WF11		15min4:34

JIAN TANG AND SHUJI SAITO, Dept. of Molecular Structure, The Graduate University for Advanced Studies and Institute for Molecular Science, Okazaki 444, Japan.

The microwave spectra of the HCCS and DCCS radicals (X²_i) in both CCS(₅) and H(D)CC(₄) bending vibrational states were observed in the frequency range of 160--400 GHz with a dc discharge of the C₂H₂ (or C₂D₂) and CS₂ gas mixture. The rotational transition series for the vibronic ²_5/2,3/2(₅), µ, \kappa²(₅), ²_3/2(2₅), ²_ 5/2(₄) and µ²(₄) states were assigned. The analysis of the effective molecular constants showed that the values of the \gamma_eff constants of the vibronic µ,\kappa² states were different from each other by 2--3 GHz, which could not be explained by the up-to-date Renner-Teller theory for a single bending mode.

This abnormal Renner-Teller effect may be understood by a new vibronic interaction theory, which was developed by us to consider the cross vibronic interaction between the two bending modes.