On kinetics of the photodissociation iodine laser

The kinetics of iodine laser amplifiers is examined by solving the time evolution equations of chemical kinetics during optical pumping. The pumping radiation intensity is modelled by a black body of the temperature varying in time (corresponding to the flash lamp pulse). A brief comparison is made of pumping effects by long and short light pulses. Pumping by the long pulse is studied in more detail and it is found that there exists an optimum pulse strength beyond which the inversion in the laser mixture no longer grows appreciably, only its lifetime is shortened. In this connection the effect of pyrolysis of the alkyliodide molecule is also discussed. The pyrolysis is found to occur under very strong illumination, but it does not interfere with the photolytic decomposition and the optimum laser action. Finally, the influence of the reaction rate constants is studied in a systematic way and only few of them are found to carry real weight.The authors are obliged to Drs. S. V. Kuznetsova and A. I. Maslov who were consulted on the values of the reaction constants and who also drew our attention to some of the references.     

Determination of Inorganic Fluorine in High-Purity Silane

A method was proposed for determining inorganic fluorine in high-purity silane. The method is based on the hydrolytic extraction of fluorine as fluorides to the aqueous phase, followed by the analysis of the extract by ion chromatography with a conductometric detector. The detection limit for inorganic fluorine was 1 × 10^–5mass %.     

Synthesis of High-Purity Calcium Hydride

A procedure for synthesizing high-purity calcium hydride in high yield was suggested. The admixture composition of the resulting CaH₂ was determined by laser mass spectrometry.     

Numericalmodeling of vehicle exhaust gas transport and dispersion by an airflow over a city block

The vehicle exhaust gas concentration field in the atmosphere of a city block is described by means of solving the system of Euler’s partial differential equations (those of continuity, motion, energy, and state) with the corresponding boundary conditions. The numerical solution is obtained by Davydov’s large particle method. The numerical experiment made it possible to determine the distributions of the main gasdynamic parameters of the gas-air mixture flow and the distribution of the concentration of carbon monoxide entering in the composition of the exhaust gases throughout a three-dimensional domain of complicated shape.     

On the effect of structural organization on magnetic moment relaxation of disperse particles in a magnetic fluid

The complex susceptibility of a magnetic fluid based on vacuum oil, which is used in engineering as a magnetosealing liquid, is investigated. Features of magnetic moment relaxation of disperse particles, which are associated with their structural organization under the action of external factors, are determined from analysis of the results.     

Hg+Br-->HgBr recombination and collision-induced dissociation dynamics

A global potential energy surface has been constructed for the system HgBr+Ar-->Hg+Br+Ar to determine temperature dependent rate constants for the collision-induced dissociation (CID) and recombination of Hg and Br atoms. The surface was decomposed using a many-body expansion. Accurate two-body potentials for HgBr, HgAr, and ArBr were calculated using coupled cluster theory with single and double excitations and a perturbative treatment of triple excitations [CCSD(T)], as well as the multireference averaged coupled pair functional method. Correlation consistent basis sets were used to extrapolate to the complete basis set limit and corrections were included to account for scalar and spin-orbit relativistic effects, core-valence correlation, and the Lamb shift. The three-body potential was computed with the CCSD(T) method and triple-zeta quality basis sets. Quasiclassical trajectories using the final analytical potential surface were directly carried out on the CID of HgBr by Ar for a large sampling of initial rotational, vibrational, and collision energies. The recombination rate of Hg and Br atoms is a likely first step in mercury depletion events that have been observed in the Arctic troposphere during polar sunrise. The effective second order rate constant for this process was determined in this work from the calculated CID rate as a function of temperature using the principle of detailed balance, which resulted in k(T) = 1.2 x 10(-12) cm(3) molecule(-1) s(-1) at 260 K and 1 bar pressure.     

Basis set limit electronic excitation energies, ionization potentials, and electron affinities for the 3d transition metal atoms: Coupled cluster and multireference methods

Recently developed correlation consistent basis sets for the first row transition metal elements Sc-Zn have been utilized to determine complete basis set (CBS) scalar relativistic electron affinities, ionization potentials, and 4s(2)3d(n-2)-4s(1)d(n-1) electronic excitation energies with single reference coupled cluster methods [CCSD(T), CCSDT, and CCSDTQ] and multireference configuration interaction with three reference spaces: 3d4s, 3d4s4p, and 3d4s4p3d'. The theoretical values calculated with the highest order coupled cluster techniques at the CBS limit, including extrapolations to full configuration interaction, are well within 1 kcal/mol of the corresponding experimental data. For the early transition metal elements (Sc-Mn) the internally contracted multireference averaged coupled pair functional method yielded excellent agreement with experiment; however, the atomic properties for the late transition metals (Mn-Zn) proved to be much more difficult to describe with this level of theory, even with the largest reference function of the present work.     

Excitation of isomeric 1h 11/2 states in nuclear reactions induced by γ rays and neutrons and in beta decay

Isomeric ratios were measured for N=81 isotones (¹³⁵Xe, ¹³⁷Ba, ¹³⁹Ce, ¹⁴¹Nd, ¹⁴³Sm). In the experiment reported here, μ _ν ≤3±10^? J ^π=11/2^? isomers were excited in (n, γ) and (γ, n) reactions and in the β ⁺ decay of ¹³⁹Pr and ¹⁴¹Pm. In order to determine the reaction yields, use was made of the activation method involving measurement of the gamma-ray spectra of reaction products. It is found that, in the same reactions, isomeric ratios are different for isotones characterized by different atomic numbers Z. Isomeric ratios were calculated with the spectra of low-lying levels and radiative-transition probabilities established on the basis of the quasiparticle-phonon model. Good agreement between the experimental and calculated values of isomeric ratios is obtained for all isotopes invesigated here. The dependence of isomeric ratios on the atomic number Z of a nucleus is explained by the difference of reaction energies, which leads to different probabilities of excitation of activation levels through which the isomers being considered are populated.     

Accounting for effects of AZA-substitution on hyperfine interaction constants in ESR spectra

A previously developed scheme for describing the effects of substituents on the physicochemical characteristics of molecules with conjugated bonds has been extended to systems with an open electron shell. The distribution of spin density has been found for a number of anion radicals of azines on the basis of a calculation of their hydrocarbon analogs. The results are in agreement with experimental values of the HFI constant in the ESR spectra of these compounds.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 2, pp. 155–161, March–April, 1989.