Neutral and Ion Number Density Mapping of Laser Ablated Titanium Plasma Plumes Using Spectroscopic and Electrostatic Probe Techniques

Development of spectroscopic and electrostatic probe techniques for the quantitative characterisation of low temperature laser ablated plasma plumes are described. The titanium plasma plume is formed by KrF irradiation, incident on a rotating target at laser fluences of 2-6 Jem−2 with a spot size 1.4 mm x 1.4 mm. A collimated, short pulsed, tunable dye laser at a set delay time, between 500ns - 2µs, is used to spatially and temporally probe the plasma plume in a direction parallel to the target surface (i.e. in x-z plane). For a plasma under-going self-similar expansion, the observed absorbance values A(ΔλS, z) are related to the corresponding absorber number densities N(x, z) within the (x-z) plane by (1) where f is the absorption oscillator strength, t is the probe delay time and ΔλS is the dye laser detuning from line centre wavelength λ0 of the transition.