R e g u l a r p a p e r s

Moscow University Physics Bulletin 1982. **37**. N 3. P. 1

The family of root trajectories of a fourth-order system with the characteristic equation(a$_0$p$^{4}$+a$_1$p$^3$+a$_2$p$^2$+a$_3$p+a$_4$+K(b$_0$p+b$_1$)=0 is investigated. Having determined the types of root trajectory, their analysis leads to the establishment of general properties, allowing calculations of such systems to be more expediently performed.

Show AbstractMoscow University Physics Bulletin 1982. **37**. N 3. P. 8

In plasma of a helium-xenon discharge, the radical distribution of xenon atoms due to cataphoresis is investigated as a function of the partial pressures of helium and xenon, the discharge current, and the distance from the cathode. The experimental results are compared with theoretical calculation.

Show AbstractMoscow University Physics Bulletin 1982. **37**. N 3. P. 13

The problem considered is the uniqueness of determining a heat source from minimal information on the temperature field outside the region that it occupies, when either or both of the intensity and the region of localization are unknown (in R$_{2}$). The problem is formulated for different stages of development of the source. Theorems for a point source (various cases) and also for a distributed source of uniform intensity with a given localization region are given.

Show AbstractMoscow University Physics Bulletin 1982. **37**. N 3. P. 17

The nature of the changes in absorption spectra of a series of dyes occurring in mixed polar solvents is discussed. The data obtained are interpreted as the appearance of inhomogeneous broadening of the electronic absorption spectra. The relation between the dependence observed and the luminescent characteristics of the investigated materials is demonstrated.

Show AbstractMoscow University Physics Bulletin 1982. **37**. N 3. P. 22

The evolution of the orbits of the components of a triple star system is considered. For the example of the triple system £ Aqu, the importance of determining the sign of the inclination of the orbits of the triple- star components is demonstrated. At certain values of the inclination, the possibility of close approach of internal-pair stars is created periodically over time.

Show AbstractMoscow University Physics Bulletin 1982. **37**. N 3. P. 27

The features of the mechanism of point-defect formation in the nonconservative motion of dislocations with steps under the action of a sign-variable load in alkali-halide crystals is considered. Within the framework of the model, taking account of vacancy emission by steps on spiral dislocations and of vacancy absorption by dislocations, an experimental dependence of the excess vacancy concentration on the amplitude of the mechanical stress at the initial stage of deformation is found.- It is shown that, at the stage of linear strengthening, the excess vacancy concentration must reach saturation.

Show AbstractMoscow University Physics Bulletin 1982. **37**. N 3. P. 32

The appearance in a shock tube of weak shock waves that interact to form a basic shock wave is investigated. It is shown that, in a gas that is under propulsion, both acoustic perturbations (M = 1) and weak shock waves (M = 1.03-1.40) are produced by the propellant. The first arise when a flow of propellant gas passes around the sharp edges of a bursting diaphragm and the second arises in the motion of a region of finite density change behind the front of the second nonsteady shock discontinuity. The Mach machine of the basic shock wave varies from 1.5 to 3.

Show AbstractMoscow University Physics Bulletin 1982. **37**. N 3. P. 39

A theoretical investigation is made into the intensity, spectral composition, and angular distribution of the electromagnetic radiation arising when a plane gravitational wave passes through an electric or magnetic quasistatic field.

Show AbstractMoscow University Physics Bulletin 1982. **37**. N 3. P. 44

The magnetic splitting of a narrow nonlinear resonance in the threelevel system Arǁn4p$^{2}$D${_5/2}$—4S$^{2}$P$_{3/2}$(λ= 488nm), 4$p^{4}$D$_{5/2}$—4s$^{2}$P_{3/2}$ (λ=514,5 nm)is investigated.Saturation of the transition 4$p^{4}$D$_{5/2}$—4s$^{2}$P$_{3/2}$ was created by single-frequency laser radiation at a wavelangth of 488 nm; probing of the system was performed by a sirigle-frequency laser radiation at a wavelength of 514.5 nm, slightly exceeding the self-exictation threshold; the emission frequency was tuned using a Troitskii selector. It is shown that imposing the magnetic field splits the nonlinear resonance into four components: two weak and two strong. The magnitude of the weak-component splitting is(6.8 ± 0.6) MHz/Oe (theoretical estimates of the Zeeman splitting of the transition 4$p^{2}$D$_{5/2}$—4s$^{2}$P$_{3/2}$ gives a value of 7.1MHz/Oe). The strong-component splitting is an order of magnitude less:experimental value (0.8 ± 0.1) MHz/Oe; calculation 0.82 MHz/Oe.Oscillograms illustrating the splitting of the resonance in a magnetic field are presented.

