ChemInform Abstract: Thioformaldehyde Single Rotational Level Photophysics: Longer Than Radiative Lifetimes and Reduced Fluorescence Yields in the Isolated Molecule.

Abstract

Single rotational level fluorescence lifetimes and relative fluorescence quantum yields have been measured under collision‐free conditions for a variety of rotational levels in the 41 vibrational state of S1 H2CS. About half of the rotational levels studied decay with a radiative lifetime of ≊170 μs. Other levels decay with lifetimes longer than the radiative lifetime and these states correlate with perturbations observed in the spectrum, as detected by Doppler‐limited laser‐induced fluorescence and sub‐Doppler intermodulated fluorescence techniques. The levels coupled to T1 and most of the levels coupled to S0 have relative fluorescence yields near unity. A few levels in S1 show reduced quantum yields of fluorescence which persist at pressures as low as 5×10−7 Torr. A sequential coupling model is proposed to qualitatively account for the observed excited state dynamics of these levels.