Accurate measurements of pressure-broadened linewidths in a transversely excited CO2 discharge

A novel technique has been used to obtain detailed measurements of He-broadened CO2 linewidths as a function of the rotational quantum number and temperature. The technique, which is based on measuring gain in a TE CO2 discharge with a CW probe laser operating at CO2 and N2O transitions with a known frequency offset, makes it possible to determine the linewidth to within 2 percent. Although the measurements reported here are limited to the 10-micron P-branch (because of chance coincidences with CW NO2 laser transitions), this technique can be easily extended to the R-branch and the 9-micron band by utilizing CO2 isotopes in the probe laser. The results of this study have been combined with previous work on CO2-CO2 and CO2-N2 broadening coefficients to derive simple formulas for calculating linewidths over the entire range of the operating conditions of CO2 lasers.