Observation of bound-free transitions of the linear Ar⋯I ₂ (X, v″ =0) complex in and above the I ₂ B-X spectral region

Laser-induced fluorescence and action spectroscopy experiments were performed to identify the origin of the Ar⋯ I2 continuum signals observed in and above the I2 B-X spectral region. We have verified that these signals arise from transitions of the linear Ar⋯ I2 (X, v″ =0) complex. The data provides no evidence that the excited state complexes undergo a one-atom caging mechanism when prepared above the I2 (B) dissociation limit, Ar⋯ I2 (B)* →Ar+I+I*→Ar+ I2 (B, v′). Instead, our results indicate that the continuum signals result from bound-free transitions of the linear Ar⋯ I2 (X, v″ =0) complex to the inner repulsive walls of numerous Ar+ I2 (B, v′) intermolecular potentials. The bound-free continuum signal associated with transitions to each Ar+ I2 (B, v′) potential spans an energy region >700 cm-1. We have found that the continuum signals turn-on 250 (2) cm-1 above the corresponding I2 B-X, v′ -0 band origin, and this energy represents the binding energy of the linear Ar⋯ I2 (X, v″ =0) conformer, D0″ (L) =250 (2) cm-1.