Spin-resolved electronic structure of the outermost surface in the H2O/Na/Fe(0 0 1) coadsorption system: spin-polarized metastable deexcitation spectroscopy study

The spin-resolved electronic structure of the outermost surface on the coadsorption system of H2O and Na on an Fe(0 0 1) surface was investigated using spin-polarized metastable deexcitation spectroscopy (SPMDS). H2O exposure on Fe(0 0 1) resulted in oxygen adsorption, where the SPMDS spectra and the observed spin polarization at the outermost surface were quite similar to those in O/Fe(0 0 1). In contrast, OH adsorption was observed when the Na-precovered Fe(0 0 1) surface was exposed to H2O. The change of the spin polarization was found at the both SPMDS peak positions of Na 3s and OH 1π on the Na/Fe(0 0 1) surface during the exposure to H2O. The change of the spin polarization at the Na 3s and OH 1π peak occurred simultaneously in the low exposure range (0–0.3 L), where polarization at Na 3s (OH 1π) changed to the positive (negative) direction. The observed behavior of the spin polarization is interpreted to indicate that the electron transfer from Na 3s to the partially vacant 1π orbital of OH, where the dominant transferred electrons are thought to have anti-parallel spins to the magnetized Fe substrate in this low exposure range.