Abstract

Recent experiments performed in this laboratory have provided a detailed picture of the intermolecular potential between the open-shell hydroxyl radical and an argon atom. The interaction potentials between Ar (¹S₀) and OH in the ground $\text{X}{}^2{\text{II}}_{\raisebox{1ex}{$3$}\!\left/ \!\raisebox{-1ex}{$2$}\right.}$ and excited A ²Σ⁺ electronic states have been probed through spectroscopic measurements and half-collision studies of the weakly bound OH-Arvan der Waals (vdW) complex. Vibrational excitation of the OH subunit induces dissociation of the complex, providing a means to examine the dynamics taking place on these potential energy surfaces. Our results show striking differences, in both the potentials and dynamics, between the ground and excited electronic states. The rate of dissociation is at least five orders of magnitude slower in the ground electronic state than in the excited state. The dissociation dynamics for OH-Ar complexes correlating with changes with initial vdW state selection. The product rotational distribution reflects the bending wave function of the complex, while the rate of dissociation depends on the number of quanta of excitation in the vdW stretching coordinate. The rate becomes faster as the excitation in the vdW stretch is decreased.

© 1990 Optical Society of America