We suggest a model that allows analysis of the photoprocesses in polyatomic organic molecules upon multiple IR photon capture. The dissociation and electron excitation of these molecules is shown to depend resonantly on the photon energy and intensity. The (СН$_2$)$_n$ substructures of these molecules serve for IR photons as antennas that accumulate energy to values at which dissociation or electron excitation can be triggered. The model is applied to diphenylalkan molecules as an example.
Show AbstractThe internal and external initial-boundary value problems for 3D equation ${\frac{\partial}{\partial t}(\Delta u-u)-u=0}$ are considered. The problems are posed under the Dirichlet boundary condition on a Lyapunov surface. Using the method of dynamic potentials, the theorems of the unique existence of the solution are proved.
Show AbstractThe thermal instability of discharge plasma in air is analyzed. The contributions of specific mechanisms of instability are examined, including VT relaxation, the increase in the fractional energy dissipation via rapid heating due to an increase in reduced field strength, and ionization thermal instability. The effects of acoustic wave generation caused by heating and of charged particle motion relative to the neutral gas on both the length scale and the growth rate of unstable fluctuations are taken into account.
Show AbstractTime delays between signals emitted by an unknown source are estimated on the basis of the shape analysis of their fragments detected by spatially separated sensors operated under unknown and different conditions [1]. The estimates minimize the maximal error in the time delay of the detected signals with a guaranteed reliability of the estimate [2, 3]. The signal shape is determined as an invariant of the class of transformations modeling the variety of the signal detection conditions.
Show AbstractThe equation of state for a multicomponent hard-sphere system is derived using the method of accelerated convergence of the perturbation series. In the asymptotic limit of small densities, this equation reproduces the virial coefficients known for the systems in question. In the case of a one-component system, the equation transforms into a form that adequately describes both the stable and metastable phases of the substance.
Show AbstractThe possibility of using the RTM-70 race-track microtron for pulsed production of photons and neutrons is analyzed. Optimum parameters of such sources are obtained through a computer simulation.
Show AbstractThe possibility of observing and diagnosing parameters of nanoobjects in a substance by using coherent X-ray radiation arising from the direct interaction of accelerated electrons with the object of interest is discussed. It is analytically shown that analysis of the generated radiation allows the microstructural features of the nanoobject to be studied. To illustrate the main conclusions, coherent radiation generated by relativistic electron scattering on fullerene is considered.
Show AbstractThe fluorescence of nanoparticles of dissolved organic matter under 270-, 310-, and 355-nm excitation is studied for different molecular fractions. The fluorescence quantum yield of the colloidal (molecules of size 5–200 nm) and low-molecular-weight (molecules smaller than 5 nm) fractions are obtained. It is shown that the spectral position of the fluorescence peak depends on both the size of the molecules and the excitation wavelength.
Show AbstractA comparative theoretical analysis of micro engine models that have appeared in recent years is performed. A new model surpassing the considered ones in efficiency and convenience of implementation is proposed.
Show AbstractAn expression for the characteristic function of a nonlocal smooth model potential of an elementary metal is obtained in terms of the full nonlocal theory. The magnesium phonon spectra calculated using the expressions for a characteristic function agree satisfactorily with the experimental data.
Show AbstractNonlinear second-type (matrix) waves are studied with special emphasis on the formation of saw-tooth shock waves. Configurations of the elastic waves in specific cases of porous gas-saturated sedimentary are calculated.
Show AbstractAn original experimental apparatus developed at the Geothermometry Laboratory of the Faculty of Physics of the MSU was used to measure the thermal diffusivity of several mantle minerals over a wide temperature range, extending up to the melting point. Application of the temperature wave method made it possible to account for the radiative heat transfer from the sample surface into ambient space and, thus, to achieve high accuracy in measuring this important thermal characteristic for each substance.
Show AbstractThe amplitude-frequency suppression of correlated non-Gaussian noise at the output of the line channel of resonant gravitational antennas is considered in the case of coherent information processing in the fast filtering mode.
Show AbstractFormulas that include the contribution from dipole-distributed anomalous masses represented as layers distributed in height relative to the reference ellipsoid to the gravitational field in the quadratic approximation have been derived. The relationships between the expansion coefficients of some function and its square in terms of spherical functions have been established. The contribution from the relief masses and the density jump at the Mohorovicic discontinuity is used to illustrate the results.
Show AbstractPion condensation in a flavor-asymmetric quark medium with massive quarks in the external chromomagnetic field is considered. It is shown that the external field catalyzes pion condensation while the finite quark mass does not impede the onset of this phenomenon.
Show Abstract
