  The evolution of entanglement for two identical two-level atoms coupled to a
resonant thermal field is studied for two different families of input states.
Entanglement enhancement is predicted for a well defined region of the
parameter space of one of these families. The most intriguing result is the
possibility of probabilistic production of maximally entangled atomic states
even if the input atomic state is factorized and the corresponding output state
is separable.
