HOLGER S. P. MÜLLER, CHRISTIAN P. ENDRES, STEPHAN SCHLEMMER, I. Physikalisches Institut, Universität zu Köln, 50937 Köln, Germany; ATSUKO MAEDA, IVAN MEDVEDEV, ERIC HERBST, MANFRED WINNEWISSER, FRANK C. DE LUCIA, Department of Physics, The Ohio State University, Columbus, OH 43210, USA.
Rotational spectra of vibrationally excited states of H2CS below 1500~cm-1 have been obtained by long-path absorption spectroscopy between 120 and currently 670~GHz. The highest Ka accessed range from 9 to 12 and correspond to combined rotational and vibrational energies of almost 2400~cm-1. The v4 = 1 (990.185~cm-1) and v6 = 1 (991.019~cm-1) states are almost degenerate and undergo very strong Coriolis interaction (| 46a| = 0.5148) which causes Ka > 0 to be mixed completely. The v3 = 1 state is at 1059.204~cm-1 and the first order Coriolis terms are smaller (| 36c| = 0.2743 and | 34b| = 0.0574) so that perturbations are more local. Finally, the v2 = 1 state (1455.496~cm-1) is comparatively far away from the three lower states, but there is a large coupling term with v4 = 1: | 24b| = 0.8555. Because of the large energy difference, only higher order effects are pronounced in this case. The initial assignments were greatly facilitated by previous infrared studies on 4, 6, and 3 as well as on 2. The results from these as well as previous and present pure rotational studies on the ground vibrational state were considered in the global fit. The very satifactory fit required a modest number of vibrational corrections for the four vibrationally excited states and a comparatively large number of Coriolis interaction terms.