  An investigation of the rotational spectrum of the interstellar molecule
thioformaldehyde between 110 and 377 GHz through a pyrolysis reaction revealed
a multitude of absorption lines assignable to H$_2$CS and H$_2$C$^{34}$S in
their lowest four excited vibrational states besides lines of numerous
thioformaldehyde isotopologues in their ground vibrational states reported
earlier as well as lines pertaining to several by-products. Additional
transitions of H$_2$CS in its lowest four excited vibrational states were
recorded in selected regions between 571 and 1386 GHz. Slight to strong
Coriolis interactions occur between all four vibrational states with the
exception of the two highest lying states because both are totally symmetric
vibrations. We present combined analyses of the ground and the four interacting
states for our rotational data of H$_2$CS and H$_2$C$^{34}$S. The H$_2$CS data
were supplemented with two sets of high-resultion IR data in two separate
analyses. The $v_2 = 1$ state has been included in analyses of Coriolis
interactions of low-lying fundamental states of H$_2$CS for the first time and
this improved the quality of the fits substantially. We extended furthermore
assignments in $J$ of transition frequencies of thioketene in its ground
vibrational state.
