Dynamics of the CO2 upper laser level as measured with a tunable diode laser

A tunable diode laser (TDL) operating in the 2140-2310 per cm wavenumber region is used to probe a conventional CW CO2 laser discharge. Detailed vibrational populations in CO2 are measured under lasing conditions, i.e., in the presence of an intense 10-micron field. The TDL is also used to investigate the rate of recovery of the populations in a variety of vibrational levels after the passage of an intense 10-micron pulse. This paper deals mainly with the behavior of the upper laser level, and the associated nu3 mode. It is shown that electron deexcitation of the nu3 mode is very important, and is responsible for the limitation of the nu3 mode temperature observed previously. In typical gas mixtures, the ratio of the nu3 mode electron deexcitation rate constant to the electron excitation rate constant is approximately 3.5:1.