Special features of the dynamics of multipole moments of atoms at rest in weak light fields

The dynamics of radiative relaxation of multipole moments of atoms at rest in the ground state is considered for a low degree of dipole transition saturation. Using the field representation in the bipolar harmonic basis, the special features of the characteristic relaxation times are studied as functions of the j_g j_e transition type, ellipticity, and field frequency offset from resonance.__________Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 57–64, December, 2004.     

Necessity of dark matter in modified Newtonian dynamics within galactic scales

To test modified Newtonian dynamics (MOND) on galactic scales, we study six strong gravitational lensing early-type galaxies from the CASTLES sample. Comparing the total mass (from lensing) with the stellar mass content (from a comparison of photometry and stellar population synthesis), we conclude that strong gravitational lensing on galactic scales requires a significant amount of dark matter, even within MOND. On such scales a 2 eV neutrino cannot explain the excess of matter in contrast with recent claims to explain the lensing data of the bullet cluster. The presence of dark matter is detected in regions with a higher acceleration than the characteristic MOND scale of approximately 10(-10) m/s(2). This is a serious challenge to MOND unless lensing is qualitatively different [possibly to be developed within a covariant, such as Tensor-Vector-Scalar (TeVeS), theory].     

Special features of electron beam-excited XeCl-laser generation

The results of experimental investigations on generation in Ar(Ne): Xe: CCl₄(HCl) mixtures at excitation by an electron beam are given. It is shown that the use of CCl₄ and HCl with an Ar buffer gas gives equal radiative energies and efficiencies and ā change of Ne for Ar causes a change in generation spectrum. The special features of XeCl-laser generation are discussed.     

Special features of thermal evaporation of rare-earth metals

The process of thermal evaporation of rare-earth metals (Ce-Yb) with an incomplete 4f-shell is discussed in terms of electronic structure of their surface. Evaluation of the surface density of neutral intrinsic atoms determining the evaporation process is made. The fact of detachment of Sm atoms in the lowest excited 4f⁵5d6s²-state from the surface is experimentally demonstrated. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 43–47, June, 2006.     

Special features of ethylene epoxidation by peroxyacetic acid

The B3LYP/6-31G(d, p) method of density functional theory was used to study the influence of carboxylic acid and water molecules on parallel ethylene oxidation reactions (epoxidation and hydroxylation) by peroxyacetic acid with the formation of various products. It was shown that carboxylic acid in the nondissociated form always present in the reaction mixture for several reasons had a catalytic action on this reaction and therefore contributed to an increase in its selectivity. We also found that the water molecule and its dimer facilitated epoxide formation. The suggestion was made that, if the reaction was performed in an aqueous medium, where the acid dissociated, the situation could radically change, and the hydroxylation reaction with the formation of glycol and/or its ester of the corresponding carboxylic acid would become predominant.     

Black-hole production at LHC: Special features,problems, and expectations

A brief survey of the present-day status of the problem of multidimensional-black-hole production at accelerators according to models featuring large extra dimensions is given. The respective production cross section and the Hawking temperature and decay rate are estimated versus model parameters. Possible flaws and assumptions whose accurate inclusion can reduce significantly the probability of blackhole production at accelerators in relation to earlier optimistic estimates are also discussed.     

Special features of magnetic susceptibility dispersion in nanocrystalline magnets

It is demonstrated theoretically that the initial (both elastic and viscous) magnetic susceptibility components for nanocrystalline magnets caused by the processes of rotations (in the region of linear response) have resonant rather than relaxation character typical already for the susceptibility component caused by displacements of domain boundaries. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 88–92, June, 2007.     

Special features of local spatial spectrum of Bessel light beams

In this paper we consider the angular spectrum of an apertured Bessel beam when the aperture is circular and shifted laterally with respect to the optical axis. Since the perturbation of the resulting angular spectrum is due to a spatially localized Bessel field, we refer to such an angular spectrum as the local spatial spectrum. We show that the local spatial spectrum of the Bessel beam may differ considerably from the angular spectrum of an unapertured Bessel beam, and find that the ring-shaped angular spectrum is converted into two arcs whose width in the azimuthal direction monotonically decreases as the shift of the circular aperture increases. This phenomenon is predicted theoretically and confirmed experimentally.     

Special temperature features of the birefringence of lithium tetraborate crystals

Using the Senarmont polarimetric method, the optical birefringence of lithium tetraborate crystals Li₂B₄O₇ in the 290–480 K range was measured. The steplike temperature dependence of birefringence, the thermal hysteresis, and the thermooptic memory effect were observed, which are most likely associated with the presence of incommensurate phase modulation in lithium tetraborate.     

Special features of the ferromagnetic resonance in cobalt-containing granulated nanostructures

Results of studying the concentration and orientation spectra of ferromagnetic resonance (FMR) in nanogranulated composites consisting of amorphous cobalt-containing granules in the SiO ₂ or Al2O ₃ amorphous dielectric or LiNbO ₃ ferroelectric matrix are presented. It is demonstrated that the magnetic and structural changes of the nanocomposites attendant to changes in the metal phase concentration can be described using the FMR spectra. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 47–53, March, 2006.     

