Highly accurate diatomic centrifugal distortion constants for high orders and high levels

Abstract

Abstract The problem of the computation of the Centrifugal Distortion Constants (CDC) related to a diatomic potential is considered. The analytical expressions obtained from a reformulation of the Rayleigh‐Schrödinger perturbation theory are used [Kobeissi et al., J. Mol. Spectrosc. , 138 , 1 (1989)]; these are e n +1 = 〈Φ 0 R Φ n 〉 – Σ e m 〈Φ 0 Φ n − m 〉 where R = 1/ r 2 , Φ 0 = ψ v is the vibrational wave function (corresponding to the given energy E v = e 0 ) and Φ 1 , Φ 2 ,…, are the “rotational corrections” to Φ 0 , solutions of the rotational (nonhomogeneous) Schrödinger equations. These equations are integrated by using a recent integrator using a powerful local control allowing (for Φ 0 ) a high accuracy. The integrals are computed by using another powerful technique tailored for matrix elements between numerical wave functions [Kobeissi et al., J. Comp. Chem. , 10 , 358 (1989)]. This numerical treatment is applied to the model Lennard‐Jones potential and to the RKR potential of the I 2 ground state. In both applications the CDC are computed up to e 6 = N v and e 7 = O v (these two are published for the first time), and up to the dissociation [up to v = 23 for the Lennard–Jones potential, and to v = 108 for the X Σ – I 2 (RKR) potential]. © 1992 by John Wiley & Sons, Inc.