Shift and width of theHαline of hydrogen in dense plasmas

The profile and the shift of the ${\mathrm{H}}_{\mathrm{\ensuremath{\alpha}}}$ line of hydrogen were measured and the shift was calculated at high electron densities in a helium plasma. The plasma was produced in a gas-liner pinch, which was diagnosed by Thomson scattering. Densities were between 1\ifmmode\times\else\texttimes\fi{}${10}^{18}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$ and 1\ifmmode\times\else\texttimes\fi{}${10}^{19}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$ and temperatures varied from 4 up to 12.5 eV. The results show a nonlinear behavior of the shift. Corresponding theoretical calculations have been performed, especially taking into account the dynamic screening of the electron-atom interaction. The agreement is very good for densities below 5\ifmmode\times\else\texttimes\fi{}${10}^{18}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$; above that density it is satisfactory.