Circularly polarized He radiation for electron polarimetry

Because of the large systematic uncertainties of Mott scattering, alternative methods for more accurate absolute electron polarimetry are presently being discussed. One of them is the measurement of the circular polarization of impact radiation produced by polarized electrons. The present paper shows that the transition $3^3$P→$2^3$ ${\mathrm{S}}_1$ (388.9 nm) from the unresolved $3^3$ ${\mathrm{P}}_{\mathrm{J}}$ multiplet of helium is very appropriate for the absolute calibration of electron polarization. This can be utilized to increase the accuracy of polarization analysis with a Mott detector.