ELECTRONIC-STATE DISTRIBUTION OF XE-+ASTERISK FORMED BY EXCITATION TRANSFER FROM HE(2 S-3) TO XE+(P-2(3/2)0) AT THERMAL-ENERGY

The formation process of Xe+* in the He afterglow reaction of Xe has been studied by observing Xe II lines in the ultraviolet and visible regions. Sixty one Xe+* states in the 13.86-19.49 eV range were excited by the He(2 3S)+Xe+(5p5 2P3/20) excitation-transfer reaction. It was found that Xe+* was not formed by the He(2 3S)+Xe(6s 3P20) Penning type reaction and the He ++Xe(6s 3P20) charge-transfer reaction. There were some unclassified Xe II lines, which occupied 14% of the total production of Xe+*. Most of them were attributed to Xe+ transitions from unknown high energy Xe+* states in the 18-19.5 eV range. The electronic state distribution of individual Xe+* levels has been determined by taking account of radiative cascade for low lying electronic levels. The He(2 3S)+Xe +(2P3/20) reaction expressed no resonant character. The electronic state of Xe+* was distributed more widely than those of Ar+* and Kr +* in the He(2 3S)+Ar+(3p5 2P3/20), He(2 3S)+Kr +(4p5 2P1/20), and He(2 3S)+Kr+(4p5 2P3/2 0) reactions. The excitation mechanism of rare gas cations due to collisions between a rare gas metastable atom and a rare gas ion is discussed. The lack of the excitation processes of Kr+* and Xe +* by the He++Kr(3P2 0) and He++Xe(3P20) reactions was attributed to the absence of near-resonant Kr+(5p) and Xe+(6p) states whose excitation satisfies the selection rule of Δl=±1. © 1994 American Institute of Physics.