Spin-resolved electronic structure of the outer-most surface in the H2O/Na/Fe(001) coadsorption system: spin-polarized metastable deexcitation spectroscopy study

The spin-resolved electronic structure of the outermost surface on the coad sorption system of H2O and Na on an Fe(001) surface was investigated using spin-polarized metastable deexcitation spectroscopy (SPMDS). H2O exposure o n Fe(001) resulted in oxygen adsorption, where the SPMDS spectra and the ob served spin polarization at the outermost surface were quite similar to tho se in O/Fe(001). In contrast, OH adsorption was observed when the Na-precov ered Fe(001) surface was exposed to H2O. The change of the spin polarizatio n was found at the both SPMDS peak positions of Na 3s and OH 1 pi on the Na /Fe(001) surface during the exposure to H2O. The change of the spin polariz ation at the Na 3s and OH 1 pi peak occurred simultaneously in the low expo sure range (0-0.3 L), where polarization at Na 3s (OH 1 pi) changed to the positive (negative) direction. The observed behavior of the spin polarizati on is interpreted to indicate that the electron transfer from Na 3s to the partially vacant 1 pi orbital of OH, where the dominant transferred electro ns are thought to have anti-parallel spins to the magnetized Fe substrate i n this low exposure range. (C) 2001 Elsevier Science B.V. All rights reserv ed.