Electron density determination of aluminium laser-induced plasma

We present temporally and spatially resolved electron density results of laser-induced plasma initiated on the surface of an aluminium target. Aluminium 394.4 and 396.15 nm lines were fit to Lorentzian profiles to evaluate Stark widths and shifts. Experimentally determined electron density versus line width and shift relationships were applied. Fitting to the aluminium lines indicates an electron density of 1.9 ± 0.2 and $3.2\pm 0.4\times {10}^{18}c{m}^{-3}$ for Stark widths and 1.7 ± 0.5 and $1.7\pm 0.5\times {10}^{18}c{m}^{-3}$ for Stark shifts at a 0.3 μs time delay following plasma initiation for the aluminium Al i 394.4 and 396.15 nm transitions, respectively. Simultaneous observations of the singly ionized nitrogen line, N ii, at 395.5 nm were also fit for a time delay of 0.2 μs, indicating an electron density of $1.8\pm 1.0\times {10}^{18}c{m}^{-3}$. The differences between the nitrogen and aluminium electron densities show evidence of self absorption. (paper)