Experimental Study of the Stark Broadened Helium Ion Lines Hell 121.5, 164.0 and 468.6 nm

Abstract

Using a pulsed linear discharge of high purity, Stark broadened profiles of the first two Balmer lines and the Paschen-α line of HeII have been investigated. The electron density (Ne = 5.5 · 1022 m-3) was measured with a coupled cavity He-Ne laser interferometer. The intensity ratio of the HeII 468.6 nm and the HeI 471.3 nm line was employed to determine the electron temperature (Te = 3.8 eV). At these plasma parameters the measured ion lines are unaffected by self absorption. This enables direct comparison with existing theories. Discrepancies between experimental and theoretical line shapes are critically discussed. Fine structure effects, usually neglected in theories, turn out to be important for the Balmer-α line.