Experimental studies of helium line broadening in a plasma. II. Low electron densities (lines with forbidden components)

For pt. I see ibid., vol.4, no.10, 1353 (1971). The He I lambda 4471 2 3 P-4 3 D and lambda 4921 2 1 P-4 3 D lines and their associated 2 3 P-4 3 F and 2 1 P-4 1 F forbidden components have been studied in a highly reproducible and homogeneous plasma produced in the after glow of a Z-pinch discharge. Electron densities in the range 3*10 14 <n e <10 15 cm -3 were determined with high accuracy by interferometric and spectroscopic means, and electron temperatures were estimated spectroscopically. Full experimental line profiles for both lines are compared with theory at two electron densities. An important discrepancy between theoretical and experimental values for the forbidden component intensities and shapes, previously reported briefly by the authors for one line and one density, is confirmed for both transitions.