Investigating the structure of the Tin M45N45N45 auger spectrum using auger photoelectron coincidence spectroscopy

Auger photoelectron coincidence spectroscopy (APECS) data were collected for the M₄₅N₄₅N₄₅ Auger peak in coincidence with the 3p_3/2, 3d_3/2 and 3d_5/2 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 3d_5/2 photoelectron line (M₅N₄₅N₄₅:3d_5/2) due to the Mg Kα₃ line of the X-ray source. There was evidence of a small Coster–Kronig component in the M₄N₄₅N₄₅:3d_3/2 data and the M₄₅N₄₅N₄₅:3p_3/2 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.     

An auger electron spectroscopic investigation of the electron states of copper alloys

L₃VV Auger transitions of copper alloys show a feature due to a band-like states, the shape and intensity of which depend on the composition. The energy separation between this feature and the L₃M_4·5M_4·5 peak increases progressively with Cu concentration.     

Cusp satellite bands in the spectrum of molecule

We report measurements and a theoretical explanation of the cusp-shaped satellite bands in the blue wing of the cesium D₂ resonance line which have been observed for the first time. The bands are identified as transitions where the upper state dissociates into the 6 ²P _3/2 + 6 ² S _1/2 atomic asymptote. The experiment has been performed using a standard absorption setup, computer controlled data acquisition and computer data processing. We have shown that the peculiar shape of the difference-potential curve is solely responsible for the spectrum containing the cusp-shaped satellite bands. The appearance of these satellite bands has been discussed and explained relating the theory of satellite bands to the catastrophe theory. The shape of the line wing and of the satellite bands have been calculated using the Fourier transform technique. To ensure a more stringent comparison between the experimental and the theoretical spectrum, we have analyzed and compared the derivatives of the measured and the calculated satellite band shape. On the contrary to the customary direct comparison between the measured and the calculated absorption coefficient, the derivative clearly shows all differences and resemblances between satellite band profiles. The degree of coincidence of the experimentally observed and the theoretically calculated satellite band shape can be used as an ultimate check on the assessment of the quality of potential-energy curves involved in the formation of satellite bands. Received: 1 October 1997 / Revised: 14 January 1998 / Accepted: 24 February 1998     

On the satellite in the Auger electron spectrum

The satellite line profile in the C–VV Auger electron spectroscopy spectrum depends upon how the initial core hole state and the final multiple hole state are created. Even if the numbers of the holes in the satellite states are the same, the Auger electron spectroscopy spectral profiles of the final multiple hole states are different. The localization of the three hole satellite state is discussed.     

Observation of resonance recombination lines in electron excited auger spectra of Gd

Combined measurements of electron excited N_4,5 Auger spectra and photoelectron emission on clean and oxidized Gd lead to a distinction between Auger lines originating from 4d → continuum and 4d → 4? resonance excitations. Several Auger structures are identified as due to the direct recombination of 4d⁹4?⁸ states with the 4f and valence electrons. The shape of the most prominent Auger line for oxidized Gd agrees perfectly with the Fano profile of the 4? photoemission intensity.     

The shapes of Auger decay lines in photoelectron satellite spectra

The theory of the shapes of Auger decay lines of satellite two-hole-one particle states accompanying photoionization based on the Green's function method is developed. The lineshapes of Auger decay of satellite states [2 s 2 p ]( ^1,3 P )3 s ( ² P ), [2 s 2 p ]( ¹ P )4 s ( ² P ) and [3 s 3 p ]( ³ P )4 s ( ² P ) in valence p-photoelectron spectra of Ne and Ar atoms are calculated (hole states are indicated by square brackets throughout). It is shown that in some cases the Auger lineshapes reproduce the shape of the photoelectron satellite line, but in other cases Auger line may be narrower then the photoelectron line and may have opposite direction of asymmetry. The theoretical results are in agreement with experimental low-energy Auger spectra. Received: 25 May 1998 / Accepted: 2 October 1998     

Temperature dependence of the low energy auger spectrum of NiO(100)

The temperature dependence of the Auger electron spectrum of NiO(100) has been observed in order to assign 10 features found below 300 eV. Six features are attributed to diffraction of true secondary electrons generated within the crystal. The others are due to substrate or surface impurity Auger peaks. The difficulties of identifying impurities and diffraction features are emphasised.     

