Spatially and temporally resolved absorption studies of YO in the plume oflaser-ablated Y2O3

A spatially and temporally resolved transient absorption technique has been employed to investigate the dynamics of ground-state YO during 355 nm lase r ablation of Y2O3. Time-of-Eight (TOF) measurements of the expanding YO pl ume in vacuum and in Ar or O-2 ambient are reported. During the initial exp ansion of YO in vacuum, the center-of-mass velocity and the expansion veloc ity increase with distance up to the boundary of the Knudsen layer. In the presence of oxygen, reactions of the ablated atomic species with oxygen tak e place, resulting in the formation of YO with broad velocity distribution. From the peak time of the observed TOF distributions, the most probable ve locities of YO are found to be 2.6 km/s in vacuum, 2.2 km/s in 50 mTorr Ar, and 1.8 km/s in 50 mTorr O-2, respectively. The dependence of the peak tim e on distance shows that the experimental data can be well fitted with a sh ock wave model at higher ambient gas pressure.