Evidence for Fermi-Shuttle Ionization in Intermediate VelocityC++XeCollisions

Abstract

Experimental evidence has been found for consecutive projectile-target-projectile (triple) and projectile-target-projectile-target (quadruple) "ping-pong" scattering of ionized target electrons in single C+ +Xe collisions at 150 and 233 keV/u impact energies. Distinct signatures of the multiple electron scattering contributions to the high-energy part (300-3400 eV) of the double differential electron spectra have been separated and identified with the help of reference measurements using He+ projectile ions and different calculations.

Ionization of small molecules induced byH+, He+, andKovács1, Herczku2, Juhász3 et al. 2016Phys. Rev. ASelf Cite

“…At higher energies, the structures nicely demonstrate the features of close collisions. The 20°curve exhibits a wide peak at 90 eV, corresponding to the enhancement of the binary encounter process due to the screened potential of the projectile [9,10]. Note that the 0°binary encounter energy is 25 eV here.…”

“…[9]. It was found earlier [9][10][11][12][13] that, due to its nonperturbative character, the CTMC model is able to quantitatively treat this type of multiple-scattering event in ∼100 keV/u collisions. From the CDW-EIS model, however, which includes only parts of the higher-order perturbation, we do not expect to describe this type of multiple scattering.…”

“…This is a key for understanding the origin of the hump. We assume that both the structure at 100 eV and the enhancement at higher energies in general are due to sequential multiple electron scattering in the Coulomb field of the ionized target and the projectile cores, i.e., the so-called Fermi-shuttle mechanism [9][10][11][12][13].…”

“…Covering the field of heavyparticle-atom collisions, the main concepts, experimental methods, and theoretical works for electron emission were reviewed by Stolterfoht, DuBois, and Rivarola in 1997 [1]. In the last two decades, remarkable new advances have been made in studying coherent electron emission from simple molecules by ion impact [2,3] and collision systems with strong perturbation [4,5], where multiple ionization [6][7][8] or multiple electron scattering (Fermi shuttle) [9][10][11][12][13] significantly contributes. Ionization in ion-molecule collisions has also been studied from the beginning of electron spectroscopy [14].…”

Atomic data for integrated tokamak modelling – Fermi-shuttle type ionization as a possible source of high energy electrons

“…The main aim of the present work is to find the possible source of generation of the high energy electrons in the plasma. At sufficiently low collision energies, it is known that the so-called Fermi-shuttle type ionization mechanism can produce high energy electrons [1,2]. Originally, Fermi proposed the mechanism as a possible source of energetic cosmic rays [3] where weak but giant magnetic fields, moving in outer space, can accelerate charged particles with extremely high energies in long sequences of reflection.…”