Chapter 4 Physics and Technology of Polarized Electron Scattering from Atoms and Molecules

Gay, T. J.

doi:10.1016/s1049-250x(09)57004-8

Cited by 47 publications

(38 citation statements)

References 216 publications

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“…Mott polarimetry techniques have been reviewed a number of times (see, e.g., [34][35][36][37][38][39]) as having the essential performance characteristics of different polarimeters (see [40][41][42]). Here the focus is on polarimetry for photoemission including a number of important recent advances.…”

Section: Spin Polarimetry Techniques and Data Handlingmentioning

confidence: 99%

“…The calibration techniques possible in Mott polarimetry have been appraised critically by Gay and Dunning [36,39,85]. They include extrapolation of measured polarimeter asymmetries to zero foil thickness or zero inelastic energy loss, followed by normalization to the calculated Sherman function for single atom scattering, undertaking double scattering, or using electrons of known polarization.…”

Section: Polarimeter Calibrationmentioning

confidence: 99%

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Spin-Resolved Valence Photoemission

Seddon

2014

Handbook of Spintronics

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Spin-resolved valence photoemission has recently seen a resurgence of interest fostered by exciting results in a range of interesting materials. Reviewed here are the basics of, the instrumentation for, and techniques useful in spin-resolved photoemission, together with illustrative examples of its utilization for materials of general importance and of particular relevance to spintronics applications. The example materials are broadly classified into nonmagnetic and magnetic systems. The former covers Rashba systems and topological insulators. The latter includes thin films, half-metals, adsorbates and induced moments, and, finally, a short section on imaging. The review is not intended to be comprehensive in its coverage but rather to provide an introduction to hardware and techniques together with an overview of selected results and state-of-the-art developments. List of Abbreviations 1DOne

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Section: Spin Polarimetry Techniques and Data Handlingmentioning

confidence: 99%

Section: Polarimeter Calibrationmentioning

confidence: 99%

Spin-Resolved Valence Photoemission

Seddon

2014

Handbook of Spintronics

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“…With ethylene, we have measured electron currents of 4 μA simultaneously with electron polarizations of 24%. This work offers the promise of a simple, benchtop, "turnkey" source of polarized electrons.The use of polarized electrons is widespread in physics, from probing of the spin structure of nucleons and nuclei [1] to studying magnetic domain structure [2] and the spin dependence of atomic collisions [3]. The additional information provided by studies with incident polarized-electron beams comes at a price: The technological demands of polarized-electron sources are severe.…”

mentioning

confidence: 99%

“…The observation of handedness-specific scattering provides information about novel molecular collision dynamics [3], as well as possible clues to the mystery of why all naturally occurring DNA has the same handedness [7]. In tabletop experiments with vapor targets, such as ours, destruction of the photocathode's NEA surface conditions by organic and other vacuum contaminants can make GaAs sources unusable or, at best, highly problematic.…”

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confidence: 99%

Optically pumped spin-exchange polarized-electron source

Pirbhai

2013

Phys. Rev. A

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We describe the operation of a prototype polarized-electron source. Rubidium vapor, contained in a cell, is optically pumped in the presence of a buffer gas. Unpolarized electrons from a tungsten filament are injected into the cell and extracted after undergoing spin exchange with the Rb atoms. We compare the performance of the source when different buffer gases are used. We measure a decrease in electron polarization as their injection energy increases, but find an unexpected regime at higher injection energies yielding increased electron polarization accompanied by a 40-fold increase in current, suggesting the production of slow secondary electrons in the target cell. With ethylene, we have measured electron currents of 4 μA simultaneously with electron polarizations of 24%. This work offers the promise of a simple, benchtop, "turnkey" source of polarized electrons.The use of polarized electrons is widespread in physics, from probing of the spin structure of nucleons and nuclei [1] to studying magnetic domain structure [2] and the spin dependence of atomic collisions [3]. The additional information provided by studies with incident polarized-electron beams comes at a price: The technological demands of polarized-electron sources are severe. The current state-ofthe-art source technology is based on photoemission from negative electron affinity (NEA) strained GaAs photocathodes [4,5]. The modern GaAs source can produce high-current (ß1 mA), high-brightness beams with ࣙ80% polarization. Also, importantly, it is optically reversible; the electron-spin direction can be flipped by reversing the helicity of the light producing photoemission from the GaAs. This enables a relatively straightforward diagnosis of systematic experimental error due to instrumental asymmetries. The biggest drawback of the GaAs source is that it is difficult to operate, particularly with regard to production of the NEA conditions that allow reasonable photocurrents to be extracted. In university labs, the learning curve for reliable graduate student operation of such sources is measured in months (or years); at accelerators, e.g., CEBAF, a dedicated scientific staff maintains and runs these sources. Several attempts to develop the GaAs source into a "blackbox" commercial technology have failed [6].We are currently investigating the interaction of longitudinally polarized electrons, which are chiral, with chiral molecular targets. The observation of handedness-specific scattering provides information about novel molecular collision dynamics [3], as well as possible clues to the mystery of why all naturally occurring DNA has the same handedness [7]. In tabletop experiments with vapor targets, such as ours, destruction of the photocathode's NEA surface conditions by organic and other vacuum contaminants can make GaAs sources unusable or, at best, highly problematic. If a different, user-friendly source of polarized electrons, such as the one we describe here, were widely available, it could enable a broad range of experiments, including those in...

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“…All present commercial spin-polarization detectors [7][8][9] are based on single-channel electron scattering and are characterized by a figure of merit of typically 10 À4 since the early 1980s, when two of the authors employed Mott scattering in a gas-phase photoemission experiment [10] and introduced spin-polarized low-energy electron scattering (SPLEED) as an ultra high vacuum (UHV)-compatible method for spin polarimetry [11]. Typical widely used instruments are described in Ref.…”

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confidence: 99%

Highly Efficient Multichannel Spin-Polarization Detection

et al. 2011

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Since the original work by Mott, the low efficiency of electron spin polarimeters, remaining orders of magnitude behind optical polarimeters, has prohibited many fundamental experiments. Here we report a solution to this problem using a novel concept of multichannel spin-polarization analysis that provides a stunning increase in efficiency by 4 orders of magnitude. This improvement was demonstrated in a setup using a hemispherical electron energy analyzer. An imaging setup proved the principal capability of resolving more than 10(5) data points in parallel.

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Chapter 4 Physics and Technology of Polarized Electron Scattering from Atoms and Molecules

Cited by 47 publications

References 216 publications

Spin-Resolved Valence Photoemission

Spin-Resolved Valence Photoemission

Optically pumped spin-exchange polarized-electron source

Highly Efficient Multichannel Spin-Polarization Detection

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