Many body satellite in the photoemission spectra of the heavy rare earths

A narrow feature is reported in the photoemission spectra of the heavy rare earths, Gd, Tb, and Dy on a variety of substrates. This feature is not expected from the initial densities of states. This feature appears to require a density of states at the Fermi energy to exist. We propose that the feature is due to a many electron shakeup process to the unoccupied 4f levels.     

On the origin of an additional feature in the photoemission spectra of the heavy rare earths

A narrow feature recently observed in photoemission spectra of heavy rare earth metals at a binding energy of 5.5–6.2 eV has been interpreted as a many-electron satellite. We question this interpretation and suggest that this feature is due to H contamination.     

Electrical resistivity of dilute heavy rare earths in Lu

The scattering of conduction electrons by the localized moments of heavy rare earth ions in Lu is investigated by analysing previously published resistivity measurements. The crystal field splitting of the 4f-levels is taken into account and satisfactory agreement obtained with experiment.     

Comment on many-body aspects of external photoemission

It is emphasized that the relation between the Laplace-transformed three-current-operator retarded commutator Green's function occurring in quadratic response theory of external photoemission, and the three-current temperature Green's function permits a standard many-body analysis of photoemission. As an example, a diagrammatic particlehole analysis yields generalized golden-rule formulae at finite temperature. Also, conserving approximations can be formally set up quite easily in the framework of the Kadanoff-Baym formalism, yielding quadratic response to the total field inside the specimen, thus limiting the volume effect.Work performed at The Aspen Center of Physics, Aspen Colorado 81611 and at Physikalisch-Technische Bundesanstalt, D-3300 Braunschweig     

Plasmon satellites in X-ray photoemission spectra

Controversy exists whether plasmon-satellite structure observed in core-level photoemission spectra arises from so-called intrinsic or extrinsic plasmo     

Paramagnon satellites in photoemission spectra of chemisorbed hydrogen

A model for the chemisorption of hydrogen on transition metals is considered taking the intrametallic exchange forcesI and the extra-atomic exchangeJ into account. The extra-atomic exchange couples the single particle states of the adatom to the particle-hole states of the metal. This leads to dynamic effects similar to those found in soft X-ray spectra of metals and in the image force dynamics of chemisorbed atoms. Such dynamic effects can be expected to be particularly large near a ferromagnetic instability of the metal. The theoretical treatment of these effects is complicated because of Kondo type divergencies. ForJ large compared to the band widthB a simplified treatment is adopted avoiding explicit consideration of the Kondo effect. The intermetallic exchange effects then can be incorporated into the calculation of the dynamic effects. A simplified and crude estimate of the exchange enhancement of the dynamic effects near a ferromagnetic instability indicates strong paramagnon satellites in the photoemission spectrum leading to a broadening of the unperturbed spectrum.     

Theory of satellites in photoemission and inverse photoemission spectra of 4 f materials

We present calculations of the relative intensities and peak separations of the f derived spectral density for the, integer valent, light rare earths. We consider both f derived photoemission and inverse photoemission spectra. In these types of experiments, the final states has either an excess or a deficiency of charge residing on the screened by the conduction electrons. If the screening interaction is This may give rise to the appearance of satellites in both photoemission and inverse photoemission spectra. However, the calculations indicate that the relative intensity of the f derived satellite in the inverse photoemission spectrum should be extremely weak, when compared to the intensity of the satellites in the photoemission experiment.     

Nuclear orientation and NMRON in rare earths

The rare-earth or lanthanoid series of elements offers a rich ground for the study of both solid-state phenomena and nuclear physics. Some systematic investigations of these elements as host materials and as impurity isotopes have been performed using the nuclear orientation methods, and more can be expected in the near future owing to recent technical developments. A review of past work in this area is given, and the outlook for future experiments is summarized.     

Surface plasmon satellites in x-ray photoemission from core states of adsorbed atoms

It is shown that the kinetic energy spectrum of electrons emitted from core levels of atoms adsorbed on metal surfaces should exhibit surface plasmon satellites. At sufficiently high energies, the satellites arise only via the so-called “intrinsic” mechanism, namely, screening of a suddenly created hole by the metal electrons. Their observation for a suitable adsorption system would thus constitute the first unequivocal evidence for the “intrinsic” effect.     

