Nonadiabatic representation for the i 3Π-g-j 3Δ-g complex of H2 and D2

The full ab initio nonadiabatic approach was successfully applied to calculate energy, radiative, and magnetic properties of strong L-uncoupling i ³Π^-_g and j ³Δ^-_g states of molecular hydrogen isotopes, for the first time, to our knowledge. The concomitant electronic L-uncoupling matrix elements between the i ³Π_g and j ³Δ_g as well as the i ³Π_g-b ³Σ⁺_u, i ³Π_g-e ³Σ⁺_u, i ³Π_g-c ³Π_u, and j ³Δ_g-c ³Π_u transition dipole moment functions were revised by using an electronic full configuration-interaction calculation together with highly accurate ab initio adiabatic potentials taken from the literature. The ab initio results were borne out by quantum-defect theory estimates. Nonadiabatic rovibronic eigenvalues and eigenfunctions for the bound i ³Π^-_g-j ³Δ^-_g perturbation complex were derived by direct numerical solutions of the two channel-coupling radial equations. The theoretical term values of the complex for H₂ and D₂ agree with their experimental counterparts within 0.5-1.5 cm^-1. For the overwhelming majority of levels, the calculated magnetic g factors coincide with the measured ones within their experimental accuracy. The predicted rovibronic transition probabilities to the lower-lying b ³Σ⁺_u, c ³Π_u, and e ³Σ⁺_u states completely resolve perplexing problems of the radiative data in experiments: lifetimes, branching ratios of fluorescence decay to the b ³Σ⁺_u and c ³Π⁺_u states, and the intensity distribution in rotational structure of the i ³Π^-_g-j ³Δ^-_g-->c ³Π^+/-_u transitions.