Dynamics of the CO<inf>2</inf>upper laser level as measured with a tunable diode laser

Abstract

A tunable diode laser (TDL) operating in the 2140-2310 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> wavenumber region is used to probe a conventional CW CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> laser discharge. Detailed vibrational populations in CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> are measured under lasing conditions, i.e., in the presence of an intense 10 μm 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 μm pulse. This paper deals mainly with the behavior of the upper laser level, and the associated ν <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> mode. We show that electron deex-citation of the ν <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> mode is very important, and is responsible for the limitation of the ν <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> mode temperature observed previously. In typical gas mixtures, the ratio of the ν <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> mode electron deexcitation rate constant to the electron excitation rate constant is <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\sim 3.5:1</tex> .