Stark Shifts of Ionized Helium Lines

The shifts of the ionized helium lines λ4686A ( n =4→3) and λ3203A ( n =5→3) were measured relative to the centers of gravity of the fine structures of these lines. A capillary tube, through which condensed discharge was passed, was used as a plasma light source. Side-on observation enabled one to obtain optically thin plasma. In each case the center of gravity of the fine structure lines excited by a liquid-nitrogen-cooled hollow cathode discharge was assumed to be the unperturbed position. The measured red shifts of the He II lines λ4686A and λ3203A are -0.041±0.023 cm -1 and -1.3×0.3 cm -1 respectively, under the plasma condition of N e =(1.6×0.4)×10 16 cm -3 , T e =(2.2±0.3)×10 4 K, and N e =(1.2±0.3)×10 16 cm -3 , T e =(1.3±0.3)×10 4 K respectively. The present results are consistent with those of Murakawa but not with those of Pittman et al.