Detailed vibrational population distributions in a CO2 laser discharge as measured with a tunable diode laser

A tunable diode laser (TDL) operating in the 2150-2350/cm wavenumber region is used to probe a conventional CW CO2 laser discharge. Absorption lines in more than 25 different vibrational bands are observed, enabling us to determine absolute vibrational populations in all levels of concern to the dynamics of the 10-micron CO2 laser. Levels in the v3 mode of CO2 as high as 00(0)9 are monitored, and it is found that anharmonic effects play a significant role in the populations of such levels. The v1 and v2 mode populations are also investigated in detail, and it is found that these modes are strongly coupled and maintain a common vibrational temperature under all discharge conditions. The use of a TDL is shown to be a powerful technique for investigating the dynamics of infrared molecular lasers.