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 2P03/2) excitation-transfer reaction. It was found that Xe+* was not formed by the He(2 3S)+Xe(6s 3P02) Penning type reaction and the He++Xe(6s 3P02) 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+(2P03/2) 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 2P03/2), He(2 3S)+Kr+(4p5 2P01/2), and He(2 3S)+Kr+(4p5 2P03/2) 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(3P02) and He++Xe(3P02) reactions was attributed to the absence of near-resonant Kr+(5p) and Xe+(6p) states whose excitation satisfies the selection rule of Δl=±1.

Arii lines have been observed by addition of Ar into the He flowing afterglow. The effect of ion collection in the He afterglow and the energetics lead us to conclude that the He(2 3S)+Ar+(3p5 2P3/2ο) excitation transfer gives the ten Ar+(4p 4P5/2,3/2,1/2ο,4p 4D7/2,5/2,3/2,1/2ο, 4p 2D5/2,3/2ο,4p 2P1/2ο) levels in the 19.22–19.80 eV range, while the He++Ar(4s 3P2ο) charge transfer populates the three Ar+(4p 2P3/2ο,4p 4S3/2ο, 4p 2S1/2ο) levels in the 19.87–19.97 eV range. The relative rate constants for excitation of individual Ar+(4p) ions have been measured. The favored exit channel is the 4p 4P3/2ο level in the former reaction, and the 4p 2P3/2ο level in the latter reaction. Since these channels are 0.5–0.6 eV below the entrance channels, attractive entrance potentials are probably important for both reactions.

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