Mg II spectral line broadening in helium, oxygen and argon-helium plasmas

Stark widths and shifts of the astrophysically very important six (279.0777, 279.5528, 279.7998, 280.2705, 292.8633 and 293.6510 nm) singly ionized magnesium (Mg II) spectral lines in helium, oxygen and argon-helium plasmas have been measured at electron temperatures between 30 000 and 52 300 K and electron densities between 1.2 1023 and 1.65 1023 m-3. They are the first experimental results obtained at electron temperatures higher than 20 000 K. A linear, low-pressure, pulsed arc has been used as an optically thin plasma source. The magnesium atoms, as impurities in the driving gases, have been introduced by erosion from the pure magnesium bands fixed on the discharge electrodes. Our measured Stark width and shift values have been compared to the existing experimental and theoretical data. We have found a good agreement with W and d values calculated by the semiclassical perturbation formalism (SCPF).