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The relaxation of the highly vibrationally excited CO (v=1-8) by CO-2 is studied by time_resolved Fourier transform infrared emission spectroscopy (TR FTIR). 193 nm laser photolysis of the mixture of CHBr-3 with O-2 generates the highly vibrationally excited CO(v) molecules. TR FTIR records the intense infrared emission of CO(v→v-1). 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 CO 2 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 CO 2. For the lower vibrational states of CO, the vibrational energy transfers preferentially to the υ-3 mode of CO 2. For the higher levels, the major quenching channel changes to the vibrational energy exchange between CO(v→v-1) and the υ-1 mode of CO 2.