The influence of oxygen on CO-laser performance

Additions of a few parts per thousand of oxygen to a CO-He mixture change drastically the laser output power, the axial field in the positive column, and the slope of the curve of the discharge. The intensity of the spectrum of vibrational transitions of the CO molecule increases when oxygen is added; the increase is especially pronounced for transitions from higher ( ) levels. The most prominent feature in the visible spectrum is the disappearance of the C2-Swan bands with the addition of oxygen. The populations of CO vibrational levels were derived from the IR spectra; they increase by more than an order of magnitude for . The electron energy distribution was derived from measured E/N and the Boltzmann equation. Oxygen affects the Boltzmann equation (and thus the electron energy-distribution function) through the change in E/N, which is in turn determined by ionization and deionization processes. The fractional power transfer from electrons increases to vibrational levels and decreases to electronic levels.