The yield of metastable atoms through dissociative recombination of O sup + sub 2 ions with electrons

The yield of metastable oxygen atoms through dissociative recombination of O{sup +}{sub 2} ions with electrons has been studied using a plasma flow tube experiment. For O{sup +}{sub 2} with high vibrational excitation (around {ital v}=9) it was found that half of the oxygen atoms are formed on the O({sup 1}{ital D}) state and that the branching ratio toward O({sup 1}{ital S}) is large ({similar to}0.4). Using Xe{sup +} instead of Ar{sup +} as precursor ions, it was shown that the O({sup 1}{ital S}) yield is much less for ions with low vibrational excitation. However, the present experimental results are not compatible with the extremely low theoretical value of this yield which was reported recently for O{sup +}{sub 2} ({ital v}=0).