首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
We provide an answer to the question why the L3 photoelectron line of Cu metal measured in coincidence with the L3–VV (3F or 1G) Auger-electron line, does not line up with the L3 single photoelectron line. We provide also an answer to the question why the L3 coincidence photoelectron line is unshifted when the Auger-electron analyzer is moved away from the Auger-electron line. We show that it is the initial core–hole self-energy by the monopole excitation (screening) and the density of final states which play an important role in the shift and narrowing of Auger-photoelectron coincidence spectroscopy (APECS) spectral line. To explain the shifted APECS spectral line, Thurgate and Jiang (Surf. Sci. 466 (2000) L807) recently proposed the presence of two different core–hole states in the main-line state upon the L3 level ionization in Cu metal. However, their explanation appears to be incorrect.  相似文献   

2.
The coincidence L3 and M3 photoelectron spectroscopy (PES) main lines of Cu metal are calculated by a many-body theory. There is no peak-energy shift between the singles PES main line and the coincidence one. The asymmetric narrowing of the coincidence PES main line on the low kinetic energy (KE) side is very small. This is in accord with recent experimental findings. In Cu metal, the shakeup satellite intensity is small and the main-line satellite separation energy is much larger than the core–hole lifetime width. The interference via the final-state interaction is negligible. In the PES main line, the imaginary part of the self-energy by shakeup excitations, which is very small compared to the core–hole lifetime width, decreases very slowly in linear with photoelectron KE. The branching ratio of Auger decay of a single hole state then increases very slowly in linear with photoelectron KE so that the deviation of the coincidence PES main line from the singles one is very small. The 939 eV structure seen only in the coincidence L3 PES spectrum of Cu metal is attributed to the enhancement of the inelastic peak of a smaller energy loss due to electrons of a smaller average emission depth measured in coincidence with the elastic Auger peak. The structure will not be enhanced in the singles PES spectrum. The background subtraction in the coincidence spectrum cannot be the same as that in the singles one. Such consideration is necessary before we can conclude about the asymmetric narrowing on the low KE side. A unique capability of APECS by which one can determine the photoelectron KE dependent part of the imaginary part of the self-energy is pointed out.  相似文献   

3.
The M45-level photoelectron spectrum of Ag metal measured in coincidence with the M45–VV(1G) Auger-electron line is analyzed by taking into account the possibility of the M4–M5–VV Coster–Kronig (CK)-transition preceded Auger transition. We denote the atomic shells Mx(Mxy) and Nxy (x, y = 4,5) by MX(MXY) and V, respectively. The M4–M5 CK-transition rate is very small. The M45–VV Auger-electron spectra of metallic Pd and Sn measured in coincidence with the M4 (or M5)-level photoelectron line are analyzed. The M4–M5 CK-transition rates are also very small in metallic Pd and Sn. The coincidence Auger-electron line previously interpreted as the M4–M5–VV (or M4–M5V–VVV) Auger-electron line is largely due to the inelastically scattered M5-level photoelectron background beneath the M4-level photoelectron line. The APECS spectrum of Pd metal shows the first evidence of the M5V–VVV transition of the localized M5V shakeup two-hole state. The intensity ratio of the inelastically scattered Auger-electron background to the M5–VV Auger-electron main line of Ag metal measured in coincidence with the inelastically scattered M5-level photoelectron background beneath the M4-level photoemission line increases, as compared to that measured in coincidence with the M5-level photoelectron main line. This is because when the probability of the photoelectron being inelastically scattered increases, that of the Auger electron emitted by the same ionized atom, being inelastically scattered increases. In other words the photoelectrons and the Auger electrons are originated from the deeper atomic sites (longer pathlength).  相似文献   

4.
The M5 (3d5/2) photoelectron line of Ag metal was measured in coincidence with the M5–N45N45 (1G or 3F) Auger-electron line by Auger-photoelectron coincidence spectroscopy (APECS). The M5 photoelectron line of Ag metal measured in coincidence with either the 1G or the 3F Auger-electron line is unshifted, within the accuracy of the experiment. As the theory [M. Ohno, J. Electron Spectrosc. Relat. Phenom. 124 (2002) 53] predicts, the energy shift and asymmetrical narrowing of the coincidence photoelectron line compared to the singles one is much smaller than that in Cu metal.  相似文献   

