ИСТИНА

We study the peculiarities of electromagnetic radiation spectrum emitted during the rescattering process of the electronic wavepacket by the parent potential center. It is demonstrated that the semiclassical approach generally applied to study processes in extreme nonlinear optics leads to the conclusion that probability of transition is proportional to the population of the initial state and, hence, is in contradiction with the quantum electrodynamics. The only situation when the semiclassical approach provides consistent with the quantum-electrodynamical calculations result is the recombination to the bound state that populated with probability close to unity. We provide the results of Schrödinger equation in the case of atomic system interacting with quantum electromagnetic field and compare them with the semiclassical results. One should mention that probabilities of the continuum-continuum transitions in the semiclassical approach are appeared to be proportional to the population of the initial continuum state. It means that if we have wave packet in the continuum with a definite spectral width near the energy E, the transitions to neighboring states within the energy interval will be only possible. Such a conclusion is also in contradiction with quantum-electrodynamical calculations of the bremsstrahlung spectrum. References. 1) A. V. Bogatskaya, E. A. Volkova, V. Y. Kharin, A. M. Popov Polarization response in extreme nonlinear optics: when can the semiclassical approach be used? //Laser Physics Lett. 13, 045301 (2016).