  The spontaneous emission rate of a radiating atom reaches its
time-independent equilibrium value after an initial transient regime. In this
paper we consider the associated relaxation effects of the spontaneous decay
rate of atoms in dispersive and absorbing dielectric media for atomic
transition frequencies near material resonances. A quantum mechanical
description of such media is furnished by a damped-polariton model, in which
absorption is taken into account through coupling to a bath. We show how all
field and matter operators in this theory can be expressed in terms of the bath
operators at an initial time. The consistency of these solutions for the field
and matter operators are found to depend on the validity of certain velocity
sum rules. The transient effects in the spontaneous decay rate are studied with
the help of several specific models for the dielectric constant, which are
shown to follow from the general theory by adopting particular forms of the
bath coupling constant.
