Measurements of the Stark broadening of ionized silicon lines from a plasma

The Stark-broadened profiles of singly ionized silicon lines of multiplet 1(3s3p²²D-3s²4p²Pᵒ) and multiplet m(3s²4s²S-3s²4p²Pᵒ) have been measured by three methods, namely, photoelectrical scanning, fast scanning with a Fabry-Perot spectrometer, and using an optical multichannel analyzer. An electromagnetically driven shock tube was used to generate a high-density helium plasma containing small silicon and hydrogen admixtures and having an electron density Nₑ≈1×10¹⁷ cm^-3 and temperature kT≈1.5 eV. The measured half widths of the lines in the two multiplets are in {~}10% agreement with the widths estimated from a semiclassical calculation, while semiempirical and quantum-mechanical calculations give widths by as much as a factor of 2 below the measured widths.