Unimolecular reaction dynamics of HSO. Analysis of the influence of different barrier samplings on the product energy distributions

Abstract

Classical dynamics calculations are reported for the lowest energy unimolecular reaction channels of HSO. A recently published single-valued DMBE potential energy surface for HSO was employed in the dynamics calculations. The results predict that the isomerization channel HSO → HOS is the preferred one at the lowest energies of the study, while dissociation to give H + SO is increasingly important as the energy rises. For the energies selected, the vibrational coupling is not strong enough to keep the phase space uniform during the unimolecular dynamics. In addition, strong mode specific effects were found under initial excitation of the three normal modes of vibration. The product energy distributions obtained with classical and quasi-classical barrier sampling techniques are very similar. The results predicted by EMS (with and without ZPE restrictions) initialization at the barrier show a much higher vibrational energy content of the products than those obtained by the above sampling techniques. This arises from the separability of the reaction coordinate mode inherent to the QCBS and CBS models.