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Sample records for inner-shell vacancy cascades

  1. Study of inner-shell vacancy cascades by coincidence techniques

    SciTech Connect

    LeBrun, T.; Arp, U.; MacDonald, M.; Southworth, S.H.

    1995-08-01

    An inner-shell vacancy in an atom decays by an intricate combination of Auger and fluorescence processes. The interrelation between these processes is not well understood because traditional studies of core-excited atoms focus on only one of the many particles that participate in the relaxation - largely ignoring the other components and the correlations between them. To understand these correlations we developed a coincidence technique that uses coincident detection of X-rays and electrons to select decay pathways that involve emission of both an X-ray photon and electrons. In the first application of this technique, the Ar 1s photoelectron spectrum was recorded selectively in coincidence with X-ray fluorescence to eliminate the asymmetric broadening and shifting of the energy distribution which results due to post-collision interaction with K-Auger electrons. This allowed the direct observation of the interaction between the photoelectron and the decay of core holes created after the initial photoionization event. We have also applied this technique to the much more complex problem of understanding Auger-electron spectra produced by vacancy cascades following inner-shell excitation. For example, we previously recorded non-coincident electron spectra of L{sub 2,3}MM Auger transitions following K-shell excitation of argon. Interpretation of these spectra is difficult because they are complicated and consist of many overlapping or unresolved Auger transitions between different ionic states.

  2. Inner shell vacancy filling and production in highly-charged-ion surface collisions

    SciTech Connect

    Grether, M.

    1994-12-31

    Secondary electron spectra of H-like Ne{sup 9+} ions incident with impact energies from 135 eV to 22.5 keV on a solid Al(111) surface were measured. The dependence of the K Auger electron yield on the observation angle and on the projectile energy is studied in detail. The data show clear evidence for Auger emission from below the surface even for the lowest projectile velocity. In addition, it is found that the Ne L shell filling via charge exchange decrease with decreasing impact energy and reaches zero near an incident energy of 200 eV. Also, the authors measured the intensity of the Au N{sub 5}N{sub 6,7}N{sub 6,7} Auger electrons for Ar{sup 9+} ions with kinetic energies from 125 eV up to 5.3 keV. A threshold behavior is observed in the production of target Au N{sub 5} vacancies by Ar{sup 9+} ions. To analyse the data, they calculated correlation diagrams involving model energies to obtain the internuclear distance of orbital and potential curve crossings. The comparison of experiment and theory shows that the excitation process is not expected to be due to a resonant vacancy transfer from the projectile to the target but due to a dielectronic process which is governed by the electron-electron interaction.

  3. Atomic inner-shell transitions

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

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

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

    SciTech Connect

    Mohammedein, Adel M.; Ghoneim, Adel A.; Kandil, Kandil M.; Kadad, Ibrahim M.

    2010-01-05

    The vacancy cascades following initial inner-shell vacancies in single and multi-ionized atoms often lead to highly charged residual ions. The inner-shell vacancy produced by ionization processes may decay by either a radiative or non-radiative transition. In addition to the vacancy filling processes, there is an electron shake off process due to the change of core potential of the atom. In the calculation of vacancy cascades, the radiative (x-ray) and non-radiative (Auger and Coster-Kronig) branching ratios give valuable information on the de-excitation dynamics of an atom with inner-shell vacancy. The production of multi-charged ions yield by the Auger cascades following inner shell ionization of an atom has been studied both experimentally and theoretically. Multi-charged Xe ions following de-excitation of K-, L{sub 1}-, L{sub 2,3}-, M{sub 1}-, M{sub 2,3}- and M{sub 4,5} subshell vacancies are calculated using Monte-Carlo algorithm to simulate the vacancy cascade development. Fluorescence yield (radiative) and Auger, Coster- Kronig yield (non- radiative) are evaluated. The decay of K hole state through radiative transitions is found to be more probable than non-radiative transitions in the first step of de-excitation. On the other hand, the decay of L, M vacancies through non-radiative transitions are more probable. The K shell ionization in Xe atom mainly yields Xe{sup 7+}, Xe{sup 8+}, Xe{sup 9+} and Xe{sup 10+} ions, and the charged X{sup 8+} ions are the highest. The main product from the L{sub 1}- shell ionization is found to be Xe{sup 8+}, Xe{sup 9+} ions, while the charged Xe{sup 8+} ions predominate at L{sub 2,3} hole states. The charged Xe{sup 6+}, Xe{sup 7+} and Xe{sup 8+} ions mainly yield from 3s{sub 1/2} and 3p{sub 1/2,3/2} ionization, while Xe in 3d{sub 3/2,5/2} hole states mainly turns into Xe{sup 4+} and Xe{sup 5+} ions. The present results are found to agree well with the experimental data.

  5. Model for vacancy-loop nucleation in displacement cascades

    NASA Astrophysics Data System (ADS)

    Kapinos, V. G.; Bacon, D. J.

    1995-08-01

    A model is proposed for the nucleation of collapsed vacancy clusters in irradiated metals, based on the principle that a vacancy loop may be nucleated in a cascade which has melted and recrystallized. The equation of thermal conduction is solved using the discretization method and initial temperature and vacancy distributions given by the marlowe code. The model simulates the processes of heat propagation, local melting, absorption and release of latent heat, and the redistribution of the density within the melt. Under the influence of the temperature gradient, the concentration of vacancies in the depleted zone increases. Simulation of hundreds of cascades gives the distribution of zones as a function of vacancy concentration and number of vacancies in them, and it is assumed that critical values Ccr and Ncrv have to be achieved to produce a visible vacancy loop. However, if the concentration exceeds a value Camv under sufficiently fast cooling, for example under strong electron-phonon coupling (EPC), the melted zone cannot crystallize completely and solidifies instead to a semiamorphous core. This prevents collapse to a vacancy loop. The model has been used to calculate the yield and mean size of vacancy loops in ion-irradiated Cu, Ni, and Cu-Ge and Cu-Ni alloys. Physically reasonable values of Ccr, Ncr, and Camv have been obtained to give good agreement with experimental values of yield and size. Furthermore, the trends with alloy content can be explained, and it is found that EPC can have a strong influence on loop yield.

  6. Computation of Ion Charge State Distributions After Inner-Shell Ionization In Ne, Ar And Kr Atoms Using Monte Carlo Simulation

    SciTech Connect

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

    2010-01-05

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

  7. Threshold Phenomena in Atomic Inner Shells

    NASA Astrophysics Data System (ADS)

    Wang, Honghong

    1995-01-01

    Two types of atomic inner-shell threshold phenomena are studied: (1) atomic inner-shell radiationless resonant Raman scattering (RRRS) as a function of excitation energy, and (2) the onset of Cu Coster-Kronig (CK) transitions due to extraatomic relaxation, as a function of cluster size. (1). The K-L_{2,3}L _{2,3} and L_{2,3 }-VV Auger spectra of P in InP were measured in the vicinity of the P K-shell ionization threshold as well as at high excess energies. The evolution of the P K-L_{2,3 }L_{2,3} ^1D Auger spectrum from the radiationless resonant Raman scattering regime into the normal Auger transition regime in InP is found to be in accordance with time-independent resonant scattering theory of inner-shell threshold phenomena. The measured RRRS intensity reveals a quasi-bound state in the bulk-sensitive P K absorption spectrum. The origins of deviations of the RRRS energy from linear dispersion are examined in terms of the finite incident-photon-energy distribution and multiple resonances. Both our measurements and semiclassical calculations show that the post-collision interaction effect is relatively small. The measured P K-L_{2,3}L_{2,3} intensities and P 1s lifetime width are found to be in good agreement with atomic calculations, revealing the predominantly atomic character of P inner-shell transitions in InP. The evolution of P L_{2,3 }-VV Auger transitions in InP is found to be sensitive to the excitation energy at the P 1s threshold; the P K-L_{2,3}L_{2,3 } Raman resonance causes changes in the L _{2,3}-VV diagram-transition line shape as well as intensity enhancement of all L _{2,3}-VV features. Applying the Cini-Sawatzky model to the line shape reveals a 0.3-eV change in the local effective Coulomb interaction U _{eff} near the resonance. The difference in the line shapes between the satellite and diagram transitions indicates a change of the local density of states in the valence band in the presence of a spectator 2p hole. The single- and double-2p

  8. Inner-shell excitation spectroscopy of peroxides

    NASA Astrophysics Data System (ADS)

    Harding, K. L.; Kalirai, S.; Hayes, R.; Ju, V.; Cooper, G.; Hitchcock, A. P.; Thompson, M. R.

    2015-11-01

    O 1s inner-shell excitation spectra of a number of vapor phase molecules containing peroxide bonds - hydrogen peroxide (H2O2), di-t-butylperoxide (tBuOtBu), benzoyl peroxide, ((C6H5(CO)O)2), luperox-F [1,3(4)-bis(tertbutylperoxyisopropyl) benzene], and analogous, non-peroxide compounds - water, t-butanol and benzoic acid have been measured. C 1s spectra are also reported. O 1s spectra of solid benzoic acid, di-t-butylperoxide and luperox-F recorded using a scanning transmission X-ray microscope, are also reported, and compared to the corresponding gaseous spectra. Spectral interpretation was aided by comparing the spectra of the peroxide and non-peroxide counterparts and with ab initio calculations. A characteristic O 1s → σ∗O-O transition at 533.0(3) eV is identified in each peroxide species, which is absent in the corresponding non-peroxide counterpart species. The energy and intensity of the 533 eV peroxide feature is stable and thus useful for analysis of peroxides in mixtures, such as tracking residual peroxide initiators, or peroxides produced in fuel cells.

  9. The formation and stability of He-vacancy clusters within displacement cascades in α-Fe

    SciTech Connect

    Gao, Fei; Heinisch, Howard L.; Kurtz, Richard J.

    2007-10-25

    Molecular dynamics (MD) methods have been utilized to study the formation of vacancy clusters created by displacement cascades in α-Fe containing concentrations of substitutional He atoms varying from 1-5%. These He concentrations are not necessarily intended to represent specific conditions within a fusion reactor (average end-of-life He concentrations in the first wall are expected to be on the order of 0.15%), but they provide an opportunity to investigate the effects of substantial amounts of He on cascade processes and microstructure development under damage producing conditions.

  10. Do inner shells of double-walled carbon nanotubes fluoresce?

    PubMed

    Tsyboulski, Dmitri A; Hou, Ye; Fakhri, Nikta; Ghosh, Saunab; Zhang, Ru; Bachilo, Sergei M; Pasquali, Matteo; Chen, Liwei; Liu, Jie; Weisman, R Bruce

    2009-09-01

    The reported fluorescence from inner shells of double-walled carbon nanotubes (DWCNTs) is an intriguing and potentially useful property. A combination of bulk and single-molecule methods was used to study the spectroscopy, chemical quenching, mechanical rigidity, abundance, density, and TEM images of the near-IR emitters in DWCNT samples. DWCNT inner shell fluorescence is found to be weaker than SWCNT fluorescence by a factor of at least 10,000. Observable near-IR emission from DWCNT samples is attributed to SWCNT impurities. PMID:19653638

  11. X-ray fluorescence/Auger-electron coincidence spectroscopy of vacancy cascades in atomic argon

    SciTech Connect

    Arp, U.; LeBrun, T.; Southworth, S.H.; Jung, M.; MacDonald, M.A.

    1996-12-01

    Argon L{sub 2.3}-M{sub 2.3}M{sub 2.3} Auger-electron spectra were measured in coincidence with K{alpha} fluorescent x-rays in studies of Ar K-shell vacancy decays at several photon energies above the K-threshold and on the 1s-4p resonance in atomic argon. The complex spectra recorded by conventional electron spectroscopy are greatly simplified when recorded in coincidence with fluorescent x-rays, allowing a more detailed analysis of the vacancy cascade process. The resulting coincidence spectra are compared with Hartree-Fock calculations which include shake-up transitions in the resonant case. Small energy shifts of the coincidence electron spectra are attributed to post-collision interaction with 1s photoelectrons.

  12. An efficient, selective collisional ejection mechanism for inner-shell population inversion in laser-driven plasmas

    SciTech Connect

    SCHROEDER,W. ANDREAS; NELSON,THOMAS R.; BORISOV,A.B.; LONGWORTH,J.W.; BOYER,K.; RHODES,C.K.

    2000-06-07

    A theoretical analysis of laser-driven collisional ejection of inner-shell electrons is presented to explain the previously observed anomalous kilovolt L-shell x-ray emission spectra from atomic Xe cluster targets excited by intense sub-picosecond 248nrn ultraviolet radiation. For incident ponderomotively-driven electrons photoionized by strong above threshold ionization, the collisional ejection mechanism is shown to be highly l-state and significantly n-state (i.e. radially) selective for time periods shorter than the collisional dephasing time of the photoionized electronic wavefunction. The resulting preference for the collisional ejection of 2p electrons by an ionized 4p state produces the measured anomalous Xe(L) emission which contains direct evidence for (i) the generation of Xe{sup 27+}(2p{sup 5}3d{sup 10}) and Xe{sup 28+}(2p{sup 5}3d{sup 9}) ions exhibiting inner-shell population inversion and (ii) a coherent correlated electron state collision responsible for the production of double 2p vacancies. For longer time periods, the selectivity of this coherent impact ionization mechanism is rapidly reduced by the combined effects of intrinsic quantum mechanical spreading and dephasing--in agreement with the experimentally observed and extremely strong {minus}{lambda}{sup {minus}6} pump-laser wavelength dependence of the efficiency of inner-shell (2p) vacancy production in Xe clusters excited in underdense plasmas.

  13. Inner-shell Photoionization Studies of Neutral Atomic Nitrogen

    NASA Astrophysics Data System (ADS)

    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.

  14. Cascade decays of hollow ions

    SciTech Connect

    Omar, G. ); Hahn, Y. )

    1991-05-01

    A multiple-electron-emission process for atoms with one or more inner-shell vacancies is treated using the radiative- and Auger-electron-emission cascade model, in which inner-shell holes are assumed to decay by sequentially emitting radiations and/or Auger electrons. Such hollow ions are produced by synchrotron irradiation of atomic targets and in ion-surface interactions with multiple-electron transfers. The final charge-state distribution is determined by the Auger and radiative branching ratios at each stage of the decay sequence. At intermediate stages of cascade, hollow ions with more than one hole in different ionization stages are created. The Ne, Mg, and Fe{sup 14+} ions with the initial 1{ital s}, 2{ital s}, and 2{ital p} vacancies are considered in detail, and the core charge dependence of the maximum charge state is studied. The hollow Mg ion with double initial 1{ital s} holes is analyzed, and the result compared with that for the case of one 1{ital s} hole. The peak is shifted more than two units to a higher degree of ionization. The correlated shake-off and shake-up multiple-electron processes are not considered, but they are expected to cause further shifts.

  15. Triple ionization of atomic Cd involving 4 p-1 and 4 s-1 inner-shell holes

    NASA Astrophysics Data System (ADS)

    Andersson, J.; Beerwerth, R.; Linusson, P.; Eland, J. H. D.; Zhaunerchyk, V.; Fritzsche, S.; Feifel, R.

    2015-08-01

    The triple ionization spectrum of atomic Cd formed upon the removal of a 4 p or a 4 s inner-shell electron and subsequent Auger decays has been obtained at 200 eV photon energy. By using a versatile multielectron coincidence detection technique based on a magnetic bottle spectrometer in combination with multiconfiguration Dirac-Fock calculations, Auger cascades leading to tricationic final states have been analyzed and final-state configurations have been identified. The most prominent Auger cascades leading to the ground state of Cd3 + have been identified in good agreement with theory.

  16. Inner-shell excitation and ionic fragmentation of molecules

    SciTech Connect

    Hitchcock, A.P.; Tyliszczak, T.; Cavell, R.G.

    1997-04-01

    Inner-shell excitation and associated decay spectroscopies are site specific probes of electronic and geometrical structure and photoionization dynamics. X-ray absorption probes the geometric and electronic structure, while time-of-flight mass spectrometry with multi-coincidence detection provides information on the photofragmentation dynamics of the initially produced inner-shell state. Auger decay of inner-shell excited and ionised states is an efficient source of multiply charged ions. The charge separation and fragmentation of these species, studied by photoelectron-photoion-photoion coincidence (also called charge separation mass spectrometry) gives insights into bonding and electronic structure. In molecules, the dependence of the fragmentation process on the X-ray energy can reveal cases of site and/or state selective fragmentation. At the ALS the authors have examined the soft X-ray spectroscopy and ionic fragmentation of a number of molecules, including carboranes, silylenes, phosphorus halides, SF{sub 6} and CO{sub 2}. Their work is illustrated using results from the carborane and PF{sub 3} studies.

  17. Report on the 18th International Conference on X-ray and Inner-Shell Processes (X99).

    SciTech Connect

    Gemmell, D. S.; Physics

    2000-01-01

    The 18th conference of the series served as a forum for discussing fundamental issues in the field of x-ray and inner-shell processes and their application in various disciplines of science and technology. Special emphasis was given to the opportunities offered by modern synchrotron x-ray sources. The program included plenary talks, progress reports and poster presentations relating to new developments in the field of x-ray and inner-shell processes. The range of topics included: X-ray interactions with atoms, molecules, clusters, surfaces and solids; Decay processes for inner-shell vacancies; X-ray absorption and emission spectroscopy - Photoionization processes; Phenomena associated with highly charged ions and collisions with energetic particles; Electron-spin and -momentum spectroscopy; X-ray scattering and spectroscopy in the study of magnetic systems; Applications in materials science, biology, geosciences, and other disciplines; Elastic and inelastic x-ray scattering processes in atoms and molecules; Threshold phenomena (post-collision interaction, resonant Raman processes, etc.); Nuclear absorption and scattering of x-rays; 'Fourth-generation' x-ray sources; Processes exploiting the polarization and coherence properties of x-ray beams; Developments in experimental techniques (x-ray optics, temporal techniques, detectors); Microscopy, spectromicroscopy, and various imaging techniques; Non-linear processes and x-ray lasers; Ionization and excitation induced by charged particles and by x-rays; and Exotic atoms (including 'hollow' atoms and atoms that contain 'exotic' particles).

  18. On the difference in oscillator strengths of inner shell excitations in noble gases and their alkali neighbors

    SciTech Connect

    Amusia, M.Y.; Baltenkov, A.S.; Zhuravleva, G.I.

    1995-08-01

    It is demonstrated that the oscillator strength of resonant inner-shell excitation in a noble gas atom is considerably smaller than that in its alkali neighbor because in the latter case the effective charge acting upon excited electron is much bigger. With increase of the excitation`s principal quantum number the difference between line intensities in noble gases and their alkali neighbors rapidly disappears. The calculations are performed in the Hartree-Fock approximation and with inclusion of rearrangement effects due to inner vacancy creation and its Auger decay. A paper has been submitted for publication.

  19. Inner-shell photoionized x-ray lasers

    SciTech Connect

    Moon, S.J.

    1998-06-01

    The inner-shell photoionized x-ray lasing scheme is an attractive method for achieving x-ray lasing at short wavelengths, via population inversion following inner-shell photoionization (ISPI). This scheme promises both a short wavelength and a short pulse source of coherent x rays with high average power. In this dissertation a very complete study of the ISPI x-ray laser scheme is done concerning target structure, filter design and lasant medium. An investigation of the rapid rise time of x-ray emission from targets heated by an ultra-short pulse high-intensity optical laser was conducted for use as the x-ray source for ISPI x-ray lasing. Lasing by this approach in C at a wavelength of 45 {angstrom} requires a short pulse (about 50 fsec) driving optical laser with an energy of 1-5 J and traveling wave optics with an accuracy of {approximately} 15 {micro}m. The optical laser is incident on a high-Z target creating a high-density plasma which emits a broadband spectrum of x rays. This x-ray source is passed through a filter to eliminate the low-energy x rays. The remaining high-energy x rays preferentially photoionize inner-shell electrons resulting in a population inversion. Inner-shell photoionized x-ray lasing relies on the large energy of a K-{alpha} transition in the initially neutral lasant. The photo energy required to pump this scheme is only slightly greater than the photon energy of the lasing transition yielding a lasing scheme with high quantum efficiency. However, the overall efficiency is reduced due to low x-ray conversion efficiency and the large probability of Auger decay yielding an overall efficiency of {approximately} 10{sup {minus}7} resulting in an output energy of {micro}J's. They calculate that a driving laser with a pulse duration of 40 fs, a 10{micro}m x 1 cm line focus, and an energy of 1 J gives an effective gain length product (gl) of 10 in C at 45 {angstrom}. At saturation (gl {approximately} 18) they expect an output of {approximately

  20. Inner shell radial pin geometry and mounting arrangement

    DOEpatents

    Leach, David; Bergendahl, Peter Allen

    2002-01-01

    Circumferentially spaced arrays of support pins are disposed through access openings in an outer turbine shell and have projections received in recesses in forward and aft sections of an inner turbine shell supported from the outer shell. The projections have arcuate sides in a circumferential direction affording line contacts with the side walls of the recesses and are spaced from end faces of the recesses, enabling radial and axial expansion and contraction of the inner shell relative to the outer shell. All loads are taken up in a tangential direction by the outer shell with the support pins taking no radial loadings.