Strength of plasmon satellites in the valence band photoemission spectra of metals

The strength of the first bulk plasmon satellite in the valence band photo-emission spectra of simple metals has been calculated for the dispersionless plasmon model. It is found that due to the mobility of the final state hole in the valence band, the strength of the plasmon satellite is lowered compared to that of the core state. This conclusion is qualitatively confirmed by an independent experiment of Van Attekum and Trooster.     

The influence of oxygen on the lattice sites of rare earths in silicon

We have used conversion electron emission channeling to investigate the lattice sites of ^167mEr following implantation of the radioactive isotope ¹⁶⁷Tm into CZ Si and FZ Si at varying doses (6×10¹² – 5×10¹³ cm⁻²). In all cases isothermal annealing at 900°C caused Er to leave its preferred near-tetrahedral sites in favour of random lattice sites, but this process occurred by orders of magnitude faster in CZ Si. Furthermore, in CZ Si the incorporation of Er on random lattice sites was fastest in samples implanted with low doses of Tm+Er. We compare our experimental results to a simple numerical model which accounts for the diffusion of Er and O and the formation of Er_nO_m complexes. On the basis of this model, our experimental data indicate that only a few (probably between 1 and 2) O atoms are required in order to remove an Er atom from its tetrahedral site.     

极化条件对偶氮化合物薄膜中分子取向的影响

为探索不同的极化条件对分子取向的影响,用旋涂法制备了偶氮主客体掺杂薄膜,并用电晕极化的方法分别在不同温度和厚度条件下使分子取向,通过测量极化前后紫外-可见吸收谱,研究了平均取向因子的变化,并和二次谐波产生结果进行了比较。实验结果表明：对于厚度相同的偶氮薄膜,随着温度的升高,平均取向因子增大,但二次谐波信号强度先增大后减小;温度越接近聚合物玻璃转变温度,分子越容易取向,但温度过高,聚甲基丙烯酸甲酯变为粘滞态,部分偶氮分子容易在高温下蒸发掉,导致二次谐波信号强度降低,而平均取向因子增大;随着薄膜厚度的增大,针-板电极电场造成薄膜内部电场分布的不均匀性增加,极化效率降低,平均取向因子不断减小,二次谐波信号强度先增大后减小。     

Compressibility and sound velocity of some liquid rare earths

We report the first measurements of the sound velocity in liquid La, Ce, Pr and Yb and deduce the adiabatic and isothermal compressibilities. The temperature coefficient of the sound velocity in liquid Ce is positive, which we interpret as support for the suggestion that there is increasing delocalization of the 4f electrons in the liquid state.     

Resonant shake-up satellites in photoemission at the Ga 3p photothreshold in GaN

Photoemission spectra recorded near the Ga 3p photothreshold from GaN have been found to contain satellites of the main Ga 3d emission line. The intensity of these satellites resonate at this threshold, and are associated with a 3d⁸ state. The correlation energies and binding energies for the satellite multiplet have been measured for the satellite and related Auger transitions. The satellite multiplet contains additional constant binding energy features not observed in previous studies of other Ga compounds. The present results are compared with those for GaP and GaAs.     

稀土离子激活长余辉发光材料的最新研究进展

长余辉发光材料是一种新型储能材料。评述了基质组成和制备技术对长余辉发光材料发光特性的影响;介绍了黄绿光、蓝光和红光长余辉材料的最新研究进展和获得长余辉发光的关键因素,即结构缺陷形成的陷阱态和稀土掺杂的作用,并对长余辉发光材料今后的研究和应用做出了展望。     

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 .     

Nonradiative decay from 5d states of rare earths in crystals

Nonradiative decay from 4f^n?1 5d states was investigated for trivalent rare earths in Y₃Al₅O₁₂. The rates of both 5d→4f and 5d→5d transitions were determined from measurements of the lifetimes and intensities of 5d fluorescence from Ce³⁺ and Pr³⁺. Because of the stronger ion-lattice coupling, nonradiative decay rates for transitions involving 5d states are much faster than those between 4f states. Decay rates are dependent upon the temperature and the energy gap to the next-lower level. The temperature dependences of the 5d fluorescence lifetimes from 77 to 700°K are reported.