High orbital angular momentum states in H2 and D2. II. The 6h–5g and 6g–5f transitions

A group of lines accompanying the first line of the Pfund series of the H atom has been observed by Fourier transform infrared spectrometry. The lines are due to transitions in molecular hydrogen of a nonpenetrating Rydberg electron possessing a high-orbital angular momentum, which is coupled only loosely to the vibrations and rotations of the H+2 core. Lines belonging to the 6h–5g and 6g–5f (v=0–3) transitions of H2 have been identified. The identifications are based on a calculation of the spectrum from first principles by multichannel quantum defect theory. The interaction between the nonpenetrating electron and the core was evaluated in terms of the permanent and induced molecular moments of H+2 as calculated by Bishop and collaborators. The analogous transitions in D2 have also been observed and assigned.