Asymmetric Stark broadening of the Fe I 538.34 nm emission line in a laser induced plasma

In this work asymmetries along with shifts in the line profiles of neutral iron emission lines coming from a laser induced plasma have been detected. The plasma was produced in air at atmospheric pressure on a 50% Fe-Ni alloy and the emission was collected at a temporal window of (2.5, 3) μs. To avoid the effect of spatial inhomogeneity on the profiles, a deconvolution procedure was applied to obtain the spatially resolved emissivity. Asymmetric theoretical Stark profiles, which take into account the effect of static ions, were used to be fitted to the experimental data of the emission profile of the line Fe I 538.34 nm. The fitting of the theoretical profile to the experimental data was carried out by means of the least squares method using genetic algorithms to automatically solve the optimization problem. The correlation coefficient was higher for the asymmetric fits than for the symmetric ones. From the fit, the quasistatic ion broadening parameter α, the electron broadening parameter we, and the total shift of the maximum of the line dt, were obtained. The ion parameter α varied in a range (0.2-0.3) for an electron density between (4-15) × 1016 cm− 3. The ion influence on the total broadening was of 15-20%. The total shift varied in the range (0.01-0.06) nm and it was mainly given by the ion shift, the electron shift being negligible. For the electron density range in this work, approximated linear behaviors of the total width and shift with electron density have been obtained.