15min:

AMY BURROUGHS AND MICHAEL C. HEAVEN, Department of Chemistry, Emory University, Atlanta, GA 30322.

~~~~~Three-dimensional quantum dynamics models for the predissociation of I₂(B)Ar were examined by Gray and Roncero. Their calculations predicted highly structured rotational population distributions for the I₂(B) products. The distributions were characteristic of dynamics controlled by intramolecular vibrational energy redistribution (IVR). To test this model we have examined final state distributions resulting from predissociation of T-shaped I₂(B)Ar using optical-optical double resonance (OODR) techniques. We observed smooth rotational distributions that are indicative of direct dissociation or IVR occurring with level densities near the statistical limit.

~~~~~OODR measurements were used to probe the highest vibrational level of I₂(B) populated by predissociation of T-shaped I₂(B)Ar. This is a matter of interest as Stevens Miller et al. have suggested that previous measurements may be in error, leading to overestimation of the bond strength for the B and X states of I₂Ar. The previous measurements relied on detection of dispersed fluorescence from I₂(B), and may have been influenced by non-adiabatic decay channels. OODR is a more sensitive technique, potentially capable of detecting the highest energy products prior to non-radiative decay. However, the OODR experiments yield results that are in agreement with the earlier study.^ c The data do not resolve conflicts associated with the relative bond strengths of the T-shaped and linear isomers.^ c

~~~~~OODR techniques are being used to characterize the predissociation of linear I₂(B)Ar. Initial measurements show that I₂(B) from the linear isomer has less rotational energy than I₂(B) from the T-shaped complex.

Work supported by the National Science Foundation