15min:

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

Two-photon excitation of the T-shaped and linear He I³⁵Cl( X ^{1 +}, v ''=0) complexes are used to access multiple intermolecular vibrational levels within the He + I³⁵Cl( E 0^{+ 3}P₂, v ^ =11,12) and He + I³⁵Cl( 1 ³P₂, v ^ =0-2) ion-pair state intermolecular potentials. The excitation utilizes different metastable intermolecular levels within the He + I³⁵Cl( B ³ ₀₊, v '=2,3) and He + I³⁵Cl( A ³ ₁, v '=15) potentials, and thus varying Franck-Condon windows, to access levels with varying amounts of vibrational excitation within the ion-pair state intermolecular potential. The He + ICl( E , v ^ =11,12) and He + ICl( , v ^ =0-2) intermolecular potentials are found to be nearly identical with an overall minimum in the near T-shaped orientation and binding energies D ₀^ = 40 cm^-1. Intermolecular stretching and bending frequencies are measured to be 25 and 13 cm^-1, respectively. Since common intermolecular levels are accessed by transitions from both the T-shaped and linear He ICl( X , v ''=0) ground state conformers, the relative binding energies of the conformers can be directly measured; the linear conformer is found to be 5.4(2) cm^-1 more strongly bound than the T-shaped conformer.