Field correlation effects in laser-assisted electron scattering: the phase diffusion model

The authors present a theory of the potential scattering in the presence of a laser field taken with a well stabilised amplitude and a randomly fluctuating phase (phase diffusion model, PDM), and investigate the structure of the scattering lineshapes in the weak- and strong-field limits. The field, with its statistics, enters the theoretical treatment in a non-perturbative way. This gives the possibility of obtaining new information on the role of the statistical properties of the radiation fields in highly non-linear domains of the matter-field interaction, which complements in a significant way what is presently known. The PDM results are compared with those relative to a chaotic field (multimode laser field with a large number of uncorrelated modes). The broadening of the scattering lines is found to be controlled in an essential way by several parameters (field bandwidth, strength of the particle-field coupling, field intensity and so on); among them, the multiplicity of the exchanged photons becomes the most important only in the limit of weak coupling. In the strong-coupling limit, a chaotic field (i.e. a field undergoing amplitude and phase fluctuations) is found to broaden the scattering lines in a more effective way than a PDM field.