SEMIRIGID BENDER DETERMINATION OF THE QUASI-LINEAR BENDING POTENTIAL-ENERGY FUNCTION OF HNCS FROM THE GROUND-STATE ROTATIONAL SPECTRA

The semirigid bender Hamiltonian of Bunker and Landsberg (J. Mel. Spec trosc. 67, 374-385, 1977) is used to study the ground state microwave, millimeter-wave, and far-infrared spectroscopic data for HNCS and its isotopomers. The results of the nonlinear least-squares fitting inclu de a determination of the geometry of the molecule and of the in-plane HNC bending potential energy function. The fitted barrier to linearit y is found to be approximately 990 cm(-1), while consideration of the rotation structure of the v(4) = 1 state implies that the barrier lies near 900 cm(-1). With an estimated uncertainty of about 200 cm(-1) th ese values are in reasonable agreement. (C) 1994 Academic Press, Inc.