Nonadiabatic energy corrections for the vibrational levels of the B and B′ 1Σ+u states of the H2 and D2 molecules

Publisher Website
Google Scholar
Abstract
The variation-perturbation method is used to calculate the nonadiabatic energy shifts of all bound vibrational levels of the B 1Σ+u and B′ 1Σ+u states of H2 and D2 from the best available ab initio wave functions. In H2 the nonadiabatic energy shifts lie between extremes of −0.31 cm−1 (B,v=0) and −5.07 cm−1 (B,v=30) and, as expected, the shifts in D2 are one half as large as the ones in H2 at the same vibrational energies. The resulting nonadiabatic vibronic term values of the B state lie ≂1.1±0.1 cm−1 above the experimental ones over a wide range of vibrational excitation energies, in H2 as well as in D2. This indicates that all nuclear-mass dependent contributions to the vibronic energies as well as the potential curve of the B state are now accounted for quite accurately. In the B′ state the remaining discrepancies with experimental term values depend markedly on vibrational excitation, and a large part of them is nuclear mass dependent, while the remaining error of the electronic energy calculation for the B′ state seems to be as small as the one for the B state.