Show AbstractMoscow University Physics Bulletin 1982. **37**. N 3. P. 48

It is shown that the nuclear binding energy may be described with high accuracy when th system of nuclei is divided into regions bounded bymagic (submagic)numbers of neutrons and protons. In each of the intermagic regions, the binding energy is represented by a quadratic function of Z and N. The parameters of the binding-energy formula are determined by minimizing the mean square deviation (σ) of the nuclear masses from the experimental values, taking account of the continuity of the energy surface at the intersection of boundaries of the regions. The formula obtained provides a description with mean square deviation σ =0,11 МeV for nuclei with Z and N ≥ 28; the accuracy is increased with increases in mass number (for heavy nuclei σ = 0.08 MeV).

Show AbstractMoscow University Physics Bulletin 1982. **37**. N 3. P. 54

The "transverse" form factor g⊥(kǁ$^{2}$,k⊥$^{2}$, B) is calculated for arbitrary values of the photon momentum к and the field, under the condition that the external electron lines are at the basic level.

Show AbstractMoscow University Physics Bulletin 1982. **37**. N 3. P. 59

On the basis of experimental data on the reflection coefficients of an inhomogeneous layer corresponding to different values of the load, the inverse problem of finding the distribution of the sample parameters is numerically solved. Examples of the VHP diagnostics of dielectrics with an inhomogeneous distribution of the complex dielectric permittivity are considered.

Show AbstractMoscow University Physics Bulletin 1982. **37**. N 3. P. 64

Methods of direct tensor computation are introduced for the solution of the system of vector equations of the dynamic theory of diffraction for the first time. A covariant representation of the dynamic coefficients is given for the dynamic coefficients for various multipolar Mossbauer transitions in the presence of hyperfine splitting. In the two-wave case, a general solution is given for the scalar interaction and also for an individual Zeeman component of the Mossbauer spectrum. It is shown that, in the latter case, a suppression effect is possible for radiation of any multipolarity. The need to take account of refraction effects is noted in calculating the dynamic coefficients in the limiting asymmetric case of diffraction in the presence of an interaction of tensor type.

Show AbstractMoscow University Physics Bulletin 1982. **37**. N 3. P. 70

A theory of а рarametric receiving antenna is presented first for a quasiplane axisymmetric beam of the reference wave in a medium with losses and then with diffraction of this beam taken into account. The directional chacteristics are obtained, and an analysis of the axial distribution of the parametric signal is performed. Losses lead to "smoothing" of the load structure. Taking account of the characteristic isotropic background noise, the optimal size for the base of the receiving antenna is found; it is larger than the distance at which the amplitude of the parametric signal is a maximum.

Show AbstractB r i e f r e p o r t s

Moscow University Physics Bulletin 1982. **37**. N 3. P. 75

By the methoi of electron microscopy and electron diffraction, the structure of the alloy Fe - 20 at. % Ru after quenching from 900°C is determined. It is shown that the alloy consists of alternating thin layers of the matrix and e martensite. Such a morphology of a twophase alloy leads to the expansion of points of the inverse lattice and, consequently, to the appearance of extra reflexes and also reflexes from double diffraction, resembling diffraction from a modulated structure, on the electron-microscope traces.

Show AbstractMoscow University Physics Bulletin 1982. **37**. N 3. P. 78

Results are given of an experimental investigation of the structure of the flow arising with wind impulsion in a homogeneous liquid above a slope, in conditions modeling the coastal shelf of a sea.

