  We make an analysis of the distribution of the extensive Doppler redshift
defined as $\widetilde{z}_{Dopp}=(z_{abs}-z_{em})/(1+z_{em})$ with a sample of
1317 absorption redshifts available from 401 quasars. The analysis reveals a
bi-peak structure in the distribution, with one component located at
$\widetilde{z}_{Dopp}\simeq 0.00$ and the other at $\widetilde{z}%
_{Dopp}\simeq -0.01$. A study of some possible causes suggests that the
structure can be well interpreted: while the absorbers inside the same cluster
as the quasar concerned could contribute to the first component and the less
populated space between clusters could explain the gap between the two peaks,
the typical distance between clusters could account for the second component.
If the bi-peak structure is true, which needs to be confirmed by complete
samples, one would be able to obtain some useful cosmological information.
