Polarisation effect of laser field in inelastic electron - hydrogen collisions

Electron-atom scattering in a circularly polarized laser field

“…The laser dressing of the atomic target was treated in second order perturbation theory, while that of the scattering electron was described by a Volkov solution. Within this approximation scheme, we were able to show that the nonlinear cross sections dσ CP N /dΩ neither depend on the dynamical phase φ q , contrary to what was predicted by earlier work on this topic [20], [22], nor is there any indication of circular dichroism. In our derivation of the above findings we devoted particular attention to the proper definition of the phases in Graf's addition theorem of Bessel functions, basing our considerations on the corresponding definitions in Watson's book [28].…”

Polarization dependence in inelastic scattering of electrons by hydrogen atoms in a circularly polarized laser field

“…This theoretical approach is similar to the one that has been used to a related problem of laser-assisted excitation collisions e − + H(2s) by LP laser fields [18] and, contrasting with this work, the main differences reside in the initial atomic state, that is now 1s, and the circular polarization of the laser field, which result in different specific expressions for the projectile and atomic contributions to DCS by CP fields. In comparison to the earlier theoretical works [20,22,14] the present semi-perturbative approach provides, for the first-time as far as we know, a closed analytical form for the DCS, which includes the atomic dressing effects, and is valid for both LP and CP fields. We obtain useful analytic formulas for DCSs in the laser-assisted inelastic scattering in the perturbative limit as well in the soft-photon limit for the 1s → nl excitation.…”

“…Theoretical studies involving CP fields with the atomic dressing taken into account in second-order of time-dependent perturbation theory (TDPT) were performed for elastic case by Cionga and coworkers [11,12], and the dichroism of the scattered electrons was investigated in elastic electron-hydrogen scattering by circularly and elliptically polarized laser fields [13]. The polarization effects in laser-assisted electron-atom inelastic collisions for the excitation of the n = 2 and 3 states in H and He, were reported [14] for two specific scattering geometries where the wave vector of the CP field is coplanar and parallel to the scattering plane. A different method based on a discrete basis of Sturmian functions was employed to calculate the relevant atomic terms of the scattering matrix and, in contrast to this previous treatment, a major purpose of our paper is to provide new analytical formulas needed to compute the differential cross section (DCS) for the laser-assisted excitation collisions e − + H(1s) by CP laser fields, that allow further investigations of the polarization effect and give more insight into the scattering process.…”

Simultaneous Excitation of Helium by Means of an Electron and a Photon: A Joined Experimental and Theoretical Study

“…The wave functions ψ i , ψ f , and ψ n are the stationary states associated with the eigenenergies E i , E f , and E n of the helium target, respectively. These states were evaluated using the Sturmian approach (see [26,34,36]).…”