Mail:
Dept. of Chemistry
Ohio State University
100 W. 18th Ave.
Columbus, OH 43210
Office:
412 CBEC
Email:
herbert@
chemistry.ohio-state.edu
Theoretical details necessary to calculate arbitrary-order correction terms to vibrational–rotational energies and wave functions in Rayleigh–Schrödinger perturbation theory are presented. Since manual derivation of high-order perturbation formulae is not feasible due to the lengthy algebra involved, the commercial computer algebra software Mathematica® is employed to perform the symbolic manipulations necessary to derive the requisite correction formulae in terms of universal constants, molecular constants, and quantum numbers. Correction terms through sixth order for 1Σ diatomic molecules are derived and then evaluated for H2, HD, N2, CO, and HF. It is thus possible, with the aid of computer-generated algebra, to apply arbitrarily high-order perturbation theory successfully to the problem of intramolecular nuclear motion.