  We theoretically analyze the light scattering of an optomechanical cavity
which strongly interacts with a single two-level system and couples
simultaneously to a mechanical oscillator by radiation forces. The analysis is
based on the assumptions that the system is driven at low intensity, and that
the mechanical interaction is sufficiently weak, permitting a perturbative
treatment. We find quantum interference in the scattering paths, which allows
to suppress the Stokes-component of the scattered light. This effect can be
exploited to reduce the motional energy of the mechanical oscillator.
