STATE-TO-STATE DYNAMICS OF ATOM + POLYATOM ABSTRACTION REACTIONS .1. THE H+CD4-]HD(V',J')+CD3 REACTION

We report measurement of the HD product quantum state distributions and absolute cross section for the H + CD4 --> HD(upsilon',J') + CD3 reaction at a collision energy of 1.5 eV. The total reaction cross section is small, 0.14 +/- 0.03 angstrom 2, making the experimental measurements difficult. The HD quantum state distribution peaks at low J' in both upsilon' = 0 and upsilon' = 1, the only vibrational states in which product is observed. Very little of the 1.5 eV available energy appears as internal excitation of the HD product molecule, 7% in HD product vibration and 9% in rotation. However, linear surprisal analysis shows that this limited internal energy disposal in the HD product in some ways exceeds that expected statistically, since two of the best-fit surprisal parameters (THETA(r) = 2.9 +/- 0.6 for upsilon' = 0, THETA(r) = - 1.9 +/- 0.5 for upsilon' = 1, lambda(v) = - 2.2 +/- 0.6) are negative. The HD rovibrational state distribution shows an anomalous positive correlation of product vibrational and rotational excitation. Those molecules formed in the vibrationally excited state, upsilon' = 1, have significantly more rotational energy (<E(rot)> = 0.17 eV) than those molecules formed in the vibrational ground state, upsilon' = 0 (<E(rot)> = 0.13 eV). This behavior runs counter to the otherwise universal behavior for direct bimolecular reactions-a negative correlation of product vibrational and rotational excitation. We speculate as to the source of this anomalous energy disposal.