  1. An efficient, selective collisional ejection mechanism for inner-shell population inversion in laser-driven plasmas

    NASA Astrophysics Data System (ADS)

    Schroeder, W. Andreas; Nelson, T. R.; Borisov, A. B.; Longworth, J. W.; Boyer, K.; Rhodes, C. K.

    2001-02-01

    A theoretical analysis of laser-driven collisional ejection of inner-shell electrons is presented to explain the previously observed anomalous kilovolt L-shell x-ray emission spectra from atomic Xe cluster targets excited by intense sub-picosecond 248 nm ultraviolet radiation (McPherson A et al 1994 Nature 370 631-4). For incident ponderomotively-driven electrons photoionized by strong above threshold ionization, the collisional ejection mechanism is shown to be highly l-state and significantly n-state (i.e. radially) selective for time periods shorter than the collisional dephasing time of the photoionized electronic wavefunction. The resulting preference for the collisional ejection of 2p electrons by an ionized 4p state produces the measured anomalous Xe(L) emission which contains direct evidence for (i) the generation of Xe27+(2p53d10) and Xe28+(2p53d9) ions exhibiting inner-shell population inversion and (ii) a coherent correlated electron state collision responsible for the production of double 2p vacancies. For longer time periods, the selectivity of this coherent impact ionization mechanism is rapidly reduced by the combined effects of intrinsic quantum mechanical spreading and dephasing - in agreement with the experimentally observed and extremely strong ~λ-6 pump-laser wavelength dependence of the efficiency of inner-shell (2p) vacancy production in Xe clusters excited in underdense plasmas (Kondo K et al 1997 J. Phys. B: At. Mol. Opt. Phys. 30 2707-16).

  2. Inner-Shell Photodetachment of Nickel Negative Ions

    NASA Astrophysics Data System (ADS)

    Dumitriu, Ileana; Bilodeau, Rene; Gibson, Daniel; Walter, Wes; Gorczyca, Thomas; Aguilar, Alex; Rolles, Daniel; Pesic, Zoran; Berrah, Nora

    2015-05-01

    Transition metals are of interest for their catalytic properties and participation of d-orbital electrons in the bonding properties. Theoretical studies of transition metal negative ions are challenging due to strong electron correlation effects and existence of low-lying electronic states as a result of open d-shell configurations. Experimental studies of transition metal negative ions are limited compared with the ions belonging to the main groups of periodic table and these studies have mostly investigated the valence-shell electrons using laser spectroscopy. Our experiment focuses on inner-shell photodetachment studies of Ni- transition metal ions using the Ion-Photon Beamline on the ALS beamline 10.0.1. Inner-shell photodetachment spectrum was recorded over a range of 30 to 90 eV which includes the 3 p threshold for Ni-. The higher-charge state formation was also observed, indicating multi-electron ejection processes. The absolute cross-section for the production of Ni+ will also be presented.

  3. Dislocation-enhanced experimental-scale vacancy loop formation in hcp Zirconium in one single collision cascade

    PubMed Central

    Zhou, Wei; Tian, Jiting; Zheng, Jian; Xue, Jianming; Peng, Shuming

    2016-01-01

    Large defects are the main factor leading to the degradation of material properties under irradiation environments. It is commonly assumed that the large defects are mainly formed through cluster growth under continuous irradiations. Besides this mechanism, recent experiments and simulations show that sometimes an individual ion can also directly create a large defect. Here we report a novel mechanism for the formation of the large defects, as discovered by our Molecular Dynamics (MD) simulations of the collision cascades in hcp Zirconium (Zr): a pre-existing edge dislocation (ED) can significantly promote the nucleation of the vacancy clusters, and even facilitate the direct formation of an experimental-scale large vacancy loop (about 3 nm) in only one single displacement cascade. This dislocation-related mechanism may be the key for understanding the experimental results in the low-dose irradiated Zr where the high-density large dislocation loops are observed but difficult to be explained by the two mechanisms mentioned above. Considering that intrinsic dislocations exist in nearly all crystalline materials, our results provide a significant concept: pre-existing dislocations have a strong influence on the primary damage production, and taking them into account is indispensable for assessing and improving the material’s irradiation-resistance. PMID:26868496

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

    SciTech Connect

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

    2014-03-15

    An analysis is presented of measured and calculated cross sections for inner-shell ionization by electron impact. We describe the essentials of classical and semiclassical models and of quantum approximations for computing ionization cross sections. The emphasis is on the recent formulation of the distorted-wave Born approximation by Bote and Salvat [Phys. Rev. A 77, 042701 (2008)] that has been used to generate an extensive database of cross sections for the ionization of the K shell and the L and M subshells of all elements from hydrogen to einsteinium (Z = 1 to Z = 99) by electrons and positrons with kinetic energies up to 1 GeV. We describe a systematic method for evaluating cross sections for emission of x rays and Auger electrons based on atomic transition probabilities from the Evaluated Atomic Data Library of Perkins et al. [Lawrence Livermore National Laboratory, UCRL-ID-50400, 1991]. We made an extensive comparison of measured K-shell, L-subshell, and M-subshell ionization cross sections and of Lα x-ray production cross sections with the corresponding calculated cross sections. We identified elements for which there were at least three (for K shells) or two (for L and M subshells) mutually consistent sets of cross-section measurements and for which the cross sections varied with energy as expected by theory. The overall average root-mean-square deviation between the measured and calculated cross sections was 10.9% and the overall average deviation was −2.5%. This degree of agreement between measured and calculated ionization and x-ray production cross sections was considered to be very satisfactory given the difficulties of these measurements.

  5. Transition energy and potential energy curves for ionized inner-shell states of CO, O2 and N 2 calculated by several inner-shell multiconfigurational approaches.

    PubMed

    Moura, Carlos E V de; Oliveira, Ricardo R; Rocha, Alexandre B

    2013-05-01

    Potential energy curves and inner-shell ionization energies of carbon monoxide, oxygen and nitrogen molecules were calculated using several forms of the inner-shell multiconfigurational self-consistent field (IS-MCSCF) method-a recently proposed protocol to obtain specifically converged inner-shell states at this level. The particular forms of the IS-MCSCF method designated IS-GVB-PP, IS-FVBL and IS-CASSCF stand for perfect pairing generalized valence bond, full valence bond-like MCSCF and complete active space self consistent field, respectively. A comparison of these different versions of the IS-MCSCF method was carried out for the first time. The results indicate that inner-shell states are described accurately even for the simplest version of the method (IS-GVB-PP). Dynamic correlation was recovered by multireference configuration interaction or multireference perturbation theory. For molecules not having equivalent atoms, all methods led to comparable and accurate transition energies. For molecules with equivalent atoms, the most accurate results were obtained by multireference perturbation theory. Scalar relativistic effects were accounted for using the Douglas-Kroll-Hess Hamiltonian. PMID:23070335

  6. Optimization of ship inner shell to improve the safety of seagoing transport ship

    NASA Astrophysics Data System (ADS)

    Yu, Yan-Yun; Lin, Yan

    2013-09-01

    A practical Ship Inner Shell Optimization Method (SISOM), the purpose of which is to improve the safety of the seagoing transport ship by decreasing the maximum Still Water Bending Moment (SWBM) of the hull girder under all typical loading conditions, is presented in this paper. The objective of SISOM is to make the maximum SWBM minimum, and the section areas of the inner shell are taken as optimization variables. The main requirements of the ship performances, such as cargo hold capacity, propeller and rudder immersion, bridge visibility, damage stability and prevention of pollution etc., are taken as constraints. The penalty function method is used in SISOM to change the above nonlinear constraint problem into an unconstrained one, which is then solved by applying the steepest descent method. After optimization, the optimal section area distribution of the inner shell is obtained, and the shape of inner shell is adjusted according to the optimal section area. SISOM is applied to a product oil tanker and a bulk carrier, and the maximum SWBM of the two ships is significantly decreased by changing the shape of inner shell plate slightly. The two examples prove that SISOM is highly efficient and valuable to engineering practice.

  7. Localized hole effects in inner-shell excitation

    SciTech Connect

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

    1983-10-14

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

  8. Inner Shell Photodetachment Of Na- Using The Multi-Configuration Tamm-Dancoff Approximation

    NASA Astrophysics Data System (ADS)

    Jose, J.; Pradhan, G. B.; Radojevic, V.; Manson, S. T.; Deshmukh, P. C.

    2010-07-01

    The multi-configuration Tamm-Dancoff approximation (MCTD) is used to calculate the inner shell photodetachment of the Na anion. The results reproduce a resonance peak in agreement with existing experimental and theoretical data. The current work emphasizes the importance of doing configuration interaction (CI) type calculations, and proves MCTD is an apt tool to investigate the photoionization/photodetachment process.

  9. Multi-electron coincidence spectroscopy: double photoionization from molecular inner-shell orbitals

    NASA Astrophysics Data System (ADS)

    Hikosaka, Y.; Lablanquie, P.; Penent, F.; Nakano, M.; Ito, K.

    2014-04-01

    We have studied double photoionization from molecular inner-shell orbitals and investigated the properties of the resultant double core-hole states in molecules, by multi-electron coincidence spectroscopy with a magnetic bottle electron spectrometer. A brief summary of our previous studies is presented.

  10. Inner-shell electron effects in strong-field double ionization of Xe

    NASA Astrophysics Data System (ADS)

    Yuan, Zongqiang; Ye, Difa; Liu, Jie; Fu, Libin

    2016-06-01

    We investigate theoretically the inner-shell electron effects in strong-field double ionization of Xe by a comparative study with two different three-dimensional semiclassical models, i.e., the widely used helium-like model and an improved Green-Sellin-Zachor (GSZ) model. The enhanced double-ionization signals through sequential ionization and recollision-induced excitation with subsequent field ionization are identified as two origins of the nonstructured pattern in the correlated electron momentum spectrum observed in a recent experiment [Phys. Rev. Lett. 113, 103001 (2014), 10.1103/PhysRevLett.113.103001]. The relationship between these enhancements and the inner-shell electrons is revealed by back analysis of the classical trajectories.

  11. Characterizing inner-shell with spectral phase interferometry for direct electric-field reconstruction

    PubMed Central

    Mashiko, Hiroki; Yamaguchi, Tomohiko; Oguri, Katsuya; Suda, Akira; Gotoh, Hideki

    2014-01-01

    In many atomic, molecular and solid systems, Lorentzian and Fano profiles are commonly observed in a broad research fields throughout a variety of spectroscopies. As the profile structure is related to the phase of the time-dependent dipole moment, it plays an important role in the study of quantum properties. Here we determine the dipole phase in the inner-shell transition using spectral phase interferometry for direct electric-field reconstruction (SPIDER) with isolated attosecond pulses (IAPs). In addition, we propose a scheme for pulse generation and compression by manipulating the inner-shell transition. The electromagnetic radiation generated by the transition is temporally compressed to a few femtoseconds in the extreme ultraviolet (XUV) region. The proposed pulse-compression scheme may provide an alternative route to producing attosecond pulses of light. PMID:25510971

  12. A new method for ship inner shell optimization based on parametric technique

    NASA Astrophysics Data System (ADS)

    Yu, Yan-Yun; Lin, Yan; Li, Kai

    2015-01-01

    A new method for ship Inner Shell optimization, which is called Parametric Inner Shell Optimization Method (PISOM), is presented in this paper in order to improve both hull performance and design efficiency of transport ship. The foundation of PISOM is the parametric Inner Shell Plate (ISP) model, which is a fully-associative model driven by dimensions. A method to create parametric ISP model is proposed, including geometric primitives, geometric constraints, geometric constraint solving etc. The standard optimization procedure of ship ISP optimization based on parametric ISP model is put forward, and an efficient optimization approach for typical transport ship is developed based on this procedure. This approach takes the section area of ISP and the other dominant parameters as variables, while all the design requirements such as propeller immersion, fore bottom wave slap, bridge visibility, longitudinal strength etc, are made constraints. The optimization objective is maximum volume of cargo oil tanker/cargo hold, and the genetic algorithm is used to solve this optimization model. This method is applied to the optimization of a product oil tanker and a bulk carrier, and it is proved to be effective, highly efficient, and engineering practical.

  13. Ultrafast Excitation of an Inner-Shell Electron by Laser-Induced Electron Recollision.

    PubMed

    Deng, Yunpei; Zeng, Zhinan; Jia, Zhengmao; Komm, Pavel; Zheng, Yinhui; Ge, Xiaochun; Li, Ruxin; Marcus, Gilad

    2016-02-19

    Extreme ultraviolet attosecond pulses, generated by a process known as laser-induced electron recollision, are a key ingredient for attosecond metrology, providing a tool to precisely initiate and probe subfemtosecond dynamics in atoms, molecules, and solids. However, extending attosecond metrology to scrutinize the dynamics of the inner-shell electrons is a challenge, that is because of the lower efficiency in generating the required soft x-ray (ℏω>300  eV) attosecond bursts. A way around this problem is to use the recolliding electron to directly initiate the desired inner-shell process, instead of using the currently low flux x-ray attosecond sources. Such an excitation process occurs in a subfemtosecond time scale, and may provide the necessary "pump" step in a pump-probe experiment. Here we used a few cycle infrared (λ_{0}≈1800  nm) source and observed direct evidence for inner-shell excitations through the laser-induced electron recollision process. It is the first step toward time-resolved core-hole studies in the keV energy range with subfemtosecond time resolution. PMID:26943536

  14. Ultrafast Excitation of an Inner-Shell Electron by Laser-Induced Electron Recollision

    NASA Astrophysics Data System (ADS)

    Deng, Yunpei; Zeng, Zhinan; Jia, Zhengmao; Komm, Pavel; Zheng, Yinhui; Ge, Xiaochun; Li, Ruxin; Marcus, Gilad

    2016-02-01

    Extreme ultraviolet attosecond pulses, generated by a process known as laser-induced electron recollision, are a key ingredient for attosecond metrology, providing a tool to precisely initiate and probe subfemtosecond dynamics in atoms, molecules, and solids. However, extending attosecond metrology to scrutinize the dynamics of the inner-shell electrons is a challenge, that is because of the lower efficiency in generating the required soft x-ray (ℏω >300 eV ) attosecond bursts. A way around this problem is to use the recolliding electron to directly initiate the desired inner-shell process, instead of using the currently low flux x-ray attosecond sources. Such an excitation process occurs in a subfemtosecond time scale, and may provide the necessary "pump" step in a pump-probe experiment. Here we used a few cycle infrared (λ0≈1800 nm ) source and observed direct evidence for inner-shell excitations through the laser-induced electron recollision process. It is the first step toward time-resolved core-hole studies in the keV energy range with subfemtosecond time resolution.

  15. Inner-shell photodetachment from a Si‑ negative ion: strong effect of many-electron correlations

    NASA Astrophysics Data System (ADS)

    Schrange-Kashenock, G.

    2016-06-01

    The first theoretical investigation of the inner-shell single-photodetachment from the Si‑ (1s22s22p63s23p3 4So) negative ion is presented. The partial and total cross sections, the photoelectron phaseshifts, and the parameters of angular anisotropy are calculated in the framework of the many-body theory for L-shell photodetachment from Si‑ ion in the experimentally accessible range of photon energies (7.5–14 Ry). Comparison is made between the calculations of the response of the ionic many-electron system Si‑ to an electromagnetic field at the different levels of approximation: the ‘frozen-field’ random phase approximation with exchange (RPAE), and the static relaxation approximation. The optimal analysis is made when the dynamic relaxation and polarization are included within the Dyson equation method (DEM) simultaneously with the RPAE corrections (the RPAE&DEM approach). It is predicted that the photoexcitation to a resonance state of complex ‘shape-Feschbach’ nature in the open p-shell reveals itself as a prominent resonance structure in the photodetachment cross sections in the energy range of the 2s and 2p inner shell thresholds similar to that in 1s inner-shell photodetachment from C‑ (2006 J. Phys. B: At. Mol. Opt. Phys. 39 1379). The photodetachment dynamical characteristics clearly demonstrate the significance of all the considered many-electron correlations within the RPAE&DEM approach, however the total photodetachment cross section is dominated by a strong resonance peak just after the 2s threshold. Dynamical relaxation (screening) is identified as a decisive factor in the formation of this resonance.

  16. Inner-shell excitations of krypton 3d investigated by electron impact with high resolution

    SciTech Connect

    Yuan Zhensheng; Zhu Linfan; Liu Xiaojing; Li Wenbin; Cheng Huadong; Sun Jianmin; Xu Kezun

    2005-06-15

    The inner-shell excitation spectra of krypton 3d electrons were measured at scattering angles of 0 deg. and 4 deg. by a fast-electron energy-loss spectrometer at an incident energy of 2.5 keV with an energy resolution better than 80 meV. Some interesting optically forbidden transitions were observed and the natural widths of the optically allowed and optically forbidden transitions were analyzed. It shows that the natural widths for the resonances having the same core hole are nearly equal, no matter whether they are optically allowed, optically forbidden, or different members of a Rydberg series.

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

    SciTech Connect

    Lindle, D.W.

    1983-12-01

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

  18. Inner-Shell Photodetachment Thresholds: Unexpected Long-Range Validity of the Wigner Law

    NASA Astrophysics Data System (ADS)

    Bilodeau, R. C.; Bozek, J. D.; Gibson, N. D.; Walter, C. W.; Ackerman, G. D.; Dumitriu, I.; Berrah, N.

    2005-08-01

    Threshold behavior in inner-shell photodetachment is studied for the first time, specifically with 2-, 3-, or 4-electron emission from He- and S-. The threshold shapes are surprisingly consistent with the Wigner threshold law in all cases, despite large PCI effects observed in He-. In S-, the s-wave law is observed to agree with the data over an unprecedented range, more than an order of magnitude greater than predictions, and allows for the observation of the d-wave component. The measurements also demonstrate a means for obtaining precise core-excitation energies of free atoms.

  19. Inner-Shell Photoionization: Teijo A˚berg's Concept of RRRS

    NASA Astrophysics Data System (ADS)

    Armen, G. Bradley

    2003-01-01

    Teijo Åberg 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.

  20. Inner-shell radiation from wire array implosions on the Zebra generator

    SciTech Connect

    Ouart, N. D.; Giuliani, J. L.; Dasgupta, A.; Safronova, A. S.; Kantsyrev, V. L.; Esaulov, A. A.; Shrestha, I.; Weller, M. E.; Shlyaptseva, V.; Osborne, G. C.; Stafford, A.; Keim, S.; Apruzese, J. P.; Clark, R. W.

    2014-03-15

    Implosions of brass wire arrays on Zebra have produced L-shell radiation as well as inner-shell Kα and Kβ transitions. The L-shell radiation comes from ionization stages around the Ne-like charge state that is largely populated by a thermal electron energy distribution function, while the K-shell photons are a result of high-energy electrons ionizing or exciting an inner-shell (1s) electron from ionization stages around Ne-like. The K- and L-shell radiations were captured using two time-gated and two axially resolved time-integrated spectrometers. The electron beam was measured using a Faraday cup. A multi-zone non-local thermodynamic equilibrium pinch model with radiation transport is used to model the x-ray emission from experiments for the purpose of obtaining plasma conditions. These plasma conditions are used to discuss some properties of the electron beam generated by runaway electrons. A simple model for runaway electrons is examined to produce the Kα radiation, but it is found to be insufficient.

  1. Inner-shell radiation from wire array implosions on the Zebra generator

    NASA Astrophysics Data System (ADS)

    Ouart, N. D.; Giuliani, J. L.; Dasgupta, A.; Safronova, A. S.; Kantsyrev, V. L.; Esaulov, A. A.; Shrestha, I.; Weller, M. E.; Shlyaptseva, V.; Osborne, G. C.; Stafford, A.; Keim, S.; Apruzese, J. P.; Clark, R. W.

    2014-03-01

    Implosions of brass wire arrays on Zebra have produced L-shell radiation as well as inner-shell Kα and Kβ transitions. The L-shell radiation comes from ionization stages around the Ne-like charge state that is largely populated by a thermal electron energy distribution function, while the K-shell photons are a result of high-energy electrons ionizing or exciting an inner-shell (1s) electron from ionization stages around Ne-like. The K- and L-shell radiations were captured using two time-gated and two axially resolved time-integrated spectrometers. The electron beam was measured using a Faraday cup. A multi-zone non-local thermodynamic equilibrium pinch model with radiation transport is used to model the x-ray emission from experiments for the purpose of obtaining plasma conditions. These plasma conditions are used to discuss some properties of the electron beam generated by runaway electrons. A simple model for runaway electrons is examined to produce the Kα radiation, but it is found to be insufficient.

