Threshold phenomena in electron-atom scattering in a laser field

Abstract

Follow this and additional works at: https://digitalcommons.unl.edu/physicsstarace Part of the Physics Commons Manakov, N. L.; Starace, Anthony F.; Flegel, A. V.; and Frolov, M. V., "Threshold Phenomena in

Plateau Structure in Resonant Laser-Assisted Electron-Atom Scattering

“…is different for l ¼ 0 and 1 [4]. We give here only those results for s scattering needed for later discussions (cf.…”

“…However, for all processes the absolute values of the n-photon rates in the plateau region are orders of magnitude smaller than in the region of small n. Hence, mechanisms for increasing rates on the plateau are of great interest. For LAES, two such mechanisms exist: thresholdrelated phenomena at the closing of the stimulated multiphoton emission channel [4] and resonance scattering. These two mechanisms occur under different conditions: the former occur at incident electron energies equal to multiples of the photon energy, while the latter occurs for those electron energies at which the electron is temporarily captured (following stimulated emission of laser photons) in a bound state of the potential UðrÞ of the target atom (or positive ion) and then detached (or ionized) by absorbing n þ photons.…”

“…One sees that the threshold enhancements of d n =d p n are much lower than the resonant ones. Moreover, the former disappear in the high-energy part of the plateau [4] [cf. Fig.…”

“…As a result, the scattering state, È E ðr; tÞ, of the electron within TDER theory has an analytic form in terms of Gðr; t; r 0 ; t 0 Þ and a periodic function, f p ðtÞ, that enters the boundary condition for È E ðr; tÞ inside the potential well UðrÞ (i.e., for r & r c ). It contains complete information on the modification of the electron-atom interaction by the laser field [4].…”

“…Since resonant phenomena disappear in a perturbative treatment of the potential UðrÞ, both the electron-atom and electron-laser interactions must be treated nonperturbatively. For this purpose, we employ the time-dependent effective range (TDER) theory [4], which extends effective range theory (ERT) [8] for lowenergy elastic electron scattering from a short-range potential UðrÞ to the case of LAES. Thus the main approximation in the TDER theory is the same as in ERT: the interaction of an incident electron with an atomic potential UðrÞ is taken into account only in the l-wave channel, by means of the scattering phase l ðEÞ, which is parametrized in terms of the scattering length a l and the effective range r l .…”