Born approximation generally overestimates the data by orders of magnitude, the ECPSSR theory is confirmed to be, on the average, in agreement with the experiment to within 10%--20%. For light and heavy target atoms, however, systematic and opposite deviations are found in the low projectile-velocity regime. These deviations are associated with the influence of multiple outer-shell ionizations on the fluorescence yields of light elements, particularly in ionization by helium ions, and with the inaccuracy of the ECPSSR theory in the reproduction of relativistic calculations for ionization of heavy elements. The remaining discrepancies at moderate projectile velocities are prima facie attributed to inadequacies of a screened hydrogenic description for the K-shell electron

  12. First pi K atom lifetime and pi K scattering length measurements

    Czech Academy of Sciences Publication Activity Database

    Adeva, B.; Afanasyev, L.; Allkofer, Y.; Amsler, C.; Anania, A.; Aogaki, S.; Benelli, A.; Brekhovskikh, V.; Čechák, T.; Chiba, M.; Doškářová, P.; Hons, Zdeněk; Klusoň, J.; Lednický, Richard; Průša, P.; Smolík, J.; Trojek, T.; Urban, T.; Vrba, T.; Zrelov, P.

    2014-01-01

    Roč. 735, JUL (2014), s. 288-294. ISSN 0370-2693 R&D Projects: GA MŠk(CZ) LG13031; GA MŠk LG14004 Institutional support: RVO:68378271 ; RVO:61389005 Keywords : DIRAC * QCD Subject RIV: BG - Nuclear, Atom ic and Molecular Physics, Colliders; BE - Theoretical Physics (FZU-D) Impact factor: 6.131, year: 2014

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

    International Nuclear Information System (INIS)

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

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

    Science.gov (United States)

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

    2014-07-28

    Most of the work done on the linear response kernel χ(r,r') has focussed on its atom-atom condensed form χAB. Our previous work [Boisdenghien et al., J. Chem. Theory Comput., 2013, 9, 1007] was the first effort to truly focus on the non-condensed form of this function for closed (sub)shell atoms in a systematic fashion. In this work, we extend our method to the open shell case. To simplify the plotting of our results, we average our results to a symmetrical quantity χ(r,r'). This allows us to plot the linear response kernel for all elements up to and including argon and to investigate the periodicity throughout the first three rows in the periodic table and in the different representations of χ(r,r'). Within the context of Spin Polarized Conceptual Density Functional Theory, the first two-dimensional plots of spin polarized linear response functions are presented and commented on for some selected cases on the basis of the atomic ground state electronic configurations. Using the relation between the linear response kernel and the polarizability we compare the values of the polarizability tensor calculated using our method to high-level values. PMID:24837234

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

    International Nuclear Information System (INIS)

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

  16. Bright x-ray stainless steel K-shell source development at the National Ignition Facility

    International Nuclear Information System (INIS)

    High x-ray conversion efficiency (XRCE) K-shell sources are being developed for high energy density experiments for use as backlighters and for the testing of materials exposed to high x-ray fluxes and fluences. Recently, sources with high XRCE in the K-shell x-ray energy range of iron and nickel were investigated at the National Ignition Facility (NIF). The x-ray conversion efficiency in the 5–9 keV spectral range was determined to be 6.8% ± 0.3%. These targets were 4.1 mm diameter, 4 mm tall hollow epoxy tubes having a 50 μm thick wall supporting a tube of 3 to 3.5 μm thick stainless steel. The NIF laser deposited ∼460 kJ of 3ω light into the target in a 140 TW, 3.3 ns square pulse. The absolute x-ray emission of the source was measured by two calibrated Dante x-ray spectrometers. Time resolved images filtered for the Fe K-shell were recorded to follow the heating of the target. Time integrated high-resolution spectra were recorded in the K-shell range

  17. Bright x-ray stainless steel K-shell source development at the National Ignition Facility

    Energy Technology Data Exchange (ETDEWEB)

    May, M. J.; Fournier, K. B.; Colvin, J. D.; Barrios, M. A.; Dewald, E. L.; Moody, J.; Patterson, J. R.; Schneider, M.; Widmann, K. [Lawrence Livermore National Laboratory, P.O. Box 808 L170, Livermore, California 94551 (United States); Hohenberger, M.; Regan, S. P. [Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623 (United States)

    2015-06-15

    High x-ray conversion efficiency (XRCE) K-shell sources are being developed for high energy density experiments for use as backlighters and for the testing of materials exposed to high x-ray fluxes and fluences. Recently, sources with high XRCE in the K-shell x-ray energy range of iron and nickel were investigated at the National Ignition Facility (NIF). The x-ray conversion efficiency in the 5–9 keV spectral range was determined to be 6.8% ± 0.3%. These targets were 4.1 mm diameter, 4 mm tall hollow epoxy tubes having a 50 μm thick wall supporting a tube of 3 to 3.5 μm thick stainless steel. The NIF laser deposited ∼460 kJ of 3ω light into the target in a 140 TW, 3.3 ns square pulse. The absolute x-ray emission of the source was measured by two calibrated Dante x-ray spectrometers. Time resolved images filtered for the Fe K-shell were recorded to follow the heating of the target. Time integrated high-resolution spectra were recorded in the K-shell range.

  18. 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...

  19. 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.

  20. Model uncertainties of local-thermodynamic-equilibrium K-shell spectroscopy

    Science.gov (United States)

    Nagayama, T.; Bailey, J. E.; Mancini, R. C.; Iglesias, C. A.; Hansen, S. B.; Blancard, C.; Chung, H. K.; Colgan, J.; Cosse, Ph.; Faussurier, G.; Florido, R.; Fontes, C. J.; Gilleron, F.; Golovkin, I. E.; Kilcrease, D. P.; Loisel, G.; MacFarlane, J. J.; Pain, J.-C.; Rochau, G. A.; Sherrill, M. E.; Lee, R. W.

    2016-09-01

    Local-thermodynamic-equilibrium (LTE) K-shell spectroscopy is a common tool to diagnose electron density, ne, and electron temperature, Te, of high-energy-density (HED) plasmas. Knowing the accuracy of such diagnostics is important to provide quantitative conclusions of many HED-plasma research efforts. For example, Fe opacities were recently measured at multiple conditions at the Sandia National Laboratories Z machine (Bailey et al., 2015), showing significant disagreement with modeled opacities. Since the plasma conditions were measured using K-shell spectroscopy of tracer Mg (Nagayama et al., 2014), one concern is the accuracy of the inferred Fe conditions. In this article, we investigate the K-shell spectroscopy model uncertainties by analyzing the Mg spectra computed with 11 different models at the same conditions. We find that the inferred conditions differ by ±20-30% in ne and ±2-4% in Te depending on the choice of spectral model. Also, we find that half of the Te uncertainty comes from ne uncertainty. To refine the accuracy of the K-shell spectroscopy, it is important to scrutinize and experimentally validate line-shape theory. We investigate the impact of the inferred ne and Te model uncertainty on the Fe opacity measurements. Its impact is small and does not explain the reported discrepancies.

  1. Determination of experimental K-shell fluorescence yield for potassium and calcium compounds

    Indian Academy of Sciences (India)

    E Tiraşoğlu; Ö Söğüt

    2008-03-01

    K-shell fluorescence yields were experimentally determined for potassium and calcium compounds using a Si(Li) X-ray detector system (FWHM=5.96 keV at 160 eV). The samples were excited by 5.96 keV photons produced by a 55Fe radioisotope source. The experimental values are systematically lower than the theoretical values.

  2. K-shell ionisation in the positron decay branch of 58Co

    International Nuclear Information System (INIS)

    The number of K-shell vacancies produced per positron emission has been measured for the #betta#+ decay branch of 58Co. The result, (16.6+-2.1) x 10-4 vacancies per positron, is in reasonable agreement with a recent independent measurement but is in severe disagreement with the latest theoretical prediction. (author)

  3. Comment on ''Double K-shell ionization in the electron capture decay of 55Fe''

    International Nuclear Information System (INIS)

    The corrections made in a recent paper to the published values for double K-shell ionization in the electron capture decays of 54Mn and 65Zn are not applicable to the data from which these values were derived. Attention is called to a recent article that is relevant to the topic of the paper

  4. Energy and decay width of the pi-K atom

    OpenAIRE

    Jallouli, H.; Sazdjian, H.

    2006-01-01

    The energy and decay width of the pi-K atom are evaluated in the framework of the quasipotential-constraint theory approach. The main electromagnetic and isospin symmetry breaking corrections to the lowest-order formulas for the energy shift from the Coulomb binding energy and for the decay width are calculated. They are estimated to be of the order of a few per cent. We display formulas to extract the strong interaction S-wave pi-K scattering lengths from future experimental data concerning ...

  5. Criticality safety evaluation of disposing of K Basin sludge in double-shell tank AW-105

    Energy Technology Data Exchange (ETDEWEB)

    ROGERS, C.A.

    1999-06-04

    A criticality safety evaluation is made of the disposal of K Basin sludge in double-shell tank (DST) AW-105 located in the 200 east area of Hanford Site. The technical basis is provided for limits and controls to be used in the development of a criticality prevention specification (CPS). A model of K Basin sludge is developed to account for fuel burnup. The iron/uranium mass ration required to ensure an acceptable magrin of subcriticality is determined.

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

    CERN Document Server

    Tomza, Michał

    2013-01-01

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

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

    Science.gov (United States)

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

    2009-11-01

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

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

    International Nuclear Information System (INIS)

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

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

    DEFF Research Database (Denmark)

    Engelbrekt, Christian; Seselj, Nedjeljko; Poreddy, Raju;

    2016-01-01

    We present a facile synthesis protocol for atomically thin platinum (Pt) shells on top of gold (Au) nanoparticles (NPs) (Au@PtNPs) in one pot under mild conditions. The Au@PtNPs exhibited remarkable stability (> 2 years) at room temperature. The synthesis, bimetallic nanostructures and catalytic...... electrooxidation of sustainable fuels (i.e. formic acid, methanol and ethanol), and selective hydrogenation of benzene derivatives. Especially high activity was achieved for formic acid oxidation, 549 mA (mgPt)−1 (at 0.6 V vs. SCE), which is 3.5 fold higher than a commercial < 5 nm PtNP catalyst. Excellent...

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

    CERN Document Server

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

    2015-01-01

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

  11. History and future perspectives of the Monte Carlo shell model -from Alphleet to K computer-

    International Nuclear Information System (INIS)

    We report a history of the developments of the Monte Carlo shell model (MCSM). The MCSM was proposed in order to perform large-scale shell-model calculations which direct diagonalization method cannot reach. Since 1999 PC clusters were introduced for parallel computation of the MCSM. Since 2011 we participated the High Performance Computing Infrastructure Strategic Program and developed a new MCSM code for current massively parallel computers such as K computer. We discuss future perspectives concerning a new framework and parallel computation of the MCSM by incorporating conjugate gradient method and energy-variance extrapolation

  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. 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

  15. 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

  16. Alloying effect on K-shell fluorescence parameters of porous NiTi shape memory alloys

    International Nuclear Information System (INIS)

    Highlights: • The Kα,β shell production cross-sections and Kβ/Kα intensity ratios of porous NiTi SMAs were determined by ED-XRF. • To analyze the changes in the structures due to the preheating and solution heat treatment processes, XRD and XPS measurements were also performed. • The deviations between the experimental and theoretical were interpreted to charge transfer phenomena. - Abstract: The Kα,β shell production cross-sections and Kβ/Kα intensity ratios of porous Ni −49 at% Ti shape memory alloys were determined using energy dispersive X-ray fluorescence (EDXRF) technique. Also, the alloying effect on the K shell fluorescence parameters was investigated. The samples were excited by 59.5 keV γ-rays from an 241Am annular radioactive source. The K X-rays emitted by the samples were counted by an Ultra-LEGe detector with a resolution of 150 eV at 5.9 keV. The structure analyses of the samples were also made using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The deviations between the present results and theoretical values, calculated for pure Ti and Ni, were attributed to charge transfer phenomena and/or rearrangement of valance shell electrons and porosity

  17. Selective hydrogen atom abstraction by hydrogen atoms in photolysis and radiolysis of alkane mixtures at 770 K

    International Nuclear Information System (INIS)

    Selective hydrogen atom abstraction reaction by H atoms, has been found in Isobutane, 2,2,3,3-tetramethylbutane(TMB), cyclopropane matrices besides neopentane matrix. The selective hydrogen atom abstraction reaction in neopentane-isobutane mixture is affected by the difference of kinetic energies of H atoms. The reaction occurs more favorably with decreasing the kinetic energy of H atoms. Competitive reaction between c-C6H12 and Hi for H atoms has been studied in the radiolysis and photolysis of neo-C5H12HI mixture at 77 K. The rate constants of these reactions in neopentane matrix are quite different from these of thermal H atom reaction, but similar to those of hot H atom reaction. Importance of the selective hydrogen atom abstraction reaction by H atoms is pointed out in the radical formation in the radiolysis of pure TMB at 77 K

  18. Updated database and new empirical values for K-shell fluorescence yields

    International Nuclear Information System (INIS)

    The measured K-shell fluorescence yield values that were reported in the literature from 1994 to 2011 were reviewed and presented in a table form (about 341 new measurements). The Weighted-mean values of experimental data were fitted by the analytical function to deduce new empirical K-shell fluorescence yields for a broad range of elements. The results were compared with the other theoretical, experimental and semi-empirical values reported in the literature. Reasonable agreement was typically obtained between our result and other works. - Highlights: ► The updated database relies on the different publications from 1994 till 2011. ► The results were presented for elements from (11Na) to (99Es). ► The experimental data are fitted to deduce the empirical fluorescence yields.

  19. K-shell ionization in the beta decay of 141Ce

    International Nuclear Information System (INIS)

    The total K-shell ionization probability accompanying the β- decay of 141Ce to the 0.145-MeV level in 141Pr was determined to be (1.79 +- 0.11) x 10-4 from Pr Kα x rays in coincidence with the 0.145-MeV gamma ray. This result is in very good agreement with the theoretical calculations of Law and Suzuki

  20. K-shell ionisation in the positron decay branch of 64Cu

    International Nuclear Information System (INIS)

    The number of K-shell vacancies per positron has been measured for the β+ decay branch of 64Cu by using a fast triple coincidence, between the annihilation quanta and the Ni x-rays, to gate the output of a high-resolution Si(Li) detector. The result, (1.33 +- 0.11) x 10-3 vacancies per positron is compared with those of other workers. (author)

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

    Science.gov (United States)

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

    2016-05-01

    X-ray absorption spectrum is a powerful tool for atomic structure detection on warm dense matter. Here, we perform first-principles molecular dynamics and X-ray absorption spectrum calculations on warm dense nitrogen along a Hugoniot curve. From the molecular dynamics trajectory, the detailed atomic structures are examined for each thermodynamical condition. The K-shell X-ray absorption spectrum is calculated, and its changes with temperature and pressure along the Hugoniot curve are discussed. The warm dense nitrogen systems may contain isolated nitrogen atoms, N2 molecules, and nitrogen clusters, which show quite different contributions to the total X-ray spectrum due to their different electron density of states. The changes of X-ray spectrum along the Hugoniot curve are caused by the different nitrogen structures induced by the temperature and the pressure. Some clear signatures on X-ray spectrum for different thermodynamical conditions are pointed out, which may provide useful data for future X-ray experiments.

  2. 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)

  3. 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)

  4. 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)

  5. K-Shell Photoionization of Nickel Ions Using R-Matrix

    Science.gov (United States)

    Witthoeft, M. C.; Bautista, M. A.; Garcia, J.; Kallman, T. R.; Mendoza, C.; Palmeri, P.; Quinet, P.

    2011-01-01

    We present R-matrix calculations of photoabsorption and photoionization cross sections across the K edge of the Li-like to Ca-like ions stages of Ni. Level-resolved, Breit-Pauli calculations were performed for the Li-like to Na-like stages. Term-resolved calculations, which include the mass-velocity and Darwin relativistic corrections, were performed for the Mg-like to Ca-like ion stages. This data set is extended up to Fe-like Ni using the distorted wave approximation as implemented by AUTOSTRUCTURE. The R-matrix calculations include the effects of radiative and Auger dampings by means of an optical potential. The damping processes affect the absorption resonances converging to the K thresholds causing them to display symmetric profiles of constant width that smear the otherwise sharp edge at the K-shell photoionization threshold. These data are important for the modeling of features found in photoionized plasmas.

  6. Variation of 3s photoionization resonance structures in a serial atomic number species Ar, K, and Ca

    International Nuclear Information System (INIS)

    Subvalence 3s-shell photoionization resonances of Ca were measured with monochromatized synchrotron radiation and photoion time-of-flight spectroscopy method. Charge resolved photoion yield spectra were obtained. Broad peak structures were found in the Ca+ spectrum and shallow window structures were found in the Ca2+ spectrum. We performed MCDF calculations to assign the resonance structures. The 3s-shell photoionization of Ar and K were also measured for comparison. A systematic increase was observed in Fano-Beutler parameter and in the resonance width along with the increase of atomic number from Z=18(Ar) to 20(Ca). We discuss also the spectral structures that could be of the 3p double-shake-up satellites, which are observed in the 3s photoionization region. (author)

  7. K-shell radiation physics in the ultrahigh optical depth pinches of the Z generator

    International Nuclear Information System (INIS)

    The 60 TW Z generator at Sandia National Laboratories is unique in its ability to strip multi-mg Al plasmas to the H- and He-like ionization stages. Such large plasma masses can produce optical depths in the principal K shell lines of 103. Thus, Z can serve as a unique laboratory facility at which radiation interactions and transport can be studied in a dense medium of extremely high x-ray opacity. In this talk the authors analyze data from shots in which arrays of alloy wires comprised of 95% Al and 5% Mg were imploded with a peak current of ∼19 MA on Z. The number of wires varied from 180 to 264, the initial array radius from 1.5 to 2.5 cm, and the mass load from 3.6 to 1.3 mg/cm. The implosion time was constant at ∼1ns. Total radiative yields of ∼1 MJ were observed, and the (Al + Mg) K shell yield increased with decreasing mass from 90 to near 200 kJ

  8. Compton scattering of 1.12 MeV gamma rays by K-shell electrons

    International Nuclear Information System (INIS)

    Two sodium iodide counters in coincidence and a twenty channel pulse height analyzer have been used to determine the pulse height distribution of 1.12 MeV gamma rays which are Compton scattered by the K-shell electrons of gold, lead and thorium. The angular variations of the differential cross section ratio, dsigma/sub K//dsigma/sub F/, have already been reported. The present measurements were made at 60 and 1000 scattering angles. At 600, lead targets of 30 mg/cm2 and 143 mg/cm2 were used. At 1000, targets of gold (13 mg/cm2), lead (143 mg/cm2) and thorium (14 mg/cm2) were used. In all cases, pulse height distributions of false coincidence events were determined and subtracted from the measured distributions in order to obtain the true distributions. A broadening of the K-shell electron Compton peak has been observed. The results of these measurements are discussed

  9. Coupled channel calculations of K-shell ionization in asymmetric collision systems

    International Nuclear Information System (INIS)

    We report theoretical results on K-shell ionization for a variety of asymmetric collision systems. The calculated ionization rates are compared with experimental data. The coupled channel formalism underlying these calculations is presented. It is based on a set of relativistic target centred states, taking a screened potential of Dirac-Fock-Slater type into account. We discuss the effects of different matrix elements, e.g. continuum-continuum couplings. The binding effect is inherently contained in our approach and described in a dynamical way. (orig.)

  10. The K-shell ionization of heavy elements induced by low energy protons

    International Nuclear Information System (INIS)

    The K-shell ionization cross sections, σKI, have been measured for Nd, Sm, Tb, Tm, and Ta targets for incident proton energies of 2.6 MeV to 3.8 MeV. The absolute σKI values have been determined by normalization to the known Coulomb excitation cross sections σc of these target nuclei. The experimental results are compared with the predictions of the SCA, PWBA models including the electron binding, Coulomb repulsion and reltivistic correction ones

  11. The grasp2K relativistic atomic structure package

    Science.gov (United States)

    Jönsson, P.; He, X.; Froese Fischer, C.; Grant, I. P.

    2007-10-01

    This paper describes grasp2K, a general-purpose relativistic atomic structure package. It is a modification and extension of the GRASP92 package by [F.A. Parpia, C. Froese Fischer, I.P. Grant, Comput. Phys. Comm. 94 (1996) 249]. For the sake of continuity, two versions are included. Version 1 retains the GRASP92 formats for wave functions and expansion coefficients, but no longer requires preprocessing and more default options have been introduced. Modifications have eliminated some errors, improved the stability, and simplified interactive use. The transition code has been extended to cases where the initial and final states have different orbital sets. Several utility programs have been added. Whereas Version 1 constructs a single interaction matrix for all the J's and parities, Version 2 treats each J and parity as a separate matrix. This block structure results in a reduction of memory use and considerably shorter eigenvectors. Additional tools have been developed for this format. The CPU intensive parts of Version 2 have been parallelized using MPI. The package includes a "make" facility that relies on environment variables. These make it easier to port the application to different platforms. The present version supports the 32-bit Linux and ibmSP environments where the former is compatible with many Unix systems. Descriptions of the features and the program/data flow of the package will be given in some detail in this report. Program summaryProgram title: grasp2K Catalogue identifier: ADZL_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADZL_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 213 524 No. of bytes in distributed program, including test data, etc.: 1 328 588 Distribution format: tar.gz Programming language: Fortran and C Computer: Intel

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

    International Nuclear Information System (INIS)

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

  13. 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.

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

    CERN Document Server

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

    2013-01-01

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

  15. Krypton K-Shell X-Ray Spectra Recorded by the HENEX Spectrometer

    International Nuclear Information System (INIS)

    High resolution x-ray spectra were recorded by the High Energy Electronic X-Ray (HENEX) spectrometer from a variety of targets irradiated by the Omega laser at the Laboratory for Laser Energetics. The HENEX spectrometer utilizes four reflection crystals covering the 1 keV to 20 keV energy range and one quartz(10-11) transmission crystal (Lau geometry) covering the 11 keV to 40 keV range. The time-integrated spectral images were recorded on five CMOS x-ray detectors. In the spectra recorded from krypton-filled gasbag and hohlraum targets, the helium-like K-shell transitions n=1-2, 1-3, and 1-4 appeared in the 13 keV to 17 keV energy range. A number of additional spectral features were observed at energies lower than the helium-like n=1-3 and n=1-4 transitions. Based on computational simulations of the spectra using the FLYCHK/FLYSPEC codes, which included opacity effects, these additional features are identified to be inner-shell transitions from the Li-like through N-like krypton charge states. The comparisons of the calculated and observed spectra indicate that these transitions are characteristic of the plasma conditions immediately after the laser pulse when the krypton density is 2x1018 cm-3 and the electron temperature is in the range 2.8 keV to 3.2 keV. These spectral features represent a new diagnostic for the charge state distribution, the density and electron temperature, and the plasma opacity. Laboratory experiments indicate that it is feasible to record K-shell spectra from gold and higher Z targets in the > 60 keV energy range using a Ge(220) transmission crystal

  16. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-05-15

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

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

    Science.gov (United States)

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

    2015-05-01

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

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

    International Nuclear Information System (INIS)

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

  20. New procedure calculation of K-shell ionization cross sections by proton impact

    International Nuclear Information System (INIS)

    The database, which relies on different compilations available in the literature and on other experimental values extracted from papers published from 1992 till 2010, is used, within the individual treatment of the elements from beryllium (4Be) to uranium (92U), to deduce the empirical cross sections. These experimental data can be presented in a single curve, depending on a scaling law extracted from studies in the most familiar theories of collision (PWBA and BEA). Then, a fourth order polynomial was used to fit very well the existing database of K-shell ionization cross sections by proton. This procedure generates a new set of parameters to calculate empirical cross sections. Following the present procedure, our results are compared with those obtained using the ECPSSR model where a discrepancy is observed in the low-proton energy regime. - Highlights: → We used the experimental data to define the K-shell ionization cross sections. → These values are presented in a single curve used PWBA and BEA theories. → The empirical values are defined for each element separately.

  1. K-shell radiation physics in the ultrahigh optical depth pinches of the Z generator

    International Nuclear Information System (INIS)

    Al:Mg alloy wire arrays of mass loads 1.3 endash 3.6 mg/cm have been imploded with peak currents of 19 MA on the 60 TW Z generator [R. B. Spielman et al., Phys. Plasmas 5, 2105 (1998)] at Sandia National Laboratories. The large mass loads have resulted in the highest K-shell x-ray line optical depths (∼103) produced to date in Z-pinches. Analysis of the time-resolved spectrum of a 2.1 mg/cm shot near the time of peak compression has yielded a temperature endash density profile of the pinch that approximately reproduces all features of the x-ray data except the continuum above 5 keV, which is underpredicted. The Ly α/He α ratio for Al is shown to be enhanced relative to that of Mg by two mechanisms: photopumped ladder ionization and absorption of the Al He-like line in a cool outer halo. This analysis and comparisons to some Ti shots demonstrates that the K-shell yield of Al is significantly reduced by line and continuum self-absorption, but that of Ti is not. copyright 1998 American Institute of Physics

  2. Large scale nuclear structure calculation by Monte Carlo shell model. Frontier of nuclear research by K-computer

    International Nuclear Information System (INIS)

    Strategic program field 5 was started in 2011 for the effective use of K-computer. In the field of the nuclear research, a large scale nuclear structure studies by Monte Carlo shell model calculation are being carried out at HPCI (High Performance Computing Infrastructure) Consortium. Since the introduction of the shell model by Mayer and Jensen in 1949, it succeeded in the explanation of magic numbers and has been very powerful theory. Recently, however, the great progress of nuclear physics at RIBF (RIKEN Beam Factory) and so on made it clear that the magic numbers disappear in the unstable nuclei, while different ones appear and evolutions of shell structure are considered. In this report the framework and recent results are described. In the second section of 'Shell Model Computation and Monte Carlo Shell Model', '2.1 Model space and effective interactions', '2.2 Strict diagonalization by Lanczos algorithm and its limitations' and '2.3 Framework of Monte Carlo shell model' are picked up with a figure of calculation example. In the third section 'Structure Exploration of Neutron Excess Nickel Isotopes by the Monte Carlo Shell Model' is explained showing the energy surfaces of 68Ni for 01+ and 02+. In the fourth section 'Monte Carlo Model Calculation without Assuming Closed Shell and its Visualization', density distributions in 8Be are shown after and before the angular momenta projection. In the fifth section of 'Development of Monte Carlo Shell Model Program at K-Computer', speeding up of Monte Carlo Shell Model by the parallel computation is shown. Finally it is pointed out that the HPCI program is planned to end 2015. Farther magic numbers are expected to be calculated before HPCI terminates. (S. Funahashi)

  3. 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)

  4. 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

  5. Discriminating the Progenitor Type of Supernova Remnants with Iron K-Shell Emission

    CERN Document Server

    Yamaguchi, Hiroya; Petre, Robert; Nakano, Toshio; Castro, Daniel; Enoto, Teruaki; Hiraga, Junko S; Hughes, John P; Maeda, Yoshitomo; Nobukawa, Masayoshi; Safi-Harb, Samar; Slane, Patrick O; Smith, Randall K; Uchida, Hiroyuki

    2014-01-01

    Supernova remnants (SNRs) retain crucial information about both their parent explosion and circumstellar material left behind by their progenitor. However, the complexity of the interaction between supernova ejecta and ambient medium often blurs this information, and it is not uncommon for the basic progenitor type (Ia or core-collapse) of well-studied remnants to remain uncertain. Here we present a powerful new observational diagnostic to discriminate between progenitor types and constrain the ambient medium density of SNRs solely using Fe K-shell X-ray emission. We analyze all extant Suzaku observations of SNRs and detect Fe K alpha emission from 23 young or middle-aged remnants, including five first detections (IC 443, G292.0+1.8, G337.2-0.7, N49, and N63A). The Fe K alpha centroids clearly separate progenitor types, with the Fe-rich ejecta in Type Ia remnants being significantly less ionized than in core-collapse SNRs. Within each progenitor group, the Fe K alpha luminosity and centroid are well correlate...

  6. 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

  7. 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

  8. The application of k-shell x-ray fluorescence to determine bone lead burden and its correlation with hypertension among African Americans in Gadsden County, Florida

    Science.gov (United States)

    Jackson-Edwards, Patrice

    Photons from k shell x-ray fluorescence illuminates lead atoms by measuring the characteristic x-rays which indicate the abundance of 210Pb present in a sample. The measurement utilizes a 109Cd source and a low-energy germanium detector, which has emerged as the best available technique for estimating cumulative exposure to lead in adults and for predicting lead-associated risks for adult chronic disease outcomes such as hypertension. The main focus of this study, was to show the correlation between bone lead concentration at the tibia (mean +/- standard deviation of 7+/-1 ppm) and patella (mean +/- standard deviation of 6+/-1 ppm) bone sites and hypertension (mean +/- standard deviation of the systolic standing 143+/-18mmHg, systolic sitting 140+/-17mmHg, diastolic standing 88+/-14 mmHg, and diastolic sitting 81+/-9 mmHg), among the 67 Gadsden County subjects that participated in this study. This was accomplished using FAMU's setup for the detector. The gamma rays emitted by the 109Cd source are scattered by atomic electrons in the k-shell. Excited electrons in the k-shell then spontaneously fluoresce at 88 keV as a signature of lead in the bone. The 88 keV photons are then detected at an angle of 180 degrees with respect to the incident x-ray direction and are detected by the Canberra Germanium solid-state detector bathed in liquid nitrogen. Results show that in this population all lead biomarkers (tibia lead, patella lead, and blood lead) were not significant contributors to the occurrence of hypertension. In the final logistic regression analysis, age and gender were predictors for the occurrence of hypertension at the pwill help contribute to the understanding of the body's management of lead toxicity and to KXRF techniques currently used in physics research.

