Optically Pumped Electron Spin Filter

Batelaan, Herman; Green, A. S.; Hitt, B. A.

doi:10.1103/physrevlett.82.4216

Cited by 30 publications

(23 citation statements)

References 23 publications

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“…No readily accessible techniques are available [19] to analyze the spin polarization of a nonrelativistic femtosecond electron pulse. Techniques for nonpulsed beams include Mott scattering [20], optical polarimetry [21], Rb spin filter [22], and others. The most well-known and widely used Mott scattering requires currents exceeding 1 pA [23].…”

Section: Introductionmentioning

confidence: 99%

Spin-dependent two-color Kapitza-Dirac effects

et al. 2015

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In this paper we present an analysis of the spin behavior of electrons propagating through a laser field. We present an experimentally realizable scenario in which spin-dependent effects of the interaction between the laser and the electrons are dominant. The laser interaction strength and incident electron velocity are in the nonrelativistic domain. This analysis may thus lead to novel methods of creating and characterizing spin-polarized nonrelativistic femtosecond electron pulses.

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Section: Introductionmentioning

confidence: 99%

Spin-dependent two-color Kapitza-Dirac effects

et al. 2015

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“…The beam passes through a clean-up linear polarizer and quarter-wave plate before entering a test cell ∼5 cm long containing Rb vapor with a natural isotopic abundance. The Rb density, N Rb , is ∼10 13 cm −3 in this cell, comparable to the density used for our optically pumped Rb electron spin filter [7]. The cell also includes N 2 buffer gas at a pressure of 0.1, 1.0, or 10 torr.…”

Section: Methodsmentioning

confidence: 78%

“…Storage of light in a warm alkali-metal vapor is effected with little or no buffer gas and with spectrally narrow, low-power lasers, while systems that use spin-exchange optical pumping to generate polarized noble gases tend to use high buffer-gas pressures (∼1000 torr) and broad, high-power lasers. The work reported here deals with a third regime, using somewhat broad, high-power lasers with low pressures (∼1 torr) of buffer gas [6,7]. These conditions are optimal to generate a beam of electrons polarized through spin exchange with a spin-polarized optically pumped alkali-metal target [7].…”

Section: Introductionmentioning

confidence: 99%

“…The work reported here deals with a third regime, using somewhat broad, high-power lasers with low pressures (∼1 torr) of buffer gas [6,7]. These conditions are optimal to generate a beam of electrons polarized through spin exchange with a spin-polarized optically pumped alkali-metal target [7]. The necessity of passing the electrons through the alkali-metal (Rb) vapor requires that the buffer-gas pressures be modest to maintain an appreciable electron current.…”

Section: Introductionmentioning

confidence: 99%

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Electron-spin-reversal phenomenon in optically pumped rubidium

2010

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We have studied the optical pumping of mixtures of Rb vapor and N 2 buffer gas by laser light tuned to the D 1 transition having a spectral width of ∼500 MHz. The Rb densities are of the order of 10 13 cm −3 , while the buffer-gas pressures range from 0.1 to 10 torr. As the frequency of the right-hand circularly polarized laser is varied across the D 1 absorption profile, the electron spin polarization of the Rb is found to take on negative values for small negative values of pump detuning from the absorption profile center. This occurs for N 2 pressures below ∼1 torr; at 10 torr the electron spins consistently point in the same direction as the angular momentum of the pump light. The spin-reversal effect can be understood in terms of populations of the F = 2 ( 85 Rb) and F = 1 ( 87 Rb) states caused by small unpolarized fractions in the pump beam and its elimination in terms of pressure broadening caused by the N 2 buffer gas. We speculate that this effect could be used for fast Rb spin modulation.

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“…We have demonstrated the proof of principle for an alternative method to produce spin-polarized electrons using spin exchange between unpolarized electrons and optically pumped Rb [8]:…”

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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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Optically Pumped Electron Spin Filter

Cited by 30 publications

References 23 publications

Spin-dependent two-color Kapitza-Dirac effects

Spin-dependent two-color Kapitza-Dirac effects

Electron-spin-reversal phenomenon in optically pumped rubidium

Optically pumped spin-exchange polarized-electron source

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