Electron temperature and density determination in a non-equilibrium laser induced plasma from asymmetric self-reversed emission lines

Summary form only given. In this paper a diagnostic procedure is described for determining the radial distribution of the electron temperature and density and the excitation temperature of an electron-collision dominated plasma using asymmetric self- reversed emission lines. The proposed method was applied to a plasma plume produced by focusing pulsed laser beams (2 GW/cm²) onto a solid aluminum target in a low-pressure environment. The asymmetrically self-reversed resonance line of aluminum 3961.5 Aring, which is emitted from the near the target surface at delay times of ~100 ns after the pulse ending, was used. This line was analyzed and compared with the computed lineshape by solving the equation of radiative transfer taking into account the radial variation of the line width and shift. A Stark-broadened Lorentz line profile is assumed. The theoretical approach is developed on the basis of a recently published work. The continuous radial distribution of the emitting atoms was obtained from Abel inversion of the side-on peak intensity corrected for self-absorption and obtained by direct imaging of the plasma plume. Applying an iterative scheme the electron density and the temperatures as well as their radial distributions are obtained simultaneously for the fist time. Substantial deviation from excitation equilibrium is evident from the large difference determined in the excitation (~8300 K) and electron kinetic (~11800 K) temperatures, while the electron density is ~3.5x 10²³ m^-3.