Polarization-induced resonances in the stimulated bremsstrahlung spectrum of quasi-classical electrons scattered by multiply charged ions

Approximation of a constant current is employed to calculate the cross sect ion of stimulated bremsstrahlung of quasi-classical electrons scattered by multiply charged ions in the presence of a laser held nearly resonant to th e natural frequency of the ionic core. The influence of the nondipole chara cter of the interaction between an electron being scattered and bound elect rons of an ion is investigated. Calculations are carried out in the Coulomb approximation in the motion of an incident particle, which implies that th e condition Z(i) much greater than N-e is satisfied (Z(i) is the ion charge and N-e is the number of bound electrons in the ionic core). Different typ es of resonant transitions are considered: (i) Delta n = 0 and (ii) Delta n = 1 in hydrogen- and lithium-like ions. It is demonstrated that a correct description of the process under study always requires analysis of the infl uence of the nondipole character of interaction. In case (i), due to the no ndipole character of interaction, a spectral dip in the area of destructive interference of polarization and static channels of stimulated bremsstrahl ung vanishes. In case (ii), nondipole effects appreciably change the spectr al line shape within the entire frequency range near the resonance, levelin g the asymmetry. A considerable asymmetry of the line shape is observed for the spectral cross section differential in the angle of scattering of an i ncident particle. As the angle of scattering is changed, the differential c ross section features some kind of asymmetry inversion.