  2. Inner shell excitation spectroscopy of transient molecules: HBS, HBO, and H3B3O3

    NASA Astrophysics Data System (ADS)

    Ennis, L. E.; Hitchcock, A. P.

    1999-08-01

    Inner shell electron energy spectroscopy (ISEELS) was used to study HBS, HBO, and H3B3O3, reactive, transient species generated in situ. The reaction of H2S with crystalline boron in a quartz tube was used to produce thioborine (HBS) at ˜1100 °C, and borine (HBO) at ˜1200 °C. The reaction of H2O vapor with crystalline boron in a quartz tube at ˜1200 °C was used to produce boroxine (H3B3O3). These species were identified from their inner shell excitation spectra and mass spectrometry. The B 1s, S 2s, and S 2p ISEEL spectra of HBS, and the B 1s and O 1s spectra of HBO and H3B3O3 are reported and analyzed with the help of GSCF3 ab initio calculations. A reaction scheme is proposed for the generation of HBO from the reaction of H2S and boron in a heated quartz tube.

  3. Inner-Shell Photon-Ionized X-Ray Laser at 45(Angstrom)

    SciTech Connect

    Weber, F; Celliers, P; Moon, S; Snavely, R; Da Silva, L

    2002-02-01

    This report summarizes the major accomplishments of this three-year Laboratory Directed Research and Development (LDRD) Lab Wide (LW) project entitled, ''An Inner-Shell Photo-Ionized X-Ray Laser at 45 {angstrom}'', tracking code 99-LW-042. The most significant accomplishments of this project include the design of a suitable x-ray laser target, the invention of a measurement technique for the determination of rise times of x-ray pulses on the order of 50 femtoseconds, and a novel setup for generating a traveling wave with an ultrashort optical laser pulse. The pump probe technique for rise time measurement will allow us to detect ultrashort x-ray pulses, whose generation by means of a variety of 4th generation light sources is currently under planning elsewhere.

  4. Any Density Changes Near the Inner Shell of the Planetary Nebula NGC 6803?

    NASA Astrophysics Data System (ADS)

    Lee, Seong-Jae; Hyung, S.

    2013-06-01

    Most recent high dispersion spectral data, secured at Lick Observatory in 1995 and 2001, suggested a large density increase near the inner shell boundary of the elliptical ring planetary nebula NGC 6803, e.g., Ne = 8900 (10^3.95) --> 14,400 (10^4.16)/cm^3 in [Ar IV] (Lee and Hyung 2013). We further analyzed high dispersion spectroscopic data observed in 2012 February with the Bohyunsan fiber-fed echelle spectrograph (BOES) attached to the Bohyunsan Observatory 1.8m telescope. The BOES diagnostic line ratios indicate a large change between 2001 & 2012 observations; -0.23, +0.39, +0.13, -0.28 dex for [S II], [O II], [N II], and [Cl III], respectively. For example, the 2012 BOES [Ar IV] line ratio implies a decreasing density of N=11,700 (10^4.07)/cm^3. We discuss the changes of physical conditions and kinematics of NGC 6803.

  5. Retrieving transient conformational molecular structure information from inner-shell photoionization of laser-aligned molecules

    PubMed Central

    Wang, Xu; Le, Anh-Thu; Yu, Chao; Lucchese, R. R.; Lin, C. D.

    2016-01-01

    We discuss a scheme to retrieve transient conformational molecular structure information using photoelectron angular distributions (PADs) that have averaged over partial alignments of isolated molecules. The photoelectron is pulled out from a localized inner-shell molecular orbital by an X-ray photon. We show that a transient change in the atomic positions from their equilibrium will lead to a sensitive change in the alignment-averaged PADs, which can be measured and used to retrieve the former. Exploiting the experimental convenience of changing the photon polarization direction, we show that it is advantageous to use PADs obtained from multiple photon polarization directions. A simple single-scattering model is proposed and benchmarked to describe the photoionization process and to do the retrieval using a multiple-parameter fitting method. PMID:27025410

  6. Retrieving transient conformational molecular structure information from inner-shell photoionization of laser-aligned molecules

    DOE PAGESBeta

    Wang, Xu; Le, Anh -Thu; Yu, Chao; Lucchese, R. R.; Lin, C. D.

    2016-03-30

    We discuss a scheme to retrieve transient conformational molecular structure information using photoelectron angular distributions (PADs) that have averaged over partial alignments of isolated molecules. The photoelectron is pulled out from a localized inner-shell molecular orbital by an X-ray photon. We show that a transient change in the atomic positions from their equilibrium will lead to a sensitive change in the alignment-averaged PADs, which can be measured and used to retrieve the former. Exploiting the experimental convenience of changing the photon polarization direction, we show that it is advantageous to use PADs obtained from multiple photon polarization directions. Lastly, amore » simple single-scattering model is proposed and benchmarked to describe the photoionization process and to do the retrieval using a multiple-parameter fitting method.« less

  7. Retrieving transient conformational molecular structure information from inner-shell photoionization of laser-aligned molecules

    NASA Astrophysics Data System (ADS)

    Wang, Xu; Le, Anh-Thu; Yu, Chao; Lucchese, R. R.; Lin, C. D.

    2016-03-01

    We discuss a scheme to retrieve transient conformational molecular structure information using photoelectron angular distributions (PADs) that have averaged over partial alignments of isolated molecules. The photoelectron is pulled out from a localized inner-shell molecular orbital by an X-ray photon. We show that a transient change in the atomic positions from their equilibrium will lead to a sensitive change in the alignment-averaged PADs, which can be measured and used to retrieve the former. Exploiting the experimental convenience of changing the photon polarization direction, we show that it is advantageous to use PADs obtained from multiple photon polarization directions. A simple single-scattering model is proposed and benchmarked to describe the photoionization process and to do the retrieval using a multiple-parameter fitting method.

  8. Advances Toward Inner-Shell Photo-Ionization X-Ray Lasing at 45 (Angstrom)

    SciTech Connect

    Moon, S J; Weber, F A; Celliers, P M; Eder, D C

    2002-07-18

    The inner-shell photo-ionization (ISPI) scheme requires photon energies at least high enough to photo-ionize the K-shell. {approx}286 eV, in the case of carbon. As a consequence of the higher cross-section, the inner-shell are selectively knocked out, leaving a hole state 1s2s{sup 2}2p{sup 2} in the singly charged carbon ion. This generates a population inversion to the radiatively connected state 1s{sup 2}2s{sup 2}2p in C+, leading to gain on the 1s-2p transition at 45 {angstrom}. The resonant character of the lasing transition in the single ionization state intrinsically allows much higher quantum efficiency compared to other schemes. Competing processes that deplete the population inversion include auto-ionization, Auger decay, and in particular collisional ionization of the outer-shell electrons by electrons generated during photo-ionization. These competing processes rapidly quench the gain. Consequently, the pump method must be capable of populating the inversion at a rate faster than the competing processes. This can be achieved by an ultra-fast, high intensity laser that is able to generate an ultra-fast, bright x-ray source. With current advances in the development of high-power, ultra-short pulse lasers it is possible to realize fast x-ray sources based that can deliver powerful pulses of light in the multiple hundred terawatt regime and beyond. They will discuss in greater detail concept, target design and a series of x-ray spectroscopy investigations they have conducted in order to optimize the absorber/x-ray converter--filter package.

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

    NASA Astrophysics Data System (ADS)

    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. Inner-shell photoionization and core-hole decay of Xe and XeF2

    NASA Astrophysics Data System (ADS)

    Southworth, Stephen; Picón, Antonio; Lehmann, C. Stefan; Wehlitz, Ralf; Cheng, Lan; Stanton, John F.

    2015-03-01

    Molecular effects on inner-shell photoionization and core-hole decay are explored by comparing cross sections and partial ion yields of Xe and XeF2 from Xe 3d and F 1s subshells in the 660-740 eV range. The Xe 3d- ɛf continuum shape resonances dominate the total cross sections, but prominent resonances appear in the XeF2 cross section due to excitation of Xe 3d and F 1s electrons to the lowest unoccupied molecular orbital (LUMO), a delocalized anti-bonding MO. Relativistic coupled-cluster calculations were performed to identify the subshell ionization thresholds, the LUMO resonances and their oscillator strengths. Comparison of the Xe charge state distributions of the atom and molecule show a general shift to lower charge states in XeF2. The measurements support a model of core-hole decay in which charge is redistributed from Xe to the F ligands and energetic F ions are produced by Coulombic fragmentation. Supported by the Chemical Sciences, Geosciences, and Biosciences Division, Office of Basic Energy Sciences, Office of Science, US Dept of Energy, Contract DE-AC02-06CH11357.

  11. Use of the Bethe Equation for Inner-Shell Ionization by Electron Impact

    PubMed Central

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

    2016-01-01

    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, with L3-subshell ionization cross sections for Xe, and with 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. 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. PMID:27546903

  12. The influence of inner-shell electron promotion on charge exchange processes in low energy ion scattering from surfaces

    NASA Astrophysics Data System (ADS)

    Ting Li; MacDonald, R. J.

    1997-11-01

    The influence of inner-shell electron promotion on charge exchange in low energy (1-7 keV) Ne + ions scattered from the Cu (1 0 0), Ni (1 0 0) and Fe (1 1 0) surfaces has been studied systematically. The yield of Ne + ion scattered from these surfaces has been measured as a function of incident ion energy under various scattering geometries. The relative Ne + ion fraction, which is proportional to the normalised ion yield divided by the differential scattering cross section, is studied and an empirical formula for relative ion fraction has been extracted. The formula combines the charge exchanges along the incoming trajectory, during the close encounter, and along the outgoing trajectory into one simple expression. It can be concluded that inner-shell electron excitations during close encounters contribute significantly to the charge exchange in the scattering systems studied in this work.

  13. Progress on precision measurements of inner shell transitions in highly charged ions at an ECR ion source

    SciTech Connect

    Szabo, Csilla I.; Indelicato, Paul; LeBigot, Eric-Olivier; Vallette, Alexandre; Amaro, Pedro; Guerra, Mauro; Gumberidze, Alex

    2012-05-25

    Inner shell transitions of highly charged ions produced in the plasma of an Electron Cyclotron Resonance Ion Source (ECRIS) were observed the first time by a Double Crystal Spectrometer (DCS). The DCS is a well-used tool in precision x-ray spectroscopy due to its ability of precision wavelength measurement traced back to a relative angle measurement. Because of its requirement for a bright x-ray source the DCS has not been used before in direct measurements of highly charged ions (HCI). Our new precision measurement of inner shell transitions in HCI is not just going to provide new x-ray standards for quantum metrology but can also give information about the plasma in which the ions reside. Ionic temperatures and with that the electron density can be determined by thorough examination of line widths measured with great accuracy.

  14. Multilayer nanoparticles with a magnetite core and a polycation inner shell as pH-responsive carriers for drug delivery

    NASA Astrophysics Data System (ADS)

    Guo, Miao; Yan, Yu; Liu, Xiaozhou; Yan, Husheng; Liu, Keliang; Zhang, Hongkai; Cao, Youjia

    2010-03-01

    Nanocarriers with multilayer core-shell architecture were prepared by coating a superparamagnetic Fe3O4 core with a triblock copolymer. The first block of the copolymer formed the biocompatible outermost shell of the nanocarrier. The second block that contains amino groups and hydrophobic moiety formed the inner shell. The third block bound tightly onto the Fe3O4 core. Chlorambucil (an anticancer agent) and indomethacin (an anti-inflammation agent), each containing a carboxyl group and a hydrophobic moiety, were loaded into the amino-group-containing inner shell by a combination of ionic and hydrophobic interactions. The release rate of the loaded drugs was slow at pH 7.4, mimicking the blood environment, whereas the release rate increased significantly at acidic pH, mimicking the intracellular conditions in the endosome/lysosome. This can be attributed to the disruption of the ionic bond caused by protonation of the carboxylate anion of the drugs and the swelling of the inner shell caused by protonation of the amino groups.

  15. Influence of the Inner-Shell Architecture on Quantum Yield and Blinking Dynamics in Core/Multishell Quantum Dots.

    PubMed

    Bajwa, Pooja; Gao, Feng; Nguyen, Anh; Omogo, Benard; Heyes, Colin D

    2016-03-01

    Choosing the composition of a shell for QDs is not trivial, as both the band-edge energy offset and interfacial lattice mismatch influence the final optical properties. One way to balance these competing effects is by forming multishells and/or gradient-alloy shells. However, this introduces multiple interfaces, and their relative effects on quantum yield and blinking are not yet fully understood. Here, we undertake a systematic, comparative study of the addition of inner shells of a single component versus gradient-alloy shells of cadmium/zinc chalogenides onto CdSe cores, and then capping with a thin ZnS outer shell to form various core/multishell configurations. We show that architecture of the inner shell between the CdSe core and the outer ZnS shell significantly influences both the quantum yield and blinking dynamics, but that these effects are not correlated-a high ensemble quantum yield doesn't necessarily equate to reduced blinking. Two mathematical models have been proposed to describe the blinking dynamics-the more common power-law model and a more recent multiexponential model. By binning the same data with 1 and 20 ms resolution, we show that the on times can be better described by the multiexponential model, whereas the off times can be better described by the power-law model. We discuss physical mechanisms that might explain this behavior and how it can be affected by the inner-shell architecture. PMID:26693950

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

    SciTech Connect

    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.

  17. Decay pathways after Xe 3d inner shell ionization using a multi-electron coincidence technique

    NASA Astrophysics Data System (ADS)

    Suzuki, I. H.; Hikosaka, Y.; Shigemasa, E.; Lablanquie, P.; Penent, F.; Soejima, K.; Nakano, M.; Kouchi, N.; Ito, K.

    2011-04-01

    Cascade Auger electron emission following Xe 3d photoionization has been investigated using a multi-electron coincidence technique, which utilizes an electron spectrometer of magnetic bottle type. It has been found that the Xe2+ states of the 4p-14d-1 configuration, formed by the Auger decay of the Xe+ 3d3/2, 5/2-1 states, dominantly turn into triply charged states of the 4d-25p-1/4d-25s-1 configurations. The Xe2+ 4s-14d-1 states, formed by the 3d Auger decay, yield the 4p-14d-15p-1 states as well as the 4d-3 states. From the coincidence spectrum among three Auger electrons, it is suggested that the Xe2+ 4p-14d-1 states give rise to the following cascade processes: 4p-14d-1 → 4d-25p-1 → 4d-15p-3.

  18. Electron impact action spectroscopy of mass/charge selected macromolecular ions: Inner-shell excitation of ubiquitin protein

    NASA Astrophysics Data System (ADS)

    Ranković, Miloš Lj.; Giuliani, Alexandre; Milosavljević, Aleksandar R.

    2016-02-01

    We have performed inner-shell electron impact action spectroscopy of mass and charge selected macromolecular ions. For this purpose, we have coupled a focusing electron gun with a linear quadrupole ion trap mass spectrometer. This experiment represents a proof of principle that an energy-tunable electron beam can be used in combination with radio frequency traps as an activation method in tandem mass spectrometry (MS2) and allows performing action spectroscopy. Electron impact MS2 spectra of multiply protonated ubiquitin protein ion have been recorded at incident electron energies around the carbon 1 s excitation. Both MS2 and single ionization energy dependence spectra are compared with literature data obtained using the soft X-ray activation conditions.

  19. Electron impact action spectroscopy of mass/charge selected macromolecular ions: Inner-shell excitation of ubiquitin protein

    DOE PAGESBeta

    Rankovic, Milos Lj.; Giuliani, Alexandre; Milosavljevic, Aleksandar R.

    2016-02-11

    In this study, we have performed inner-shell electron impact action spectroscopy of mass and charge selected macromolecular ions. For this purpose, we have coupled a focusing electron gun with a linear quadrupole ion trap mass spectrometer. This experiment represents a proof of principle that an energy-tunable electron beam can be used in combination with radio frequency traps as an activation method in tandem mass spectrometry (MS2) and allows performing action spectroscopy. Electron impact MS2 spectra of multiply protonated ubiquitin protein ion have been recorded at incident electron energies around the carbon 1s excitation. Both MS2 and single ionization energy dependencemore » spectra are compared with literature data obtained using the soft X-ray activation conditions.« less

  20. Exciton Lines in Luminescence Spectra of NixZn1-xO under Inner Shell Excitation

    NASA Astrophysics Data System (ADS)

    Churmanov, V. N.; Sokolov, V. I.; Gruzdev, N. B.; Ivanov, V. Yu.; Pustovarov, V. A.

    The paper presents the results of the study of two narrow luminescence lines I1 and I2 at the energies of 3.339 and 3.393 eV respectively in NiO and solid state solution Ni0.6Zn0.4O. The luminescence spectroscopy with a sub-nanosecond time resolution upon selective photoexcitation in the energy range of absorption of the inner shells Zn M- and Ni L2,3- edges of Zn- and Ni- ions was used to promote proposed earlier mechanism of origin of luminescence lines I1 and I2. Photoluminescence decay kinetics of NiO and solid state solution Ni0.6Zn0.4O under soft x-ray excitation are discussed. The doublet of I1 and I2 lines is believed to arise due to the radiative annihilation of p-d excitons.

  1. Compton scattering cross section for inner-shell electrons in the relativistic impulse approximation

    NASA Astrophysics Data System (ADS)

    Stutz, G. E.

    2014-01-01

    Total Compton scattering cross sections and inelastic scattering factors for bound electron states of several elements have been evaluated in the framework of the relativistic impulse approximation (RIA). The accuracy of different approximate expressions for the singly differential cross section within the RIA is discussed. Accurate evaluations of bound state scattering factors require the use of the full RIA expression. Compton scattering from K-shell electrons dominates over the photoelectric absorption at higher energies. Energy values at which the Compton interaction become the main process of creation of K-shell vacancies are assessed. The role of binding effects in Compton processes at lower energies are clearly evidenced by the computed total cross sections. Calculated K-shell ionization total cross sections, defined as the sum of the photoelectric absorption and the Compton scattering cross sections, are in good agreement with available experimental data. The total Compton cross section for the 2s atomic orbital exhibits a shoulder-like structure, which can be traced back to the node structure of the 2s wave function.

  2. Lifetime of inner-shell hole states of Ar (2p) and Kr (3d) using equation-of-motion coupled cluster method

    SciTech Connect

    Ghosh, Aryya; Vaval, Nayana; Pal, Sourav

    2015-07-14

    Auger decay is an efficient ultrafast relaxation process of core-shell or inner-shell excited atom or molecule. Generally, it occurs in femto-second or even atto-second time domain. Direct measurement of lifetimes of Auger process of single ionized and double ionized inner-shell state of an atom or molecule is an extremely difficult task. In this paper, we have applied the highly correlated complex absorbing potential-equation-of-motion coupled cluster (CAP-EOMCC) approach which is a combination of CAP and EOMCC approach to calculate the lifetime of the states arising from 2p inner-shell ionization of an Ar atom and 3d inner-shell ionization of Kr atom. We have also calculated the lifetime of Ar{sup 2+}(2p{sup −1}3p{sup −1}) {sup 1}D, Ar{sup 2+}(2p{sup −1}3p{sup −1}) {sup 1}S, and Ar{sup 2+}(2p{sup −1}3s{sup −1}) {sup 1}P double ionized states. The predicted results are compared with the other theoretical results as well as experimental results available in the literature.

  3. Inner-Shell Absorption Lines of Fe 6-Fe 16: a Many-Body Perturbation Theory Approach

    SciTech Connect

    Gu, Ming F.; Holczer, Tomer; Behar, Ehud; Kahn, Steven M.; /KIPAC, Menlo Park

    2006-01-17

    We provide improved atomic calculation of wavelengths, oscillator strengths, and autoionization rates relevant to the 2 -> 3 inner-shell transitions of Fe VI-XVI, the so-called Fe M-shell unresolved transition array (UTA). A second order many-body perturbation theory is employed to obtain accurate transition wavelengths, which are systematically larger than previous theoretical results by 15-45 mA. For a few transitions of Fe XVI and Fe XV where laboratory measurements exist, our new wavelengths are accurate to within a few mA. Using these new calculations, the apparent discrepancy in the velocities between the Fe M-shell UTA and other highly ionized absorption lines in the outflow of NGC 3783 disappears. The oscillator strengths in our new calculation agree well with the previous theoretical data, while the new autoionization rates are significantly larger, especially for lower charge states. We attribute this discrepancy to the missing autoionization channels in the previous calculation. The increased autoionization rates may slightly affect the column density analysis of the Fe M-shell UTA for sources with high column density and very low turbulent broadening. The complete set of atomic data is provided as an electronic table.

