  One-dimensional reaction-diffusion systems are mapped through a similarity
transformation onto integrable (and a priori non-stochastic) quantum chains.
Time-dependent properties of these chemical models can then be found exactly.
The reaction-diffusion processes related to free fermion systems with
site-independent interactions are classified. The time-dependence of the mean
particle density is calculated. Furthermore new integrable stochastic processes
related to the Heisenberg XXZ chain are identified and the relaxation times for
the particle density and density correlation for these systems are found.
