Hyperfine interaction studies on swift O-ions emerging with polarized electrons from ferromagnetic layers into vacuum

A precision plunger set-up was used to determine in time-differential measurements of hyperfine interactions the degree of polarization of 1s- and 2s-electrons in H- and Li-like oxygen ions on their emergence from magnetized Ni- and Gd-layers into vacuum. In addition a time-integral measurement with Fe-layers served to obtain the polarization of 2s-electrons only. For all three ferromagnetic materials the degree of polarization of 2s-electrons is found to be twice as large as for 1s-electrons. The data are discussed in the context of transient magnetic fields and their underlying polarization mechanism.