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The Stark parameters, the width (W) and the shift (d), of the neutral argon (Ar I) 425.9 nm spectral line have been studied in a linear, low-pressure, optically thin pulsed arc discharge. The line shapes are measured in three different plasmas at about 16,000 K electron temperature (T) and about 7.0×1022 m−3 electron density (N). The separate electron and ion contributions to the total Stark width (Wt), i.e. We and Wi, as well as to the total Stark shift (dt), i.e. de and di, have also been obtained and represent new experimental data in this field.

On the basis of the observed asymmetry of the Stark broadened line profile we have deduced the ion broadening parameters, which describe the influence of the ion static (A) and the ion-dynamical effect on the width (D) and on the shift (E) of the line shape. Stronger influence of the ion contribution on the 425.9 nm Ar I line shape than is the one predicted by current theory has been evidenced.

On the basis of the accurately recorded 425.9 nm Ar I line shape (in the 4s′–5p′ transition), the basic plasma parameters, i.e. electron temperature (T) and electron density (N) have been recovered. This has been achieved by applying the recently developed line deconvolution procedure. The plasma parameters (T and N) have also been measured using independent diagnostics techniques.