IR‐Luminescence of CF2Cl2 Molecules in Multiple‐Photon Excitation With Co2‐Laser Radiation

We studied the IR luminescence spectra of vibrationally excited CF 2 Cl 2 moleculesresulting from excitation of the ν 1 (1098 cm −1 ) and ν 8 (922 cm −1 ) modes with a pulsed CO 2 laser. The nonequilibrium spectra obtained under pumping conditions where their equilibrium counterparts coincide (the number of the photons absorbed per molecule being the same) were found to differ considerably. We suppose that this difference is due to different types of vibrational distribution formed as a result of the IR laser pumping. When pumping the ν 1 mode, excitation of the R-branch occurs, resulting in the molecules “sticking” on the lower vibrational levels, whereas in the case of the ν 8 mode, it is the P-branch that gets excited so that the molecules become easy to raise to high-lying vibrational levels.