Vibrational relaxation by reversible intersystem crossing

Abstract

The time- and energy-resolved fluorescence spectra of CO obtained under selective excitation of the A 1Π (υ′ = 1) level have been studied. The apparent vibrational relaxation in the singlet manifold is shown to be mainly due to the three-step process: the singlet → triplet crossing from υ′ = 1 level, vibrational relaxation in the triplet manifold and reverse crossing to the A 1Π (υ′ = 0) level. The decay form may be fitted by assuming the relaxation rate constants in triplet (and singlet) manifolds of the order of 10 5 s −1 Torr −1 i.e. smaller by one order of magnitude than previously proposed.