  9. Accuracy of K-shell spectra modeling in high-density plasmas

    International Nuclear Information System (INIS)

    We present spectroscopic measurements of the helium-like and lithium-like argon emission supported by Thomson scattering diagnostics on gas bag targets. These data provide critical tests of plasma spectroscopic K-shell models. In particular, we have measured the line radiation in the wavelength region of the He-like Ar 1s2-1s3l transition (He-β) that is of interest for density and temperature measurements of plasmas from gas-filled targets (ne≤1021 cm-3), laser ablation targets (ne≤1022 cm-3), and inertial confinement fusion capsule implosions (ne≥1024 cm-3). The spectra show lithium-like dielectronic satellites on the red wing of the He-β line that are temperature sensitive and are known to influence the shape of the Stark-broadened line profiles observed from implosions. To examine the kinetics modeling of this complex, i.e., the He-β and its associated satellites, we have performed experiments in gas bag plasmas at densities of (0.6-1.1)x1021 cm-3 where we independently determine the electron temperature with ultraviolet Thomson scattering. The comparison of the satellite intensities with kinetics modeling shows good agreement for satellites whose upper states are populated by dielectronic capture, but shows discrepancies for inner-shell collisional excited transitions. (c) 2000 The American Physical Society

  10. Measurements of K Shell Emission of Highly Charged Ions with the XRS at EBIT

    Science.gov (United States)

    Porter, F. Scott; Beiersdorfer, P.; Boyce, K.; Brown, G. V.; Chen, H.; Kahn, S.; Kelley, R.; Kilbourne, C. A.

    2004-01-01

    The XRS/EBIT is a 32 channel microcalorimeter spectrometer operating at the electron beam ion trap (EBIT) facility at Lawrence Livermore National Laboratory. The system contains a flight candidate detector array from the XRS instrument for the Astro-E2 mission. The detector array in the XRS/EBIT is functionally identical to the flight array integrated into the XRS instrument and benefits from the enormous amount of calibration data from the XRS program. Since the XRSEBIT was upgraded with the new detector array in October 2003, the system has been used for a number of experiments including a survey of the K shell emission from He-like and H-like O, Ne, Ar, Fe, Ni and Kr as well as for L shell emission to measure the 3C/3D line ratio in Ni. Here we present some basic operational parameters of the instrument as well as direct excitation and simulated maxwellian spectra of He-like and E-like Fe. We show that the XRS instrument can resolve the Lyal and Lya2 lines from each other as well as from the dielectronic recombination satellites in thermal H-like Fe. We also show exactly how well the XRS instrument on Astro-E2 will resolve the thermal He-like triplet in collisionally excited Fe. This work was funded under NASA's Research Opportunities in Space Science program.

  11. Evidence for pi K-atoms with DIRAC

    Czech Academy of Sciences Publication Activity Database

    Adeva, B.; Afanasyev, L.; Allkofer, Y.; Amsler, C.; Anania, A.; Benelli, A.; Brekhovskikh, V.; Caragheorgheopol, G.; Čechák, T.; Chiba, M.; Chliapnikov, P.; Ciocarlan, C.; Constantinescu, S.; Curceanu, C.; Detraz, C.; Dreossi, D.; Drijard, D.; Dudarev, A.; Duma, M.; Dumitriu, D.; Fungueirino, J.L.; Gerndt, J.; Gorin, A.; Gorchakov, O.; Gritsay, K.; Guaraldo, C.; Gugiu, M.; Hansroul, M.; Hons, Zdeněk; Horikawa, S.; Iliescu, M.; Karpukhin, V.; Klusoň, J.; Kobayashi, M.; Komarov, V.; Kruglov, V.; Kruglova, L.; Kulikov, A.; Kuptsov, A.; Kurochkin, I.; Lamberto, A.; Lanaro, A.; Lapshin, V.; Lednicky, R.; Sandri, P.L.; Aguera, A.L.; Lucherini, V.; Manuilov, I.; Marinas, C.; Nemenov, L.; Nikitin, M.; Okada, K.; Olchevskii, V.; Pentia, M.; Penzo, A.; Plo, M.; Rappazzo, G.F.; Regenfus, C.; Rochet, J.; Romero, A.; Ronjin, V.; Ryazantsev, A.; Rykalin, V.; Saborido, J.; Schacher, J.; Sidorov, A.; Smolík, J.; Sugimoto, S.; Takeutchi, F.; Tarasov, A.; Tauscher, L.; Trojek, T.; Trusov, S.; Utkin, V.; Vazguez Doce, O.; Vrba, T.; Yazkov, V.; Yoshimura, Y.; Zhabitsky, M.; Zrelov, P.

    2009-01-01

    Roč. 674, č. 1 (2009), s. 11-16. ISSN 0370-2693 Institutional research plan: CEZ:AV0Z10480505 Keywords : DIRAC experiment * Exotic atoms * Scattering length Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 5.083, year: 2009

  12. Metastable Innershell Molecular State (MIMS II: K-shell X-ray satellites in heavy ion impact on solids

    Directory of Open Access Journals (Sweden)

    Young K. Bae

    2014-01-01

    Full Text Available Metastable Innershell Molecular State (MIMS, an innershell-bound ultra-high-energy molecule, was previously proposed to explain a ∼40% efficiency of soft-X-ray generation in ∼0.05 keV/amu nanoparticle impact on solids. Here, the MIMS model has been extended and applied to interpreting the experimental K-shell X-ray satellite spectra for more than 40 years in keV-MeV/amu heavy-ion impact on solids. The binding energies of the K-shell MIMS of elements from Al to Ti were determined to be 80–200 eV. The successful extension of the model to the K-shell MIMS confirms that all elements in the periodic table and their combinations are subjected to the MIMS formation.

  13. Measurement of scandium and vanadium K-shell ionization cross sections by electron impact

    International Nuclear Information System (INIS)

    Electron impact Sc and V K-shell ionization cross sections have been measured for the first time in the incident energy region from near threshold to 45 keV. Thin targets with thick substrates are used in the experiments. The influence of the substrate on measured data has been corrected by a method based upon an electron transport calculation. For Sc and V elements, the experimental data are compared with some empirical formulae and theoretical results. It is found that the experimental data for Sc and V and most of the other elements measured before (i.e. Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Nb and Mo) with the same method as presented in this paper, can be reasonably described by both Luo's theoretical results and Casnati's empirical formula. (author)

  14. K-shell ionisation in the positron decay branch of 68Ga

    International Nuclear Information System (INIS)

    The number of K-shell vacancies produced per positron emitted in the β+ decay branch of 68Ga has been found to be (10.3 +- 1.0) x 10-4. This is 50% higher than the prediction of the theory of Law and Suzuki (1982 Phys. Rev. C 25, 514), which has proved successful in β- decay, and confirms the trend of the experimental results obtained in the three other positron decays which have so far been investigated. The importance of the final-state interaction in β+ decay has recently been shown theoretically by other authors, and a successful theory will probably require a combination of their approach with that of Law and Suzuki, which emphasises many-body effects. (author)

  15. 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

  16. 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

  17. The mechanism of low-k SiOCH film modification by oxygen atoms

    International Nuclear Information System (INIS)

    The interaction of oxygen atoms with three types of plasma enhanced chemical vapor deposition low-k SiOCH films is studied. The samples were treated by O atoms in the far plasma afterglow conditions in a special experimental system designed for this study. The experimental system allowed avoiding the effect of ions and vacuum ultraviolet (VUV) photons on surface reactions and controlling the oxygen atom concentration over the samples. Fourier-transform infrared spectroscopy, x-ray fluorescence, and atomic force microscopy techniques were used to analyze the changes occurring in low-k films. Monte Carlo model for O atom interaction with low-k material that includes penetration, recombination, and reactions with methyl groups was developed. It is shown that the surface recombination on the pore wall surface determines the profile and penetration depth of O atoms into the films. The reaction of O atoms with methyl groups has lower probability and therefore proceeds in the background mode.

  18. Metastable Innershell Molecular State (MIMS) II: K-shell X-ray satellites in heavy ion impact on solids

    OpenAIRE

    Young K. Bae

    2014-01-01

    Metastable Innershell Molecular State (MIMS), an innershell-bound ultra-high-energy molecule, was previously proposed to explain a ∼40% efficiency of soft-X-ray generation in ∼0.05 keV/amu nanoparticle impact on solids. Here, the MIMS model has been extended and applied to interpreting the experimental K-shell X-ray satellite spectra for more than 40 years in keV-MeV/amu heavy-ion impact on solids. The binding energies of the K-shell MIMS of elements from Al to Ti were determined to be 80–200...

  19. Empirical K -Shell ionization cross sections of elements from 4Be to 92U for proton impact

    International Nuclear Information System (INIS)

    Experimental ionization cross sections for K-shell by protons for elements from Be to U available in the literature from 1953 to 1999 are fitted to deduce the empirical K-shell ionization cross sections, 5400 values of cross sections have been collected from various references. The deduced empirical cross sections are compared to the experimental data and to the theoretical values obtained by our research group within the ECPSSR theory and also with the reference ionization cross sections obtained by Paul and Sacher [H. Paul and J. Sacher At. Data. Nucl. Data. Tables 42 (1989) 105

  20. A semiclassical study of laser-induced atomic fluorescence from Na2, K2 and NaK

    Science.gov (United States)

    Yuan, J.-M.; Bhattacharyya, D. K.; George, T. F.

    1982-01-01

    A semiclassical treatment of laser-induced atomic fluorescence for the alkali-dimer systems Na2, K2 and NaK is presented. The variation of the fluorescence intensity with the frequency of the exciting laser photon is studied and a comparison of theoretical results with a set of experimental data is presented.

  1. K-shell decomposition reveals hierarchical cortical organization of the human brain

    Science.gov (United States)

    Lahav, Nir; Ksherim, Baruch; Ben-Simon, Eti; Maron-Katz, Adi; Cohen, Reuven; Havlin, Shlomo

    2016-08-01

    In recent years numerous attempts to understand the human brain were undertaken from a network point of view. A network framework takes into account the relationships between the different parts of the system and enables to examine how global and complex functions might emerge from network topology. Previous work revealed that the human brain features ‘small world’ characteristics and that cortical hubs tend to interconnect among themselves. However, in order to fully understand the topological structure of hubs, and how their profile reflect the brain’s global functional organization, one needs to go beyond the properties of a specific hub and examine the various structural layers that make up the network. To address this topic further, we applied an analysis known in statistical physics and network theory as k-shell decomposition analysis. The analysis was applied on a human cortical network, derived from MRI\\DSI data of six participants. Such analysis enables us to portray a detailed account of cortical connectivity focusing on different neighborhoods of inter-connected layers across the cortex. Our findings reveal that the human cortex is highly connected and efficient, and unlike the internet network contains no isolated nodes. The cortical network is comprised of a nucleus alongside shells of increasing connectivity that formed one connected giant component, revealing the human brain’s global functional organization. All these components were further categorized into three hierarchies in accordance with their connectivity profile, with each hierarchy reflecting different functional roles. Such a model may explain an efficient flow of information from the lowest hierarchy to the highest one, with each step enabling increased data integration. At the top, the highest hierarchy (the nucleus) serves as a global interconnected collective and demonstrates high correlation with consciousness related regions, suggesting that the nucleus might serve as a

  2. K-shell photoionization and interatomic Coulombic decay following Auger decay in van der Waals neon clusters

    International Nuclear Information System (INIS)

    We investigated K-shell photoionization and interatomic Coulombic decay (ICD) following Ne KL1L23Auger decay in Nen by momentum-resolved electron-ion multi-coincidence. The angular distributions of the photoelectrons depend only on the direction of the polarization vector, whereas those of the ICD electrons depend on the neither the polarization vector nor the ion emission directions.

  3. Effects of higher-coordination shells in garnets detected by XAS at the Al K-edge

    International Nuclear Information System (INIS)

    The aluminium 1 s x-ray-absorption spectra of a series of garnets, pyrope, almandine, spessartine and grossular, are compared to full multiple-scattering calculation using cluster models. An overall good agreement between experiment and calculation, extended also to the edge region,is obtained in the energy range in up to 60 e V above the threshold, provided cluster containing at least 40 atoms are used. The analysis of these garnet XAS spectra provides clear evidence on the effect of probe, XANES spectroscopy at the edge of low Z elements appears to be a perfect tool to investigate the role played by atoms located in higher-coordination shells

  4. Hot surface ionic line emission and cold K-inner shell emission from petawatt-laser irradiated Cu foil targets

    Energy Technology Data Exchange (ETDEWEB)

    Theobald, W; Akli, K; Clarke, R; Delettrez, J A; Freeman, R R; Glenzer, S; Green, J; Gregori, G; Heathcote, R; Izumi, N; King, J A; Koch, J A; Kuba, J; Lancaster, K; MacKinnon, A J; Key, M; Mileham, C; Myatt, J; Neely, D; Norreys, P A; Park, H; Pasely, J; Patel, P; Regan, S P; Sawada, H; Shepherd, R; Snavely, R; Stephens, R B; Stoeckl, C; Storm, M; Zhang, B; Sangster, T C

    2005-12-13

    A hot, T{sub e} {approx} 2- to 3-keV surface plasma was observed in the interaction of a 0.7-ps petawatt laser beam with solid copper-foil targets at intensities >10{sup 20} W/cm{sup 2}. Copper K-shell spectra were measured in the range of 8 to 9 keV using a single-photon-counting x-ray CCD camera. In addition to K{sub {alpha}} and K{sub {beta}} inner-shell lines, the emission contained the Cu He{sub {alpha}} and Ly{sub {alpha}} lines, allowing the temperature to be inferred. These lines have not been observed previously with ultrafast laser pulses. For intensities less than 3 x 10{sup 18} W/cm{sup 2}, only the K{sub {alpha}} and K{sub {beta}} inner-shell emissions are detected. Measurements of the absolute K{sub {alpha}} yield as a function of the laser intensity are in agreement with a model that includes refluxing and confinement of the suprathermal electrons in the target volume.

  5. Clear evidence of charge conjugation and parity violation in K atoms from atomic permanent electric dipole moment experiments

    CERN Document Server

    You, Pei-Lin

    2008-01-01

    Quantum mechanics thinks that atoms do not have permanent electric dipole moment (EDM) because of their spherical symmetry. Therefore, there is no polar atom in nature except for polar molecules. The electric susceptibility Xe caused by the orientation of polar substances is inversely proportional to the absolute temperature T while the induced susceptibility of atoms is temperature independent. This difference in temperature dependence offers a means of separating the polar and non-polar substances experimentally. Using special capacitor our experiments discovered that the relationship between Xe of Potassium atom and T is just Xe=B/T, where the slope B is approximately 283(K) as polar molecules, but appears to be disordered using the traditional capacitor. Its capacitance C at different voltage V was measured. The C-V curve shows that the saturation polarization of K vapor has be observed when E more than 105V/m and nearly all K atoms (over 98.9 per cent) are lined up with the field! The ground state neutra...

  6. 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.

  7. 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

  8. 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.

  9. Simultaneous Magneto-Optical Trapping of Fermionic 40K and Bosonic 87Rb Atoms

    Institute of Scientific and Technical Information of China (English)

    WEI Dong; XIONG De-Zhi; CHEN Hai-Xia; WANG Peng-Jun; GUO Lu; ZHANG Jing

    2007-01-01

    We report on simultaneous magneto-optical trapping of fermionic 40K and bosonic 87Rb atoms. This trap is the first step towards quantum degenerate fermi gas 40K. Laser lights for the two-species magneto-optical trap (MOT) are generated from diode lasers and tapered amplifier. The enriched 40K dispenser is utilized in the experimental setup. We obtain up to 107 ~108 40K and 108 ~109 87Rb atoms respectively in the steady-state single-species MOT.

  10. Decay widths and energy shifts of pi pi and pi K atoms

    OpenAIRE

    J. Schweizer

    2004-01-01

    We calculate the S-wave decay widths and energy shifts for pi pi and pi K atoms in the framework of QCD+QED. The evaluation - valid at next-to-leading order in isospin symmetry breaking - is performed within a non-relativistic effective field theory. The results are of interest for future hadronic atom experiments.

  11. 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.

  12. K shell X-ray fluorescence parameters of Co, Ni, Cu and Zn in phthalocyanine complexes

    Science.gov (United States)

    Doğan, M.; Cengiz, E.; Dilber, G.; Nas, A.; Tıraşoğlu, E.; Kantekin, H.

    2014-08-01

    The influence of the chemical effects on σ production cross-sections and Kβ/Kα intensity ratios of Co, Ni, Cu and Zn elements in the phthalocyanine complexes was investigated. The samples were excited by 59.5 keV γ-rays from an 241Am annular radioactive source. K X-rays emitted by the samples were counted by an Ultra-LEGe detector with a resolution of 150 eV at 5.9 keV. We observed the effects of different ligands on the σ production cross-sections and the Kβ/Kα intensity ratios. These effects were interpreted according to the charge transfer process from the central atoms to the ligands.

  13. 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.

  14. 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

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

    International Nuclear Information System (INIS)

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

  16. Ag K-shell ionization by electron impact: New cross-section measurements between 50 and 100 keV and review of previous experimental data

    Science.gov (United States)

    Vanin, V. R.; Manso Guevara, M. V.; Maidana, N. L.; Martins, M. N.; Fernández-Varea, J. M.

    2016-02-01

    We report the measurement of Ag K-shell ionization cross-section by electron impact in the range 50-100 keV and review the experimental data found in the literature. The sample consisted in a thin film of Ag evaporated on a thin C backing. The x-ray spectra generated by electron bombardment in the São Paulo Microtron were observed with a planar HPGe detector. The ratios between characteristic and bremsstrahlung x-ray yields were transformed to ionization cross sections with the help of theoretical atomic-field bremsstrahlung cross sections. The measured cross sections are compared with existing experimental values and calculations based on the semi-relativistic distorted-wave Born approximation. According to our experiment, the ratio of Ag Kβ to Kα x-ray intensities is 0.2018(24).

  17. Signatures of Quantum-Tunneling Diffusion of Hydrogen Atoms on Water Ice at 10 K.

    Science.gov (United States)

    Kuwahata, K; Hama, T; Kouchi, A; Watanabe, N

    2015-09-25

    Reported here is the first observation of the tunneling surface diffusion of a hydrogen (H) atom on water ice. Photostimulated desorption and resonance-enhanced multiphoton ionization methods were used to determine the diffusion rates at 10 K on amorphous solid water and polycrystalline ice. H-atom diffusion on polycrystalline ice was 2 orders of magnitude faster than that of deuterium atoms, indicating the occurrence of tunneling diffusion. Whether diffusion is by tunneling or thermal hopping also depends on the diffusion length of the atoms and the morphology of the surface. Our findings contribute to a better understanding of elementary physicochemical processes of hydrogen on cosmic ice dust. PMID:26451552

  18. Preliminary Measurement of the K-Shell Ionization Cross Sections of Ti by Positron Impact in the Low Energy Region

    Institute of Scientific and Technical Information of China (English)

    田丽霞; 刘慢天; 朱敬军; 安竹; 王宝义; 秦秀波

    2012-01-01

    Measurements were performed of K-shell ionization cross sections of Ti element by 10~30 keV positron impact using the thick-target method. The effects of multiple scattering of incident positron and from bremsstrahlung photons and annihilation photons with the thick-target method are discussed with the Monte Carlo code PENELOPE. Meanwhile, the Monte Carlo method is also applied to determine the detection efficiencies of X- and γ-ray detectors. Our experimental K-shell ionization cross sections for Ti element are compared with the distorted-wave Born approximation (DWBA) theoretical predictions, and it is found that the agreement of the experimental data and theoretical values is good and this indicates that the experimental method adopted in this study is applicable.

  19. Accelerated Thermalisation of 39K atoms in a Magnetic Trap with Superimposed Optical Potential

    CERN Document Server

    Nath, Dipankar; Rajalakshmi, G; Unnikrishnan, C S

    2013-01-01

    We report the rapid accelerated thermalisation of Potassium 39 K atoms loaded in a magnetic trap, in the presence of a single dipole trap beam. More than an order of magnitude reduction in the thermalisation time, to less than a second, is observed with the focused off- resonant beam occupying only 0.01% of the volume of the magnetic trap. The cold atoms are loaded from a Magneto-Optical Trap(MOT) of 39 K that has gone through a compressed MOT and sub-Doppler cooling stage. The atoms are prepared in the magnetically stretched |F = 2, mF = 2> state prior to loading into the hybrid trap. We also report a direct loading of 39 K atoms, prepared in the state |F = 1>, into a single beam dipole trap.

  20. Measurements of the Ground-State Polarizabilities of Cs, Rb, and K using Atom Interferometry

    CERN Document Server

    Gregoire, Maxwell D; Holmgren, William F; Trubko, Raisa; Cronin, Alexander D

    2015-01-01

    We measured the ground-state static electric-dipole polarizabilities of Cs, Rb, and K atoms using a three-nanograting Mach-Zehnder atom beam interferometer. Our measurements provide benchmark tests for atomic structure calculations and thus test the underlying theory used to interpret atomic parity non-conservation experiments. We measured $\\alpha_{\\mathrm{Cs}} = 4\\pi\\epsilon_0 \\times 59.45(11) \\AA^3$, $\\alpha_{\\mathrm{Rb}} = 4\\pi\\epsilon_0 \\times 47.44(9) \\AA^3$, and $\\alpha_{\\mathrm{K}} = 4\\pi\\epsilon_0 \\times 42.97(8) \\AA^3$. In atomic units, these measurements are $\\alpha_{\\mathrm{Cs}} = 401.2(7)$, $\\alpha_{\\mathrm{Rb}} = 320.1(6)$, and $\\alpha_{\\mathrm{K}} = 290.0(5)$. We report ratios of polarizabilities $\\alpha_{\\mathrm{Cs}}/\\alpha_{\\mathrm{Rb}} = 1.2532(10)$, $\\alpha_{\\mathrm{Cs}}/\\alpha_{\\mathrm{K}} = 1.3835(9)$, and $\\alpha_{\\mathrm{Rb}}/\\alpha_{\\mathrm{K}} = 1.1040(9)$ with smaller fractional uncertainty because the systematic errors for individual measurements are largely correlated. Since Cs atom...

  1. First-Principles Calculation of Principal Hugoniot and K-Shell X-ray Absorption Spectra for Warm Dense KCl

    OpenAIRE

    Zhao, Shijun; Zhang, Shen; Kang, Wei; Li, Zi; Zhang, Ping; He, Xian-Tu

    2015-01-01

    Principal Hugoniot and K-shell X-ray absorption spectra of warm dense KCl are calculated using the first-principles molecular dynamics method. Evolution of electronic structures as well as the influence of the approximate description of ionization on pressure (caused by the underestimation of the energy gap between conduction bands and valence bands) in the first-principles method are illustrated by the calculation. Pressure ionization and thermal smearing are shown as the major factors to pr...

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

    CERN Document Server

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

    2016-01-01

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

  3. Determination of K-shell absorption jump factors and jump ratios for La2O3, Ce and Gd using two different methods

    International Nuclear Information System (INIS)

    The K shell absorption jump factors and jump ratios for La2O3, Ce and Gd samples have been determined using the gamma or X-ray attenuation and EDXRF methods. It is the first time that the K shell absorption jump factor and jump ratio have been discussed for present elements using two different methods. To detect K X-rays, a high resolution Si(Li) detector was used. The experimental results of K shell absorption jump factors and jump ratios were compared with the theoretically calculated ones. - Highlights: • The K shell absorption jump factors and jump ratios were measured for La2O3, Ce and Gd. • These parameters were determined using two different methods. • The measured values of the parameters were found in good agreement with the theoretical ones

  4. 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.

  5. Quantum-interference-enhanced deep sub-Doppler cooling of 39K atoms in gray molasses

    Science.gov (United States)

    Nath, Dipankar; Easwaran, R. Kollengode; Rajalakshmi, G.; Unnikrishnan, C. S.

    2013-11-01

    We report enhanced sub-Doppler cooling of the bosonic atoms of 39K facilitated by formation of dark states with the cooling and repumping lasers tuned to the Raman resonance in Λ configuration near the D1 transition. A temperature of about 12 μK and phase-space density >2×10-5 is achieved in the two-stage D2-D1 molasses and spans a very large parameter region where quantum interference persists robustly. We also present results on enhanced radiation heating with a subnatural linewidth (0.07Γ) and a signature Fano-like profile of a coherently driven three-level atomic system. The optical Bloch equations relevant for the three-level atom in a bichromatic light field are solved with the method of continued fractions to show that cooling occurs only for a small velocity class of atoms, emphasizing the need for precooling in the D2 molasses stage.

  6. $K$-series X-rays yield measurement of kaonic hydrogen atoms in gaseous target

    CERN Document Server

    Bazzi, M; Bellotti, G; Berucci, C; Bragadireanu, A M; Bosnar, D; Cargnelli, M; Curceanu, C; Butt, A D; d'Uffizi, A; Fiorini, C; Ghio, F; Guaraldo, C; Hayanao, R S; Iliescu, M; Ishiwatari, T; Iwasaki, M; Sandri, P Levi; Marton, J; Okada, S; Pietreanu, D; Piscicchia, K; Vidal, A Romero; Sbardella, E; Scordo, A; Shi, H; Sirghi, D L; Sirghi, F; Tatsuno, H; Doce, O Vazquez; Widmann, E; Zmeskal, J

    2016-01-01

    We measured the $K$-series X-rays of the $K^{-}p$ exotic atom in the SIDDHARTA experiment with a gaseous hydrogen target of 1.3 g/l, which is about 15 times the $\\rho_{\\rm STP}$ of hydrogen gas. At this density, the absolute yields of kaonic X-rays, when a negatively charged kaon stopped inside the target, were determined to be 0.012$^{+0.004}_{-0.003}$ for $K_{\\alpha}$ and 0.043$^{+0.012}_{-0.011}$ for all the $K$-series transitions $K_{tot}$. These results, together with the KEK E228 experiment results, confirm for the first time a target density dependence of the yield predicted by the cascade models, and provide valuable information to refine the parameters used in the cascade models for the kaonic atoms.

  7. 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

  8. 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.

  9. 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)

  10. 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...

  11. Purification and functional analysis of a 40 kD protein extracted from the Strombus decorus persicus mollusk shells.

    Science.gov (United States)

    Pokroy, Boaz; Zolotoyabko, Emil; Adir, Noam

    2006-02-01

    A 40 kD protein has been extracted from the biomineral matrix of the calcium carbonate gastropod shell of Strombus decorus persicus. The protein was isolated by decalcification and ion exchange HPLC. We have named this protein ACLS40, i.e., aragonite crossed-lamellar structure protein. A partial sequence of the isolated ACLS40 and amino acid analysis both indicate that it does not belong to the family of very acidic proteins, i.e., rich in aspartic and glutamic residues. The shell-extracted protein shows the ability to stabilize calcium carbonate in vitro, in the form of thermodynamically unstable vaterite polymorph, and to inhibit the growth of calcite. PMID:16471929

  12. 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...

  13. Nuclear and Atomic Physics Invited Nuclear medium effects iu' K and R interactions

    International Nuclear Information System (INIS)

    Medium effects in the interaction of K and K' mesons with nucleons are reviewed. Recent K+ nuclear data confirm that conventional multiple scattering models fail to describe the interaction of K mesons for incoming momenta ρL = 400 - 800 MeV/c, suggesting a particular form of density dependence for the K nuclear optical potential. K+- atom strong-interaction data, fitted using a density dependent nuclear optical potential which respects the low-density theorem, require an appreciably stronger attraction than that obtained using a Vopt = tρ form, of order 180 +- 20 MeV at nuclear-matter density. The relationship of this result to the physics of theΛ(1405) KN unstable bound state is clarified, and the prospects of meeting the conditions for K- condensation in high-density matter are discussed

  14. 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

  15. 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.

  16. 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.

  17. 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

  18. 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)

  19. 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.

  20. K-shell ionisation in the positron decay branch 64Cu

    International Nuclear Information System (INIS)

    The inner-shell ionization accompanying positron emission is difficult to observe due to competition with electron capture (EC) and the attendant x-rays produced which are identical to those indicating ionization. It is necessary to use a coincidence arrangement to discriminate against EC. The present study used a triple coincidence between annihilation quanta and x-rays to gate the output of a high resolution Si(L) detector

  1. Bonding of an Isolated K atom to a Surface : Experiment and Theory

    NARCIS (Netherlands)

    Sandell, A.; Hjortstam, O.; Nilsson, A.; Brühwiler, P.A.; Eriksson, O.; Bennich, P.; Rudolf, P.; Wills, J.M.; Johansson, B.; Mårtensson, N.

    1997-01-01

    We present a new and general technique with which the local properties of the unoccupied states of an adsorbed alkali atom in the low coverage limit can be studied. The method, based on a combination of experimental core level spectroscopy data and calculations, is demonstrated for the K/graphite sy

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

    International Nuclear Information System (INIS)

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

  3. 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 ...

  4. 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

  5. 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 .

  6. Quantum interference-enhanced deep sub-Doppler cooling of 39 K atoms beyond gray molasses

    CERN Document Server

    Nath, Dipankar; Rajalakshmi, G; Unnikrishnan, C S

    2013-01-01

    We report enhanced sub-Doppler cooling of the bosonic atoms of 39 K facilitated by formation of dark states due to the quantum interference of excitation amplitudes in the Raman configuration for the cooling and repumping lasers tuned around the D1 resonance. The temperature of about 12 {\\mu}K achieved in the two stage D2-D1 molasses is the lowest ever reported for 39 K and spans a very large parameter region where quantum interference persists robustly. We also present results on enhanced radiation heating with sub-natural linewidth (0.1{\\Gamma}) and Fano like profile, following the quantum features of 3-level coherently driven atomic system with complexities associated with optical pumping to dark states and Sisyphus effect in standing wave light fields, over and above the Raman quantum interference.

  7. Atomic Decay Data for Modeling K Lines of Iron Peak and Light Odd-Z Elements*

    Science.gov (United States)

    Palmeri, P.; Quinet, P.; Mendoza, C.; Bautista, M. A.; Garcia, J.; Witthoeft, M. C.; Kallman, T. R.

    2012-01-01

    Complete data sets of level energies, transition wavelengths, A-values, radiative and Auger widths and fluorescence yields for K-vacancy levels of the F, Na, P, Cl, K, Sc, Ti, V, Cr, Mn, Co, Cu and Zn isonuclear sequences have been computed by a Hartree-Fock method that includes relativistic corrections as implemented in Cowan's atomic structure computer suite. The atomic parameters for more than 3 million fine-structure K lines have been determined. Ions with electron number N greater than 9 are treated for the first time, and detailed comparisons with available measurements and theoretical data for ions with N less than or equal to 9 are carried out in order to estimate reliable accuracy ratings.

