ИСТИНА

General approach to analyze the spontaneous emission of an atomic system driven by a strong laser field is discussed in detail. It based on the first order of perturbation theory for the interaction with quantized vacuum field modes while the interaction with the intense classical laser field is considered numerically or analytically beyond the perturbation theory [1]. The spontaneous emission from the model one-dimensional atom driven by the high-intensity Ti-Sa laser field is studied. Different types of transitions between discrete and continuum states are found to exist and distinguished. The comparison of emission spectrum data for a single atom obtained in the frames of semiclassical approach with results of quantum-electrodynamical (QED) calculations reveals the absolute discrepancy of these data. The QED spectrum is richer showing besides fundamental frequency and its third harmonic peaks a lot of other peaks that corresponds to spontaneous emission from different populated states to low-lying unpopulated states. Some of them are formed during the laser pulse action, while others appear in the after-pulse limit. It was also demonstrated the spontaneous emission from the atom in the after-laser-regime can be used to testify the population trapping in atomic Rydberg states and interference stabilization phenomenon. The performed analysis can be effectively used for the investigation of energy level dynamics in strong laser field, i.e. the reconstruction of atomic spectra (Kramers-Henneberger atom, Rabi-oscillations etc) [2] and also important for understanding of high order harmonic generation physics [3]. References [1] A.V. Bogatskaya, E.A. Volkova and A.M. Popov "Spontaneous transitions in atomic system in the presence of high intensity laser field", EPL 116, 14003 (2016). [2] A.V.Bogatskaya, A.M. Popov "Spontaneous emission of dressed atomic system in a strong light field", Proceedings of 5th International Conference on Photonics, Optics and Laser Technology, ISBN: 978-989-758-223-3, 129136 (2017). [3] A.V. Bogatskaya, E.A. Volkova and A.M. Popov "Prospects of odd and even harmonic generation by an atom in a high-intensity laser field", Laser Phys. Lett. 14, 055301 (2017).