The absorption spectrum of D2 from 1100 to 840 A

The absorption spectrum of D 2 has been studied in absorption at high resolution (0.254 Å/mm) in the region 1100 to 840 Å. The three band systems B 1 Σ u + ← X 1 Σ g + (Lyman bands), B′ 1 Σ u + ← X 1 Σ g + and C 1 Π u ← X 1 Σ g (Werner bands) have been measured right up to the dissociation limit. New improved values of the rotational and vibrational constants in the three upper states have been derived. By comparing the electronic energy differences T c thus obtained with the corresponding values for H 2 fairly precise values for the electronic isotope shifts for the B–X and C–X systems have been determined (+ 2.8 and −7.4 cm −1 respectively). In this connection two gaps in the knowledge of the absorption spectrum of H 2 have been filled: the Lyman bands with ν′ = 5–16 and the Werner bands with ν′ = 0–4 (see Appendix). A detailed comparison is made of the observed vibrational levels and the observed B ν values of D 2 with those derived from ab initio calculations based on the Kotos and Wolniewicz' potential functions. From the observed electronic isotope shift the adiabatic corrections can be estimated near the minimum. For the B state these estimates agree very well with the ab initio calculations. The remaining differences between observation and theory are partly due to lack of convergence of the Born–Oppenheimer calculation, partly to the neglect of nonadiabatic corrections. The convergence error near minimum is estimated to be 5.1 cm −1 for the B state and 1.2 cm −1 for the C state.