Time-resolved measurement of copper emission spectrum excited by a low-pressure argon laser-induced plasma.

A laser-induced plasma generated with a pulsed Nd:YAG laser under evacuated conditions has complicated structures both temporally and spatially. The time-resolved spectra of copper in three different wavelength regions were observed in detail for elucidating the excitation mechanisms of many atomic/ionic copper emission lines. The emission intensities of copper emission lines, measured in a time-resolved mode, were strongly dependent on the kind of copper lines: ionic or atomic lines, and their excitation energies. Generally, copper ionic lines were rapidly decayed and dominantly emitted from the initial breakdown zone, because the copper ions requiring larger excitation energies were produced mainly in the hot breakdown zone. On the other hand, the atomic lines were emitted during prolonged periods, implying that they could also be excited in the expanded plasma zone. The excitation phenomena occurring in the laser-induced plasma could be better understood by analyzing the time-resolved copper spectra.