  In order to investigate the near wing of the Lyman-alpha line, accurate line
profile calculations and molecular data are both required due to the existence
of a close line satellite responsible for its asymmetrical shape. Lyman-alpha
lines observed with the Cosmic Origin Spectograph (COS) on the Hubble Space
Telescope ( HST) show this peculiarity in the spectra of DBA and DA white dwarf
stars. A similar asymmetrical shape in the blue wing can be predicted in the
Balmer-alpha line of H perturbed by He and H atoms. In continuation with a very
recent work on the Lyman-alpha line, where the n=2 potential energies and
transition dipole moments from the ground state were determined, we present new
accurate H-He potential energies and electronic transition dipole moments
involving the molecular states correlated with H(n=3)+He and their transition
dipole moments with the states correlated with H(n=2)+He. Those new data and
existing molecular data for H(n=2,3)-H are used to provide a theoretical
investigation of the collisional effects in the blue wing of the Balmer-alpha
line of H perturbed by He and H atoms. We note the consequences for the
Balmer-alpha line shape in the physical conditions found in the cool atmosphere
of DZA white dwarfs where helium densities may be as high as 10^21 cm-3. This
study is undertaken with a unified theory of spectral line broadening valid at
very high helium densities.
