Effect of radiation trapping on the polarization of an optically pumped alkali-metal vapor

Abstract

Calculations are presented of the limitations imposed by radiation trapping on the electron spin polarization produced in an alkali-metal vapor by optical pumping in a large magnetic field. It is found that electron spin polarizations of 90% are possible with Na densities up to ${10}^{19}$ atoms/${\mathrm{m}}^3$ and ground-level relaxation times of 150 μs in a large magnetic field using a cylindrical geometry of radius 7.5×${10}^{\mathrm{-}3}$ m.