NEAR-THRESHOLD DYNAMICS AND DISSOCIATION-ENERGY OF THE REACTION H2CO-]HCO+H

The state-to-state dynamics of the gas phase reaction H2CO (u, J, K-a, K-c) + hv --> H + HCO (v, N, S, K-a, K-c have been explored in a supe rsonic free jet. Seven rotational states within the 2(1)4(3) vibration al level of H2CO were excited and the population distribution of the H CO (v = 0, N, S, K-a, K-c) product states measured. The distributions are constrained severely by the available energy in the reaction with the lowest H2CO state producing HCO in only three rotational states. C areful matching of the H2CO and HCO energy levels leads to an estimate of the dissociation energy of the above reaction of 30328.5 +/- 0.5 c m(-1), which leads us to an estimate of the standard heat of formation of the formyl radical of Delta H-f(0) +/- 42.5 +/- 0.5 kJ mol(-1).