A CO plasma can be excited to a strong vibrational disequilibrium by CO laser radiation. From such an optically pumped CO plasma, we have been able to observe CO laser emission. This type of new excitation mechanism for the CO laser will provide a very good means to study relaxation processes in a running laser under much better defined experimental conditions than in gas discharge lasers.

We describe a modified design of a continuous-flow cw CO laser with longitudinal electric discharge using an externally ribbed wall cooled discharge tube. The transverse ribbed discharge tube provides a more intense heat exchange of the CO-laser gas with the walls. With this configuration it was possible to obtain about 50% more output power from an all-line CO Δv=1 laser. For a CO-overtone Δv=2 laser we were able to improve both the output power and the number of lines as compared to a conventional smooth tube.

A careful analysis of experimental data for a CO laser plasma shows a considerable depletion of the vibrational distribution of the electronic ground state in the energy range of the first excited electronic state a 3 Π. If the transferred population would reappear completely, the corresponding concentration of CO in the a 3 Π state should be observable by the most sensitive Faraday laser magnetic resonance technique. From the fact that no signal could be found, we deduce an upper concentration for CO a 3 Π which is then compared to a new refined model. This model takes into account both VE transfer rates between the ground state and the a 3 Π and a relaxation rate for the triplet state.