Defect Formation, Surface Metalization, and Desorption of Excited Atoms Induced by Ion Bombardment of Alkali-Halides

This dissertation presents the first detailed investigation of defect formation, surface metalization in alkali-halide crystals, and desorption of excited atoms induced by ion bombardment of alkali-halide crystals. F -center and F-center clusters are identified in NaF and LiF crystals bombarded by 20 keV ions at room temperature. The concentration of F centers is found to be proportional to the square root of the ion doses. The current dependence of excited sodium or excited fluorine atoms ejected from a NaF crystal strongly indicates both electronic sputtering and collisional cascade processes are involved in the desorption of excited sodium or fluorine atoms induced by ion bombardment. Anomalous behavior in the desorption of sodium atoms in the first excited states as a function of temperature compared to other highly excited atoms imply that the electron transfer processes is an essential factor to the measured photon yields. Both dependencies are well fitted by a proposed model based on electron transfer mechanism. The experiment results on work function measurements of ion-bombarded NaF or LiF crystals clearly show that ion bombardment of alkali-halide crystals results in surface metalization. The correlation between the work function and the yield of sodium D lines strongly indicates electron transfer processes are an important factor in photon emission from excited atoms.