Observations of laser cooling by resonant energy transfer in CO2 - N2 mixtures

The effects produced by absorption of an intensity modulated CO2 laser in CO2‐N2 mixture are investigated here by means of the photothermal deflection technique. The deflection signal arises from CO2 molecule deactivation and energy transfer from CO2 to N2 molecules, which are responsible for heating and cooling the mixture, respectively. The dominant mechanism is determined by the pressure of the gas mixture, which, in turn, affects the CO2 molecule lifetime. A theoretical model based on rate equations for the CO2‐N2 system is presented, in which the deflection signal is given as a function of the excited molecule populations. The theoretical predictions are shown to be in reasonable agreement with the experimental results.