  8. 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.

  9. 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.

  10. 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

  11. First-principles calculation of principal Hugoniot and K-shell X-ray absorption spectra for warm dense KCl

    International Nuclear Information System (INIS)

    Principal Hugoniot and K-shell X-ray absorption spectra of warm dense KCl are calculated using the first-principles molecular dynamics (FPMD) method. Evolution of electronic structures as well as the influence of the approximate description of ionization on pressure (caused by the underestimation of the energy gap between conduction bands and valence bands) in the first-principles method are illustrated by the calculation. It is shown that approximate description of ionization in FPMD has small influence on Hugoniot pressure due to mutual compensation of electronic kinetic pressure and virial pressure. The calculation of X-ray absorption spectra shows that the band gap of KCl persists after the pressure ionization of the 3p electrons of Cl and K taking place at lower energy, which provides a detailed understanding to the evolution of electronic structures of warm dense matter

  12. First-Principles Calculation of Principal Hugoniot and K-Shell X-ray Absorption Spectra for Warm Dense KCl

    CERN Document Server

    Zhao, Shijun; Kang, Wei; Li, Zi; Zhang, Ping; He, Xian-Tu

    2015-01-01

    Principal Hugoniot and K-shell X-ray absorption spectra of warm dense KCl are calculated using the first-principles molecular dynamics method. Evolution of electronic structures as well as the influence of the approximate description of ionization on pressure (caused by the underestimation of the energy gap between conduction bands and valence bands) in the first-principles method are illustrated by the calculation. Pressure ionization and thermal smearing are shown as the major factors to prevent the deviation of pressure from global accumulation along the Hugoniot. In addition, cancellation between electronic kinetic pressure and virial pressure further reduces the deviation. The calculation of X-ray absorption spectra shows that the band gap of KCl persists after the pressure ionization of the $3p$ electrons of Cl and K taking place at lower energy, which provides a detailed understanding to the evolution of electronic structures of warm dense matter.

  13. First-principles calculation of principal Hugoniot and K-shell X-ray absorption spectra for warm dense KCl

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Shijun; Zhang, Shen; Kang, Wei, E-mail: weikang@pku.edu.cn [HEDPS, Center for Applied Physics and Technology, Peking University, Beijing 100871 (China); College of Engineering, Peking University, Beijing 100871 (China); Li, Zi [Institute of Applied Physics and Computational Mathematics, Beijing 100088 (China); Zhang, Ping [HEDPS, Center for Applied Physics and Technology, Peking University, Beijing 100871 (China); Institute of Applied Physics and Computational Mathematics, Beijing 100088 (China); He, Xian-Tu, E-mail: xthe@iapcm.ac.cn [HEDPS, Center for Applied Physics and Technology, Peking University, Beijing 100871 (China); College of Engineering, Peking University, Beijing 100871 (China); Institute of Applied Physics and Computational Mathematics, Beijing 100088 (China)

    2015-06-15

    Principal Hugoniot and K-shell X-ray absorption spectra of warm dense KCl are calculated using the first-principles molecular dynamics (FPMD) method. Evolution of electronic structures as well as the influence of the approximate description of ionization on pressure (caused by the underestimation of the energy gap between conduction bands and valence bands) in the first-principles method are illustrated by the calculation. It is shown that approximate description of ionization in FPMD has small influence on Hugoniot pressure due to mutual compensation of electronic kinetic pressure and virial pressure. The calculation of X-ray absorption spectra shows that the band gap of KCl persists after the pressure ionization of the 3p electrons of Cl and K taking place at lower energy, which provides a detailed understanding to the evolution of electronic structures of warm dense matter.

  14. 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 .

  15. 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.

  16. K-LL Auger transition probabilities for elements with low and intermediate atomic numbers

    Science.gov (United States)

    Chen, M. H.; Crasemann, B.

    1973-01-01

    Radiationless K-LL transition probabilities have been calculated nonrelativistically in j-j coupling and in intermediate coupling, without and with configuration interaction, for elements with atomic numbers from 13 to 47. The system is treated as a coupled two-hole configuration. The single-particle radial wave functions required in the calculation of radial matrix elements, and in the calculation of mixing coefficients in the intermediate-coupling scheme, were obtained from Green's atomic independent-particle model. Comparison with previous theoretical work and with experimental data is made. The effects of intermediate coupling, configuration interaction, and relativity are noted.

  17. Sub-Doppler laser cooling of fermionic 40K atoms in three-dimensional gray optical molasses

    Science.gov (United States)

    Rio Fernandes, D.; Sievers, F.; Kretzschmar, N.; Wu, S.; Salomon, C.; Chevy, F.

    2012-12-01

    We demonstrate sub-Doppler cooling of 40K on the D1 atomic transition. Using a gray-molasses scheme, we efficiently cool a compressed cloud of 6.5 × 108 atoms from ˜4 mK to 20 μK in 8 ms. After transfer to a quadrupole magnetic trap, we measure a phase space density of ˜10-5. This technique offers a promising route for fast evaporation of fermionic 40K.

  18. Sub-Doppler laser cooling of fermionic 40K atoms in three-dimensional gray optical molasses

    OpenAIRE

    Rio Fernandes, Diogo; Sievers, Franz; Kretzschmar, Norman; Wu, Saijun; Salomon, C; Chevy, Frédéric

    2012-01-01

    We demonstrate sub-Doppler cooling of 40K on the D_1 atomic transition. Using a gray molasses scheme, we efficiently cool a compressed cloud of 6.5x10^8 atoms from ~ 4\\mK to 20uK in 8 ms. After transfer in a quadrupole magnetic trap, we measure a phase space density of ~10^-5. This technique offers a promising route for fast evaporation of fermionic 40K.

  19. Rotation Measurement with a K-Rb-21Ne Atomic Spin Co-magnetometer Gyroscope

    Science.gov (United States)

    Chen, Yao; Zou, Sheng; Duan, Lihong; Fang, Jiancheng

    2014-05-01

    Co-magnetometers based on K-3He and K-Rb-21Ne have been used to test of CPT symmetry. For the K- Rb-21Ne co-magnetometer, due to the gyroscopic effect of the 21Ne nuclear spin, it can also be used to sense small rotation. For inertial navigation application, 21Ne atoms, whose gyromagnetic ratio is an order of smaller than 3He, is better to be used to sense rotation. The spin projection noise of a K-Rb-21Ne co-magnetometer with measurement volume of 1cm3 could be on the order of 10-10 rad/s/Hz1/2. A K-Rb-21Ne co-magnetometer gyroscope has been designed. It is under constructing in our laboratory and the rotation of the earth should be measured by this apparatus. We also have made alkali vapor cells filled with K and Rb atoms, whose mole fraction ratio is controlled by analytical balance operated in the anaerobic glove box. This work was supported by Key Programs of National Science Foundation of China under Grant No. 61227902 and 61374210.

  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. Probing the N = 32 shell closure below the magic proton number Z = 20: Mass measurements of the exotic isotopes 52,53K

    CERN Document Server

    Rosenbusch, M; Atanasov, D; Barbieri, C; Beck, D; Blaum, K; Borgmann, Ch; Breitenfeldt, M; Cakirli, R B; Cipollone, A; George, S; Herfurth, F; Kowalska, M; Kreim, S; Lunney, D; Manea, V; Navrátil, P; Neidherr, D; Schweikhard, L; Somà, V; Stanja, J; Wienholtz, F; Wolf, R N; Zuber, K

    2015-01-01

    The recently confirmed neutron-shell closure at N = 32 has been investigated for the first time below the magic proton number Z = 20 with mass measurements of the exotic isotopes 52,53K, the latter being the shortest-lived nuclide investigated at the online mass spectrometer ISOLTRAP. The resulting two-neutron separation energies reveal a 3 MeV shell gap at N = 32, slightly lower than for 52Ca, highlighting the doubly-magic nature of this nuclide. Skyrme-Hartree-Fock-Boguliubov and ab initio Gorkov-Green function calculations are challenged by the new measurements but reproduce qualitatively the observed shell effect.

  2. Brief Announcement: Anonymous Obstruction-free (n, k)-Set Agreement with n−k+1 Atomic Read/Write Registers

    OpenAIRE

    Bouzid, Zohir; Raynal, Michel; Sutra, Pierre

    2015-01-01

    This paper presents an obstruction-free solution to the (n,k)-set agreement problem in an asynchronous anonymous read/write system using solely (n − k + 1) registers. We then extend this algorithm into (i) a space-optimal solution for the repeated version of (n, k)-set agreement, and (ii) an x-obstruction- free solution using (n − k + x) atomic registers (with 1 ≤ x ≤ k < n).

  3. 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.

  4. Quantum Degenerate Fermi-Bose Mixtures of 40K and 87Rb Atoms in a Quadrupole-Ioffe Configuration Trap

    Institute of Scientific and Technical Information of China (English)

    XIONG De-Zhi; CHEN Hai-Xia; WANG Peng-Jun; YU Xu-Dong; GAO Feng; ZHANG Jing

    2008-01-01

    @@ We report on the attainment of quantum degeneracy of 40K by means of efficient thermal collisions with the evaporatively cooled 87Rb atoms.In a quadrupole-Ioffe configuration trap,potassium atoms are cooled to 0.5 times the Fermi temperature.We obtain up to 7.59 × 105 degenerate fermions 40K.

  5. 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:

  6. K vacancy production in collisions of 63 MeV Cu ions with Ge and Ag atoms

    International Nuclear Information System (INIS)

    The mechanism of K-shell vacancy production is studied in t in an X-ray-scattered ion coincidence experiment with 1 MeV/a.m.u. 63Cu4+ ion incident onto natural Ge and Ag targets. The impact parameter dependent K-shell vacancy production probability measured in the experiment is interpreted in terms of the rotational coupling and the statistical models. The dependence of the vacancy sharing process in the Cu-Ge collision system on the impact parameter is obtained and compared with the predictions of the Briggs-Myerhof-Demkov model

  7. K-Vacancy Production in the Collision of Highly Charged Relativistic Ions With Heavy Atoms

    OpenAIRE

    Khabibullaev, P. K.

    2000-01-01

    A general expression for the cross section of the inelastic collision of relativistic highly charged ion with heavy (relativistic) atoms is obtained using the generalized eikonal approximation. In the ultrarelativistic limit, the obtained formula coincides with a known exact one. As an application of the obtained result, probability and cross section of the K-vacany production in the U92+ - U91+ collision are calculated.

  8. 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.

  9. Coordination-resolved local bond strain and 3p energy entrapment of K atomic clusters and K(1 1 0) skin

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • Coordination environment resolves electron binding-energy shift of K44, K46, K55 clusters. • Predict the effective coordination number of K nanoclusters when we get the atomic number N. • Atomic under coordination shortens the local bonds and entrapment. • XPS derives core level of an isolated atom and its bulk shift. - Abstract: We have examined the atomic coordination effect on the local bond strain and the 3p core-level shift of K(1 1 0) skin and nanoclusters using a combination of the bond order–length–strength correlation notion, tight-binding approach, density functional theory calculations, and photoelectron spectroscopy measurements. It turns out that: (i) the 3p core-level shifts from 15.595 ± 0.003 eV for an isolated K atom by 2.758 eV to the bulk value of 18.353 eV; (ii) the effective atomic coordination number reduces from the bulk value of 12 to 3.93 for the first layer and to 5.81 for the second layer of K(1 1 0) skin associated with the local lattice strain of 12.76%, a binding energy density 72.67%, and atomic cohesive energy −62.46% for the skin; and (iii) K cluster size reduction lowers the effective atomic coordination number and enhances further the skin electronic attribution. Results have revealed that the 3p core-level shifts of K(1 1 0) and nanoclusters originate from perturbation of the Hamiltonian by under-coordination induced charge densification and quantum entrapment

  10. Coordination-resolved local bond strain and 3p energy entrapment of K atomic clusters and K(1 1 0) skin

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Ting; Bo, Maolin; Guo, Yongling [Key Laboratory of Low-Dimensional Materials and Application Technologies (Ministry of Education), Faculty of Materials Science and Engineering, Xiangtan University, Hunan 411105 (China); Hunan Provincial Key Laboratory of Thin Film Materials and Devices, Faculty of Materials Science and Engineering, Xiangtan University, Hunan 411105 (China); Chen, Hefeng [United Superconductive Institution, Shanghai Jiaotong University, Shanghai 200240 (China); Wang, Yan [School of Information and Electronic Engineering, Hunan University of Science and Technology, Hunan 411201 (China); Huang, Yongli, E-mail: huangyongli@xtu.edu.cn [Key Laboratory of Low-Dimensional Materials and Application Technologies (Ministry of Education), Faculty of Materials Science and Engineering, Xiangtan University, Hunan 411105 (China); Hunan Provincial Key Laboratory of Thin Film Materials and Devices, Faculty of Materials Science and Engineering, Xiangtan University, Hunan 411105 (China); Sun, Chang Q., E-mail: ecqsun@ntu.edu.sg [Key Laboratory of Low-Dimensional Materials and Application Technologies (Ministry of Education), Faculty of Materials Science and Engineering, Xiangtan University, Hunan 411105 (China); Hunan Provincial Key Laboratory of Thin Film Materials and Devices, Faculty of Materials Science and Engineering, Xiangtan University, Hunan 411105 (China); School of Information and Electronic Engineering, Hunan University of Science and Technology, Hunan 411201 (China); NOVITAS, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798 (Singapore)

    2015-09-15

    Graphical abstract: - Highlights: • Coordination environment resolves electron binding-energy shift of K{sub 44}, K{sub 46}, K{sub 55} clusters. • Predict the effective coordination number of K nanoclusters when we get the atomic number N. • Atomic under coordination shortens the local bonds and entrapment. • XPS derives core level of an isolated atom and its bulk shift. - Abstract: We have examined the atomic coordination effect on the local bond strain and the 3p core-level shift of K(1 1 0) skin and nanoclusters using a combination of the bond order–length–strength correlation notion, tight-binding approach, density functional theory calculations, and photoelectron spectroscopy measurements. It turns out that: (i) the 3p core-level shifts from 15.595 ± 0.003 eV for an isolated K atom by 2.758 eV to the bulk value of 18.353 eV; (ii) the effective atomic coordination number reduces from the bulk value of 12 to 3.93 for the first layer and to 5.81 for the second layer of K(1 1 0) skin associated with the local lattice strain of 12.76%, a binding energy density 72.67%, and atomic cohesive energy −62.46% for the skin; and (iii) K cluster size reduction lowers the effective atomic coordination number and enhances further the skin electronic attribution. Results have revealed that the 3p core-level shifts of K(1 1 0) and nanoclusters originate from perturbation of the Hamiltonian by under-coordination induced charge densification and quantum entrapment.

  11. Measurements of K-shell ionization cross-sections of S, Ca and Zn by 7-30 keV electron impact

    International Nuclear Information System (INIS)

    The absolute K-shell ionization cross-sections of S, Ca and Zn by 7-30 keV electron impact have been measured. The targets were prepared by evaporating the compounds ZnS and CaF2 to the thick pure carbon substrates. The effects of multiple scattering of electrons penetrating the target films, electrons reflected from the thick pure carbon substrates and Bremsstrahlung photons produced when incident electrons impacted on the targets are corrected by using Monte Carlo method. The uncertainties of our measured K-shell ionization cross-sections are, respectively, ∼13% for S, ∼15% for Ca and ∼12% for Zn. The experimental results were compared with some theoretical results and available experimental data from the literature. The experimental data for S K-shell ionization cross-sections by 7-30 keV electron impact are given here for the first time.

  12. Cross sections of K-shell ionization by electron impact, measured from threshold to 100 keV, for Au and Bi

    International Nuclear Information System (INIS)

    We have measured cross sections for the ionization of the K shell by electrons with energies from the respective thresholds up to 100 keV, for Au and Bi. The experimental values are obtained by dividing the number of counts in the Kα peak by the number of counts in an energy interval near the tip of the bremsstrahlung continuum, and multiplying this ratio by the theoretical estimate of bremsstrahlung emission towards the detector in this energy interval. Although such a procedure has already been described in the literature, here it is implemented avoiding some of the simplifications made in earlier works. Our experimental cross sections, which are the first ones to be reported for atoms with Z>47 close to the threshold, are in reasonable agreement with the theoretical predictions of the semirelativistic distorted-wave Born approximation. Hippler's plane-wave Born approximation with corrections for Coulomb and exchange effects yields cross sections that are closer to the experimental data than those evaluated from the relativistic binary-encounter-Bethe model. (paper)

  13. Low-energy total K-shell ionisation cross sections in the plane-wave Born approximation: an analytical result

    International Nuclear Information System (INIS)

    Starting from the general formulation of the plane-wave Born approximation (PWBA) an analytical expression for the low-energy total K-shell ionisation cross section is obtained. The reduced cross section is given as a power series in the adimensional parameters xi2 and theta which reproduces the values obtained by numerical integration within the precision inherent in the available tables. The universal part of the reduced cross section in the PWBA (that part of F(xi2,theta) that does not depend explicitly on theta) is expressed in terms of a few elementary analytical functions. The exact physical limits of integration are taken into account through the introduction of an effective parameter xisub(eff). (author)

  14. Calculation of K Shell Intensity Ratios and Line Widths of Ti and some of its compounds by means of 5,96 keV energy

    Science.gov (United States)

    Kağan Köksal, Oğuz; Apaydın, Gökhan; Cengiz, Erhan; Karabulut, Kazım

    2016-04-01

    K shell intensity ratios and Line Widths of pure Ti and some of its compounds have been determined experimentally using an Ultra-LEGe detector with resolution 140 eV at 5.9 keV. The samples were excited 5.96 keV photons emitted from a 55Fe radioisotope source with 50 mCi activity. The experimental values of the K shell intensity ratios have been compared with the experimental and theoretical values available in the literature for pure Ti and line widths have been only compared with a theoretical value for pure Ti.

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

    Institute of Scientific and Technical Information of China (English)

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

    2007-01-01

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

  16. An extremely important discovery-the centre of the electron cloud of K atom does not coincide with the nucleus

    CERN Document Server

    You, Pei-Lin

    2009-01-01

    It is a general point of view that in the absence of an external field, the nucleus of an atom is at the centre of the electron cloud, so that all kinds of atoms do not have permanent electric dipole moment(EDM). In the fact, the idea is untested. Using two special capacitors containing Potassium vapor we discovered that the electric susceptibility Xe of K atoms is directly proportional to the density N, and inversely to the temperature T, as polar molecules. The experimental K material is supplied by Strem Chemicals Co. USA. We have distinguished between permanent and induced dipole moments carefully. There is good evidence that a ground state neutral K atom has a large permanent EDM, d(K)=2.53*10-29C.m, while d(H2O)=0.62 *10-29C.m for water molecule. New example of time-reversal violation occurred in K atoms. Why the linear Stark effect of K atoms has not been observed? The article discussed the question thoroughly. The linear Stark shift of K atoms is only 0.0041nm. It is so small, in fact, that a direct o...

  17. Observation on radiation transfer experiments using k-shell absorption spectra

    International Nuclear Information System (INIS)

    Recent laser-produced plasma experiments have relied on spectroscopic comparisons with models to infer plasma temperatures. Here, the technique is applied to study thermal radiation transfer experiments. The transmission model combines high-quality atomic data with an ionization balance obtained from systematic expansions of the grand canonical ensemble. The latter avoids the ad hoc cutoffs required in free energy minimization schemes and includes Coulomb corrections usually neglected in other models. It is shown that the improved equation of state significantly affects inferred temperatures at the higher densities expected in the heat flow experiments. Even though good agreement is obtained between the experimental and theoretical transmission spectrum, the experimental uncertainties are sufficiently large that is compromises the intended bench marking of the thermal transport models

  18. The estimation of production rates of {\\pi }^{+}{K}^{-}, {\\pi }^{-}{K}^{+} and {\\pi }^{+}{\\pi }^{-} atoms in proton–nucleus interactions at 450 GeV c–1

    Science.gov (United States)

    Gorchakov, O. E.; Nemenov, L. L.

    2016-09-01

    Short-lived (τ ∼ 3× {10}-15 s) {π }+{K}-, {K}+{π }- and {π }+{π }- atoms as well as long-lived (τ ≥slant 1× {10}-11 s) {π }+{π }- atoms produced in proton–nucleus interactions at 24 GeV c–1 are observed and studied in the DIRAC experiment at the CERN Proton Synchroton. The purpose of this paper is to show that the yields of the short-lived {π }+{K}-, {K}+{π }- and {π }+{π }- atoms in proton–nucleus interactions at 450 GeV c–1 and {θ }{{lab}}=4^\\circ are estimated to be, respectively 67 ± 13, 31 ± 6 and 15 ± 2 times higher. This may allow a significant improvement of the precision of their lifetime measurement and π π and π K scattering length combinations | {a}0-{a}2| and | {a}1/2-{a}3/2| . The yields of the long-lived {π }+{K}-, {K}+{π }- and {π }+{π }- atoms at 450 GeV c–1 are estimated to be 265 ± 53, 120 ± 24 and 60 ± 9 times higher per time unit than at 24 GeV c–1. This may allow the resonance method to be used for measuring the Lamb shift in the π π atom and a new π π scattering length combination 2{a}0+{a}2 to be obtained.

  19. 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)

  20. 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.

  1. Valence-shell single photoionization of Chlorine-like K$^{2+}$ ions: Experiment and Theory

    CERN Document Server

    Alna'Washi, G A; Habibi, M; Esteves-Macaluso, D; Wang, J C; Phaneuf, R A; Kilcoyne, A L D; Cisneros, C; McLaughlin, B M

    2014-01-01

    The absolute single photoionization cross-section was measured for Cl-like K$^{2+}$ over the photon energy range from 44.2 - 69.7 eV at a constant energy resolution of 0.045 eV. The experiments were performed by merging an ion beam with a beam of synchrotron radiation from an undulator. The ground-state ionization threshold was measured at 0.004 eV energy resolution to be 45.717 $\\pm$ 0.030 eV. The measurements are rich in resonance structure due to multiple Rydberg series of transitions to autoionizing states. These series are assigned spectroscopically using the quantum defect method, guided by pseudo-relativistic Hartree-Fock calculations for the energies and oscillator strengths of transitions to autoionizing states. The experimental results, which include significant contributions from K$^{2+}$ ions initially in metastable states, are in satisfactory agreement with a linear superposition of semi-relativistic R-matrix calculations of photoionization cross sections from these initial states.

  2. Experiments with a Gas-Puff-On-Wire-Array Load on the GIT-12 Generator for Al K-shell Radiation Production at Microsecond Implosion Times

    Science.gov (United States)

    Shishlov, Alexander V.; Baksht, Rina B.; Chaikovsky, Stanislav A.; Fedunin, Anatoly V.; Fursov, Fedor I.; Kovalchuk, Boris M.; Kokshenev, Vladimir A.; Kurmaev, Nikolai E.; Labetsky, Aleksey Yu.; Oreshkin, Vladimir I.; Rousskikh, Alexander G.; Lassalle, Francis; Bayol, Frederic

    2006-01-01

    Results of the experiments carried out on the GIT-12 generator at the current level of 3.5 MA and the Z-pinch implosion times from 700 ns to 1.1 μs are presented. A multi-shell (triple-shell) load configuration with the outer gas puffs (neon) and the inner wire array (aluminum) was used in the experiments. In the course of the research, implosion dynamics of the triple-shell z-pinch was studied, and the radiation yield in the spectral range of neon and aluminum K-lines have been measured. Optimization of the inner wire array parameters aimed at obtaining the maximum aluminum K-shell radiation yield has been carried out. As a result of optimization of the gas-puff-on-wire-array Z-pinch load, the aluminum K-shell radiation yield (hv> 1.55 keV) up to 4 kJ/cm in the radiation pulse with FWHM less than 30 ns has been obtained. Comparison of the experimental results with the results of preliminary 1D RMHD simulations allows a conclusion that at least 2/3 of the generator current is switched from a gas puff to an aluminum wire array. The radiation yield in the spectral range of neon K-lines (0.92-1.55 keV) increases considerably in the shots with the inner wire array in comparison with the shots carried out with the outer gas puffs only. The radiation yield in the spectral range above 1 keV registered in the experiments reached 10 kJ/cm. The presence of a high portion of the neon plasma inside an inner wire array can limit the radiation yield in the spectral range above 1.55 keV.

  3. Construction of embedded-atom-method interatomic potentials for alkaline metals (Li, Na, and K) by lattice inversion

    International Nuclear Information System (INIS)

    The lattice-inversion embedded-atom-method interatomic potential developed previously by us is extended to alkaline metals including Li, Na, and K. It is found that considering interatomic interactions between neighboring atoms of an appropriate distance is a matter of great significance in constructing accurate embedded-atom-method interatomic potentials, especially for the prediction of surface energy. The lattice-inversion embedded-atom-method interatomic potentials for Li, Na, and K are successfully constructed by taking the fourth-neighbor atoms into consideration. These angular-independent potentials markedly promote the accuracy of predicted surface energies, which agree well with experimental results. In addition, the predicted structural stability, elastic constants, formation and migration energies of vacancy, and activation energy of vacancy diffusion are in good agreement with available experimental data and first-principles calculations, and the equilibrium condition is satisfied. (atomic and molecular physics)

  4. 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

  5. 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)

  6. Interaction of antiprotons with Rb atoms and a comparison of antiproton stopping powers of the atoms H, Li, Na, K, and Rb

    DEFF Research Database (Denmark)

    Lühr, Armin Christian; Fischer, Nicolas; Saenz, Alejandro

    Ionization and excitation cross sections as well as electron-energy spectra and stopping powers of the alkali metal atoms Li, Na, K, and Rb colliding with antiprotons were calculated using a time-dependent channel-coupling approach. An impact-energy range from 0.25 to 4000 keV was considered. The...... target atoms are treated as effective one-electron systems using a model potential. The results are compared with calculated cross sections for antiproton-hydrogen atom collisions....

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

    International Nuclear Information System (INIS)

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

  8. Soft-photon emission in extreme-relativistic Compton scattering by K-shell electrons and connection to photoeffect

    CERN Document Server

    Florescu, V

    2000-01-01

    We have recently obtained cross-sections for Compton scattering by K-shell electrons at extreme-relativistic (ER) energies of the incoming photon. Our method is essentially analytical, and only at the end did it require a modest numerical computation. The results are valid for the Compton line of the scattered photon spectrum, but do not cover the infrared divergence at the soft-photon end of the spectrum. This case is treated in the present paper. The method we apply here is an adaptation of the one used for the Compton line. This allows us to make use of many previous results. The quadruply and doubly differential Compton cross-sections can be expressed in analytical forms which allow factorization of the ER photoeffect cross-sections (differential or total, respectively). This result is shown to be a manifestation of the soft-photon theorem connecting the Compton matrix element at low emitted photon frequencies to that of the photoeffect. The computation of ER Compton cross-sections with soft-photon emissi...

  9. Kinetics and mechanism of the gas-phase reaction of Cl atoms and OH radicals with fluorobenzene at 296 K

    DEFF Research Database (Denmark)

    Andersen, Mads Peter Sulbæk; Nielsen, Ole John; Hurley, MD;

    2002-01-01

    radical and adduct formation to give the C6H5F-Cl adduct. At 296 K the rate constant for the abstraction channel is k(5a)(Cl+C6H5F) = (1.1 +/- 0.1) x 10(-17) cm(3) molecule(-1) s(-1). The C6H5F-Cl adduct undergoes rapid (k similar to 10(8) s(-1)) decomposition to reform C6H5F and Cl atoms and reaction......Smog chamber/FTIR techniques were used to study the kinetics and mechanism of the reaction of Cl atoms and OH radicals with fluorobenzene, C6H5F, in 700 Torr of N-2 or air diluent at 296 K. Reaction of Cl atoms with C6H5F proceeds via two pathways: H-atom abstraction to give HCl and the C6H4F...... with Cl atoms via a mechanism which, at least in part, leads neither to production of C6H5Cl nor to reformation of C6H5F. As the steady-state Cl atom concentration is increased, the fraction of the C6H5F-Cl adduct undergoing reaction with Cl atoms increases causing an increase in the effective rate...

  10. The energy dependence of selective hydrogen atom abstraction by H(D) atoms in the photolysis of neopentane - ethane mixtures at 77 K

    International Nuclear Information System (INIS)

    Selective hydrogen - atom - abstraction reaction by H or D atom has been studied in a neo C5H12 - C2H6 (less than 1 mol %) mixture at 77 K by ESR spectroscopy. The H (or D) atom produced by the photolysis of HI (or DI) reacts with neo - C2H12 and C2H6 to form neo - C5H11 and C2H5 radicals. In order to obtain H atoms with different kinetic energies, the photolysis was performed with different lights of 313, 254 and 229 nm. The selective formation of the C2H5 radical by the reaction of the H (or D) atom with C2H6 becomes more effective with the decrease in the energy of the H (or D) atom. The formation of the neo - C5H11 radical by the reaction of the H (or D) atom with neo - C2H12 becomes more effective with the increase in the energy of the H (or D) atom. (A.R.H.)

  11. Construction of embedded-atom-method interatomic potentials for alkaline metals (Li, Na, and K) by lattice inversion

    Institute of Scientific and Technical Information of China (English)

    Yuan Xiao-Jian; Chen Nan-Xian; Shen Jiang

    2012-01-01

    The lattice-inversion embedded-atom-method interatomic potential developed previously by us is extended to alkaline metals including Li,Na,and K.It is found that considering interatomic interactions between neighboring atoms of an appropriate distance is a matter of great significance in constructing accurate embedded-atom-method interatomic potentials,especially for the prediction of surface energy.The lattice-inversion embedded-atom-method interatomic potentials for Li,Na,and K are successfully constructed by taking the fourth-neighbor atoms into consideration.These angular-independent potentials markedly promote the accuracy of predicted surface energies,which agree well with experimental results.In addition,the predicted structural stability,elastic constants,formation and migration energies of vacancy,and activation energy of vacancy diffusion are in good agreement with available experimental data and first-principles calculations,and the equilibrium condition is satisfied.

