Laser-induced infrared photofragmentation of SF₆·(C₆H₆)_n⁺ cluster ions

Size-selected SF₆·(C₆H₆)_n⁺ cluster ions have been photoexcited in the infrared using radiation from a line-tuneable CO₂ laser. In contrast to metastable (unimolecular) decay where loss of C₆H₆ is the dominant decay channel, photoexcitation only promotes the loss of SF₆. This observation is rationalized in terms of a structure where SF₆ resides on the surface of the cluster and there is no statistical partitioning of the photon's energy prior to dissociation. Further support for a surface-bound SF₆ is provided by infrared absorption profiles recorded as a function of laser wavelength. These latter measurements also show that SF₆·(C₆H₆)₁₄⁺ may adopt a structure that is more symmetric than those of its immediate neighbors.