Refinement of the OH A²∑⁺(v=0)+Ar intermolecular potential energy surface

Abstract

Several intermolecular vibrational levels of the excited electronic state of OH-Ar correlating with OH A²∑⁺(v=0)+Ar have been characterized by laser-induced fluorescence and hole-burning experiments. The OH-Ar levels identified include the lowest intermolecular level, an intermolecular bending level with a lower degree of stretching excitation than previously observed, and intermolecular levels with two quanta of bending excitation. The intensities of electronic transitions to these levels from the lowest intermolecular level of the ground electronic state of OH-Ar (X²) are significantly weaker than those of transitions previously reported. These data are used to refine a semiempirical potential for OH A²∑⁺(v=0)+Ar proposed by Bowman et al. [J. Phys. Chem. 94, 2226 (1990)]. The potential parameters have been adjusted to increase the potential anisotropy and the steepness of the radial potential in the O-H-Ar well region. The bound states supported by the adjusted potential have been calculated by taking into account the electron spin angular momentum of the OH radical. The calculated vibrational energies and rotor constants reproduce the rovibrational structure observed experimentally. A theoretical simulation of the OH-Ar electronic excitation spectrum based on the adjusted intermolecular potential yields an intensity pattern which is consistent with experimental results.