Electron Spin Polarization in Optically Pumped HELIUM-4.

A source of spin-polarized electrons based on a laser-pumped flowing helium afterglow is described. He(23S) atoms contained in the afterglow are optically pumped using circularly polarized 1.08-μm (23S→23P) radiation provided by a NaF (F2+)* color-center laser. Spin angular momentum conservation in subsequent chemi-ionization reactions with CO2 produces polarized electrons that are extracted from the afterglow. At low currents, ≲1 μA, polarizations of ∼70%–80% are achieved. At higher currents the polarization decreases, falling to ∼40% at 50 μA. The spin polarization can be simply reversed (P→−P) and the source is suitable for use in the majority of low-energy spin-dependent scattering experiments proposed to date.A source of spin-polarized electrons based on a laser-pumped flowing helium afterglow is described. He(23S) atoms contained in the afterglow are optically pumped using circularly polarized 1.08-μm (23S→23P) radiation provided by a NaF (F2+)* color-center laser. Spin angular momentum conservation in subsequent chemi-ionization reactions with CO2 produces polarized electrons that are extracted from the afterglow. At low currents, ≲1 μA, polarizations of ∼70%–80% are achieved. At higher currents the polarization decreases, falling to ∼40% at 50 μA. The spin polarization can be simply reversed (P→−P) and the source is suitable for use in the majority of low-energy spin-dependent scattering experiments proposed to date.

Review of Scientific InstrumentsMar 1, 198332 citations

Spin polarization in a two-dimensional electron gas

B. Davoudi, Monica Tosi

arXiv:cond-mat/0107519Physica B Condensed MatterAug 26, 200210 citations

Enhanced polarization of electron spins in He4 by simultaneous optical pumping with circularly and linearly polarized resonance radiation

L. D. Schearer, Padetha Tin

The polarization of helium (2 $^{3}$ ${\mathit{S}}_{1}$ ) metastable atoms saturates at 50% when the ensemble is optically pumped with the ${\mathit{D}}_{0}$ (2 $^{3}$ ${\mathit{S}}_{1--}$2 $^{3}$ ${\mathit{P}}_{0}$ ) transition. We have obtained polarizations approaching 100% with a simple, straightforward modification to the conventional experimental arrangement. The addition of a small amount of \ensuremath{\pi}-polarized ${\mathit{D}}_{0}$ light incident on the cell perpendicular to the defining field direction doubles the polarization produced by circularly polarized ${\mathrm{\ensuremath{\sigma}}}^{+}$ light along the field direction. A simple rate-equation model illustrates the enhancement.The polarization of helium (2 $^{3}$${\mathit{S}}_{1}$) metastable atoms saturates at 50% when the ensemble is optically pumped with the ${\mathit{D}}_{0}$ (2 $^{3}$${\mathit{S}}_{1--}$2 $^{3}$${\mathit{P}}_{0}$) transition. We have obtained polarizations approaching 100% with a simple, straightforward modification to the conventional experimental arrangement. The addition of a small amount of \ensuremath{\pi}-polarized ${\mathit{D}}_{0}$ light incident on the cell perpendicular to the defining field direction doubles the polarization produced by circularly polarized ${\mathrm{\ensuremath{\sigma}}}^{+}$ light along the field direction. A simple rate-equation model illustrates the enhancement.

Physical Review AOct 1, 19905 citations

The polarization of helium (2

^{3}

{\mathit{S}}_{1}

) metastable atoms saturates at 50% when the ensemble is optically pumped with the

{\mathit{D}}_{0}

^{3}

${\mathit{S}}_{1--}$2

^{3}

{\mathit{P}}_{0}

) transition. We have obtained polarizations approaching 100% with a simple, straightforward modification to the conventional experimental arrangement. The addition of a small amount of \ensuremath{\pi}-polarized

{\mathit{D}}_{0}

light incident on the cell perpendicular to the defining field direction doubles the polarization produced by circularly polarized ${\mathrm{\ensuremath{\sigma}}}^{+}$ light along the field direction. A simple rate-equation model illustrates the enhancement.