Arturo Bambini

Single-particle theory of the free-electron laser in a moving frame

We give a summary of the theory of a single electron involved in free-electron laser (FEL) operation. We use the method of transformation to a predetermined moving frame where the wiggler-laser scattering process is elastic. In this paper, we discuss the classical and quantum dynamics of such an electron and evaluate perturbatively the lowest order FEL behavior from the classical pendulum equation. The presentation is tutorial throughout and stresses analytic results and physically significant dimensionless parameters. No results are included for the dynamic evolution of the light during the laser action.

Laser-induced collisional energy transfer

Abstract A review of the status of theoretical and experimental work on Laser-Induced Collisional Energy Transfer (LICET) is presented. The process involves two dissimilar atoms, one of which is excited, colliding in the presence of a laser field. If the radiation field is properly tuned to an interatomic resonance, the initially excited system undergoes a transition to its ground state, while its partner gains both the excitation energy and that of a photon. The transfer cannot occur unless both collisional and radiative interactions are present. The line shape of the excitation spectrum, markedly asymmetric, is closedly related to the interaction dynamics. Details of theories applicable to low intensities, as well as their high-field counterparts are discussed, as are the predictions of spectral shapes and comparison with measurements. The treatment is extended to include studies of magnetic-state and electronic-state coherences, allowing an additional insight into the nature of the process. Representative experimental investigations are surveyed, including a detailed description of experimental arrangements specifically designed for high-accuracy spectral measurements. Finally, it is shown how a wider approach to the LICET process, by considering it as a radiative transition of a transient molecule, can be promising for an improved understanding of the problem.

Power Series Solutions for the Free Electron Laser

In this paper we use the formulation of the free-electron problem introduced earlier by the present authors. We derive a coupled set of equations for the moments of the electron distributions and solve these as power series in a dimensionless intensity parameter. This way we obtain saturation corrections to the gain and momentum distribution. We are also able to calculate the lowest order quantum corrections. All results are expressed as functions of the interaction time. Comparisons with earlier calculations are given. The lowest order saturation term is found to describe the gain unexpectedly well.