Optical–optical double resonance probe of the dark state of thiophosgene in supersonic free jet

One-photon excitation of the S0 (X̃) thiophosgene to the S1 (Ã) state, followed by photodepletion of the S1→S0 fluorescence by Sn (n=2,3)←S1 excitation, by another photon, reveals the presence of a dark S3(C̃) state in the vicinity of the B̃1A1(ππ*),S2, state. The measured polarization and the vibrational structure of the C̃←Ã absorption are consistent with the C̃ state being the 1B2(nσ*) state, predicted by the CASSCF calculations of Strickler and Gruebele [Chem. Phys. Lett. 349 (2001) 137]. The dominant decay channel of the C̃1B2(nσ*) state is shown to be the direct internal conversion to the X̃1A1 state.