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 S-1 2(2)4(3) and 2(3)4(1) 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 K-a = 6 for v = 0. Such high-K-a levels are believed to be the result of contributions from the S-0 groundstate surface at energies where the S-0 and T-1 radical pathways compete. (C) 1997 Published by Elsevier Science B.V.