The effect of temperature on the pulsed conductivity of a KCl crystal excited by picosecond electron pulses

This paper discusses the temperature dependence of the pulsed conductivity of a KCl crystal in the interval 12–300K when it is excited by an electron beam (0.2 MeV, 50 ps, 300A/cm²) with a time resolution of 150 ps. It is shown that the electron lifetime is τ<100 ps in the entire interval under consideration, while the conductivity increases with temperature. The experimental results make it possible to obtain the temperature dependences of the effective electron-hole recombination cross section S∼T ^3.5 and the separation probability of genetic pairs. Fiz. Tverd. Tela (St. Petersburg) 41, 429–430 (March 1999)     

Kinetics of the failure of loaded materials at variable temperature

The possibility of predicting the lifetime of loaded materials at variable (increasing) temperature is demonstrated on the basis of a kinetic approach to the problem of the failure of such materials. Zh. Tekh. Fiz. 68, 76–81 (November 1998)     

Quasiparticles in the theory of fermion condensation

It is shown that Landau’s quasiparticle formalism continues to work in systems with a fermion condensate. In the case of a finite system this formalism is suitable for describing the restructuring of states at the Fermi surface. It also works in an infinite system, and the idea of quasiparticles at low temperature as well-defined excitations at the Fermi surface remains valid. The quasiparticle lifetime is directly proportional to the temperature, and the density of states is inversely proportional to the temperature. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 9, 719–723 (10 May 1996)     

Dynamics of nanodefects on a loaded gold surface

The dynamics of defects with linear dimensions from ≈1 to ≈100 nm on a Au surface under load have been studied by means of tunnelling microscopy. It is found that the origin, growth, and resorption of the defects is caused by displacements of bands of material from 5 to 50 nm wide, parallel to the {111} slip planes. The defects can be separated into two groups: nonsteady-state defects, whose lifetime does not exceed 15 min, while the depth is ⩽20 nm, and quasi-steady-state defects, with a lifetime three orders of magnitude greater than the first. It is assumed that the nonsteady-state defects are formed when the ensemble of dislocations is being reconstructed, while the quasi-steady-state defects are formed at the instant of formation of dislocation substructures during the creep of the loaded metal. Fiz. Tverd. Tela (St. Petersburg) 40, 2180–2183 (December 1998)     

Direct measurements of energy relaxation times on an AlGaAs/GaAs heterointerface in the range 4.2–50 K

The temperature dependence of the energy relaxation time τ_e (T) of a two-dimensional electron gas at an AlGaAs/GaAs heterointerface is measured under quasiequilibrium conditions in the region of the transition from scattering by acoustic phonons to scattering with the participation of optical phonons. The temperature interval of constant τ_e, where scattering by the deformation potential predominates, is determined. In the preceding, low-temperature region, where piezoacoustic and deformation-potential-induced scattering processes coexist, τ _e decreases slowly with increasing temperature. Optical phonons start to participate in the scattering processes at T∼25 K (the characteristic phonon lifetime was equal to τ_LOτ4.5 ps). The energy losses calculated from the τ_e data in a model with an effective nonequilibrium electron temperature agree with the published data obtained under strong heating conditions. Pis’ma Zh. éksp. Teor. Fiz. 64, No. 5, 371–375 (10 September 1996)     

Perturbation theory for the π+π− atom

A perturbation-theory framework is developed for calculation of the characteristics of the atom π ⁺π⁻ on the basis of the field-theoretic Bethe-Salpeter approach. A closed expression is obtained for the first-order correction to the lifetime of the π⁺π⁻ atom. Pis’ma Zh. éksp. Teor. Fiz. 66, No. 12, 747–752 (25 December 1997) Published in English in the original Russian journal. Edited by Steve Torstveit.     

