ROTATIONAL AND VIBRATIONAL-RELAXATION OF THE NU(1) 2NU(2) FERMI DYAD IN CO2 GAS FROM RAMAN-INFRARED DOUBLE-RESONANCE EXPERIMENTS/

Time-resolved Raman-infrared double resonance experiments have been co nducted on CO2 gas in order to determine collisional relaxation rates of energy levels. These total depopulation constants are measured in a three-level double resonance scheme. A pulsed Raman excitation popula tes the studied state over a brief time interval (7 ns). The ensuing c ollisional depopulation of this level is monitored by a continuous pro be CO2 laser whose transition originates in the same level. The transi ent absorption on the probe laser gives the time dependent population behavior. The high selectivity of the lasers allows the study of vibra tional and rotational levels. The relaxation rates, of the (10(0)0) vi brational state and, for the first time, of the J=14-34 rotational lev els of the (02(0)0) vibrational state, have been measured. The derived broadening coefficients have been compared to those calculated by a s emiclassical model.