Knowledge Bank

The direct extraction of state-to-state rotationally inelastic rate constants, , from pressure-broadened line width data (a measure of the total inelastic rate) has generally been considered an intractable problem. In this paper we present two new developments which allow, for the first time, the deconvolution of experimental data to yield the individual rates without recourse to any dynamical calculations. These innovations not only eliminate the redundancies in the rates and assess the Information content in the data but also show that the amount of experimental information is directly related to the dependence of linewidth on rotational quantum number. Consequently, it is of prime importance experimentally to measure the halfwidths for various rotational lines. The application of this inversion procedure to typical atom-molecule and molecule-molecule systems is considered. The rates as determined from the line width data are shown to be in good agreement with those available from the few accurate ab initio dynamical calculations on atom-molecule collisions. In addition, many other systems have been studied by this inversion procedure and a wealth of detailed collisional information (e.g., propensity rules for multiple quantum transitions, physical trends using different collision partners, etc.) will he shown to be obtainable from experimental data of reasonable accuracy.