GROUND-STATE AND EXCITED ATOM EMISSION UNDER ION AND ELECTRON BOMBARDMENT OF NaCI AND CaF2

Abstract

The particle emission process for ion bombardment and electron bombardment of NaCl and CaF2 using high resolution optical spectroscopy and Laser Induced Fluorescence (LIF) has been compared. The energy distribution of ground-state as well as excited Na atoms from NaCl under electron bombardment was found to be thermal, while under ion bombardment the excited Na atoms were found to be energetic in the range of 2 eV. However for ground-state Na atoms even under heavy ion bombardment (Xe) the energy distribution was found, surprisingly, to be almost purely thermal. In the case of Ca from CaF2 we observed under ion bombardment a non-thermal energy distribution for Ca ground-state atoms at low temperat- ures, but at higher temperatures (above 600 K) a thermal, ion beam induced component became dominant. Similar under electron bombardment only desorption of Ca ground state atoms at elevated temperatures was observed and the energy distribution was purely thermal. In addition no electron induced desorption of Ca was observed for all energies and all temperatures, while under ion bombardment non-thermal emission of Ca was found.