  We investigate the Wigner-Weisskopf decay of a two level atom in front of an
oscillating mirror. This work builds on and extends previous theoretical and
experimental studies of the effects of a static mirror on spontaneous decay and
resonance fluorescence. The spontaneously emitted field is inherently
non-stationary due to the time-dependent boundary conditions and in order to
study its spectral distribution we employ the operational definition of the
spectrum of non-stationary light due to the seminal work by Eberly and
Wodkiewicz. We find a rich dependence of this spectrum as well as of the
effective decay rates and level shifts on the mirror-atom distance and on the
amplitude and frequency of oscillations of the mirror. The results presented
here provide the basis for future studies of more complex setups, where the
motion of the atom and/or the mirror are included as quantum degrees of
freedom.