  12. Production of graphitic carbon-based nanocomposites from K2CO3-activated coconut shells as counter electrodes for dye-sensitized solar-cell applications

    Science.gov (United States)

    Loryuenyong, Vorrada; Buasri, Achanai; Lerdvilainarit, Parichat; Manachevakulm, Konnatee; Sompong, Siripond

    2016-01-01

    In this study, graphitic carbon-activated carbon nanocomposites fabricated from K2CO3 chemically-activated coconut shells by using Fe-catalytic chemical vapor deposition are reported. The present method was simple, environmentally-friendly, low cost, but successfully offered graphitic carbon-based materials that demonstrated promise for use as counter electrodes in dye-sensitized solar cells. The results showed that the coconut shell:catalyst ratio (1:0, 1:4, 1:1, and 4:1) significantly affected the structural, physical and electrochemical properties of the samples. Graphitic carbon and activated carbon nanocomposites with a high specific surface area of 1230 m2/g and high electrochemical activity in iodide reduction are obtained for samples with a coconut shells/iron precursor (Fe(NO3)3) ratio of 4:1.

  13. Microwave plasma atomic emission spectrometric determination of Ca, K and Mg in various cheese varieties.

    Science.gov (United States)

    Ozbek, Nil; Akman, Suleyman

    2016-02-01

    Microwave plasma-atomic emission spectrometry (MP-AES) was used to determine calcium, magnesium and potassium in various Turkish cheese samples. Cheese samples were dried at 100 °C for 2 days and then digested in a mixture of nitric acid/hydrogen peroxide (3:1). Good linearities (R(2) > 0.999) were obtained up to 10 μg mL(-1) of Ca, Mg and K at 445.478 nm, 285.213 nm and 766.491 nm, respectively. The analytes in a certified reference milk powder sample were determined within the uncertainty limits. Moreover, the analytes added to the cheese samples were recovered quantitatively (>90%). All determinations were performed using aqueous standards for calibration. The LOD values for Ca, Mg and K were 0.036 μg mL(-1), 0.012 μg mL(-1) and 0.190 μg mL(-1), respectively. Concentrations of Ca, K and Mg in various types of cheese samples produced in different regions of Turkey were found between 1.03-3.70, 0.242-0.784 and 0.081-0.303 g kg(-1), respectively. PMID:26304350

  14. 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)

  15. 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

  16. 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)

  17. Fermi-Bose mixtures of 40K and 87Rb atoms

    International Nuclear Information System (INIS)

    After the recent realization of the BCS-BEC crossover in dilute atomic Fermi gases, quantum degenerate mixtures of bosonic and fermionic atoms are expected to provide a complementary approach to fermionic super fluidity where the attractive interaction between Fermions is mediated by the inter species interaction, a situation which is in many ways analogous to phonon-mediated Cooper pairing in superconductors. Moreover, these mixtures are expected to show a rich phase diagram when loaded into an optical lattice, with various pairing phases involving one or several fermionic and bosonic atoms. Already in a harmonic trap, these mixtures show a rich class of phenomena. The behaviour of the mixture is influenced by a lot of properties: mean ld interaction both between Fermions and Bosons as well as the mean field interaction in the condensate. Depending on the sign of the Fermi-Bose interaction, phase separation or mean ld trapping and collapse of the mixture are expected. The mass ratio between Fermions and Bosons will also influence the ratio of trapping frequencies between the two species. Three-body loss processes can have a dramatic impact on lifetime and dynamical behaviour of the mixture. The condensate overlapping only with a small part of the Fermi sea will introduce localized trapping and loss processes. We report on the production of a quantum degenerate Fermi-Bose mixture of 40K and 87Rb in a regime of large particle numbers. In the experiment, we can span a wide range of phenomena starting at small particle numbers, where the expansion of the bosonic and the fermionic component are well described by the respective single-component Thomas-Fermi profiles. As particle numbers and densities in the mixture increase, the mean field attraction will create a strong localized mean field trapping potential in the centre of the trap where the BEC is localized. We observe this in-trap effect as a bimodal distribution of the fermionic component in the axial direction

  18. 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

  19. Characterization of a hybrid target multi-keV x-ray source by a multi-parameter statistical analysis of titanium K-shell emission

    International Nuclear Information System (INIS)

    We studied the titanium K-shell emission spectra from multi-keV x-ray source experiments with hybrid targets on the OMEGA laser facility. Using the collisional-radiative TRANSPEC code, dedicated to K-shell spectroscopy, we reproduced the main features of the detailed spectra measured with the time-resolved MSPEC spectrometer. We developed a general method to infer the Ne, Te and Ti characteristics of the target plasma from the spectral analysis (ratio of integrated Lyman-α to Helium-α in-band emission and the peak amplitude of individual line ratios) of the multi-keV x-ray emission. Finally, these thermodynamic conditions are compared to those calculated independently by the radiation-hydrodynamics transport code FCI2

  20. Characterization of a hybrid target multi-keV x-ray source by a multi-parameter statistical analysis of titanium K-shell emission

    Science.gov (United States)

    Primout, M.; Babonneau, D.; Jacquet, L.; Gilleron, F.; Peyrusse, O.; Fournier, K. B.; Marrs, R.; May, M. J.; Heeter, R. F.; Wallace, R. J.

    2016-03-01

    We have studied the titanium K-shell emission spectra from multi-keV x-ray source experiments with hybrid targets on the OMEGA laser facility. Using the collisional-radiative TRANSPEC code, dedicated to K-shell spectroscopy, we reproduced the main features of the detailed spectra measured with the time-resolved MSPEC spectrometer. We have developed a general method to infer the Ne, Te and Ti characteristics of the target plasma from the spectral analysis (ratio of integrated Lyman-α to Helium-α in-band emission and the peak amplitude of individual line ratios) of the multi-keV x-ray emission. These thermodynamic conditions are compared to those calculated independently by the radiation-hydrodynamics transport code FCI2.

  1. 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.

  2. 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.

  3. Laboratory astrophysics on ASDEX Upgrade: Measurements and analysis of K-shell O, F, and Ne spectra in the 9 - 20 A region

    Science.gov (United States)

    Hansen, S. B.; Fournier, K. B.; Finkenthal, M. J.; Smith, R.; Puetterich, T.; Neu, R.

    2006-01-01

    High-resolution measurements of K-shell emission from O, F, and Ne have been performed at the ASDEX Upgrade tokamak in Garching, Germany. Independently measured temperature and density profiles of the plasma provide a unique test bed for model validation. We present comparisons of measured spectra with calculations based on transport and collisional-radiative models and discuss the reliability of commonly used diagnostic line ratios.

  4. 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)

  5. The temperature dependence of the three-body reaction rate coefficient for some rare-gas atomic ion-atom reactions in the range 100-300K

    International Nuclear Information System (INIS)

    The temperature dependence of some three-body association reaction rate coefficients for some rare-gas atomic ion-rare-gas atom reactions of the type A+ + 2B → AB+ + B have been investigated in the temperature range 100-300 K using a selected ion flow tube technique. The experimental method consists of injecting the ion A+ into the flowing carrier gas B and monitoring the ratio of the concentrations of AB+ to A+ as a function of carrier gas pressure. The three-body association rate coefficients are obtained from an analysis which allows for differential diffusive losses and reaction with impurities in a limited manner. (author)

  6. 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.)

  7. Local environment about O atoms in Pr-Y-Ba-Cu-O films studied by O K-edge XAFS

    International Nuclear Information System (INIS)

    The local environment about oxygen atoms in PrxY1-xBa2Cu3O7 films obtained by laser ablation has been investigated by means of the x-ray absorption fine structure (XAFS) spectroscopy at the O K-edge. It has been found that the Pr atoms do not substitute for the Cu atoms nor form interstitial defects in the CuO2 planes and that the presence of Pr dopant does not disturb the local environment of oxygen

  8. An Algorithm of Important Nodes Finding for Complex Network Based on K-Shell%一种基于K-Shell的复杂网络重要节点发现算法

    Institute of Scientific and Technical Information of China (English)

    顾亦然; 王兵; 孟繁荣

    2015-01-01

    复杂网络中的重要节点通常数量较少,但是对网络的影响却很大。为了能够有效地发现网络拓扑结构中的重要节点,文中基于K -Shell算法,在考虑节点自身重要度的基础上,考虑了邻居节点对自身节点的重要度贡献,提出KSA( K-Shell-Affect)算法。该算法引入影响度概念,用节点自身的K -Shell值和与对其邻居节点的影响度来表征其对邻居节点的重要度贡献。对具有明显社团结构的Zachary网络进行仿真表明,该算法可行有效,克服了K - Shell划分结果的粗粒化,能够正确找到网络中的重要节点,具有一定的合理性,尤其在具有社团结构的网络中,能够十分有效地找到社团内部的核心节点。%There are only a few important nodes in the complex network,which have a great impact on the complex network. In order to discover the important nodes in the complex network effectively,propose a novel algorithm-KSA( K-Shell-Affect) based on K-Shell. The algorithm considers the property of node itself,as well as the important contributions of the adjacent nodes by introducing the concept of affect. The important contribution to the adjacent nodes is characterized by K-Shell and affect to the adjacent nodes. The simulation on the Zachary network,which has a significant community structure,shows that the algorithm is feasible,effective and reasonable,and over-comes the coarse result of the K-Shell . Especially for a network of community structure,can find the core node of the community struc-ture effectively.

  9. Chemical Effect on K Shell X-ray Fluorescence Parameters and Radiative Auger Ratios of Co, Ni, Cu, and Zn Complexes

    Science.gov (United States)

    Cengiz, Erhan; Bıyıklıoğlu, Zekeriya; Küp Aylıkcı, Nuray; Aylıkcı, Volkan; Apaydın, Gökhan; Tıraşoğlu, Engin; Kantekin, Halit

    2010-04-01

    The production cross-sections, intensity ratios, and radiative Auger intensity ratios of Co, Ni, Cu, and Zn elements in different complexes were measured. The chemical effects on the K shell fluorescence parameters and the radiative Auger intensity ratios of these elements were investigated and the changes in these parameters were interpreted according to the charge transfer process. The samples were excited by 59.5 keV γ-rays from a 241Am annular radioactive source. K X-rays emitted by samples were counted by an Ultra-LEGe detector with a resolution of 150 eV at 5.9 keV.

  10. 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

  11. Management of scientific staff at the Harwell Laboratory of the U.K. Atomic Energy Authority

    International Nuclear Information System (INIS)

    The primary role of the Atomic Energy Research Establishment, Harwell is to serve as the main research laboratory supporting the U.K. nuclear power development programme; in addition it undertakes research and development outside of the nuclear field for Government and industrial customers. Overall, there is the need to manage a very large number of separate and often disparate items of work and to ensure effective communication with senior managers of the nuclear power programme and with commercial customers on allocation of resources and technical progress. This is done through a version of 'matrix management'. A large proportion of the technical, commercial and staff management decisions are devolved within Harwell's matrix organisation where teams of staff required for particular items of R and D are formed by arrangements agreed locally between the two axes of the matrix. The smaller groupings of staff created in the matrix are important in providing environments where good staff management practices can be established and where a team spirit aids motivation and technical initiative. (author)

  12. 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.

  13. Efimov studies of an ultracold cloud of 39 K atoms in microgravity: Numerical modelling and experimental design

    Science.gov (United States)

    Mossman, Maren; Engels, Peter; D'Incao, Jose; Jin, Deborah; Cornell, Eric

    2016-05-01

    Ultracold atomic gases at or near quantum degeneracy provide a powerful tool for the investigation of few-body physics. A particularly intriguing few-body phenomenon is the existence of Efimov trimer states at large interatomic scattering lengths. These trimers are predicted to exhibit universal geometric scaling relations, but in practice the situation is complicated e.g. by finite-range and finite-temperature effects. While some Efimov trimers have already been experimentally observed by several groups in ground-based experiments, NASA's Cold Atom Laboratory (CAL) onboard the ISS will greatly enhance the experimentally accessible regimes by providing ultracold clouds of 39 K atoms with temperatures at or below 1 nK, low densities, and long observation times. We present results of numerical modelling and simulations that lay out Efimov experiments capitalizing on the particular strengths of CAL.

  14. K-shell ionization cross sections of Cl and Lα, Lβ X-ray production cross sections of Ba by 6-30 keV electron impact

    International Nuclear Information System (INIS)

    The absolute K-shell ionization cross sections of Cl and Lα, Lβ X-ray production cross sections of Ba by 6-30 keV electron impact have been measured. The target was prepared by evaporating the thin film of compound BaCl2 to the thick pure carbon substrate. The effects of multiple scattering of electrons penetrating the target films, electrons reflected from the thick pure carbon substrates and Bremsstrahlung photons produced when incident electrons impacted on the targets are corrected by using Monte Carlo method. For Ba L-shell X-ray characteristic peaks, the spectra were fitted by using spectrum-fitting program ALLFIT to extract more accurately the Lα and Lβ peak counts. The experimental results, reported here for the first time in the energy region of 6-30 keV, were compared with some theoretical results developed recently.

  15. Kinetics and Mechanism of the Gas-Phase Reaction of Selected Carbonyls with Cl Atoms between 250 and 340 K

    Science.gov (United States)

    Hasson, A. S.; Algrim, L.; Abdelhamid, A.; Tyndall, G. S.; Orlando, J. J.

    2013-12-01

    Carbonyls are important products from the gas phase degradation of most volatile organic compounds. Their atmospheric reactions therefore have a significant impact on atmospheric composition, particularly in aged air masses. While the reactions of short-chain linear carbonyls are well understood, the chemistry of larger (> C6) and branched carbonyl is more uncertain. To provide insight into these reactions, the reactions of three carbonyls (methyl isopropyl ketone, MIK; di-isopropyl ketone, DIK; and diethyl ketone, DEK) with chlorine atoms were investigated between 250 and 340 K and 1 atm in the presence and absence of NOx and an HO2 source (methanol). Experiments were performed in a photochemical reactor using a combination of long-path Fourier transform infra-red spectroscopy, proton transfer reaction mass spectrometry and gas chromatography with flame ionization detection. The kinetics were studied using the relative rate technique with butanone and isopropanol as the reference compounds. The Arrhenius expression for the three rate coefficients was determined to be k(DEK+Cl) = 3.87 x 10-11e(2 × 7 kJ/mol)/RT cm3 molecules-1 s-1 , k(MIPK+Cl) = 7.20 x 10-11e(0.2× 8 kJ/mol)/RT cm3 molecules-1 s-1 , and k(DIPK+Cl) = 3.33 x 10-10e(-3× 8 kJ/mol)/RT cm3 molecules-1 s-1 . Measured reaction products accounted for 38-72 % of the reacted carbon and were consistent with strong deactivation of the carbon atom adjacent to the carbonyl group with respect to H-atom abstraction by Cl atoms. The product distributions also provide insight into radical recycling from the organic peroxy + HO2 reaction, and the relative rates of isomerization, fragmentation and reaction with O2 for carbonyl-containing alkoxy radicals. Implications of these results will be discussed.

  16. Thermodynamics and kinetic behaviors of thickness-dependent crystallization in high-k thin films deposited by atomic layer deposition

    International Nuclear Information System (INIS)

    Atomic layer deposition is adopted to prepare HfO2 and Al2O3 high-k thin films. The HfO2 thin films are amorphous at the initial growth stage, but become crystallized when the film thickness (h) exceeds a critical value (hcritical*). This phase transition from amorphous to crystalline is enhanced at higher temperatures and is discussed, taking into account the effect of kinetic energy. At lower temperatures, the amorphous state can be maintained even when h>hcritical* owing to the small number of activated atoms. However, the number of activated atoms increases with the temperature, allowing crystallization to occur even in films with smaller thickness. The Al2O3 thin films, on the other hand, maintain their amorphous state independent of the film thickness and temperature owing to the limited number of activated atoms. A thermodynamic model is proposed to describe the thickness-dependent phase transition

  17. Molecular theory of K-vacancy production in heavy-ion-atom collisions at small impact parameters

    International Nuclear Information System (INIS)

    1 s sigma vacancy production is calculated by approximating the 1 s sigma molecular wave function with an atomic 1s wave function for a charge Z(R) centered at a distance h(R) from the heavier nucleus. h(R) and Z(R) are determined by minimizing the 1 s sigma electronic energy. Previous calculations with the atomic semi-classsical approximation (h = 0, Z(R) = Z2, the target atomic number) showed that the probability of making Cu K vacancies in 0.5- to 2-MeV/a.m.u. H+, D+, and He+ + Cu collisions can be written as P(theta) = A(1 + B cos theta), where theta is the scattering angle and A and B are constants for theta approx. > 100. Although the recoil and dipole excitation contributions to P(theta) (which interfere destructively in the atomic theory) are independently smaller in the molecular calculations, similar B values are obtained. (orig.)

  18. 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.

  19. 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.

  20. 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.

  1. Preparation of α-alanine-3H by the interaction of atomic tritium heated up to 2000 K with a solid alanine target at 77 K

    International Nuclear Information System (INIS)

    Absorption of hydrogen by alanine targets, the target behaviour and the yield of α-alanine-3H were studied in experiments involving straight passage of H and T atoms from the sourse (2000 K) to the target (77 K) as a function of the exposure time. In the studies with 3H2 the radioactivity of the gas phase was decreasing more rapidly than the overall pressure of hydrogen: H3H accumulates more rapidly in the gas phase. Alanine decomposition products were identified. The conditions for the studies of α-alanine-3H are suggested

  2. 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.

  3. Comment on "Atomic mass compilation 2012" by B. Pfeiffer, K. Venkataramaniah, U. Czok, C. Scheidenberger

    CERN Document Server

    Audi, Georges; Block, Michael; Bollen, Georg; Herfurth, Frank; Goriely, Stéphane; Hardy, John C; Kondev, Filip G; Kluge, Juergen H; Lunney, David; Pearson, Mike J; Savard, Guy; Sharma, Kumar; Wang, Meng; Zhang, Yuhu

    2014-01-01

    This "Comment" submitted to ADNDT on December 13, 2013 concerns a publication entitled "Atomic Mass Compilation 2012", which is due to appear in the March 2014 issue of the journal Atomic Data and Nuclear Data Tables (available online on September 6, 2013). We would like to make it clear that this paper is not endorsed by the Atomic Mass Evaluation (AME) international collaboration. The AME provides carefully recommended evaluated data, published periodically. The "Atomic Mass Compilation 2012" is not to be associated with the latest publication, AME2012, nor with any of the previously published mass evaluations that were developed under the leadership of Prof. A.H. Wapstra. We found the data presented in "Atomic Mass Compilation 2012" to be misleading and the approach implemented to be lacking in rigour since it does not allow to unambiguously trace the original published mass values. Furthermore, the method used in "Atomic Mass Compilation 2012" is not valid and leads to erroneous and contradictory outputs,...

  4. Theoretical investigation of the hypothesized crossing between the Penning and atomic autoionizing states of He+K

    Energy Technology Data Exchange (ETDEWEB)

    Padial, N.T.; Martin, R.L.; Cohen, J.S.; Lane, N.F.

    1989-03-01

    The Penning ionization interaction He(12s/sup 3/S)+K(3p/sup 6/4s) and the atomic autoionizing state interaction He(1s/sup 2/)+K(3p/sup 5/4s/sup 2/) have been determined in a configuration-interaction calculation utilizing a basis set designed to treat these two states equitably. In contrast to an earlier calculation, the corresponding two potential curves are found not to cross. This finding puts in question the original speculation that the observed large He/sup */+K ionization cross section is due partially to collisional excitation of atomic states that subsequently autoionize. However, the calculated Penning ionization cross section is still in agreement with the experimental measurement.

  5. 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

  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. Spectral analysis of K-shell X-ray emission of magnesium plasma produced by ultrashort high-intensity laser pulse irradiation

    Indian Academy of Sciences (India)

    V Arora; U Chakravarty; Manoranjan P Singh; J A Chakera; P A Naik; P D Gupta

    2014-02-01

    Spectral analysis of K-shell X-ray emission of magnesium plasma, produced by laser pulses of 45 fs duration, focussed up to an intensity of ∼1018 W cm-2, is carried out. The plasma conditions prevalent during the emission of X-ray spectrum were identified by comparing the experimental spectra with the synthetic spectra generated using the spectroscopic code Prism-SPECT. It is observed that He-like resonance line emission occurs from the plasma region having sub-critical density, whereas K- emission arises from the bulk solid heated to a temperature of 10 eV by the impact of hot electrons. K- line from Be-like ions was used to estimate the hot electron temperature. A power law fit to the electron temperature showed a scaling of 0.47 with laser intensity.

  8. Spectroscopic Investigation of p-Shell Lambda Hypernuclei by the (e,e'K+) Reaction

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Chunhua [Hampton Univ., Hampton, VA (United States)

    2014-08-01

    Hypernuclear spectroscopy is a powerful tool to investigate Lambda-N interaction. Compared with other Lambda hypernuclei productions, electroproduction via the (e,e'K+) reaction has the advantage of exciting states deeply inside of the hypernucleus and achieving sub-MeV energy resolution. The E05-115 experiment, which was successfully performed in 2009, is the third generation hypernuclear experiment in JLab Hall C. A new splitter magnet and electron spectrometer were installed, and beam energy of 2.344 GeV was selected in this experiment. These new features gave better field uniformity, optics quality and made the tilt method more effective in improving yield-to-background ratio. The magnetic optics of the spectrometers were carefully studied with GEANT simulation, and corrections were applied to compensate for the fringe field cross talk between the compact spectrometer magnets. The non-linear least chi-squared method was used to further calibrate the spectrometer with the events from Lambda, Sigma0 and B12Lambda and uniform magnetic optics as well as precise kinematics were achieved. Several p-shell Lambda hypernuclear spectra, including B12Λ, Be10Λ, He7Λ, were obtained with high energy resolution and good accuracy. For B12Λ, eight peaks were recognized with the resolution of ~540keV (FWHM), and the ground state binding energy was obtained as 11.529 ± 0.012(stat.) ± 0.110(syst.) MeV. Be10Λ, twelve peaks were recognized with the resolution of ~520keV (FWHM), and the binding energy of the ground state was determined as 8.710 ± 0.059(stat.) ± 0.114(syst.) MeV. For He7Λ, three peaks were recognized with the resolution of ~730keV, and the ground state binding energy was obtained as 5.510 ± 0.050(stat.) ± 0.120(syst.) MeV. Compared with the published data of B12Λ from the JLab Hall A experiment

  9. Doubly-differential cross section calculations for $K$-shell vacancy production in lithium by fast O$^{8+}$ ion impact

    CERN Document Server

    Śpiewanowski, M D; Horbatsch, M; Kirchner, T

    2016-01-01

    Inner-shell vacancy production for the O$^{8+}$-Li collision system at 1.5 MeV/amu is studied theoretically. The theory combines single-electron amplitudes for each electron in the system to extract multielectron information about the collision process. Doubly-differential cross sections obtained in this way are then compared with the recent experimental data by LaForge et al. [J. Phys. B 46, 031001 (2013)] yielding good resemblance, especially for low outgoing electron energy. A careful analysis of the processes that contribute to inner-shell vacancy production shows that the improvement of the results as compared to single-active-electron calculations can be attributed to the leading role of two-electron excitation-ionization processes.

  10. Development of an optically pumped atomic magnetometer using a K-Rb hybrid cell and its application to magnetocardiography

    Directory of Open Access Journals (Sweden)

    Yosuke Ito

    2012-09-01

    Full Text Available We have developed an optically pumped atomic magnetometer using a hybrid cell of K and Rb. The hybrid optical pumping technique can apply dense alkali-metal vapor to the sensor head and leads to high signal intensity. We use dense Rb vapor as probed atoms, and achieve a sensitivity of approximately 100 fTrms/Hz1/2 around 10 Hz. In this case, the sensitivity is limited by the system noise, and the magnetic linewidth is narrower than that for direct Rb optical pumping. We demonstrated magnetocardiography using the magnetometer and obtained clear human magnetocardiograms.

  11. K-shell emission x-ray imaging of Z-pinch plasmas with a pinhole and a logarithmic spiral crystal.

    Science.gov (United States)

    Yang, Qingguo; Li, Zeren; Peng, Qixian; Yang, Libing; Chen, Guanhua; Ye, Yan; Huang, Xianbin; Cai, Hongchun; Li, Jing; Xiao, Shali

    2011-09-01

    An in-chamber, mini x-ray imaging instrument employs a pinhole and a logarithmic spiral crystal has been developed for obtaining K-shell line images of the imploding aluminum wire array on the "Yang" accelerator. The logarithmic spiral crystal acts as a monochromator and a non-dispersive mirror that reflects the pinhole image to a x-ray film detector with a very narrow photon energy bandwidth (intercombination line (1588.3 eV) emission. The primary experimental data corresponding to these two configurations are presented and discussed. PMID:21974579

  12. 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

  13. 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...

  14. Inner-shell ionization and biological radiations effects

    International Nuclear Information System (INIS)

    Biological effects of K-ionizations followed by Auger cascades have been much studied to elucidate mechanisms of cell inactivation and DNA repair and to develop therapeutic applications. Experiments performed with incorporated radionuclides (125I) or incorporated elements (Br, I, P) photoionized in the K-shell using synchrotron radiation all displayed a K + Auger enhancement. The interest in K-ionization rose again when recent works suggested that K-ionizations in C, N, 0 atoms of DNA could be the primary physical events responsible for cell death induced by heavy ions. Photoabsorption experiments at the C-K threshold support this hypothesis. (authors)

  15. Experimental investigation of evaporative cooling mixture of bosonic 87Rb and fermionic 40K atoms with microwave and radio frequency radiation

    Institute of Scientific and Technical Information of China (English)

    wang Peng-Jun; xiong De-Zhi; Fu Zheng-Kun; Zhang Jing

    2011-01-01

    We investigate sympathetic cooling fermions 40K by evaporatively cooling bosonic 87Rb atoms in a magnetic trap with microwave and radio frequency induced evaporations in detail. The mixture of bosonic and fermionic atoms is Quadrupole-Ioffe-Configuration trap. Comparing microwave with radio frequency evaporatively cooling bosonic 87Rb states, which are generated in the evaporative process, gives rise to a significant loss of 40K due to inelastic collisions.Thus, the rubidium atoms populated in the |2, 1> Zeeman states should be removed in order to effectively perform sympathetically cooling 40K with the evaporatively cooled 87Rb atoms.

  16. Studies on effective atomic numbers, electron densities from mass attenuation coefficients near the K edge in some samarium compounds.

    Science.gov (United States)

    Akman, F; Durak, R; Turhan, M F; Kaçal, M R

    2015-07-01

    The effective atomic numbers and electron densities of some samarium compounds were determined using the experimental total mass attenuation coefficient values near the K edge in the X-ray energy range from 36.847 up to 57.142 keV. The measurements, in the region from 36.847 to 57.142 keV, were done in a transmission geometry utilizing the Kα2, Kα1, Kβ1 and Kβ2 X-rays from different secondary source targets excited by the 59.54 keV gamma-photons from an Am-241 annular source. This paper presents the first measurement of the effective atomic numbers and electron densities for some samarium compounds near the K edge. The results of the study showed that the measured values were in good agreement with the theoretically calculated ones. PMID:25880612

  17. In--Flight ($K^-,p$) Reactions for the Formation of Kaonic Atoms and Kaonic Nuclei in Green function method

    OpenAIRE

    Yamagata, J.; Nagahiro, H.; Hirenzaki, S.

    2006-01-01

    We study theoretically the kaonic atom and kaonic nucleus formations in the in--flight ($K^-,p$) reactions using the Green function method, which is suited to evaluate formation rates both of stable and unstable bound systems. We consider $^{12}$C and $^{16}$O as the targets and calculate the spectra of the ($K^-,p$) reactions. We conclude that a no peak structure due to kaonic nucleus formation is expected in the reaction spectra calculated with the chiral unitary kaon--nucleus optical poten...

  18. 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

  19. The single-nucleon energies of closed shell nuclei, influenced by n(k,rho), in the framework of Hartree-Fock inspired-scheme and LOCV method

    CERN Document Server

    Mariji, Hodjat

    2016-01-01

    The nucleon single-particle energies (SPEs) of the selected closed shell nuclei; that is, 16O, 40Ca, and 56Ni, are obtained by using the diagonal matrix elements of two-body effective interaction, which generated through the lowest order constrained variational (LOCV) calculations for the symmetric nuclear matter with the AV18 phenomenological nucleon-nucleon potential. The SPEs at the major levels of nuclei are calculated by employing a Hartree-Fock inspired-scheme in the spherical harmonic oscillator basis. In the scheme, the correlation influences are taken into account by imposing the nucleon effective mass factor on the radial wave functions of the major levels. Replacing the density-dependent one-body momentum distribution functions of nucleons, n(k,rho), with the Heaviside functions, the role of n(k,rho) on the nucleon SPEs at the major levels of the selected closed shell nuclei, is investigated. The best fit of spin-orbit splitting is taken into account when correcting the major levels of the nuclei b...

