Photoexcitation is examined for an inherent nondegenerate semiconductor with different masses for the electrons and holes. The study relates to three limiting cases of relaxation within the bands: slow, fast, and intermediate. Expressions are derived for the electron and hole concentrations and average energies. A study is made of the effects of electron-electron relaxation on the photoexcitation.
Show AbstractAn analytic expression is derived, for the pulse-height distribution at the output from a channel electron multiplier СЕМ working under unsaturated conditions, this being a function of the mean secondary-emission coefficient. A method is given for determining the efficiency of a СЕМ by analyzing the pulse-height distribution at the output. A comparison is made of the recording efficiency for VEU-6 electron detectors recorded in this way with other experimental data.
Show AbstractA microscopic quantum-field description is used in considering the evolution of a one-photon wave packet in a periodically deformed lattice. The Ewald-Oseen theorem is proved for this case.
Show AbstractThe interaction between an electron and an adsorbed oxygen molecule is discussed. A mechanism is proposed for this interaction that explains the peak on the electron-stimulated desorption at an electron energy of 13 eV.
Show AbstractAn experimental study has been performed on the applicability of collision-free theories of the ion current to a Langmuir probe over a wide range in the ratios of the radius of the probe to the Debye screening radius $\xi = R/\lambda_D$, and also over wide ranges in the ion mean free path $\lambda_i$ and in the ratio of the probe length L to the radius of the spacecharge layer s: $(10^{-2}<R/\lambda_D<10^1,10^{-1}<\lambda_i s \le 10^1, 1<L/s\le 10^1)$. For $\lambda_i\ge s$, it is found that for values of $\xi$ satisfying the criterion for distruption of the orbital motion $\frac{\lambda_i}{s}<\frac{\xi}{5\gamma^{1/2}} \eta^{1/2}$ $(\eta=\frac{eV}{kT_e}, \gamma=\frac{T_i}{T_e})$, the ion-current density is close to that calculated from Chen's radial-motion theory; at lower $\xi$, the ion-current density in the orbital-motion mode is dependent on $\lambda_i/s$ and L/s. A close fit to Laframbolse's calculations is to be expected for $\lambda_i/s \gg 10^1$ and $L/s \gg 10^1$.
Show AbstractThis paper discusses saturation of a Raman-scattering transition by biharmonic pumping waves, with probing by coherent anti-Stokes Raman scattering ASRS. It is shown that oscillations in the population difference on this transition at the difference frequency between the pumping and probe waves causes the shape of the homogeneous line for the ASRS signal to contain a characteristic feature: a dip with width determined by the time $T_1$. The results are extended to the case of a Doppler-broadened line. There is a discussion of the scope for coherence spectroscopy free from Doppler broadening.
Show AbstractAn exact solution is found for the transit through resonance in a spin system described by Bloch equations for $T_1=T_2=T$ with a special form for the external fields. It is shown in particular that one can obtain an inversion in the magnetization vector on rapid transit through resonance with comparatively weak HP fields if the nutation frequency for the magnetization vector is equal to twice the frequency of the external-field vector rotation in the rotating coordinate system.
Show AbstractThe paper discusses the interaction of a planar elliptically polarized gravitational wave with the electric field of a particle at rest. The calculation is based on exact allowance for the delay in two cases: in vacuum and in matter whose refractive index is different from one. It Is shown that the interaction produces an electromagnetic wave of finite intensity, but the total intensity of the emission in all directions increases logarithmically with the distance because of the coherent character of the interaction. Allowance for the refractive index of the medium and for other perturbations that disrupt the соherence condition leads to a finite value for the total intensity.
Show AbstractA study has been made of the dynamics of radial cataphoresis in helium-xenon mixtures. It has been found that the settling time for a stationary radial distribution is substantially less than the time of recovery to a radially homogeneous distribution after the end of the current pulse. It has been found that the effective diffusion length for minority atoms Is reduced, and this substantially influences the settling time in radial cataphoresis. A method is described for determining the time dependence of the radial separation in Penning mixtures.
Show AbstractThe strong-coupling approximation for four open channels has been used to calculate the К electron scattering matrix for $Не^+$ and the direct photoionization cross section for helium in the region above threshold. The channel-coupling effects are discussed together with the influence of the He ground-state function on the direct photoionization cross section. The calculations are compared with experiment and with other calculations.
