Auger Satellite Lines Research Articles

PCI effects and the gradual formation of Rydberg series due to photoelectron recapture, in the Auger satellite lines upon Xe 4d−15/2 photoionization

The Xe (N5O2,3O2,3) Auger electron spectra originating from 4d−15/2 inner-shell photoionization were measured, with photon energy tuned close to the ionization threshold. As the photon energy approaches the threshold from above the 4d−15/2 photoionization threshold, Rydberg series structures are formed within the Auger electron peak by the recapture of the photoelectron into high-lying ion orbitals. They emerge in the tail on the higher energy side of the post–collision interaction (PCI) profile of the Auger electron. Discrete Rydberg peaks replace the continuous PCI tail and gradually form a series with intensity distribution emulating the intensity profile of the continuous tail. Structures due to the Xe+5p4(1S0, 1D2, 3P2,1,0) ml series were observed and assigned.

Chemical effects on F KLL Auger spectra in fluorides

Considerable chemical effects have been found on the satellite structures of F KLL Auger spectra in fluorides recently, which could be important for surface chemical identification and could provide information on the origin and the atomic or molecular character of particular Auger satellite lines. In the case of alkali fluorides unassigned satellites were found and interpreted on the basis of a new concept, resonant orbital rearrangement. In the present work we study the structure of the Auger satellites induced from rutile-type fluorides. F KLL Auger spectra were excited by Al Kα and Cu Lα x-rays from polycrystalline powder samples of MgF2, ZnF2, NiF2, and CoF2 and measured by a high luminosity electron spectrometer. Excitation by Cu Lα increased the peak to background ratio in the spectra significantly. Similar to the alkali fluorides, a satellite has been found in the high kinetic energy part of the measured F KLL spectra. From the satellite intensities the fluorescence yield for the doubly ionized states in MgF2 has been determined. An inverse proportionality has been found between the satellite/diagram x ray and the corresponding Auger intensity ratios, while the latter ratios have been found to be proportional to the linewidth of the new Auger satellites. These observations indicate the resonant nature of the Auger transition identified. For determining the energy difference between the molecular orbitals in resonance, discrete variational Xα cluster molecular orbital calculations have been performed and the experimental results have been interpreted on the basis of the resonant orbital rearrangement model. Multiplet structure calculations for K6F clusters indicate that multiplet splitting cannot explain the origin of the above satellite peak in the F KLL spectrum of solid KF.

Solid-state effects on the satellite structure of KLL Auger spectra in Cu and Ni

Discrete variational (DV) Xα cluster molecular orbital calculations were performed for describing the energy of the Cu and Ni KLL Auger satellite lines reported recently. The results of the molecular orbital cluster approximation are in good agreement with the experimental data, thus confirming the validity of the spectator vacancy model assumed earlier. It is also shown that, in the case of Ni, accounting for screening effects of free electrons in the metal is necessary and results in good agreement with the satellite–KL2L3(1D2) energy separation determined experimentally. Copyright © 2000 John Wiley & Sons, Ltd.

New trends in the study of alignment and orientation in ion-atom collisions

An overview of recent experimental and theoretical studies of the alignment of inner shell vacancies produced in fast ion-atom collisions is given. Information about impact parameter dependence of the alignment as obtained from coincidence measurements and from studies of the anisotropy of the X-ray and Auger satellite lines is discussed. The contribution of various mechanisms of inner-shell vacancy production (direct Coulomb ionization, electron capture, shake-off) is discussed. Recent experiments on the alignment in electron capture processes are analyzed. Finally, new types of experiments, namely, measurements of the alignment and orientation of a vacancy produced by proton impact ionization of laser excited and aligned atoms, is theoretically analyzed.

KL 2,3 ionization in neon by electron impact in the range 1.5–50 keV: cross sections and alignment

We have measured the ratio of cross sections σ(KL2,3)/σ(K) for neon for electron impact in the energy range ofE0=1.5 ... 50 keV via the intensity ofKL2,3−LLL2,3 Auger satellite lines relative to the intensity ofKL1L2,3 (3P) diagram line. The experimental ratio decreases over the full range of energyE0 which is contrary to an earlier result by Carlson et al. We have also measured the alignment ofKL2,31P and3P states via the angular distribution of Auger satellite intensity for the energy rangeE0=1.5 ... 4 keV, within experimental error we have found a zero alignment. The totalK Auger spectrum, measured forE0=40 keV and at the magic angle of emission ϑ=54.7°, has been decomposed into its components by using appropriate line shapes distorted by postcollision interaction. Finally, we discussed whether the lines observed at the high-energy side ofKL2,3−LLL2,3 Auger satellite lines can be interpreted as structures caused by an angular momentum exchange in the postcollision interaction predicted by Niehaus and Zwakhals.

