Analysis of the Microwave Spectrum of Tricarbon Oxide Sulfide,

In memoriam Professor Dr. Werner Zeil The microwave spectrum of tricarbon oxide sulphide (3-thioxo-l,2-propadiene-l-one), 0 = C = C = C = S , has been measured in the frequency range from 8 to 40 GHz and includes vibrational satellite lines arising from the vibrational manifold of the lowest-lying doubly-degenerate bending mode i>7. The method of analysis followed the theory of rotation-vibrational interaction as developed by Nielsen and Amat. The spectroscopic constants Bv and Dv as well as several vibrationrotational constants for each vibrational state vy = 0 to 7, = 1 and vq = 1 were determined with the aid of a newly written least squares program. The program structure relies on the correlation of the symmetry classification of energy levels in linear and bent molecules, and follows closely the analysis of asymmetric rotor spectra. From the «»vibrational spectrum of C3OS in excited states of vy up to t'7 — 7 and 1 — 6 the sign and magnitude of the effective vibrational anharmonicity constant xitit were determined. The interpretation of these results yields the information that in C3OS the potential function describing the two-dimensional oscillator of the vj bending mode is very harmonic and does not contain a perturbing hump. The dynamic behaviour of C3OS, a classical example of a linear molecule, is thus in sharp contrast to the quasilinear behaviour of C3O2 •