  We study a mixture of two light spin-1/2 fermionic atoms and two heavy atoms
%in a Mott state in a double well potential. Inelastic scattering processes
between both atomic species excite the heavy atoms and renormalize the
tunneling rate and the interaction of the light atoms (polaron effect). The
effective interaction of the light atoms changes its sign and becomes
attractive for strong inelastic scattering. This is accompanied by a crossing
of the energy levels from singly occupied sites at weak inelastic scattering to
a doubly occupied and an empty site for stronger inelastic scattering. We are
able to identify the polaron effect and the level crossing in the quantum
dynamics.
