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

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.