<p>An electron-spin polarized <sup>4</sup>He<sup>+</sup> ion beam is useful for analyzing the spin polarization on outermost surfaces (spin-polarized ion scattering spectroscopy). This is because the neutralization of the He<sup>+</sup> ion (the Auger neutralization) in the vicinity of the surface is dependent on the spin due to the Pauli principle. Thus, the element-selective spin polarization of the outermost surface is analyzed from the spin-dependent ion scattering (the spin asymmetry). We recently found that the spin asymmetry also appears on the surface of a non-magnetic material. The appearance of the spin asymmetry is quantitatively interpreted in terms of the anomalously large spin-orbit coupling (SOC) in the quantum mechanical intermediate state, where the SOC transiently acts on the spin of the virtually created hole in the target during the He<sup>+</sup> ion-target atom binary collision.</p>