Spin polarized energy-resolved photoemission from Ni(111) using synchrotron radiation

We report on the first energy-resolved (retarding field mode) spin polarized photoemission measurement from a Ni(111) single crystal using synchrotron radiation from the ACO storage ring at LURE(ORSAY) It is shown that exchange effects can be detected for electron states well below the Fermi energy and that spin polarized, constant-initial-state spectroscopy of ferromagnets using synchrotron radiation is feasible.     

Double-step excitation in spin polarized photoemission from NEA GaAs(100)

Spin polarized photoelectrons emitted from a NEA GaAs(100)-photocathode, which is activated in a special way with oxygen and cesium, can have a broad energy distribution with a maximum energy higher than expected for an one-photon excitation process within the bulk from the valence band edge into the conduction band. Also the shape of the energy distribution curves of the emitted electrons depends on the intensity of the incident light. This double-step excitation process is observed for aged and/or oxidized activation layers, especially for surfaces with a strongly developed, negative electron affinity. To give an explanation of these effects, it is suggested that excited conduction electrons absorb a further photon within the band bending region. This second photoemission excitation step seems to be enhanced by an interfacial barrier between the band bending region and the cesium-oxygen activation layer as well as by the existence of two-dimensional surface subbands.     

Spin polarized Auger spectroscopy from Fe(100)

The spin polarization of the M₂₃M₄₅M₄₅ Auger line of Fe(100) is shown to reveal two gain satellites at 4 and 17 eV, respectively, above the M₂₃ threshold. The lower one was previously identified as autoionization emission, whereas the higher one is a newly observed feature with a strikingly large positive spin polarization of > 80%. The spin polarization of the M₁M₄₅M₄₅ line is also reported.     

Plasmon loss structure in synchrotron radiation photoemission from Mg films

Synchrotron radiation excitation has been used to vary the kinetic energy of electrons photoemitted from the 2p core level of polycrystalline magnesium films and the energy-dependence of the accompanying plasmon loss structure has been observed. Difficulties associated with background subtraction are discussed, and it is shown that the method of background subtraction profoundly affects the conclusions drawn from such an experiment on the relative importance of plasmon and single particle excitation mechanisms for electron scattering. Very thin films of Mg have also been studied in an attempt to separate the intrinsic and extrinsic modes of plasmon creation. Although the plasmon loss structure is dependent on film thickness implying a considerable contribution from extrinsic processes, we are not able to observe plasmons excited in the thin film by electrons originating in the substrate core level. The implications of these results are discussed and further experiments suggested.     

Study of W bulk bands with normal (001) photoemission using synchrotron radiation

Photoemission normal to the (001) face of W was measured using polarized synchrotron radiation at normal incidence for 10 eV ?hv? 30 eV. All the major features observed agree very well with the predictions of three-dimensional, bulk band calculations for direct transitions along the line Δ, even for final energies well above E_F. No surface resonances were observed with s-polarized radiation.     

Resonant photoemission from SmS(100)

A strong, sharp resonance enhancement of 4f photoemission has been observed on SmS(100) surfaces for photon energies in the region of the 4d-4f transitions at about 126 eV. The discrete final state reached via the excitation hν+4d¹⁰4f⁶→4d⁹4f⁷ autoionizes primarely via a super Coster-Kronig transition of the type 4d⁹4f⁷→4d¹⁰4f⁵ + unbound electron. Other decay channels, e.g, Sm 5p emission, as well as a surface induced binding energy shift in the Sm³⁺ final state are identified and discussed.     

Spin polarized photoemission from the Fe 3s core levels

The origin of the core level splitting in the Fe 3s spectra has been investigated by spin resolved photoemission. The two Fe 3s spectral features, separated by 4.4 eV, are found to be characterized by large and opposite spin polarization. This observation proves that the exchange interaction is the main cause of the Fe 3s splitting.     

Fe/ZnO(0001)界面的同步辐射光电子能谱研究

利用同步辐射光电子能谱研究了Fe/ZnO生长模式、界面化学反应和电子结构.结果表明，Fe在ZnO(0001)表面以类SK模式生长(单层加岛状生长).当沉积约2?的Fe后，生长模式开始从二维层状生长转变成混合模式生长.界面价带谱和Fe3p芯能级谱的分析表明，在低覆盖度下，约有一个原子层(约1.5?)的Fe被ZnO(0001)面的外层O原子氧化，随着沉积厚度的增加，金属态Fe的信号逐渐增强.当吸附了5.1?的Fe时，出现了较强的金属Fe的Fermi边，说明出现了Fe的金属态.此外，在Fe原子吸附过程中，样品功函数在Fe厚度为0.2?时达到最小值4.5eV，偶极层形成后逐渐稳定在4.9eV.     

Azimuthal asymmetry in processes of nonlinear QED for linearly polarized photon

Cross sections of nonlinear QED processes (photon-photon scattering, photon splitting in a Coulomb field, and Delbrück scattering) are considered for linearly polarized initial photon. The cross sections have sizeable azimuthal asymmetry.     

Angle-resolved photoemission from CO on Fe(110)

We report normal emission, angle-resolved photoemission measurements of the system p (1×2)Co-Fe(110) at several photon energies. The lower bind-energy feature, commonly attributed to emission from both the 1π and 5σ molecular orbitals of CO, shifts from 6.9 to 8.1 eV (relative to the Fermi energy) as the photon energy is increased from 21 to 30 eV. We attribute this dispersion to a large variation in cross section for photoionization of the 1π- and 5σ-derived orbitals and use symmetry selection rules to Identify the 6.9 eV component as the 1π and the 8.1 eV component as the 5σ. This ordering is reversed from the gas phase ordering.