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Measurement of the profile of He I 4471 Å at low electron densities Stevenson, Dale Christian

Abstract

The profiles of the He I lines with forbidden components in plasmas with electron densities below 10¹⁵ electrons per cc. are of astro-physical interest. A pulsed-arc plasma device has been constructed and operated at such initial conditions that in the afterglow (i.e. up to 200 μsec after breakdown), the steadily decreasing electron density passes through the range of interest. The plasma was observed end-on with a monochromator at a wavelength near 4471 angstroms for each discharge, and the intensity recorded as a functions of time. Good shot-to-shot reproducibility of the plasma permitted the line profile to be reconstructed for different times by repeating the measurements at different wavelengths spanning the line. The profile of He I 4471 has been measured for 10¹⁵ cm ̄³ and agreement has been found with the results of Burgess and Cairns (1971) and recent calculations of Barnard and Cooper (to be published).

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