Isotope Effects on Franck—Condon Factors. VII. Vibrational Intensity Distribution in the H2 Lyman, H2 Werner, O2 Schumann—Runge, N2 First Positive, N2 Vegard—Kaplan, and LiH (A—X) Systems Based on RKR Potentials

Abstract

Franck—Condon factors, based on Rydberg—Klein—Rees (RKR) potential functions, were computed for the H₂ and D₂ Lyman and Werner, ¹⁶O₂ and ¹⁸O₂ Schumann—Runge, ¹⁴N₂ and ¹⁴N¹⁵N first positive and Vegard—Kaplan, and ⁷LiH and ⁷LiD (A—X) band systems. While the vibrational intensity distribution within several band series differs considerably from that previously computed using Morse potentials, the isotope effect is very similar by both methods. Only for the hydrogen Lyman bands, even the isotope effect on Franck—Condon factors is markedly different by the two methods. The isotope ratio of Franck—Condon factors, _q(⁷LiH)/_q(⁷LiD), in a given band progression (e.g., v″=3), oscillates between very large (10⁴) and very small (10⁻²) values at the minima between the locus of the Condon parabolas. The isotope effect on r centroids is negligible for transitions of oxygen and nitrogen molecules, but amounts to several percent for transitions of hydrogen and lithium hydride molecules. For the ¹⁶O₂ Schumann—Runge absorption bands, the variation of the electronic transition moment R_e with internuclear distance r is represented by R_e=const(1–0.70r).