  The spontaneous emission is investigated for an effective atomic two-level
system in an intense coherent field with frequency lower than the
vacuum-induced decay width. As this additional low-frequency field is assumed
to be intense, multiphoton processes may be induced, which can be seen as
alternative transition pathways in addition to the simple spontaneous decay.
The interplay of the various interfering transition pathways influences the
decay dynamics of the two-level system and may be used to slow down the
spontaneous decay considerably. We derive from first principles an expression
for the Hamiltonian including up to three-photon processes. This Hamiltonian is
then applied to a quantum mechanical simulation of the decay dynamics of the
two-level system. Finally, we discuss numerical results of this simulation
based on a rubidium atom and show that the spontaneous emission in this system
may be suppressed substantially.
