  We study in this paper a non-equilibrium Fermi-edge problem where the system
under investigation is a single electron reservoir putting under an AC electric
field. We show that the electron Green's function and other correlation
functions in the problem can be solved and expressed exactly in terms of a
well-defined integral. The qualitative behaviors of the solution is studied and
compared with the situation where the impurity is coupled to more than one
reservoirs at different chemical potentials.
