First Principles Calculations

Calculations of the linestrengths and transition frequencies of the forbidden pure rotational spectrum of Hz in the vibrationally excited v2 state are presented. These transitions occur in the far-infrared region, and their observation may be complicated by vi u2 difference transitions. Examples of these are also given. Forbidden rovibrational transition frequencies and linestrengths have also been calculated in the frequency range 2000-3000 cm -I. The bands ( v2 + Y, ) Ye and (2~~ (I = 0) + V, ) 2~ (1 = 2) are found to be particularly strong. Possible phenomenological explanations for the observed line intensities are discussed. Two routes to obtaining the energy levels of the V, manifold of Hi are suggested. o 1990 Academic press, hc.