Classical Trajectory Study of Mode Specificity and Rotational Effects in Unimolecular Dissociation of HO2

Abstract

Trajectory calculations are presented for the unimolecular dissociation of HO2. The study covers internal energies in the range 58.311 ≤ Etot/kcal mol-1 ≤ 59.432, just above the H + O2 threshold, and Etot = 76.412 kcal mol-1 for which the O + OH channel is also open. The HO2 single-valued double many-body expansion potential energy surface has been employed in all calculations. Due to strong coupling among the vibrational degrees of freedom, mode specificity is shown to play a minor role in the formation of H + O2. Conversely, the increase of initial rotational energy clearly influences the dynamics of the unimolecular dissociation. In particular, energy placed in a specific rotational degree of freedom can dramatically modify the yield of O2 or OH products and corresponding decay rates. The results show the importance of rotational effects in order to correctly describe the unimolecular dissociation of HO2.