Line-broadening analysis of plasma emission produced by laser ablation of metal Cu

A time-resolved diagnostic technique was used to investigate the emission spectra from the plasmas produced by 1.06 mum, 10 ns pulsed-laser ablation of metal Cu. The spectral line broadening was analysed according to the obtained spectra of the excited atoms, several broadening factors were estimated according to our experimental conditions and the results indicate that Stark broadening is the main broadening mechanism. Under the assumption of local thermodynamic equilibrium, electron number density was deduced from the Stark-broadening measurements. The time evolution and space profile of electron density were obtained. The combined results indicate that impact excitation and ionization occurring after the end of the laser pulse is more important than photon-induced processes produced by the laser pulse.