Measurement of Stark widths of Ni II spectral lines by laser induced breakdown spectroscopy

The Stark widths of 53 Ni II spectral lines have been measured by laser induced breakdown spectroscopy. The laser induced plasmas have been generated from Ni-Cu and Ni-Al alloys with a wide range of nickel concentrations. The electron density at the different instants of the plasma lifetime has been determined from the Stark broadening of the Hα line and is in the range (1.6-6.8)×1017 cm−3. The plasma temperature, measured by the Boltzmann plot method, is in the range 13100-18000 K. Within the ranges of electron density and temperature in the experiment and the statistical errors, the Stark widths are found to be proportional to the electron density. A procedure, based on the curve-of-growth methodology and the use of samples with different nickel concentrations, has been applied to reduce self-absorption. The Stark widths obtained are compared to experimental and theoretical data available in the literature.

► We have measured the Stark widths of 53 Ni II spectral lines, 44 for the first time. ► Stark widths are determined by laser induced breakdown spectroscopy. ► Self-absorption is reduced using samples with different nickel concentrations. ► The procedure has allowed to include lines belonging to 27 multiplets.