Spin Effects in the (e, 2e) Cross Section of Xenon

Granitza, B.; Guo, X.; Hurn, J.; Lower, Julian; Mazevet, S.; McCarthy, I. E.; Shen, Yanjun; Weigold, E.

doi:10.1071/ph960383

Cited by 23 publications

(14 citation statements)

References 15 publications

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“…The present elastic scattering measurements were performed using an existing (e, 2e) coincidence apparatus described in detail in an earlier publication (Granitza et al 1996). It consists of a polarized electron source housed in an ultra-high vacuum (UHV) chamber, two identical hemispherical analysers which can measure scattered electron intensity and a Mott polarimeter, whose purpose is to measure the polarization of the primary electron beam (figure 1).…”

Section: Sherman Functionmentioning

confidence: 99%

The elastic scattering of spin-polarized electrons from xenon

Dorn

Elliott

Lower

et al. 1998

J. Phys. B: At. Mol. Opt. Phys.

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Here we present experimental and theoretical results for the elastic scattering of spinpolarized electrons from xenon and the subsequent determination of the Sherman function, which is directly related to the measured spin up-down asymmetry, in the energy range between 30 and 160 eV. For our measurements, particular attention was given to minimizing the deleterious effects of finite angular resolution and background levels on the derived Sherman functions. Our theoretical results were derived from Dirac-Fock scattering calculations where, for energies above 60 eV, the effects of including a phenomenological absorption potential to account for the loss of flux into the non-elastic channels have been investigated. In general, a comparison of the new experimental results with previous data shows very good agreement, however, sharper structure is observed in some cases in the present results. A comparison of the calculated with experimental results again shows good agreement but also demonstrates that for energies above 100 eV, absorption effects must be taken into account for a detailed description of the ST U parameters.

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Section: Sherman Functionmentioning

confidence: 99%

The elastic scattering of spin-polarized electrons from xenon

Dorn

Elliott

Lower

et al. 1998

J. Phys. B: At. Mol. Opt. Phys.

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“…The analyzers [3] incorporate position sensitive detectors at their exit plane, enabling simultaneous measurement over a 6 eV energy band with a resolution of around 0.2 eV. A total coincidence (e, 2e) resolution of around 0.9 eV was achieved, more than sufficient to accurately distinguish between ionizing events occurring from atoms in their ground and excited states, which are separated in binding energy by 2.14 eV.…”

mentioning

confidence: 99%

“…1) with attention focused on the new elements, namely, the sodium source and the laser pumping system incorporated into our previously described polarized electron spectrometer [3]. 0031-9007͞98͞80(2)͞257(4)$15.00 In the apparatus, a beam of unpolarized electrons is produced by photoemission from a negative electron affinity GaAs crystal surface.…”

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confidence: 99%

Orientational Dichroism in the Electron-Impact Ionization of Laser-Oriented Atomic Sodium

et al. 1998

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We report the first experimental observation of "orientational dichroism" in electron impact-induced ionization. ͑e, 2e͒ experiments have been performed on pure angular momentum states 3P 3͞2 , m F 13 and m F 23 of the sodium atom, excited by right-and left-handed circularly polarized laser light. Our results show that the angular correlation of the final-state electron pair is strongly dependent on the m L sublevel populated. Comparison with calculation demonstrates the dependence of the dichroism on details of the scattering dynamics. [S0031-9007(97)04999-5] PACS numbers: 34.80.Dp A detailed knowledge of the ionization process is essential to our understanding of, and progress in, such diverse fields as discharge and plasma physics, fusion physics, laser physics, and the physics and chemistry of the upper atmosphere. The most accurate information on this process is derived from kinematically complete ͑e, 2e͒ experiments, in which the energies and momenta of all reaction participants and products are determined [1]. We report here on an ͑e, 2e͒ experiment in which the projection quantum number for an excited atomic target in a pure nonzero angular momentum state is also resolved. Using laser pumping techniques, an atomic sodium target is laser excited to the 3 2 P 3͞2 F 3, m F 13 or m F 23 hyperfine states. These states consist of maximal projections of the nuclear spin (I 63͞2), the orbital angular momentum (m L 61), and the electron spin (S 61͞2) along the laser beam direction.If neither the projection quantum numbers of the incident electron nor the target are resolved, the (e, 2e) differential cross section is simply a scalar invariant with respect to a joint rotation of the incoming and outgoing electron momenta p 0 , p a , and p b , respectively. This basic symmetry is destroyed by an initial orientation and/or alignment of the target. The (e, 2e) cross section is then irreducibly described by a set of tensorial parameters whose number is determined by the symmetry of the initially prepared target state [2]. Generally, the cross section for the ionization of a target with total angular momentum J can be written as [2]where L ͑i͒ 0 are tensorial components along the quantization axis of the target describing the dynamics of the ionization process and r i0 are the state multipoles describing the M-state population of the target. The transformation properties of L ͑i͒ 0 are determined by the rank i of the associated tensor. The solid angles of the momenta p a , p b with respect to p 0 are labeled by dV a , dV b , respectively.In the present case of the Na 3P 3͞2 state, neglecting spin-orbit interactions and for unpolarized primary electrons it suffices to consider Eq. (1) with respect to the orbital angular momentum L 1 for singlet and triplet scattering. Then the cross section is described only by three tensorial components L ͑i͒ 0 , which can be written in terms of the ionization cross sections for the individual magnetic substates s L,m L :L ͑2͒ 0 1 p 6 ͑s 1,1 2 2s 1,0 1 s 1,21 ͒ .The scalar component L ͑0...

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“…The predicted spin effects resulted directly from the exchange scattering amplitude and would be observable if the final Jstate of the ion could be resolved experimentally. Soon after that work, experimental measurements were performed by Granitza et al (1996) in Canberra, Australia and Hanne (1996) in Münster, Germany and significant spin effects were found. Madison et al (1996a, b) applied the JMH theory to two preliminary measurements from Australia and found good agreement in one case and poor agreement in the second case which was discounted somewhat since it corresponded to very small signals.…”

mentioning

confidence: 99%

Role of exchange scattering in spin-dependent (e,2e) collisions

Madison

Kravtsov

Mazevet

1998

J. Phys. B: At. Mol. Opt. Phys.

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One of the exciting new developments in the field of electron-impact ionization of atoms lies in the use of spin-polarized electron beams. The development of new technology which allows one to measure increasingly differential cross sections is partially motivated by the fact that the new results would be expected to serve as a more sensitive test of theory. For the last 20 years, spin-polarized electron-atom scattering has provided stringent tests of theory for elastic and inelastic scattering and the new ionization measurements will undoubtedly extend the horizons for this type of work. Probably the most important issue, however, concerns whether or not these sensitive tests can serve as a probe of new physical effects which were not previously observable. In this letter, it is demonstrated that the recent measurements of ionization of xenon using spin-polarized electrons provide information about exchange effects between the projectile electron and atomic charge cloud which would not be seen using unpolarized beams of electrons.

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Spin Effects in the (e, 2e) Cross Section of Xenon

Cited by 23 publications

References 15 publications

The elastic scattering of spin-polarized electrons from xenon

The elastic scattering of spin-polarized electrons from xenon

Orientational Dichroism in the Electron-Impact Ionization of Laser-Oriented Atomic Sodium

Role of exchange scattering in spin-dependent (e,2e) collisions

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