On the n = 1 exciton line of the green series in Cu2O

The weak isotropic line λ = 5830 Å observed on the wing of the yellow 2p-exciton line in Cu₂O is usually ascribed to the 1s(Γ⁺₄)-exciton of the green series. It is shown that if this is correct, then the stronger anisotropic line associated with the 1s(Γ⁺₅)-exciton of the green series should be nearly observed.     

Raman spectroscopy of infrared multiple-photon excited molecules

The method of spectroscopy of spontaneous Raman scattering (RS) with time resolution has been applied for the first time to diagnose the process of multiphoton ir molecular excitation (MPE). Some aspects of RS diagnostics of MPE processes are being analyzed. It has been shown experimentally on SF₆ and CF₃I molecules that it is possible to study such important characteristics of excitation process as the fraction of molecules involved in the process of excitation, vibrational energy distribution of molecules, stochastization of inner molecular energy.     

Interlaboratory comparisons between results from testing metallurgical products for precious metal content

Problems verifying the accuracy of analyses of non-standardized materials for precious metal (PM) content have arisen at the Norilsky Nickel plant, which is a major producer of nickel, copper, and PMs in Russia. Because of the unavailability of certified reference samples for direct accuracy verification, a program of interlaboratory comparisons (ILC) was developed. This program was based on testing three semi-products of the PM production process for PM content. On program completion, a total of 826 results in 98 runs had been obtained. For each run, the calculated mean value of PM concentration was taken to be the reference value. The results obtained by Norilsky Nickel were in agreement with the reference values within the standard deviations calculated for the values. The quality of results yielded with the ILC program, as assessed via the Z-criterion, is regarded as satisfactory.Presented at the Second International Conference on Metrology – Trends and Applications in Calibration and Testing Laboratories, November 4–6, 2003, Eilat, Israel.     

The permittivity of a monatomic gas with spatial dispersion

The longitudinal, ε^l(ω, k), and transverse, ε^tr(ω, k), permittivities of a monatomic gas were calculated. The frequency ranges in which the permittivity ε(ω) and permeability μ(ω) of a gas without spatial dispersion have a physical meaning were determined. The limiting magnetic susceptibility χ(ω) at ω=0 and the static magnetic susceptibility were found. The question of whether an electromagnetic wave with antiparallel group and phase velocities can propagate through a monatomic gas is discussed.     

The “SKATE” CO2 Gigawatt Laser for a Laser-Plasma Generator of Ions and Nuclei

A set-up of the CO₂ SKATE and its output characteristics are described. The system is based on a self-sustained gas discharge module with x-ray preionization that ensures reliability and stable repetition rate operation at 1 Hz for a long time. Measurement of the initial electron density in the discharge volume produced by an x-ray gun is presented for different gases and their mixtures, which is of independent interest for some applications of x-ray preionization. Data on measurements of the low-intensity signal gain and laser parameters for a free-running generator configuration are presented as well as long-term operation characteristics. This laser system has been used as a CO₂ generator with gigawatt peak intensity and high spatial–temporal characteristics. In particular, the laser can be used as a driver for a source of multicharged ions in contrast to the laboratory prototypes previously investigated.     

On asymptotics of the uniform norm of polynomials with zeros at the roots of unity

The work is related to the problem by P. Erds about the estimation of the numbers

FD-Method: the Exponential Rate of Convergence

In this article, we describe a functional–discrete method (FD>-method) for solving operator equations and abstract eigenvalue problems. The algorithm of the method includes a recurrent solution of a sequence of problems with a fixed operator, which is simpler than the initial one, and a changing right-hand side. We prove that, with fairly general assumptions, the FD-method converges with the rate of a geometric progression, i.e., has exponential convergence rate.     

Ray escape from a range-dependent underwater sound channel

The problem of sound propagation in a spatially inhomogeneous underwater sound channel is considered. The effect of ray escape, i.e., the ray incidence on the absorbing bottom due to the chaotic swing of rays, is studied. With the use of the Poincaré map and maps of escape, the relation of ray escape to the properties of the phase space of the set of ray equations is demonstrated. It is found that the maximum escape occurs under the vertical resonance conditions, i.e., at the resonance of the ray oscillations in the waveguide with the vertical oscillations of the sound velocity perturbation. A qualitative theory of the vertical resonance is developed. It is shown that the ray escape considerably shortens the time spreading of the signal.     

Growth of Pt thin films on WSe2

The morphology and structure of Pt deposited on a WSe₂(0 0 0 1) van der Waals surface have been investigated by reflection high energy electron diffraction and scanning tunneling microscopy. At room temperature, the initial growth is characterized by the formation of three-dimensional fcc Pt islands with (1 1 1) orientation. In contrast, at higher temperatures of about 450 °C the formation of a novel chemically ordered Pt-Se alloy is observed. Based on the diffraction patterns, a tetragonal DO₂₂-type structure of a Pt₃Se compound is suggested. With increasing Pt thickness, this chemically ordered alloy disappears and an additional superstructure occurs, which is accompanied by the coalescence of the islands. The observed superstructure is attributed to a strong Se diffusion towards the growth surface, forming most likely a PtSe₂ alloy with the CdI₂-type layered structure on the top surface. Due to the lateral lattice mismatch between the Pt(1 1 1) layers and the PtSe₂(1 1 1) top layer, a Moiré pattern with a period of 1.1 nm is created, which might be used as a long-range atomic pattern for further nanostructure growth.