  4. Stability of Helium Clusters during Displacement Cascades

    SciTech Connect

    Yang, Li; Zu, Xiaotao T.; Xiao, H. Y.; Gao, Fei; Heinisch, Howard L.; Kurtz, Richard J.; Wang, Zhiguo; Liu, K. Z.

    2007-02-01

    The interaction of displacement cascades with helium-vacancy clusters is investigated using molecular dynamics simulations. The He-vacancy clusters initially consist of 20 vacancies with a Helium-to-vacancy ratio ranging from 0.2 to 3. The primary knock-on atom (PKA) energy, Ep, varies from 2 keV to 10 keV, and the PKA direction is chosen such that a displacement cascade is able to directly interact with a helium-vacancy cluster. The simulation results show that the effect of displacement cascades on a helium-vacancy cluster strongly depends on both the helium-to-vacancy ratio and the PKA energy. For the same PKA energy, the size of helium-vacancy clusters increases with the He/V ratio, but for the same ratio, the cluster size changes more significantly with increasing PKA energy. It has been observed that the He-vacancy clusters can be dissolved when the He/V ratio less than 1, but they are able to re-nucleate during the thermal spike phase, forming small He-V nuclei. When the He/V ratio is larger than 1, the He-V clusters can absorb a number of vacancies produced by displacement cascades, forming larger He-V clusters. These results are discussed in terms of PKA energy, helium-to-vacancy ratio, number of vacancies produced by cascades, and mobility of helium atoms.

  5. High resolution X-ray spectra of solar flares. V - Interpretation of inner-shell transitions in Fe XX-Fe XXIII

    NASA Technical Reports Server (NTRS)

    Doschek, G. A.; Feldman, U.; Cowan, R. D.

    1981-01-01

    The paper examines high-resolution solar flare iron line spectra recorded between 1.82 and 1.97 A by a spectrometer flown by the Naval Research Laboratory on an Air Force spacecraft launched on 1979 February 24. The emission line spectrum is due to inner-shell transitions in the ions Fe XX-Fe XXV. Using theoretical spectra and calculations of line intensities obtained by methods discussed by Merts, Cowan, and Magee (1976), electron temperatures as a function of time for two large class X flares are derived. These temperatures are deduced from intensities of lines of Fe XXII, Fe XXIII, and Fe XXIV. The determination of the differential emission measure between about 12-million and 20-million K using these temperatures is considered. The possibility of determining electron densities in flare and tokamak plasmas using the inner-shell spectra of Fe XXI and Fe XX is discussed.

  6. Charge and Nuclear Dynamics Induced by Deep Inner-Shell Multiphoton Ionization of CH3I Molecules by Intense X-ray Free-Electron Laser Pulses.

    PubMed

    Motomura, Koji; Kukk, Edwin; Fukuzawa, Hironobu; Wada, Shin-ichi; Nagaya, Kiyonobu; Ohmura, Satoshi; Mondal, Subhendu; Tachibana, Tetsuya; Ito, Yuta; Koga, Ryosuke; Sakai, Tsukasa; Matsunami, Kenji; Rudenko, Artem; Nicolas, Christophe; Liu, Xiao-Jing; Miron, Catalin; Zhang, Yizhu; Jiang, Yuhai; Chen, Jianhui; Anand, Mailam; Kim, Dong Eon; Tono, Kensuke; Yabashi, Makina; Yao, Makoto; Ueda, Kiyoshi

    2015-08-01

    In recent years, free-electron lasers operating in the true X-ray regime have opened up access to the femtosecond-scale dynamics induced by deep inner-shell ionization. We have investigated charge creation and transfer dynamics in the context of molecular Coulomb explosion of a single molecule, exposed to sequential deep inner-shell ionization within an ultrashort (10 fs) X-ray pulse. The target molecule was CH3I, methane sensitized to X-rays by halogenization with a heavy element, iodine. Time-of-flight ion spectroscopy and coincident ion analysis was employed to investigate, via the properties of the atomic fragments, single-molecule charge states of up to +22. Experimental findings have been compared with a parametric model of simultaneous Coulomb explosion and charge transfer in the molecule. The study demonstrates that including realistic charge dynamics is imperative when molecular Coulomb explosion experiments using short-pulse facilities are performed. PMID:26267186

  7. Observation of Doubly-Excited States in CALCIUM(17+) and Inner Shell-Photoexcitations in Argon, Potassium and Rubidium

    NASA Astrophysics Data System (ADS)

    Suleiman, Jamal A.

    High resolution X-ray spectroscopy is used to study (A) simultaneous electron-excitation and electron capture in the collision of calcium ions with argon atoms; these studies are important because of the close relationship to dielectronic recombination (DR) which plays an important role in energy-transfer processes in astrophysical and laboratory plasmas; (B) single and double inner-shell photoexcitations of potassium, rubidium and argon; these measurements can lead to very precise tests of electron correlation effects, such as Breit interaction, and QED effects in many electron systems. In the first case, Ca^{18+ } and Ca^{19+} ions from the ATLAS accelerator at Argonne National Laboratory, at energies near 100 MeV, were directed to an argon gas target. X-ray spectra near 3.9 KeV were collected using a high-resolution X-ray spectrometer. We have resolved transitions from doubly-excited 1s2lnl^ ' states to singly-excited 1s ^2nl^' states in lithium -like calcium. Comparison of the experimental wavelengths and intensities with relativistic Hartree-Fock calculations shows very good agreement. In the second case, we have obtained high spectral resolution absorption spectra of potassium near K-, KN -, and KM-edges, rubidium near K- and KO edges, and argon near K-, KM-, and KL-edges. The measurements were made at the X-24A and X-23A2 beamlines at the National Synchrotron Light Source at Brookhaven National Laboratory. Preliminary identifications of most the peaks are made using Dirac Hartree-Fock calculations. Comparisons of the experimental wavelengths and intensities with relativistic Hartree-Fock calculations show very good agreement.

  8. Measurement of wavelengths and lamb shifts for inner-shell transitions in Fe XVIII-XXIV. [from solar flare X-ray spectra

    NASA Technical Reports Server (NTRS)

    Seely, J. F.; Feldman, U.; Safronova, U. I.

    1986-01-01

    The wavelengths of inner-shell 1s-2p transitions in the ions Fe XVIII-XXIV have been measured in solar flare spectra recorded by the Naval Research Laboratory crystal spectrometer (SOLFLEX) on the Air Force P78-1 spacecraft. The measurements are compared with previous measurements and with recently calculated wavelengths. It is found that the measured wavelengths are systematically larger than the wavelengths calculated using the Z-expansion method by up to 0.65 mA. For the more highly charged ions, these differences can be attributed to the QED contributions to the transition energies that are not included in the Z-expansion calculations.

  9. MEASUREMENT AND MODELING OF Na-LIKE Fe XVI INNER-SHELL SATELLITES BETWEEN 14.5 A AND 18 A

    SciTech Connect

    Graf, A.; Beiersdorfer, P.; Brown, G. V.; Gu, M. F.

    2009-04-20

    We have used the University of California Lawrence Livermore National Laboratory's EBIT-I electron beam ion trap to perform measurements of the wavelengths and relative intensities of the X-ray lines from inner-shell satellite transitions in sodium-like Fe XVI. The measurements were carried out with high-resolution crystal and grating spectrometers and covered the 14.5-18 A wavelength band. In contrast to some predicted line strengths and positions found in the literature, our results show that the strongest relatively unblended inner-shell satellites of Fe XVI are located near 15.2 A. This is near the location of the 3d{yields} 2p intercombination line in Fe XVII. Calculations using the Flexible Atomic Code (FAC) are presented. The average deviation between the EBIT-I measurements and the FAC calculations for the wavelength positions and line ratios are 22 mA and a factor of 2.3, respectively, where the average is taken over the ten features included in this work.

  10. Ion charge-resolved branching in decay of inner shell holes in Xe up to 1200 eV

    NASA Astrophysics Data System (ADS)

    Eland, J. H. D.; Slater, C.; Zagorodskikh, S.; Singh, R.; Andersson, J.; Hult-Roos, A.; Lauer, A.; Squibb, R. J.; Feifel, R.

    2015-10-01

    Using a new multi-electron multi-ion coincidence apparatus and soft x-ray synchrotron radiation we have determined branching ratios to final Xe n+ states with 2 < n < 9 from the 4d-1, 4p-1, 4s-1, 3d-1 and 3p-1 Xe+ hole states. The coincident electron spectra give information on the Auger cascade pathways. We show that by judicious choice of coincident electrons, almost pure single charge states of the final ions can be selected.

  11. Solid-state effects and atomiclike effects on shallow inner-shell-electron energy-loss spectra of a cation p or d hole in sulfides

    NASA Astrophysics Data System (ADS)

    Ohno, Youichi

    1994-03-01

    Inner-shell-electron energy-loss spectroscopy studies have been done for the systems in which a shallow p or d core hole exists in the final state of a cation. Optically allowed and forbidden transitions have been distinguished from spectral variations due to the breakdown of dipole selection rules. The Ti and V M2,3 spectra and the Zr, Nb, and Mo M4,5 spectra in layered transition-metal disulfides and related misfit-layer compounds are well explained in terms of the energy-band structures. The overall structures of the Pb and Bi O4,5 spectra are understood within the atomic model containing j-j coupling. The Sn N4,5 spectra in SnS and SnS2 are intermediate between them. A reasonable explanation is given by both the atomic model and the band-structure model.

  12. Mango core inner shell membrane template-directed synthesis of porous ZnO films and their application for enzymatic glucose biosensor

    NASA Astrophysics Data System (ADS)

    Zhou, Yu; Wang, Lei; Ye, Zhizhen; Zhao, Minggang; Cai, Hui; Huang, Jingyun

    2013-11-01

    Micro/nano-porous ZnO films were synthesized through a simple biotemplate-directed method using mango core inner shell membranes as templates. The achieved ZnO films with wrinkles on the surface are combined of large holes and small pores in the bulk. High specific surface area, numerous microspaces, and small channels for fluid circulation provided by this unique structure along with the good biocompatibility and electron communication features of ZnO material make the product an ideal platform for the immobilization of enzymes The fabricated glucose biosensor based on the porous ZnO films exhibits good selective detection ability of analyte with good stability, high sensitivity of 50.58 μA cm-2 mM-1 and a wide linear range of 0.2-5.6 mM along with a low detection limit of 10 μM.

  13. Modeling energy dependence of the inner-shell x-ray emission produced by femtosecond-pulse laser irradiation of xenon clusters

    SciTech Connect

    Colgan, James P

    2008-01-01

    We employ the Los Alamos suite of atomic physics codes to model the inner-shell x-ray emission spectrum of xenon and compare results with those obtained via high-resolution x-ray spectroscopy of xenon clusters irradiated by 30 fs Ti:Sa laser pulses. We find that the commonly employed configuration average approximation breaks down and significant spin-orbit splitting necessitates a detailed level accounting. Additionally, we reproduce an interesting spectral trend for a series of experimental spectra taken with varying pulse energy for fixed pulse duration. To simulate the experimental measurements at increasing beam energies, we find that spectral modeling requires an increased hot electron fraction, but decreased atomic density and bulk electron temperature. We believe these latter conditions to be a result of partial cluster destruction due to the increased energy in the laser prepulse.

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

    SciTech Connect

    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.

  15. Stochastic annealing simulation of cascades in metals

    SciTech Connect

    Heinisch, H.L.

    1996-04-01

    The stochastic annealing simulation code ALSOME is used to investigate quantitatively the differential production of mobile vacancy and SIA defects as a function of temperature for isolated 25 KeV cascades in copper generated by MD simulations. The ALSOME code and cascade annealing simulations are described. The annealing simulations indicate that the above Stage V, where the cascade vacancy clusters are unstable,m nearly 80% of the post-quench vacancies escape the cascade volume, while about half of the post-quench SIAs remain in clusters. The results are sensitive to the relative fractions of SIAs that occur in small, highly mobile clusters and large stable clusters, respectively, which may be dependent on the cascade energy.

  16. Primary-energy dependence of the momentum transfer in reflection inner-shell-electron energy-loss spectra of layered transition-metal dichalcogenides

    NASA Astrophysics Data System (ADS)

    Ohno, Youichi

    1987-11-01

    Sulfur L2.3 and titanium L2.3 and M2.3 inner-shell-electron energy-loss spectra in 1T-TiS2, 1T-TiSe2, 2H-TaS2, and 2H-MoS2 have been measured at various primary energies in the reflection mode. A remarkable primary-energy dependence is found. As the primary energy decreases, the first peak that is assigned to the unoccupied t2g band for the 1T compounds & band for 2H-TaS2 increases in intensity relative to the second peak. The peak positions are almost unchanged. They are in agreement with those of band-structure calculations and x-ray absorption spectra. The primary-energy dependence has been discussed mainly in terms of the breakdown of dipole selection rules due to momentum transfer involved in the inelastic scattering process and anisotropy in electronic structures.

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

    SciTech Connect

    Peek, J.M.; Halbleib, J.A.

    1983-01-01

    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.

  18. Atomic Data for the K-Vacancy States of Fe XXIV

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

    As part of a project to compute improved atomic data for the spectral modeling of iron K lines, we report extensive calculations and comparisons of atomic data for K-vacancy states in Fe XXIV. The data sets include: (i) energy levels, line wavelengths, radiative and Auger rates; (ii) inner-shell electron impact excitation rates and (iii) fine structure inner-shell photoionization cross sections. The calculations of energy levels and radiative and Auger rates have involved a detailed study of orbital representations, core relaxation, configuration interaction, relativistic corrections, cancellation effects and semi-empirical corrections. It is shown that a formal treatment of the Breit interaction is essential to render the important magnetic correlations that take part in the decay pathways of this ion. As a result, the accuracy of the present A-values is firmly ranked at better than 10% while that of the Auger rates at only 15%. The calculations of collisional excitation and photoionization cross sections take into account the effects of radiation and spectator Auger dampings. In the former, these effects cause significant attenuation of resonances leading to a good agreement with a simpler method where resonances are excluded. In the latter, resonances converging to the K threshold display symmetric profiles of constant width that causes edge smearing.

  19. Atomic Data for the K-vacancy States of Fe XXIV

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

    As part of a project to compute improved atomic data for the spectral modeling of iron K lines, we report extensive calculations and comparisons of atomic data for K-vacancy states in Fe XXIV. The data sets include: (i) energy levels, line wavelengths, radiative and Auger rates; (ii) inner-shell electron impact excitation rates and (iii) fine structure inner-shell photoionization cross sections. The calculations of energy levels and radiative and Auger rates have involved a detailed study of orbital representations, core relaxation, configuration interaction, relativistic corrections, cancellation effects and semi-empirical corrections. It is shown that a formal treatment of the Breit interaction is essential to render the important magnetic correlations that take part in the decay pathways of this ion. As a result, the accuracy of the present A-values is firmly ranked at better than 10% while that of the Auger rates at only 15%. The calculations of collisional excitation and photoionization cross sections take into account the effects of radiation and spectator Auger dampings. In the former, these effects cause significant attenuation of resonances leading to a good agreement with a simpler method where resonances are excluded. In the latter, resonances converging to the K threshold display symmetric profiles of constant width that causes edge smearing.

  20. Atomic inner-shell laser at 1.5-ångström wavelength pumped by an X-ray free-electron laser

    NASA Astrophysics Data System (ADS)

    Yoneda, Hitoki; Inubushi, Yuichi; Nagamine, Kazunori; Michine, Yurina; Ohashi, Haruhiko; Yumoto, Hirokatsu; Yamauchi, Kazuto; Mimura, Hidekazu; Kitamura, Hikaru; Katayama, Tetsuo; Ishikawa, Tetsuya; Yabashi, Makina

    2015-08-01

    Since the invention of the first lasers in the visible-light region, research has aimed to produce short-wavelength lasers that generate coherent X-rays; the shorter the wavelength, the better the imaging resolution of the laser and the shorter the pulse duration, leading to better temporal resolution in probe measurements. Recently, free-electron lasers based on self-amplified spontaneous emission have made it possible to generate a hard-X-ray laser (that is, the photon energy is of the order of ten kiloelectronvolts) in an ångström-wavelength regime, enabling advances in fields from ultrafast X-ray spectrosopy to X-ray quantum optics. An atomic laser based on neon atoms and pumped by a soft-X-ray (that is, a photon energy of less than one kiloelectronvolt) free-electron laser has been achieved at a wavelength of 14 nanometres. Here, we use a copper target and report a hard-X-ray inner-shell atomic laser operating at a wavelength of 1.5 ångströms. X-ray free-electron laser pulses with an intensity of about 1019 watts per square centimetre tuned to the copper K-absorption edge produced sufficient population inversion to generate strong amplified spontaneous emission on the copper Kα lines. Furthermore, we operated the X-ray free-electron laser source in a two-colour mode, with one colour tuned for pumping and the other for the seed (starting) light for the laser.

  1. Atomic inner-shell laser at 1.5-ångström wavelength pumped by an X-ray free-electron laser.

    PubMed

    Yoneda, Hitoki; Inubushi, Yuichi; Nagamine, Kazunori; Michine, Yurina; Ohashi, Haruhiko; Yumoto, Hirokatsu; Yamauchi, Kazuto; Mimura, Hidekazu; Kitamura, Hikaru; Katayama, Tetsuo; Ishikawa, Tetsuya; Yabashi, Makina

    2015-08-27

    Since the invention of the first lasers in the visible-light region, research has aimed to produce short-wavelength lasers that generate coherent X-rays; the shorter the wavelength, the better the imaging resolution of the laser and the shorter the pulse duration, leading to better temporal resolution in probe measurements. Recently, free-electron lasers based on self-amplified spontaneous emission have made it possible to generate a hard-X-ray laser (that is, the photon energy is of the order of ten kiloelectronvolts) in an ångström-wavelength regime, enabling advances in fields from ultrafast X-ray spectrosopy to X-ray quantum optics. An atomic laser based on neon atoms and pumped by a soft-X-ray (that is, a photon energy of less than one kiloelectronvolt) free-electron laser has been achieved at a wavelength of 14 nanometres. Here, we use a copper target and report a hard-X-ray inner-shell atomic laser operating at a wavelength of 1.5 ångströms. X-ray free-electron laser pulses with an intensity of about 10(19) watts per square centimetre tuned to the copper K-absorption edge produced sufficient population inversion to generate strong amplified spontaneous emission on the copper Kα lines. Furthermore, we operated the X-ray free-electron laser source in a two-colour mode, with one colour tuned for pumping and the other for the seed (starting) light for the laser. PMID:26310765

  2. A comparative study of the inner-shell and the ionic line radiation from ultra-short laser-produced magnesium plasma

    NASA Astrophysics Data System (ADS)

    Arora, Vipul; Anant Naik, Prasad; Chakravarty, Uday; Singhal, Himanshu; Sanyasi Rao, Bobbili; Chakera, Juzer Ali; Prasad Singh, Manoranjan; Dass Gupta, Parshottam

    2014-11-01

    The inner-shell radiation (K-α) and the ionic line radiation (He-α) from magnesium plasma, generated by the interaction of a 3 TW, 45 fs laser, have been studied simultaneously using an x-ray crystal spectrograph. The effect of the variation of the laser intensity and its offset from the best focus position has been studied. He-α and K-α x-ray yields are found to scale with the laser intensity as IL1.5 and IL0.6 respectively. The K-α x-ray conversion shows a maximum at the best focus and reduces symmetrically on either side of the best focus position, whereas the He-α conversion peaks when the target is placed before the focused laser beam. The angular distribution for the He-α as well as the K-α emissions shows a maximum in the forward direction and the intensity reduces with the increase in angle θ with respect to the target normal as cosα θ. The value of α is 0.7 and 3 for He-α and K-α respectively. The experimentally observed variation of the He-α line conversion for different laser parameters has been explained by considering the change in preformed plasma conditions, and the variation in the K-α emission has been explained by considering hot electron generation and their propagation in the bulk solid target. The plasma conditions prevalent during the emission of the x-ray spectrum were identified by comparing the experimental spectra with the synthetic spectra generated using the spectroscopic analysis code PrismSPECT. The results will be useful in designing laser-produced plasma x-ray line radiation sources of photon energy in the range of 1-2 keV, for its potential use as a probe pulse in x-ray backlighting, or time-resolved x-ray diffraction studies.

