Fourier transform spectroscopy analysis of the 3 d -triplet complex visible emission spectra of H2

An investigation of the triplet 3d-complex of H2, the g(3d) 3Σ+g, i(3d) 3Πg, and j(3d) 3Δg and the nearby h(3s) 3Σ+g electronic states, has been performed. The 3s,3d→c (2p) 3Π−u visible emission spectra have been obtained with a low pressure discharge lamp and recorded with a Fourier transform spectrometer. Transition wave numbers and rotational energy levels are given for v=0–3 of the four states. An effective Hamiltonian is used to fit the data, which shows the rotational breakdown of the Born–Oppenheimer approximation due to the L-uncoupling effect. The eigenvectors obtained from this model provide considerable insight into the nature of the 3d-complex. Furthermore, the model shows the mixing between the 3d states and the h(3s) 3Σ+g state which is particularly strong for lower v values. Molecular constants, coupling parameters, and term values are also given.