Detection of metastable chlorine ions in time-modulated plasma by time resolved laser-induced fluorescence

Metastable chlorine ions (Cl⁺*) were detected in time-modulated inductively coupled plasma by a time-resolved laser-induced fluorescence technique. By varying the rf power, gas pressure and modulation frequency, the Cl⁺* density was measured in detail. In the discharge-on period, the Cl⁺* density increased as the rf power increased. In the discharge-off period, the rf power decreased within 1 μs, however, the Cl⁺* density decreased more slowly and persisted for a while. The decay constant was evaluated to be around 10 μs by fitting the decay curve under our experimental conditions. In addition, the diffusion coefficient of Cl⁺* was also estimated.