Synergistic effects of exposure of surfaces of ionic crystals to radiation and water

We present studies of the consequences of simultaneous exposure of inorganic single crystals to radiation and water. The first case consists of a biomineral, CaHPO4•2H2O (brushite), which is a wide band gap, hydrated inorganic single crystal. We examine the laser-induced ion and neutral emissions accompanying 248 nm excimer laser radiation. Both types of emission are several orders of magnitude higher following exposure to 2 keV electrons at current densities of 200 μA/cm2 and doses of 102 to 103 mC/cm2. We show that the enhancements in emission are strongly correlated with e-beam induced morphology changes (including recrystallization) on this unusual surface. We then examine similar effects on “dry” crystals such as NaCl and NaNO3 which are exposed to 10−5 Pa partial pressures of H2O. Again dramatic enhancements in radiation induced emissions are exhibited along with the generation of unique morphological structures with nanometer scale dimensions.