Study of the plume generated by Nd : YAG laser ablation of a hydroxyapatite target

The plume generated by Nd:YAG laser ablation of a hydroxyapatite target has been investigated in vacuum and at 0.1 and 0.2 mbar of water vapor. The in vestigation has been carried out by means of fast intensified CCD imaging w ith the aid of bandpass interferential filters that allow the following sin gle species to be isolated: neutral calcium, calcium oxide radicals and neu tral oxygen. Results obtained in vacuum reveal that expansion takes place a t a constant velocity of about 2 x 10(4) m/s for the atomic species and abo ut 3 x 10(3) m/s for the molecular ones and that emission is completely dom inated by emissive neutral calcium. When ablation is carried out in a water atmosphere, the background gas confines the species in the leading edge of the plume, which results in the formation of a planar shock wave at 0.1 mb ar and a spherical shock wave at 0.2 mbar. Comparison of the images with th ose obtained at 0.1 mbar of Ne has revealed the existence of chemical react ions between the plume and the water atmosphere, leading to the formation o f calcium oxide radicals. In that case, plume emission is dominated by thes e molecular species.