Non-Born-Oppenheimer calculations of the rovibrational spectrum of H₂excited to the second rotational level

Quantum mechanical, non-relativistic, non-Born-Oppenheimer (non-BO) calculations are performed for the rovibrational spectrum of H₂excited to the second rotational level. The non-BO wave functions of the considered states are expanded in terms of all-particle explicitly correlated Gaussian functions. The dissociation energies and rovibrational transition energies are calculated and compared with experimental values and values obtained in calculations performed by others. The average interparticle distances are calculated and compared with the corresponding values for HD. They show that H₂is a more “diffuse molecule”. The nuclear-nuclear correlation functions are calculated and plotted to visualize the “non-BO molecular structure” of H₂.