Ar OH Research Articles

Van der Waals vibrational dependence in the vibrational predissociation dynamics of OH–Ar

The OH–Ar vibrational predissociation lifetimes and OH product rotational state distributions are shown to change with van der Waals (vdW) state selection within the manifold of OH–Ar vibrational states correlating with OH A2Σ+(v′=1)+Ar(1S0). Excitations to pure vdW stretching levels result in similar product state distributions, but predissociation lifetimes that vary from 30±8 ps at v′vdW=0 to greater than 150 ps at vvdW=6. Excitations to assigned vdW bend-stretch combination bands result in product state distributions which differ from those observed after excitation of the pure vdW stretch and those differences are attributed to the form of the bending wave function. Rotational constants and band positions for OH–Ar features in the OH A2Σ+–X2Π3/2 0–0, 1–0, 1–1, 2–1, 1–2, and 2–2 regions are also presented. The spectroscopic analysis reveals details about the radial portion of the intermolecular potential between Ar (1S0) and hydroxyl radicals in the ground X2Π3/2 and excited A2Σ+ states. Vibrational excitation of the OH moiety induces measurable perturbations in the interaction potentials along the OH–Ar vdW stretching coordinate for both electronic states. These changes are reflected in the vibrational predissociation rates.