15min:

JOSHUA P. DARR AND RICHARD A. LOOMIS, Department of Chemistry, Washington University, One Brookings Drive, CB 1134, Saint Louis, MO 63130.

Two-laser, pump-probe spectroscopy experiments reveal different dissociation pathways for He ICl( B , v ') intermolecular levels. Weakly bound He I³⁵Cl( B , v '=3) complexes that are prepared with different quanta of intermolecular vibrational excitation are observed to undergo vibrational predissociation to yield predominantly I³⁵Cl( B , v '=2) products. The I³⁵Cl( B , v '=2) rotational product state distributions formed following the excitation of different intermolecular vibrational levels and rotational states are all bimodal. Less rotational excitation is found in the products when preparing He ICl( B , v ') bending levels that preferentially sample the linear He-I-Cl and anti-linear I-Cl-He orientations than when preparing the lowest intermolecular vibrational energy level, which has a preferred T-shaped geometry. Additionally, linear He I³⁵Cl( B , v '=2) complexes undergo a direct dissociation mechanism when prepared above the He + I³⁵Cl( B , v '=2) dissociation limit. The I³⁵Cl( B , v '=2) products are formed with significantly less rotational excitation via this mechanism. Dynamical effects believed to be associated with tunneling through the centrifugal barrier are observed and result in highly non-statistical rotational distributions.