Interaction effects of an excimer laser beam with hydroxyapatite targets

The excimer laser ablation of hydroxyapatite targets has been studied under diverse conditions. For this purpose, KrF (248 nm) excimer laser pulses at two different fluences, 4.8 and 2.1 J/cm2, onto two different density targets, 1.3 and 1.7 g/cm3, have been used resulting in the release of material from them and in the formation of the characteristic plasma plume. Fast intensified CCD-imaging with the aid of bandpass filters has been used to analyze the plume. The results as obtained show the presence of three emitting species in the plasma: an atomic component, a molecular one, and hot particulates expanding away the target. The dependence of their velocities with the laser fluence shows that the mechanism of production of the molecular component is different of that of the other species. The analysis of the dependence on the density of the target reveals that the mechanism controlling the ablation rate in this range of fluences is the expulsion of hot particulates from the target.