Near threshold dynamics and dissociation energy of the reaction H 2CO → HCO + H

Abstract

The state-to-state dynamics of the gas phase reaction H 2CO ( v, J, K a, K c) + hv → H + HCO( v, N, S, K a, K c) have been explored in a supersonic free jet. Seven rotational states within the 2 14 3 vibrational level of H 2CO were excited and the population distribution of the HCO ( 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 H 2CO state producing HCO in only three rotational states. Careful matching of the H 2CO and HCO energy levels leads to an estimate of the dissociation energy of the above reaction of 30328.5 ± 0.5 cm −, which lead us to an estimate of the standard heat of formation of the formyl radical of ΔH f 0 = 42.5 ± 0.5 kJ mol −1.