  3. Inner-shell capture and ionization in collisions of H/sup +/, He/sup 2 +/, and Li/sup 3 +/ projectiles with neon and carbon

    SciTech Connect

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

    1981-02-01

    Theoretical methods used previously for H/sup +/, He/sup 2 +/, and C/sup 6 +/ collisions with neutral argon atoms have been applied to collisions of H/sup +/, He/sup 2 +/, and Li/sup 3 +/ projectiles with neon, and to collisions of H/sup +/ with carbon targets. The energy range covered by the calculations is 0.4 to 4.0 MeV/amu for the neon target, and 0.2 to 2.0 MeV/amu for carbon. We calculate single-electron amplitudes for target K-shell ionization and target K- and L-shell, to projectile K-shell, charge transfer. These single-electron amplitudes are used, in an independent-particle model that allows for multielectron processes, to compute K-shell vacancy production cross sections sigma/sup IPM//sub V/K, and cross sections sigma/sup IPM//sub C/,VK for producing a charge-transfer state of the projectile in the coincidence with a K-shell vacancy in the target. These cross sections are in reasonable agreement with the recent experiments of Rodbro et al. at Aarhus. In particular, the calculated, as well as the experimental, sigma/sub C/,VK scale with projectile nuclear charge Z/sub p/ less strongly than the Z/sup 5//sub p/ of the Oppenheimer-Brinkman-Kramers (OBK) approximation. For He/sup 2 +/ and Li/sup 3 +/ projectiles at collision energies below where experimental data are available, our calculated multielectron corrections to the single-electron approximation for sigma/sub C/,VK are large.

  4. Contributions to the generalized oscillator strength for the inner-shell C 1s{yields}3s{sigma}{sub g} transition in CO{sub 2} from the vibronic coupling mechanism

    SciTech Connect

    Rocha, Alexandre B.; Bielschowsky, Carlos E.

    2002-11-01

    An approach is proposed to account for the general effect of the nuclei motion in the intensity of electronic transitions caused by fast electron collision with molecular targets, following a similar procedure that has recently been used by our group to determine the optical oscillator strength of symmetry-forbidden transition, and which consists of expanding the (squared) transition moment along the normal coordinates of vibration. It is shown that the profile of total generalized oscillator strength as a function of the squared transferred moment can be significantly changed by the inclusion of terms that depend explicitly on the normal coordinates of vibration. The generalized oscillator strength for the inner-shell C 1s{yields}3s{sigma}{sub g} transition in CO{sub 2} is calculated within this approach and compared with experimental results.

  5. Vacancies in epitaxial graphene

    SciTech Connect

    Davydov, S. Yu.

    2015-08-15

    The coherent-potential method is used to consider the problem of the influence of a finite concentration of randomly arranged vacancies on the density of states of epitaxial graphene. To describe the density of states of the substrate, simple models (the Anderson model, Haldane-Anderson model, and parabolic model) are used. The electronic spectrum of free single-sheet graphene is considered in the low-energy approximation. Charge transfer in the graphene-substrate system is discussed. It is shown that, in all cases, the density of states of epitaxial graphene decreases proportionally to the vacancy concentration. At the same time, the average charge transferred from graphene to the substrate increases.

  6. Formation and Growth of Stacking Fault Tetrahedra in Ni via Vacancy Aggregation Mechanism

    SciTech Connect

    Aidhy, Dilpuneet S.; Lu, Chenyang; Jin, Ke; Bei, Hongbin; Zhang, Yanwen; Wang, Lumin; Weber, William J.

    2015-12-29

    Using molecular dynamics simulations, the formation and growth of stacking fault tetrahedra (SFT) are captured by vacancy cluster diffusion and aggregation mechanisms in Ni. The vacancytetrahedron acts as a nucleation point for SFT formation. Simulations show that perfect SFT can grow to the next size perfect SFT via a vacancy aggregation mechanism. The stopping and range of ions in matter (SRIM) calculations and transmission electron microscopy (TEM) observations reveal that SFT can form farther away from the initial cascade-event locations, indicating the operation of diffusion-based vacancy-aggregation mechanism.

  7. HELIUM EFFECTS ON DISPLACEMENT CASCADE IN TUNGSTEN

    SciTech Connect

    Setyawan, Wahyu; Nandipati, Giridhar; Roche, Kenneth J.; Heinisch, Howard L.; Kurtz, Richard J.; Wirth, Brian D.

    2013-09-30

    Molecular dynamics (MD) simulations were performed to investigate He effects on displacement cascades in W. Helium content, proportion of interstitial and substitutional He and temperature were varied to reveal the various effects. The effect of interstitial He on the number of self-interstitial atoms (SIAs) produced during cascade damage appears to be insignificant. However, interstitial He tends to fill a vacancy (V). Nevertheless, this process is less favorable than SIA-V recombination particularly when excess SIAs are present before a cascade. The efficiency of He filling and SIA-V recombination increases as temperature increases due to increased point defect mobility. Likewise, substitutional He is more susceptible to displacement during a collision cascade than W. This susceptibility increases towards higher temperatures. Consequently, the number of surviving V is governed by the interplay between displaced substitutional He and SIA-V recombination. The temperature dependence of these processes results in a minimum number of V reached at an intermediate temperature.

  8. 24 CFR 983.352 - Vacancy payment.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... keep the payment if the PHA determines that the vacancy is the owner's fault. (b) Vacancy payment at...); (ii) The owner certifies that the vacancy is not the fault of the owner and that the unit was...

  9. 24 CFR 983.352 - Vacancy payment.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... keep the payment if the PHA determines that the vacancy is the owner's fault. (b) Vacancy payment at...); (ii) The owner certifies that the vacancy is not the fault of the owner and that the unit was...

  10. 24 CFR 983.352 - Vacancy payment.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... keep the payment if the PHA determines that the vacancy is the owner's fault. (b) Vacancy payment at...); (ii) The owner certifies that the vacancy is not the fault of the owner and that the unit was...

  11. Pathway studies in the fragmentation of Ge(CH 3) 4 involving Ge(3d,3p,3s) and C(1s) inner-shell photoexcitation in the range 49.5-450 eV

    NASA Astrophysics Data System (ADS)

    Boo, Bong Hyun; Saito, Norio; Suzuki, Isao H.; Koyano, Inosuke

    2002-06-01

    The dissociative multiple photoionization of tetramethylgermane (Ge(CH 3) 4) in the valence, and in the Ge(3d,3p,3s) and C(1s) inner-shell regions has been studied by using time-of-flight mass spectrometry coupled to synchrotron radiation in the range 49.5-450 eV. Total and individual photoion yields have been recorded as a function of the incident photon energy. Several discrete resonances over a structureless giant resonance are observed below the Ge(3p), Ge(3s) and C(1s) threshold regions. The structureless giant resonance corresponding to the Ge(3d) presumably arises from the continuum enhancement caused by the 3d→ɛf transition. Various monocations of H +, H 2+, CH n+ ( n=0-4), C 2H n+ ( n=0-5), GeH n+, GeCH n+, GeC 2H n+, and GeC 3H n+ are detected in the whole energy range. Dissociation processes have also been investigated by photoelectron-photoion and photoion-photoion coincidence methods. The dominant dissociation channel is found to be CH n+-GeCH n+ in the whole energy examined. Specific energy dependence of dissociation processes is observed in the Ge(3p) and Ge(3s) regions. With the help of ab initio HF/6-311++G(2df,p) calculation, we roughly estimated the photoabsorption positions and symmetries for the discrete core hole states.

  12. Counting vacancies and nitrogen-vacancy centers in detonation nanodiamond

    NASA Astrophysics Data System (ADS)

    Chang, Shery L. Y.; Barnard, Amanda S.; Dwyer, Christian; Boothroyd, Chris B.; Hocking, Rosalie K.; Ōsawa, Eiji; Nicholls, Rebecca J.

    2016-05-01

    Detonation nanodiamond particles (DND) contain highly-stable nitrogen-vacancy (N-V) centers, making it important for quantum-optical and biotechnology applications. However, due to the small particle size, the N-V concentrations are believed to be intrinsically very low, spawning efforts to understand the formation of N-V centers and vacancies, and increase their concentration. Here we show that vacancies in DND can be detected and quantified using simulation-aided electron energy loss spectroscopy. Despite the small particle size, we find that vacancies exist at concentrations of about 1 at%. Based on this experimental finding, we use ab initio calculations to predict that about one fifth of vacancies in DND form N-V centers. The ability to directly detect and quantify vacancies in DND, and predict the corresponding N-V formation probability, has a significant impact to those emerging technologies where higher concentrations and better dispersion of N-V centres are critically required.Detonation nanodiamond particles (DND) contain highly-stable nitrogen-vacancy (N-V) centers, making it important for quantum-optical and biotechnology applications. However, due to the small particle size, the N-V concentrations are believed to be intrinsically very low, spawning efforts to understand the formation of N-V centers and vacancies, and increase their concentration. Here we show that vacancies in DND can be detected and quantified using simulation-aided electron energy loss spectroscopy. Despite the small particle size, we find that vacancies exist at concentrations of about 1 at%. Based on this experimental finding, we use ab initio calculations to predict that about one fifth of vacancies in DND form N-V centers. The ability to directly detect and quantify vacancies in DND, and predict the corresponding N-V formation probability, has a significant impact to those emerging technologies where higher concentrations and better dispersion of N-V centres are critically

  13. Counting vacancies and nitrogen-vacancy centers in detonation nanodiamond.

    PubMed

    Chang, Shery L Y; Barnard, Amanda S; Dwyer, Christian; Boothroyd, Chris B; Hocking, Rosalie K; Ōsawa, Eiji; Nicholls, Rebecca J

    2016-05-19

    Detonation nanodiamond particles (DND) contain highly-stable nitrogen-vacancy (N-V) centers, making it important for quantum-optical and biotechnology applications. However, due to the small particle size, the N-V concentrations are believed to be intrinsically very low, spawning efforts to understand the formation of N-V centers and vacancies, and increase their concentration. Here we show that vacancies in DND can be detected and quantified using simulation-aided electron energy loss spectroscopy. Despite the small particle size, we find that vacancies exist at concentrations of about 1 at%. Based on this experimental finding, we use ab initio calculations to predict that about one fifth of vacancies in DND form N-V centers. The ability to directly detect and quantify vacancies in DND, and predict the corresponding N-V formation probability, has a significant impact to those emerging technologies where higher concentrations and better dispersion of N-V centres are critically required. PMID:27147128

  14. Exploration of Vacancies in Solid 4^He

    NASA Astrophysics Data System (ADS)

    Clark, Bryan; Ceperley, David

    2006-03-01

    Experiments by Kim and Chan [1] have renewed interest in the understanding of supersolids and whether mechanisms exist in solid ^4He to allow for supersolid-like effects. Ground state vacancies would lead to bose condensation and superfluidity. Using Path Integral Monte Carlo we examine vacancy formation energies, vacancy-vacancy interactions and the effect of vacancies on supersolid behavior in solid ^4He. [1] E. Kim and M. H. Chan, Science 305, 1941 (2004).

  15. Displacement cascades and defect annealing in tungsten, Part II: Object kinetic Monte Carlo Simulation of Tungsten Cascade Aging

    SciTech Connect

    Nandipati, Giridhar; Setyawan, Wahyu; Heinisch, Howard L.; Roche, Kenneth J.; Kurtz, Richard J.; Wirth, Brian D.

    2015-07-01

    The results of object kinetic Monte Carlo (OKMC) simulations of the annealing of primary cascade damage in bulk tungsten using a comprehensive database of cascades obtained from molecular dynamics (Setyawan et al.) are described as a function of primary knock-on atom (PKA) energy at temperatures of 300, 1025 and 2050 K. An increase in SIA clustering coupled with a decrease in vacancy clustering with increasing temperature, in addition to the disparate mobilities of SIAs versus vacancies, causes an interesting effect of temperature on cascade annealing. The annealing efficiency (the ratio of the number of defects after and before annealing) exhibits an inverse U-shape curve as a function of temperature. The capabilities of the newly developed OKMC code KSOME (kinetic simulations of microstructure evolution) used to carry out these simulations are described.

  16. Displacement cascades and defect annealing in tungsten, Part II: Object kinetic Monte Carlo simulation of tungsten cascade aging

    NASA Astrophysics Data System (ADS)

    Nandipati, Giridhar; Setyawan, Wahyu; Heinisch, Howard L.; Roche, Kenneth J.; Kurtz, Richard J.; Wirth, Brian D.

    2015-07-01

    The results of object kinetic Monte Carlo (OKMC) simulations of the annealing of primary cascade damage in bulk tungsten using a comprehensive database of cascades obtained from molecular dynamics (Setyawan et al.) are described as a function of primary knock-on atom (PKA) energy at temperatures of 300, 1025 and 2050 K. An increase in SIA clustering coupled with a decrease in vacancy clustering with increasing temperature, in addition to the disparate mobilities of SIAs versus vacancies, causes an interesting effect of temperature on cascade annealing. The annealing efficiency (the ratio of the number of defects after and before annealing) exhibits an inverse U-shape curve as a function of temperature. The capabilities of the newly developed OKMC code KSOME (kinetic simulations of microstructure evolution) used to carry out these simulations are described.

  17. MOLECULAR DYNAMICS OF CASCADES OVERLAP IN TUNGSTEN WITH 20-KEV PRIMARY KNOCK-ON ATOMS

    SciTech Connect

    Setyawan, Wahyu; Nandipati, Giridhar; Roche, Kenneth J.; Kurtz, Richard J.; Wirth, Brian D.

    2015-04-16

    Molecular dynamics simulations are performed to investigate the mutual influence of two subsequent cascades in tungsten. The influence is studied using 20-keV primary knock-on atoms, to induce one cascade after another separated by 15 ps, in a lattice temperature of 1025 K (i.e. 0.25 of the melting temperature of the interatomic potential). The center of mass of the vacancies at the peak damage during the cascade is taken as the location of the cascade. The distance between this location to that of the next cascade is taken as the overlap parameter. Empirical fits describing the number of surviving vacancies and interstitial atoms as a function of overlap are presented.

  18. 7 CFR 1160.205 - Vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... National Fluid Milk Processor Promotion Board § 1160.205 Vacancies. To fill any vacancy occasioned by the... a successor from the most recent list of nominations made by individual fluid milk processors...

  19. 7 CFR 1205.327 - Vacancies.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE COTTON RESEARCH AND PROMOTION Cotton Research and Promotion Order Cotton Board § 1205.327 Vacancies. To fill any vacancy occasioned by...

  20. 7 CFR 1205.327 - Vacancies.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE COTTON RESEARCH AND PROMOTION Cotton Research and Promotion Order Cotton Board § 1205.327 Vacancies. To fill any vacancy occasioned by...

  1. 7 CFR 1205.327 - Vacancies.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE COTTON RESEARCH AND PROMOTION Cotton Research and Promotion Order Cotton Board § 1205.327 Vacancies. To fill any vacancy occasioned by...

  2. 7 CFR 981.36 - Vacancy.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE ALMONDS GROWN IN CALIFORNIA Order Regulating Handling Almond Board of California § 981.36 Vacancy. To fill any vacancy occasioned by the death,...

  3. 7 CFR 981.36 - Vacancy.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE ALMONDS GROWN IN CALIFORNIA Order Regulating Handling Almond Board of California § 981.36 Vacancy. To fill any vacancy occasioned by the death,...

  4. 7 CFR 981.36 - Vacancy.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE ALMONDS GROWN IN CALIFORNIA Order Regulating Handling Almond Board of California § 981.36 Vacancy. To fill any vacancy occasioned by the death,...

  5. 7 CFR 981.36 - Vacancy.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE ALMONDS GROWN IN CALIFORNIA Order Regulating Handling Almond Board of California § 981.36 Vacancy. To fill any vacancy occasioned by the death,...

  6. 7 CFR 981.36 - Vacancy.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE ALMONDS GROWN IN CALIFORNIA Order Regulating Handling Almond Board of California § 981.36 Vacancy. To fill any vacancy occasioned by the death,...

  7. 7 CFR 932.33 - Vacancies.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE OLIVES GROWN IN CALIFORNIA Order Regulating Handling Olive Administrative Committee § 932.33 Vacancies. To fill any vacancy occasioned by...

  8. 7 CFR 932.33 - Vacancies.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE OLIVES GROWN IN CALIFORNIA Order Regulating Handling Olive Administrative Committee § 932.33 Vacancies. To fill any vacancy occasioned by...

  9. 7 CFR 932.33 - Vacancies.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE OLIVES GROWN IN CALIFORNIA Order Regulating Handling Olive Administrative Committee § 932.33 Vacancies. To fill any vacancy occasioned by...

  10. 7 CFR 932.33 - Vacancies.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE OLIVES GROWN IN CALIFORNIA Order Regulating Handling Olive Administrative Committee § 932.33 Vacancies. To fill any vacancy occasioned by...

  11. 7 CFR 932.33 - Vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE OLIVES GROWN IN CALIFORNIA Order Regulating Handling Olive Administrative Committee § 932.33 Vacancies. To fill any vacancy occasioned by...

  12. 7 CFR 930.27 - Vacancies.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... MICHIGAN, NEW YORK, PENNSYLVANIA, OREGON, UTAH, WASHINGTON, AND WISCONSIN Order Regulating Handling Administrative Body § 930.27 Vacancies. To fill any vacancy occasioned by the failure of any person appointed...

  13. 7 CFR 982.35 - Vacancy.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE HAZELNUTS GROWN IN OREGON AND WASHINGTON Order Regulating Handling Hazelnut Control Board § 982.35 Vacancy. To fill any vacancy occasioned by...

  14. 7 CFR 982.35 - Vacancy.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE HAZELNUTS GROWN IN OREGON AND WASHINGTON Order Regulating Handling Hazelnut Control Board § 982.35 Vacancy. To fill any vacancy occasioned by...

  15. 7 CFR 982.35 - Vacancy.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE HAZELNUTS GROWN IN OREGON AND WASHINGTON Order Regulating Handling Hazelnut Control Board § 982.35 Vacancy. To fill any vacancy occasioned by...

  16. 7 CFR 982.35 - Vacancy.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE HAZELNUTS GROWN IN OREGON AND WASHINGTON Order Regulating Handling Hazelnut Control Board § 982.35 Vacancy. To fill any vacancy occasioned by...

  17. 7 CFR 982.35 - Vacancy.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE HAZELNUTS GROWN IN OREGON AND WASHINGTON Order Regulating Handling Hazelnut Control Board § 982.35 Vacancy. To fill any vacancy occasioned by...

  18. 7 CFR 1230.35 - Vacancies.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE PORK PROMOTION, RESEARCH, AND CONSUMER INFORMATION Pork Promotion, Research, and Consumer Information Order National Pork Producers Delegate Body § 1230.35 Vacancies. To fill any vacancy occasioned by the death, removal, resignation,...

  19. 7 CFR 1230.35 - Vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE PORK PROMOTION, RESEARCH, AND CONSUMER INFORMATION Pork Promotion, Research, and Consumer Information Order National Pork Producers Delegate Body § 1230.35 Vacancies. To fill any vacancy occasioned by the death, removal, resignation,...

  20. THE EFFECTS OF GRAIN BOUNDARIES ON RADIATION DAMAGE PRODUCTION BY DISPLACEMENT CASCADES IN α-Fe

    SciTech Connect

    Heinisch, Howard L.; Kurtz, Richard J.; Gao, Fei

    2011-04-17

    It is well known that grain boundaries in metals can be sinks for migrating defects such as mobile interstitial atoms, but less is known about the effects of grain boundaries on defect production and defect-grain boundary interactions due to displacement cascades in the vicinity of grain boundaries. Molecular dynamics simulations were performed for displacement cascades in the vicinity of both a symmetric {Sigma}3<110>{l_brace}112{r_brace} and a symmetric {Sigma}11<110>{l_brace}323{r_brace} grain boundary (GB) in {alpha}-Fe to investigate cascade-GB interactions and defect creation near GBs. Both self-interstitial atoms and vacancies are created within the {Sigma}11 GB as well as within the {Sigma}3 GB, although fewer defects are trapped in the {Sigma}3 GB than in the {Sigma}11. See Figures 1-3 and typical cascades in Figure 4. The relative numbers of surviving vacancies and interstitials per cascade residing within the GB vary as a function of the distance of the primary knock-on atom from the GB, with more interstitials than vacancies arriving at the GB from distant cascades. For both {Sigma}3 and {Sigma}11 GBs the total number of surviving defects per cascade increases somewhat with decreasing distance of the cascade from the GB, indicating that having some fraction of the defects trapped in the GB promotes the initial survival of more cascade defects overall relative to cascades in the perfect crystal. Molecular statics simulations of defect formation energies within the GBs (Figure 5) confirm that both vacancies and self-interstitials have lower defect formation energies in both the {Sigma}3 and {Sigma}11 GBs relative to their formation energies in the perfect crystal.

  1. 7 CFR 7.13 - Vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 1 2010-01-01 2010-01-01 false Vacancies. 7.13 Section 7.13 Agriculture Office of the Secretary of Agriculture SELECTION AND FUNCTIONS OF AGRICULTURAL STABILIZATION AND CONSERVATION STATE, COUNTY AND COMMUNITY COMMITTEES § 7.13 Vacancies. (a) In case of a vacancy in the office of chairperson of county or community committee,...