5.
The valence hole created in Ni metal either by the L2-L3V Coster–Kronig (CK) transition or by the L3V shakeup/off becomes screened out prior to the L3-hole decay. We denote the atomic shell Lx (x = 2, 3) by LX. The metastable two-hole L3V state relaxes to the fully relaxed single L3-hole state before the L3-hole decays. Thus, the coincidence L2-L3(V)-VV(V) Auger-electron spectrum resembles closely the coincidence L3-VV Auger-electron spectrum. The final state of the CK transition preceded Auger transition is a two-hole state rather than a three-hole state. The four-hole satellite about 8 eV below the L3-VV main line in the singles (non-coincidence) Auger-electron spectrum is partly due to the L3VV-VVVV transition and the L2-L3VV-VVVV transition. The valence holes created either by the L2-L3VV transition or by the L3VV double shakeup/off remain localized during the L3-hole decay. The L3-hole lifetime widths of Fe, Co and Ni metals are determined from the APECS spectra. The agreement between experiment and theory (the independent-particle approximation) is poor.  相似文献   

6.
Auger photoelectron coincidence spectroscopy (APECS) data were collected for the M45N45N45 Auger peak in coincidence with the 3p3/2, 3d3/2 and 3d5/2 photoelectron lines of Tin. Model spectra were created to fit the APECS data from sets of Gaussian curves defined by Parry-Jones et al., J. Phys. C: Solid State Physics, 12 (1979) 1587. These models were then combined using information about the relative intensities of the peaks from the aforementioned paper to produce a model of the Auger peak which proved a good comparison to high resolution AES spectra. The APECS data revealed satelite structure in the M5N45N45 peak in coincidence with the 3d5/2 photoelectron line (M5N45N45:3d5/2) due to the Mg Kα3 line of the X-ray source. There was evidence of a small Coster–Kronig component in the M4N45N45:3d3/2 data and the M45N45N45:3p3/2 data showed intensity in the M4N45N45 and M5N45N45 regions also arising from Coster–Kronig processes. The contribution of the M4N45N45 plasmon was included in each of the APECS models and was reflected in the high resolution AES spectra. Slight oxidation of the surface of the sample during each 24-h period produced a 0.7 eV shift of the singles Auger peak to lower kinetic energies. The shift was not reflected in the coincidence peak which produced a spectrum of a clean surface due to the nature of the coincidence experiment.  相似文献   

7.
The valence hole created by the L2–L3 M45 Coster–Kronig (CK) transition may hop away from the ionized atomic site before the L3-hole decays. Then when the third (Auger) electron emitted by the L3-hole decay is measured in coincidence with the photoelectron emitted by the initial L2-level electron ionization, the coincidence spectrum becomes similar or identical to the singles spectrum of the secondary (Auger) electron emitted by the L3-hole decay as if it decayed as an initial single core hole. Thus the coincidence spectrum is essentially governed by the valence-hole dynamics of both the intermediate states and the final states of the L2–L3 (M45) CK-transition preceded Auger transition. In the present paper the Auger-photoelectron coincidence spectroscopy (APECS) spectra of Fe, Co, and Ni metals reported by C.P. Lund et al. (Phys. Rev. B55 (1997) 5455) are analyzed in light of the delocalization and localization of the valence hole(s) created by the CK transition or the CK-transition preceded Auger transition.  相似文献   

8.
In the M5O3 X-ray emission spectroscopy (XES) spectrum of La metal the spectral intensity ratio of the satellite to the diagram line is very large, as compared to that of the shakedown satellite to the main line in the M5 X-ray photoelectron spectroscopy (XPS) spectrum. The large spectral intensity ratio is due to the X-ray fluorescence of the shakedown satellite via the relaxation of the M5 main-line state to the shakedown satellite state on the time scale of M5–hole decay. We attribute the large line width of the M5 main-line state of La metal as compared to that of Ba metal, to the relaxation on the time scale of M5–hole decay.  相似文献   

9.
D’Addato et al. [S. D’Addato, P. Luches, R. Gotter, L. Floreano, D. Cvetko, A. Morgante, A. Newton, D. Martin, P. Unsworth, P. Weightman, Surf. Rev. Lett. 9 (2002) 709] studied the variation with Fe coverages in the relative Fe L3-M4,5M4,5 Auger electron spectroscopy (AES) spectral satellite intensity of ultrathin Fe films grown on Cu(1 0 0) by sweeping photon excitation energy through the Fe L2-level ionization threshold. They interpreted that the M4,5 hole in the L3M4,5 double-hole state created by the L2-L3M4,5 Coster–Kronig (CK) decay remains localized for longer than the L3-hole lifetime for the 0.3 and 10 ML coverages but has a lifetime comparable to the L3-hole lifetime for the 1 ML coverages. The present many-body theory shows that when the M4,5 hole created either by the CK decay or by the L3M4,5 shakeoff hops away from the ionized atomic site and becomes completely screened out prior to the L3-hole decay, the Fe L2-L3M4,5-L3-M4,5M4,5 AES main line as well as the Fe L3 M4,5 (satellite)-L3-M4,5M4,5 one, both of which are identical in line shape to the Fe L3-M4,5M4,5 one, dominate in the Fe CK preceded AES spectrum. The present analysis shows that the delocalization time of the M4,5 hole created in the 1 ML Fe/Cu(1 0 0) system by the L2-L3M4,5 CK decay is much shorter than the L3-hole lifetime so that the Fe L3-M4,5M4,5 AES spectral line shape hardly changes, except for the presence of a very weak spectator L2-L3M4,5-M4,5M4,5M4,5 AES satellite, when the photon excitation energy is swept through the Fe L2-level ionization threshold. For the 0.3 ML coverages the M4,5-hole delocalization time is still shorter than the L3-hole lifetime.  相似文献   

