Formation of Excimers by Ionic-Recombination Reactions between Rare Gas Positive Ions and Halogen Anions

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A flowing-afterglow apparatus for studying ionic-recombination reactions between a rare gas positive ion and a halogen anion has been developed. Ar^+, Kr^+, Xe^+ ions were generated by Penning ionization, while halogen anions were produced by an electron attachment to halogen-containing compounds. Two-body and three-body Ionic recombination reactions between positive ions and anions result in excimer emissions.Ar^+, Kr^+, Xe^+ + SF_6^-> ArF^*, KrF^*, XeF^*+SF_5 (1)Ar^+, Kr^+, Xe^+ +Cl^-+He -> ArCl^*, KrCl^*, XeCl^*+He (2)The spin-orbit state selectivity for the excimer formation was examined by isolating one 6f the spin-orbit state of rare gas, lon. A high propensity for the D formation from the ^2P_<1/2> reaction and for the B, C formation from the ^2P_<3/2>. reaction has been discovered. This result can be explained by adiabatic potential diagram. The relative formation rate of excimer from the ^2P_<1/2> reaction was smaller than that from the ^2P_<3/2> reaction. It was explained as due to faster predissociation in the former reaction. A high spin-orbit state selectivity was applied to the measurements of the ^2P_<1/2> : ^2P_<3/2> ratios in the He_2^+/Kr and He_2^+/Xe charge-transfer reactions. The ^2P_<1/2> : ^2P_<3/2> ratio was found to be a nearly statistical ratio of 1 : 2 for both reactions.