Spin-resolved triple differential cross sections of xenon

Spin- and fine-structure resolved results for the inner-shell ionization of argon are presented. By performing measurements and relativistic scattering calculations under kinematical conditions where the contribution from the exchange between the scattered electrons and the electrons in the residual ion is small, the effect of target fine structure on the measured spin asymmetry has been highlighted. Fully relativistic distorted wave Born approximation calculations are found to be in good agreement with both the spin asymmetry and branching ratio measurements.

Section: R = σmentioning

confidence: 99%

Spin asymmetries in the electron-impact ionization of Ar(2p)

Bellm

Lower

Kampp³

et al. 2006

“…It first became apparent through the investigation of (e, 2e) processes for spin polarized electrons. Investigations of spin effects have been performed for inert gases (Duemmler et al 1993, Dorn et al 1997, Mette et al 1998 and the alkali atoms (Baum et al 1992). When experiment and theory were compared for the inert gases, it was found that the standard first-order DWBA was in good accord with the spin asymmetry measurements in some cases but not others.…”

Section: Introductionmentioning

confidence: 99%

Exchange effects in low energy electron impact ionization of the inner and outer shells of argon

Biava

Saha

Engel

et al. 2002

Self Cite

First order distorted wave Born approximation (DWBA) triple differential cross sections are reported for low-energy electron-impact ionization of the inner 3s and outer 3p shells of argon. Previous DWBA works have demonstrated that experiment and theory are not in accord for low energy ionization of inert gases and here we investigate the importance of exchange scattering. Different approximations for treating exchange scattering are investigated. It is shown that exchange scattering is particularly important for 3s ionization. Even with a proper treatment of exchange, the first order calculations are still not in satisfactory agreement with experiment. Consequently higher order effects will have to be included to achieve a satisfactory description of the low-energy ionization process. We also investigated both the Hartree-Fock and optimized potential methods for calculating atomic wavefunctions and static potentials and found that both methods produced almost the same cross sections.

“…One of the recent advances in the field of atomic ionization by electron impact (e, 2e) lies in the use of polarized electron projectiles. Investigations of spin effects have been performed for inert gases (Duemmler et al 1993, Dorn et al 1997, Mette et al 1998 and the alkali atoms (Baum et al 1992). When experiment and theory were compared for the inert gases, it was found that the standard first-order distorted-wave Born approximation (DWBA) was in good accord with the spin-asymmetry measurements in some cases but not others.…”

Section: Introductionmentioning

confidence: 99%

Hartree-Fock treatment of exchange in (e,2e) collisions

Winkler

Madison

Saha

1999

Self Cite

The distorted-wave Born approximation has been very successful for treating electron-impact ionization (e,2e) of heavy atoms for high-energy incident electrons. However, as the energy of the incident electrons approaches threshold, significant differences between experiment and theory are observed. In these calculations, the continuum projectile electron wavefunction is typically calculated using the static field of the atom plus a local approximation for electron exchange. While this approximation is believed to be reasonable for higher energies, it is likely to become unreliable for energies near threshold. Here we report a proper treatment of electron exchange in which a full Hartree-Fock calculation is performed for both the atomic and projectile electrons. For the initial state, the projectile orbitals are calculated in the Hartree-Fock approximation with full exchange with the target electrons and for the final state, the Hartree-Fock continuum orbitals are computed for an ion. It is found that the static-exchange approximation is not valid for lower incident energy projectiles.