The processes of multiple scattering of a secondary electron from a local atomic structure and their contributions to the EELFS spectra have been considered. For the M EELFS spectra of 3 d metals (i.e., the EELFS spectra behind the M edges of energy loss), the contributions of the processes provided by multiple processes of electron-impact excitation of 3 d valence electrons have been analyzed.

The electron energy loss extended fine structure (EELFS) spectra were obtained from the pure nickel surface (M (2,3) EELFS) of a stoichiometric NiO film (NiM (2,3) and OK EELFS spectra) and the "nonhomogeneous" oxide film on the surface of nickel Ni-O (NiM (2,3) and OK EELFS spectra). The amplitudes and intensities of electron transitions for the core levels of atoms were calculated with regard for the multiplicity of electron impact excitation of the corresponding core levels of atoms. The corresponding normalized oscillating terms were isolated using the results of calculations based on the experimental EELFS spectra. Agreement between the experimental and calculated (on Ni and NiO test objects) data showed that the theoretical approaches used and the calculated data for describing the EELFS spectra are good approximations. Using the results of calculations and the parameters of secondary electron elastic scattering (FEEF-8 data) we obtained the atomic pair correlation functions from the experimental normalized oscillating parts of the EELFS spectra by Tikhonov's regularization method.

The problem of multipolarity of the atom core level ionization by electron impact in extended energy loss fine structure (EELFS) spectroscopy is studied. The intensities and amplitudes of electron transitions have been calculated in the OPW approximation. The experimental K EELFS spectra of Al, Si and L EELFS spectra of Fe, Co have been obtained. Corresponding calculations have been carried out in the monopole and dipole approximations. A comparison of theoretical and experimental spectra have been made. It is shown that a good agreement between the theoretical and experimental results points to the need for taking account of multipolarity of the electron transition processes in EELFS calculations.

The surfaces of crystalline samples of 3d-metals (Mn, Fe, Co, Ni, and Cu) and their stoichiometric oxides have been studied by Auger spectroscopy. A correlation between the change in the LVV (L-inner level-valence-valence electron transition) Auger intensities and the change of the squares of the corresponding atomic-magnetic moments has been observed. This is because of the complicated nature of the Auger process. That is, the Auger electron emission is a result of the inner atomic level excitation by electron impact and Auger annihilation of the inner-level hole. Therefore, the Auger process has been considered a second-order process, and spin polarization of the valence states has been taken into account for the LMM (L-inner level-M-inner level-M-inner level electron transition) Auger spectra of 3d-metals.

Secondary electron spectra of Fe, Ni, Cu pure surfaces and corresponding oscillating signals were obtained. The atomic pair correlation function was estimated by solving the inverse problem using the Tikhonov regularization method. The results obtained and the application of the secondary electron fine structure method for local atomic structure analysis are discussed.

The pseudopotential model is used for the evaluation of the core level ionisation intensities (by the electron impact). The central atom effective phase shift is calculated for K EELFS spectra in this framework. The Si K EELFS spectra were calculated and compared with the experimental data. The comparison of experimental and calculated results is performed on the base of the electron dispersion law which takes into account electron-plasmon interaction.

In this paper we report the history of the electron Extended Energy Loss Fine Structure (EELFS) spectroscopy in brief, quite a novel technique for studying local atomic structure of materials. Fine structures above ionization edges studied by EELFS technique are similar to those measured in X-ray absorption spectra and have an extension of several hundreds eV above a threshold and a period of about tens eV. The analysis of these extended structures gives local structural information (partial interatomic distances, coordination numbers, backscattering amplitudes, phase shifts, etc.). EELFS technique has been proved to be a powerful tool for local structure investigations of clean surfaces and chemisorbed species. Numerous papers have been published to demonstrate the applicability of EELFS technique in the determination of the structure of different compounds and different metals deposited on clean surfaces. Application of EELFS technique provides great progress to materials science in regard to the atomic structure study. In this paper we give some examples of studying different materials by EELFS both in the transmission and reflection mode using the results obtained by different authors including ours.

A spectrum of the secondary electron extended fine structure (SEFS) above the M2,3VV Auger line of a Cu (111) single crystal has been obtained. The solution of an inverse problem has been calculated for the experimental SEFS spectrum and the pair correlation function (PCF) has been obtained by Tikhonov's regularization method. Parameters for the nearest atomic environment, namely, the bond length and the asymmetry parameter of the PCF first peak, have been determined. A comparison of results obtained with available data and those obtained by other methods allows us to conclude that this setting of the inverse problem and the integral operator kernel parameters selected can be used for the experimental determination of PCF for both single-component and more complicated matter.

Extended energy loss fine structures spectra (EELFS) above the M2,3 ionisation edge of a Cu(111) single crystal have been obtained at primary electron energies of 1500 and 560eV, corresponding to a studied layer depth of ∼15 and ∼8Å. For experimental EELFS spectra the solution of an inverse problem has been performed and pair correlation functions (PCFs) have been obtained by Tikhonov's regularisation method with allowance made for normalisation of the atomic intensity of ionisation losses. Parameters of the nearest atomic environment, namely, the bond length, the co-ordination number, the Debye–Waller factor and the parameter of asymmetry of the first peak of the pair correlation function, have been determined for both large (∼15Å) and small (∼8Å) depths of the studied layer.

The extended fine structure (FS) was obtained above MVV and LVV Auger transitions in Fe and Ni. The temperature behavior of FS above MVV Auger transition was investigated in the range of 300–800 K. It was shown that the supplementary peak appears in Fe spectra and vanishes in Ni spectra with increase in temperature. A new mechanism of the FS formation was used which includes both the first order process (the secondary electron emission from a core level) and the second order process proceeding through the intermediate state. The appropriate theory was developed and on its basis the quantitative interpretation of the anomalous temperature behavior of MVV FS and the type of the oscillation above the LVV Auger transition was given for Fe and Ni.

The oscillation in the secondary spectra (extended fine structure) contains the surface (~ 3–5 atomic layers) local atomic structure information in the form of the radial distribution function. For the latter determination from the 3d metals secondary electron extended fine structure the inverse problem has been setting. On this basis the mathematical treatment of the experimental copper spectra was performed. The separation of the first three peaks and their approximately right positions in the calculation result was obtained.

It has been shown that the contribution from the intermediate excited state of the system at the moment of the Auger transition causes the extended fine structure of secondary electron spectra, which extends several hundred electron volts above the main Auger line. Two types of oscillations are observed in the spectrum, due to the electron scattering on the atomic environment in the intermediate and final states. The comparison between Cu and Ni theoretical and experimental spectra was carried out.