Photoinduced Harpoon Reactions as a Probe of Condensed-Phase Dynamics: IC1 in Liquid and Solid Xenon

Two-photon-induced harpoon reactions of IC1 in liquid and solid xenon are reported. The reaction dynamics is followed by monitoring the luminescent products: the triatomic Xe2Cl and Xe21 exciplexes. Action spectra and branching ratios as a function of excitation energy are reported. The efficient production of the nonthermodynamic product, the iodide, in the liquid phase implies that the cage exit of the ejected C1 atom is direct and sudden. The absence of iodide in the crystalline solids establishes the absence of direct cage exit in the ordered phase. Line-shift.measurements at the phase transition indicate that the exciplexes are strongly clustered in the liquid phase. The effect of clustering on dynamics is the prevention of exchange between iodide and chlorine-the solvent cage excludes C1 atoms. Branching ratios and action spectra are used to identify the potential surfaces in the exit channel and the optical resonances in the entrance channel. The two-photon charge-transfer excitations are enhanced by two-electron resonances that allow selectivity of products.