10.
Cu 2p, Cu 3d and O 1s electron spectra and Cu L3M4,5M4,5 Auger electron spectra from Cu, Cu2O and CuO have been studied at 25°C and at 400°C. The height of the Cu 2p satellite peaks from copper oxides was lowered when the temperature was raised. The intensity of the satellites also decreased if the sample stayed in vacuum for prolonged periods.Two commercial cuprous oxides were different with respect to the behaviour of the satellite peaks. One produced very weak satellites, while the other produced strong ones as previously reported in the literature for cuprous oxide. The colour of the oxides was slightly different, indicating that the stoichiometry was not the same.The change in satellite intensity is accompanied by changes in oxygen spectra, Cu L3M4,5 M4,5 Auger spectra and valence band spectra.It is useful to study Auger electrons in addition to the direct electron spectrum, since Auger signals can be more sensitive to surface conditions than direct electron spectra.  相似文献   

11.
The L and M XPS spectra of Cu (Z = 29) and the M and N spectra of Ag (Z = 47) are measured. The lineshift and the line-width of the L, M, and N core levels are analysed in a systematic way from the viewpoint of dynamic decay processes and fluctuations of a hole. The non-relativistic diagrammatic many-body calculations give much better agreement with the measured linewidths than the conventional methods because of a consistent treatment of correlation and localization effects.  相似文献   

12.
X-ray photoelectron spectra of the 2p levels of Co, Ni, and Cu compounds are examined concurrently with their L3M4,5M4,5 Auger spectra. A correlation is established between the presence or absence of Auger satellites with the presence or absence of photoelectron shake-up satellites for Co and Ni compounds. The correlation is less clear for cupric compounds. We propose the mechanism of Auger shake-up as a plausible interpretation for the observed behavior of these Auger satellites.  相似文献   

13.
Auger electron spectra have been recorded when oxygen is adsorbed on a Ni(111) single crystal surface. For the coverage range θ < 1, an analysis of the plot of the peak to peak height (H) of the oxygen KVV (516 eV) transition versus the total number of molecules cm2? impinging on the surface (molecular beam dosing) shows agreement with the kinetic mechanism proposed by Morgan and King [Surface Sci. 23 (1970) 259] for the adsorption of oxygen on polycrystalline nickel films. In this coverage range, no energy shifts of the nickel or oxygen Auger peaks were recorded.At coverages θ > 1 (standard dosing procedure) shifts in the valence spectra M2, 3VV (61 eV) and L3M2, 3V (782 eV) of ?2.3 eV and ?1.8eV respectively are recorded at 1.4 × 10?2 torr-sec. Up to these coverages no shift of the L3VV transition (849 eV) is observed. A chemical shift of ?2.1 eV is recorded in the L3M2, 3M2, 3 Auger transition (716 eV) at 1.4 × 10?2 torr-sec.In the coverage range θ > 1, shifts in the energy of the oxygen Auger peaks are observed. At 5.8 × 10?3 torr-sec. the KVV (516 eV) and KL1V (495.2 ± 0.3 eV) transitions show shifts of ?1.5 eV and ?(1.0 ±0.3) eV respectively. No shift up to this coverage is recorded in the KL1L1 (480.6 ± 0.3 eV) transition.  相似文献   

14.
《X射线光谱测定》2005,34(3):179-182
The energies and intensities of the various transitions corresponding to the transition scheme 2p3/2?13x?1–3x?13d3/2?1 (i.e. L3Mx–MxM4) were used to compute theoretical Lα2 satellite spectra in 13 elements in the atomic number range of 62 ≤ Z ≤ 90. The energies were calculated using available HFS data on K–LM and L–MM transition energies. The intensities of all the possible transitions were estimated by considering cross‐sections for the Auger transitions simultaneous to a hole creation and then distributing statistically the total cross‐sections for initial two‐hole states 2p3/2?13x?1 (L3Mx) amongst various allowed transitions from these initial states to 3x?13d3/2?1 (MxM4) final states. Each transition was assumed to give rise to a Gaussian line and the overall spectrum was computed as the sum of these Gaussian curves. The calculated spectra were compared with the available measured Lα satellite spectra. The peaks in the theoretical satellite spectra were identified as the experimentally reported satellites Lαs, La13, La14 and La17, which lie on the high‐energy side of the Lα2 dipole line. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

