Madalina Boca

On the properties of the Volkov solutions of the Klein–Gordon equation

We present an elementary proof based on a direct calculation of the property of completeness at constant time of the solutions of the Klein–Gordon equation for a charged particle in a plane wave electromagnetic field. We also review different forms of the orthogonality and completeness relations previously presented in the literature and discuss the possibility of constructing the Feynman propagator for the particle in a plane-wave laser pulse as an expansion in terms of Volkov solutions. We show that this leads to a rigorous justification for the expression of the transition amplitude, currently used in the literature, for a class of laser-assisted or laser-induced processes.

Thomson scattering in the high intensity regime

Within the framework of classical electrodynamics, we investigate the scattering of a very intense laser pulse on ultrarelativistic electrons. The laser pulse is modeled by a plane wave of finite length. For a circularly polarized laser pulse, we focus on the angular distribution of the emitted radiation in its dependence on the electron energy for the cases of head-on and 90° collisions. We investigate the relation between dW/dΩ and the trajectory followed by the velocity of the electron during the laser pulse; for the case of a short laser pulse, we discuss the carrier–envelope phase effects. We also present an analysis of the polarization of emitted radiation. We present two scaling laws that allow us to predict the behavior of angular distributions for a broad range of parameters.

Electron distributions in nonlinear Compton scattering

Our calculation of the final electron distribution in nonlinear Compton scattering with very energetic electrons is performed for an electromagnetic pulse with finite duration. In contrast to the monochromatic case, this gives access to the the asymptotically free electrons and not to those dressed by the laser field.

Mott scattering of a Klein-Gordon particle in an intense laser field

We study the Mott scattering of charged spinless particles in the presence of an intense plane wave laser pulse with fixed propagation direction and arbitrary duration and shape. We derive two equivalent forms of the transition amplitude and we discuss the relation between the respective results obtained in the case of a laser pulse and the monochromatic case. We obtain the condition defining the boundaries of the “bright” domain (the domain of allowed values in the energy-direction space of the scattered particle) and we illustrate our results with numerical examples.

Resonances and antibound states for the dressed one-dimensional δ-function potential

We calculate resonances, antibound states and two new light induced states of the dressed one-dimensional attractive δ-function potential, as function of α0 — the free electron quiver motion amplitude in a monochromatic electromagnetic field, in the range 0<α0<150 a.u. We describe also our method, adequate to the numerical solution of the Schrodinger equation for this particular potential.

Non-linear Compton effect with a laser pulse

We theoretically investigate the scattering of intense laser radiation on energetic electrons. The laser field is described as a pulse with a fixed propagation direction; this allows the use of relativistic Volkov solutions and leads to a transition amplitude which is a product of a three-dimensional δ-function with an one-dimensional integral evaluated numerically. We study the dependence of the emitted photon spectrum on the pulse duration. In contrast with the monochromatic case, where the spectrum is discrete, in our case one obtains a continuous distribution with a succession of maxima located near the corresponding discrete values.