In the case of dense and hot plasmas, interactions with ionic perturbers become a major
source of broadening. Due to the linear Stark effect, it is the same situation whether the emitter is
an H atom or an hydrogenic ion. The quasistatic approximation used for ionic broadening at low
densities is no longer valid and simultaneous strong interactions between the radiator and the
surrounding perturbers must be taken into account. Much effort has been devoted to this many
body dynamical problem both on the methods and the applications. Important results have been
obtained theoretically or experimentally for lines of H (35-37), He
(36,38,39), N V (40) and
multicharged hydrogenic ions (41). Extensive tables (42) and parametrized formulae (43) are
available.
Analytic expressions have been obtained for the lines of one electron ions (44), and wing formulae
for
plasma broadened spectral lines of hydrogenic ions (45). Ion dynamics effects are also studied in
He lines (46-49).
Far wings of the Lyman 
line of H have been studied in a quasi molecular approach in the
physical conditions of white dwarfs (50).