Mid- and near-infrared spectra, millimeterwave spectra, and global analysis of (OCSe)-O-16-C-12-Se-80

We have recorded a total of 12 FTIR spectra of monoisotopic (OCSe)-Se-80 in different spectral regions with a resolution (1/maximum optical path diffe rence) between 2.7 and 13.2 x 10(-3) cm(-1). These spectra spanned the rang e from 350 to 7800 cm(-1), many bands being studied with different p x L pr oducts in order to also detect weak hot bands. Altogether 18 band systems c omprising 81 different bands, mostly of Sigma type, were observed and analy zed by means of polynomial expansions in J(J + 1). New rotational transitio ns of vibrationally excited states as high as 2200 cm(-1) with J " 17-25 in the 140-210 GHz and J " 53-58 in the 430-470 GHz millimeterwave regions we re measured with the assistance of predictions by the global fit. This fit was performed using a weighted least-squares procedure and employing the wh ole body of data, and about 100 molecular parameters were determined that d escribe the energy level of (OCSe)-O-16-C-12-Se-80 With statistical accurac y. Improved highly accurate ground state parameters up to sextic centrifuga l distortion terms were obtained by a merge of ground state combination dif ferences and pure rotational data. The v(1), v(2), v(3) polyad interacts an harmonically with the v(1) - 1, v(2) + p, v(3) + q polyads with p + 2q = 4. Moreover, some local crossings with Coriolis interactions between (v(1), v (2), v(3)) and (v(1) - 1, v(2) + 3, v(3) + 1) levels were observed and trea ted perturbationally. (C) 1999 Academic Press.