Vol 105, No 10 (2017)

Different interpretations of narrow structures at W ~ 1.68 and 1.72 GeV observed in several reactions are discussed. It is questionable whether interference phenomena could explain the whole complex of experimental findings. More probable hypotheses would be the existence of one or two narrow resonances N(1685) and N(1726) and/or the sub-threshold virtual KΣ and ωp production (cusps).

A modified-gravity theory with a four-form field strength F, a variable gravitational coupling parameter G(F), and a standard matter action are considered here. Maxwell and Einstein equations are now derived when including to action also derivates of F. The energy momentum tensor of the 4-form field contains both the part, which is typical for the fundamental (pseudo)scalar, and the part, which cancels the divergent contribution of the zero-point energies of quantum fields to the vacuum energy and thus leads to the natural nullification of the cosmological constant in Minkowski vacuum.

The possibility of the formation of a plasma–dust cloud in the exosphere of the Moon owing to impacts of meteoroids on the lunar surface is discussed. Attention is focused on dust particles at large altitudes of ~10–100 km at which measurements were performed within the NASA LADEE mission. It has been shown that a melted material ejected from the lunar surface owing to the impacts of meteoroids plays an important role in the formation of the plasma–dust cloud. Drops of the melted material acquire velocities in the range between the first and second cosmic velocities for the Moon and can undergo finite motion around it. Rising over the lunar surface, liquid drops are solidified and acquire electric charges, in particular, owing to their interaction with electrons and ions of the solar wind, as well as with solar radiation. It has been shown that the number density of dust particles in the plasma–dust cloud present in the exosphere of the Moon is ≲10⁻⁸ cm⁻³, which is in agreement with the LADEE measurements.

Miniature analogs of starters and blue jets that are observed in the upper atmosphere of the Earth and have dimensions of tens of kilometers are formed and studied in air and nitrogen at pressures of tens and hundreds of Torr. Ministarters and mini blue jets have been obtained in laboratory experiments owing to the application of a pulse-periodic discharge with a plasma jet referred to as apokamp. The velocities of propagation of apokamps have been measured at various pressures. It has been found that the average values of these velocities are about the velocities of propagation of starters and blue jets in the atmosphere of the Earth. It has been shown that jets (apokamps) with the maximum length are observed in the pressure range corresponding to the altitudes of appearance and propagation of starters and blue jets.

The transport of traps in a dielectric after capture of holes in an electric field is considered with the inclusion of the two-band conduction. The distance covered by a trap with a trapped hole decreases exponentially with an increase in the electric field. A value of 3 × 10^–15 cm²/(V s) has been determined for the mobility of traps with trapped holes in Si₃N₄.

The transmission and luminescence spectra of a cholesteric photonic crystal doped with an organic dye are measured. The density of photon states is calculated using the material parameters obtained from the comparison of the experimental and theoretical spectra. The shape of the luminescence spectra is modified with respect to the density of photon states owing to the difference in the structure of the normal modes of the photonic crystal near the short-wavelength and long-wavelength edges of the photonic quasi-band gap upon the “pushing” of the photon states from the gap and to the nonvanishing orientation ordering of the luminescent molecules. The luminescence spectrum calculated taking into account the chiral structure of the photonic crystal agrees with the experimental spectrum.

Atomic metallic hydrogen, which has a lattice with the FDDD unit cell symmetry, has been shown to be a stable phase at a hydrostatic pressure of 350–500 GPa. The found structure has a phonon spectrum which is stable with respect to decay. The structural, electronic, phonon, etc., characteristics of normal metallic phases of hydrogen at a pressure of 350–500 GPa have been ab initio calculated.

The dependence of the enhancement of the Raman scattering on the size of a dielectric column is measured in structures with the spatial modulation of the height and lateral sizes of the dielectric coated with a thick metal layer (10–80 nm). It is established that, in the case of a thick metal coating (silver, gold, and copper coatings are used) at dimensions of the dielectric column close to the laser pump wavelength, considerable enhancement of the Raman signal oscillating upon the variation of the geometrical dimensions of the structure is observed. It is shown that the observed resonance enhancement of the Raman signal is associated with the transformation of the electromagnetic radiation into localized plasmon–polariton modes, and the efficiency of such transformation is determined by the commensurability of the wavelength of the plasmon–polariton mode and the planar size of the metal film. For different metal coatings, the dependence of the enhancement of the Raman scattering on the laser wavelength is measured.

The evolution of probabilities of escape of hot and thermalized electrons from GaAs(001) with adsorbed cesium and oxygen layers to vacuum at the transition from positive to negative effective electron affinity is studied by the photoemission quantum yield spectroscopy. A minimum of the probability of escape of thermalized electrons near zero electron affinity is revealed and explained.