Dissociation rates for individual eigenstates of S formaldehyde: Fluctuations and barrier height

Abstract

Spectra of S0 D2CO rovibronic states near the dissociation threshold have been taken with a new method by monitoring S1 lifetime while Stark shifting an S1 level through the S0 manifold. An order of magnitude variation in the unimolecular dissociation rate and in the S1–S0 vibronic coupling matrix element is observed among S0 levels within a 0.2 cm−1 energy range. These individual molecular eigenstates exhibit distinctive chemical properties. Dissociation rates averaged over an energy range of a few cm−1 vary smoothly with energy and give a barrier height of 78.0–81.1 kcal/mol for H2CO→H2+CO.