Experimental interrogation of the multidimensional He+ICl (E, v†) and He+ICl (Β, v†) intermolecular potential energy surfaces

Resonant two-photon excitation of the T-shaped and linear He⋯I ³⁵Cl(X, v″ = 0) complexes is used to access the intermolecular vibrational levels bound within the He+ICl(Β, v† =0-2) and He+ICl(E, v† = 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†) and He+ICl(Β, v†) 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 ³⁵Cl(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 ³⁵Cl complexes in the He+ICl(A, v′ = 15), He+ICl(B, v′ = 3), He+ICl(Β, v† = 1), and He+ICl(E, v† = 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(Β, v†) state and the ICl(D′, v†) molecular state is observed.