Investigation on the emission characteristics of copper atomic and ionic lines in reduced-pressure argon spark discharge plasma based on time-resolved measurement

Time-resolved signals of several atomic and ionic copper lines from argon spark discharge plasmas were measured when the pressure of argon was varied at evacuated atmospheres. The time profiles of these emission lines were quite different. The profile width of the atomic resonance line, Cu I 324.75 nm, was broader than that of an ionic line, Cu II 213.60 nm. In the case of Cu I 324.75 nm, the overall lifetime of the signal was almost constant independent of the argon pressures, and the profile comprised an initial peak and a subsequent large tail which was more predominant at larger pressures of argon. In the case of Cu II 213.60 nm, the overall lifetime of the signal was a little varied at different argon pressures, and the profile comprised an initial peak and a subsequent small tail. These effects could be explained from the difference in the excitation process between the atomic and the ionic lines, which was changed temporally within a single spark shot.