Selective processes of IR excitation and dissociation of molecules in gasdynamically cooled jets and flows

Research into the selective excitation and dissociation of molecules by intense IR laser radiation in gasdynamically cooled jets and flows is reviewed. Methods for and results of studying the spectral and energy characteristics of molecular excitation and dissociation are described. It is shown that vibrational and rotational temperatures, together with collision processes, have a pronounced effect on the formation of spectral structures and on the selectivity of dissociation. Diode laser spectroscopic data on the dynamics of the molecular excitation from individual rotational sublevels of the ground vibrational state are presented. Molecular excitation models for lower vibrational transitions are discussed and related problems are considered. Experimental and theoretical findings are compared and their discrepancies are analyzed. The isotopically selective dissociation of molecules under low-temperature and low gas concentration conditions is discussed, the related problems are identified, and methods for their solution are considered. Results on how the main dissociation characteristics — selectivity and dissociation yield — vary with the laser radiation and gas flow parameters are presented. Methods for improving dissociation efficiency are described, and optimal conditions for high selectivity and dissociation yield are pointed out.