INVESTIGATION OF THE HE-II-P-ALPHA AND HE-II-P-BETA TRANSITIONS AT HIGH-DENSITIES

Measurements of Stark profiles of the He II P-alpha line at lambda = 4 68.6 nm and of the He II P-beta line at lambda = 320.3 nm from a well diagnosed plasma of a gas-liner pinch discharge are reported. The plas ma parameters were determined independently by Thomson scattering, and we found n(e) = 0.5-4 x 10(18) cm(-3), k(B)T(e) = 4-7.5 eV when measu rements of the He II P-alpha line were carried out and n(e) = 0.4-0.9 x 10(18) cm(-3), k(B)T(e) = 3-5.4 eV for the He II P-beta measurements . We compare widths and shifts of the spectral lines with theoretical approximations and present new empirical scalings. While the width of the He II P-alpha line shows significant discrepancies with lineshape theories, in the case of the He II P-beta line profile we find good ag reement with some calculations. In particular, to investigate ion dyna mic effects we present an accurate measurement of the dip in the centr e of the spectral line.