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 H_{2}CS below 1500~cm^{-1} have been obtained by long-path absorption spectroscopy between 120 and currently 670~GHz. The highest K_{a} accessed range from 9 to 12 and correspond to combined rotational and vibrational energies of almost 2400~cm^{-1}. The v_{4} = 1 (990.185~cm^{-1}) and v_{6} = 1 (991.019~cm^{-1}) states are almost degenerate and undergo very strong Coriolis interaction (|
_{46}^{a}| = 0.5148) which causes K_{a} > 0 to be mixed completely. The v_{3} = 1 state is at 1059.204~cm^{-1} and the first order Coriolis terms are smaller (|
_{36}^{c}| = 0.2743 and |
_{34}^{b}| = 0.0574) so that perturbations are more local. Finally, the v_{2} = 1 state (1455.496~cm^{-1}) is comparatively far away from the three lower states, but there is a large coupling term with v_{4} = 1: |
_{24}^{b}| = 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.