ANALYSIS OF TRANSLATIONAL, ROTATIONAL, AND VIBRATIONAL-ENERGY TRANSFER IN COLLISIONS BETWEEN CO2 AND HOT HYDROGEN-ATOMS - THE 3-DIMENSIONAL BREATHING ELLIPSOID MODEL

Classical scattering of a particle from a three-dimensional "breathing" ellipsoid is used to model translational, rotational, and vibrational energy transfer in collisions between hot hydrogen atoms and CO 2. The model combines the theoretical formalism which describes rotational scattering between a particle and a three-dimensional rigid ellipsoid with a simple scheme to account for the effects of CO2 vibrational excitation. The calculations are used to analyze experimental data (measured using time-domain diode laser absorption spectroscopy) concerning the state-specific deposition of energy among the translational, rotational, and vibrational degrees of freedom of CO2 following collisions with translationally hot H atoms. The model provides substantial insight into the features of the final-state-resolved experimental data, indicating which "types" of trajectories, e.g., "end-on" vs "broadside" collisions, are responsible for scattering into particular final states. Despite its simplicity, the model is shown to predict virtually all of the major features of the experimental data with remarkable accuracy. In addition, it reproduces highly complex behavior seen in the state-to-state collision cross sections which had been previously obtained using a data-inversion procedure. © 1990 American Institute of Physics.