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.     

The influence of the matrix element on angle-resolved photoemission spectra of insulating cuprates

Microscopic model calculations of the matrix element of a dipole moment are carried out in terms of the cluster model. This matrix element determines the transition probability of electron photoemission from a one-electron orbital with symmetry γμ to a free state. The effect of the matrix element on the angular and polarization dependences in the angle-resolved photoemission spectra of insulating cuprates, such as Sr₂CuO₂Cl₂ and Ca₂CuO₂Cl₂, is analyzed under the assumption of a well-isolated ground state of the two-hole CuO ₄ ^5? cluster, namely, the Zhang-Rice singlet. The angular k dependence of the matrix element gives rise to effects, such as the residual Fermi surface, which are typical of metallic systems. An analysis of the experimental data reveals the presence of another electronic state (with different symmetry) in the vicinity of the Zhang-Rice singlet.     

Splitting of core-level lines in photoemission spectra of transition metal compounds

The multiplet structure of core-electron binding energies in Cr 3s, Cr 3p and Cr 2p levels of CrCl₃ and CrBr₃ compounds has been investigated by X-ray photoelectron spectroscopy. The Cr 3s levels show a doublet splitting (about 4.3?eV) for the main emission in both halides. Satellites features are observed in Cr 3s, 3p and 2p levels at higher binding energies. In the Cr 3s spectrum, the main emission is assigned to unscreened intra-atomic multiplet splittings with correlation-induced satellites. The Cr 3p and 2p spectra can be better explained by the multiplet splitting arising from the interaction between valence band 3d electrons and core p holes in the crystal field. Final state screening (charge-transfer) effects do not play a major role in Cr 3s main emission nor do they affect the satellite structures in a relevant way. This explains why the Cr 3s exchange splitting in chromium halides is proportional to the local magnetic moment.     

Franck-condon-broadened angle-resolved photoemission spectra predicted in LaMnO3

The sudden photohole of least energy created in the photoemission process is a vibrationally excited state of a small polaron. Therefore the photoemission spectrum in LaMnO3 is predicted to have multiple Franck-Condon vibrational sidebands. This generates an intrinsic line broadening approximately 0.5 eV. The photoemission spectral function has two peaks whose central energies disperse with bandwidth approximately 1.2 eV. Signatures of these phenomena are predicted to appear in angle-resolved photoemission spectra.     

Calculation of the structure of the 4s band for Ni3Mn and Ni3Fe ordered alloys

Perturbation theory has been applied to the structure of the 4s band of Ni₃Mn and Ni₃Fe ordered alloys; the Fermi surfaces have been constructed for these alloys in the one-wave approximation, and the electron state densities and electron energy change on ordering have been calculated. It is found that the contribution of the 4s electrons to the ordering energy is much less than that of the 3d electrons.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 102–106, July, 1972.     

Resonant photoemission at the 3s threshold of Ni

A resonant enhancement of valence band photoemission features in Ni near the 3s threshold is presented. The emission behavior with photon energy of the Ni-3d band is characteristic of a Fano-type resonance. In addition to the main 3d-band emission and 6eV binding energy satellite, a weak satellite is observed at 7.2eV below the Fermi level with photon energies in the vicinity of the 3s threshold.     

Surface versus bulk Coulomb correlations in photoemission spectra of SrVO3 and CaVO3

Recent photoemission spectra of the perovskite series CaxSr1-xVO3 revealed strong modifications associated with surface contributions. To study the effect of Coulomb correlations in the bulk and at the surface, the quasiparticle spectra are evaluated using the dynamical mean field theory. It is shown that as a result of the reduced coordination number of surface atoms correlation effects are stronger at the surface than in the bulk, in agreement with experiment.     

X-ray photoemission spectra of valence electrons in V3X and Nb3X compounds

The X-ray photoemission spectra (XPS) of the A15 type compounds V₃Au, Nb₃Os, Nb₃Ir, Nb₃Pt and Nb₃Au have been studied. The inner level binding energies of the different components and the valence electron distribution were measured. The Nb4d and the X5d energy bands of the Nb₃X compounds appear to be more and more separate with increasing atomic number of the X component. The comparison between the results from X-ray emission spectroscopy (XES) and X-ray photoelectron spectroscopy (XPS) of corresponding V₃X and Nb₃X compounds points out the similarity of their electronic structures.     

Cooper minima in the photoemission spectra of solids

Variations of the photoionization cross section of valence states as a function of interatomic distance are studied by means of atomic and solid-state density functional approaches and compared with photoemission data. In contrast to the free atom case, a series of Cooper minima is found for 4d, 5d, and 5f states in Pd, Ag, Au, and U metals. The discovered fundamental phenomenon is of high importance for the correct interpretation of photoemission data.     

Effects of short-range magnetic order on photoemission and inverse photoemission spectra in iron

The dependenc of spin-resolved photoemission and inverse photoemission spectra on short-range magnetic order below and aboveT _c is investigated within a bulk interband transition model. The spectra are calculated in a 2000-atom cluster of bcc-Fe with local exchange field configurations, which are random subject to an assumed spin-correlation function. The model continuously bridges the gap between the disordered-local-moment picture (no short-range order) and a local-band picture (massive short-range order). Special emphasis is given to the analysis of factors like group velocity and the symmetry of the wave function by investigating special points in the Brillouin zone. Comparison with experimental data reveals a short-range order of at least 4 Å (corresponding to a nearest-neighbour correlation of about 0.4) nearT _c .     

Energy-gain satellite structure in the C(1s) x-ray photoemission spectra of organic macromolecules

Satellite peaks on the high kinetic energy side of the C(1s) photoemission line of several aromatic organic macromolecules are observed. Subsidary experiments indicate that these peaks correspond to the absorption of quanta of energy from the exciton population created at the surfaces of thin film samples by the inelastic scattering of photoelectrons not collected under the C(1s) peak. This phenomenon would then be an approximate electronic analogue to photon-vibron hot bands in the Frank-Condon effect in the optical spectroscopy of molecules.     

类铝离子Cr+11、Mn+12和Fe+13能级3s23p-3s23d跃迁参数计算

用多组态Dirac-Fock(MCDF)方法,对类铝离子Cr⁺¹¹、Mn⁺¹²和Fe⁺¹³能级3s²3p-3s²3d跃迁进行了理论计算。研究了组态相互作用对类铝离子跃迁的影响,得到了相应的跃迁能量、跃迁波长和振子强度。与已有的实验数据进行了比较,相应的计算结果符合较好。     

Polarization effects in the photoemission spectra of trigonal tellurium

Strong and unequivocal polarization effects are observed on the photoemission spectra of vacuum-cleaved, $\text{(10}\text{1}\text{0)}$ Tellurium. Calculations of the energy distribution curves of the photoelectrons have been performed based on pseudopotential band structure and wave functions. The results correlate with the observations and allow for the interpretation of the measured EDC in terms of bulk properties and surface effects.     

Electronegativity and crystal field splittings in rare earth compounds

Crystal field studies in a variety of 4f-and some 5f electron-systems reveal a correlation between crystal field splittings, i.e. sign and charge strength of simple ligands and their electronegativities. Deviations occur in several very dilute f.c.c. noble metals, as well as noble metal compounds presumably due to the d-electron contribution and perhaps ill-defined valence states, in particular in transition metal compounds.