Mass Spectrometric Study of Ion–Neutral Reactions in Radio-Frequency Discharges in Carbon Dioxide

Abundances of positive ions and neutral molecules emanating from an active radio-frequency discharge in CO2 at pressures from 0.01 to 1 torr have been determined mass spectrometrically. The data are used to evaluate rate constants for ion–neutral reactions occuring in the discharge. The results are in agreement with previous results for reactions occuring in an electron-impact ion source and in thermalized flowing afterglows. The large yield of O2+ at the higher discharge pressures is attributed mainly to charge transfer to O2, the extent of which is enhanced by the long retention (and hence reaction) time resulting from the low mobility of CO2+ at the higher pressures.