Surface photoemission in the 4d band from polycrystalline silver surfaces

Surface induced local d-band states in the upper 4d band between ～ 4 and ～ 5.2 eV below E_Fermi have been identified for polycrystalline silver films in photoemission experiments using synchroton radiation. A thin over-coat (10 å) by an Al film leads to a depression of these surface induced local states whereas a change from s- to p-polarized excitation leads to an enhancement. Deposition of additional silver (～ 3 Å) at 120 K induces additional emission 4.2 eV below E_F with a FWHM of only ～ 0.4 eV.     

Pressure dependent optical absorption edge shift and compressibility of CdCr2Se4 single crystals

The pressure shift of the optical absorption edge (dE_g/dp = (1.1 ± 0.1) × 10^?6 eV bar^?1) and the compressibility (κ = (1.3 ± 0.) × 10^?6 bar^?1) of single crystalline CdCr₂Se₄ have been measured at ambient temperature. These data suggest an interpretation of the fundamental absorption in terms of either p → p interband or p → localized d charge transfer transitions, but exclude excitations involving s-band states.     

Surface states ond-band metals

Electron surface states ond-band metals are investigated by the method of matching the crystal wave function to the outside solution at the surface. On a (100) surface of anfcc structure such a state is found near to the crossover of thes-band and thed-band of the same symmetry. In Ni this state lies 4–5 eV below the Fermi energy, for Cu 5–6 V beloweE _F. It explains the density of states anomaly seen in photoemission.     

Electronic structure of MnSb

On the basis of a two center tight binding model the recursion method of Haydock et al. was applied to calculate spin polarized and non-polarized electronic densities of states and magnetic moments for the B8₁ crystal structure and a fictitious B32 structure of MnSb. The model implies the itinerant nature of the Mn d-states hybridizing with Sb p-states. For the non-polarized densities of states the self-consistent charge transfer amounts to 0.6 electrons from Mn to Sb with a band center difference of E_p ? E_d = - 0.75 eV. For the magnetic moments, which were also calculated self-consistently, 3.5 μ_B for the d-band and 3.34 μ_B in total were obtained for the B8₁ crystal structure. For the B31 structure bigger moments of 3.67 μ_B and 3.53 μ_B were obtained, correspondingly. The results for MnSb are also discussed with respect to very recent results for MnAs calculated within the same model. The local densities of states as obtained for MnSb are in good agreement with experimental XPS results.     

Energy spectra of cosmic pions and nucleons at the top of the atmosphere

The production spectra of cosmic pions and their primaries have been derived from the experimental muon spectrum by using the theories of Barrettet al. and Feynman. The calculated pion production spectrum takes the formI(E _π)d E _π = 0.206E _π ^{? 2.65} d E _πper cm² sec str GeV in the energy range 3<E _π<1500 GeV and the nucleon spectrum follows the relationN(E _p)d E _p = 2.7 × 10⁴ (E _p/GeV)^2.65 d E _pper m² sec str GeV in the range 5 <E _p <3000 Gev.     

Effect of pressure on superconductivity in transition metal alloys

Measurements on twelve alloys of the series Zr-Nb-Mo show a close correlation ofdT _c /dp with thed-band structure of these alloys and suggest that thed-band is virtually rigid with respect to pressure. The results are not compatible with an empirical observation of McMillan thatT _c is governed only by a phonon factor Mω ².     

Volume dependence of the spin-orbit splitting in the Au d-band

Self-consistent, Dirac relativistic band-structure calculations have been performed for gold with compressed as well as expanded lattices. Although spin-orbit (SO) parameters usually increase under compression it was found that, in the volume ranges considered here, the SO-splittings in the Au d-band have a positive volume derivative. This is mainly due to the volume-dependent SO-induced hybridization between the E_gandT_2g states.     

