A variational method for the calculation of spin–rovibronic energy levels of any triatomic molecule in an electronic triplet state

Abstract

The triatomic spin-rovibronic variational code RVIB3 has been extended to include the effect of two uncoupled electrons, for both ³Σ^- and ³Π (Renner–Teller) electronic states. The spin–orbital–rotational kinetic energy is included in the usual way, via terms (

). The phenomenological terms

are introduced to reproduce the spin–orbit and spin–spin splittings, respectively. Calculations are performed to evaluate the spin–rovibronic energy levels of CCO

and CCO

for which the Born–Oppenheimer potentials are derived from high-accuracy ab initio calculations.

Acknowledgments

We would like to thank the University of Bologna and US Office of Naval Research for continued support of this work under grant No. N00014-01-1-0809. SC acknowledges the award of a HPC-Europa grant to carry out part of this work at the CINECA Supercomputer Centre (Casalecchio di Reno, Italy). RT also acknowledges H.-J. Werner and P.J. Knowles for providing him with access to the MOLPRO code.