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Reaction of 5-methyl-2-(p-nitrophenyl)oxazolo[3,2-a]pyridinium perchlorate with acetylacetone gives 1-acetyl-2,5-dimethylindolizine, the structure of which was proved by X-ray analysis.

An investigation was made of the impact and inhomogeneous broadening of a line emitted by a traveling-wave helium–neon laser with a circularly anisotropic resonator. The pressure dependences of the beats between the opposite waves were determined experimentally for two Ne20–Ne22 isotopic mixtures (99.7 and 53% Ne20) and for three ratios of the partial pressures of the components pHe:pNe = 14:1, 9:1, and 4:1. The pressure dependences of the beat frequency were also calculated for parameters of the homogeneous (γab) and inhomogeneous (ku) broadening taken from the experimental data. The rates of change of γab with the partial pressures of He and Ne (∂γab/∂pHe = 28.4 ± 1 and ∂γab/∂pNe = 9.5 ± 2.5 MHz/mm Hg) and the value of ku (480 ± 15 MHz) were determined.

A study was made of a stabilized laser source based on a two-mode helium--neon ring laser with a circularly anisotropic resonator. This laser emitted at 0.63 ..mu... The frequency was stabilized by comparing the frequencies of the Zeeman beats between the orthogonal modes of the opposite waves. The relative frequency stability achieved in this way was 8.8 x 10/sup -12/ in an averaging time of 1 min.

The signal/noise ratio was improved in the measurement of the indicatrix of the light scattered by laser mirrors. The improvement was achieved by using the energy accumulated in a unidirectionally operated traveling-wave laser resonator. A description is given of the apparatus with which this method was put to test and the results of the measurements are given.