The Role of Excited Electronic States in Hypervelocity Collisions: Enhancement of the O(³P) + HCL → OCl + H Reaction Channel

The role of excited electronic states in the O + HCl reaction was studied using the quasi-classical trajectory method for collision energies between 1 and 5.5 eV. Global potential energy surfaces were developed for the ground (3A\u27\u27) and first excited (3A\u27\u27) electronic states of the OHCl system using an interpolating moving least-squares-based method for energies up to 6.5 eV above the reactant valley. High-accuracy ab initio datawere computed at automatically selected points using an 18-electronic-state model and the generalized dynamically weighted multireference configuration interaction (GDW-MRCI ) method extrapolated to the complete basis set limit. The results show significant dynamical differences between ground- and excited-state reactions. At high collision energies, over half of the total OCl reactive flux originates from reactions on the 3A\u27\u27 state, whereas OH is produced almost exclusively by the 3A\u27\u27 state. Inclusion of the excited electronic state, therefore, dramatically alters the OCl/OH product branching ratio