DOPPLER-FREE STARK SPECTRA OF THE 4(0)(1)-BAND OF THE (A)OVER-TILDE(1)A(2)-(X)OVER-TILDE(1)A(1) SYSTEM OF THIOFORMALDEHYDE

Doppler-free Stark Spectra of the 4(0)(1) band of the (A) over tilde 1 (2)(A)-(X) over tilde(1)A(1) system of thioformaldehyde have been obta ined using the technique of intermodulated fluorescence. Fully resolve d m structures have been obtained for ten lines with linewidths of abo ut 5 MHz. The a component of the dipole moment of the molecule in the excited state is 0.815+/-0.020 Debye, but values from 0.77 D to 0.93 D have been derived from some of the Stark patterns depending on the de gree of mixing of the excited-state levels with high rovibronic levels of the ground state.