State-to-state dynamics of atom + polyatom abstraction reactions. I. The H+CD sub 4 r arrow HD( v prime , J prime )+CD sub 3 reaction

We report measurement of the HD product quantum state distributions and absolute cross section for the H+CD{sub 4}{r arrow}HD({ital v}{prime},{ital J}{prime})+CD{sub 3} reaction at a collision energy of 1.5 eV. The total reaction cross section is small, 0.14{plus minus}0.03 A{sup 2}, making the experimental measurements difficult. The HD quantum state distribution peaks at low {ital J}{prime} in both {ital v}{prime}=0 and {ital v}{prime}=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}{sub {ital r}}=2.9{plus minus}0.6 for {ital v}{prime}=0, {Theta}{sub {ital r}}={minus}1.9{plus minus}0.5 for {ital v}{prime}=1, {lambda}{sub {ital v}}={minus}2.2{plus minus}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, {ital v}{prime}=1, have significantly more rotational energy ({l angle}{ital E}{sub rot}{r angle}=0.17 eV) than those molecules formed in the vibrational ground state, {ital v}{prime}=0 ({l angle}{ital E}{sub rot}{rmore » angle}=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.« less