20-09-2013, 01:11 PM
Optically Pumped Electron Spin Filter
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ABSTRACT
This paper reports the first experimental demonstration of an optically pumped electron spin filter. Unpolarized electrons produced in a cold-cathode discharge drift through a mixture of spin-polarized Rb and a nitrogen or helium buffer gas. Through spin-exchange collisions with the Rb, the drifting electrons become polarized along the optical pumping axis. We study the role of the buffer gas in both the optical pumping and the spin transfer to the free electrons.
INTRODUCTION
This Letter reports the experimental demonstration of a new kind of polarized electron source: an optically pumped electron spin filter. Polarized electrons are an indispensable probe of spin-dependent phenomena in many areas of physics [1 – 3], but they are difficult to produce. State-of-the-art sources of polarized electrons use either photoemission from negative-electron-affinity GaAs (or variants of its basic structure) [3,4] or chemi-ionization of optically pumped metastable Hep [5,6]. Both of these methods can yield average currents on the order of 100 mA with polarizations in excess of 70%. Unfortunately, such sources are technically and operationally complex.