Correlation between Metastable and Ground-State Fluorine Atom Densities Measured by Laser-Induced Fluorescence and Vacuum Ultraviolet Absorption Spectroscopies

Abstract

The correlation between F atom densities at the ground state and the metastable state was determined in high-density fluorocarbon plasmas by laser-induced fluorescence (LIF) and vacuum ultraviolet absorption spectroscopies. A proportional relationship has been determined between the metastable and ground-state F atom densities, which can be understood reasonably well by considering the production and loss processes of the metastable state. The metastable state is produced from the ground state by electron impact excitation. According to the results of lifetime measurements, the loss of the metastable state is dominated by electron collision in high-density plasmas (≥2×1012 cm-3). Since both the production and the loss of the metastable state are dominated by electron impact processes, the density of the metastable state is proportional to the ground-state F atom density. The present experimental results suggest the possibility of monitoring the spatial distribution of the ground-state F atom density using LIF detection of the metastable state.