Stark-Profile Measurements for the First Fourn−αLines of Ionized Helium

Using an electromagnetically driven $T$ tube as a source, the profiles of the He II 304-Å ($n=2\mathrm{} \mathrm{to} 1$), He II 1640-Å ($n=3\mathrm{} \mathrm{to} 2$), He II 4686-Å ($n=4\mathrm{} \mathrm{to} 3$), and He II 10 123-Å ($n=5\mathrm{} \mathrm{to} 4$) lines were scanned and compared with Stark broadening theory. The plasma conditions correspond to electron temperature from 4 to 5 eV and electron densities from 1 × ${10}^{17}$ to 3 × ${10}^{17}$ ${\mathrm{cm}}^{-3\mathrm{}}$. Agreement of measured relative intensities with theory is typically within ∼ 30%, provided a distinction is made between absorption and emission line shapes of the resonance line in a singly ionized helium plasma.