Elasticity of a cryo-insulation polymer foam coating in the temperature range 8–293 K

An apparatus is developed for investigating the dynamic deformation properties of cryoinsulation coatings in the temperature range 8–293 K. One type of cryo-insulation material — polyurethane foam — is chosen as the object of investigation. Test measurements on a polyurethane foam “pack” (metal substrate with a polyurethane foam coating) are performed at 0.01 Hz in the temperature range 8–293 K. A jump in the temperature dependence of the dynamic shear modulus (by two orders of magnitude) is observed in the temperature range 54–63 K. This feature is attributed to the solidification of the air present in the pores of the polyurethane foam. Such a transition results in cementation of the polyurethane skeleton of the coating by the nitrogen and oxygen “ice” that is formed. Zh. Tekh. Fiz. 69, 116–118 (February 1999)     

The lifetime of the soliton in the improved Davydov model at the biological temperature 300 K for protein molecules

We study the effects of quantum fluctuations and thermal perturbations on the lifetime of the soliton in the improved Davydov model proposed by us with two-quanta and with an added interaction. By using quantum perturbation theory, we compute the soliton lifetime for a wide ranges of parameter values relevant for protein molecules. The lifetime of the new soliton at the biological temperature 300 K is of the order of 10^-10 second or τ/τ≥ 500 for parameters appropriate to α-helical protein molecules. This shows clearly that the new soliton in the improved model is a viable mechanism for the bio-energy transport in the α-helix region of proteins. Received 7 January 1999 and Received in final form 16 August 2000     

Alpha decay of the first excited state of the Th-229 nucleus

The α decay of the anomalously low-lying isomeric level 3/2⁺ (3.5±1.0 eV) of the ²²⁹Th nucleus is studied. The lifetime of the isomer with respect to a decay is predicted and the spectrum of the emitted a particles is calculated. It is noted that the complete α spectrum of the isomer and accelerated α decay of ²²⁹Th can be observed by exciting the nuclei with laser radiation. Pis’ma Zh. éksp. Teor. Fiz. 64, No. 5, 319–323 (10 September 1996)     

Phase transitions in a system of unstable particles

A study is reported of phase separation in a system of particles created at a constant rate and having a finite lifetime. It is shown that (1) phase separation is possible if the particle lifetime exceeds a certain critical value, (2) the particle-density difference between the phases depends on particle lifetime, and (3) the correlation function in the two-phase region oscillates (with damping) as a function of spatial coordinates, which implies correlation between the phase locations. Fiz. Tverd. Tela (St. Petersburg) 40, 741–745 (April 1998)     

Millimeter microwave study of the superconducting properties of the Cu-C system

A study has been made of a cylindrical Cu-C powder sample operated as a microwave antenna at 35 GHz in the 80–300-K temperature interval. The efficiency of such an antenna is shown to increase nearly twofold from room temperature to liquid nitrogen temperature, which is apparently associated with a superconducting transition close to 80 K. Fiz. Tverd. Tela (St. Petersburg) 39, 816–817 (May 1997)     

Temperature dependence of magnetophonon resistance oscillations in GaAs/AlAs heterostructures at high filling factors

The temperature dependence of the magnetic-field resistance oscillations induced by acoustic phonons in a 2D system with a moderate mobility and a high electron density in the range T = 7.4–25.4 K has been studied. It has been established that the amplitude of the magnetophonon resistance oscillations in the system under study is determined by the quantum lifetime modified by the electron-electron scattering, in accordance with the results recently obtained in a GaAs/AlGaAs heterostructure with an ultrahigh mobility and a low electron density [A. T. Hatke et al., Phys. Rev. Lett. 102, 086808 (2009)]. The shift of the main maximum of the magnetophonon resistance oscillations to higher magnetic fields with increasing temperature is observed.     

