Excitation of the hydrogen atom by fast-electron impact in the presence of a laser field

Abstract

An approach has been developed to study the excitation of a ground-state H atom to the n =2 level under the simultaneous action of fast-electron impact and a monochromatic, linearly polarized, homogeneous laser beam. The laser frequency is assumed to be low (soft-photon limit) so that a stationarystate perturbation theory can be applied as is done in the adiabatic theory. An elegant method has been developed in the present work to construct the dressed excited-state wave functions of the H atom using first-order perturbation theory in the parabolic coordinate representation. By virtue of this method, the problem arising due to the degeneracy of the excited states of the H atom has been successfully overcome. The main advantage of the present approach is that the dressed wave function has been obtained in terms of a finite number of Laguerre polynomials instead of an infinite summation occurring in the usual perturbative treatment. The amplitude for direct excitation (without exchange) has been obtained in closed form. Numerical results for differential cross sections are presented for individual excitations to different Stark manifolds as well as for excitations to the n =2 level at high energies (100 and 200 eV) and for field directions both parallel and perpendicular to the incident electron momentum. Extension to a higher order of perturbation is also possible in the present approach for the construction of the dressed states, and the electron-exchange effect can also be taken into account without any further approximation.

Laser assisted excitation in electron–hydrogen-like ion collisions

“…Regarding the shape of the DCS curves, it may be noted from figures 1 and 2 that the field free (FF) DCS curves fall off monotonically with increasing scattering angle while the field assisted (for l = 0, +1) curves exhibit some oscillations arising due to the occurrence of the Bessel functions J l (x) in the expression for the transition amplitude (see equation (22)). However, the number of oscillations in the l = 0, ±1 curves is found to increase (see figures 1 and 2) with the increasing field strength for the following reason.…”

“…In later works the Coulomb-Volkov (CV) wavefunction was also used by several workers [12,14,15] in the context of different laser assisted/induced procssses. Although the approximate CV solution presents the advantage of containing the field to all orders (inherent in the plane wave Volkov solution [11,[16][17][18][19][20][21][22][23]), it completely decouples the electron-laser and the electron-screened-ion interactions [18]. The laser-ion interaction (i.e.…”

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

“…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].…”

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

“…Theoretical works on the laser-assisted inelastic scattering of electrons by the hydrogen atom in its ground state by taking into account the atomic "dressing" (i.e. the dipole distortion of the atom by the laser field) in first-order perturbation theory were performed by Jetzke and co-workers [12], Francken and co-workers [13], Bhattacharya and co-workers [14], and Cionga and Florescu [15]. Lately Voitkiv and co-workers [16] have considered laser-assisted inelastic collisions of relativistic electrons with atomic targets in their ground state.…”