15.
The X-ray absorption spectra of the 3d and 4d transition metals have been calculated within the single-particle approximation by a new linearized augmented plane wave method. The spectra, calculated with sharp atomic and band-structure single-particle levels, have been convoluted with a Lorentzian broadening function whose width is the sum of that of the core hole and the excited electrons. Plots are shown for (i) the K-edge fine structures up to at least 100 eV above the edge for Ca, Ti, Cr, Co, Cu, and Zn, (ii) the L2, 3 white lines for Ca, Ti, Cr, Co, and Cu, (iii) the L3 white lines for Sr, Zr, Nb, Ru, Rh, and Pd, and (iv) the M2, 3 and M4,5 spectrum of Pd. Systematic features which depend on the crystal structure and the placement of the Fermi level with conduction band are briefly discussed.  相似文献   

16.
The X-ray photoelectron spectra of Co, Ni and Cu 2p levels for samples of MxMg1-xO (M = Co, Ni, Cu), CoO, NiO and CuO were compared. The binding energies of metal 2p32 levels did not change with their concentration. The shake-up satellite main peak intensity ratios and FWHM of metal 2p levels for Co2+ and Cu2+ in MgO were smaller than those for CoO and CuO. The Ni 2p32 spectrum for Ni2+ in MgO had no shoulder, unlike NiO. Results indicate that next nearest neighbor ions (metal ions) may influence the final states after photoelectron ejection.  相似文献   

17.
The energy distributions N(E) of secondary electrons emitted from GaP and InP samples bombarded with 40 keV Ar+ ions have been studied by a retarding potential method and an electronic derivation. The spectra show beyond an intensive peak developed at 2 eV, a detailed spectrum between 80 and 140 eV. The analysis of this spectrum reveales Auger electrons corresponding to L23(P) VV and L23MIV–V(Ga) V [or L23(P) NIV-V(In) V] transitions; moreover, peaks due to plasmon excitations and d band excitations can be distinguished.  相似文献   

18.
The vacancy satellite lines in the Cu LMM spectrum which originate from transitions between two hole initial states and three hole final states have been experimentally identified by changing the energy of the exciting x-rays from 1254eV to 950eV and so reducing the number of two hole initial states populated by L1L3M and L2L3M4,5 Coster-Kronig transitions relative to the number of single L3 holes.  相似文献   

19.
The total energy distribution of electrons emitted from clean Cu(100) and oxygen covered surfaces is analysed. A primary electron energy of 400 eV enabled the investigation of characteristic losses (ELS), Cu MVV Auger transitions and true secondary electrons in a single spectroscopic run. Oxygen exposure up to 108 L at elevated temperature (~400 K) results in a Cu density of states (DOS) strongly affected by O(2p) electrons. The Auger lines of Cu, atomic-like for clean surfaces, reveal DOS effects after some 107 L oxygen exposure: all MVV transitions shift down by ~2 eV in spite of a fixed M23 level; the M23VV Auger line splitting is vanishing due to a broadened valence band maximum allowing the deexcitation of the final two-hole state of intraatomic transitions. Heating the oxygen covered crystal to 820 K is accompanied by the removal of much surface oxygen and an electronic state resembling an earlier oxidation state without DOS effects in the Cu Auger spectrum.  相似文献   

20.
The many-body effect in the L3-M23M23 Auger-electron spectroscopy (AES) spectrum of metallic Zn is discussed. The lifetime width and residual relaxation energy shift of the two M23-hole state are governed by the (super) Coster-Kronig (sCK) transitions of two M23-hole state. The residual relaxation energy shift and decay width of the two M23-hole state are calculated in an average configuration by an ab initio atomic many-body theory. The agreement with experiment is good. To elucidate the many-body effect in the two-hole states, it is necessary to be able to discriminate individual components of the multiplet-split AES spectrum. We discuss how to discriminate individual components of the multiplet-split L3-M23M23 AES spectrum of metallic Zn by angle-resolved Auger-photoelectron coincidence spectroscopy (AR-APECS) in order to determine accurately their line shapes, multiplet splitting energies, and spin states (singlet etc.).  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号