High-resolution spectroscopy of molecular hydrogen in the extreme ultraviolet region

We report high-resolution spectroscopy of the D¹Πᵤ, D^''¹Πᵤ, and B^''¹Σᵤ⁺ states in H₂, HD, and D₂, performed in absorption in the vicinity of 83 nm. Predissociative widths as narrow as 0.3 cm^-1 have been measured, and profile analyses based on the theory of Fano are performed on these predissociated states. The importance of overlap integrals in the predissociation of B^'' is shown, and the absorption cross section σ=(7.2±0.7)×10^-16 cm² for the B^''←X(2,0) is determined. Anomalous behavior observed in the $D(v=5)$ states of D₂ is analyzed in terms of an accidental perturbation by the D^''(v=0) states.