We analyze how a decaying cavity field can lead to significant atomic
cooling. This cooling can be intuitively understood by invoking the ad
iabatic theorem to characterize the dynamics of an atom dressed by a c
lassical field. We find numerically that cooling can proceed well into
the quantum regime where there are only a few photons left in the cav
ity, and where the adiabatic theorem ceases to be applicable. A physic
al interpretation of this final cooling stage is given.