The influence of the Stark effect on the shape of He-like argon lines in a dense plasma

We interpret the relative intensities and widths of ArXVII lines in a dense plasma including the Stark effect of electromagnetic fields. For many elements the wavelength of the forbidden line 21S0-11S0 is almost equal to that of intercombination y-line (23P1-11S0). A strong enough electric field can cause the forbidden line intensity to become high enough to have a visible effect on the intensity of the intercombination line. This paper calculates the intensity of the resonance, intercombination, and forbidden lines versus the strength of the electric field, including the shift of the n = 2 levels in ArXVII. A collisonal-radiative model simulates the ArXVII lines in a dense plasma with a electric field, demonstrating that an electric field with E = 1010 V/cm has the same effect on line shape as plasma opacity. Good agreement is obtained with ArXVII spectra emitted by a Z-pinch, with peak current 500 kA. Since the intensities of intercombination and resonance lines are widely used to determine plasma parameters, the present study is relevant to the applicability range of existing methods, and may show the way to measure strong electric fields. We also discuss the reasons for the presence of strong macroscopic electric fields in a plasma