Resonant Spontaneous Bremsstrahlung of Ultrarelativistic Electrons in the Field of a Nucleus and a Laser Wave

Abstract

The actual theoretical research focuses on the resonant spontaneous bremsstrahlung (RSB) of ultrarelativistic electrons under the condition of scattering on a nucleus in a laser field. The represented energies of ultrarelativistic electrons are of considerable magnitudes $E_{thr} >rsim 5\div 10^{6}$ MeV and the intensity of the laser wave is $I \lesssim 10^{16}\frac{\mathrm{w}}{\mathrm{cm}^{2}}$ . In the resonant state the intermediate virtual electron in the laser field transforms into a real particle. As a result of the characterized effect the original second order process with accordance to the fine structure constant effectively splits into two consequent first-order processes: the laser-stimulated Compton effect and the laser-assisted Mott scattering process of an electron on a nucleus. The indication of resonances in a laser field is a significant phenomena for investigations in Quantum Electrodynamics. Constructive analysis illustrates the resonant kinematics of the RSB process in which the initial and final ultrarelativistic electrons in addition to spontaneous high-energy photon propagate in a narrow cone. Furthermore, it is important to emphasize that the development of the studied process possesses two probable channels of reaction. Therefore, the first channel determines the process of emission of a spontaneous photon by an initial electron in the field of a wave (laser-stimulated Compton effect) with the sequential scattering on a nucleus (laser-assisted Mott process). The second channel - defines the process of the scattering of an initial electron on a nucleus with the consecutive spontaneous photon emission in the field of a laser. Moreover, the resonant frequency of a spontaneous photon depends substantially on the channel of the interaction. The detailed verification validates that with implementation of the equal initial parameters to the system the resonant frequency in the first channel constantly exemplifies a deficient magnitude level corresponding to the resonant frequency in the second channel. Complementary to the described discrepancy the emission angle of the spontaneous photon in the first channel particularly specify the resonant frequency contrary to the second channel that produces a spectrum range for the emission angles referring three various magnitudes for the resonant frequency value. Nevertheless, the physical calculations estimate that with the exclusion of the scattering of an electron at a zero angle the first and second channel correlations do not interfere. To summarize, the result provides computation of the resonant differential scattering cross section of the process. In conclusion, the research indicates that the considered resonant differential scattering cross section characteristically exceeds the according cross section of a spontaneous bremsstrahlung in the absence of an external field. Numerous scientific facilities of pulsed laser radiation (SLAC, FAIR, XFEL, ELI, XCELS) may experimentally verify the project calculations.