Accurate measurement of the T-shaped and linear Ar ⋯ i ₂ (X, ^ν' = 0) binding energies using vibronic-specific I ₂(B, ν) fragment velocity-map imaging

Ion time-of-flight slow fragment velocity imaging (SFVI) is combined with laser-induced fluorescence spectroscopy measurements to accurately determine the binding energies of the T-shaped and linear conformers of the ground-state Ar⋯I ₂(X, ^ν″=0) complex. The fluorescence-based measurements were used to optimize the conditions for preferentially stabilizing either the T-shaped or linear conformers, and to ensure proper excitation energetics for the SFVI experiments. In the ion-imaging experiments, the kinetic energy distributions of specific I ₂(B, ν) fragments formed with very low kinetic energies via dissociation of initially prepared Ar⋯I ₂(B, ν′) intermolecular vibrational levels were imaged to measure the binding energies of the linear and T-shaped conformers. The linear conformer is energetically preferred, with a binding energy of 250.3(2.7) cm ^-1, over the T-shaped conformer, with a binding energy of 240.5(3.6) cm ^-1. These values are compared with previously reported data from high-level ab initio calculations and experiments.