Effects of pulse duration upon the plume formation by the laser ablation of Cu in water

Time-resolved images of an ablation plume obtained at different pulse durations have been measured for the liquid-phase laser ablation of a Cu plate, and the emission intensity and size of the plume have been discussed. In some plume images, high-density bright spots were observed. The size of the light-emitting region increases and the bright spots disappear for the irradiation with a 150-ns pulse. We conclude that consecutive excitation by the later part of a longer pulse expands the plume and reduces plume density. These results are consistent with our previous result that less-broadened atomic line spectra with high emission intensity were obtained with a 150-ns-pulse irradiation.