An impact mechanism in diverting energy from absorbing inclusions at laser destruction of transparent dielectrics

A new mechanism of destruction of transparent dielectrics with small highly-absorbing inclusions by using intensive laser emission has been suggested. It has been shown that for experimentally found values of threshold radiation intensity I_th ≈ 1 GW/cm² and impurity concentration n ? 10⁷ cm^-3 radiation absorption outside the front of the impurity-initiated shock wave, when allowing for the collective action of waves, results in great heating of the dielectric surface layer which causes its destruction. The found critical value of impurity concentration is several orders less than the value estimated over a model of heating of an inclusion-surrounding dielectric at the expense of heat conductivity.     

Catalytic olefination. Estimation of the reactivity of polyhaloalkanes

Global electrophilicity indices and carbon-halogen bond energies of a wide series of halogen derivatives were calculated in terms of the density functional theory (DFT). The calculated values were used to estimate the reactivity of halogen derivatives under conditions of catalytic olefination. Reactions of N-unsubstituted hydrazones with polyhaloalkanes in the presence of CuCl afforded substituted alkenes. The relation between the structure of polyhaloalkanes and their reactivity was studied using the reaction with 4-chlorobenzaldehyde hydrazone as an example. It was found that increase in the global electrophilicity index and decrease in the C-Hlg bond energy are accompanied by increase in the olefinating power of halogen derivatives.Dedicated to Full Member of the Russian Academy of Sciences A.I. Konovalov on His 70th Anniversary__________Translated from Zhurnal Organicheskoi Khimii, Vol. 40, No. 12, 2004, pp. 1801–1807.Original Russian Text Copyright © 2004 by Nenaidenko, Korotchenko, Shastin, Tyurin, Balenkova.     

Arc atomic emission determination of noble metals in mineral raw materials and products of their processing

A procedure has been developed for the direct atomic emission determination of medium concentrations of noble metals in mineral raw materials and products of their processing. The procedure is based on the application of a spectral complex, consisting of an arc source of spectrum excitation, a DFS-8 spectrograph, a receiver of spectrum emission with CCD structures, and a registration system including software. The detection limits are n × 10^?5% for a number of noble metals and n × 10^?7% for Ag with RSD of 7?C14%.     

Features of the ionization mechanism of radical recombination luminescence excitation

A comparison of the temperature-time cycles of radical recombination luminescence (RRL) in atomic hydrogen, based on ZnS and ZnCdS at different partial pressures, is presented. The obtained results allow us to explain the temperature dependences of chemisorption of the charged form of N ⁺ and the optical transition rate upon RRL.     

Rotational mobility of Aerosil surface grafted ≡ SiNNO<Superscript>•</Superscript> radicals with and without adsorbate at 77 K

The rotational mobility of Aerosil surface grafted ≡ SiNNO^? radicals without adsorbate and in adsorbed carbon dioxide or sulfur hexafluoride layers was estimated at 77 K as (4–5) × 10⁷ s^?1.     

Dynamics of hydrogen accumulation and radiation-stimulated release from steels

Hydrogen accumulation during electrolytic saturation of 12Kh18N10T and 12Kh12M1BFR steels, as well as during thermally and radiation-stimulated hydrogen release from the same materials, was studied. It was shown that there is a critical hydrogen concentration in the sample, which is reached in 50 h for this saturation method (1 M H₂SO₄ electrolyte, current density is 0.5 A/cm²). Initially, hydrogen is trapped at low-temperature (400–500°C) traps of several types in surface layers. At saturation times of 50 h and longer, hydrogen penetrates to high-temperature (800–900°C) traps in the sample bulk. Under electron irradiation of saturated samples, the hydrogen yield nonlinearly increases with electron current density and energy above 40 keV. It was concluded that electronic processes (Auger process and plasmon excitation) play a dominant role in hydrogen diffusion and desorption activation.