Structure, interaction potentials, and vibrational spectra of the sulfite ion coordinated to alkaline element ions

Potential surface sections in the complexes of SO ₃ ^2- with Li⁺ and Na⁺ are calculated by the CNDO method with a modified potential of interaction between the cores. It is established that the equilibrium geometry of the coordinated sulfite ion corresponds to the bidentate coordination of the onion to the Li₊ and Na⁺ cations. Frequencies of normal vibrations are determined for four types of anion coordination to cations and compared with the experimental frequencies in aqueous sodium sulfite. The bidentate coordination gives the best correspondence with the experimental spectrum. Translated from Zhurnal Struktumoi Khimii, Vol. 38, No. 2, pp. 282–286, March–April, 1997.     

Synthesis of heterocyclic analogs of isoflavone and homoisoflavone based on 3-formylchromone

The review is focused on recent developments of chemistry of synthetic analogs of natural compounds, isoflavone and homoisoflavone. The possible synthetic strategies to access heterocyclic analogs of these compounds starting from readily available 3-formylchromone and its derivatives (3-cyanochromone, 2-amino-3-formylchromone) and products of its condensation with simplest C- and N-nucleophiles are discussed. The structural features of the reaction products that depend on the nature of the reaction medium, structure of the starting compounds, and reagent ratio are considered. Particular attention is given to the application of the modern strategies of organic synthesis, namely green chemistry approaches, click reactions, domino reactions, etc. Examples of compounds of this group most promising for clinical application due to wide and pronounced pharmacological effects are given.

     

Hydrogen gas sensitivity of thin films of tin oxide surface doped by platinum laser plasma of different structure and charge composition

The effect of structure and charge composition of Pt laser plasma in the surface doping of SnO₂ thin films on their resistive gas sensitivity towards hydrogen has been studied. The structure and charge composition of plasma varied depending on the value and polarity of the potential (U _D ) of the inhomogeneous electrostatic field generated between a target and plates of a diaphragm located in a vacuum chamber outside the plasma dispersion zone under the action of Kr-F laser radiation on a platinum target. Doping at U _D > 0 results in an increase in gas sensitivity of SnO₂ films several times greater than doping by quasineutral plasma (U _D = 0). The films doped at U _D < 0 with surface concentrations of Pt optimum in terms of the maximum gas sensitivity appear to tolerant towards changes in the composition of the gas phase in a temperature range of 50–600°C.     

Intensity correlation function of field backscattered by two isotropic atoms

It is shown that the temporal intensity correlation function of laser light backscattered by two isotropic atoms displays the photon antibunching property in a helicity-conserving polarization channel. A simple qualitative explanation to this effect is given, results of numerical calculations that support the qualitative analysis are presented, and possibilities of the experimental observation of this effect are discussed.     

Deuteron flux production in a small high-voltage high-current diode with pulsed magnetic insulation

Technical Physics - The results of new studies on the production of accelerated deuteron fluxes in a small ion diode with pulsed magnetic insulation of electrons have been presented. A plasma anode...     

Resonance fluorescence of a two-level atom excited by a superposition of coherent states, and the instability of the average atomic dipole moment

We find the evolution of average atomic variables in the resonance fluorescence of a two-level atom excited by a superposition of coherent states shifted in phase by π. A new effect is predicted, the quantum instability of the average atomic dipole moment, with a strong correlation between atom and field being the reason. We propose different ways of verifying the effect in experiments involving high-Q optical and microwave cavities. Zh. éksp. Teor. Fiz. 111, 1174–1189 (April 1997)     

Generation of nanosecond neutron pulses in vacuum accelerating tubes

The generation of neutron pulses with a duration of 1–100 ns using small vacuum accelerating tubes is considered. Two physical models of acceleration of short deuteron bunches in pulse neutron generators are described. The dependences of an instantaneous neutron flux in accelerating tubes on the parameters of pulse neutron generators are obtained using computer simulation. The results of experimental investigation of short-pulse neutron generators based on the accelerating tube with a vacuum-arc deuteron source, connected in the circuit with a discharge peaker, and an accelerating tube with a laser deuteron source, connected according to the Arkad’ev-Marx circuit, are given. In the experiments, the neutron yield per pulse reached 107 for a pulse duration of 10–100 ns. The resultant experimental data are in satisfactory agreement with the results of computer simulation.