Optical absorption and electronic structure of intermetallic compound RuIn3

The optical properties of intermetallide RuIn₃ are investigated by ellipsometry in the spectral range of 0.22–10 μm. The experimental data point to the existence of an energy gap of about 0.5 eV in the electronic spectrum of the compound. The density of the electron states and interband optical conductivity are calculated in terms of the density functional theory. The experimental and theoretical spectra of the optical conductivity are compared. It is found that the formation of basic absorption bands is caused by interband transitions of electrons of the d-band of Ru and p-band of In.     

Electroreflectance of bound excitonic states in semiconductors

While first-derivative spectroscopy (thermoreflectance, piezoreflectance, wavelength derivative modulation) has a general validity, no matter whether one is studying interband or excitonic transitions (involving also bound states), things are more complex in the case of electroreflectance (ER). As a matter of fact, Aspnes and Rowe's third-derivative theory does not include bound excitonic states. Using a phenomenological approach one can see that only in the case of a strong mixing between d³ε_r/dE³ and d³ε₁/dE³ it is possible to observe a qualitative agreement between Δε and d³ε/dE³ in some particular cases where Wannier excitonic series gives a predominant contribution to the optical spectra.     

Temperature dependence of the fundamental absorption edge in CuGaSe2

The temperature dependence of the fundamental absorption edge in CuGaSe₂ single crystals was determined in the temperature range from 15 to 300 K. Above about 120 K the gap energy changes linearly with temperature with dE_g/dT = ? (2.1 ± 0.1) eV K^?1. The downshift in dE_g/dT of the I–III–VI₂ compounds compared to their II–VI analogs is discussed accounting for the p-d hybridization of the uppermost valence band.     

Low-Spin Ferriheme Models of the Cytochromes: Correlation of Molecular Structure with EPR and Mössbauer Spectral Parameters

The electronic properties of the intermetallic compound HfCo₃B₂ were investigated using combined TDPAC measurements and first principles LAPW calculations. The V _zz value at the hafnium site is determined from dominant positive p–p contribution, with less than 20%, negative s–d and d–d contributions. Based on the calculated density of state (DOS) at 0 K, a band contribution (γ _band) of 7.26 (mJ/mol/K²) to the value of the electronic specific heat coefficient (γ) was obtained. This relatively low γ _band value is attributed to the hybridization between hafnium d-states, boron 2p-states and cobalt 3d-states, formed at the energy interval below E _Fermi. This hybridization, together with the dip in the DOS around E _Fermi, implies a possible reduction of the low temperature magnetic moment in this compound.     

Energy dissipation in the deterministic and nondeterministic Nagel-Schreckenberg models

In this paper, we numerically study energy dissipation per unit time per car E_d in the Nagel-Schreckenberg (NS) model. Numerical results show that there is a critical density over which energy dissipation occurs, but below which no energy loss happens in the deterministic NS model. Energy dissipation depends on both the car density and initial configuration in the deterministic case. The energy dissipation rate, E_d, calculated starting from a completely jammed state whose value is minimum, decreases monotonously with the increase of car density above the critical density. In the nondeterministic case, however, there is no critical density and energy dissipation happens in the whole density region, and initial configuration has no effects on energy dissipation. The dissipated energy has two different contributions: one coming from the interactions and another from the braking noise in the stochastic case. The relative contributions of the two dissipation mechanisms are presented. In the free-flow state, E_d is proportional to p(1−p) where p is the stochastic braking probability. In the case of v_max=1,E_d is proportional to the mean density of “go and stop” car per time step ρ_gs, which is equal to n₀(1−n₀) where n₀ is the fraction of stopped car. Theoretical analyses give an excellent agreement with numerical results.     

Secondary electron emission yield behaviour of polymers

The secondary electron emission yields of highly-insulating, thin polymer foils have been measured for incident primary beam energies, 50 ? E_p ? 2500 eV. The results follow closely a ‘universal’ reduced yield curve determined by the energy loss law, dE_p/dx = -A/E_p^n-1, where n = 2 and A is a constant proportional to the density of the solid, as predicted by the elementary theory of Lye and Dekker (1957). This behaviour remains true up to high primary beam energies and, as such, is unique to these low density solids.     

