Laser ablation of aluminum and silver targets submerged in water has been studied. The self-reversed structure in the atomic emission lines has been observed. The results were compared with the line profile calculation based on one dimensional radiative transfer model. In the calculation the population density was assumed either Gaussian or a rectangular distribution, the latter represents the higher distribution of the ground state in the periphery of the plume. The comparison of the experiment and the calculation suggests a high distribution in the periphery region for the plume in water in comparison with the plume in air.
Laser ablation of Eu2O3 in water has been studied by emission spectroscopy and shadowgraphy. In the emission spectra, many emission lines appear in the visible region and last for a millisecond. In the early time range from the ablation pulse shot, most of them are assigned to Eu atoms and Eu+ ions. Among them, the emission lines originated from the transition to the ground state of both species show the self-reversed profile. It indicates that both Eu atoms and Eu+ ions in their ground state are abundant in the peripheral region of the plume. In a later time range, the emission lines originated from trivalent Eu species (Eu2O3 nanoparticles) appear and last for a long time. In the shadowgraphs, the gas cavity-like plume expands, shrinks, and collapses with time. Based on the obtained results, we revealed that the chemical reactions following the laser ablation phenomenon in liquid does not end only in the plume, but also proceeds in the surrounding liquid phase. By using the long-lasting lanthanide emission as a probe, the information about the distribution of the ablated species in the plume can be obtained as long as milliseconds. The mechanism of the particle formation can also be discussed.