The electronic emission spectrum of triatomic hydrogen. IV. Visible bands near 5800 Å and infrared bands near 3950 cm−1

Abstract

In addition to the H3 and D3 bands previously analysed a strong and extensive band was observed near 5800 Å consisting of a large number of irregularly spaced sharp lines. This band can only be accounted for by transitions from the states derived from a 3d electron (2A1, 2E″, 2E′) to the 2p[Formula: see text] state which is also the lower state of the [Formula: see text] band at 6025 Å (paper I). The complexity of the spectrum arises from the interaction among the three component states brought about by uncoupling of the 3d electron from the symmetry axis, together with the perturbation of these states by the 3p[Formula: see text] state (the upper state of the diffuse [Formula: see text] band at 5600 Å). The 3d group of states emits also to the 3p2E′ state, giving rise to an infrared band at 3950 cm−1. The analysis of both the infrared and the visible band was carried out by means of an appropriate Hamiltonian written in terms of the rotational angular momentum R and the electronic orbital angular momentum L. On this basis the great majority of the lines have been assigned and sets of observed and calculated rotational levels have been evaluated. The agreement between observed and calculated levels, while good enough to leave no doubt in the electronic assignments, is not as good as might have been expected, most probably because of perturbations by vibrational levels of 3p2E′. These vibrational levels are not sufficiently well known and therefore cannot easily be included in the computation. Effective constants, for both H3 and D3, for the 3d group of states as well as the perturbing 3p[Formula: see text] state, have been evaluated. For several of these constants the ratio of the values for H3 and D3 deviates considerably from the theoretical ratio, suggesting a strong influence of additional perturbations.