  We analyze the dynamics of a single-level quantum dot with Coulomb
interaction, weakly tunnel coupled to an electronic reservoir, after it has
been brought out of equilibrium, e.g. by a step-pulse potential. We investigate
the exponential decay towards the equilibrium state, which is governed by three
time scales. In addition to the charge and spin relaxation time there is a
third time scale which is independent of the level position and the Coulomb
interaction. This time scale emerges in the time evolution of physical
quantities sensitive to two-particle processes.
