Spatial spectroscopic diagnose of the plasma produced from laser ablation of a KTA crystal

Optical emission spectra of the plasma produced by the 1.06 mu m Nd:YAG laser ablation of KTiOAsO4 (KTA) crystal in vacuum and in air is studied spectroscopically in time-integrated manner. Electron density and temperature in the plasma in vacuum are determined by using Stark-broadened line width of K toms (KI 766.5 nm) and Boltzmann plot method with the relative intensities of 5 emission lines of singly ionized Ti ions, respectively, The dependences of electron density electron temperature on distance from the target surface and laser irradiance are investigated. By comparing the optical emission spectra in vacuum with those in air the effects of background gas are discussed. We also tested the validity of the assumptions for measuring electron temperature.