HIGH-RESOLUTION STUDIES OF OH/D(A, v=1)-Ar VIBRATIONAL PREDISSOCIATION

Abstract

Rapid vibrational predissociation of OH(A, v=1)-Ar is evident in the A-X excitation and resolved fluorescence $spectra^{1,2}$. In excitation, predissociation causes homogeneous broadening of the rotational lines. Berry $et. al.^{1}$ reported linewidths ranging from $<$0.05 to $0.26 cm^{-1}$, which were determined from spectra taken at a resolution of $0.1 cm^{-1}$. They noted that they predissociation rate decreased with increasing excitation of the van der Waals stretch, but in a manner that was not consistent with simple energy or momentum gap $laws^{3}$. Departures from these models were also indicated by the spectra for $OD(A, v=1)-Ar^{2}$. Based on the smaller vibrational interval for OD(A), a V-T energy gap model predicts that OD-Ar will predissociate much more rapidly that OH-Ar. However, homogeneous line broadening could not be detected in OD(A, v=1)-Ar spectra recorded at $0.08 cm^{-1}$ $resolution^{2}$. In order to examine the predissociation dynamics in more detail, we are using a pulse amplified ring dye laser system to record OH/D (A, v=1)-Ar bands at $0.01 cm^{-1}$ resolution. Results from these measurements, and their dynamical implications, will be discussed.