  20. The A(K{sub stop}{sup -},{pi}{sup {+-}}{Sigma}{sup {+-}})A{sup '} reaction on p-shell nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Agnello, M. [Dip. di Fisica Politecnico di Torino, via Duca degli Abruzzi, Torino, and INFN Sez. di Torino, via P. Giuria 1, Torino (Italy); Benussi, L.; Bertani, M. [Laboratori Nazionali di Frascati dell' INFN, via E. Fermi 40, Frascati (Italy); Bhang, H.C. [Dep. of Physics, Seoul National Univ., 151-742 Seoul (Korea, Republic of); Bonomi, G. [Dip. di Meccanica, Universita di Brescia, via Valotti 9, Brescia, and INFN Sez. di Pavia, via Bassi 6, Pavia (Italy); Botta, E. [Dipartimento di Fisica Sperimentale, Universita di Torino, via P. Giuria 1, Torino, and INFN Sez. di Torino, via P. Giuria 1, Torino (Italy); Bregant, M. [Dip. di Fisica, Univ. di Trieste, via Valerio 2, Trieste, and INFN, Sez. di Trieste, via Valerio 2, Trieste (Italy); Bressani, T. [Dipartimento di Fisica Sperimentale, Universita di Torino, via P. Giuria 1, Torino, and INFN Sez. di Torino, via P. Giuria 1, Torino (Italy); Bufalino, S. [INFN Sez. di Torino, via P. Giuria 1, Torino (Italy); Busso, L. [Dipartimento di Fisica Generale, Universita di Torino, via P. Giuria 1, Torino, and INFN Sez. di Torino, via P. Giuria 1, Torino (Italy); Calvo, D. [INFN Sez. di Torino, via P. Giuria 1, Torino (Italy); Camerini, P. [Dip. di Fisica, Univ. di Trieste, via Valerio 2, Trieste, and INFN, Sez. di Trieste, via Valerio 2, Trieste (Italy); Dalena, B. [Dip. di Fisica Univ. di Bari, via Amendola 179, Bari, and INFN Sez. di Bari, via Amendola 179, Bari (Italy); De Mori, F. [Dipt. di Fisica Sperimentale, Univ. di Torino, via P. Giuria 1, Torino, and INFN Sez. di Torino, via P. Giuria 1, Torino (Italy); D' Erasmo, G. [Dip. di Fisica Univ. di Bari, via Amendola 179, Bari, and INFN Sez. di Bari, via Amendola 179, Bari (Italy); Fabbri, F.L. [Lab. Nazionali di Frascati dell' INFN, Frascati (Italy); Feliciello, A.; Filippi, A. [INFN Sez. di Torino, via P. Giuria 1, Torino (Italy); Fiore, E.M. [Dip. di Fisica Univ. di Bari, via Amendola 179, Bari, and INFN Sez. di Bari, via Amendola 179, Bari (Italy)

    2011-10-25

    This Letter is concerned with the study of the K{sub stop}{sup -}A{yields}{pi}{sup {+-}}{Sigma}{sup {+-}}A' reaction in p-shell nuclei, i.e., {sup 6,7}Li, {sup 9}Be, {sup 13}C and {sup 16}O. The {pi}{sup {+-}}{Sigma}{sup {+-}}/K{sub stop}{sup -} emission rates are reported as a function of A. These rates are discussed in comparison with previous findings. The ratio {pi}{sup -}{Sigma}{sup +}/{pi}{sup +}{Sigma}{sup -} in p-shell nuclei is found to depart largely from that on hydrogen, which provides support for large in-medium effects possibly generated by the sub-threshold {Lambda}(1405). The continuum momentum spectra of prompt pions and free sigmas are also discussed as well as the {pi}{sup {+-}}{Sigma}{sup {+-}} missing mass behavior and the link with the reaction mechanism. The apparatus used for the investigation is the FINUDA spectrometer operating at the DA{Phi}NE{phi}-factory (LNF-INFN, Italy).

  1. Measurements of the K-shell ionization cross sections of Si by 3-25-keV electron impact using the thick-target method

    International Nuclear Information System (INIS)

    In this paper, the K-shell ionization cross sections of Si element in the threshold energy region of 3-25 keV have been measured by using the thick-target method. With the Monte Carlo simulations, the effects of multiple scattering of incident electrons and from the bremsstrahlung photons and other secondary particles in the thick-target method have been discussed. The detection efficiency calibration in the lower-energy region has been performed by using the bremsstrahlung spectra of thick carbon target by electron impact in combination with the use of standard x-ray sources, and the detector thickness parameters have also been determined by a nonlinear least-squares fit. The ill-posed inverse problem involved in the thick-target method has been dealt with by the Tikhonov regularization method. The experimental K-shell ionization cross sections for Si element obtained in this paper have also been compared with some theoretical models, and it has been observed that the experimental data in this paper are in good agreement with the theoretical values based on the distorted-wave Born approximation model developed most recently.

  2. Studies on effective atomic numbers, electron densities from mass attenuation coefficients near the K edge in some samarium compounds

    International Nuclear Information System (INIS)

    The effective atomic numbers and electron densities of some samarium compounds were determined using the experimental total mass attenuation coefficient values near the K edge in the X-ray energy range from 36.847 up to 57.142 keV. The measurements, in the region from 36.847 to 57.142 keV, were done in a transmission geometry utilizing the Kα2, Kα1, Kβ1 and Kβ2 X-rays from different secondary source targets excited by the 59.54 keV gamma-photons from an Am-241 annular source. This paper presents the first measurement of the effective atomic numbers and electron densities for some samarium compounds near the K edge. The results of the study showed that the measured values were in good agreement with the theoretically calculated ones. - Highlights: • The effective atomic numbers and electron densities determined for some samarium compounds from total mass attenuation coefficients near the K edge. • The measurements performed using secondary excitation geometry and a Si(Li) detector. • The experimental results compared with the theoretical calculation

  3. 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.)

  4. A High Sensitive Atomic Co-magnetometer for Rotation Rate Measurement Based on K-Rb-21Ne

    Science.gov (United States)

    Chen, Yao; Zou, Sheng; Quan, Wei; Lu, Yan; Ding, Ming; Fang, Jiancheng

    2016-05-01

    Atomic co-magnetometers use two spin ensembles occupying the same volume in glass vapor cells to suppress their sensitivity to magnetic field noise and leave them sensitive to rotation rate, anomalous fields, etc. Due to the small gyromagnetic ratio of the 21 Ne atom, an atomic co-magnetometer based on 21Ne is very suitable for rotation rate measurement. Thus, we focus on and report a co-magnetometer for rotation rate measurement based on K-Rb-21Ne. We have developed a rotating co-magnetometer which is calibrated by the rotation of the earth. All the optics in the co-magnetometer have been encased in a bell jar in which the air is pumped away to suppress the air density fluctuation noise. MnZn ferrite is also utilized in the inner most magnetic field shielding system to suppress the magnetic field noise. We have reached rotation rate sensitivity of 2.1 * 10-8 rad/ s / sqrt(Hz) or equivalent magnetic field noise level of 1.4 fT / sqrt(Hz) . The K-Rb-21Ne co-magnetometer has many potential applications for precision measurements, including spin dependent force detecting, Electric Dipole Moment measurement and fundamental symmetry test.

  5. CMUTs with High-K Atomic Layer Deposition Dielectric Material Insulation Layer

    OpenAIRE

    Xu, Toby; Tekes, Coskun; Degertekin, F. Levent

    2014-01-01

    Use of high-κ dielectric, atomic layer deposition (ALD) materials as an insulation layer material for capacitive micromachined ultrasonic transducers (CMUTs) is investigated. The effect of insulation layer material and thickness on CMUT performance is evaluated using a simple parallel plate model. The model shows that both high dielectric constant and the electrical breakdown strength are important for the dielectric material, and significant performance improvement can be achieved, especiall...

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

    International Nuclear Information System (INIS)

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

  7. Effect of the Initial Load Parameters on the K-shell Output of Al Planar Wire Arrays Operating in the Microsecond Implosion Regime

    Science.gov (United States)

    Shishlov, A.; Chaikovsky, S.; Fedunin, A.; Fursov, F.; Kokshenev, V.; Kurmaev, N.; Labetsky, A.; Oreshkin, V.; Rousskikh, A.; Labetskaya, N.

    2009-01-01

    A set of microsecond implosion experiments was carried on the GIT-12 generator to study the radiative performance of Al planar wire arrays. The load parameters such as a wire diameter, a gap between the wires, the number of wires, and the total planar wire mass and width were varied during the experiments, however the implosion time and the peak implosion current were almost the same for all load configurations. This ensured equal energy deposition to the plasma due to kinetic mechanisms for all load configurations. Two implosion regimes with the implosion times of 1050 ns and 850 ns were investigated. The experimental data on the K-shell radiation yield and power at varying load parameters are presented.

  8. 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.

  9. K-shell emission x-ray imaging of z-pinch plasmas with a pinhole and a logarithmic spiral crystal

    Energy Technology Data Exchange (ETDEWEB)

    Yang Qingguo; Li Zeren; Peng Qixian; Yang Libing; Chen Guanhua; Ye Yan; Huang Xianbin; Cai Hongchun; Li Jing [Institute of Fluid Physics, CAEP, Mianyang, Sichuan 621900 (China); Xiao Shali [Key Laboratory of Optic-electronic Technology and System, Ministry of Education, Chongqing University, Chongqing 400044 (China)

    2011-09-15

    An in-chamber, mini x-ray imaging instrument employs a pinhole and a logarithmic spiral crystal has been developed for obtaining K-shell line images of the imploding aluminum wire array on the ''Yang'' accelerator. The logarithmic spiral crystal acts as a monochromator and a non-dispersive mirror that reflects the pinhole image to a x-ray film detector with a very narrow photon energy bandwidth (<1 eV, mainly determined by the width of rocking curve of the crystal). Two imaging configurations with the use of Quartz (1010) crystal and Mica (002) crystal are designed, respectively, to image the Al Ly{sub {alpha}2} line (1727.7 eV) emission and Al He{sub {alpha}} intercombination line (1588.3 eV) emission. The primary experimental data corresponding to these two configurations are presented and discussed.

  10. Formation of hydrogen peroxide and water from the reaction of cold hydrogen atoms with solid oxygen at 10K

    CERN Document Server

    Miyauchi, N; Chigai, T; Nagaoka, A; Watanabe, N; Kouchi, A

    2008-01-01

    The reactions of cold H atoms with solid O2 molecules were investigated at 10 K. The formation of H2O2 and H2O has been confirmed by in-situ infrared spectroscopy. We found that the reaction proceeds very efficiently and obtained the effective reaction rates. This is the first clear experimental evidence of the formation of water molecules under conditions mimicking those found in cold interstellar molecular clouds. Based on the experimental results, we discuss the reaction mechanism and astrophysical implications.

  11. Evaluation of Toxicological Effects of an Aqueous Extract of Shells from the Pecan Nut Carya illinoinensis (Wangenh.) K. Koch and the Possible Association with Its Inorganic Constituents and Major Phenolic Compounds

    Science.gov (United States)

    Porto, Luiz Carlos S.; Sousa, Karen; Ambrozio, Mariana L.; de Almeida, Aline; dos Santos, Carla Eliete I.; Dias, Johnny F.; Allgayer, Mariangela C.; dos Santos, Marcela S.; Pereira, Patrícia; Picada, Jaqueline N.

    2016-01-01

    Background. Industrial processing of the pecan nut Carya illinoinensis K. Koch generated a large amount of shells, which have been used to prepare nutritional supplements and medicinal products; however, the safe use of shells requires assessment. This study evaluated the toxic, genotoxic, and mutagenic effects of pecan shell aqueous extract (PSAE) and the possible contribution of phenolic compounds, ellagic and gallic acids, and inorganic elements present in PSAE to induce toxicity. Results. Levels of inorganic elements like K, P, Cl, and Rb quantified using the Particle-Induced X-Ray Emission method were higher in PSAE than in pecan shells, while Mg and Mn levels were higher in shells. Mice showed neurobehavioral toxicity when given high PSAE doses (200–2,000 mg kg−1). The LD50 was 1,166.3 mg kg−1. However, PSAE (50–200 mg·kg−1) and the phenolic compounds (10–100 mg·kg−1) did not induce DNA damage or mutagenicity evaluated using the comet assay and micronucleus test. Treatment with ellagic acid (10–100 mg·kg−1) decreased triglyceride and glucose levels, while treatments with PSAE and gallic acid had no effect. Conclusion. Pecan shell toxicity might be associated with high concentrations of inorganic elements such as Mn, Al, Cu, and Fe acting on the central nervous system, besides phytochemical components, suggesting that the definition of the safe dose should take into account the consumption of micronutrients. PMID:27525021

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

    Science.gov (United States)

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

    2009-05-28

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

  13. 76 FR 35934 - In the Matter of: SHC Corp. (f/k/a Victormaxx Technologies, Inc.), Shells Seafood Restaurants...

    Science.gov (United States)

    2011-06-20

    ... information concerning the securities of Solar Satellite Communication, Inc. because it has not filed any... The Cap One Group, Inc.), Solar Satellite Communication, Inc., and Sonoran Energy, Inc.; Order of... lack of current and accurate information concerning the securities of SHC Corp. (f/k/a...

  14. 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.

  15. 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

  16. 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.

  17. 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

  18. 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.

  19. 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.

  20. K-shell Photoionization of Na-like to Cl-like Ions of Mg, Si, S, Ar, and Ca

    Science.gov (United States)

    Witthoeft, M. C.; Garcia, J.; Kallman, T. R.; Bautista, M. A.; Mendoza, C.; Palmeri, P.; Quinet, P.

    2010-01-01

    We present R-matrix calculations of photoabsorption and photoionization cross sections across the K edge of Mg, Si, S, Ar, and Ca ions with more than 10 electrons. The calculations include the effects of radiative and Auger damping by means of an optical potential. The wave functions are constructed from single-electron. orbital bases obtained using a Thomas-Fermi-Dirac statistical model potential. Configuration interaction is considered among all states up to n = 3. The damping processes affect the resonances converging to the K-thresholds causing them to display symmetric profiles of constant width that smear the otherwise sharp edge at the photoionization threshold. These data are important for the modeling of features found in photoionized plasmas.

  1. Preparation of activated carbon from coconut shell chars in pilot-scale microwave heating equipment at 60 kW

    International Nuclear Information System (INIS)

    Experiments to prepare activated carbon by microwave heating indicated that microwave energy can decrease reaction temperature, save the energy and shorten processing time remarkably compared to conventional heating, owing to its internal and volumetric heating effects. The above results were based on the laboratory-scale experiments. It is desirable to develop a pilot-scale microwave heating equipment and investigate the parameters with the aim of technological industrialization. In the present study, the components and features of the self-invented equipment were introduced. The temperature rise curves of the chars were obtained. Iodine numbers of the activated carbons all exceed the state standard of China under the following conditions: 25 kg/h charging rate, 0.42 rev/min turning rate of ceramic tube, flow rate of steam at pressure of 0.01 MPa and 40 kW microwave heating power after 60 kW pre-activation for 30 min. Pore structure of the sample obtained at a time point of 46 h, which contained BET surface area, and pore size distributions of micropores and total pores, was tested by nitrogen adsorption at 77 K

  2. Scale heights and equivalent widths of the iron K-shell lines in the Galactic diffuse X-ray emission

    CERN Document Server

    Yamauchi, Shigeo; Nobukawa, Masayoshi; Uchiyama, Hideki; Koyama, Katsuji

    2016-01-01

    This paper reports the analysis of the X-ray spectra of the Galactic diffuse X-ray emission (GDXE) in the Suzaku archive. The fluxes of the Fe I K alpha (6.4 keV), Fe XXV,He alpha (6.7 keV) and Fe XXVI Ly alpha (6.97 keV) lines are separately determined. From the latitude distributions, we confirm that the GDXE is decomposed into the Galactic center (GCXE), the Galactic bulge (GBXE) and the Galactic ridge (GRXE) X-ray emissions. The scale heights (SHs) of the Fe XXV He alpha line of the GCXE, GBXE and GRXE are determined to be ~40, ~310 and ~140 pc, while those of the Fe I K alpha line are ~30, ~160 and ~70 pc, respectively. The mean equivalent widths (EWs) of the sum of the Fe XXV He alpha and Fe XXVI Ly alpha lines are ~750 eV, ~600 eV and ~550 eV, while those of the Fe I K alpha line are ~150~eV, ~60~eV and ~100~eV for the GCXE, GBXE and GRXE, respectively. The origin of the GBXE, GRXE and GCXE is separately discussed based on the new results of the SHs and EWs, in comparison with those of the Cataclysmic ...

  3. 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.

  4. Lifetime Measurements of $ \\pi ^+ \\pi ^- $ and $\\pi^{+-} K^{-+}$ Atoms to Test Low-Energy QCD Predictions

    CERN Multimedia

    Ponta, T C; Dumitriu, D E; Afanasyev, L; Zhabitskiy, M; Rykalin, V; Hons, Z; Schacher, J; Yazkov, V; Gerndt, J; Detraz, C C; Guaraldo, C; Dreossi, D; Smolik, J; Gorchakov, O; Nikitin, M; Dudarev, A; Kluson, J; Hansroul, M; Okada, K; Constantinescu, S; Kruglov, V; Komarov, V; Takeutchi, F; Tarta, P D; Kuptsov, A; Nemenov, L; Karpukhin, V; Shliapnikov, P; Brekhovskikh, V; Saborido silva, J J; Drijard, D; Rappazzo, G F; Pentia, M C; Gugiu, M M; Kruglova, L; Pustylnik, Z; Trojek, T; Vrba, T; Iliescu, M A; Duma, M; Ciocarlan, C; Kulikov, A; Ol'shevskiy, V; Ryazantsev, A; Chiba, M; Anania, A; Tarasov, A; Gritsay, K; Lapchine, V; Cechak, T; Lopez aguera, A

    2002-01-01

    %PS212 \\\\ \\\\ The proposed experiment aims to measure the lifetime of $ \\pi ^+ \\pi ^- $ atoms in the ground state with 10\\% precision, using the 24~GeV/c proton beam of the CERN Proton Synchrotron. As the value of the above lifetime of order 10$ ^- ^{1} ^{5} $s is dictated by a strong interaction at low energy, the precise measurement of this quantity enables to determine a combination of S-wave pion scattering lengths to 5\\%. Pion scattering lengths have been calculated in the framework of chiral perturbation theory and values predicted at the same level of accuracy have, up to now, never been confronted with accurate experimental data. Such a measurement would submit the understanding of chiral symmetry breaking of QCD to a crucial test.

  5. Chemical reactivity of hydrogen, nitrogen, and oxygen atoms at temperatures below 100 k

    Science.gov (United States)

    Mcgee, H. A., Jr.

    1973-01-01

    The synthesis of unusual compounds by techniques employing cryogenic cooling to retard their very extreme reactivity was investigated. Examples of such species that were studied are diimide (N2H2), cyclobutadiene (C4H4), cyclopropanone (C3H4O), oxirene (C2H2O), and many others. Special purpose cryogenically cooled inlet arrangements were designed such that the analyses incurred no warm-up of the cold, and frequently explosively unstable, compounds. Controlled energy electron impact techniques were used to measure critical potentials and to develop the molecular energetics and thermodynamics of these molecules and to gain some insight into their kinetic characteristics as well. Three and four carbon strained ring molecules were studied. Several reactions of oxygen and hydrogen atoms with simple molecules of H, N, C, and O in hard quench configurations were studied. And the quench stabilization of BH3 was explored as a model system in cryochemistry.

  6. From k{center_dot}p to atomic calculations applied to semiconductor heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Pedesseau, L; Cornet, C; Dore, F; Even, J [FOTON-INSA Laboratory, UMR 6058 au CNRS, INSA de Rennes, 20 avenue des Buttes de Coemes, CS 14315, 35043 RENNES Cedex (France); Schliwa, A; Bimberg, D [Institut fuer Festkoerperphysik, Technische Universitaet Berlin, Hardenbergstrasse 36, 10623 Berlin (Germany)], E-mail: laurent.pedesseau@insa-rennes.fr

    2008-03-15

    We present a brief overview of the main results obtained in our group for the simulation of electronic and optical properties of semiconductor heterostructures. A short introduction is given on InAs quantum dots, grown on InP, GaAs and GaP substrates. It is shown that 1-band k.p calculations can be used in the reciprocal space, in order to get a simulation of perfectly ordered array of quantum dots. A semianalytical modeling is also presented, including an axial approximation of the 8*8 band k.p calculations. Linear and nonlinear contributions to piezoelectricity are discussed. A complete 8*8 band k.p approach is then used to show the properties of InAs/InP quantum dots, with different substrate orientations. Finally, a study of the highly strained InAs/GaP interface is performed with a first principle modeling using ABINIT packages. Band lineups and evolution of gap energies are calculated, and compared to those found by Chuang et al.

  7. Small atomic displacements in the molybdenophosphates AMo2P3O12 (A = K, Rb, Tl)

    International Nuclear Information System (INIS)

    KMo2P3O12, Mr = 515.90, orthorhombic, Pbnm, a = 17.6398(14), b = 9.1761(4), c = 12.3000(8) A, V = 1990.9(4) A3, Z=8, Dx = 3.44 Mg m-3, λ(Mo Kα) = 0.71069 A, μ = 3.42 mm-1, F(000) = 1952. T = 294 K, R = 0.028 for 2123 reflections. RbMo2P3O12, Mr = 562.26, orthorhombic, Pbcm, a = 8.8314(8), b = 9.2368(7), c = 12.3051(9) A, V = 1003.8(4) A3, Z=4, Dx = 3.72 Mg m-3, λ(Mo Kα) = 0.71069 A, μ = 8.08 mm-1, F(000) = 1048, T = 294 K, R = 0.044 for 2073 reflections. The Mo2P3O12 frameworks of the K, Rb and Tl compounds are almost the same. The main difference is in the position of the alkaline-earth ions in the tunnels, which induces, in the potassium compound, a superstructure along a. The alkaline-earth ions are slightly displaced as their size decreases in order that the A-O distances may agree with the sum of the ionic radii. (orig.)

  8. 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

  9. 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.

  10. Experimental study of K-shell X-ray emission from argon clusters irradiated by an ultra-intense laser pulse

    International Nuclear Information System (INIS)

    The K-shell X-ray emission of argon clusters irradiated by 1017 W cm-2 laser pulses was spectrally resolved and investigated as a function of different laser and cluster parameters. A special effort was first realized in order to control the laser focusing into the cluster jet and the temporal laser pulse contrast which both were observed to have a drastic influence on the X-ray emission. Cluster mean radius was then varied from 200 to 350 A as well as the laser pulse duration from 30 fs to 3.5 ps (FWHM). The X-ray emission was observed to reach a maximal value for a given laser pulse duration (typically a few times 100 fs), increasing with the cluster mean radius. These observations can be understood in terms of density resonance effect. The X-ray emission duration was also investigated above 3 keV with a streak camera (resolution about 1 ps (FWHM) at 1 kHz). This duration was observed to be close to 3.5 ps (FWHM) at the optimal X-ray emission

  11. The estimation of production rates of $π^+ K^−, π^− K^+$ and $π^+π^−$ atoms in proton-nucleus interactions at 24 and 450 GeV/c

    CERN Document Server

    Gorchakov, O

    2016-01-01

    Short-lived ( τ ∼ 3 × 10 − 15 s ) π + K − , K + π − and π + π − atoms as well as long-lived ( τ ≥ 1 × 10 − 11 s) π + π − atoms produced in proton-nucleus interactions at 24 GeV/c are observed and studied in the DIRAC experiment at the CERN P S. The purpose of this paper is to show that the yields of the short-lived π + K − , K + π − and π + π − atoms in proton-nucleus interactions at 450 GeV/c and θ lab = 4 ◦ are estimated to be, respectively, 17, 38 and 16 times higher. This may allow sign ificantly improving the precision of their lifetime measurement and ππ and πK scattering length combinations | a 0 − a 2 | and | a 1 / 2 − a 3 / 2 | . The yields of the long-lived π + K − , K + π − and π + π − atoms at 450 GeV/c are estimated to be 180,800 and 370 times higher p er time unit than at 24 GeV/c. This may allow the resonance method to be used for measuring the Lamb shift in the ππ atom and a new ππ scattering length combination 2a0 + a2 to be obtaine...

  12. 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 ...

  13. An important discovery - with no electric field, the center of the electron cloud of K atom does not coincide with the nucleus

    OpenAIRE

    You, Pei-Lin

    2009-01-01

    It is a general point of view that in the absence of an external field, the nucleus of an atom is at the center of the electron cloud, so that all kinds of atoms do not have permanent electric dipole moment (EDM). In the fact, the idea is untested. Using two special capacitors containing Potassium vapor we discovered that the electric susceptibility Xe of K atoms is directly proportional to the density N, and inversely to the temperature T, as polar molecules. The experimental K material with...

  14. Plasma-enhanced atomic layer deposition and etching of high-k gadolinium oxide

    International Nuclear Information System (INIS)

    Atomic layer deposition (ALD) of high-quality gadolinium oxide thin films is achieved using Gd(iPrCp)3 and O2 plasma. Gd2O3 growth is observed from 150 to 350 deg. C, though the optical properties of the film improve at higher temperature. True layer-by-layer ALD growth of Gd2O3 occurred in a relatively narrow window of temperature and precursor dose. A saturated growth rate of 1.4 A/cycle was observed at 250 deg. C. As the temperature increases, high-quality films are deposited, but the growth mechanism appears to become CVD-like, indicating the onset of precursor decomposition. At 250 deg. C, the refractive index of the film is stable at ∼1.80 regardless of other deposition conditions, and the measured dispersion characteristics are comparable to those of bulk Gd2O3. XPS data show that the O/Gd ratio is oxygen deficient at 1.3, and that it is also very hygroscopic. The plasma etching rate of the ALD Gd2O3 film in a high-density helicon reactor is very low. Little difference is observed in etching rate between Cl2 and pure Ar plasmas, suggesting that physical sputtering dominates the etching. A threshold bias power exists below which etching does not occur; thus it may be possible to etch a metal gate material and stop easily on the Gd2O3 gate dielectric. The Gd2O3 film has a dielectric constant of about 16, exhibits low C-V hysteresis, and allows a 50 x reduction in gate leakage compared to SiO2. However, the plasma enhanced atomic layer deposition (PE-ALD) process causes formation of an ∼1.8 nm SiO2 interfacial layer, and generates a fixed charge of -1.21 x 1012 cm-2, both of which may limit use of PE-ALD Gd2O3 as a gate dielectric.

  15. CMUTs with high-K atomic layer deposition dielectric material insulation layer.

    Science.gov (United States)

    Xu, Toby; Tekes, Coskun; Degertekin, F

    2014-12-01

    Use of high-κ dielectric, atomic layer deposition (ALD) materials as an insulation layer material for capacitive micromachined ultrasonic transducers (CMUTs) is investigated. The effect of insulation layer material and thickness on CMUT performance is evaluated using a simple parallel plate model. The model shows that both high dielectric constant and the electrical breakdown strength are important for the dielectric material, and significant performance improvement can be achieved, especially as the vacuum gap thickness is reduced. In particular, ALD hafnium oxide (HfO2) is evaluated and used as an improvement over plasma-enhanced chemical vapor deposition (PECVD) silicon nitride (Six)Ny)) for CMUTs fabricated by a low-temperature, complementary metal oxide semiconductor transistor-compatible, sacrificial release method. Relevant properties of ALD HfO2) such as dielectric constant and breakdown strength are characterized to further guide CMUT design. Experiments are performed on parallel fabricated test CMUTs with 50-nm gap and 16.5-MHz center frequency to measure and compare pressure output and receive sensitivity for 200-nm PECVD Six)Ny) and 100-nm HfO2) insulation layers. Results for this particular design show a 6-dB improvement in receiver output with the collapse voltage reduced by one-half; while in transmit mode, half the input voltage is needed to achieve the same maximum output pressure. PMID:25474786

  16. 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).

  17. 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

  18. 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).

  19. Integration of atomic layer deposited high-k dielectrics on GaSb via hydrogen plasma exposure

    Directory of Open Access Journals (Sweden)

    Laura B. Ruppalt

    2014-12-01

    Full Text Available In this letter we report the efficacy of a hydrogen plasma pretreatment for integrating atomic layer deposited (ALD high-k dielectric stacks with device-quality p-type GaSb(001 epitaxial layers. Molecular beam eptiaxy-grown GaSb surfaces were subjected to a 30 minute H2/Ar plasma treatment and subsequently removed to air. High-k HfO2 and Al2O3/HfO2 bilayer insulating films were then deposited via ALD and samples were processed into standard metal-oxide-semiconductor (MOS capacitors. The quality of the semiconductor/dielectric interface was probed by current-voltage and variable-frequency admittance measurements. Measurement results indicate that the H2-plamsa pretreatment leads to a low density of interface states nearly independent of the deposited dielectric material, suggesting that pre-deposition H2-plasma exposure, coupled with ALD of high-k dielectrics, may provide an effective means for achieving high-quality GaSb MOS structures for advanced Sb-based digital and analog electronics.

  20. Spectroscopic atom symbolism

    International Nuclear Information System (INIS)

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

  1. Radiation effects in the WWR-K and BN-350 atomic reactors construction materials

    International Nuclear Information System (INIS)

    The brief review of the research works in the field of reactor material testing fulfilled at the Institute of Nuclear Physics of the National Nuclear Center of the Republic of Kazakhstan for the last years is given. The principal attention was paid to consideration of structure change and mechanical properties of stainless steels and alloys (12Cr18Ni10Ti, 08Cr16Ni11Mo3Ti, 12Cr13Mo2BFR, Cr16Ni15Mo3T, Cr20Ni45Mo4BRTs, SAV-1), as well as pure metals (Cu, Ni, Mo, Nb, Fe), irradiated at the WWR-K and BN-350 reactors or implanted by helium at the U-150 cyclotron. For these operations fulfilling the automation multipurpose experimental equipment complex with distance control was implemented. The complex provides to conduction of precision mechanical tests and simultaneously determine the valid strength parameters and plasticity, magnetization change, thermal effects accompanying the deformation process, and etc. The microstructure change examination of the each irradiated and deformed material were carried out with help of metallographic, as well as scanning and transmission electron microscopy. In this paper basically three radiation effects (hardening, embrittlement and corrosion) accompanying processes and following irradiated materials storage are considered

  2. 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

  3. Measurement of atomic-hydrogen spin-exchange parameters at 0.5 K using a cryogenic hydrogen maser

    International Nuclear Information System (INIS)

    Using a cryogenic hydrogen maser, suitably modified to have electronic control of both the resonance frequency and the quality factor of the external cavity, we have measured a number of spin-exchange parameters for an atomic-hydrogen (H) gas at a temperature of 0.5 K. These results are relevant to the ultimate achievable frequency stability for cryogenic H masers and, when coupled with accurate calculations of the spin-exchange parameters, serve as a sensitive test of the H-H interatomic potentials. We find evidence for a frequency shift not predicted by semiclassical theories of spin exchange. In the context of a fully quantum mechanical hydrogen-atom spin-exchange theory [B. J. Verhaar et al., Phys. Rev. A 35, 3825 (1987) and J. M. V. A. Koelman et al., Phys. Rev. A 38, 3535 (1988)], this frequency shift is attributed to the influence of hyperfine interactions during spin-exchange collisions. Our findings are generally in agreement with these predictions; however, the sign of the hyperfine-induced frequency shift appears to differ from theory. copyright 1996 The American Physical Society

  4. Seeding Atomic Layer Deposition of High-k Dielectrics on Epitaxial Graphene with Organic Self-assembled Monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Alaboson, Justice M. P.; Wang, Qing Hua; Emery, J.D.; Lipson, Albert L; Bedzyk, M.J.; Elam, Jeffrey W.; Pellin, Michael J.; Hersam, Mark C.

