The electronic properties of mixed valence hydrated europium chloride thin film

Abstract

We investigate the electronic properties of a model mixed-valence hydrated chloride europium salt by means of high resolution photoemission spectroscopy (HRPES) and resonant photoemission spectroscopy (RESPES) at the Eu 3d → 4f and 4d → 4f transitions. From the HRPES spectra, we have determined that the two europium oxidation states are homogeneously distributed in the bulk and that the hydrated salt film is exempt from surface mixed valence transition. From the RESPES spectra, the well separated resonant contributions characteristic of divalent and trivalent europium species (4f(6) and 4f(7) final states, respectively) are accurately extracted and quantitatively determined from the resonant features measured at the two edges. The partial absorption yield spectra, obtained by integrating the photoemission intensity in the valence-band region, can be well reproduced by atomic multiplet calculation at the M(4,5) (3d-4f) absorption edge and by an asymmetric Fano-like shape profile at the N(4,5) (4d-4f) absorption edge. The ratio of Eu(2+) and Eu(3+) species measured at the two absorption edges matches with the composition of the mixed valence europium salt as determined chemically. We have demonstrated that the observed spectroscopic features of the mixed valence salt are attributed to the mixed-valence ground state rather than surface valence transition. HRPES and RESPES spectra provide reference spectra for the study of europium salts and their derivatives.

Photoelectron diffraction for probing valency and magnetism of 4f -based materials: A view on valence-fluctuating EuIr2Si2

“…In spite of carrying out measurements at the 4d → 4 f resonance, we consider only the direct photoexcitation channel and ignore the possible influence of the Auger decay channel on the angular distribution of photoelectrons. The latter assumption can be justified by the fact that the observed final state spectral features are equivalent to those that would result from a direct PE process [26,27]. For Eu 2+ ions, we have checked that the spectral shape of their relatively narrow 4 f multiplet at the resonance maximum is similar to the off-resonance case that was also observed in the previous studies of Tb [28].…”

Electrospun Poly(acrylic acid)/Silica Hydrogel Nanofibers Scaffold for Highly Efficient Adsorption of Lanthanide Ions and Its Photoluminescence Performance

“…The typical wide-scan XPS spectra of the virgin and Ln 3+ -loaded PAA-S HNFs were shown in Figure 8A−D. It could be clearly observed that La 3d, 26 Eu 4d, 64 and Tb 4d 65 orbital were detected at the characteristic binding energy of 838.4, 137.4, and 154.1 eV, respectively, which confirmed the adsorption of Ln 3+ on PAA-S HNFs (see details in the Supporting Information, section S6). Figure 8E−H depict the high-resolution scan of the O 1s core-level spectra of PAA-S HNFs before and after Ln 3+ adsorption.…”

Nonmonotonous temperature fluctuations of the orbital moment and spin-orbit coupling in multiferroic gallium ferrite thin films

“…While XAS and XMCD probe the unoccupied electronic states, photoelectron spectroscopies, which are also element and site selective, probe the occupied states and are perfectly adapted to study the electronic structure of the compounds. Resonant photoemission spectroscopy (RESPES) has for example successfully been used to quantitatively extract the amount of the various valences present in mixed valence compounds [40] and bring information onto charge transfer processes. [41] It consists in scanning the photon energy of a soft-X ray beam in the range of a specific absorption edge and measuring the valence band spectra for these scanned energies.…”

“…A complete description of the excitation and de-excitation processes occurring in this condition is depicted in the S.I. (Fig S3) [20,40]. One can briefly summarize them as follows: the absorption of an X-ray photon results in the transition of a core 2p-electron to the excited valence 3d-state (Fe 2p 6 3d n + h → (Fe 2p 5 3d n+1 )*), the relaxation and auto-ionization of the system then occurs through the emission of an Auger electron ((Fe 2p 5 3d n+1 )* → Fe 2p 6 3d n-1 + e -).…”