Production of Excited Atomic Hydrogen and Deuterium from HD Photodissociation

We have measured the production of Ly$\alpha $, H$\alpha $, and H$\beta $ fluorescence from atomic H and D for the photodissociation of HD by linearly-polarized photons with energies between 20 and 66 eV. In this energy range, excited photofragments result primarily from the production of doubly-excited molecular species which promptly autoionize or dissociate into two neutrals. Theoretical calculation are not yet available for HD, but comparison between the relative cross sections for H$_{2}$, D$_{2}$ and HD targets and the available theory for H$_{2}$ and D$_{2}$ [1] allow for an estimate of the relative strength of each dissociation channel in this energy range. [1] J. D. Bozek \textit{et al.}, J. Phys. B \textbf{39}, 4871 (2006). Support provided by the NSF (Grant PHY-0653379), DOE (LBNL/ALS) and ANSTO (Access to Major Research Facilities Programme).