HCO rotational excitation in the photoinitiated unimolecular decomposition of H2CO

The unimolecular decomposition of H2CO via the H + HCO radical channel has been examined by photoexcitation of the S1 2243 and 2341 vibrational bands (31500-31855 cm−1). The H-atom translational energy distributions, obtained by using the high-n Rydberg time-of-flight technique, reflect the HCO internal energy distributions and reveal rotational excitation as high as Ka = 6 for ν = 0. Such high-Ka levels are believed to be the result of contributions from the S0 ground state surface at energies where the S0 and T1 radical pathways compete.