Suppression of clustering of CF3Br molecules with argon atoms by CO2 laser radiation in gas-dynamic expansion of a CF3Br–Ar mixture: bromine isotope selectivity

Abstract

We present the study of suppressing the clustering of CF3Br molecules with argon atoms under gas-dynamic expansion of the CF3Br–Ar mixture at a nozzle exit by a cw CO2 laser. The main attention is paid to the analysis of possibility of implementing the selective control of bromine isotope clustering. The method relies on the vibrational excitation of molecules with the laser radiation, which leads to the suppression of their clustering with argon atoms. The experimental setup and the method of study are briefly described. The results of evaluation of the efficiency and selectivity of suppression of molecular–atomic clustering for different compositions of the gas above the nozzle and separations between the irradiation zone and the nozzle exit section are presented. It is shown that under the resonance vibrational excitation of gas-dynamically cooled CF3Br molecules at the nozzle exit one can implement bromine isotope selective suppression of clustering of molecules with argon atoms. It is found that by controlling the clustering of CF3Br molecules with argon atoms one can implement considerably higher enrichment and selectivity factors than in the case of controlling the clustering of CF3Br molecules with each other. Thus, using the CF3Br–Ar mixture (the ratio of pressures 1 : 100 and 1 : 200) the enrichment factors for the bromine isotopes Kenr(81Br) = 1.50 ± 0.13 and 1.30 ± 0.09, respectively, were obtained under the conditions of irradiating the jet at the 9R(30) line of the laser (ν = 1084.635 cm−1). The selectivity α of the suppression of clustering of CF3Br molecules with argon atoms, achieved in this case, amounted to 4.02 ± 0.19 and 2.31 ± 0.11, respectively. The results show that the method allows one to selectively control the clustering of molecules, comprising isotopes of heavy elements that possess a small isotopic shift in the IR absorption spectra.