    2011-06-28

    The development of high-performance graphene-based nanoelectronics requires the integration of ultrathin and pinhole-free high-k dielectric films with graphene at the wafer scale. Here, we demonstrate that self-assembled monolayers of perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) act as effective organic seeding layers for atomic layer deposition (ALD) of HfO₂ and Al₂O₃ on epitaxial graphene on SiC(0001). The PTCDA is deposited via sublimation in ultrahigh vacuum and shown to be highly ordered with low defect density by molecular-resolution scanning tunneling microscopy. Whereas identical ALD conditions lead to incomplete and rough dielectric deposition on bare graphene, the chemical functionality provided by the PTCDA seeding layer yields highly uniform and conformal films. The morphology and chemistry of the dielectric films are characterized by atomic force microscopy, ellipsometry, cross-sectional scanning electron microscopy, and X-ray photoelectron spectroscopy, while high-resolution X-ray reflectivity measurements indicate that the underlying graphene remains intact following ALD. Using the PTCDA seeding layer, metal-oxide-graphene capacitors fabricated with a 3 nm Al₂O₃ and 10 nm HfO₂ dielectric stack show high capacitance values of ~700 nF/cm² and low leakage currents of ~5 × 10{sup –9} A/cm² at 1 V applied bias. These results demonstrate the viability of sublimated organic self-assembled monolayers as seeding layers for high-k dielectric films in graphene-based nanoelectronics.

  5. Seeding atomic layer deposition of high-k dielectrics on epitaxial graphene with organic self-assembled monolayers.

    Science.gov (United States)

    Alaboson, Justice M P; Wang, Qing Hua; Emery, Jonathan D; Lipson, Albert L; Bedzyk, Michael J; Elam, Jeffrey W; Pellin, Michael J; Hersam, Mark C

    2011-06-28

    The development of high-performance graphene-based nanoelectronics requires the integration of ultrathin and pinhole-free high-k dielectric films with graphene at the wafer scale. Here, we demonstrate that self-assembled monolayers of perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) act as effective organic seeding layers for atomic layer deposition (ALD) of HfO(2) and Al(2)O(3) on epitaxial graphene on SiC(0001). The PTCDA is deposited via sublimation in ultrahigh vacuum and shown to be highly ordered with low defect density by molecular-resolution scanning tunneling microscopy. Whereas identical ALD conditions lead to incomplete and rough dielectric deposition on bare graphene, the chemical functionality provided by the PTCDA seeding layer yields highly uniform and conformal films. The morphology and chemistry of the dielectric films are characterized by atomic force microscopy, ellipsometry, cross-sectional scanning electron microscopy, and X-ray photoelectron spectroscopy, while high-resolution X-ray reflectivity measurements indicate that the underlying graphene remains intact following ALD. Using the PTCDA seeding layer, metal-oxide-graphene capacitors fabricated with a 3 nm Al(2)O(3) and 10 nm HfO(2) dielectric stack show high capacitance values of ∼700 nF/cm(2) and low leakage currents of ∼5 × 10(-9) A/cm(2) at 1 V applied bias. These results demonstrate the viability of sublimated organic self-assembled monolayers as seeding layers for high-k dielectric films in graphene-based nanoelectronics. PMID:21553842

  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. K-shell photoabsorption and photoionisation of trace elements. I. Isoelectronic sequences with electron number 3 ≤N ≤ 11

    Science.gov (United States)

    Palmeri, P.; Quinet, P.; Mendoza, C.; Bautista, M. A.; Witthoeft, M. C.; Kallman, T. R.

    2016-04-01

    Context. With the recent launching of the Hitomi X-ray space observatory, K lines and edges of chemical elements with low cosmic abundances, namely F, Na, P, Cl, K, Sc, Ti, V, Cr, Mn, Co, Cu and Zn, can be resolved and used to determine important properties of supernova remnants, galaxy clusters and accreting black holes and neutron stars. Aims: The second stage of the present ongoing project involves the computation of the accurate photoabsorption and photoionisation cross sections required to interpret the X-ray spectra of such trace elements. Methods: Depending on target complexity and computer tractability, ground-state cross sections are computed either with the close-coupling Breit-Pauli R-matrix method or with the autostructure atomic structure code in the isolated-resonance approximation. The intermediate-coupling scheme is used whenever possible. In order to determine a realistic K-edge behaviour for each species, both radiative and Auger dampings are taken into account, the latter being included in the R-matrix formalism by means of an optical potential. Results: Photoabsorption and total and partial photoionisation cross sections are reported for isoelectronic sequences with electron numbers 3 ≤ N ≤ 11. The Na sequence (N = 11) is used to estimate the contributions from configurations with a 2s hole (i.e. [2s]μ) and those containing 3d orbitals, which will be crucial when considering sequences with N > 11. Conclusions: It is found that the [2s]μ configurations must be included in the target representations of species with N ≥ 11 as they contribute significantly to the monotonic background of the cross section between the L and K edges. Configurations with 3d orbitals are important in rendering an accurate L edge, but they can be practically neglected in the K-edge region.

  8. Evidence for ultra-fast outflows in radio-quiet AGNs: I - detection and statistical incidence of Fe K-shell absorption lines

    CERN Document Server

    Tombesi, F; Reeves, J N; Palumbo, G G C; Yaqoob, T; Braito, V; Dadina, M

    2010-01-01

    We performed a blind search for narrow absorption features at energies greater than 6.4 keV in a sample of 42 radio-quiet AGNs observed with XMM-Newton. We detect 36 narrow absorption lines on a total of 101 XMM-Newton EPIC pn observations. The number of absorption lines at rest-frame energies E>7 keV is 22. Their global probability to be generated by random fluctuations is very low, less than 3x10^-8, and their detection have been independently confirmed by a spectral analysis of the MOS data, with associated random probability <10^-7. We identify the lines as Fe XXV and Fe XXVI K-shell resonant absorption. They are systematically blue-shifted, with a velocity distribution ranging from zero up to 0.3c, with a peak and mean value at 0.1c. We detect variability of the lines on both EWs and blue-shifted velocities among different observations even on time-scales as short as a few days, possibly suggesting somewhat compact absorbers. Moreover, we find no significant correlation between the cosmological red-sh...

  9. Reply on "Comments on 'Time modulation of the K-shell electron capture decay rates of H-like heavy ions at GSI experiments'"

    CERN Document Server

    Ivanov, A N

    2009-01-01

    According to experimental data at GSI, the rates of the number of daughter ions, produced by the nuclear K-shell electron capture (EC) decays of the H-like 140Pr58+, 142Pm60+ and 122I52+ ions, are modulated in time with periods T_{EC} of the order of a few seconds, obeying an A-scaling T_{EC} = A/20 s, where A is the mass number of the mother nuclei, and with amplitudes a^{EC}_d ~ 0.21. In turn, the positron decay mode of the H-like 142Pm60+ ions showed no time modulation of the decay rates. As has been shown in Phys. Rev. Lett. 103, 062502 (2009) and Phys. Rev. Lett. 101, 182501 (2008), these data can be explained by the interference of two neutrino mass-eigenstates. In this letter we give a reply on the comments on our paper Phys. Rev. Lett. 103, 062502 (2009) by V. Flambaum (arXiv: 0908.2039 [nucl-th]).

  10. 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

  11. Effect of atomic-arrangement matching on La2O3/Ge heterostructures for epitaxial high-k-gate-stacks

    Science.gov (United States)

    Kanashima, T.; Nohira, H.; Zenitaka, M.; Kajihara, Y.; Yamada, S.; Hamaya, K.

    2015-12-01

    We demonstrate a high-quality La2O3 layer on germanium (Ge) as an epitaxial high-k-gate-insulator, where there is an atomic-arrangement matching condition between La2O3(001) and Ge(111). Structural analyses reveal that (001)-oriented La2O3 layers were grown epitaxially only when we used Ge(111) despite low growth temperatures less than 300 °C. The permittivity (k) of the La2O3 layer is roughly estimated to be ˜19 from capacitance-voltage (C-V) analyses in Au/La2O3/Ge structures after post-metallization-annealing treatments, although the C-V curve indicates the presence of carrier traps near the interface. By using X-ray photoelectron spectroscopy analyses, we find that only Ge-O-La bonds are formed at the interface, and the thickness of the equivalent interfacial Ge oxide layer is much smaller than that of GeO2 monolayer. We discuss a model of the interfacial structure between La2O3 and Ge(111) and comment on the C-V characteristics.

  12. Effect of atomic-arrangement matching on La2O3/Ge heterostructures for epitaxial high-k-gate-stacks

    International Nuclear Information System (INIS)

    We demonstrate a high-quality La2O3 layer on germanium (Ge) as an epitaxial high-k-gate-insulator, where there is an atomic-arrangement matching condition between La2O3(001) and Ge(111). Structural analyses reveal that (001)-oriented La2O3 layers were grown epitaxially only when we used Ge(111) despite low growth temperatures less than 300 °C. The permittivity (k) of the La2O3 layer is roughly estimated to be ∼19 from capacitance-voltage (C-V) analyses in Au/La2O3/Ge structures after post-metallization-annealing treatments, although the C-V curve indicates the presence of carrier traps near the interface. By using X-ray photoelectron spectroscopy analyses, we find that only Ge–O–La bonds are formed at the interface, and the thickness of the equivalent interfacial Ge oxide layer is much smaller than that of GeO2 monolayer. We discuss a model of the interfacial structure between La2O3 and Ge(111) and comment on the C-V characteristics

  13. Measurement of the gold–gold bond rupture force at 4 K in a single-atom chain using photon-momentum-based force calibration

    International Nuclear Information System (INIS)

    We present instrumentation and methodology for simultaneously measuring force and displacement at the atomic scale at 4 K. The technique, which uses a macroscopic cantilever as a force sensor and high-resolution, high-stability fiber-optic interferometers for displacement measurement, is particularly well-suited to making accurate, traceable measurements of force and displacement in nanometer- and atomic-scale mechanical deformation experiments. The technique emphasizes accurate co-location of force and displacement measurement and measures cantilever stiffness at the contact point in situ at 4 K using photon momentum. We present preliminary results of measurements made of the force required to rupture a single atomic bond in a gold single-atom chain formed between a gold flat and a gold tip. Finally, we discuss the possible use of the gold–gold bond rupture force as an intrinsic force calibration value for forces near 1 nN. (paper)

  14. First-principles study of ternary graphite compounds cointercalated with alkali atoms (Li, Na, and K) and alkylamines towards alkali ion battery applications

    Science.gov (United States)

    Ri, Gum-Chol; Yu, Chol-Jun; Kim, Jin-Song; Hong, Song-Nam; Jong, Un-Gi; Ri, Mun-Hyok

    2016-08-01

    First-principles calculations were carried out to investigate the structural, energetic, and electronic properties of ternary graphite compounds cointercalated with alkali atoms (AM = Li, Na, and K) and normal alkylamine molecules (nCx; x = 1, 2, 3, 4), denoted as AM-nCx-GICs. From the optimization of the orthorhombic unit cells for the crystalline compounds, it was found that, with the increase in the atomic number of alkali atoms, the layer separations decrease in contrast to AM-GICs, while the bond lengths between alkali atoms and graphene layer, and nitrogen atom of alkylamine increase. The calculated formation energies and interlayer binding energies of AM-nC3-GICs indicate that the compounds is increasingly stabilized from Li to K, and the energy barriers for migration of alkali atoms suggest that alkali cation with larger ionic radius diffuses more smoothly in graphite, being similar to AM-GICs. Through the analysis of electronic properties, it was established that more extent of electronic charge is transferred from more electropositive alkali atom to the carbon ring of graphene layer, and the hybridization of valence electron orbitals between alkylamine molecules and graphene layer is occurred.

  15. EVIDENCE FOR ULTRA-FAST OUTFLOWS IN RADIO-QUIET ACTIVE GALACTIC NUCLEI. II. DETAILED PHOTOIONIZATION MODELING OF Fe K-SHELL ABSORPTION LINES

    International Nuclear Information System (INIS)

    X-ray absorption line spectroscopy has recently shown evidence for previously unknown Ultra-fast Outflows (UFOs) in radio-quiet active galactic nuclei (AGNs). These have been detected essentially through blueshifted Fe XXV/XXVI K-shell transitions. In the previous paper of this series we defined UFOs as those highly ionized absorbers with an outflow velocity higher than 10,000 km s–1 and assessed the statistical significance of the associated blueshifted absorption lines in a large sample of 42 local radio-quiet AGNs observed with XMM-Newton. The present paper is an extension of that work. First, we report a detailed curve of growth analysis of the main Fe XXV/XXVI transitions in photoionized plasmas. Then, we estimate an average spectral energy distribution for the sample sources and directly model the Fe K absorbers in the XMM-Newton spectra with the detailed Xstar photoionization code. We confirm that the frequency of sources in the radio-quiet sample showing UFOs is >35% and that the majority of the Fe K absorbers are indeed associated with UFOs. The outflow velocity distribution spans from ∼10,000 km s–1 (∼0.03c) up to ∼100,000 km s–1 (∼0.3c), with a peak and mean value of ∼42,000 km s–1 (∼0.14c). The ionization parameter is very high and in the range log ξ ∼ 3-6 erg s–1 cm, with a mean value of log ξ ∼ 4.2 erg s–1 cm. The associated column densities are also large, in the range NH ∼ 1022-1024 cm–2, with a mean value of NH ∼ 1023 cm–2. We discuss and estimate how selection effects, such as those related to the limited instrumental sensitivity at energies above 7 keV, may hamper the detection of even higher velocities and higher ionization absorbers. We argue that, overall, these results point to the presence of extremely ionized and possibly almost Compton-thick outflowing material in the innermost regions of AGNs. This also suggests that UFOs may potentially play a significant role in the expected cosmological feedback

  16. Evidence for Ultra-fast Outflows in Radio-quiet Active Galactic Nuclei. II. Detailed Photoionization Modeling of Fe K-shell Absorption Lines

    Science.gov (United States)

    Tombesi, F.; Cappi, M.; Reeves, J. N.; Palumbo, G. G. C.; Braito, V.; Dadina, M.

    2011-11-01

    X-ray absorption line spectroscopy has recently shown evidence for previously unknown Ultra-fast Outflows (UFOs) in radio-quiet active galactic nuclei (AGNs). These have been detected essentially through blueshifted Fe XXV/XXVI K-shell transitions. In the previous paper of this series we defined UFOs as those highly ionized absorbers with an outflow velocity higher than 10,000 km s-1 and assessed the statistical significance of the associated blueshifted absorption lines in a large sample of 42 local radio-quiet AGNs observed with XMM-Newton. The present paper is an extension of that work. First, we report a detailed curve of growth analysis of the main Fe XXV/XXVI transitions in photoionized plasmas. Then, we estimate an average spectral energy distribution for the sample sources and directly model the Fe K absorbers in the XMM-Newton spectra with the detailed Xstar photoionization code. We confirm that the frequency of sources in the radio-quiet sample showing UFOs is >35% and that the majority of the Fe K absorbers are indeed associated with UFOs. The outflow velocity distribution spans from ~10,000 km s-1 (~0.03c) up to ~100,000 km s-1 (~0.3c), with a peak and mean value of ~42,000 km s-1 (~0.14c). The ionization parameter is very high and in the range log ξ ~ 3-6 erg s-1 cm, with a mean value of log ξ ~ 4.2 erg s-1 cm. The associated column densities are also large, in the range N H ~ 1022-1024 cm-2, with a mean value of N H ~ 1023 cm-2. We discuss and estimate how selection effects, such as those related to the limited instrumental sensitivity at energies above 7 keV, may hamper the detection of even higher velocities and higher ionization absorbers. We argue that, overall, these results point to the presence of extremely ionized and possibly almost Compton-thick outflowing material in the innermost regions of AGNs. This also suggests that UFOs may potentially play a significant role in the expected cosmological feedback from AGNs and their study can

  17. Detection of atomic surface structure on NbSe2 and NbSe3 at 77 and 4.2 K using scanning tunneling microscopy

    International Nuclear Information System (INIS)

    Scanning tunneling microscopy (STM) studies have been performed on NbSe2 and NbSe3 at 77 and 4.2 K. The surface atomic structure has been clearly resolved, but evidence of charge-density wave (CDW) modulation has only been observed at 4.2 K in NbSe3. CDW's exist in NbSe2 at 4.2 K and in NbSe3 at 77 K, but the CDW amplitude is either too small or is screened by the remaining conduction electrons. The linear chain structure in NbSe3 has been clearly resolved and the STM profiles are dominated by the heights and effective charges of the surface Se atoms. Improved sensitivity and resolution will be required to study any details of the CDW structure in both compounds

  18. Characteristics of plutonium and americium contamination at the former U.K. atomic weapons test ranges at Maralinga and Emu

    Energy Technology Data Exchange (ETDEWEB)

    Burns, P.A.; Cooper, M.B.; Lokan, K.H.; Wilks, M.J.; Williams, G.A. [Australian Radiation Lab., Melbourne, VIC (Australia)

    1995-11-01

    Physico-chemical studies on environmental plutonium are described, which provide data integral to an assessment of dose for the inhalation of artificial actinides by Australian Aborigines living a semi-traditional lifestyle at Maralinga and Emu, sites of U.K. atomic weapons tests between 1953 and 1963. The most significant area, from a radiological perspective, is the area contaminated by plutonium in a series of ``one point`` safety trials in which large quantities of plutonium were dispersed explosively at a location known as Taranaki. The activity distribution of plutonium and americium with particle size is quite different from the mass distribution, as a considerably higher proportion of the activity is contained in the finer (inhalable) fraction than of the mass. Except in areas which were disturbed through ploughing during a cleanup in 1967, most the activity remains in the top 1 cm of the surface. Much of the activity is in particulate form, even at distances > 20 km from the firing sites, and discrete particles have been located even at distances beyond 100 km. Data are presented which permit the assessment of annual committed doses through the inhalation pathway, for Aborigines living a semi-traditional lifestyle in the areas affected by the Taranaki firings in particular. (author).

  19. Characteristics of plutonium and americium contamination at the former U.K. atomic weapons test ranges at Maralinga and Emu

    International Nuclear Information System (INIS)

    Physico-chemical studies on environmental plutonium are described, which provide data integral to an assessment of dose for the inhalation of artificial actinides by Australian Aborigines living a semi-traditional lifestyle at Maralinga and Emu, sites of U.K. atomic weapons tests between 1953 and 1963. The most significant area, from a radiological perspective, is the area contaminated by plutonium in a series of ''one point'' safety trials in which large quantities of plutonium were dispersed explosively at a location known as Taranaki. The activity distribution of plutonium and americium with particle size is quite different from the mass distribution, as a considerably higher proportion of the activity is contained in the finer (inhalable) fraction than of the mass. Except in areas which were disturbed through ploughing during a cleanup in 1967, most the activity remains in the top 1 cm of the surface. Much of the activity is in particulate form, even at distances > 20 km from the firing sites, and discrete particles have been located even at distances beyond 100 km. Data are presented which permit the assessment of annual committed doses through the inhalation pathway, for Aborigines living a semi-traditional lifestyle in the areas affected by the Taranaki firings in particular. (author)

  20. Stereo and scanning electron microscopy of in-shell Brazil nut (Bertholletia excelsa H.B.K.): part two-surface sound nut fungi spoilage susceptibility.

    Science.gov (United States)

    Scussel, Vildes M; Manfio, Daniel; Savi, Geovana D; Moecke, Elisa H S

    2014-11-01

    This work reports the in-shell Brazil nut spoilage susceptible morpho-histological characteristics and fungi infection (shell, edible part, and brown skin) through stereo and scanning electron microscopies (SEM). The following characteristics related to shell (a) morphology-that allow fungi and insects' entrance to inner nut, and (b) histology-that allow humidity absorption, improving environment conditions for living organisms development, were identified. (a.1) locule in testae-the nut navel, which is a cavity formed during nut detaching from pods (located at 1.0 to 2.0/4th of the shell B&C nut faces linkage). It allows the nut brown skin (between shell and edible part) first contact to the external environment, through the (a.2) nut channel-the locule prolongation path, which has the water/nutrients cambium function for their transport and distribution to the inner seed (while still on the tree/pod). Both, locule followed by the channel, are the main natural entrance of living organisms (fungi and insects), including moisture to the inner seed structures. In addition, the (a.3) nut shell surface-which has a crinkled and uneven surface morphology-allows water absorption, thus adding to the deterioration processes too. The main shell histological characteristic, which also allows water absorption (thus improving environment conditions for fungi proliferation), is the (b.1) cell wall porosity-the multilayered wall and porous rich cells that compose the shell faces double tissue layers and the (b.2) soft tissue-the mix of tissues 2 faces corner/linkage. This work also shows in details the SEM nut spoilage susceptible features highly fungi infected with hyphae and reproductive structures distribution. PMID:25318846

  1. Reduction of in-shell Brazil nut (Bertholletia excelsa H.B.K.) aflatoxin contamination by ozone gas application during storage

    OpenAIRE

    Giordano, B. N. E.; Simao, V.; Manfio, D.; Galvao, S.; Scussel, J. N.; Scussel, V. M.

    2010-01-01

    The susceptibility of the in-shell Brazil nut mycoflora and aflatoxins (AFLs) contamination to ozone (O₃) gas during storage is reported. In-shell Brazil nuts obtained from retail market were submitted to O₃ gas atmosphere at different concentrations immediately before to be stored. Samples were collected just after the gas exposure and every 30 days during the storage period to carry on mycological tests and AFLs analysis. A sensorial evaluation by descriptive quality analysis was carried ou...

  2. Observation of K-shell soft X ray emission of nitrogen irradiated by XUV Free Electron Laser FLASH at intensities greater than 10{sup 16} W/cm{sup 2}

    Energy Technology Data Exchange (ETDEWEB)

    Galtier, E. [Universite Pierre et Marie Curie, UPMC, Paris (France); Rosmej, F.B. [Universite Pierre et Marie Curie, UPMC, Paris (France)] [Laboratoire pour l' Utilisation des Lasers Intenses, LULI, Palaiseau (France); White, S.; Riley, D. [Queen' s University of Belfast, Belfast (United Kingdom); Vinko, S.M.; Witcher, T. [Department of Physics, Clarendon Laboratory, University of Oxford, Oxford (United Kingdom); Nagler, B. [SLAC National Accelerator Laboratory, California (United States); Nelson, A.J.; Lee, R.W. [Lawrence Livermore National Laboratory, California (United States); Chalupsky, J.; Renner, O.; Juha, L. [Academy of Sciences of the Czech Republic, Prague (Country Unknown); Toleikis, S. [Deutsches Elektronen - Synchrotron DESY, Hamburg (Germany); Gauthier, J.C. [Centre Lasers Intenses et Applications, CELIA, Bordeaux (France)

    2011-07-01

    In the past few years, the development of light sources of the fourth generation, namely XUV/X - ray Free Electron Lasers provides to the scientific community with outstanding tools to investigate matter under extreme conditions never obtained in laboratories so far. As theory is at its infancy the analysis of matter via the self - emission of the target is of central importance for this research. In order to minimize absorption to have photons which exit the dense matter, K-shell X-ray transitions play a key role. We report here about the first successful observation of K-shell emission of nitrogen using an XUV - Free Electron laser to irradiate solid BN-targets under exceptional conditions: photon energy of 92 eV, pulse duration of 15 fs, micro-focussing and intensities larger than 10{sup 16} W/cm{sup 2}. Using a Bragg crystal THM coupled to a CCD, we resolved K-shell line emission from different charge states. We demonstrate that the K-shell data allow the characterization of electron heating processes when X-ray radiation is interacting with solid matter. As energy transport is non-trivial because the light source is monochromatic, these results have important impact to theory. We also present data that show significant variation in dependence of the laser intensity, this permits quantitative characterization of the electron temperature: about 100 eV are deduced. The high electron temperatures seem to be in contradiction with the theory of pure Auger electron heating. This document is composed of an abstract followed by the slides of the presentation. (authors)

  3. Calculations of electron screening in muonic atoms

    International Nuclear Information System (INIS)

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

  4. 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

  5. Evolution of three-shell onion-like and core-shell structures in (AgCo)201 bimetallic clusters

    Institute of Scientific and Technical Information of China (English)

    Wang Qiang; Li Guo-Jian; Li Dong-Gang; Lv Xiao; He Ji-Cheng

    2009-01-01

    This paper studies the structural evolution of (AgCo)201 clusters with different Co concentrations under various temperature conditions by using molecular dynamics with the embedded atom method. The most stable position for Co atoms in the cluster is the subsurface layer at low temperature (lower than 200 K for the Ag200Co1 cluster). The position changes to the core layer with the increase of temperature, but there is an energy barrier in the middle layer. This makes the Ag-Co cluster form an Ag-Co-Ag three-shell onion-like configuration. When the temperature is high enough [higher than 800 K for (AgCo)201 clusters with 50% Co], Co atoms can obtain enough energy to overcome the energy barrier and the duster forms an Ag-Co core-shell configuration. Amorphization for the onion-like and core-shell clusters is induced by the large lattice misfit at Ag-Co interfaces. The structural evolution in the Ag-Co cluster is related to the release of excess energy.

  6. The formation of IRIS diagnostics I. A quintessential model atom of Mg II and general formation properties of the Mg II h&k lines

    CERN Document Server

    Leenaarts, J; Carlsson, M; Uitenbroek, H; de Pontieu, B

    2013-01-01

    NASA's Interface Region Imaging Spectrograph (IRIS) space mission will study how the solar atmosphere is energized. IRIS contains an imaging spectrograph that covers the Mg II h&k lines as well as a slit-jaw imager centered at Mg II k. Understanding the observations will require forward modeling of Mg II h&k line formation from 3D radiation-MHD models. This paper is the first in a series where we undertake this forward modeling. We discuss the atomic physics pertinent to h&k line formation, present a quintessential model atom that can be used in radiative transfer computations and discuss the effect of partial redistribution (PRD) and 3D radiative transfer on the emergent line profiles. We conclude that Mg II h&k can be modeled accurately with a 4-level plus continuum Mg II model atom. Ideally radiative transfer computations should be done in 3D including PRD effects. In practice this is currently not possible. A reasonable compromise is to use 1D PRD computations to model the line profile up ...

  7. Study of the selective abstration reaction of the hydrogen atom in the radiolysis and photolysis of alkane mixture at 77 K

    International Nuclear Information System (INIS)

    The occurence of the selective abstraction reaction of the solute hydrogen atom by hydrogen atom produced during radiolysis or photolysis of the systems such as neopentane/cyclo-hexane/HI, neopentane/2,3 dimethylbutane, n-pentane/HI/cyclo-hexane and cyclo-hexane/HI/n-pentane, at 77 K is studied. Experiments have been undertaken on the kinetics nature of the active species, the H atom, during radiolysis and photolysis of the neopentane/cyclo-hexane/HI system at 77 K, presenting competitive reactions. Studies have also been made on the occurrence of the selective abstraction reaction in inverted systems, in which the concentrations of the components of a system are so much altered that the solute becomes the solvent and vice-versa, in the other system. By means of photolysis at 77 K, it has been observed that for the two systems constitued by the cyclo-hexane and n-pentane the selective abstraction reaction occurs. However, for radiolysis of that same two systems it has been observed that only the hydrogen atom abstraction reaction corresponding to the solvent occurs. (Author)

  8. 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.

  9. Measurement of the K shell X-ray production cross-sections and fluorescence yields for Nd, Eu, Gd, Dy and Ho using radioisotope X-ray fluorescence in the external magnetic field

    International Nuclear Information System (INIS)

    The effect of external magnetic field on the Kα and Kβ X-ray production cross-sections and K shell fluorescence yields for ferromagnetic elements Nd, Gd and Dy and paramagnetic elements Eu and Ho have been measured at the excitation energy of 59.5 keV γ-rays from Am241 radioactive source of strength 100 mCi in the external magnetic field of intensities ± 0.75 T. Furthermore, I(Kβ)/I(Kα) intensity ratios for these elements have been measured in the external magnetic field. The K X-rays from different targets were detected using a high resolution Si(Li) semiconductor detector. For B = 0, the measured K X-ray production cross-sections, K shell fluorescence yields and the I(Kβ)/I(Kα) intensity ratios were compared with the experimental and theoretical data in literature. The results have shown that the fluorescence parameters as photoionization cross section, fluorescence yield, radiation rates and spectral linewidth can change when the irradiation is conducted in a magnetic field. (authors)

  10. 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...

  11. 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....

  12. Comparative band alignment of plasma-enhanced atomic layer deposited high-k dielectrics on gallium nitride

    Science.gov (United States)

    Yang, Jialing; Eller, Brianna S.; Zhu, Chiyu; England, Chris; Nemanich, Robert J.

    2012-09-01

    Al2O3 films, HfO2 films, and HfO2/Al2O3 stacked structures were deposited on n-type, Ga-face, GaN wafers using plasma-enhanced atomic layer deposition (PEALD). The wafers were first treated with a wet-chemical clean to remove organics and an in-situ combined H2/N2 plasma at 650 °C to remove residual carbon contamination, resulting in a clean, oxygen-terminated surface. This cleaning process produced slightly upward band bending of 0.1 eV. Additional 650 °C annealing after plasma cleaning increased the upward band bending by 0.2 eV. After the initial clean, high-k oxide films were deposited using oxygen PEALD at 140 °C. The valence band and conduction band offsets (VBOs and CBOs) of the Al2O3/GaN and HfO2/GaN structures were deduced from in-situ x-ray and ultraviolet photoemission spectroscopy (XPS and UPS). The valence band offsets were determined to be 1.8 and 1.4 eV, while the deduced conduction band offsets were 1.3 and 1.0 eV, respectively. These values are compared with the theoretical calculations based on the electron affinity model and charge neutrality level model. Moreover, subsequent annealing had little effect on these offsets; however, the GaN band bending did change depending on the annealing and processing. An Al2O3 layer was investigated as an interfacial passivation layer (IPL), which, as results suggest, may lead to improved stability, performance, and reliability of HfO2/IPL/GaN structures. The VBOs were ˜0.1 and 1.3 eV, while the deduced CBOs were 0.6 and 1.1 eV for HfO2 with respect to Al2O3 and GaN, respectively.

