Molecular constants for the I1Πg and J1Δg states of the 3d complex in H2, HD,and D2

The experimental rovibronic energies of the 3dπI¹Π_g^? and 3dδJ¹Δ_g^? states of H₂ and D₂ (v = 0–4 and N = 1–11) have been fitted by rovibronic constants, including L-uncoupling through constants B_v^ΠΔ and D_v^ΠΔ. Comparison of the constants obtained for H₂ and D₂ yields information on the Born-Oppenheimer and adiabatic electronic energies T_e^BO and T_e^AD, and on the diagonal corrections for nuclear motion. T_e^BO derived from experiment for the I¹Π_g state lies 2 cm^?1 below the ab initio calculation of Ko?os and Rychlewski (J. Mol. Spectrosc., 66, 428–440 (1977). The nuclear mass dependence of the ω_e and B_e values in H₂ and D₂ deviates from simple isotope relationships but agrees with expectations based on the R-dependence of the diagonal corrections for nuclear motion through the term $\text{〈L}{}^2\text{?2}\text{Λ}{}^2\text{〉}\text{2μR}{}^2$, i.e., $\text{+2}\text{μR}{}^2$ for 3dπ and $\text{?1}\text{μR}{}^2$ for 3dδ.