Nonadiabatic Ab initio multichannel quantum defect theory applied to absolute experimental absorption intensities in...

The positions and intensities of the Q(N) (N = 1-4) X1 Sigma(g)+ --> nppi1 Pi(u)- (n = 2 to approximately 30) absorption transitions of H2 have been calculated by multichannel quantum defect theory. The computations are based on the quantum chemical ab initio clamped nuclei potential curves and absorption dipole transition moments for n = 2-4 of Wolniewicz and Staszewska (J. Mol. Spectrosc. 2003, 220, 45). The resulting Einstein spontaneous Einstein A coefficients are in good agreement with those derived from the absolute intensity measurements of Glass-Maujean et al. (Mol. Phys. 2007, 105, 1535). The results reveal widespread vibronic intensity perturbations in the Q(N) Rydberg series, whereas the line frequencies are comparatively little affected by nonadiabatic effects.