Observation of an ion effect in the profile of the 4471-Å line of Hei

We have measured the profile of the 4471-Å line of Hei at electron densities $n_e=3\mathrm{}\times {10}^{15}, {10}^{16}, \mathrm{and} 3\times {10}^{16}$ ${\mathrm{cm}}^{-3\mathrm{}}$ in plasmas of different chemical composition. We have observed a smearing of the central dip of the line varying with the inverse square root of the reduced mass of the radiator-perturber system. A comparison with a calculation using ion dynamics at $n_e=3\mathrm{}\times {10}^{15}$ ${\mathrm{cm}}^{-3\mathrm{}}$ shows a better agreement for the dip intensity than with the usual quasistatic ion calculations.