Show AbstractNonlinear capillary-wave interaction in liquids is considered. Some spatial characteristics of the interaction have been established. An expression is derived for the threshold intensity of the parametric decay of the exciting capillary wave.
Show AbstractA study is made of the possible reasons for systematic discrepancies between the cross sections of photonuclear reactions measured with continuous-spectrum $\gamma$ rays CG and quasimonochromatic $\gamma$ rays QMG. It is shown to be necessary to perform a full processing for the published QMG cross sections (which in essence are reaction yields) by analogy with what is done in CG experiments. It is proposed to use a reduction method for this additional treatment of the QMG cross sections that enables one to evaluate the quality of the CG and QMG data clearly and to combine the results from experiments of both types in the reduction scheme. This reduction processing has been carried out. for a series of measured cross sections for photoneutron reactions on $^{12}C$ and $^{18}O$. It has been found that the additional processing of the QMG cross sections leads to much improved agreement with the CG ones.
Show AbstractThe behavior of multilayer dielectric-reflecting systems is considered for angles of incidence of 85-90°, and types of system are identified that provide reflection coefficients close to one with extended reflection spectral ranges.
Show AbstractExperimental results are presented on the macroscopic scales of turbulent pulsations in a vortex model.
Show AbstractGauge models are described in which the vacuum has nontrivial topological characteristics, by analogy with spontaneous symmetry breaking.
Show AbstractThe sink parameter has been determined for an infinite cylindrical probe under conditions where charged particles are generated in the plasma around the probe. It is shown for the spherical probe that if the radius is small by comparison with the ionization length, then the sink parameter is determined by Bohm's expression. Probe operation is considered in the presence of ionization and recombination in the bulk of the plasma.
Show AbstractThe paper discusses the spectrum and major parameters of the magnetostatic waves MSW in a $(1\bar{1}0)$ plate of cubic ferrite ($K_1<0$) having a domain structure DS when the waves have a length greatly exceeding the DS period. A dispersion equation is derived, and results are given from the numerical calculation of the frequencies and group velocities for the case of YIG parameters. The spectrum consists of transverse MSW that are analogs of Damon-Eshbach modes and longitudinal MSW due to the resonant component $\mu_z$ of the magnetic-permeability tensor averaged over the DS. The first may be surface and bulk direct waves or bulk reverse ones. The longitudinal MSW are only direct waves, both surface and bulk types. It is shown that the wave type can be transformed from surface to direct bulk and from direct bulk MSW to reverse.
Show AbstractA method and apparatus are described for calibrating wide-band hydrophones in the megahertz range in ultrasonic beams of finite amplitude. The calibration is based on nonlinear waveform distortion in water as standard medium. The measured parameter is the rate of change of pressure with time on the rectilinear part of the profile. A calibration accuracy of 10% is attained in the range 1-5 MHz.
Show AbstractAn expression is derived for the differential scattering cross sections for atomic particles at an amorphous target. Various interference effects occur, which are dependent on the scattering geometry and particle energy. A study is made of the effects of anisotropy in the thermal vibrations of the surface atoms on the Debye-Waller factor.
Show AbstractA method is described for constructing the X-ray patterns of immobile single crystals and the electron-diffraction pattern of a single crystal of a major phase containing crystallites of a second one. The algorithm has been used in a computer program, which has been tested out in interpreting the structure of the X phase in alloys based on titanium nickelide.
Show AbstractExperimental and theoretical studies have been made on superelastic electron scattering at atoms excited by laser pumping [1,2]. The most detailed studies have been made on electron scattering by sodium atoms excited to the 3P state by a laser: $e+Na^*(3P)\rightarrow e^{\prime}+Na(3S)$ [3]. Here we examine the applicability of the Born distorted-wave approximation BDWA [4,5] in describing this. The channel strong-coupling approximation [6] and the polarized-orbital method [7] have been used previously for a similar purpose. On the basis of the available experimental data and the general constraints imposed on BDWA, we are interested only in small scattering angles. Here we giye calculations for an electron beam energy E = 20 eV.
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