Experimental measurements of Stark widths for Mn I lines in long laser spark

We report the experimental Stark widths of Mn I lines belonging to multiplets z⁶P° → a⁶S and z⁶D° → a⁶D in long spark induced by laser. We have used aluminum alloy containing 80 ppm of manganese as a target to avoid strong self-absorption of Mn I lines. Its absence was proved by the comparison of observed intensities with relative strengths of lines within multiplets. Electron density of plasma estimated by Mg I (5172.68 Å) and Al II (2816.18 Å) lines was within the range of (4–30) × 10¹⁶ cm⁻³. The shortest possible gate allowed the observation of symmetric atomic and ionic lines. The spatial profiles of plasma temperature and electron density along the axis of long spark demonstrated that both values were lower than for spherical plasma. Measured Stark widths of resonance multiplet z⁶P° → a⁶S decrease from 0.075 Å for its first component to 0.055 Å for the last one, while Stark widths of components of multiplet z⁶D° → a⁶D increase from 0.095 Å to 0.125 Å. No Stark shifting was observed for the studied multiplets. - Highlights: • Diagnostics of long laser-induced plasma • Stark widths of resonance and non-resonance Mn I lines • No Stark shifts are observed.