Experimental interrogation of the multidimensional He + ICl(E, v(dagger)) and He + ICl(beta, v(dagger)) intermolecular potential energy surfaces.

Resonant two-photon excitation of the T-shaped and linear He...I(35)Cl(X,v(") = 0) complexes is used to access the intermolecular vibrational levels bound within the He + ICl(beta,v(dagger) = 0-2) and He + ICl(E,v(dagger) = 11,12) intermolecular potentials. The excitation utilizes different metastable intermolecular vibrational levels within the He + ICl(A,v(') = 15) and He + ICl(B,v(') = 2,3) potentials to access levels with varying intermolecular vibrational excitation in the ion-pair states. In addition to providing data revealing properties of the He + ICl(E,v(dagger)) and He + ICl(beta,v(dagger)) potentials, the transition energies of the observed features permit the relative binding energies of the T-shaped and linear ground-state He...ICl(X,v(") = 0) conformers to be accurately measured. The binding energies of the T-shaped and linear He...I(35)Cl(X,v(") = 0) conformers are 16.6(3) and 22.0(2) cm(-1), respectively. These values and the observed transition energies are then used to set the binding energies of the T-shaped He...I(35)Cl complexes in the He + ICl(A,v(') = 15), He + ICl(B,v(') = 3), He + ICl(beta,v(dagger) = 1), and He + ICl(E,v(dagger) = 12) potentials as 13.4(3), 13.3(3), 41(1), and 39.2(4) cm(-1), respectively. Nonadiabatic coupling between specific intermolecular vibrational levels within the He + ICl(beta,v(dagger)) state and the ICl(D('),v(dagger)) molecular state is observed.