SUBMILLIMETER-WAVE SPECTRUM OF H2SE - THE EVIDENCE OF FOURFOLD CLUSTERING OF ROTATIONAL LEVELS

The spectra of H280Se and H278Se were investigated in the region 300-650 GHz including transitions with high rotational excitation up to J = 20, K-1 = 20. The effect of fourfold clustering of rotational energy levels was observed and interpreted as a critical phenomenon. Very strong distortion of line strengths was also found for rotational transitions in the region of critical phenomena. The measured frequencies were fitted, together with available MW data and IR ground state combination differences, in the modified Watson Hamiltonian and the sets of rotational and centrifugal distortion constants were obtained. © 1992.