Rotationally resolved high-resolution spectrum of the S-1-S-0 transition of jet-cooled thioanisole

The rotationally resolved high-resolution fluorescence excitation spectrum of the 0-0 band in the S-1 <- S-0 electronic excitation of thioanisole was observed using the techniques of a collimated supersonic jet and a single-mode ultraviolet laser for the first time. High accurate rotational constants for the S-0 and the S-1 states have been determined by precisely calibrated transition energies of about 1000 assigned rotational lines. The molecular structure of thioanisole has been estimated by high-level MO calculations. The planarity of thioanisole in the S-0 and the S-1 states was also demonstrated clearly. The lifetime of the S-1 state was estimated to be 2.0 ns from the observed line width. This line shape did not change with the magnetic field of 1 Tesla, suggesting that the main radiationless process should be internal conversion to the S-0 state.