Cooperative photoabsorption induced charge transfer reaction dynamics in rare gas solids. I. Photodynamics of localized xenon chloride exciplexes

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Abstract
Cooperative charge transfer absorptions are demonstrated in HCl, Cl2, and Cl doped rare gas solids. The four‐body, two‐photon cross section for Xe+HCl+2hν→Xe+(HCl)− at 308 nm is >10−42 cm4 s. The same mechanism explains the efficient Cl atom photogeneration in Cl2 doped solids. The weak field cross sections for the three‐body one‐photon and four‐body one‐photon transitions, Xe+Cl+ hν→XeCl(B) and Xe+Xe+Cl+hν→Xe2Cl(4 2Γ), are comparable near the B←X resonance, the cross sections are estimated as 3 and 1(±0.5)×10−16 cm2. The XeCl C→A emission, B←X absorption, and C state lifetime [75 (±5) and 60 (±5) ns in Ar and Kr], can be accounted by bulk dielectric solvation of the molecular dipole. The Xe2Cl(4 2Γ) emission [573 nm in Ar, Kr, and Xe], and lifetime [250 (±10), 210 (±10) and 225(±10) ns in Ar, Kr, Xe] cannot be treated by the same model. The XeCl (B)→XeCl(C) and XeCl(C)+Xe→Xe2Cl(4 2Γ) reactions are fast, >2×1010 s−1. The XeCl(C) and Xe2Cl(4 2Γ) emissions can be modeled with one‐ and two‐dimensional potentials using gas phase diatomic parameters: the localized excitons retain their molecular nature.