  We have shown that the steady state probability distribution function of a
diffusion-coalescence system on a one-dimensional lattice of length L with
reflecting boundaries can be written in terms of a superposition of double
shock structures which perform biased random walks on the lattice while
repelling each other. The shocks can enter into the system and leave it from
the boundaries. Depending on the microscopic reaction rates, the system is
known to have two different phases. We have found that the mean distance
between the shock positions is of order L in one phase while it is of order 1
in the other phase.
