Vol 62, No 3 (2017)

In a magneto-optical trap (MOT) of ⁷Li, two-photon Rydberg resonances are recorded by using a spectroscopic technique, which based on variation in the resonance fluorescence. The first excitation frequency is detuned by 0.59 GHz from the intermediate 2P_3/2 state. Two counter-propagating laser beams are used. The resonances are studied on two-photon transitions 2S_1/2 − nl in a range of principal quantum number n from 38 to 120. The widths of the observed resonances are varied from 4.4 to 13 MHz for different MOT parameters.

The problem on dispersive distortions of an electromagnetic pulse in a gaseous medium with two isolated resonant frequencies is solved analytically. The solution is obtained directly in the time region and, thus, is not the result of calculations of the Fourier integral. Without introducing additional assumptions, it is possible to study the regularities and the features of the process of propagation of pulses caused by variations of both their initial characteristics and the parameters of the propagation medium. As an example, the solution is applied to describe the distortions of the two-frequency pulse of subnanosecond duration in the terrestrial atmosphere.

A theoretical description of the plastic deformation of metal–graphene nanocomposites through stress-induced migration of grain boundaries is proposed. Within the micromechanical approach developed, the plastic deformation induced by this migration leads to the formation of disclination quadrupoles (intense elastic stress sources). The energy characteristics and critical stress are calculated for the plastic deformation mode under consideration. The influence of graphene nanoinclusions is shown to cause significant hardening of metal–graphene nanocomposites. This conclusion is consistent with the corresponding experimental data.

In the solution of many problems of mechanics and mathematical physics, there is the necessity of operating with complicated (“unbearable”) elliptic integrals of the 1st, 2nd, and 3rd kinds, in the calculation of particular values of which various programs and special tables are now used. However, the use of tables is associated with the necessity of the cross interpolation of tabular data, difficulties in programming, and the restricted scope of their application. In addition it is shown that certain tables give an inadmissibly large underestimate of the results (up to 60−80%).

The method of particle dynamics is used for both analytical and numerical investigation of tensor properties of the Mie–Grüneisen equation of state for two-dimensional solids with crystalline structure. It is demonstrated analytically that the Grüneisen function essentially depends on the ratio between the eigenvalues of the deformation temperature tensor, which, in this work, is determined numerically.

The kinetic Boltzmann equation has been solved for the boundary-value problem of heat transfer with boundary conditions in the form of nonequilibrium distributions. Modes with anomalous heat transfer have been revealed in the spatial zones where the signs of the heat flux and temperature gradient coincide (in the classical statement of the problem with equilibrium conditions, heat transfer conventionally occurs in the entire range of physical parameters). Possible experiments aimed at verifying these effects are discussed.

An exponential smallness of the errors in the one-dimensional model of the Stokes flow in a branching thin vessel with rigid walls is achieved by introducing effective lengths of the one-dimensional image of internodal fragments of vessels. Such lengths are eluated through the pressure–drop matrix at each node describing the boundary-layer phenomenon. The medical interpretation and the accessible generalizations of the result, in particular, for the Navier–Stokes equations are presented.