The Potential Energy Function of CS2 Derived from Rovibrational Data

✍ Scribed by M. Kolbuszewski; P.R. Bunker; P. Jensen

• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 437 KB
• Volume: 170
• Category: Article
• ISSN: 0022-2852
• DOI: 10.1006/jmsp.1995.1062

✦ Synopsis

We have derived the potential energy surface up to (5000 \mathrm{~cm}^{-1}) of the (\dot{X}^{1} \Sigma_{\mathrm{g}}^{+})electronic ground state of (\mathrm{CS}{2}) by fitting to experimental rotation-vibration data using a variational approach. We use the Morse oscillator rigid bender (MORBID) Hamiltonian, with a basis set composed of Morse oscillator and rigid bender eigenfunctions, to fit 40 vibrational term values and 40 rotational levels with (J<6). We obtain a root mean square deviation of (2.12 \mathrm{~cm}^{-1}) for the vibrational energy spacings. In determining the potential energy function we obtain the equilibrium bond length (R{c}) (=1.5549 \pm 0.0040 \AA), and predict the position of (22 l=0) vibrational levels, below (5000 \mathrm{~cm}^{-1}), that have not been observed. The large masses of the terminal sulphur atoms lead to difficulties in basis set convergence at high energies because of large bend-stretch and stretch-stretch coupling in the kinetic energy operator, and for this reason we only fit to levels up to (5000 \mathrm{~cm}^{-1}); these are converged to better than (1 \mathrm{~cm}^{-1}). This difficulty with convergence does not occur for hydrides such as (\mathrm{CH}{2}, \mathrm{H}{2} \mathrm{O}, \mathrm{H}{2} \mathrm{~S}), and (\mathrm{H}{2} \mathrm{Se}), but is a general problem in heavy-light-heavy triatomic molecules. It is particularly difficult to fit the (l=1) vibrational energies. (c) 1995 Academic Press. Ins.