  Spontaneous emission of the quantum system driven by a high intensity
classical laser field is analyzed. The study is based on the accurate
consideration of quantum system interaction with vacuum quantized field modes
in the first order of perturbation theory, while the intense laser field is
considered classically beyond the perturbation theory. It is demonstrated that
the spectrum of the spontaneous emission can be used for analyzing of the
strong-field dynamics and structure of the energy spectrum of the atomic
system. The obtained data are compared with that obtained in the frames of
semiclassical approximation typically used for analyzing of the strong-field
dynamics. It is found that the applicability of the semiclassical approach is
strictly limited.
