Paper detail

The D^1Π state of HD and the mass scaling relation of its predissociation widths

Absorption spectra of HD have been recorded in the wavelength range of 75 to 90 nm at 100 K using the vacuum ultraviolet Fourier transform spectrometer at the Synchrotron SOLEIL. The present wavelength resolution represents an order of magnitude improvement over that of previous studies. We present a detailed study of the D^1Π- X^1Σ^+_g system observed up to v'=18. The Q-branch transitions probing levels of Π^- symmetry are observed as narrow resonances limited by the Doppler width at 100 K. Line positions for these transitions are determined to an estimated absolute accuracy of 0.06 cm^{-1} . Predissociation line widths of Π^+ levels are extracted from the absorption spectra. A comparison with the recent results on a study of the D^1Πstate in H_2 and D_2 reveals that the predissociation widths scale as μ^-2J(J+1), with μthe reduced mass of the molecule and J the rotational angular momentum quantum number, as expected from an interaction with the B'^1Σ_u^+ continuum causing the predissociation.