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UBC Theses and Dissertations

Measurement of spectral line profiles in dense plasmas James, Harry Gordon

Abstract

The spectra emitted by a pulsed-arc discharge have been photographed with a medium resolution spectrograph to obtain Stark broadened line images measurable for both width and shift. Plasmas with densities near 10¹⁷cm⁻³ and temperatures of about 2.6 ev were produced by subjecting Argon - Nitrogen mixtures to a square current pulse. Light from the discharge was shuttered by a rotating mirror system so that the plasma was photographed in an interval during the current pulse when the plasma had optimal conditions for measurement. A technique in which the spectral lines from a standard source are photographed on the same plates as the plasma lines has been devised for calibrating the measurement routine and for facilitating shift measurements. Stark parameters were obtained by scanning the plates on a precision comparator. Nineteen ArII lines and six NII lines were studied. For Argon, the agreement with other experimental results is satisfactory but the theory is inadequate. Similarly, the NII theory does not predict the values measured here. On the other hand, some of the qualitative predictions by the Impact theory about the line shape and about the common widths and shifts of lines in the same multiplet have been confirmed. The experiment on the NII lines also reveals advantages of the present technique over other methods for obtaining Stark parameters.

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