Show AbstractMoscow University Physics Bulletin 1982. **37**. N 3. P. 82

In conditions of frequency tuning of the exciting radiation, the energy threshold, and spectral characteristics of the infrared induced three-photon scattering (IR ITPS) of light in rubidium vapor are investigated. It is established that induced cascade transition arising as a result of multiphoton ionization of the atoms has a significant influence on the occurrence of this process. The features of IR ITPS excitation are investigated for the case where the conditions of both two-photonn (5${^2}$S$_{1/2}$—5$^{2}$D$_{5/2}$) and single-photon(5${^2}$S$_{1/2}$ — 5$^{2}$ P$_{3/2}$)resonance are simultaneously satisfied. It is observed that, on approaching the single-photon resonance,the reduction in excitation threshold and icrease in energy of the scattered radiation that is expected from theory is not observed, but instead the completely opposite picture; the excitation threshold rises and the energy decreases.This contradiction between theory and experiment is explained.

Show AbstractMoscow University Physics Bulletin 1982. **37**. N 3. P. 85

Results are presented of natural investigations of the total heat flux and effective long-range radiation of the surface of the sea during expeditions in 1977-1979 to the open sea. Prom the data of recordings made over many days and synchronously, curves of the daily trend of the heat-flux components from the sea into the atmosphere are plotted.

Show AbstractMoscow University Physics Bulletin 1982. **37**. N 3. P. 88

For a two-conductor line, the four-point correlator of the potential and current is calculated. Two cases are considered: nonlinear conduction of the directing conductors; and a "linear" line loaded by a nonlinear resistance. The correlator is calculated using cubic relations of nonlinear fluctuational-dissipative thermodynamics. The indeterminacy remaining after the phenomenological equations are specified reduces to the presence of a single numerical parameter that is dissipationallу undetermined.

Show AbstractMoscow University Physics Bulletin 1982. **37**. N 3. P. 92

For the longitudinal dielectric permittivity of relativistic plasma in the long-wave region, a representation in the form of a uniformly converging series is obtained; this representation is valid over a broad range of temperatures and wave vectors. If the temperature is not too small in the long-wave region, this series converges rapidly, ensuring high accuracy of the representation when only the first few terms of the series are used.

Show AbstractMoscow University Physics Bulletin 1982. **37**. N 3. P. 95

The optimal directions of linear longitudinal and transverse electrooptical effects are determined for crystals of classes mm2 and 4mm. The minimal halfwave potentials are given for NaBa$_2$ Nb$_5$O$_15$ and Ba$_0,25$ Sr$_0,75$ NB$_2$ O$_6$.

Show AbstractMoscow University Physics Bulletin 1982. **37**. N 3. P. 99

Adaptive optical systems are used to ensure maximum angular resolution of telescopes in observing remote objects through a turbulent atmosphere, and also for focusing radiation onto remote objects in a nonlinear and turbulent medium. The potential of additive systems is largely determined by the type of corrector used and its parameters: the band of working frequencies and the sensitivity. The parameters of correcting mirrors are expediently measured by interferometric methods.

Show AbstractMoscow University Physics Bulletin 1982. **37**. N 3. P. 102

The angular dependence of the intensity of fluxes of molecular and atomic nitrogen ions forcing in the reflecting of accelerated molecular nitrogen ions of energy 30 keV from the surface of polycrystalline copper is investigated. It is shown that the difference between the angular distributions of the molecular and atomic ions may be explained by the dependence of the degree of dissociation of the molecules on the scattering angle.

Show AbstractMoscow University Physics Bulletin 1982. **37**. N 3. P. 106

Moscow University Physics Bulletin 1982. **37**. N 3. P. 109

On the basis of taking into account the interaction between a photon and a complex electromagnetic field consisting of a combination of the field of a wave and a homogeneous magnetic field, the process of e$^{-}$ e$^{+}$ pair formation is investigated. The case of the two-photon formation of an electron-positron pair with the propagation of photons in opposite directions in an external magnetic field H is analyzed In detail. A correction is obtained to the Breit-Uiler cross section in the limit H ≪H$_10$ ~ 10 $^{13}$ G. It is shown that the magnitude of this correction depends significantly on the energy of the interacting photons and changes sign at an energy h$_ω$ ~ 1,33 mc$^{2}$.

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