  A possible explanation for the central abundance dips found from
spatially-resolved X-ray spectroscopy of several groups and clusters of
galaxies is resonance scattering. A number of the prominent iron emission lines
are resonance lines. We construct a unique spectral model which takes account
of resonance scattering for several thousand resonance lines, projection
effects, photoelectric absorption, and allows direct spectral fitting. We apply
our model to Chandra observations of two clusters with pronounced central
abundance dips, Centaurus and Abell 2199. The results show that the effect of
resonance scattering on emission from the centre of the cluster can be as much
as 30 per cent for the Fe-K resonance lines, and 10 per cent for several Fe-L
lines, if turbulence is low. The change to the metallicities obtained by
fitting low resolution CCD spectra is at most 10 per cent. Accounting for
resonance scattering does not remove the central dip. Allowing for internal
absorption within the Centaurus significantly improves the quality of the fits,
indicating the presence of absorbing material within the inner 40 kpc of NGC
4696.
