Ultraviolet absorption by diatomic rare gas ions in E-beam excited plasmas

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Abstract
Absorption has been measured at 295 and 320 nm in electron‐beam excited mixtures of argon, krypton, and fluorine. The absorbing species are identified as the diatomic rare gas ions Ar+2, ArKr+, and Kr+2. By using kinetic models to calculate ion number densities in the absence of fluorine, absorption cross sections are determined for these species. At 295 nm, they are 5.8×10−17 cm2 for Ar+2, 1×10−17 cm2 for ArKr+, and 2.6×10−17 cm2 for Kr+2. At 320 nm, the cross sections are 5.4×10−17 cm2, 2.5×10−17 cm2, and 3.1×10−17 cm2, respectively. Errors of ±18% are estimated for these values. Absorption in mixtures containing fluorine is higher, and the presence of additional absorbing species is indicated. The most likely candidates are the triatomic excimers Ar2F, Kr2F, and possibly ArKrF.