Spectral profile of atomic emission lines and effects of pulse duration on laser ablation in liquid

The emission spectra of laser-ablated Cu atoms in water were examined, focusing on the irradiation-pulse duration effects. Spectral line profile was observed for the pulse duration of 19, 90, and 150 ns at various delay times. The line width as narrow as instrumental width was obtained by 150-ns pulse at the delay time of 800 ns. Also, long pulses result in high intensity of the emission. The spectral feature obtained by long pulses looks similar to that obtained in a gas phase. The absorption of the later part of the long pulse directly by the plume having been formed by the earlier part of the pulse may be the cause of this gas-phase-like emission. Whether the pulse heats directly the surface or the plume was investigated by the measurements of the removal volume of the ablation pit obtained by laser confocal scanning microscopy and the maximum bubble expansion size observed by shadowgraphy.