Collisional broadening of the Balmer-αtransition of H andHe+in plasmas

We have computed the Stark-broadened width of the ${\mathrm{H}}_{\mathrm{\alpha }}$ transition of neutral hydrogen ($n_e$ ${=10\mathrm{}}^{15}$–${10}^{17}$ ${\mathrm{cm}}^{\mathrm{-}3}$) and singly ionized helium ($n_e$ ${=10\mathrm{}}^{17}$–${10}^{18}$ ${\mathrm{cm}}^{\mathrm{-}3}$) at several plasma temperatures. Our calculations include dynamical contributions of perturbing ions, which dominated the widths of this important transition, particularly at lower electron densities. We compare our results for neutral hydrogen with experimental results over a span of two decades in electron density ($n_e$), and excellent agreement is obtained.