  2. Atomistic Simulation of Displacement Cascades in Zircon

    SciTech Connect

    Devanathan, Ram; Weber, William J.; Corrales, Louis R.; BP McGrail and GA Cragnolino

    2002-05-06

    Low energy displacement cascades in zircon (ZrSiO4) initiated by a Zr primary knock-on atom have been investigated by molecular dynamics simulations using a Coulombic model for long-range interactions, Buckingham potential for short-range interactions and Ziegler-Biersack potentials for close pair interactions. Displacements were found to occur mainly in the O sublattice, and O replacements by a ring mechanism were predominant. Clusters containing Si interstitials bridged by O interstitials, vacancy clusters and anti-site defects were found to occur. This Si-O-Si bridging is considerable in quenched liquid ZrSiO4.

  3. Cascaded Mach–Zehnder interferometer tunable filters

    NASA Astrophysics Data System (ADS)

    Ovvyan, A. P.; Gruhler, N.; Ferrari, S.; Pernice, W. H. P.

    2016-06-01

    By cascading compact and low-loss Mach–Zehnder interferometers (MZIs) embedded within nanophotonic circuits we realize thermo-optically tunable optical filters for the visible wavelength range. Through phase tuning in either arm of the MZI, the filter response with maximum extinction can be shifted beyond one free-spectral range with low electrical power consumption. The working wavelength of our device is aligned with the emission wavelength of the silicon vacancy color center in diamond around 740 nm where we realize a filter depth beyond 36.5 dB. Our approach allows for efficient isolation of the emitted signal intensity in future hybrid nanodiamond-nanophotonic circuits.

  4. Interaction of displacement cascade with helium bubbles in alpha-iron: Computer simulation

    SciTech Connect

    Pu, Jin; Yang, Li; Gao, Fei; Heinisch, Howard L.; Kurtz, Richard J.; Zu, Xiaotao T.

    2008-09-01

    Molecular dynamics (MD) method has been performed to study the interaction of displacement cascade with He bubbles with two sets of potentials. The results show that the stability of He bubbles depends much on the initial He-vacancy (He/V) ratio and the recoil energy. For an initial He/V ratio of 3, the cascade leads to the increase in the number of vacancies in the He bubble and the decrease in the He/V ratio. For an initial He/V ratio of 0.5, the interaction of a cascade with the He/V bubble results in the decrease in the number of vacancies and the increase in the He/V ratio. For an initial He/V ratio of 1, the stability of the bubbles slightly depends on the primary knock-on atom (PKA) energy. Furthermore, a large number of self-interstitial atom clusters are formed after cascade collision for the He/V ratio of 3, while large vacancy clusters are observed for the He/V ratio of 0.5. However, some differences of defect production and clustering between the two sets of potentials are observed, which may be associated the formation energies of He-V clusters, the binding energies of vacancies and He atoms to the clusters and the probability of subcascade formation.

  5. Anomaly in Dependence of Radiation-induced Vacancy Accumulation on Grain Size

    SciTech Connect

    Yang, Yi; Huang, Hanchen; Zinkle, Steven J

    2010-01-01

    According to conventional steady-state rate theory predictions of displacement damage evolution in irradiated materials, the accumulation of vacancies decreases as grain size decreases. Using atomistic simulations, the authors report a transient anomaly in the dependence of radiation produced vacancy accumulation on grain size. Contrary to the conventional wisdom, the accumulation of vacancies can be higher in smaller grains than in larger grains during a transient stage. The anomaly is a result of competition between two atomic-level processes: grain boundary absorption and bulk recombination of point defects, each of which has characteristic length and time scales. A simple metal copper is used as the prototype of face-centered cubic material and electron radiation is the source of non-cascade defect production, both choices aiming at clarity for identifying physical mechanisms.

  6. Hydrogen in anion vacancies of semiconductors

    SciTech Connect

    Du, Mao-Hua; Singh, David J

    2009-01-01

    Density functional calculations show that, depending on the anion size, hydrogen in anion vacancies of various II-VI semiconductors can be either two-fold or four-fold coordinated, and has either amphoteric or shallow donor character. In general, the multi-coordination of hydrogen in an anion vacancy is the indication of an anionic H, H { ion, in the relatively ionic environment. In more covalent semiconductors, H would form a single cation-H bond in the anion vacancy.

  7. 7 CFR 1260.163 - Vacancies.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE BEEF PROMOTION AND RESEARCH Beef Promotion and Research Order Beef Promotion Operating Committee § 1260.163 Vacancies. To fill any...

  8. 7 CFR 1260.163 - Vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE BEEF PROMOTION AND RESEARCH Beef Promotion and Research Order Beef Promotion Operating Committee § 1260.163 Vacancies. To fill any...

  9. 7 CFR 1220.206 - Vacancies.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE SOYBEAN PROMOTION, RESEARCH, AND CONSUMER INFORMATION Soybean Promotion and Research Order United Soybean Board § 1220.206 Vacancies....

  10. 7 CFR 1220.206 - Vacancies.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE SOYBEAN PROMOTION, RESEARCH, AND CONSUMER INFORMATION Soybean Promotion and Research Order United Soybean Board § 1220.206 Vacancies....

  11. 7 CFR 1220.206 - Vacancies.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE SOYBEAN PROMOTION, RESEARCH, AND CONSUMER INFORMATION Soybean Promotion and Research Order United Soybean Board § 1220.206 Vacancies....

  12. 7 CFR 1220.206 - Vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE SOYBEAN PROMOTION, RESEARCH, AND CONSUMER INFORMATION Soybean Promotion and Research Order United Soybean Board § 1220.206 Vacancies....

  13. 7 CFR 1220.206 - Vacancies.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE SOYBEAN PROMOTION, RESEARCH, AND CONSUMER INFORMATION Soybean Promotion and Research Order United Soybean Board § 1220.206 Vacancies....

  14. 7 CFR 1207.324 - Vacancies.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE POTATO RESEARCH AND PROMOTION PLAN Potato Research and Promotion Plan National Potato Promotion Board § 1207.324 Vacancies. To fill...

  15. 7 CFR 1207.324 - Vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE POTATO RESEARCH AND PROMOTION PLAN Potato Research and Promotion Plan National Potato Promotion Board § 1207.324 Vacancies. To fill...

  16. 7 CFR 1207.324 - Vacancies.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE POTATO RESEARCH AND PROMOTION PLAN Potato Research and Promotion Plan National Potato Promotion Board § 1207.324 Vacancies. To fill...

  17. 7 CFR 1207.324 - Vacancies.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE POTATO RESEARCH AND PROMOTION PLAN Potato Research and Promotion Plan National Potato Promotion Board § 1207.324 Vacancies. To fill...

  18. 7 CFR 1207.324 - Vacancies.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE POTATO RESEARCH AND PROMOTION PLAN Potato Research and Promotion Plan National Potato Promotion Board § 1207.324 Vacancies. To fill...

  19. Computer Simulation of Cascade Damage in α-Iron with Carbon in Solution

    SciTech Connect

    Andrew, Calder F; Bacon, David J; Barashev, Aleksandr; Osetskiy, Yury N

    2008-01-01

    Molecular dynamics simulation method is used to investigate defect production by displacement cascades in iron with carbon (C) in solution. This is the first study of cascade damage in a metal containing interstitial solute. Iron is of particular interest because of the use of ferritic steels in plant for nuclear power generation. Cascades are simulated with energy in the range 5 to 20keV in iron at either 100 or 600K containing carbon with concentration in the range 0 to 1at%. C in solution has no discernible effect on the number of defects produced in cascades under any of the conditions simulated, nor on the clustered fraction of either self-interstitial atoms (SIAs) or vacancies. However, significant fractions of single SIAs and vacancies are trapped by C in the cascade process, irrespective of cascade energy. The fraction is independent of temperature for vacancies, but increases strongly with temperature for SIAs: this is a consequence of the higher mobility of the SIA.

  20. MD description of damage production in displacement cascades in copper and α-iron.

    SciTech Connect

    Bacon, David J; Osetskiy, Yury N; Stoller, Roger E; Voskoboinikov, Roman E

    2003-01-01

    Molecular dynamics computer simulation was applied for an extensive study of primary damage creation in displacement cascades in copper and {alpha}-iron. Primary knock-on atom energy, E{sub p}, of up to 25 keV in copper and 100 keV in iron was considered for irradiation temperatures in the range 100-900 K. Special attention was paid to comprehensive statistical treatment of the number and type of defects created in cascades by conducting multiple simulations for each value of energy and temperature. The total number of point defects per cascade is significantly lower than that predicted by the NRT model and rather similar in the two metals. The fraction of self-interstitial atoms (SIAs) and vacancies that agglomerate in clusters in the cascade process was analysed in detail. The clustered fraction of SIAs increases with temperature increase and is larger in copper than iron. SIA clusters have a variety of forms in both metals and, although most are glissile clusters of parallel crowdions, a significant fraction are sessile. The latter include Frank dislocation loops in copper. Tightly packed arrangements of vacancies do not form in iron, and so the fraction of clustered vacancies depends strongly on the range within which point defects are defined to be near-neighbours. Arrangements of vacancies in first-neighbour sites are common in copper. Most are irregular stacking fault tetrahedra (SFTs). In 53 simulations of cascades with E{sub p} = 25 keV at 100 K, the largest cluster formed contained 89 vacancies. The size spectrum of SFT-like clusters is similar to that found experimentally in neutron-irradiated copper, suggesting that the SFTs observed in experiment are formed directly in the cascade process.

  1. 7 CFR 993.32 - Vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Order Regulating Handling Prune Marketing Committee § 993.32 Vacancies. In the event of any committee vacancy occasioned by the removal, resignation, disqualification, or death of any member, or in the event... producer member position to represent independent producers may, at the discretion of the committee,...

  2. 38 CFR 1.896 - Publicizing vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 1 2010-07-01 2010-07-01 false Publicizing vacancies. 1.896 Section 1.896 Pensions, Bonuses, and Veterans' Relief DEPARTMENT OF VETERANS AFFAIRS GENERAL PROVISIONS Part-Time Career Employment Program § 1.896 Publicizing vacancies. When applicants from...

  3. 38 CFR 1.896 - Publicizing vacancies.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 1 2011-07-01 2011-07-01 false Publicizing vacancies. 1.896 Section 1.896 Pensions, Bonuses, and Veterans' Relief DEPARTMENT OF VETERANS AFFAIRS GENERAL PROVISIONS Part-Time Career Employment Program § 1.896 Publicizing vacancies. When applicants from...

  4. 22 CFR 506.6 - Publicizing vacancies.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 22 Foreign Relations 2 2013-04-01 2009-04-01 true Publicizing vacancies. 506.6 Section 506.6 Foreign Relations BROADCASTING BOARD OF GOVERNORS PART-TIME CAREER EMPLOYMENT PROGRAM § 506.6 Publicizing... Employment Offices. (c) Broadcasting Board of Governors Vacancy Announcements. (d) College and...

  5. 22 CFR 506.6 - Publicizing vacancies.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 22 Foreign Relations 2 2011-04-01 2009-04-01 true Publicizing vacancies. 506.6 Section 506.6 Foreign Relations BROADCASTING BOARD OF GOVERNORS PART-TIME CAREER EMPLOYMENT PROGRAM § 506.6 Publicizing... Employment Offices. (c) Broadcasting Board of Governors Vacancy Announcements. (d) College and...

  6. 22 CFR 506.6 - Publicizing vacancies.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 22 Foreign Relations 2 2014-04-01 2014-04-01 false Publicizing vacancies. 506.6 Section 506.6 Foreign Relations BROADCASTING BOARD OF GOVERNORS PART-TIME CAREER EMPLOYMENT PROGRAM § 506.6 Publicizing... Employment Offices. (c) Broadcasting Board of Governors Vacancy Announcements. (d) College and...

  7. 22 CFR 506.6 - Publicizing vacancies.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 22 Foreign Relations 2 2012-04-01 2009-04-01 true Publicizing vacancies. 506.6 Section 506.6 Foreign Relations BROADCASTING BOARD OF GOVERNORS PART-TIME CAREER EMPLOYMENT PROGRAM § 506.6 Publicizing... Employment Offices. (c) Broadcasting Board of Governors Vacancy Announcements. (d) College and...

  8. 22 CFR 506.6 - Publicizing vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 22 Foreign Relations 2 2010-04-01 2010-04-01 true Publicizing vacancies. 506.6 Section 506.6 Foreign Relations BROADCASTING BOARD OF GOVERNORS PART-TIME CAREER EMPLOYMENT PROGRAM § 506.6 Publicizing... Employment Offices. (c) Broadcasting Board of Governors Vacancy Announcements. (d) College and...

  9. South Cascade Glacier bibliography

    SciTech Connect

    Fountain, A.G.; Fulk, M.A.

    1984-01-01

    South Cascade Glacier, in Washington State, resides in a well-defined basin with mainly unglacierized divides making it ideal for most glaciological and hydrological studies. This bibliography is divided into three cateogories: (1) studies done about South Cascade Glacier specifically; (2) studies that use data from South Cascade Glacier but do not focus on or give insight to the glacier itself; and (3) instrumentation studies and non-glacier projects including snow studies done in the basin. (ACR)

  10. Vacancies and antisite defects in ordered alloys

    SciTech Connect

    Johnson, R.A.; Brown, J.R. )

    1992-12-01

    Equations for the concentrations of vacancies and antisite defects in ordered alloys in thermodynamic equilibrium at and near stoichiometry have been derived as functions of defect energies and a Lagrangian parameter. While the resulting equations cannot be solved analytically and in general require iterative calculations, an approximation is given that permits simple numerical evaluation with just a minor loss of accuracy. Using defect energies obtained from an embedded-atom method calculation for Cu[sub 3]Au, it is found that the adjustment for off-stoichiometric compositions is accounted for primarily by the creation of antisite defects rather than vacancies, and the vacancy concentration on Au sites is orders of magnitude less than that on Cu sites. There is a significant increase in the Au vacancy concentration but a slight decrease in the net vacancy content with increasing Cu fraction.

  11. Thermally cascaded thermoelectric generator

    NASA Technical Reports Server (NTRS)

    Flaherty, R.

    1970-01-01

    High efficiency thermoelectric generator utilizes a high-temperature thermoelectric material in thermal series with a low-temperature material. A thermally cascaded generator increases system efficiency.

  12. Temperature Effects on He bubbles production due to cascades in alpha-iron

    SciTech Connect

    Yang, Li; Zu, Xiaotao; Xiao, H Y.; Gao, Fei; Liu, K Z.; Heinisch, Howard L.; Kurtz, Richard J.; Yang, S Z.

    2006-07-15

    The effects of irradiation temperature on the formation of He?vacancy clusters by displacement cascades in *-Fe are investigated by molecular dynamics (MD) methods. The irradiation temperatures of 100 and 600K are considered for primary knock-on atom (PKA) energy, Ep, from 500 eV to 20 keV. The concentration of He in Fe varies from 1 to 5 at.%. We find that the number of Frenkel pairs (NF) at 600K is slightly lower than that at 100K for the same He concentration and Ep, but the number of He?vacancy clusters increases with increasing temperature for the same He concentration and energy recoils. However, the mean size of He?vacancy clusters is independent on temperature. The mechanisms of He bubble nucleation in displacement cascades at different temperatures are discussed in detail.

  13. Effects of in-cascade defect clustering on near-term defect evolution

    SciTech Connect

    Heinisch, H.L.

    1997-08-01

    The effects of in-cascade defect clustering on the nature of the subsequent defect population are being studied using stochastic annealing simulations applied to cascades generated in molecular dynamics (MD) simulations. The results of the simulations illustrates the strong influence of the defect configuration existing in the primary damage state on subsequent defect evolution. The large differences in mobility and stability of vacancy and interstitial defects and the rapid one-dimensional diffusion of small, glissile interstitial loops produced directly in cascades have been shown to be significant factors affecting the evolution of the defect distribution. In recent work, the effects of initial cluster sizes appear to be extremely important.

  14. Cascaded automatic target recognition (Cascaded ATR)

    NASA Astrophysics Data System (ADS)

    Walls, Bradley

    2010-04-01

    The global war on terror has plunged US and coalition forces into a battle space requiring the continuous adaptation of tactics and technologies to cope with an elusive enemy. As a result, technologies that enhance the intelligence, surveillance, and reconnaissance (ISR) mission making the warfighter more effective are experiencing increased interest. In this paper we show how a new generation of smart cameras built around foveated sensing makes possible a powerful ISR technique termed Cascaded ATR. Foveated sensing is an innovative optical concept in which a single aperture captures two distinct fields of view. In Cascaded ATR, foveated sensing is used to provide a coarse resolution, persistent surveillance, wide field of view (WFOV) detector to accomplish detection level perception. At the same time, within the foveated sensor, these detection locations are passed as a cue to a steerable, high fidelity, narrow field of view (NFOV) detector to perform recognition level perception. Two new ISR mission scenarios, utilizing Cascaded ATR, are proposed.

  15. Theory of cascade refrigeration

    NASA Astrophysics Data System (ADS)

    Quack, Hans H.

    2012-06-01

    The maximum difference between the warm and cold temperature of a refrigeration cycle is limited by properties of the refrigerant and/or losses associated with the transport of the refrigerant. For larger temperature differences, one has to arrange several refrigeration cycles "above" each other, each cycle spanning a certain temperature difference. This approach is called cascade refrigeration and has played an important role in the history of cryogenics. For a theory of cascade refrigeration it is helpful to define a general one-stage non-reversible refrigeration step and to visualize it within the temperature-entropy diagram. Then one can combine several one-stage cycles to a cascade. There exist two types of cascades: "Full" cascades, where all entropy gains of a lower stage are transferred to the next higher temperature stage, and "partial" cascades, where each single cycle goes up to ambient temperature, where a part of the entropy gain is removed, and only the rest of the entropy gain is transferred to the next higher temperature stage. In cryogenic refrigeration "partial" cascades are generally more efficient than "full" cascades.

  16. Defect clusters formed from large collision cascades in fcc metals irradiated with spallation neutrons

    NASA Astrophysics Data System (ADS)

    Satoh, Y.; Matsuda, Y.; Yoshiie, T.; Kawai, M.; Matsumura, H.; Iwase, H.; Abe, H.; Kim, S. W.; Matsunaga, T.

    2013-11-01

    Fcc pure metals were irradiated with spallation neutrons (energies up to 500 MeV) at room temperature to a neutron fluence of 1 × 1018 n m-2 at KENS, High Energy Accelerator Research Organization (KEK). Defect clusters induced by large collision cascades were examined using transmission electron microscopy (TEM). In Au, large groups of defects included more than 10 clusters, and the damage zone extended over 50 nm, which was larger than that induced by fusion neutron irradiation (<20 nm). Although small stacking fault tetrahedra (SFT) are formed in subcascades by fission and fusion neutron irradiation, dislocation loops were also observed in the present experiments. Large dislocation loops (>10 nm) were identified as vacancy type by the conventional inside-outside contrast method. Because of the low neutron fluence, spatial overlapping of collision cascades was ignored. Large vacancy loops are formed through cooperative reactions among subcascades in a single collision cascade with large recoil energy.

  17. Understanding long-time vacancy aggregation in iron: A kinetic activation-relaxation technique study

    NASA Astrophysics Data System (ADS)

    Brommer, Peter; Béland, Laurent Karim; Joly, Jean-François; Mousseau, Normand

    2014-10-01

    Vacancy diffusion and clustering processes in body-centered-cubic (bcc) Fe are studied using the kinetic activation-relaxation technique (k-ART), an off-lattice kinetic Monte Carlo method with on-the-fly catalog building capabilities. For monovacancies and divacancies, k-ART recovers previously published results while clustering in a 50-vacancy simulation box agrees with experimental estimates. Applying k-ART to the study of clustering pathways for systems containing from one to six vacancies, we find a rich set of diffusion mechanisms. In particular, we show that the path followed to reach a hexavacancy cluster influences greatly the associated mean-square displacement. Aggregation in a 50-vacancy box also shows a notable dispersion in relaxation time associated with effective barriers varying from 0.84 to 1.1 eV depending on the exact pathway selected. We isolate the effects of long-range elastic interactions between defects by comparing to simulations where those effects are deliberately suppressed. This allows us to demonstrate that in bcc Fe, suppressing long-range interactions mainly influences kinetics in the first 0.3 ms, slowing down quick energy release cascades seen more frequently in full simulations, whereas long-term behavior and final state are not significantly affected.

  18. Structural relaxation of vacancies in amorphous silicon

    SciTech Connect

    Kim, E.; Lee, Y.H.; Chen, C.; Pang, T.

