Abstract
The vacuum ultraviolet spectra of solid ammonia and ice are found to be shifted to higher frequencies relative to the corresponding vapor spectra by 7000 cm-1. The effects of hydrogen bonding in the ground states of these solids, and the nature of repulsive interactions possible in the excited states are discussed. In methane, which forms a pure van der Waals solid, the spectra of gas and solid are found to be very similar.