Production of Atomic Hydrogen and Deuterium from H$_{2}$, D$_{2}$ and HD Photodissociation

We have measured the production of Ly$\alpha $ and H$\alpha $ fluorescence from atomic H and D resulting from the photodissociation of H$_{2}$, D$_{2}$ and HD by linearly-polarized photons with energies between 22 and 64 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. Comparison between the current relative cross section results, previous absolute and relative experimental results and the available theory show only qualitative agreement. We will discuss the various systematic effects which affect this and other types of synchrotron-based measurements in this energy range. Support provided by the NSF (Grant PHY-0653379), DOE (LBNL/ALS) and ANSTO (Access to Major Research Facilities Programme).