  Thioformaldehyde is an abundant molecule in various regions of the
interstellar medium. However, available laboratory data limit the accuracies of
calculated transition frequencies in the submillimeter region, in particular
for minor isotopic species. We aim to determine spectroscopic parameters of
isotopologs of H2CS that are accurate enough for predictions well into the
submillimeter region. We investigated the laboratory rotational spectra of
numerous isotopic species in natural isotopic composition almost continuously
between 110 and 377 GHz. Individual lines were studied for most species in two
frequency regions between 566 and 930 GHz. Further data were obtained for the
three most abundant species in the 1290-1390 GHz region. New or improved
spectroscopic parameters were determined for seven isotopic species.
Quantum-chemical calculations were carried out to evaluate the differences
between ground state and equilibrium rotational parameters to derive
semi-empirical equilibrium structural parameters. The spectroscopic parameters
are accurate enough for predictions well above 1 THz with the exception of
H2(13)C(34)S where the predictions should be reliable to around 700 GHz.
