Knowledge Bank

The photoacoustic and infrared fluorescence signal following $CO2$ laser excitation was measured for $CO2,N2O$, and $SF6$. The amplitude and phase of the resulting signal was measured as a function of modulation frequency and the V=V and V=T relaxation rates were determined by least squares fitting. The branching ratio for collisional deexcitation from (0,0,1) to the (0,m,0) states is determined for $N2O$ and $CO2$. The effect of thermal diffusion on the photoacoustic signal is observed at low pressure and included in the data analysis. Radiation trapping of the infrared fluorescence signal is also observed.