Variational Evaluation of the HSSH FIR Transitions: The Anomalous K-Doubling

✍ Scribed by M.L. Senent; Y.G. Smeyers; R. Domı́nguez-Gómez; A. Arroyo; S. Fernández-Herrera

• Publisher: Elsevier Science
• Year: 2000
• Tongue: English
• Weight: 182 KB
• Volume: 203
• Category: Article
• ISSN: 0022-2852
• DOI: 10.1006/jmsp.2000.8177

✦ Synopsis

The roto-torsional energy levels of HSSH and DSSD up to J ϭ 20 are evaluated variationally with a Hamiltonian expressed in terms of internal coordinates. The kinetic and potential parameters are derived from ab initio calculations with full optimization of the geometry. The calculated levels are employed for the determination of the centrifugal distortion constants. HSSH is a near-prolate symmetric rotor. The most stable C 2 conformer, calculated with MP4(SDQ)/cc-pVQZ, exhibits a 90.55°dihedral angle. For J ϭ 0, the lowest energies of HSSH and DSSD are 413.4876 cm Ϫ1 (n ϭ 1), 798.0304 cm Ϫ1 (n ϭ 2) and 1151.5773 cm Ϫ1 (n ϭ 3), and 304.3185 cm Ϫ1 (n ϭ 1), 594.2919 cm Ϫ1 (n ϭ 2), and 869.3508 cm Ϫ1 (n ϭ 3), respectively. For J ϭ 60, the ab initio calculations allow the reproduction of the anomalous type-K doubling predicted with perturbation theory.