    1997-07-01

    The authors have studied the structural relaxation of vacancies in amorphous silicon (a-Si) using a tight-binding molecular-dynamics method. The most significant difference between vacancies in a-Si and those in crystalline silicon (c-Si) is that the deep gap states do not show up in a-Si. This difference is explained through the unusual behavior of the structural relaxation near the vacancies in a-Si, which enhances the sp{sup 2} + p bonding near the band edges. They have also observed that the vacancies do not migrate below 450 K although some of them can still be annihilated, particularly at high defect density due to large structural relaxation.

  19. 7 CFR 1260.146 - Vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE BEEF PROMOTION AND RESEARCH Beef Promotion and Research Order Cattlemen's Beef Promotion and Research Board § 1260.146 Vacancies. To fill...

  20. 7 CFR 1260.146 - Vacancies.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE BEEF PROMOTION AND RESEARCH Beef Promotion and Research Order Cattlemen's Beef Promotion and Research Board § 1260.146 Vacancies. To fill...

  1. 7 CFR 989.34 - Vacancies.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE RAISINS PRODUCED FROM GRAPES GROWN IN CALIFORNIA Order Regulating Handling Raisin Administrative Committee § 989.34 Vacancies. To fill any...

  2. 7 CFR 989.34 - Vacancies.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE RAISINS PRODUCED FROM GRAPES GROWN IN CALIFORNIA Order Regulating Handling Raisin Administrative Committee § 989.34 Vacancies. To fill any...

  3. 7 CFR 989.34 - Vacancies.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE RAISINS PRODUCED FROM GRAPES GROWN IN CALIFORNIA Order Regulating Handling Raisin Administrative Committee § 989.34 Vacancies. To fill any...

  4. 5. VIEW OF UPPER AND LOWER CASCADE BRIDGES AND CASCADE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    5. VIEW OF UPPER AND LOWER CASCADE BRIDGES AND CASCADE CREEK FROM 100 YARDS WEST OF THE ROSTRUM (ROCK FORMATION ON SOUTH SIDE OF MERCED RIVER). HIGHWAY 140 IS AT BOTTOM OF FRAME. HIGHWAY 120, THE BIG OAK FLAT ROAD CROSSES FRAME JUST ABOVE CENTER. - Cascade Creek Bridge, Spanning Cascade Creek on New Big Oak Flat Road, Yosemite Village, Mariposa County, CA

  5. Highly Itinerant Atomic Vacancies in Phosphorene.

    PubMed

    Cai, Yongqing; Ke, Qingqing; Zhang, Gang; Yakobson, Boris I; Zhang, Yong-Wei

    2016-08-17

    Using detailed first-principles calculations, we investigate the hopping rate of vacancies in phosphorene, an emerging elemental 2D material besides graphene. Our work predicts that a direct observation of these monovacancies (MVs), showing a highly mobile and anisotropic motion, is possible only at low temperatures around 70 K or below where the thermal activity is greatly suppressed. At room temperature, the motion of a MV is 16 orders faster than that in graphene, because of the low diffusion barrier of 0.3 eV. Built-in strain associated with the vacancies extends far along the zigzag direction while attenuating rapidly along the armchair direction. We reveal new features of the motion of divacancies (DVs) in phosphorene via multiple dissociation-recombination processes of vacancies owing to a small energy cost of ∼1.05 eV for the splitting of a DV into two MVs. Furthermore, we find that uniaxial tensile strain along the zigzag direction can promote the motion of MVs, while the tensile strain along the armchair direction has the opposite effect. These itinerant features of vacancies, rooted in the unique puckering structure facilitating bond reorganization, enable phosphorene to be a bright new opportunity to broaden the knowledge of the evolution of vacancies, and a proper control of the exceedingly active and anisotropic movement of the vacancies should be critical for applications based on phosphorene. PMID:27448591

  6. Unsteady Euler cascade analysis

    NASA Technical Reports Server (NTRS)

    Liu, Jong-Shang; Sockol, Peter M.

    1989-01-01

    The results of an investigation of the rotor-stator interaction phenomena in turbomachines are presented. Numerical study was carried out by solving the unsteady Euler equations in the blade-to-blade direction for a variety of cascade geometries. The problem of uneven rotor and stator blades is addressed by adopting the tilted time domain technique. Computed solutions are presented and discussed for a NACA 0012 type cascade and the first stage fuel turbopump of the Space Shuttle Main Engine (SSME).

  7. Binary collision Monte Carlo simulations of cascades in polyatomic ceramics*1

    NASA Astrophysics Data System (ADS)

    Ghoniem, N. M.; Chou, S. P.

    1988-07-01

    The understanding of radiation damage phenomena in polyatomic ceramic materials (PCMs) is still at an early stage as compared to that in metallic structural alloys. The binary collision approximation (BCA) is used in a Monte Carlo (MC) study of high-energy collision-cascade creation in SPINEL (MgAl 2O 4). The study focuses on two aspects of cascade generation: cascade morphology and cascade stoichiometry. In the high-energy regime, typical of fusion neutrons, cascades show a tree-like morphology. To a large degree, instantaneous recombination occurs in the "stem" part of the cascade because of the closer separation of vacancy-interstitial pairs. Following this recombination phase, fusion neutron cascades tend to result in Frenkel pairs distributed on the "branches" of the tree in a zone extending over 100 to 200 nm. The stoichiometry of displacements within the cascade is found to be substantially different from bulk stoichiometry and is dependent upon the energy and type of primary knock-on atom (PKA). Limitations of the BCA to model the low energy characteristics of the cascade are discussed in the paper.

  8. The nitrogen cascade

    SciTech Connect

    Galloway J.N.; Aber J.D.; Erisman J.W.; Seitzinger S.P.; Howarth R.W.; Cowling E.B.; Cosby B.J.

    2003-04-01

    Human production of food and energy is the dominant continental process that breaks the triple bond in molecular nitrogen (N{sub 2}) and creates reactive nitrogen (Nr) species. Circulation of anthropogenic Nr in Earth's atmosphere, hydrosphere, and biosphere has a wide variety of consequences, which are magnified with time as Nr moves along its biogeochemical pathway. The same atom of Nr can cause multiple effects in the atmosphere, in terrestrial ecosystems, in freshwater and marine systems, and on human health. We call this sequence of effects the nitrogen cascade. As the cascade progresses, the origin of Nr becomes unimportant. Reactive nitrogen does not cascade at the same rate through all environmental systems; some systems have the ability to accumulate Nr, which leads to lag times in the continuation of the cascade. These lags slow the cascade and result in Nr accumulation in certain reservoirs, which in turn can enhance the effects of Nr on that environment. The only way to eliminate Nr accumulation and stop the cascade is to convert Nr back to nonreactive N{sub 2}.

  9. Correlated Formation and Stability of SIA Loops and Stacking Fault Tetrahedra in High Energy Displacement Cascades in Copper,

    SciTech Connect

    Voskoboinikov, Roman E; Osetskiy, Yury N; Bacon, David J

    2005-01-01

    Atomistic modeling was conducted for an investigation of primary damage creation, self-interstitial and vacancy clusters formation, and their stability in high energy displacement cascades in copper. The simulations were carried out for a wide range of temperatures (100 K {le} T {le} 900 K) and primary knock-on atom (PKA) energies 5 keV {le} Epka {le} 25 keV. This study of over 400 cascades is the largest yet reported for this metal. At least 20 cascades for each (Epka, T) pair were simulated in order to ensure statistical reliability of the results. The number of surviving point defects for each cascade and the mean value for cascades at the same temperature and PKA energy were found. The corresponding fraction of self-interstitial atoms (SIA) in dislocation loops and vacancies in stacking fault tetrahedron (SFT)-like clusters was calculated. Strong spatial and size correlation of SFTs and SIA clusters at low temperatures were established. In the context of high dose irradiation and the spatial overlap of displacement cascades, the stability of SFTs and dislocation loops inside an overlapping cascade region was investigated. It was observed that an SFT destroyed in the collision phase by a cascade is always recreated. On being completely enveloped by the region of displaced atoms, both SFT and SIA dislocation loops are destroyed with corresponding decrease of the number of residual point defects, whereas partial overlapping leads to increase in size of both types of cluster.

  10. Structure and Mobility of Defects Formed from Collision Cascades in MgO

    NASA Astrophysics Data System (ADS)

    Uberuaga, B. P.; Smith, R.; Cleave, A. R.; Montalenti, F.; Henkelman, G.; Grimes, R. W.; Voter, A. F.; Sickafus, K. E.

    2004-03-01

    We study radiation-damage events in MgO on experimental time scales by augmenting molecular dynamics cascade simulations with temperature accelerated dynamics, molecular statics, and density functional theory. At 400eV, vacancies and mono- and di-interstitials form, but often annihilate within milliseconds. At 2 and 5keV, larger clusters can form and persist. While vacancies are immobile, interstitials aggregate into clusters (In) with surprising properties; e.g., an I4 is immobile, but an im­pinging I2 can create a metastable I6 that diffuses on the nanosecond time scale but is stable for years.

  11. Atomic structure of titania nanosheet with vacancies

    PubMed Central

    Ohwada, Megumi; Kimoto, Koji; Mizoguchi, Teruyasu; Ebina, Yasuo; Sasaki, Takayoshi

    2013-01-01

    Titania nanosheets are two-dimensional single crystallites of titanium oxide with a thickness of one titanium or two oxygen atoms, and they show attractive material properties, such as photocatalytic reactions. Since a titania (Ti0.87O2) nanosheet is synthesized by the delamination of a parent layered K0.8Ti1.73Li0.27O4 crystal using a soft chemical procedure, substantial Ti vacancies are expected to be included and affect the material properties. The atomic arrangement of a titania nanosheet with vacancies has not been revealed owing to the difficulties of direct observation. Here, we have directly visualized the atomic arrangement and Ti vacancies of a titania nanosheet using advanced lower-voltage transmission electron microscopy (TEM). Analyses of the results of first-principles calculations and TEM image simulations for various Ti vacancy structure models indicate that two particular oxygen atoms around each Ti vacancy are desorbed, suggesting the sites where atomic reduction first occurs. PMID:24077611

  12. Displacement cascades and defect annealing in tungsten, Part III: The sensitivity of cascade annealing in tungsten to the values of kinetic parameters

    SciTech Connect

    Nandipati, Giridhar; Setyawan, Wahyu; Heinisch, Howard L.; Roche, Kenneth J.; Kurtz, Richard J.; Wirth, Brian D.

    2015-07-01

    Object kinetic Monte Carlo (OKMC) simulations have been performed to investigate various aspects of cascade aging in bulk tungsten and to determine the sensitivity of the results to the kinetic parameters. The primary focus is on how the kinetic parameters affect the initial recombination of defects in the first few ns of a simulation. The simulations were carried out using the object kinetic Monte Carlo (OKMC) code KSOME (kinetic simulations of microstructure evolution), using a database of cascades obtained from results of molecular dynamics (MD) simulations at various primary knock-on atom (PKA) energies and directions at temperatures of 300, 1025 and 2050 K. The OKMC model was parameterized using defect migration barriers and binding energies from ab initio calculations. Results indicate that, due to the disparate mobilities of SIA and vacancy clusters in tungsten, annealing is dominated by SIA migration even at temperatures as high as 2050 K. For 100 keV cascades initiated at 300 K recombination is dominated by annihilation of large defect clusters. But for all other PKA energies and temperatures most of the recombination is due to the migration and rotation of small SIA clusters, while all the large SIA clusters escape the cubic simulation cell. The inverse U-shape behavior exhibited by the annealing efficiency as a function of temperature curve, especially for cascades of large PKA energies, is due to asymmetry in SIA and vacancy clustering assisted by the large difference in mobilities of SIAs and vacancies. This annealing behavior is unaffected by the dimensionality of SIA migration persists over a broad range of relative mobilities of SIAs and vacancies.

  13. Tracking Earthquake Cascades

    NASA Astrophysics Data System (ADS)

    Jordan, T. H.

    2011-12-01

    In assessing their risk to society, earthquakes are best characterized as cascades that can propagate from the natural environment into the socio-economic (built) environment. Strong earthquakes rarely occur as isolated events; they usually cluster in foreshock-mainshock-aftershock sequences, seismic swarms, and extended sequences of large earthquakes that propagate along major fault systems. These cascades are regulated by stress-mediated interactions among faults driven by tectonic loading. Within these cascades, each large event can itself cause a chain reaction in which the primary effects of faulting and ground shaking induce secondary effects, including tsunami, landslides, liquefaction, and set off destructive processes within the built environment, such as fires and radiation leakage from nuclear plants. Recent earthquakes have demonstrated how the socio-economic effects of large earthquakes can reverberate for many years. To reduce earthquake risk and improve the resiliency of communities to earthquake damage, society depends on five geotechnologies for tracking earthquake cascades: long-term probabilistic seismic hazard analysis (PSHA), short-term (operational) earthquake forecasting, earthquake early warning, tsunami warning, and the rapid production of post-event information for response and recovery (see figure). In this presentation, I describe how recent advances in earthquake system science are leading to improvements in this geotechnology pipeline. In particular, I will highlight the role of earthquake simulations in predicting strong ground motions and their secondary effects before and during earthquake cascades

  14. Resonant Cascaded Downconversion

    SciTech Connect

    Weedbrook, Christian; Parrett, Ben; Kheruntsyan, Karen; Drummond, Peter; Pooser, Raphael C; Pfister, Olivier

    2012-01-01

    We analyze an optical parametric oscillator (OPO) in which cascaded down-conversion occurs inside a cavity resonant for all modes but the initial pump. Due to the resonant cascade design, the OPO presents two {chi}{sup (2)}-level oscillation thresholds that are therefore much lower than for a {chi}{sup (3)} OPO. This is promising for reaching the regime of an effective third-order nonlinearity well above both thresholds. Such a {chi}{sup (2)} cascaded device also has potential applications in frequency conversion to far-infrared regimes. But, most importantly, it can generate novel multipartite quantum correlations in the output radiation, which represent a step beyond squeezed or entangled light. The output can be highly non-Gaussian and therefore not describable by any semiclassical model. In this paper, we derive quantum stochastic equations in the positive-P representation and undertake an analysis of steady-state and dynamical properties of this system.

  15. Hadron cascades produced by electromagnetic cascades

    SciTech Connect

    Nelson, W.R.; Jenkins, T.M.; Ranft, J.

    1986-12-01

    A method for calculating high energy hadron cascades induced by multi-GeV electron and photon beams is described. Using the EGS4 computer program, high energy photons in the EM shower are allowed to interact hadronically according to the vector meson dominance (VMD) model, facilitated by a Monte Carlo version of the dual multistring fragmentation model which is used in the hadron cascade code FLUKA. The results of this calculation compare very favorably with experimental data on hadron production in photon-proton collisions and on the hadron production by electron beams on targets (i.e., yields in secondary particle beam lines). Electron beam induced hadron star density contours are also presented and are compared with those produced by proton beams. This FLUKA-EGS4 coupling technique could find use in the design of secondary beams, in the determination high energy hadron source terms for shielding purposes, and in the estimation of induced radioactivity in targets, collimators and beam dumps.

  16. Lattice Strain Due to an Atomic Vacancy

    PubMed Central

    Li, Shidong; Sellers, Michael S.; Basaran, Cemal; Schultz, Andrew J.; Kofke, David A.

    2009-01-01

    Volumetric strain can be divided into two parts: strain due to bond distance change and strain due to vacancy sources and sinks. In this paper, efforts are focused on studying the atomic lattice strain due to a vacancy in an FCC metal lattice with molecular dynamics simulation (MDS). The result has been compared with that from a continuum mechanics method. It is shown that using a continuum mechanics approach yields constitutive results similar to the ones obtained based purely on molecular dynamics considerations. PMID:19582230

  17. Collisional Cascades Revisited

    NASA Astrophysics Data System (ADS)

    Schlichting, Hilke; Pan, M.

    2013-01-01

    Collisional cascades are believed to be the primary mechanism operating in circumstellar dusty debris disks, and are thought to be important in the Kuiper and Asteroid belt. Collisional cascades transfer mass via destructive collisions from larger bodies to smaller ones. Their widespread occurrence and potential importance in understanding planet formation and planet-disk interactions have motivated detailed studies of collisional cascades. The standard theoretical treatment of collisional cascades derives a steady-state size distribution assuming a single constant velocity dispersion for all bodies regardless of size. We relax this assumption and solve self-consistently for the bodies' steady-state size and size-dependent velocity distributions. Specifically, we account for viscous stirring, dynamical friction, and collisional damping of the bodies' random velocities in addition to the mass conservation requirement typically applied to find the size distribution in a steady-state cascade. The resulting size distributions are significantly steeper than those derived without velocity evolution. For example, accounting self-consistently for the velocities can change the standard q = 3.5 power-law index of the Dohnanyi differential size spectrum to an index as large as q = 4. Similarly, for bodies held together by their own gravity, the corresponding power-law index range 2.88 < q < 3.14 of Pan & Sari (2005) can steepen to values as large as q = 3.26. These differences in the size distribution power law index are very important when estimating the total disk mass, including larger bodies, by extrapolating from the observed dust masses. Our velocity results allow quantitative predictions of the bodies' scale heights as a function of size. Together with our predictions, observations of the scale heights for different-sized bodies in, for example, extrasolar debris disks may constrain the total mass in large bodies stirring the cascade as well as the colliding bodies

  18. Intra Nucleon Cascade Program

    Energy Science and Technology Software Center (ESTSC)

    1998-08-18

    The package consists of three programs ISABEL, EVA, and PACE-2. ISABEL and PACE-2 are part of the LAHET code. ISABEL is an intra-nucleon cascade program. The output cascades are used as directly as input files to the two evaporation programs EVA and PACE-2. EVA ignores the effect of the angular momentum of the excited nuclei on the deexcitation and also ignores the possibility of gamma emission as long as particle emission is energetically allowed. PACE-2more » takes full account of angular momentum effects including irast levels and gamma emission at all stages of the evaporation chain.« less

  19. Howling about Trophic Cascades

    ERIC Educational Resources Information Center

    Kowalewski, David

    2012-01-01

    Following evolutionary theory and an agriculture model, ecosystem research has stressed bottom-up dynamics, implying that top wild predators are epiphenomenal effects of more basic causes. As such, they are assumed expendable. A more modern co-evolutionary and wilderness approach--trophic cascades--instead suggests that top predators, whose…

  20. 'Cascade Gold' raspberry

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cascade Gold’ is a new gold fruited, floricane fruiting raspberry cultivar (Rubus idaeus L.) jointly released by Washington State University (WSU), Oregon State University (OSU) and the U.S. Department of Agriculture (USDA). It has been evaluated at Puyallup, Wash. in plantings from 1988 to 2008. ...

  1. Cascaded thermoacoustic devices

    DOEpatents

    Swift, Gregory W.; Backhaus, Scott N.; Gardner, David L.

    2003-12-09

    A thermoacoustic device is formed with a resonator system defining at least one region of high specific acoustic impedance in an acoustic wave within the resonator system. A plurality of thermoacoustic units are cascaded together within the region of high specific acoustic impedance, where at least one of the thermoacoustic units is a regenerator unit.

  2. 7 CFR 922.26 - Vacancies.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 8 2014-01-01 2014-01-01 false Vacancies. 922.26 Section 922.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE APRICOTS GROWN IN DESIGNATED...

  3. 7 CFR 922.26 - Vacancies.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 8 2013-01-01 2013-01-01 false Vacancies. 922.26 Section 922.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE APRICOTS GROWN IN DESIGNATED...

  4. 7 CFR 922.26 - Vacancies.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 8 2012-01-01 2012-01-01 false Vacancies. 922.26 Section 922.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE APRICOTS GROWN IN DESIGNATED...

  5. 7 CFR 922.26 - Vacancies.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 8 2011-01-01 2011-01-01 false Vacancies. 922.26 Section 922.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE APRICOTS GROWN IN DESIGNATED...

  6. 7 CFR 922.26 - Vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 8 2010-01-01 2010-01-01 false Vacancies. 922.26 Section 922.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE APRICOTS GROWN IN DESIGNATED...

  7. 7 CFR 925.26 - Vacancies.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 8 2014-01-01 2014-01-01 false Vacancies. 925.26 Section 925.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE GRAPES GROWN IN A DESIGNATED AREA...

  8. 7 CFR 989.34 - Vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 8 2010-01-01 2010-01-01 false Vacancies. 989.34 Section 989.34 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE RAISINS PRODUCED FROM GRAPES GROWN...

  9. 7 CFR 925.26 - Vacancies.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 8 2013-01-01 2013-01-01 false Vacancies. 925.26 Section 925.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE GRAPES GROWN IN A DESIGNATED AREA...

  10. 7 CFR 925.26 - Vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 8 2010-01-01 2010-01-01 false Vacancies. 925.26 Section 925.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE GRAPES GROWN IN A DESIGNATED AREA...

  11. 7 CFR 989.34 - Vacancies.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 8 2014-01-01 2014-01-01 false Vacancies. 989.34 Section 989.34 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE RAISINS PRODUCED FROM GRAPES GROWN...

