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.     

Electrical properties of some crystalline salts of adenine

In the present paper we report the first experimental results on ac and dc conductivity and permittivity of adenine hemisulphate hydrate and adenine sulphate measured at atmospheric and high hydrostatic pressures. For both materials ac conductivity is of ^s type, where:s 1·1· Room temperature dc conductivity of adenine hemisulphate hydrate equals approximately 5×10^{–15 –1} cm^–1 with an activation energy of 0·86 eV; dc conductivity of adenine sulphate is less than 10^–16 cm^–1. On the basis of these measurements and those carried out at high pressure, it is concluded that conductivity of adenine hemisulphate hydrate is of electronic type.The authors wish to thank Dr. J. Zachová for the preparation of adenine salts single crystals.     

РАСПРЕДЕЛЕНИЕ ЗВЕЗД, ОБУСЛОВЛЕННЫ Х КОСМИ ЧЕСКИМ ИЗЛУЧЕНИЕМ, В ЛДЕРНЫХ ЗМУЛЬСИЯХ

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On the star distribution, caused by the cosmic rays in nuclear emulsions

     

ФОТОЯДЕРНЫЙ ЭФФЕКТ Н А НИКЕЛЕ, МЕДИ И ЦИНКЕ

, - 17,6 , . , (8±4)·10^–23, (7±4)·10^–23 (4±2)·10^{–23 2}. , - .     

A resistometric investigation of the decomposition kinetics of Al-21·8 at.% Zn solid solution at 276 °C

Under the condition of nearly equilibrium concentration of vacancies, time dependence of the amount of isothermal transformation given byy=R/R _f was investigated whereR _f is the total structural change of resistivity on completion of the whole process andR is the measured resistivity change. The investigation was done on the 21·8 at.% (40·3wt.%) Zn alloy under the condition of relatively low supersaturation of a few degrees centigrade below the metastable _R solvus line. The total transformation involves four kinetic stages: the first two stages correspond probably to diffusion-controlled growth of the _R particles from the supersaturated solid solution and to the ripening of these particles till their conversion to the cubic phase takes place. The last two kinetic stages account analogously for the particles growth and ripening. Both _R and phases were identified by the transmission electron microscopy. When separating the individual stages, the approximation byy=1–exp [–(mt) ⁿ] of the amount of transformationy was used. The approximation allowed to get the starting values of both the time and the change of the structural part of the electrical resistance for individual stages and also to derive the parametersm _i, n_i which had to be redetermined for the individual separated stages. These data made it possible to synthetize the experimental curves ofR andy vs. time for the total transformation.It is a pleasure to thank Doc. Dr. V.Syneek CSc. for stimulating the author's interest in this problem and for providing helpful discussions. I also would like to express my thanks to Ing. P.Bartuka CSc. for the transmission electron microscopic study carried out to identify the particular phases. The author is indebted to Ing.V. íma for the preparation of the investigated alloy and to Mrs. A.Mendlová and Mr. P.Vyhlídka for technical assistance.     

The structure of83Sr excited states

The -decay of⁸³Y isomers (7.06 min and 2.85 min) have been studied by means of Ge (Li) detectors. The proposed level scheme of the⁸³Sr nucleus is based on the coincidence measurement and the analysis of energy sums. The intensity balance requirement leads to _T (35·5 keV)=3.2 which is consistent with M1 multipolarity of this transition. A probable structure of some of the excited states in the⁸³Sr nucleus is discussed in the framework of Alaga's model and Kuriyama's model.     

Magnetic study of some liquids and gases adsorbed on polymers

The paper reports on the measurements of magnetic susceptibility of methylalcohol and toluene adsorbed on polypropylenes of two different molecular masses PP 5056, PP 5078, polyethylene-terephtalate and cellulose. The measurements were carried out for the full range of covering, possible at room temperature, and comparison with the additivity law was made in the whole range of concentrations. With the exception of methylalcohol in PP 5078, all samples showed noticeable deviations from linearity in the dependence of susceptibility on the percentual share of the adsorbate, the deviations were towards decreasing diamagnetism. Polyethyleneterephtalate with methylalcohol showed contradictory results. The measurements were completed with a magnetic study of adsorption of natural air and pure oxygen on cellulose and PP 5506.As far as the interpretation is concerned, the measurements of magnetic susceptibility are in good agreement with experiments on high resolution nuclear magnetic resonance (NMR). From the experimental results the authors draw up conclusions as to the character of mutual interaction of polymers with given adsorbates, to the location of an adsorbed molecule on the polymer surface, and to the contribution of Van Vleck polarization paramagnetism and other susceptibility components on the experimental results.Toluene C₆H₅.CH₃, adsorbed on polypropylene, showed two more peaks beside a NMR signal of C₆H₅; they were identified as the signals of CH₃ adsorbed on non-equivalent parts of a polypropylene macromolecule.     

160Tb nuclear orientation in yttrium single crystal

First experimental results of¹⁶⁰Tb nuclear orientation in yttrium single crystal matrix are described. The influence of external magnetic field in combination with the crystal field interaction is discussed.