Inelastic scattering of electrons by metastable hydrogen atoms in a laser field

Abstract

The inelastic scattering of fast electrons by metastable hydrogen atoms in the presence of a linearly polarized laser field is theoretically studied in the domain of field intensities below 10 10 W/cm 2 . The interaction of the hydrogen atom with the laser field is described by first-order time-dependent perturbation theory, while the projectile electrons interacting with the laser field are described by the Gordon-Volkov wave functions. An analytic expression is obtained for the differential scattering cross section in the first-order Born approximation for laser-assisted inelastic e − -H(2s) scattering for the 2s → nl excitation. Detailed analytical and numerical results are presented for inelastic scattering accompanied by one-photon absorption, and the angular dependence and resonance structure of the differential cross sections is discussed for the 2s → 4l excitation of metastable hydrogen.

Differential Cross-Section in the Presence of a Weak Laser Field for Inelastic Scattering

“…Therefore, the authors are using visible and UV ranges of the electron energy for hydrogen atoms, because there are no studies of the scattering in such energy interval. Some authors studied the differential crosssection with high-energy electrons from a few keV to MeV like Joachain [19], Buica [2], etc. To study the differential cross-section, one can use Nd : YAG (𝜔 = 1.17 3.1.…”

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

“…(3) and (5) of Ref. [18]. For fast projectile electrons (E ki > 150 eV) the exchange effects are safely neglected [20] and are not included in the calculation of the scattering matrix.…”

“…as well for H(2s) [18]. Obviously the expressions of the specific radial integrals I nl and J nll ′ , included in P nl and Q nl , depend on the initial and final states of the inelastic scattering process.…”

“…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. It is well known that by increasing the atomic excitation the laser-dressing effects induced by the dipole polarizability [15] should increase in importance [16,17,18], and therefore with an increasing probability of experimental detection. As far as we known the first theoretical works on the laser-assisted inelastic scattering of electrons by atoms taking into account the atomic "dressing" (i.e., the dipole distortion of the atom by the laser field) were performed in different approaches such as first-order perturbation theory [19,20,21,22], non-perturbative Floquet theory [23], or relativistic method [24].…”

“…(iii) The dressing of the hydrogen atom by the laser field is described within the first-order time-dependent perturbation theory (TDPT) in the field [36]. 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.…”