The electronic emission spectrum of triatomic hydrogen. II. The perpendicular bands near 7100 Å

The strongest emission bands of H3 and D3 near 7100 Å are shown to be [Formula: see text] bands even though of a somewhat unusual structure. Because of the large width of the lines (the same as those of the 5600 Å [Formula: see text] bands) the only method of analysis is by model bands whose parameters are changed until the best fit between observed and calculated spectrum is obtained. As expected on the basics of the line width the lower state is found to be identical with that of the 5600 Å band, i.e., 2s2A1′, while the upper state is 3p2E′. The band structure of a [Formula: see text] band depends strongly on the value of ζ, the electronic angular momentum. When as in the present case ζ is close to 1, pseudo-branches with a constant N – K form the most characteristic features of the [Formula: see text] band. The ζ value determined here for the 3p2E′ state of D3 is 0.8775 which is very close to the ab initio value of King and Morokuma after the latter has been corrected for quenching by the zero-point vibration as a result of Jahn–Teller interaction. In addition the band structure shows clearly the effects of Λ-type doubling and Λ-type resonance which is made especially large by Jahn–Teller distortion. The final B0 value of D3 in the 3p2E′ state, i.e., B0 = 21.16 cm−1, is smaller than the predicted value (21.61 cm−1) for the ground state of D3+ suggesting that the 3pe′ orbital is anti-bonding in agreement with the predictions of King and Morokuma.