  An averaging procedure is proposed to account for spectral features of
correlated one-dimensional systems in the presence of non-magnetic impurities.
The dynamical spin structure factor for a corresponding random ensemble of
Heisenberg chain segments is calculated by exact numerical diagonalization. It
is shown that a few-pole approximation is sufficient to describe the numerical
results. A similar analysis is proposed for the discussion of experimental
spectra, such as obtained by inelastic neutron scattering measurements on
Zn-doped CuO chains. By examination of the disorder-induced pseudo-gap, the
loss of spectral weight, and the discrete peak structures due to
smallest-cluster contributions, the underlying impurity distribution function
can be determined.
