Molecular relaxation in supersonic free jets of N2 and CH4 from stimulated Raman spectroscopy and time-of-flight measurements

摘要

The relaxation of the energy stored in the translational and rotational degrees of freedom of N2 and CH4 in the course of free jet expansions has been experimentally studied. Rotational temperatures along the expansion axis were obtained by means of stimulated Raman spectroscopy, and terminal flow velocities and translational temperatures were determined from supersonic beam time-of-flight measurements. From these measurements low-temperature cross sections for rotational relaxation have been estimated. The results are compared with data from other experiments, and the validity of simple relaxation models is discussed. © 1997 American Chemical Society