The Rotational Spectrum of Monothioformic Acid. I. cis-and trans-HC(:O)SH1,2

Abstract

Abstract The rotational spectra of the two abundant isomers of monothioformic acid, cis- and trans- HC(:O)SH, have been assigned in the frequency region 8 -250 GHz. Over 90 a-type transitions and over 60 b-type transitions have been measured for each rotamer. The a-type transitions belong to the qRK , qQ1, qQ2, qQ3 and qQ4 branches and the b-type absorption lines encompass the Ka = 1 - 0, 2 - 1, 3 - 2, 4 - 3 and 5 - 4 rotational sub-bands. The rotational constants and all quartic and sextic centrifugal distortion constants have been determined for each rotamer using Watson's reduced Hamiltonian. In addition to the measured line positions the frequencies of some selected low-J transitions, not observed in this work but of potential astrophysical interest, have been listed as an aid in the interstellar search for monothioformic acid.