Semiconductor-metal phase transition under a strain induced by a spherical indenter

A semiconductor-metal phase transition is produced in samarium monosulfide under the action of the pressure of a spherical indenter in the region of quasiuniaxial compression of the sample material under the indenter and investigated. It is shown that the phase transition occurs when the decrease in the volume of SmS under the action of the applied field reaches a critical value of 4–5% at T=300 K. The temperature dependence of the critical volume decrease is recorded in the range 280–440 K. Zh. Tekh. Fiz. 68, 53–57 (March 1998)     

Spectroscopy of GaAs/AlGaAs microstructures with submicron spatial resolution using a near-field scanning optical microscope

A near-field scanning optical microscope (NSOM), which we built, is used to investigate 1–5-μm wide stripes with a 10-nm thick layer—a quantum well — on a GaAs surface. A map of the photoluminescence intensity is obtained synchronously with the topographic profile of the structures. The measured spatial distribution of the photoluminescence intensity is described satisfactorily in a model that takes into account carrier diffusion in the layer and the existence of a region with a short carrier lifetime near the side boundaries of the layer. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 7, 523–527 (10 April 1996)     

Low-temperature diffusion of gold in germanium under the influence of atomic hydrogen

An investigation is made of the diffusion of gold in germanium under the influence of the energy released by the recombination of hydrogen atoms to form molecules. Crystals of n-type germanium with gold films (d=1×10⁻⁷ m) are exposed to atomic hydrogen for various times (up to 10⁴ s) at temperatures close to room temperature. The diffusion of gold in the germanium is analyzed by laser mass spectrometry, and also by measuring the surface resistance, the minority carrier lifetime, and the infrared transmission spectra. Mechanisms are proposed for the stimulation of heterodiffusion and accompanying processes. Zh. Tekh. Fiz. 69, 73–76 (July 1999)     

Positron lifetime measurements inn- andp-type silicon

Positron lifetime measurements were carried out in four different samples of silicon, namelyn-type (P-doped) 75 Ωcm,n-type (Sb-doped) 0.018 Ωcm,p-type (B-doped) 60 Ωcm andp-type (B-doped) 0.02 Ωcm. The measurements were made at room temperature and at 77K. A positron lifetime of τ₁=(230±2) psec was found for all samples, independant of dopant or temperature. Paper A 17 presented at 3 rd Internat'l Conf. Positron Annihilation. Otaniemi, Finland (August 1973).     

Simulation of arbitrary deformations of polycrystals by the method of cellular atomata

A computer model for the deformation of polycrystals is developed, based on the concept of cellular automata. The model is used to investigate a polycrystal by treating it as a multilevel hierarchical system, and to study the peculiarities in the behavior of this system as a function of the material structure, mechanisms of low-level deformation, history of loading and/or deformation at the top hierarchical level, the temperature, and other parameters. Zh. Tekh. Fiz. 68, 130–132 (November 1998)     

Evolution of spiral dynamic magnetic domains in Anger states of iron garnet films

Dynamic domain structures in the Anger state of iron garnet films are analyzed by a video micrographic technique. Data are obtained on the evolution of individual spiral domains over the lifetime of each domain. A new mechanism for the destruction of this state is discovered. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 6, 453–456 (25 March 1996)     

Creation of excitons and defects in a CsI crystal during pulsed electron irradiation

Data presented on the influence of the temperature in the range 80–650 K on the spectral kinetics of the luminescence and transient absorption of unactivated CsI crystals under irradiation by pulsed electron beams (〈E〉=0.25 MeV, t _1/2=15 ns, j=20 A/cm²). The structure of the short-wavelength part of the transient absorption spectra at T=80–350 K exhibits features, suggesting that the nuclear subsystem of self-trapped excitons (STE’s) transforms repeatedly during their lifetime until their radiative annihilation at T⩾80 K, alternately occupying di-and trihalide ionic configurations. It is established that a temperature-induced increase in the yield of radiation defects, as well as F and H color centers, and quenching of the UV luminescence in CsI occur in the same temperature region (above 350 K) and are characterized by identical thermal activation energies (∼0.22 eV). It is postulated that the STE’s in a CsI crystal can have a trihalide ionic core with either an on-center or off-center configuration; the high-temperature luminescence of CsI crystals is associated with the radiative annihilation of an off-center STE with the structure (I⁻(I⁰I⁻ e ⁻))*. Fiz. Tverd. Tela (St. Petersburg) 40, 640–644 (April 1998)