摘要:

The methods are described for producing unstable paramagnetic excited states in rare gas cryocrystals Ne, Ar, Kr, and Xe through the trapping, in the cryocrystals growing from the gas phase, the products of the gas discharge taking place in the same or other rare gas. The paper presents a technique and results of an observation and investigation of excited states in rare gas cryocrystals with electron paramagnetic resonance (EPR). The discovered unstable paramagnetic centers are interpreted as being local metastable excitednp5(n+1)satomic-type states in rare gas cryocrystals which are subject to the action of the anisotropic electric field resulted from the crystal surroundings distorted by the center. An account is given of the mechanisms for formation of observed paramagnetic excited states in cryocrystals which arise owing to the excitation energy of the metastable3P2atoms of Ne, Ar, Kr, Xe and He23S1and21S0atoms that form in the discharge in an appropriate gas and trap in the growing cryocrystal. ©1998 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593670

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Relaxation processes in a phonon–impuriton systems of superfluid3He–4Hemixtures are studied on the basis of the system of kinetic equations. The obtained general energy–momentum relations are valid for any ratio of the times of phonon–impuriton interaction to the times of equilibrium stabilization in the phonon and impuriton subsystems. In the hydrodynamic and kinetic modes of phonon rates, the effective diffusion coefficient for the dissipative mode as well as the velocity and attenuation of sound in the acoustic mode are calculated. ©1998 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593671

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A dynamic mechanical method using a weak low-frequency magnetic field is proposed for investigation of stimulated dynamics and pinning in the Abrikosov vortex lattice in type II superconductors. It is shown that the application of a weak a.c. field facilitates depinning of Abrikosov vortices and additional dissipation of energy by liberated vortices. As the frequency of the field increases, a mode in which the vortices virtually do not oscillate is attained, i.e., dissipation ceases, while pinning is extremely effective. The observed effects can be successfully explained on the basis of the Gor’kov–Kopnin theory. ©1998 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593672

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Peculiarities of the electromagnetic power absorption are investigated at extreme points of magnetic field dependences in high-Tcsuperconductors. A linear dependence of absorption on the magnetizing field at the points of minima on the curves is established. It is shown that the main contribution to absorption at these points comes from hf losses directly in grains. The relative value of losses at the minima on magnetic field curves can be used for estimating the grain quality. ©1998 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593673

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The magnetic ordering model is considered for a single-lattice spin subsystem withS=1and a large biquadratic exchange whose energy has the same order of magnitude as the bilinear exchange interaction energy. The expression for free energy is obtained in the microscopic approximation, and the phase states are defined and analyzed. The Landau potential is represented as a power expansion in the model microscopic free energy. This expression is used to describe the peculiarities of the temperature dependences of the magnetic susceptibility and magnetoelastic deformation. ©1998 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593674

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Transmission spectra of synthetic and natural hematite(&agr;-Fe2O3)crystals are measured at temperatures 10, 25, and 300 K in the wavelength range 500–1100 nm, and the absorption spectra are computed. Pure exciton and exciton–magnond–dtransition bands are revealed, the corresponding wavelengths at 10 K being&lgr;0=1020 nmand&lgr;1=965 nmrespectively. The half-widths and oscillator forces areg0=84 cm−1,f0=4×10−9,g1=60 cm−1,f1=1.4×10−7for 10 K,g0=85 cm−1,f0=5×10−9,g1=110 cm−1,f1=2.1×10−7for 25 K. The mechanisms of band formation for weakly allowedd–dtransitions in hematite are analyzed. ©1998 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593675

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The tunnel resistance of highly stable, mechanically controlled break junctions of Al, Au, Cu, Pb, Ni, Pt, and Pt–Ir, have been recorded as a function of the electrode spacing over 6–7 decades. Clear deviations from the expected exponential behavior have been observed. Comparison with previous experimental and theoretical studies indicate that the discussed deviations in some cases are most probably due to the shape of, rather than to interactions between, the two electrodes. ©1998 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593676

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A detailed theory of electron–electron scattering in two-dimensional degenerate systems in heterostructures is constructed as a result of analysis and numerical computations. The conditions are formulated and the values of characteristic parameters are obtained for which specific two-dimensional effects predicted earlier from theoretical considerations can be observed. New properties of scattering indicatrix, viz., a beam of electrons flying almost antiparallel to the primary beam and a very narrow beam of holes flying in the forward direction, are found. ©1998 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593663

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The impact of monochromatic low-energy electrons (4–52 eV) is found to induce desorption of metastable particles (MP) from multilayer films formed by condensing CO gas on a Pt(111) substrate held at 20 K. The results are compared with metastable production from gaseous CO. Metastable CO(CO*)is identified as the major desorbed species, its desorption is discussed in terms of intramolecular to molecule-surface vibrational energy transfer. Primary electronic excitation proceeds via the states,a′3&Sgr;+,d3&Dgr;,e3&Sgr;−,I1&Sgr;−,andD1&Dgr;which contribute to MP desorption directly or by first decaying in high vibrational levels of thea3&Pgr;configuration. The energy threshold of 8.0 eV forCO*desorption indicates that CO in low vibrational levels of thea3&Pgr;state does not desorb. Electronic excitation occurs either near the surface of the CO film or in the bulk. In the latter case, excitonic motion to the surface can be followed byCO*desorption. ©1998 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593664

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A simple model of the dynamics of a layered crystal having a hexagonal lattice with weak interaction of atoms in neighboring basal planes is formulated. Vibrations propagating in the basal plane with displacement vectors lying in the same plane are investigated. Energy–momentum relations are obtained for low-frequency (Rayleigh type) as well as high-frequency (gap-mode) vibrations localized at the free surface. The region of existence of quasi-surface phonons, whose boundaries are determined to a considerable extent by the shape of constant-frequency surfaces for two branches of bulk vibrations is determined. It is shown that peculiarities in the interaction of elastic waves with the crystal surface appear in the bulk spectrum at certain frequencies. The dispersion curves for surface vibrations separated from the continuous spectrum have a continuation in this spectrum in the form of dependences corresponding to transformation of a transverse wave into a longitudinal one. The effect of a surface monolayer of impurity atom on localized and pseudolocalized vibrations is investigated. ©1998 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593665

出版商:AIP    

年代:1998

数据来源: AIP