Special features in photoemission from the s-p bands of copper

Angle-resolved photoemission (ARPES) studies of the (100) face of clean copper using He I radiation reveal two distinct peaks with binding energies between 0 and 2 eV. These peaks have the opposite dispersion with emission angle and have very different widths, one peak in particular being unusually sharp. We show that both of these peaks are associated with the upper part of the s-p band and that their behaviour can be qualitatively explained by an examination of the bulk band structure for finite values of k_∥ away from the Δ-symmetry direction. We also show that rather good quantitative agreement with the experimental spectra can be obtained by performing realistic photocurrent calculations which include a proper treatment of the surface electronic structure, matrix elements and lifetime effects. Finally, the significance of a sharp peak arising from the s-p band for ARPES studies of random alloys and chemisorption systems is briefly discussed.     

Mode interaction and dynamics features of class d lasers

We study a simple model of the class D laser with allowance for the spectral and spatial inhomogeneity of an active medium, whose polarization relaxation rate is much smaller than the field relaxation rate in a resonator. We consider the cases of one-, two-, and four-mode lasing for which the stationary, pulsed, self-modulation, and quasi-chaotic of laser dynamics are numerically studied. The laser parameters are chosen to correspond to the experiments on the Bose–Einstein condensation of dipolar excitons in semiconductor traps with quantum wells, which open up a possibility for creating class D lasers for the first time.     

Lattice dynamics and melting features of Li and Na

The high-pressure melting of Li and Na has been studied using ab initio calculations of the lattice dynamics. It has been shown that the recently discovered anomalous melting of Na is adequately explained by the phonon spectrum behavior and, accordingly, the thermal vibration amplitudes under compression. In a simple approach using the Lindemann criterion, the nonmonotonic behavior of the melting curve T _m(p) of Na has been quantitatively described within very wide pressure and temperature ranges, and, in particular, the melting temperature drop at p ～ 1 Mbar down to values lower than those at normal pressure. This approach leads to a nonphysical discontinuity of the melting curve T _m(p) of Li near the bcc-fcc-liquid triple point. This is due to the “softness” of the phonon spectrum of the bcc phase of Li that is the necessary condition for the existence of the high-temperature bcc phase. The melting of Na and Li is used as an example to determine why the Lindemann criterion is efficient in some situations and is inapplicable in the other cases.     

Uncovering the features of spin dynamics in hadronic physics

We summarize the program pursued by Michael J. Moravcsik and the authors on spin amplitude analyses and interpretation. We present the recent observations that phase histograms reveal striking peaks corresponding to spin amplitudes that tend to have definite simple phase relations. An interpretation is proposed in which the spin amplitudes receive a coherent and an incoherent contribution over large ranges of energies and angles. Continuing research directions are reported.Dedicated to the memory of Michael J. Moravcsik, whose contribution to this work, our research, and spin physics is immeasurable     

New features in collective dynamics of intrinsic Josephson junctions

We discuss the breakpoint phenomenon, which reflects a resonance between Josephson and plasma oscillations in the system of coupled Josephson junctions. The resonance leads to the creation of the longitudinal plasma waves (LPW) at the breakpoint and to the oscillation dependence of the breakpoint current as a function of the dissipation and coupling parameters. A group behavior of the current-voltage characteristics (IVC) of the stacks with different number of junctions is predicted. Particularly, in the materials with dissipation parameter β=0.35 and coupling parameter α=3, we expect four groups of the IVC, which demonstrate a different character of changing of the breakpoint current with the number of junctions in the stack. Using the k-αβ-method, we find the values of the wave numbers k of the LPW and explain this group behavior of the IVC.     

Special features of recording IR spectra of MFTIR of fibrous materials

We investigated the influence exerted by the conditions of preparation of specimens of fibrous materials made of polyethylene terephthalate and triacetate threads and fabrics and the conditions of recording IR spectra of modified frustrated total internal reflection (MFTIR) on the reproducibility of spectral characteristics. We found that the area of actual contact of fibrous meterials with a reflecting prism and the reproducibility of spectral characteristics can be considerably increased by applying preliminary pressing and increasing the pressure of clamping the materials to the prism. We determined the optimum values of the parameters for preparing specimens and recording MFTIR spectra that make it possible to carry out, with sufficient accuracy, spectrophotometering of fibrous specimens made of polyethylene terephthalate and triacetate fabrics and threads. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 103–107, January–February, 1997.     

Special features of absorption of electromagnetic radiation by a cylindrical particle

The cross section of electromagnetic radiation absorption by a cylindrical metal particle was calculated. No limitations were imposed on the relation between the electron mean free path and the particle size. Specific absorption cross sections of cylindrical and spherical particles are compared. The results of the numerical calculation are presented graphically.