The v-v energy transfer of highly vibrationally excited states (I) - Vibrational quenching of CO(v) by CO2

The relaxation of the highly vibrationally excited CO (v = 1-8) by CO2 is studied by time-resolved Fourier transform infrared emission spectroscopy (TR FTIR). 193 nm laser photolysis of the mixture of CHBr3 with O-2 generates the highly vibrationally excited CO(v) molecules. TR FTIR records the intense infrared emission of CO(v-->v - I). The vibrational populations of each level of CO(v) have been determined by the method of spectral simulation. Based on the evolution of the time resolved populations and the differential method, 8 energy transfer rate constants of CO (v = 1-8) to CO2 molecules are obtained: (5.7 +/- 0.1), (5.9 +/- 0.1), (5.2 +/- 0.2), (3.4 +/- 0.2), (2.4 +/- 0.3), (2.2 +/- 0.4), (2.0 +/- 0.4) and (1.8 +/- 0.6) (10(-14) cm(3).molecule(-1).s(-1)), respectively. A two-channel energy transfer model can explain the feature of the quenching of CO(v) by CO2. For the lower vibrational states of CO, the vibrational energy transfers preferentially to the upsilon(3) mode of CO2. For the higher levels, the major quenching channel changes to the vibrational energy exchange between CO(v-->v - 1) and the upsilon(1) mode of CO2