Distribution of vibrational states of CO2 in the reaction O((1)D) + CO2 from time-resolved fourier transform infrared emission spectra.

A mixture of O(3) and CO(2) was irradiated with light from a KrF laser at 248 nm; time-resolved infrared emission of CO(2) in the region 2000-2400 cm(-1) was observed with a Fourier transform spectrometer. This emission involves one quantum in the asymmetric stretching mode (nu(3)) of CO(2) in highly vibrationally excited states. The band contour agrees satisfactorily with a band shape calculated based on a simplified polyad model of CO(2) and a vibrational distribution estimated through a statistical partitioning of energy of approximately 13,000 cm(-1), approximately 3100 cm(-1) smaller than the available energy, into the vibrational modes of CO(2). From this model, approximately 44% and 5% of the available energy of O((1)D) + CO(2) is converted into the vibrational and rotational energy of product CO(2), respectively, consistent with previous reports of approximately 50% for the translational energy. An extent of rotational excitation of CO(2) much smaller than that expected from statistical calculations indicates a mechanism that causes a small torque to be given to CO(2) when an O atom leaves the complex CO(3) on the triplet exit surface of potential energy, consistent with quantum-chemical calculations.