Elastic and inelastic contributions to the auger electron appearance potential spectrum of titanium

The energy distribution of electrons contributing to the L-shell Auger electron appearance potential spectrum of a polycrystalline titanium surface has been measured. The Auger electron appearance potential spectrum is obtained by differentiating the total secondary electron yield of an electron bombarded sample as a function of incident electron energy. At the threshold for scattering from a core level the secondary yield increases. Most of the electrons contributing to this increase have energies below 30 eV, and result from secondary processes following Auger recombination of the core hole. The elastic yield decreases at the threshold, however, due to opening a new channel for inelastic scattering. A comparison of the elastic yield spectrum (DAPS), the total yield spectrum (AEAPS) and the soft X-ray yield spectrum (SXAPS), shows very similar line shapes, but differences in the relative strengths of the lines.     

Many body theory of the coster-kronig satellite spectrum

It is shown that the formula used by Nyholm et al. to obtain the L₂ linewidths of the elements Ti(Z = 22) to Zn(Z = 30) from the L₃ linewidths is valid only when the L₃ linewidth is dominated by the L₃-M₄₅M₄₅ Auger decay process.     

A double ionization satellite in the tungsten Auger spectrum

The electron induced tungsten Auger spectrum exhibits a peak at 210 eV which is on the high energy side of the major Auger emissions, N_{4, 5}N_{6, 7}X (X ≡ N_{6, 7} or O_{2, 3}). The N₄N_{6, 7}V Coster-Kronig processes should occur around 210 eV but the yield curve for the 210 eV feature shows that most of the intensity arises from a process with threshold behaviour toward N₃. This process is identified as the second step in an Auger cascade: N₃ single holes decay via an N₅V state which exhibits a high probability of decaying via a particular N_{6, 7}XV three-hole state to yield electron emission at 210 eV.     

Plasma effects in the spectrum of high Balmer lines

Measurements of high Balmer lines (N_upper = 12 to 19) emitted from a hydrogen discharge of relatively low plasma density show that the spectrum may be well reproduced by a superposition of symmetric Stark profiles, which accounts for the broadening effect generated by ions and quasistatic electrons. The small deviations which were found most probably involve inelastic electron collisions connecting adjacent upper levels. Within experimental accuracy, a shift is not detectable either for odd or for even series members. This finding is inconsistent with the observations of other authors according to which odd Balmer lines are shifted to the red.     

Surface effects in the valence band XPS spectrum of copper

Comparison of valence band XPS spectra of Cu samples with theoretical density of states shows a high intensity near the upper edge of the d-band. This is a feature common for most d-band metals. However, if the difference in the density of states of the first two atomic layers with respect to the bulk is taken into account, good agreement between theory and experiment is found.     

Low-energy electron spectrum in copper oxides in the multiband p-d model

An exact diagonalization of the Hamiltonian in the p-d model of a CuO₆ cluster was used to obtain dependences on the model parameters of the lowest-energy two-hole terms: the energy difference between the 2p orbitals of planar and apical oxygen Δ(apex)=ε(2p)−ε[2p(apex)], the crystal field parameter , and the ratio of the distances between the copper atom and the apical and planar oxygen atoms d(apex)/d(pl). In the limit of large d(apex)/d(pl) and Δ_d, our model is equivalent to the three-band p-d model and, in this case, large singlet-triplet splitting Δε⩾1 eV is also observed. As the parameters decrease, a singlet-triplet crossover is observed. Two mechanisms are identified for stabilization of the triplet term ³ B _1g (0) as the ground state. It is shown that for realistic values of the parameters, reduction of the p-d model to the three-band model is limited by the low energies of the current excitations because of the presence of the lower excited ³ B _1g and ¹ A _1g cluster states. Intercluster hopping causes strong mixing of singlet and triplet states far from the G point. The results of the calculations are compared with data obtained by angle-resolved photoelectron emission in Sr₂CuO₂Cl₂. Fiz. Tverd. Tela (St. Petersburg) 40, 184–190 (February 1998)     

The range of energetic auger electrons in the electron-hole liquid in Ge

Some controversy has arisen as regards to the escape probability of Auger decay electrons from electron-hole drops. We present experimental and theoretical arguments which show that in fact most electrons do escape.