## 3. Density effectsThe aim of this section is to examine the density dependence of the lineshape. According to equation (4), this dependence is contained in the maximum angular momentum , since , with Debye distance. Let us decompose the profile of equation (4) into two terms denoted and so that: where is the asymptotic Holtsmark profile, i.e: which is the object of the next paragraph,
is independent of the density. Hence, the density dependence comes
from via the limit . We
have calculated the latter contribution at various densities and
temperatures.The results are reported in the Tables 1 to 3. It comes
out from these tables that the influence of the density increases with
the temperature, and that the density effect is meaningful only in the
linecore and the near linewings ( Å). For
greater than 8Å, the profile is linear in
density, within an error less than , at
densities below cm
At higher densities, gets smaller and the region of non-linearity enlarges. However, not too far in the line wings (detunings Å), is a good cut-off. © European Southern Observatory (ESO) 1998 Online publication: December 8, 1997 |