Spatially and Temporally Resolved Absorption Studies of YO in the Plume of Laser-Ablated Y 2 O 3

Abstract

A spatially and temporally resolved transient absorption technique has been employed to investigate the dynamics of ground-state YO during 355 nm laser ablation of Y₂O₃. Time-of-flight (TOF) measurements of the expanding YO plume in vacuum and in Ar or O₂ ambient are reported. During the initial expansion of YO in vacuum, the center-of-mass velocity and the expansion velocity increase with distance up to the boundary of the Knudsen layer. In the presence of oxygen, reactions of the ablated atomic species with oxygen take place, resulting in the formation of YO with broad velocity distribution. From the peak time of the observed TOF distributions, the most probable velocities 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 O₂, respectively. The dependence of the peak time on distance shows that the experimental data can be well fitted with a shock wave model at higher ambient gas pressure.