  13. Comparative band alignment of plasma-enhanced atomic layer deposited high-k dielectrics on gallium nitride

    International Nuclear Information System (INIS)

    Al2O3 films, HfO2 films, and HfO2/Al2O3 stacked structures were deposited on n-type, Ga-face, GaN wafers using plasma-enhanced atomic layer deposition (PEALD). The wafers were first treated with a wet-chemical clean to remove organics and an in-situ combined H2/N2 plasma at 650 °C to remove residual carbon contamination, resulting in a clean, oxygen-terminated surface. This cleaning process produced slightly upward band bending of 0.1 eV. Additional 650 °C annealing after plasma cleaning increased the upward band bending by 0.2 eV. After the initial clean, high-k oxide films were deposited using oxygen PEALD at 140 °C. The valence band and conduction band offsets (VBOs and CBOs) of the Al2O3/GaN and HfO2/GaN structures were deduced from in-situ x-ray and ultraviolet photoemission spectroscopy (XPS and UPS). The valence band offsets were determined to be 1.8 and 1.4 eV, while the deduced conduction band offsets were 1.3 and 1.0 eV, respectively. These values are compared with the theoretical calculations based on the electron affinity model and charge neutrality level model. Moreover, subsequent annealing had little effect on these offsets; however, the GaN band bending did change depending on the annealing and processing. An Al2O3 layer was investigated as an interfacial passivation layer (IPL), which, as results suggest, may lead to improved stability, performance, and reliability of HfO2/IPL/GaN structures. The VBOs were ∼0.1 and 1.3 eV, while the deduced CBOs were 0.6 and 1.1 eV for HfO2 with respect to Al2O3 and GaN, respectively.

  14. 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.

  15. 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

  16. Rate coefficients for hydrogen abstraction reaction of pinonaldehyde C10H16O2 with Cl atoms between 200 and 400 K: A DFT study

    Indian Academy of Sciences (India)

    G SRINIVASULU; B RAJAKUMAR

    2016-06-01

    The kinetics of the reaction between pinonaldehyde C10H16O2 and Cl atom were studied usinghigh level ab initio G3(MP2) and DFT based MPWB1K/6-31+G(d) and MPW1K/6-31+G(d) levels of theoriescoupled with Conventional Transition State Theory in the temperature range between 200 and 400 K. Thenegative temperature dependent rate expression for the title reaction obtained with Wigner’s and Eckart’s symmetricaltunneling corrections are k(T)=(5.1 ± 0.56) × 10−19T2.35exp[(2098 ± 2)/T] cm3 molecule-1 s-1, and k(T)=(0.92 ± 0.18) × 10-19T2.60exp[(2204 ± 4)/T] cm3 molecule-1 s-1, respectively, at G3(MP2)//MPWB1Kmethod. The H abstraction reaction from the –CHO group was found to be the most dominant reaction channelamong all the possible reaction pathways and its corresponding rate coefficient at 300 K is kEckart’s unsymmetrical= 3.86 ×10-10 cm3 molecule-1 s-1. Whereas the channel with immediate lower activation energy is the H-abstraction from –CH- group (Tertiary H-abstraction site, Cg). The rate coefficient for this channel is kCg(Eckart’s unsymmetrical) = 1.83 ×10-15 cm3 molecule-1 s-1 which is smaller than the dominant channel byfive orders of magnitude. The atmospherically relevant parameters such as lifetimes were computed in thisinvestigation of its reaction with Cl atom.

  17. Transient x-ray absorption spectroscopy of hydrated halogen atom

    CERN Document Server

    Elles, Christopher G; Crowell, Robert A; Arms, Dohn A; Landahl, Eric C

    2007-01-01

    Time-resolved x-ray absorption spectroscopy monitors the transient species generated by one-photon detachment of an electron from aqueous bromide. Hydrated bromine atoms with a lifetime of ca. 17 ns were observed, nearly half of which react with excess Br- to form Br2-. The K-edge spectra of the Br atom and Br2- anion exhibit distinctive resonant transitions that are absent for the Br- precursor. The absorption spectra indicate that the solvent shell around a Br0 atom is defined primarily by hydrophobic interactions, in agreement with a Monte Carlo simulation of the solvent structure.

  18. 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.

  19. Evolution of structural properties of iron oxide nano particles during temperature treatment from 250{\\deg}C - 900{\\deg}C: X-ray diffraction and Fe K-shell pre-edge X-ray absorption study

    OpenAIRE

    Bora, Debajeet K.; Braun, Artur; Erat, Selma; Safonova, Olga; Graule, Thomas; Constable, Edwin C.

    2011-01-01

    Iron oxide nano particles with nominal Fe2O3 stoichiometry were synthesized by a wet, soft chemical method with the heat treatment temperatures from 250{\\deg}C to 900{\\deg}C in air. The variation in the structural properties of the nano particles with the heat treatment temperature was studied by X-ray diffraction and Fe K shell X-ray absorption study. X-ray diffractograms show that at lower annealing temperatures nano particle comprises both maghemite and hematite phases. With increasing tem...

  20. 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...

  1. 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)

  2. Absorption spectrum of very low pressure atomic hydrogen

    CERN Document Server

    Moret-Bailly, Jacques

    2015-01-01

    Spectra of quasars result primarily from interactions of natural light with atomic hydrogen. A visible absorption of a sharp and saturated spectral line in a gas requires a low pressure, so a long path without blushing as a cosmological redshift. Burbidge and Karlsson observed that redshifts of quasars result from fundamental redshifts, written 3K and 4K, that cause a shift of absorbed beta and gamma lines of H to alpha gas line. Thus absorbed spectrum is shifted until an absorbed line overlaps with Lyman alpha line of gas: redshift only occurs if an alpha absorption pumps atoms to 2P state. Thus, space is divided into spherical shells centered on the quasar, containing or not 2P atoms. Neglecting collisional de-excitations in absorbing shells, more and more atoms are excited until amplification of a beam having a long path in a shell, thus perpendicular to the observed ray, is large enough for a superradiant flash at alpha frequency. Energy is provided by atoms and observed ray, absorbing a line at local Lym...

  3. 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...

  4. Relativistic Calculation Of K$\\beta$ Hypersatellite Energies and Transition Probabilities for Selected Atoms with 13<=Z<=80

    CERN Document Server

    Costa, A M; Santos, J P; Indelicato, P J; Parente, F; Indelicato, Paul

    2006-01-01

    Energies and transition probabilities of K$\\beta$ hypersatellite lines are computed using the Dirac-Fock model for several values of $Z$ throughout the periodic table. The influence of the Breit interaction on the energy shifts from the corresponding diagram lines and on the K$\\beta\\_{1}^{\\rm h}$/K$\\beta\\_{3}^{\\rm h}$ intensity ratio is evaluated. The widths of the double-K hole levels are calculated for Al and Sc. The results are compared to experiment and to other theoretical calculations.

  5. Atomic Layer Deposition of a High-k Dielectric on MoS2 Using Trimethylaluminum and Ozone

    OpenAIRE

    Cheng, Lanxia; Qin, Xiaoye; Lucero, Antonio T.; Azcatl, Angelica; Huang, Jie; Wallace, Robert M.; Cho, Kyeongjae; Kim, Jiyoung

    2014-01-01

    We present an Al2O3 dielectric layer on molybdenum disulfide (MoS2), deposited using atomic layer deposition (ALD) with ozone/trimethylaluminum (TMA) and water/TMA as precursors. The results of atomic force microscopy and low-energy ion scattering spectroscopy show that using TMA and ozone as precursors leads to the formation of uniform Al2O3 layers, in contrast to the incomplete coverage we observe when using TMA/H2O as precursors. Our Raman and X-ray photoelectron spectroscopy measurements ...

  6. 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)

  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. Adiabatic Channel Capture Theory Applied to Cold Atom-Molecule Reactions: Li + CaH -> LiH + Ca at 1 K

    CERN Document Server

    Tscherbul, Timur V

    2014-01-01

    We use quantum and classical adiabatic capture theories to study the chemical reaction Li + CaH -> LiH + Ca. Using a recently developed ab initio potential energy surface, which provides an accurate representation of long-range interactions in the entrance reaction channel, we calculate the adiabatic channel potentials by diagonalizing the atom-molecule Hamiltonian as a function of the atom-molecule separation. The resulting adiabatic channel potentials are used to calculate both the classical and quantum capture probabilities as a function of collision energy, as well as the temperature dependencies of the partial and total reaction rates. The calculated reaction rate agrees well with the measured value at 1 K [V. Singh et al., Phys. Rev. Lett. 108, 203201 (2012)], suggesting that the title reaction proceeds without an activation barrier. The calculated classical adiabatic capture rate agrees well with the quantum result in the multiple partial wave regime of relevance to the experiment. Significant differen...

  9. Alternative evaluation of statistical indicators in atoms: The non-relativistic and relativistic cases

    International Nuclear Information System (INIS)

    In this work, the calculation of a statistical measure of complexity and the Fisher-Shannon information is performed for all the atoms in the periodic table. Non-relativistic and relativistic cases are considered. We follow the method suggested in [C.P. Panos, N.S. Nikolaidis, K.Ch. Chatzisavvas, C.C. Tsouros, (arXiv:0812.3963v1)] that uses the fractional occupation probabilities of electrons in atomic orbitals, instead of the continuous electronic wave functions. For the order of shell filling in the relativistic case, we take into account the effect due to electronic spin-orbit interaction. The increasing of both magnitudes, the statistical complexity and the Fisher-Shannon information, with the atomic number Z is observed. The shell structure and the irregular shell filling is well displayed by the Fisher-Shannon information in the relativistic case.

  10. Inner-shell ionization by relativistic radiation pressure

    International Nuclear Information System (INIS)

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

  11. Seeding atomic layer deposition of high-k dielectric on graphene with ultrathin poly(4-vinylphenol) layer for enhanced device performance and reliability

    Science.gov (United States)

    Cheol Shin, Woo; Yong Kim, Taek; Sul, Onejae; Jin Cho, Byung

    2012-07-01

    We demonstrate that ultrathin poly(4-vinylphenol) (PVP) acts as an effective organic seeding layer for atomic layer deposition (ALD) of high-k dielectric on large-scale graphene fabricated by chemical vapor deposition (CVD). While identical ALD conditions result in incomplete and rough dielectric deposition on CVD graphene, the reactive groups provided by the PVP seeding layer yield conformal and pinhole-free dielectric films throughout the large-scale graphene. Top-gate graphene field effect transistors fabricated with the high quality, PVP-seeded Al2O3 gate dielectric show superior carrier mobility and enhanced reliability performance, which are desirable for graphene nanoelectronics.

  12. Statistical disordering of chalcogen atoms in cluster fragments of K4[Re6(μ3-S)8-y(μ3-Te)y(CN)6

    International Nuclear Information System (INIS)

    X-ray diffraction investigation is conducted for three types of crystals of K4[Re6(μ3-S)8-y(μ3-Te)y(CN)6] - representatives of the continuous series of solid solutions prepared by high temperature reactions with the use of different initial substances. Syngony of the crystals is cubic, space group is Ia3. Statistical disordering of chalcogen atoms in cluster fragments [Re6(μ3-S)8-y(μ3-Te)y(CN)6] is investigated on data for three crystals. Results obtained show different effect of statistical disordering degree of Te and S on metric characteristics of the structures

  13. 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

  14. 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

  15. 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

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

    International Nuclear Information System (INIS)

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

  17. Atomic Structure of Au−Pd Bimetallic Alloyed Nanoparticles

    KAUST Repository

    Ding, Yong

    2010-09-08

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

  18. Determination of Ca, Mg, Na, Cd, Cu, Fe, K, Li and Zn in acid mine and reference water samples by inductively coupled plasma atomic fluorescence spectrometry

    Science.gov (United States)

    Sanzolone, R.F.; Meier, A.L.

    1986-01-01

    An inductively coupled plasma atomic fluorescence spectrometric (ICP-AFS) method was used for the determination of nine elements in natural water. Reference and acid mine water samples were analysed by this method to demonstrate its usefulness for hydrogeochemical exploration. The elements were determined in two groups based on the compatibility of operating conditions and consideration of element abundance levels in natural water. Ca, Mg and Na were determined as a group using one set of instrumental conditions and a 1 + 99 dilution of the sample, and Cd, Cu, Fe, K, Li and Zn were determined using another set of conditions and the undiluted sample. The detection limits for the elements are as follows: Ca, 1.4; Mg, 1.7; Na, 2.0; Cd, 1.8; Cu, 6.2; Fe, 15.8; K, 3.5; Li, 0.3; and Zn, 1.2 ng m1-1. Each element has a linear range spanning about four orders of magnitude. The method has good precision and accuracy, as shown by statistics on replicate analyses and by the agreement between values obtained and those recommended for the reference water samples, and also those obtained by atomic absorption spectrometry for the acid mine water samples.

  19. 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

  20. 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.

  1. Atomic and electronic structure of the Si(001)2x1-K chemisorption system at monolayer coverage

    International Nuclear Information System (INIS)

    Full text: It has been well established that the chemisorption of potassium on the Si (001) 2x1 surface leads to the so-called 'double-layer model' at one monolayer coverage. The plane wave pseudopotential density functional programs VASP and fhi98md have been used to optimise the geometry of this double-layer model. The resulting geometry has been found to be in excellent agreement with the experimental results. To identify the surface states of this double-layer model in the vicinity of the Fermi energy we have calculated the modulus squared of each wavefunction integrated over the surface unit cell. We have also calculated charge density contour plots over various planes containing the surface silicon and potassium atoms. The theoretically predicted dispersion of both the occupied and unoccupied surface states has been found to be in excellent agreement with the experimental data

  2. Tube-in-shell heat exchangers

    International Nuclear Information System (INIS)

    A tube-in-shell heat exchanger is described for use in liquid metal cooled fast breeder reactor constructions. The system consists of a bundle of heat exchange tubes with a central spine extending longitudinally through the shell and a series of longitudinally spaced transverse grids resiliently mounted on the central spine within the shell to provide transverse support for bracing the tubes apart. (U.K.)

  3. 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...

  4. 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)

  5. Proton induced K-shell ionization cross sections for a wide range of elements (4 ≤ Z ≤ 92 within ECPSSR theory and updated experimental data

    Directory of Open Access Journals (Sweden)

    B. Deghfel

    2014-10-01

    Full Text Available Within the individual treatment of the elements from beryllium (4Be to uranium (92U, the experimental databases are normalized to their corresponding values of the ECPSSR model to deduce the semi-empirical cross sections. These databases rely on the different compilations available in the literature and on the other data extracted from papers published from 1953 till 2010. In the present paper, a fourth order polynomial was used to fit very well the existing normalized database of K-shell ionization cross sections by proton. These procedures generate a new set of parameters for the sake of the quick calculation of the semi-empirical cross sections. A comparison is made between the deduced results and those obtained by using the ECPSSR model where a remarkable discrepancy is observed at low-proton velocity regime especially for the lightest elements.

  6. Lithography-Free Fabrication of Core-Shell GaAs Nanowire Tunnel Diodes.

    Science.gov (United States)

    Darbandi, A; Kavanagh, K L; Watkins, S P

    2015-08-12

    GaAs core-shell p-n junction tunnel diodes were demonstrated by combining vapor-liquid-solid growth with gallium oxide deposition by atomic layer deposition for electrical isolation. The characterization of an ensemble of core-shell structures was enabled by the use of a tungsten probe in a scanning electron microscope without the need for lithographic processing. Radial tunneling transport was observed, exhibiting negative differential resistance behavior with peak-to-valley current ratios of up to 3.1. Peak current densities of up to 2.1 kA/cm(2) point the way to applications in core-shell photovoltaics and tunnel field effect transistors. PMID:26189994

  7. 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

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

    CERN Document Server

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

    2014-01-01

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

  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. Role of ICAM-1 polymorphisms (G241R, K469E) in mediating its single-molecule binding ability: Atomic force microscopy measurements on living cells

    Energy Technology Data Exchange (ETDEWEB)

    Bai, Rui [Chinese (301) General Hospital, 28 Fuxing Road, Haidian District, Beijing 100853 (China); Yi, Shaoqiong [Beijing Institute of Biotechnology, 20 Dongdajie, Fengtai, Beijing 100071 (China); Zhang, Xuejie [Beijing National Laboratory for Molecular Sciences, Key Laboratory of Molecular Nanostructure and Nanotechnology, Institute of Chemistry Chinese Academy of Sciences, 2 Zhongguancun North 1st Street, Beijing 100190 (China); Liu, Huiliang, E-mail: lhl518@vip.sina.com [Department of Cardiology, The General Hospital of Chinese People’s Armed Police Forces, Beijing 100039 (China); Fang, Xiaohong, E-mail: xfang@iccas.ac.cn [Beijing National Laboratory for Molecular Sciences, Key Laboratory of Molecular Nanostructure and Nanotechnology, Institute of Chemistry Chinese Academy of Sciences, 2 Zhongguancun North 1st Street, Beijing 100190 (China)

    2014-06-13

    Highlights: • We evaluated both single molecule binding ability and expression level of 4 ICAM-1 mutations. • AFM was used to measure single-molecule binding ability on living cells. • The SNP of ICAM-1 may induce changes in expressions rather than single-molecule binding ability. - Abstract: Atherosclerosis (As) is characterized by chronic inflammation and is a major cause of human mortality. ICAM-1-mediated adhesion of leukocytes in vessel walls plays an important role in the pathogenesis of atherosclerosis. Two single nucleotide polymorphisms (SNPs) of human intercellular adhesion molecule-1 (ICAM-1), G241R and K469E, are associated with a number of inflammatory diseases. SNP induced changes in ICAM-1 function rely not only on the expression level but also on the single-molecule binding ability which may be affected by single molecule conformation variations such as protein splicing and folding. Previous studies have shown associations between G241R/K469E polymorphisms and ICAM-1 gene expression. Nevertheless, few studies have been done that focus on the single-molecule forces of the above SNPs and their ligands. In the current study, we evaluated both single molecule binding ability and expression level of 4 ICAM-1 mutations – GK (G241/K469), GE (G241/E469), RK (R241/K469) and RE (R241/E469). No difference in adhesion ability was observed via cell adhesion assay or atomic force microscopy (AFM) measurement when comparing the GK, GE, RK, or RE genotypes of ICAM-1 to each other. On the other hand, flow cytometry suggested that there was significantly higher expression of GE genotype of ICAM-1 on transfected CHO cells. Thus, we concluded that genetic susceptibility to diseases related to ICAM-1 polymorphisms, G241R or K469E, might be due to the different expressions of ICAM-1 variants rather than to the single-molecule binding ability of ICAM-1.

  11. 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.

  12. The feasibility of a sensitive low-dose method for the in vivo evaluation of Fe in skin using K-shell x-ray fluorescence (XRF)

    Science.gov (United States)

    Farquharson, Michael J.; Bradley, David A.

    1999-04-01

    An x-ray fluorescence (XRF) system designed for monitoring of skin Fe concentrations has been performance tested for use on patients treated for -thalassaemia. The essentials of the system are: a collimated x-ray tube operated at 20 kV and 20 mA; energy selection of the x-ray beam by means of a Cu K-edge filter; use of skin phantoms containing concentrations of Fe in the range 10 to 100 parts per million (ppm); and a high-purity germanium detector placed at to the incident beam. For a Cu K-edge filter of 0.15 mm thickness a quasi-monoenergetic beam of approximately 8.4 keV is obtained which is close to the absorption edge of Fe (7.11 keV). For a real-time counting period of 400 s the system is capable of detecting Fe concentrations of ppm at a skin dose of the order of 5 mSv. This level of Fe is at the higher end of the normal range found in the skin. In using the same system and operating parameters, measurements on a sample of ferritin obtained from a rat's liver yield an Fe concentration of ppm for a measurement time of 500 s; this can be compared with suppliers' data indicating an Fe level of 36 ppm.

  13. The feasibility of a sensitive low-dose method for the in vivo evaluation of Fe in skin using K-shell x-ray fluorescence (XRF)

    International Nuclear Information System (INIS)

    An x-ray fluorescence (XRF) system designed for monitoring of skin Fe concentrations has been performance tested for use on patients treated for β-thalassaemia. The essentials of the system are: a collimated x-ray tube operated at 20 kV and 20 mA; energy selection of the x-ray beam by means of a Cu K-edge filter; use of skin phantoms containing concentrations of Fe in the range 10 to 100 parts per million (ppm); and a high-purity germanium detector placed at 90 deg. to the incident beam. For a Cu K-edge filter of 0.15 mm thickness a quasi-monoenergetic beam of approximately 8.4 keV is obtained which is close to the absorption edge of Fe (7.11 keV). For a real-time counting period of 400 s the system is capable of detecting Fe concentrations of 15±2 ppm at a skin dose of the order of 5 mSv. This level of Fe is at the higher end of the normal range found in the skin. In using the same system and operating parameters, measurements on a sample of ferritin obtained from a rat's liver yield an Fe concentration of 36±3 ppm for a measurement time of 500 s; this can be compared with suppliers' data indicating an Fe level of 36 ppm. (author)

  14. Oxygen K-edge extended x-ray-absorption fine-structure studies of molecules containing oxygen and carbon atoms

    International Nuclear Information System (INIS)

    The absorption spectra of a group of selected molecules containing O: C bonds, carbon monoxide, carbon dioxide, carbonyl sulfide, acetone, ethanol, diethylether, tetrahydrofuran, and dioxane, have been recorded in a transmission mode in the energy region from 500 to 1000 eV. Earlier observation of extended x-ray-absorption fine structure (EXAFS) in some of these molecules is confirmed. A systematic analysis of the EXAFS spectra is performed. The results in both phase and amplitude show disagreement with the single-electron single-scattering theory with plane-wave approximation. The measured phase is systematically lower than the theory of Teo and Lee [J. Am. Chem. Soc. 101, 2815 (1979)] by about 0.7--1.5 rad, which may be significant in determining interatomic distances. The EXAFS amplitude function in the molecules containing oxygen-carbon single bonds also shows an appreciable deviation (decrease) in the first-neighbor backscattering from that predicted by theory and an increase in the second-neighbor backscattering at high-k values

  15. Study of porogen removal by atomic hydrogen generated by hot wire chemical vapor deposition for the fabrication of advanced low-k thin films

    International Nuclear Information System (INIS)

    In order to obtain low-k dielectric films, a subtractive technique, which removes sacrificial porogens from a hydrogenated silicon oxycarbide (SiOC:H) film, has been used successfully by different groups in the past. In this paper, we report on the porogen removal from porogenated SiOC:H films, using a hot wire chemical vapor deposition (HWCVD) equipment. Molecular hydrogen is dissociated into atomic hydrogen by the hot wires and these atoms may successfully remove the hydrocarbon groups from the porogenated SiOC:H films. The temperature of the HWCVD filaments proved to be a determining factor. By Fourier transform infrared spectroscopy, X-ray reflectivity (XRR), secondary ion mass spectrometry (SIMS), ellipsometric porosimetry and capacitance-voltage analyses, it was possible to determine that for temperatures higher than 1700 °C, efficient porogen removal occurred. For temperatures higher than 1800 °C, the presence of OH groups was detected. The dielectric constant was the lowest, 2.28, for the samples processed at a filament temperature of 1800 °C, although porosity measurements showed higher porosity for the films deposited at the higher temperatures. XRR and SIMS analyses indicated densification and Tungsten (W) incorporation at the top few nanometers of the films

  16. Atomic layer deposition of crystalline SrHfO{sub 3} directly on Ge (001) for high-k dielectric applications

    Energy Technology Data Exchange (ETDEWEB)

    McDaniel, Martin D.; Ngo, Thong Q.; Ekerdt, John G., E-mail: ekerdt@utexas.edu [Department of Chemical Engineering, The University of Texas at Austin, Austin, Texas 78712 (United States); Hu, Chengqing; Jiang, Aiting; Yu, Edward T. [Microelectronics Research Center, The University of Texas at Austin, Austin, Texas 78758 (United States); Lu, Sirong; Smith, David J. [Department of Physics, Arizona State University, Tempe, Arizona 85287 (United States); Posadas, Agham; Demkov, Alexander A. [Department of Physics, The University of Texas at Austin, Austin, Texas 78712 (United States)

    2015-02-07

    The current work explores the crystalline perovskite oxide, strontium hafnate, as a potential high-k gate dielectric for Ge-based transistors. SrHfO{sub 3} (SHO) is grown directly on Ge by atomic layer deposition and becomes crystalline with epitaxial registry after post-deposition vacuum annealing at ∼700 °C for 5 min. The 2 × 1 reconstructed, clean Ge (001) surface is a necessary template to achieve crystalline films upon annealing. The SHO films exhibit excellent crystallinity, as shown by x-ray diffraction and transmission electron microscopy. The SHO films have favorable electronic properties for consideration as a high-k gate dielectric on Ge, with satisfactory band offsets (>2 eV), low leakage current (<10{sup −5} A/cm{sup 2} at an applied field of 1 MV/cm) at an equivalent oxide thickness of 1 nm, and a reasonable dielectric constant (k ∼ 18). The interface trap density (D{sub it}) is estimated to be as low as ∼2 × 10{sup 12 }cm{sup −2 }eV{sup −1} under the current growth and anneal conditions. Some interfacial reaction is observed between SHO and Ge at temperatures above ∼650 °C, which may contribute to increased D{sub it} value. This study confirms the potential for crystalline oxides grown directly on Ge by atomic layer deposition for advanced electronic applications.

  17. Evidence for ultra-fast outflows in radio-quiet AGNs: II - detailed photo-ionization modeling of Fe K-shell absorption lines

    OpenAIRE

    Tombesi, F.; Cappi, M.; Reeves, J. N.; Palumbo, G.G.C.; Braito, V.; Dadina, M.

    2011-01-01

    X-ray absorption line spectroscopy has recently shown evidence for previously unknown Ultra-fast Outflows (UFOs) in radio-quiet AGNs. In the previous paper of this series we defined UFOs as those absorbers with an outflow velocity higher than 10,000km/s and assessed the statistical significance of the associated blueshifted FeK absorption lines in a large sample of 42 local radio-quiet AGNs observed with XMM-Newton. In the present paper we report a detailed curve of growth analysis and direct...

  18. Purification and characterization of two bifunctional chitinases/lysozymes extracellularly produced by Pseudomonas aeruginosa K-187 in a shrimp and crab shell powder medium.

    OpenAIRE

    Wang, S.L.; Chang, W T

    1997-01-01

    Two extracellular chitinases (FI and FII) were purified from the culture supernatant of Pseudomonas aeruginosa K-187. The molecular weights of FI and FII were 30,000 and 32,000, respectively, by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and 60,000 and 30,000, respectively, by gel filtration. The pIs for FI and FII were 5.2 and 4.8, respectively. The optimum pH, optimum temperature, pH stability, and thermal stability of FI were pH 8, 50 degrees C, pH 6 to 9, and 50 degrees C; ...

  19. 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。

  20. 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

  1. Evidence for ultra-fast outflows in radio-quiet AGNs: II - detailed photo-ionization modeling of Fe K-shell absorption lines

    CERN Document Server

    Tombesi, F; Reeves, J N; Palumbo, G G C; Braito, V; Dadina, M

    2011-01-01

    X-ray absorption line spectroscopy has recently shown evidence for previously unknown Ultra-fast Outflows (UFOs) in radio-quiet AGNs. In the previous paper of this series we defined UFOs as those absorbers with an outflow velocity higher than 10,000km/s and assessed the statistical significance of the associated blueshifted FeK absorption lines in a large sample of 42 local radio-quiet AGNs observed with XMM-Newton. In the present paper we report a detailed curve of growth analysis and directly model the FeK absorbers with the Xstar photo-ionization code. We confirm that the frequency of sources in the radio-quiet sample showing UFOs is >35%. The outflow velocity distribution spans from \\sim10,000km/s (\\sim0.03c) up to \\sim100,000km/s (\\sim0.3c), with a peak and mean value of \\sim42,000km/s (\\sim0.14c). The ionization parameter is very high and in the range log\\xi 3-6erg s^{-1} cm, with a mean value of log\\xi 4.2 erg s^{-1} cm. The associated column densities are also large, in the range N_H\\sim10^{22}-10^{24...

  2. Characterization of the core-shell interaction of differently stabilized transition-metal nanoparticles by means of X-ray absorption spectroscopy

    International Nuclear Information System (INIS)

    Transition metal nanoparticles with different surfactants were investigated using X-ray absorption spectroscopy (XAS) to obtain information about the interaction between metal core and protecting shell. For tetraalkylammoniumchloride stabilized Pd- and Co-colloids, a detailed model of the interaction between the metal core and the stabilizing shell could be established, in which chlorine is the connecting element between the metal core and the organic protection cover. Different lengths of the alkyl-chains can cause different equilibrium positions for the chlorine atoms. At aluminum-organic stabilized Pt-colloids, Al K-XANES and Pt LIII-XAS were carried out. In this case, it turned out that aluminum is the connecting element between metal core and protection shell. After modification of the shell by connecting different molecules to the outside of the shell, rearrangements of the shell could be observed. In contrast to the surfactant stabilized systems discussed above, metallic covers, especially gold coatings, of Co-particles did not lead to a complete protection shell. In all cases, the cobalt in the nanoparticles was oxidized. A core shell structure could not be verified for any of the metallic stabilized colloids. (orig.)

