Analysis of positive ions in CO2 gas laser systems

Positive ions in the cathode region of electrical discharges through a 6% CO 2 , 12% N 2 and 82% He gas mixture and through initially pure carbon dioxide have been examined with a time-of-flight mass spectrometer. Mass peaks have been found corresponding to CO 2 + , O 2 + , CO + , N 2 + and H 2 O + for the mixture, and corresponding to CO 2 + , O 2 + , CO + , H 2 O + , O + and C + for CO 2 . The variations of the peak heights with discharge current, gas pressure and gas flow rate are presented. The peaks are interpreted in terms of the production of ions in the negative glow and cathode fall regions, subsequent ion-neutral collisions and the characteristics of the mass spectrometer.