Dynamical susceptibilities of intermediate valence compounds

Relaxation rates of magnetic moment and charge are discussed for systems showing intermediate valence. The periodic Anderson model and a more realistic model with periodic 4f shells are investigated by the use of the Mori formalism. It is shown that the relaxation of the 4f moment and the charge above the spin fluctuation temperature is dominated by the second order process with respect to the hybridization interaction and is nearly independent of temperature. The moment relaxation rate is significantly larger than that in the integral valent case where the fourth order Korringa process is dominant. The theory can explain the anomalously large width and the momentum independent nature of the quasi-elastic component of the neutron scattering on intermediate valence compounds.Work performed under the research program SFB 125 Aachen-Jülich-KölnOn leave of absence from the Department of Applied Physics, Tohoku University, Sendai 980, Japan     

Steady oscillatory states of a finite Josephson junction

Under the assumption that solutions have traveling-wave form, time-periodic solutions are found for the Josephson phase equation for a finite-length tunnel junction with uniform current feed and linear loss term. Exact current-voltage characteristics are found and compared with simple approximations. The complete current-velocity and mean-width-velocity curves for isolated fluxons are found. Comparison with characteristics for a finite junction shows that end effects obtained from analysis of a circuit model of the junction shows that end effects introduce lower- and upper-current thresholds.     

More on finite element modeling of damped composite systems

Finite element procedures are developed and verified for layered beams and rings having either continuously or discontinuously constrained viscoelastic damping layers. The two configurations considered are (1) a three-layered sandwich beam or ring (closed curved beam) consisting of two thin elastic layers with a viscoelastic core in between, and (2) a damped composite made of a thin-walled elastic structure having a finite number of mass segments or elastic segments adhered to it by a viscoelastic material. Viscoelastic material dependence on frequency and temperature is accounted for. Numerical predictions of transverse driving point impedances agree very well with available experimental data.     

The out-of-plane vibrational modes of chlorobenzene in its ground and first singlet excited states

The study of 2699 Å electronic band system of chlorobenzene has been extended to extract out all the six b₁ and three a₂ modes in both the ground state (^eA₁) and the electronically excited first singlet state (^eB₂). The procedure of the extraction of these modes on the basis of observed sequences, cross-sequences, and overtones has especially been elaborated. Strong Fermi interaction has been observed between the vibrational level ν′_6b and combination level ν′_16a + ν′_16b in ^eB₂ state. The uniqueness of the assignments of the modes has been critically discussed.     

Capture cross-section and density of deep gap states in a−SiHx schottky barrier structures

Recombination of charge carriers in a?SiH_x Schottky barriers with density of states near mid-gap ranging from 2.8×10¹⁵?7×10¹⁶cm^-1eV^-1 is attributed to recombination centers with hole capture cross-section of 1.3×10^-15cm².     

Acoustic plasmons in a two-band metal

The properties of acoustic plasmon excitations and the conditions for their existence in a metal with two overlapping bands one of which is narrow (d-band) and the other broad (s-band) are discussed. Model calculations in which the d-electrons are treated in the tight-binding approximation and the s-electrons are assumed to be free are presented. The prospects for finding well defined acoustic plasmons in a real system are examined. The example of the V₃Ga crystal is considered in some detail.     

Germanium lasers in the range from far-infra red to millimetre waves

Recent experimental and theoretical achievements are reviewed on three types of laser oscillation inp-type germanium; the intervalence band (IVB) laser oscillation due to transitions between the light-hole band and the heavy-hole band, the light-hole cyclotron resonance (LHCR) laser oscillation, and the heavy hole cyclotron resonance (HHCR) maser oscillation. Described for the IVB oscillation are fundamental characteristics (such as the wavelength range of oscillation and the cooperation with higherharmonic cyclotron resonances), the polarization characteristics of radiation and influence of uniaxial stress on the oscillation. The present status of the attempt at single line oscillation is also described. As for the LHCR oscillation, the formation of population inversion and the amplification are explained on the basis of quantum mechanical calculations of the valence bands in crossed electric and magnetic fields.     

Dynamics of lateral modes in broad aperture injection lasers

The dynamics of optical filaments in broad aperture semiconductor lasers was studied. We use the model where one longitudinal mode is taken into account. The spectrum and the instabilities of lateral modes joined with the above mentioned longitudinal mode were investigated. The structures arise due to instability of various number of lateral modes. On the background of these modes we found a new type of modulation with a frequency depending on the laser aperture width. This frequency is smaller than the electron-photon resonance one. The existence of the modulation was confirmed by experimental investigations of broad aperture laser noise spectra.     

Low noise 80–115 GHz quasiparticle mixer with small Nb/Al-Oxide/Nb tunnel junctions

Millimeter-wave characterization of a heterodyne receiver using (2 m²) Nb/Al-Ox/Nb Superconducting-Insulator-Superconducting (SIS) junctions arrays is reported. The fabrication of the Nb/Al-Ox/Nb SIS junction arrays as a heterodyne mixer is described. The leakage current of these junctions is below 2A at 4.2K and unmeasurable at 2.5K. The receiver gave a noise temperature Double Side Band (DSB) between 63K and 187K over the frequency range 80 to 115 GHz at the first conversion peak. The results are comparable to those obtained with SIS receivers using well researched lead junctions. Contrary to the lead junctions, our mixer using all Nb junctions have proven remarkably stable with respect to thermal cycling, characteristics which are required for space applications. To our knowledge, this is the most reliable low noise receiver operating in this frequency range.