Electronic structure investigation of CeB6 by means of soft X-ray scattering

The electronic structure of the heavy fermion compound CeB6 is probed by resonant inelastic soft X-ray scattering using photon energies across the Ce 3d and 4d absorption edges. The hybridization between the localized 4f orbitals and the delocalized valence-band states is studied by identifying the different spectral contributions from inelastic Raman scattering and normal fluorescence. Pronounced energy-loss structures are observed below the elastic peak at both the 3d and 4d thresholds. The origin and character of the inelastic scattering structures are discussed in terms of charge-transfer excitations in connection to the dipole allowed transitions with 4f character. Calculations within the single impurity Anderson model with full multiplet effects are found to yield consistent spectral functions to the experimental data.Comment: 9 pages, 4 figures, 1 table, http://link.aps.org/doi/10.1103/PhysRevB.63.07510

Theoretical study of resonant x-ray emission spectroscopy of Mn films on Ag

We report a theoretical study on resonant x-ray emission spectra (RXES) in the whole energy region of the Mn $L_{2,3}$ white lines for three prototypical Mn/Ag(001) systems: (i) a Mn impurity in Ag, (ii) an adsorbed Mn monolayer on Ag, and (iii) a thick Mn film. The calculated RXES spectra depend strongly on the excitation energy. At $L_3$ excitation, the spectra of all three systems are dominated by the elastic peak. For excitation energies around $L_2$, and between $L_3$ and $L_2$, however, most of the spectral weight comes from inelastic x-ray scattering. The line shape of these inelastic ``satellite'' structures changes considerably between the three considered Mn/Ag systems, a fact that may be attributed to changes in the bonding nature of the Mn-$d$ orbitals. The system-dependence of the RXES spectrum is thus found to be much stronger than that of the corresponding absorption spectrum. Our results suggest that RXES in the Mn $L_{2,3}$ region may be used as a sensitive probe of the local environment of Mn atoms.Comment: 9 pages, 11 figure

Lifetime Adherence to Physical Activity Recommendations and Fall Occurrence in Community-dwelling Older Adults: a Retrospective Cohort Study

Falling is a major health concern for community-dwelling older adults. Regular physical activity has been proposed to prevent falls. The aim of this study was to assess whether the achievement of the 2004 UK Department of Health physical activity recommendations over a lifetime had a protective effect against falling in older people. 313 community-dwelling older adults completed a questionnaire about lifetime physical activity and fall occurrence. There were significantly fewer falls in those who had led an active lifestyle compared to those who had not (χ2Yates=4.568, p=0.033), with a lower relative risk of fall occurrence for the active respondents (RR=0.671) compared to the inactive (RR=1.210). Of those who were sufficiently active in their early adulthood, the decade where there was the biggest decrease in remaining active enough was in the 60s. It is concluded that an active lifestyle may have decreased the likelihood of having a fall in older ag

Exact-exchange density-functional calculations for noble-gas solids

The electronic structure of noble-gas solids is calculated within density functional theory's exact-exchange method (EXX) and compared with the results from the local-density approximation (LDA). It is shown that the EXX method does not reproduce the fundamental energy gaps as well as has been reported for semiconductors. However, the EXX-Kohn-Sham energy gaps for these materials reproduce about 80 % of the experimental optical gaps. The structural properties of noble-gas solids are described by the EXX method as poorly as by the LDA one. This is due to missing Van der Waals interactions in both, LDA and EXX functionals.Comment: 4 Fig

Jet-Induced Nucleosynthesis in Misaligned Microquasars

The jet axes and the orbital planes of microquasar systems are usually assumed to be approximately perpendicular, eventhough this is not currently an observational requirement. On the contrary, in one of the few systems where the relative orientations are well-constrained, V4641Sgr, the jet axis is known to lie not more than ~36 degrees from the binary plane. Such a jet, lying close to the binary plane, and traveling at a significant fraction of the speed of light may periodically impact the secondary star initiating nuclear reactions on its surface. The integrated yield of such nuclear reactions over the age of the binary system (less the radiative mass loss) will detectably alter the elemental abundances of the companion star. This scenario may explain the anomalously high Li enhancements (roughly ~20-200 times the sun's photospheric value; or, equivalently, 0.1-1 times the average solar system value) seen in the companions of some black-hole X-ray binary systems. (Such enhancements are puzzling since Li nuclei are exceedingly fragile - being easily destroyed in the interiors of stars - and Li would be expected to be depleted rather than enhanced there.) Gamma-ray line signatures of the proposed process could include the 2.22 MeV neutron capture line as well as the 0.478 MeV 7Li* de-excitation line, both of which may be discernable with the INTEGRAL satellite if produced in an optically thin region during a large outburst. For very energetic jets, a relatively narrow neutral pion gamma-decay signature at 67.5 MeV could also be measurable with the GLAST satellite. We argue that about 10-20% of all microquasar systems ought to be sufficiently misaligned as to be undergoing the proposed jet-secondary impacts.Comment: ApJ, accepted. Includes referee's suggestions and some minor clarifications over previous versio

Telecommunications systems design techniques handbook

Handbook presents design and analysis of tracking, telemetry, and command functions utilized in these systems with particular emphasis on deep-space telecommunications. Antenna requirements are also discussed. Handbook provides number of tables outlining various performance criteria. Block diagrams and performance charts are also presented

Resonant Inelastic X-Ray Scattering at the K Edge of Ge

We study the resonant inelastic x-ray scattering (RIXS) at the $K$ edge of Ge. We measure RIXS spectra with systematically varying momenta in the final state. The spectra are a measure of exciting an electron-hole pair. We find a single peak structure (except the elastic peak) as a function of photon energy, which is nearly independent of final-state momenta. We analyze the experimental data by means of the band structure calculation. The calculation reproduces well the experimental shape, clarifying the implication of the spectral shape.Comment: 17 pages,9 figures, Please also see our related paper: cond-mat/040500

Unscreened Hartree-Fock calculations for metallic Fe, Co, Ni, and Cu from ab-initio Hamiltonians

Unscreened Hartree-Fock approximation (HFA) calculations for metallic Fe, Co, Ni, and Cu are presented, by using a quantum-chemical approach. We believe that these are the first HFA results to have been done for crystalline 3d transition metals. Our approach uses a linearized muffin-tin orbital calculation to determine Bloch functions for the Hartree one-particle Hamiltonian, and from these obtains maximally localized Wannier functions, using a method proposed by Marzari and Vanderbilt. Within this Wannier basis all relevant one-particle and two-particle Coulomb matrix elements are calculated. The resulting second-quantized multi-band Hamiltonian with ab-initio parameters is studied within the simplest many-body approximation, namely the unscreened, self-consistent HFA, which takes into account exact exchange and is free of self-interactions. Although the d-bands sit considerably lower within HFA than within the local (spin) density approximation L(S)DA, the exchange splitting and magnetic moments for ferromagnetic Fe, Co, and Ni are only slightly larger in HFA than what is obtained either experimentally or within LSDA. The HFA total energies are lower than the corresponding LSDA calculations. We believe that this same approach can be easily extended to include more sophisticated ab-initio many-body treatments of the electronic structure of solids.Comment: 11 papes, 7 figures, 5 table