  12. 7 CFR 925.26 - Vacancies.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 8 2011-01-01 2011-01-01 false Vacancies. 925.26 Section 925.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE GRAPES GROWN IN A DESIGNATED AREA...

  13. 7 CFR 925.26 - Vacancies.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 8 2012-01-01 2012-01-01 false Vacancies. 925.26 Section 925.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE GRAPES GROWN IN A DESIGNATED AREA...

  14. 7 CFR 930.27 - Vacancies.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 8 2012-01-01 2012-01-01 false Vacancies. 930.27 Section 930.27 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE TART CHERRIES GROWN IN THE STATES...

  15. 7 CFR 923.26 - Vacancies.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 8 2012-01-01 2012-01-01 false Vacancies. 923.26 Section 923.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE SWEET CHERRIES GROWN IN...

  16. 7 CFR 915.26 - Vacancies.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 8 2012-01-01 2012-01-01 false Vacancies. 915.26 Section 915.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE AVOCADOS GROWN IN SOUTH FLORIDA...

  17. 7 CFR 915.26 - Vacancies.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 8 2013-01-01 2013-01-01 false Vacancies. 915.26 Section 915.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE AVOCADOS GROWN IN SOUTH FLORIDA...

  18. 7 CFR 915.26 - Vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 8 2010-01-01 2010-01-01 false Vacancies. 915.26 Section 915.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE AVOCADOS GROWN IN SOUTH FLORIDA...

  19. 7 CFR 985.26 - Vacancies.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 8 2012-01-01 2012-01-01 false Vacancies. 985.26 Section 985.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE MARKETING ORDER REGULATING THE HANDLING OF SPEARMINT OIL PRODUCED IN THE FAR...

  20. 7 CFR 985.26 - Vacancies.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 8 2014-01-01 2014-01-01 false Vacancies. 985.26 Section 985.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE MARKETING ORDER REGULATING THE HANDLING OF SPEARMINT OIL PRODUCED IN THE FAR...

  1. 7 CFR 956.26 - Vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 8 2010-01-01 2010-01-01 false Vacancies. 956.26 Section 956.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE SWEET ONIONS GROWN IN THE WALLA...

  2. 7 CFR 955.26 - Vacancies.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 8 2014-01-01 2014-01-01 false Vacancies. 955.26 Section 955.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE VIDALIA ONIONS GROWN IN...

  3. 7 CFR 956.26 - Vacancies.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 8 2014-01-01 2014-01-01 false Vacancies. 956.26 Section 956.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE SWEET ONIONS GROWN IN THE WALLA...

  4. 7 CFR 955.26 - Vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 8 2010-01-01 2010-01-01 false Vacancies. 955.26 Section 955.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE VIDALIA ONIONS GROWN IN...

  5. Dangling bonds and vacancies in germanium

    NASA Astrophysics Data System (ADS)

    Weber, J. R.; Janotti, A.; Van de Walle, C. G.

    2013-01-01

    The quest for metal-oxide-semiconductor field-effect transistors (MOSFETs) with higher carrier mobility has triggered great interest in germanium-based MOSFETs. Still, the performance of germanium-based devices lags significantly behind that of their silicon counterparts, possibly due to the presence of defects such as dangling bonds (DBs) and vacancies. Using screened hybrid functional calculations we investigate the role of DBs and vacancies in germanium. We find that the DB defect in germanium has no levels in the band gap; it acts as a negatively charged acceptor with the (0/-1) transition level below the valence-band maximum (VBM). This explains the absence of electron-spin-resonance observations of DBs in germanium. The vacancy in germanium has a much lower formation energy than the vacancy in silicon and is stable in a number of charge states, depending on the position of the Fermi level. We find the (0/-1) and (-1/-2) transition levels at 0.16 and 0.38 eV above the VBM; the spacing of these levels is explained based on the strength of intraorbital repulsion. We compare these results with calculations for silicon, as well as with available experimental data.

  6. Understanding the Oxygen Vacancy in Tungsten Trioxide

    NASA Astrophysics Data System (ADS)

    Wang, Wennie; Janotti, Anderson; van de Walle, Chris G.

    2015-03-01

    Tungsten trioxide (WO3) has a variety of applications in gas sensors, photocatalysis, and smart windows. As an electrochromic BO3 perovskite, WO3 turns from transparent to blue upon doping. This color change is correlated with a drop in transmittance of near-IR radiation, and is used in smart windows for energy efficiency. In addition to monovalent species doping that modulates optical properties, oxygen deficiencies have been found to have a similar electrochromic effect. The influence of oxygen vacancies on electronic structure and how it corresponds to electrochromic behavior remains a topic of debate. In this work, we examine the oxygen vacancy in monoclinic WO3 and its influence on electronic structure using density functional theory with a hybrid functional. We investigate the relative stability of different charge states and its implications for electrical properties, such as conductivity and electrochromism. We find oxygen vacancies to be shallow donors, and explore similarities and differences with monovalent species doping. Finally, we compare our theoretical findings with experiment to elucidate how vacancies may contribute to electrochromic behavior. This work is supported by DOE and NSF.

  7. 7 CFR 966.30 - Vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 8 2010-01-01 2010-01-01 false Vacancies. 966.30 Section 966.30 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE TOMATOES GROWN IN FLORIDA...

  8. Principal Vacancies and Appointments 2009-10

    ERIC Educational Resources Information Center

    Robertson, Sally

    2011-01-01

    School leadership in New Zealand has gained more attention in recent years. The New Zealand Council for Educational Research (NZCER) began collecting data on all principal advertisements in the "Education Gazette" in late 2007. This brief report analyses principal vacancies advertised in the "Education Gazette" in 2009 and 2010. It also analyses…

  9. 24 CFR 990.150 - Limited vacancies.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 24 Housing and Urban Development 4 2012-04-01 2012-04-01 false Limited vacancies. 990.150 Section 990.150 Housing and Urban Development REGULATIONS RELATING TO HOUSING AND URBAN DEVELOPMENT (CONTINUED) OFFICE OF ASSISTANT SECRETARY FOR PUBLIC AND INDIAN HOUSING, DEPARTMENT OF HOUSING AND URBAN DEVELOPMENT THE PUBLIC HOUSING OPERATING FUND...

  10. 7 CFR 923.26 - Vacancies.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 8 2013-01-01 2013-01-01 false Vacancies. 923.26 Section 923.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE SWEET CHERRIES GROWN IN...

  11. 7 CFR 923.26 - Vacancies.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 8 2014-01-01 2014-01-01 false Vacancies. 923.26 Section 923.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE SWEET CHERRIES GROWN IN...

  12. 7 CFR 930.27 - Vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 8 2010-01-01 2010-01-01 false Vacancies. 930.27 Section 930.27 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE TART CHERRIES GROWN IN THE STATES...

  13. 7 CFR 923.26 - Vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 8 2010-01-01 2010-01-01 false Vacancies. 923.26 Section 923.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE SWEET CHERRIES GROWN IN...

  14. 7 CFR 930.27 - Vacancies.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 8 2014-01-01 2014-01-01 false Vacancies. 930.27 Section 930.27 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE TART CHERRIES GROWN IN THE STATES...

  15. 7 CFR 923.26 - Vacancies.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 8 2011-01-01 2011-01-01 false Vacancies. 923.26 Section 923.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE SWEET CHERRIES GROWN IN...

  16. 7 CFR 985.26 - Vacancies.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 8 2013-01-01 2013-01-01 false Vacancies. 985.26 Section 985.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE MARKETING ORDER REGULATING THE HANDLING OF SPEARMINT OIL PRODUCED IN THE FAR...

  17. Unemployment, Vacancies and Local Labor Markets.

    ERIC Educational Resources Information Center

    Holzer, Harry J.

    This monograph studies unemployment in relation to labor market vacancies throughout the United States, using a new set of data: the Survey of Firms from the Employment Opportunity Pilot Project, a labor market experiment conducted by the Department of Labor at 28 sites in 1979 and 1980. The monograph is organized in five chapters. The first…

  18. 7 CFR 920.26 - Vacancies.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 8 2014-01-01 2014-01-01 false Vacancies. 920.26 Section 920.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE KIWIFRUIT GROWN IN...

  19. 7 CFR 920.26 - Vacancies.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 8 2013-01-01 2013-01-01 false Vacancies. 920.26 Section 920.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE KIWIFRUIT GROWN IN...

  20. 7 CFR 920.26 - Vacancies.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 8 2011-01-01 2011-01-01 false Vacancies. 920.26 Section 920.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE KIWIFRUIT GROWN IN...

  1. 7 CFR 920.26 - Vacancies.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 8 2012-01-01 2012-01-01 false Vacancies. 920.26 Section 920.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE KIWIFRUIT GROWN IN...

  2. 7 CFR 920.26 - Vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 8 2010-01-01 2010-01-01 false Vacancies. 920.26 Section 920.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE KIWIFRUIT GROWN IN...

  3. 7 CFR 929.26 - Vacancies.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 8 2011-01-01 2011-01-01 false Vacancies. 929.26 Section 929.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE CRANBERRIES GROWN IN STATES...

  4. 7 CFR 929.26 - Vacancies.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 8 2012-01-01 2012-01-01 false Vacancies. 929.26 Section 929.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE CRANBERRIES GROWN IN STATES...

  5. 7 CFR 929.26 - Vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 8 2010-01-01 2010-01-01 false Vacancies. 929.26 Section 929.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE CRANBERRIES GROWN IN STATES...

  6. 7 CFR 929.26 - Vacancies.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 8 2014-01-01 2014-01-01 false Vacancies. 929.26 Section 929.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE CRANBERRIES GROWN IN STATES...

  7. 7 CFR 929.26 - Vacancies.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 8 2013-01-01 2013-01-01 false Vacancies. 929.26 Section 929.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE CRANBERRIES GROWN IN STATES...

  8. 7 CFR 1208.43 - Vacancies.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE PROCESSED RASPBERRY PROMOTION, RESEARCH, AND INFORMATION ORDER Processed Raspberry Promotion, Research, and Information Order National Processed Raspberry Council § 1208.43 Vacancies. (a) In the event that any member of the Council ceases...

  9. 7 CFR 1208.43 - Vacancies.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE PROCESSED RASPBERRY PROMOTION, RESEARCH, AND INFORMATION ORDER Processed Raspberry Promotion, Research, and Information Order National Processed Raspberry Council § 1208.43 Vacancies. (a) In the event that any member of the Council ceases...

  10. 45 CFR 1176.7 - Publicizing vacancies.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 45 Public Welfare 3 2014-10-01 2014-10-01 false Publicizing vacancies. 1176.7 Section 1176.7 Public Welfare Regulations Relating to Public Welfare (Continued) NATIONAL FOUNDATION ON THE ARTS AND THE HUMANITIES NATIONAL ENDOWMENT FOR THE HUMANITIES PART-TIME CAREER EMPLOYMENT § 1176.7 Publicizing...

  11. 45 CFR 1176.7 - Publicizing vacancies.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 45 Public Welfare 3 2011-10-01 2011-10-01 false Publicizing vacancies. 1176.7 Section 1176.7 Public Welfare Regulations Relating to Public Welfare (Continued) NATIONAL FOUNDATION ON THE ARTS AND THE HUMANITIES NATIONAL ENDOWMENT FOR THE HUMANITIES PART-TIME CAREER EMPLOYMENT § 1176.7 Publicizing...

  12. 45 CFR 1176.7 - Publicizing vacancies.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 45 Public Welfare 3 2012-10-01 2012-10-01 false Publicizing vacancies. 1176.7 Section 1176.7 Public Welfare Regulations Relating to Public Welfare (Continued) NATIONAL FOUNDATION ON THE ARTS AND THE HUMANITIES NATIONAL ENDOWMENT FOR THE HUMANITIES PART-TIME CAREER EMPLOYMENT § 1176.7 Publicizing...

  13. 45 CFR 1176.7 - Publicizing vacancies.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 45 Public Welfare 3 2010-10-01 2010-10-01 false Publicizing vacancies. 1176.7 Section 1176.7 Public Welfare Regulations Relating to Public Welfare (Continued) NATIONAL FOUNDATION ON THE ARTS AND THE HUMANITIES NATIONAL ENDOWMENT FOR THE HUMANITIES PART-TIME CAREER EMPLOYMENT § 1176.7 Publicizing...

  14. 45 CFR 1176.7 - Publicizing vacancies.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 45 Public Welfare 3 2013-10-01 2013-10-01 false Publicizing vacancies. 1176.7 Section 1176.7 Public Welfare Regulations Relating to Public Welfare (Continued) NATIONAL FOUNDATION ON THE ARTS AND THE HUMANITIES NATIONAL ENDOWMENT FOR THE HUMANITIES PART-TIME CAREER EMPLOYMENT § 1176.7 Publicizing...

  15. 7 CFR 984.41 - Vacancy.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 8 2010-01-01 2010-01-01 false Vacancy. 984.41 Section 984.41 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE WALNUTS GROWN IN CALIFORNIA Order...

  16. 7 CFR 984.41 - Vacancy.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 8 2014-01-01 2014-01-01 false Vacancy. 984.41 Section 984.41 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE WALNUTS GROWN IN CALIFORNIA Order...

  17. 7 CFR 984.41 - Vacancy.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 8 2011-01-01 2011-01-01 false Vacancy. 984.41 Section 984.41 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE WALNUTS GROWN IN CALIFORNIA Order...

  18. 7 CFR 984.41 - Vacancy.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 8 2013-01-01 2013-01-01 false Vacancy. 984.41 Section 984.41 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE WALNUTS GROWN IN CALIFORNIA Order...

  19. 7 CFR 984.41 - Vacancy.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 8 2012-01-01 2012-01-01 false Vacancy. 984.41 Section 984.41 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE WALNUTS GROWN IN CALIFORNIA Order...

  20. 7 CFR 955.26 - Vacancies.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 8 2012-01-01 2012-01-01 false Vacancies. 955.26 Section 955.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE VIDALIA ONIONS GROWN IN...

  1. 7 CFR 956.26 - Vacancies.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 8 2012-01-01 2012-01-01 false Vacancies. 956.26 Section 956.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE SWEET ONIONS GROWN IN THE WALLA...

  2. 7 CFR 955.26 - Vacancies.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 8 2013-01-01 2013-01-01 false Vacancies. 955.26 Section 955.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE VIDALIA ONIONS GROWN IN...

  3. 7 CFR 955.26 - Vacancies.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 8 2011-01-01 2011-01-01 false Vacancies. 955.26 Section 955.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE VIDALIA ONIONS GROWN IN...

  4. 7 CFR 956.26 - Vacancies.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 8 2013-01-01 2013-01-01 false Vacancies. 956.26 Section 956.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE SWEET ONIONS GROWN IN THE WALLA...

  5. 7 CFR 956.26 - Vacancies.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 8 2011-01-01 2011-01-01 false Vacancies. 956.26 Section 956.26 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE SWEET ONIONS GROWN IN THE WALLA...

  6. On the interaction between perfect interstitial clusters and a vacancy in BCC, FCC and HCP metals

    SciTech Connect

    Puigvi, Mary Angels; Serra, Anna; de Diego, Nieves; Osetskiy, Yury N; Bacon, David J

    2004-01-01

    Point defects and defect clusters have been observed in metals irradiated by high-energy particles. Interactions of these defects between themselves and with existing microstructure features cause microstructure evolution and lead to changes in mechanical and physical properties of the irradiated materials. Models for prediction of radiation-induced changes should include details of reactions involving defects, and so in this paper we present the results of atomic-scale computer modelling of interactions between a cluster of self-interstitial atoms (SIAs) and a single vacancy in models of bcc, fcc and hcp metals. The vacancy is taken to lie on or within the glide prism of the cluster. This type of reaction is considered to be one of the most frequent because formation of SIA clusters, particularly glissile clusters, is commonly observed in high-energy displacement cascades in all metals. The interaction depends strongly on the dislocation nature of the cluster and therefore these interactions are different in the three crystal structures. Vacancy-SIA recombination, in particular, is inhibited by dissociation of the SIA loop on its glide prism.

  7. The effect of neutron irradiation dose on vacancy defect accumulation and annealing in pure nickel

    NASA Astrophysics Data System (ADS)

    Druzhkov, A. P.; Arbuzov, V. L.; Perminov, D. A.

    2012-02-01

    In order to investigate the dose dependence of vacancy defect evolution in nickel, specimens of high-purity Ni were neutron-irradiated at ˜330 K in the IVV-2M reactor (Russia) to fluencies in the range of 1 × 10 21-1 × 10 23 n/m 2 ( E > 0.1 MeV) corresponding to displacement dose levels in the range of about 0.0001-0.01 dpa and subsequently stepwise annealed to about 900 K. Ni was characterized both in as-irradiated state as well as after post-irradiation annealing by positron annihilation spectroscopy. The formation of three-dimensional vacancy clusters (3D-VCs) in cascades was observed under neutron irradiation, the concentration of 3D-VCs increases with increasing dose level. 3D-VCs collapse into secondary-type clusters (stacking fault tetrahedra (SFTs), and vacancy loops) during stepwise annealing at 350-450 K. It is shown that the thermal stability of SFTs grow with increasing dose level, probably, it is due to growth of the average SFT size during annealing. The results of annealing experiments on electron-irradiated Ni at 300 K are indicated in the paper, for comparison. We also have briefly discussed the positron response to the SFT-like structures.

  8. Integrated Broadband Quantum Cascade Laser

    NASA Technical Reports Server (NTRS)

    Mansour, Kamjou (Inventor); Soibel, Alexander (Inventor)

    2016-01-01

    A broadband, integrated quantum cascade laser is disclosed, comprising ridge waveguide quantum cascade lasers formed by applying standard semiconductor process techniques to a monolithic structure of alternating layers of claddings and active region layers. The resulting ridge waveguide quantum cascade lasers may be individually controlled by independent voltage potentials, resulting in control of the overall spectrum of the integrated quantum cascade laser source. Other embodiments are described and claimed.

  9. On the origin of large interstitial clusters in displacement cascades

    NASA Astrophysics Data System (ADS)

    Calder, A. F.; Bacon, D. J.; Barashev, A. V.; Osetsky, Yu. N.

    2010-03-01

    Displacement cascades with wide ranges of primary knock-on atom (PKA) energy and mass in iron were simulated using molecular dynamics. New visualisation techniques are introduced to show how the shock-front dynamics and internal structure of a cascade develop over time. These reveal that the nature of the final damage is determined early on in the cascade process. We define a zone (termed 'spaghetti') in which atoms are moved to new lattice sites and show how it is created by a supersonic shock-front expanding from the primary recoil event. A large cluster of self-interstitial atoms can form on the periphery of the spaghetti if a hypersonic recoil creates damage with a supersonic shock ahead of the main supersonic front. When the two fronts meet, the main one injects atoms into the low-density core of the other: these become interstitial atoms during the rapid recovery of the surrounding crystal. The hypersonic recoil occurs in less than 0.1 ps after the primary recoil and the interstitial cluster is formed before the onset of the thermal spike phase of the cascade process. The corresponding number of vacancies is then formed in the spaghetti core as the crystal cools, i.e. at times one to two orders of magnitude longer. By using the spaghetti zone to define cascade volume, the energy density of a cascade is shown to be almost independent of the PKA mass. This throws into doubt the conventional energy-density interpretation of an increased defect yield with increasing PKA mass in ion irradiation.

  10. On the Origin of Large Interstitial Clusters in Displacement Cascades

    SciTech Connect

    Andrew, Calder F; Barashev, Aleksandr; Bacon, David J; Osetskiy, Yury N

    2010-01-01

    Displacement cascades with wide ranges of primary knock-on atom (PKA) energy and mass in iron were simulated using molecular dynamics. New visualisation techniques are introduced to show how the shock-front dynamics and internal structure of a cascade develop over time. These reveal that the nature of the final damage is determined early on in the cascade process. We define a zone (termed 'spaghetti') in which atoms are moved to new lattice sites and show how it is created by a supersonic shock-front expanding from the primary recoil event. A large cluster of self-interstitial atoms can form on the periphery of the spaghetti if a hypersonic recoil creates damage with a supersonic shock ahead of the main supersonic front. When the two fronts meet, the main one injects atoms into the low-density core of the other: these become interstitial atoms during the rapid recovery of the surrounding crystal. The hypersonic recoil occurs in less than 0.1 ps after the primary recoil and the interstitial cluster is formed before the onset of the thermal spike phase of the cascade process. The corresponding number of vacancies is then formed in the spaghetti core as the crystal cools, i.e. at times one to two orders of magnitude longer. By using the spaghetti zone to define cascade volume, the energy density of a cascade is shown to be almost independent of the PKA mass. This throws into doubt the conventional energy-density interpretation of an increased defect yield with increasing PKA mass in ion irradiation.