HIGH-RESOLUTION ANALYSIS OF THE UPSILON(1)+2-UPSILON(2)-BAND, 2-UPSILON(2)+UPSILON(3)-BAND, 2-UPSILON(1)-BAND, UPSILON(1)+UPSILON(3)-BAND, AND 2-UPSILON(3)-BAND OF (H2SE)-SE-80

High-resolution Fourier transform spectra of monoisotopic (H2Se)-Se-80 have been recorded with a resolution of 7 X 10(-3) cm-1 in the 4210-4850 cm-1 spectral range. Their rovibrational analysis led to an extensive and precise set of rotational levels for the (1 2 0), (0 2 1), (2 0 0), (1 0 1), and (0 0 2) vibrational states of this molecule. To fit these levels satisfactorily it proved necessary to take explicitly into account in the Hamiltonian not only the strong Coriolis and Darling-Dennison interactions coupling the rotational levels of the {(2 0 0), (1 0 1), (0 0 2)} vibrational states and the strong Coriolis interaction coupling the levels of (1 2 0), (0 2 1)}, but also weak interactions linking the rotational levels of these two groups of vibrational states; indeed for J values around 15 and above, there appear crossings between the levels despite the differences in the bandcenters. In this way, all the experimental levels were satisfactorily calculated and a precise set of vibrational energies and rotational and coupling constants was obtained for the five vibrational states (1 2 0), (0 2 1), (2 0 0), (1 0 1), and (0 0 2) of (H2Se)-Se-80 with the following bandcenters: nu0 (nu1 + 2nu2) = 4370.60800 cm-1, nu0 (2nu2 + nu3) = 4377.61844 cm-1, nu0 (2nu1) = 4615.32816 cm-1, nu0 (nu1 + nu3) = 4617.39318 cm-1, and nu0 (2nu3) = 4702.54744 cm-1. (C) 1994 Academic Press, Inc.