Reaction and deactivation of HCl ( v =1, 2) by O atoms

Laser-induced fluorescence, following direct excitation of HCl (v=2), was used to measure the total deactivation rate constant for HCl (v=2) by O(3Pg) atoms as (5.2±0.4) ×10−12 cm3 molecule−1 sec−1. This is partitioned into a reaction rate constant of (1.5±1.2) ×10−12 cm3 molecule−1 sec−1 for HCl (v=2)+O(3Pg) →OH (v=1, 0)+Cl and a relaxation rate constant for HCl (v=2)+O(3Pg) →HCl (v=1)+O(3Pg) of (3.7±1.2) ×10−12 cm3 molecule−1 sec−1. The total deactivation rate constant for HCl (v=1)+O(3Pg) atoms, including reaction and relaxation, was measured to be (8.9±1.3) ×10−13 cm3 molecule−1 sec−1. All measurements were carried out at 296±2 °K. The vibrationally enhanced chemical reaction rate constant for HCl (v=2) is roughly a factor of 104 greater than the reaction rate constant for HCl (v=0) with O atoms. The reaction appears to occur adiabatically on the lowest triplet potential hypersurface. For HCl (v=2, 1)+O vibrational relaxation is faster than chemical reaction even though the total energy is well above the barrier to reaction.