  3. Deformation of thin shallow nonuniform shells

    International Nuclear Information System (INIS)

    Shallow shells are common structural elements used in various sectors of industry. Problems of the theory of shallow shells have been the subject of numerous investigations, the results of which can be found. For the most part, researchers have focused on one-layer isotropic shells of constant thickness. Here, we examine problems related to the statics of shallow shells that are rectangular in plan and are composed of orthotropic layers of variable thickness. We assume the following in regard to the parameters of the coordinate surface of shells of this class: the internal geometry of the coordinate surface is identical to the geometry in a plane; the principal curvatures k1 and k2 are constant. The coordinates α and β are identical to the cartesian coordinates in a plane

  4. Effect of atomic-arrangement matching on La{sub 2}O{sub 3}/Ge heterostructures for epitaxial high-k-gate-stacks

    Energy Technology Data Exchange (ETDEWEB)

    Kanashima, T., E-mail: kanashima@ee.es.osaka-u.ac.jp; Zenitaka, M.; Kajihara, Y.; Yamada, S.; Hamaya, K. [Graduate School of Engineering Science, Osaka University, Machkaneyama 1-3, Toyonaka, Osaka 560-8531 (Japan); Nohira, H. [Tokyo City University, 1-28-1 Tamazutumi, Setagaya-ku, Tokyo 158-8557 (Japan)

    2015-12-14

    We demonstrate a high-quality La{sub 2}O{sub 3} layer on germanium (Ge) as an epitaxial high-k-gate-insulator, where there is an atomic-arrangement matching condition between La{sub 2}O{sub 3}(001) and Ge(111). Structural analyses reveal that (001)-oriented La{sub 2}O{sub 3} layers were grown epitaxially only when we used Ge(111) despite low growth temperatures less than 300 °C. The permittivity (k) of the La{sub 2}O{sub 3} layer is roughly estimated to be ∼19 from capacitance-voltage (C-V) analyses in Au/La{sub 2}O{sub 3}/Ge structures after post-metallization-annealing treatments, although the C-V curve indicates the presence of carrier traps near the interface. By using X-ray photoelectron spectroscopy analyses, we find that only Ge–O–La bonds are formed at the interface, and the thickness of the equivalent interfacial Ge oxide layer is much smaller than that of GeO{sub 2} monolayer. We discuss a model of the interfacial structure between La{sub 2}O{sub 3} and Ge(111) and comment on the C-V characteristics.

  5. Experimental and theoretical studies of metal vapor atoms

    International Nuclear Information System (INIS)

    Employing electron spectrometry in conjunction with tuneable synchrotron radiation, we will present a detailed examination of the photoionization dynamics of selected metal vapor atoms. In particular, this paper will focus on the relative partial cross sections of the atomic Li K-shell main and satellite (ionization with excitation) photoelectron lines in the region of the strong 1snln'l' autoionizing transitions, the atomic Sc 3d, 4s main and satellite photoelectron lines in the region of the 3p→3d giant resonance, and also the atomic Fe 3d, 4s main and satellite photoelectron lines in the same resonance region. Our experimental data for Sc and Fe will be compared to our state-of-the-art calculations based on the superposition of configuration method developed by Cowan (The Theory of Atomic Structure and Spectra. University of California Berkeley Press, Berkeley and Los Angeles, 1981). Our partial cross section measurements for Li and Sc will be complemented with measurements of the angular distribution parameter, β. In addition, our Li data will also be compared with recent R-matrix calculations (Phys. Rev. 57 (1998) 1045). In the case of Fe, we will also address the term dependent behavior of the partial cross sections on resonance. These results will highlight what can be achieved with today's technology and point the way towards future endeavors in the study of the photoionization dynamics of open-shell metal vapor atoms

  6. Evidence for ultra-fast outflows in radio-quiet AGNs. I. Detection and statistical incidence of Fe K-shell absorption lines

    Science.gov (United States)

    Tombesi, F.; Cappi, M.; Reeves, J. N.; Palumbo, G. G. C.; Yaqoob, T.; Braito, V.; Dadina, M.

    2010-10-01

    Context. Blue-shifted Fe K absorption lines have been detected in recent years between 7 and 10 keV in the X-ray spectra of several radio-quiet AGNs. The derived blue-shifted velocities of the lines can often reach mildly relativistic values, up to 0.2-0.4c. These findings are important because they suggest the presence of a previously unknown massive and highly ionized absorbing material outflowing from their nuclei, possibly connected with accretion disk winds/outflows. Aims: The scope of the present work is to statistically quantify the parameters and incidence of the blue-shifted Fe K absorption lines through a uniform analysis on a large sample of radio-quiet AGNs. This allows us to assess their global detection significance and to overcome any possible publication bias. Methods: We performed a blind search for narrow absorption features at energies greater than 6.4 keV in a sample of 42 radio-quiet AGNs observed with XMM-Newton. A simple uniform model composed by an absorbed power-law plus Gaussian emission and absorption lines provided a good fit for all the data sets. We derived the absorption lines parameters and calculated their detailed detection significance making use of the classical F-test and extensive Monte Carlo simulations. Results: We detect 36 narrow absorption lines on a total of 101 XMM-Newton EPIC pn observations. The number of absorption lines at rest-frame energies higher than 7 keV is 22. Their global probability to be generated by random fluctuations is very low, less than 3 × 10-8, and their detection have been independently confirmed by a spectral analysis of the MOS data, with associated random probability UFOs) those highly ionized absorbers with outflow velocities higher than 104 km s-1, then the majority of the lines are consistent with being associated to UFOs and the fraction of objects with detected UFOs in the whole sample is at least ~35%. This fraction is similar for type 1 and type 2 sources. The global covering fraction of

  7. Evidence for Ultra-Fast Outflows in Radio-Quiet AGNs. 2; Detailed Photoionization Modeling of Fe K-Shell Absorption Lines

    Science.gov (United States)

    Tombesi, Francesco; Clapp, M.; Reeves, J. N.; Palumbo, G. G. C.; Braito, V.; Dadina, M.

    2011-01-01

    X-ray absorption line spectroscopy has recently shown evidence for previously unknown Ultra-fast Outflows (UFOs) in radio-quiet AGNs. In the previous paper of this series we defined UFOs as those absorbers with an outflow velocity higher than 10,000km/s and assessed the statistical significance of the associated blue shifted FeK absorption lines in a large sample of 42 local radio-quiet AGNs observed with XMM-Newton. In the present paper we report a detailed curve of growth analysis and directly model the FeK absorbers with the Xstar photo-ionization code. We confirm that the frequency of sources in the radio-quiet sample showing UFOs is >35%. The outflow velocity distribution spans from \\sim10,000km/s (\\sim0.03c) up to \\siml00,000kmis (\\sim0.3c), with a peak and mean value of\\sim42,000km/s (\\sim0.14c). The ionization parameter is very high and in the range log\\xi 3-6 erg s/cm, with a mean value of log\\xi 4.2 erg s/cm. The associated column densities are also large, in the range N_H\\siml0(exp 22)-10(exp 24)/sq cm, with a mean value of N_H\\siml0(exp23)/sq cm. We discuss and estimate how selection effects, such as those related to the limited instrumental sensitivity at energies above 7keV, may hamper the detection of even higher velocities and higher ionization absorbers. We argue that, overall, these results point to the presence of extremely ionized and possibly almost Compton thick outflowing material in the innermost regions of AGNs. This also suggests that UFOs may potentially play a significant role in the expected cosmological feedback from AGNs and their study can provide important clues on the connection between accretion disks, winds and jets.

  8. Close shell interactions in 3-ethoxycarbonyl-4-hydroxy-6-methoxymethyleneoxy-1-methyl-2-quinolone: 100 K single crystal neutron diffraction study and ab initio calculations

    Science.gov (United States)

    Pozzi, C. G.; Fantoni, A. C.; Goeta, A. E.; Wilson, C. C.; Autino, J. C.; Punte, G.

    2005-10-01

    The molecular and crystal structures of the title compound have been determined from a single crystal neutron diffraction experiment at 100 K. A comparison between the main geometrical features and related properties of the in-crystal and the ab initio optimized free molecule structures has shown that crystal packing induces a significant distortion in the molecular geometry. Packing instead would only have a moderate effect on the observed intramolecular resonance assisted hydrogen bond. Supermolecular ab initio molecular orbital calculations have been performed on the six different dimers one molecule forms with its nine nearest neighbours. The obtained results clearly show that dispersion contributions dominate in the most strongly interacting dimers, in good qualitative accord with the predictions made by using different empirical potentials. A qualitative description of the most prominent inductive effects determined from the electron density deformation upon dimer formation is presented. Topological analyses of the dimers charge densities have been performed in the framework of the Bader's AIM theory and all the intermolecular bond critical points have been identified. An attempt to determine some of the interaction energies only from topological quantities made evident the practical limitations of such an approach.

  9. 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

    2016-07-01

    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.

  10. Auger electron spectroscopy applied to inner shell ionization by fast charged particles

    International Nuclear Information System (INIS)

    Until recently, inner shell ionization by charged particle impact was studied almost exclusively through the use of x-ray spectroscopy. This method is limited in accuracy, however, for ionization of inner shells where the fluorescence yield is small. For K-shell ionization of elements with atomic number less than about ten the fluorescence yield can be considered negligible and Auger electron emission cross section provide direct information regarding the ionization cross section. The ionization cross sections determined in this way are accurate to approximately 20 percent whereas x-ray measurements may be uncertain by a factor of five or more due to uncertainties in fluorescence yields. In addition to ionization cross sections, Auger emission spectra provide information regarding multiple ionization, effects of molecular binding on inner shell ionization and, when coupled with x-ray measurements, provide fluorescence yields as a function of the final state of the target atom. These points will be illustrated for ionization by fast protons along with some results for heavier incident particles

  11. Facile preparation of hybrid core-shell nanorods for photothermal and radiation combined therapy

    Science.gov (United States)

    Deng, Yaoyao; Li, Erdong; Cheng, Xiaju; Zhu, Jing; Lu, Shuanglong; Ge, Cuicui; Gu, Hongwei; Pan, Yue

    2016-02-01

    The hybrid platinum@iron oxide core-shell nanorods with high biocompatibility were synthesized and applied for combined therapy. These hybrid nanorods exhibit a good photothermal effect on cancer cells upon irradiation with a NIR laser. Furthermore, due to the presence of a high atomic number element (platinum core), the hybrid nanorods show a synergistic effect between photothermal and radiation therapy. Therefore, the as-prepared core-shell nanorods could play an important role in facilitating synergistic therapy between photothermal and radiation therapy to achieve better therapeutic efficacy.The hybrid platinum@iron oxide core-shell nanorods with high biocompatibility were synthesized and applied for combined therapy. These hybrid nanorods exhibit a good photothermal effect on cancer cells upon irradiation with a NIR laser. Furthermore, due to the presence of a high atomic number element (platinum core), the hybrid nanorods show a synergistic effect between photothermal and radiation therapy. Therefore, the as-prepared core-shell nanorods could play an important role in facilitating synergistic therapy between photothermal and radiation therapy to achieve better therapeutic efficacy. Electronic supplementary information (ESI) available: Details of general experimental procedures. See DOI: 10.1039/c5nr09102k

  12. Entropy squeezing and atomic inversion in the k-photon Jaynes—Cummings model in the presence of the Stark shift and a Kerr medium: A full nonlinear approach

    Science.gov (United States)

    H, R. Baghshahi; M, K. Tavassoly; A, Behjat

    2014-07-01

    The interaction between a two-level atom and a single-mode field in the k-photon Jaynes—Cummings model (JCM) in the presence of the Stark shift and a Kerr medium is studied. All terms in the Hamiltonian, such as the single-mode field, its interaction with the atom, the contribution of the Stark shift and the Kerr medium effects are considered to be f-deformed. In particular, the effect of the initial state of the radiation field on the dynamical evolution of some physical properties such as atomic inversion and entropy squeezing are investigated by considering different initial field states (coherent, squeezed and thermal states).

  13. Inner-Shell Photoionization: Teijo Aaberg's Concept of RRRS

    International Nuclear Information System (INIS)

    Teijo Aaberg died on December 29, 2000 - and with his passing we have lost a gifted and important member of our community. Over the years Teijo has made many major contributions to the science of x-ray and inner-shell physics. Perhaps the most visionary of these was his idea of radiative and radiationless resonant Raman scattering (RRRRS) [1]. This arose as an outgrowth of his earlier thoughts on Auger [2] and x-ray [3] processes. It is visionary in that it attempts to unify the various aspects of inner-shell photoexcitation and decay as different aspects of the same basic process, i.e. resonant inelastic x-ray scattering. In honor and memory of Teijo, and as a last attempt to promote his ideas, I describe here the theory and some of its consequences. First, RRRRS is outlined in a semi-rigorous form, with emphasis placed on the physical nature of the concepts. Then, using the example of atomic K-shell photoionization, we see how features such as fluorescence and photoelectron lines arise in a natural way as manifestations of resonance scattering

  14. Adsorption of iron (III ion on activated carbons obtained from bagasse, pericarp of rubber fruit and coconut shell

    Directory of Open Access Journals (Sweden)

    Orawan Sirichote

    2002-04-01

    Full Text Available The adsorptions of iron (III from aqueous solution at room temperature on activated carbons obtaining from bagasse, pericarp of rubber fruit and coconut shell have been studied by atomic absorption spectrophotometry. The activated carbons were prepared by carbonization of these raw materials and followed by activation with ZnCl2 . The adsorption behavior of iron (III on these activated carbons could be interpreted by Langmuir adsorption isotherm as monolayer coverage. The maximum amounts of iron (III adsorbed per gram of these activated carbons were 0.66 mmol/g, 0.41 mmol/g and 0.18 mmol/g, respectively. Study of the temperature dependence on these adsorptions has revealed them to be exothermic processes with the heats of adsorption of about -8.9 kJ/mol , -9.7 kJ/mol and -5.7 kJ/mol for bagasse, pericarp of rubber fruit and coconut shell, respectively.

  15. Size effect in the melting and freezing behaviors of Al/Ti core-shell nanoparticles using molecular dynamics simulations

    Science.gov (United States)

    Jin-Ping, Zhang; Yang-Yang, Zhang; Er-Ping, Wang; Cui-Ming, Tang; Xin-Lu, Cheng; Qiu-Hui, Zhang

    2016-03-01

    The thermal stability of Ti@Al core/shell nanoparticles with different sizes and components during continuous heating and cooling processes is examined by a molecular dynamics simulation with embedded atom method. The thermodynamic properties and structure evolution during continuous heating and cooling processes are investigated through the characterization of the potential energy, specific heat distribution, and radial distribution function (RDF). Our study shows that, for fixed Ti core size, the melting temperature decreases with Al shell thickness, while the crystallizing temperature and glass formation temperature increase with Al shell thickness. Diverse melting mechanisms have been discovered for different Ti core sized with fixed Al shell thickness nanoparticles. The melting temperature increases with the Ti core radius. The trend agrees well with the theoretical phase diagram of bimetallic nanoparticles. In addition, the glass phase formation of Al-Ti nanoparticles for the fast cooling rate of 12 K/ps, and the crystal phase formation for the low cooling rate of 0.15 K/ps. The icosahedron structure is formed in the frozen 4366 Al-Ti atoms for the low cooling rate. Project supported by the National Natural Science Foundation of China (Grant No. 21401064), the Science & Technology Development Program of Henan Province, China (Grant No. 142300410282), and the Program of Henan Educational Committee, China (Grant No. 13B140986).

  16. 2 MeV electron irradiation effects on bulk and interface of atomic layer deposited high-k gate dielectrics on silicon

    International Nuclear Information System (INIS)

    2 MeV electron irradiation effects on the electrical properties of Al2O3 and HfO2-based metal–insulator–semiconductor capacitors have been studied. High-k dielectrics were directly grown on silicon by atomic layer deposition. Capacitors were exposed to three different electron irradiation doses of 0.025, 0.25 and 2.5 MGy. Capacitance–voltage, deep-level transient spectroscopy, conductance transients, flat-band voltage transients and current–voltage techniques were used to characterize the defects induced or activated by irradiation on the dielectric bulk and on the interface with silicon substrate. In all cases, positive charge is trapped in the dielectric bulk after irradiation indicating the existence of hole traps in the dielectric. When the samples are exposed to 2 MeV electron beam (e-beam) irradiation, electron–hole pairs are created and holes are then captured by the hole traps. Insulator/semiconductor interface quality slightly improves for low irradiation doses, but it is degraded for high doses. Irradiation always degrades the dielectric layers in terms of gate leakage current: the trapped holes are mobile charge which can contribute to leakage current by hopping from trap to trap. - Highlights: ► Positive charge accumulates inside dielectrics after electron irradiation. ► Irradiation improves oxide/semiconductor interface for low doses. ► Irradiation increases gate leakage current

  17. 2 MeV electron irradiation effects on bulk and interface of atomic layer deposited high-k gate dielectrics on silicon

    Energy Technology Data Exchange (ETDEWEB)

    García, H., E-mail: hecgar@ele.uva.es [Departamento de Electricidad y Electrónica, ETSI Telecomunicación, Universidad de Valladolid, 47011 Valladolid (Spain); Castán, H.; Dueñas, S.; Bailón, L. [Departamento de Electricidad y Electrónica, ETSI Telecomunicación, Universidad de Valladolid, 47011 Valladolid (Spain); Campabadal, F.; Rafí, J.M.; Zabala, M.; Beldarrain, O. [Institut de Microelectrònica de Barcelona (IMB-CNM), CSIC, Campus UAB, 08193 Bellaterra (Spain); Ohyama, H.; Takakura, K.; Tsunoda, I. [Department of Electronic Engineering, Kumamoto National College of Technology, Kumamoto 861-1102 (Japan)

    2013-05-01

    2 MeV electron irradiation effects on the electrical properties of Al{sub 2}O{sub 3} and HfO{sub 2}-based metal–insulator–semiconductor capacitors have been studied. High-k dielectrics were directly grown on silicon by atomic layer deposition. Capacitors were exposed to three different electron irradiation doses of 0.025, 0.25 and 2.5 MGy. Capacitance–voltage, deep-level transient spectroscopy, conductance transients, flat-band voltage transients and current–voltage techniques were used to characterize the defects induced or activated by irradiation on the dielectric bulk and on the interface with silicon substrate. In all cases, positive charge is trapped in the dielectric bulk after irradiation indicating the existence of hole traps in the dielectric. When the samples are exposed to 2 MeV electron beam (e-beam) irradiation, electron–hole pairs are created and holes are then captured by the hole traps. Insulator/semiconductor interface quality slightly improves for low irradiation doses, but it is degraded for high doses. Irradiation always degrades the dielectric layers in terms of gate leakage current: the trapped holes are mobile charge which can contribute to leakage current by hopping from trap to trap. - Highlights: ► Positive charge accumulates inside dielectrics after electron irradiation. ► Irradiation improves oxide/semiconductor interface for low doses. ► Irradiation increases gate leakage current.

  18. The use of hogdahl convention k0 neutron activation analysis (NAA) standardization method and atomic absortion spectroscopy (ASS) for determination of toxic elements in foodstuffs

    International Nuclear Information System (INIS)

    Copper, cadmium, tin, chromium, arsenic, antimony, vanadium and mercury contents were determined in various foodstuffs (Mussa paradisiaca (plantains), Manihot esculentus (cassavas), Vantosoma sagittifolium (cocoyam). Vantosoma sagittifolium leaves (kontomire), Lycopersicum esculentus (tomatoes), Capsicum species (peppers), Solanum melongena (garden eggs), Nbelmoschus esculentus (okro), and Colocasia esculenta (kooko or taro)) produced in the Wassa West District, Ghana. These plants are the basis of human nutrition in the study area. These elements were determined using Hogdahl convention k0 Instrumental Neutron Activation Analysis (NAA) Standardization Method and Atomic Absorption Spectroscopy (AAS). The elements in the various foodstuffs and their concentration ranges were Cu (16.87-180.06) mg/kg, As (2.68-9.84) µg/g, Cd (0.63-5.64) µg/g, Hg (0.01-67) ng/g, Cr (0.03-3.66) µg/g, Sb (1.1- 18.6) ng/g, Sn (3.4-58.4) ng/g, and V (12-99) ng/g. The study showed that there are high levels of toxic elements in the foodstuffs grown in the mining areas as compared to that of the non-mining area (i.e., control area). This could be attributed to gold mines pollution. Compared to the World Health Organization (WHO) permissible levels of toxic elements in foods, Cu, Cr and Hg were above the permissible levels whereas the concentrations of As, Cd. Sb, Sn and V fall within the permissible levels. (au)

  19. 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...

  20. 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

  1. 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),…

  2. 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

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

    International Nuclear Information System (INIS)

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

  4. A short pulse (7 μs FWHM) and high repetition rate (dc-5kHz) cantilever piezovalve for pulsed atomic and molecular beams

    International Nuclear Information System (INIS)

    In this paper we report on the design and operation of a novel piezovalve for the production of short pulsed atomic or molecular beams. The high speed valve operates on the principle of a cantilever piezo. The only moving part, besides the cantilever piezo itself, is a very small O-ring that forms the vacuum seal. The valve can operate continuous (dc) and in pulsed mode with the same drive electronics. Pulsed operation has been tested at repetition frequencies up to 5 kHz. The static deflection of the cantilever, as mounted in the valve body, was measured as a function of driving field strength with a confocal microscope. The deflection and high speed dynamical response of the cantilever can be easily changed and optimized for a particular nozzle diameter or repetition rate by a simple adjustment of the free cantilever length. Pulsed molecular beams with a full width at half maximum pulse width as low as 7 μs have been measured at a position 10 cm downstream of the nozzle exit. This represents a gas pulse with a length of only 10 mm making it well matched to for instance experiments using laser beams. Such a short pulse with 6 bar backing pressure behind a 150 μm nozzle releases about 1016 particles/pulse and the beam brightness was estimated to be 4x1022 particles/(s str). The short pulses of the cantilever piezovalve result in a much reduced gas load in the vacuum system. We demonstrate operation of the pulsed valve with skimmer in a single vacuum chamber pumped by a 520 l/s turbomolecular pump maintaining a pressure of 5x10-6 Torr, which is an excellent vacuum to have the strong and cold skimmed molecular beam interact with laser beams only 10 cm downstream of the nozzle to do velocity map slice imaging with a microchannel-plate imaging detector in a single chamber. The piezovalve produces cold and narrow (Δv/v=2%-3%) velocity distributions of molecules seeded in helium or neon at modest backing pressures of only 6 bar. The low gas load of the cantilever

  5. 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)

  6. 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...

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

    International Nuclear Information System (INIS)

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

  8. 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...

  9. Mineral Composition of the Cockle (Anadara granosa Shells of West Coast of Peninsular Malaysia and It?s Potential as Biomaterial for Use in Bone Repair

    Directory of Open Access Journals (Sweden)

    M.M. Noordin

    2007-01-01

    Full Text Available The study was conducted to determine the composition of mineral content of cockle (Anadara granosa shells from 3 major cockle cultivation of West Coast of Malaysia. Three samples of cockle shells from three different sources were evaluated to determine the content of 12 macro-and micro-elements (Calcium (Ca, Carbon (C, Magnesium (Mg, Sodium (Na, Phosphorus (P, Potassium (K, Ferum (Fe, Copper (Cu, Nickel ( Ni, Zink (Zn, Boron and Silica (Si. For convenience and ease of reference, Ca and C were combine into one unit (Calcium Carbonate, CaC while Mg, Na, P and K was evaluated individually and Fe, Cu, Ni, Zn, B and Si were evaluated as one group (others. Analysis of elements content was done using inductively Coupled plasma, Auto Analyzer, an Atomic Absorption Spectrophotometer and Carbon Analyzer. Results in this study revealed that the mineral compositions of cockle shells from 3 different sources in West Coast of Peninsular Malaysia were consistence almost in all the samples. The percentage of CaC comprises of more than 98.7% of the total minerals content of the cockle shells of the 3 sources. About 1.3 % of the composition are comprises of Mg, Na, P, K and others (Fe, Cu, Ni, B, Zn and Si.Overall, the minerals composition of cockle shells of West Coast of Peninsular Malaysia are as followed: CaC 98.7 %, Mg 0.05%, Na 0.9%, p 0.02 and others 0.2%.

  10. Measurements of egg shell plasma parameters using laser-induced breakdown spectroscopy

    Indian Academy of Sciences (India)

    Wenfeng Luo; Xiaoxia Zhao; Shuyuan Lv; Haiyan Zhu

    2015-07-01

    Measurements of 1064 nm laser-induced egg shell plasma parameters are presented in this paper. Of special interests were its elemental identification and the determination of spectroscopic temperature and electron density. The electron temperature of 5956 K was inferred using an improved iterative Boltzmann plot method with six calcium atomic emission lines, and the electron number density of 6.1 × 1016 cm−3 was determined by measuring the width of Stark-broadened once-ionized calcium line at 393.37 nm. Based on the experimental results, the laser-induced egg shell plasma was verified to be optically thin and satisfy local thermodynamic equilibrium (LTE). Furthermore, experiments also demonstrated that the loss of energy due to the reflection of the laser beam from the plasma can be neglected and the inverse bremsstrahlung (IB) absorption was the dominant mechanism of plasma heating at the IR wavelength.

  11. 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.

  12. Electron-ion time-of-flight coincidence measurements of K-K electron-capture, cross sections for nitrogen, methane, ethylene, ethane, carbon dioxide, and argon (L-K) targets

    International Nuclear Information System (INIS)

    Protons with energies ranging from 0.4 to 2.0 MeV were used to measure K-shell vacancy production cross sections for N2, CH4, C2H4, C7H6, and CO2 gas targets under single collision conditions. An electron-ion time-of-light coincidence technique was used to determine the ratio of the K-K electron capture cross section to the K-vacancy production cross section. These ratios were then combined to extract the K-K electron capture cross sections. Measurements were also made for protons of the same energy range but with regard to L-shell vacancy production and L-K electron capture for Ar targets. In addition, K-K electron capture cross sections were measured for 1.0-2.0 MeV He+ ions on CH4. The agreement among the present measurements, previously published measurements, and the ECPSSR theory is excellent for protons incident on N2, Ar, and CH4. The present measurements do indicate that there is a molecular dependence for the carbon atom K-K electron capture cross sections

  13. Inner-shell couplings in transiently formed superheavy quasimolecules

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-06-15

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

  14. 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.

  15. Comment on “Atomic mass compilation 2012” by B. Pfeiffer, K. Venkataramaniah, U. Czok, C. Scheidenberger

    Energy Technology Data Exchange (ETDEWEB)

    Audi, G., E-mail: amdc.audi@gmail.com [CSNSM, CNRS/IN2P3, Université Paris-Sud, Bât. 108, F-91405 Orsay Campus (France); Blaum, K. [Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg (Germany); Block, M. [GSI Helmholtzzentrum für Schwerionenforschung GmbH, Planckstrasse 1, D-64291 Darmstadt (Germany); Bollen, G. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824 (United States); Goriely, S. [Institut d’Astronomie et d’Astrophysique, CP-226, Université Libre de Bruxelles, 1050 Brussels (Belgium); Hardy, J.C. [Cyclotron Institute, Texas A& M University, College Station, TX 77843 (United States); Herfurth, F. [GSI Helmholtzzentrum für Schwerionenforschung GmbH, Planckstrasse 1, D-64291 Darmstadt (Germany); Kondev, F.G. [Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL 60439 (United States); Kluge, H.-J. [GSI Helmholtzzentrum für Schwerionenforschung GmbH, Planckstrasse 1, D-64291 Darmstadt (Germany); University of Heidelberg, D-69120 Heidelberg (Germany); Lunney, D. [CSNSM, CNRS/IN2P3, Université Paris-Sud, Bât. 108, F-91405 Orsay Campus (France); Pearson, J.M. [Département de Physique, Université de Montréal, Montréal, Québec, H3C 3J7 (Canada); Savard, G. [Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL 60439 (United States); Sharma, K.S. [Department of Physics and Astronomy, University of Manitoba, Winnipeg, MB R3T 2N2 (Canada); and others

    2015-05-15

    In order to avoid errors and confusion that may arise from the recent publication of a paper entitled “Atomic Mass Compilation 2012”, we explain the important difference between a compilation and an evaluation; the former is a necessary but insufficient condition for the latter. The simple list of averaged mass values offered by the “Atomic Mass Compilation” uses none of the numerous links and correlations present in the large body of input data that are carefully maintained within the “Atomic Mass Evaluation”. As such, the mere compilation can only produce results of inferior accuracy. Illustrative examples are given.

  16. 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.

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

    International Nuclear Information System (INIS)

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

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

    Science.gov (United States)

    Fransson, Thomas; Burdakova, Daria; Norman, Patrick

    2016-05-21

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

  19. Growth models of coexisting p(2 × 1) and c(6 × 2) phases on an oxygen-terminated Cu(110) surface studied by noncontact atomic force microscopy at 78 K

    Science.gov (United States)

    Li, Yan Jun; Lee, Seung Hwan; Kinoshita, Yukinori; Ma, Zong Min; Wen, Huanfei; Nomura, Hikaru; Naitoh, Yoshitaka; Sugawara, Yasuhiro

    2016-05-01

    We present an experimental study of coexisting p(2 × 1) and c(6 × 2) phases on an oxygen-terminated Cu(110) surface by noncontact atomic force microscopy (NC-AFM) at 78 K. Ball models of the growth processes of coexisting p(2 × 1)/c(6 × 2) phases on a terrace and near a step are proposed. We found that the p(2 × 1) and c(6 × 2) phases are grown from the super Cu atoms on both sides of O–Cu–O rows of an atomic spacing. In this paper, we summarize our investigations of an oxygen-terminated Cu(110) surface by NC-AFM employing O- and Cu-terminated tips. Also, we state several problems and issues for future investigation.

  20. Entropy squeezing and atomic inversion in the k-photon Jaynes—Cummings model in the presence of the Stark shift and a Kerr medium: A full nonlinear approach

    International Nuclear Information System (INIS)

    The interaction between a two-level atom and a single-mode field in the k-photon Jaynes—Cummings model (JCM) in the presence of the Stark shift and a Kerr medium is studied. All terms in the Hamiltonian, such as the single-mode field, its interaction with the atom, the contribution of the Stark shift and the Kerr medium effects are considered to be f-deformed. In particular, the effect of the initial state of the radiation field on the dynamical evolution of some physical properties such as atomic inversion and entropy squeezing are investigated by considering different initial field states (coherent, squeezed and thermal states). (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)