  The effective mass that approximately describes the effect of a classical
homogeneous gravitational field on an interacting atom-radiation field system
is determined within the framework of the Jaynes-Cummings model.
  By taking into account both the atomic motion and gravitational field, a full
quantum treatment of the internal and external dynamics of the atom is
presented. By solving exactly the Schrodinger equation in the interaction
picture, the evolving state of the system is found. Influence of a classical
homogeneous gravitational field on the energy eigenvalues, the effective mass
of atom-radiation field system and the Wigner distribution of the radiation
field are studied, when initially the radiation field is prepared in a coherent
state and the two-level atom is in a coherent superposition of the excited and
ground states.
