Emission characteristics of copper ionic lines from the 3d ⁹5s-3d⁹4p transition in a low-pressure laser-induced plasma

The emission characteristic of copper ionic lines requiring large excitation energies was investigated in low-pressure laser-induced plasma spectroscopy (LP-LIPS), when argon was employed as plasma gas. The excited mechanism of the ironic lines whose electron transitions were assigned to the 3d95s-3d94p configuration was understood from the time-resolved spectra of copper. The emission intensity of the copper emission lines, measured in a time-resolved mode, was extremely dependent on the kind of copper lines and the upper energy. Generally, their emission intensities dramatically decreased with the duration time, along with the recombination as well as the de-excitation of copper ions requiring larger kinetics energy which mainly were produced in a hot breakdown plasma. The emission behavior excited from the 3d⁹5s- 3d⁹4p transition, such as the Cu II 254.4 nm and the Cu II 276.9 nm lines, was generally similar to that from 3d⁹4p-3d⁹4s transition, although their excitation energies were different. This effect would result from a common and dominant ionization /excitation mechanism, which was collision energy transfer from energetic particles such as fast electrons.