Spin-polarized electron capture during ion impact on a ferromagnetic surface

25-keV He⁺ ions are scattered from a clean and Mn-covered (1 ML) Fe(100) surface. The spin polarization of electrons captured into excited 3³P states of He atoms is probed via an analysis of polarized fluorescence light. For projectiles impinging from grazing to normal incidence we observe the same spin polarization of captured electrons. By a coverage of 1 ML of Mn atoms we demonstrate the surface sensitivity of the method and discuss its potential for spin-sensitive microscopy and sputter depth profiling.