Energy transfer in the 1A u state of glyoxal. III. Deuterium effects

Abstract

Collision‐free lifetimes and collisional quenching rate constants are reported for a number of single vibrational levels of glyoxal‐d₂ (¹A_u) and glyoxal‐hd (¹A^″) and are compared with previous results for glyoxal‐h₂. There was some success in correlating the dependences of collision‐free decay rates on specific vibrational level and on isotopic substitution with the predictions of intramolecular, nonradiative decay theory. There are strong isotope effects on the collision‐free lifetimes, but the rate constants for collision depopulation of a vibronic level, which increase sharply with energy in the excited state, are strikingly isotope independent. The increase is believed to be primarily a result of increased intersystem crossing rate and is compared with a mixed state model proposed by Freed.