Measurement and interpretation of dielectronic recombination satellite line intensities

Abstract

Using a theta-pinch plasma at temperatures between 2 and 3*10⁶ K and densities of 1 to 8*10¹⁶ cm^-3, measurements have been made on the satellite lines which appear on the long-wavelength side of the helium-like resonance lines of oxygen VII and nitrogen VI. These satellites are due to emission from doubly excited or inner-shell excited lithium-like ions. The relative intensity of the satellites to the resonance lines were measured as a function of time. The intensities are shown to fit well to a quantitative theory which has been developed to account for the emission. This indicates that the dominant populating mechanism is by dielectronic recombination, which would be the only mechanism in a steady state plasma. However, the transient nature of the theta-pinch leads to an additional mechanism which contributes in the early phase of the plasma, i.e. the inner-shell excitation of lithium-like ions.