Hydrogen-induced states in VHx and VDx observed by soft X-ray emission spectroscopy

From measurements of soft X-ray emission spectra (V-L₃) of VH_x and VD_x, a gradual change of d-band of V metal with addition of H(D), and an appearance of H(D)-induced states immediately below the d-band, are clearly demonstrated. The states, located at 7 eV below the Fermi energy for all compositions, are interpreted as being bonding states formed by H(D)-1s and V-3d orbitals. No isotope effects were detected within the accuracy of the experiment.     

Effect of hydrostatic pressure on the hole effective mass in a strained InGaAs/GaAs quantum well

A systematic analysis of the hydrostatic pressure effects on the effective masses of holes in strained single In_xGa_1−xAs/GaAs quantum-well (Qw) is performed. The strain effect on the shift of the subband energies and the effective masses is also investigated. A 14-band k.p Hamiltonian matrix is used in the calculations and solved by iteration with the Bir–Pikus Hamiltonian. Numerical results have been presented over a pressure range from 0 to 16 kbar. Our results show that especially for the calculation of the light-hole mass, it is necessary to use the 14-band and not the 8-band k.p model. This is supported by the fact that the 8-band k.p model predicts an increasing mass with pressure which does not reproduce the experimental results. Finally our calculations clearly confirm the available experimental results given in the literature.     

A study of the121,123Sb(p,d) reactions

Levels of^120,122Sb have been observed using the^121,123Sb(p, d) reactions atE _p = 26.2 MeV. Thirty-two levels of¹²⁰Sb and thirty-four levels of¹²²Sb are observed below 2.0 MeV excitation with an energy resolution better than 25 keV FWHM. Experimental angular distributions were compared to DWBA calculations in order to extractl-transfers and spectroscopic factors. Strong mixing between the 3s _1/2, 2d _3/2, 2d _5/2, and 1g _7/2 neutron orbitals is observed in both nuclei. Nuclear Reactions:^121,123Sb(p, d),E=26.2 MeV; measuredσ(E _d ,θ).^120,122Sb deduced levels,l,J,π, spectroscopic factors. Enriched targets, magnetic spectrometer.     

Application of X-ray photoelectron spectroscopy to characterization of Au nanoparticles formed by ion implantation into SiO2

In X-ray photoelectron spectroscopy (XPS) of Au nanoparticles, the width of 5d valence band changes with Au particle size. This enables us to estimate the size of Au nanoparticles by using XPS. In this work, the 5d-band width has been measured for Au nanoparticles formed by ion implantation into SiO₂. The 5d-band width is found to be correlated strongly with the Au concentration. As the Au concentration increases, the 5d-band width becomes larger, indicating that the Au nanoparticles with the larger size tend to be formed in the vicinity of the projected range of Au ions. This correlation agrees very well with the results from transmission electron microscopy.     

The energy dependence of single particle spectra in e+e− annihilation

We present explicit predictions of the statistical bootstrap model for inclusive single particle spectra in e⁺e^? annihilation. The distribution (ω/σ_tot·E) (dσ/p² dp) is found to become, for E ? 3 GeV, a function only of the secondary energy ω, independent of the incident e⁺d^? energy E.     

Effect of carrier concentration on the reflectivity spectrum of Ge and InSb

We have measured at 5 K the derivative spectra (1/R) dR/dE around the E₁ and E₁ + Δ₁ structures, of Ge and InSb with different impurity concentrations. In the more highly doped samples, the peaks are broadened and shifted slightly to lower frequencies. The change in the value of (1/R) dR/dE is much larger than recently predicted by Seraphin and Aspnes, based on the surface field effect. Different possibilities for the effect are discussed. Wavelength modulation measurements on samples with an applied surface electric field have shown no difference.