Depolarization effects in electron spin polarization of 4He+ ion beam

Spin polarization of He+ ions in Penning ionization of optically pumped He metastable atoms (He∗(23S1)) has been investigated. It was indicated that radiation trapping is a predominant depolarization effect in the He pressure range below 100 Pa. A drastic drop of He∗ polarization was observed below the He pressure of 10 Pa. The He+ polarization was estimated to be 16.6 ± 3.1% from the spin dependence of the electron spectra obtained on a magnetized sample surface (spin-polarized ion neutralization spectroscopy).