An Auger and X-ray photoelectron spectroscopic study of sodium metal and sodium oxide

Photoelectron and Auger electron measurements have been made on polycrystalline films of sodium metal evaporated in ultra high vacuum, and on Na 2O produced by in-situ oxidation by dry oxygen. Most of the spectra were recorded using Mg Kα (1254 eV) radiation but excitation by 5 keV electrons or monochromatized Al Kα (1487 eV) X-rays was used for specific purposes. Core and valence electron binding energies, photoionization cross-sections relative to Na 1s, KLL and KLV Auger energies and transition probabilities are reported. Energy losses in the metal and oxide are discussed and the relative intensities of surface and bulk plasmon losses have been used to calculate mean electron escape depths in the metal. When corrections were made for experimental geometry, escape depths of 10 Å at 180 eV and 31 Å at 1200 eV were obtained. An escape depth of 23 Å at 980 eV was obtained by Na 1s-Na K-Auger intensity correlation and this is consistent with the plasmon data. Data on Auger satellite lines are presented and, in particular, evidence has been obtained which indicates that a high energy satellite should not be attributed to a plasmon gain mechanism. Valence band influences on the KLV Auger spectra are discussed with reference to the XPS spectrum and other sources of valence band information. Unexpected structure was found in the KLV spectra of the metal which, pending thorough interpretation, offsets the sensitivity and resolution advantages which these spectra otherwise offer for valence band studies.

Auger decay of neon following energetic ion bombardment

A high-resolution double-focusing electrostatic electron analyzer has been used to resolve Ne Auger electrons produced by 0.15-6.0-MeV ${\mathrm{H}}^{+}$, 1.0-MeV ${\mathrm{He}}^{+}$, and 33-MeV ${0}^{5+}$ bombardment. Individual $K$-Auger satellite lines stemming from the decay of multiply ionized neon have been observed. The energies, relative intensities, and production probabilities of these satellite lines were measured as a function of the projectile $Z$ and as a function of proton bombarding energy. Tentative identifications for all observed lines were made by comparison with calculated Auger satellite transition energies. The reliability of the Hartree-Fock calculations used was demonstrated by comparison with ${e}^{\ensuremath{-}}+\mathrm{Ne}$ data and by comparing calculated x-ray transition energies for multiply ionized neon to recent measurements of O + Ne x-ray lines. A rough estimate of the probability of single- and double-$2s$ orbital vacancy production as a function of $L$-shell defect was obtained. With proton bombardment, the satellite-production probability ${Q}_{s}$ was observed to decrease smoothly with increasing proton energy. The observation that ${Q}_{s}$ for 6-MeV proton bombardment was approximately equal to that obtained with equal-velocity electrons is believed to imply that electron shakeoff is the dominant $L$-shell ionization mechanism for high-energy proton bombardment.

A high resolution study of Ar LMM Auger electrons produced by ion bombardment

Ar LMM Auger electron lines produced by H+, He+, O4+, and O5+ bombardment are measured with high instrumental resolution (0.02% FWHM). Individual heavy ion induced Auger satellite lines are resolved. Two strong lines are observed at 221 and 223 eV in the oxygen induced spectra. The ratio of satellite to normal line production is given for each projectile.

High resolution Ne KLL Auger spectra produced by H+ and He+ bombardment

Abstract Ne KLL Auger satellite lines are measured with an energy resolution of 0.02% FWHM. The relative intensities of initial 2p vacancy satellite lines are observed to be four times larger with He + than with H + bombardment. The He + beam also produces new satellite lines which are assigned to double initial 2p vacancies.

K-Shell Ionization ofN2and CH4by 50- to 600-keVH+,D+,H2+, andHe+Impact

A crossed-beam scattering chamber was used to measure absolute cross sections for Auger-electron ejection by 50- to 600-keV ${\mathrm{H}}^{+}$, ${\mathrm{D}}^{+}$, $\mathrm{H}_{2}^{}{}_{}{}^{+}$, and ${\mathrm{He}}^{+}$ impact on ${\mathrm{N}}_{2}$ and C${\mathrm{H}}_{4}$. Auger electrons emitted at 150\ifmmode^\circ\else\textdegree\fi{} with respect to the incident ions were analyzed by an electrostatic parallel-plate spectrometer with a resolution of 1.1% full width at half-maximum. The intensities of Auger-satellite lines were determined to study the simultaneous inner- and outer-shell ionization of ${\mathrm{N}}_{2}$ by $\mathrm{H}_{2}^{}{}_{}{}^{+}$ and ${\mathrm{He}}^{+}$ at different energies. The Auger spectra were integrated with respect to energy and angle of ejection of the electrons to obtain total cross sections for $K$-shell ionization. The experimental results are compared with existing theories. Good agreement is obtained for ${\mathrm{H}}^{+}$, ${\mathrm{D}}^{+}$, and $\mathrm{H}_{2}^{}{}_{}{}^{+}$, but discrepancies appear for ${\mathrm{He}}^{+}$ impact at low energies. Ratios of Auger-electron and x-ray production cross sections are determined to study the effect of multiple ionization on the fluorescence yield.