This lecture introduces a simplified single-pole approximation (SSPA) for calculating the inelastic mean free path (IMFP) of electrons in surface electron spectroscopy. The SSPA is a further simplification of Penn’s single-pole approximation (SPA), in which the dispersion relation is expressed in a quadratic form with a single adjustable parameter. By optimizing this parameter, the accuracy of the IMFP can be improved while maintaining computational simplicity. IMFPs calculated using the SSPA were evaluated for 41 elemental solids and compared with results from the full Penn algorithm (FPA) and the original SPA. The SSPA demonstrated good agreement with the FPA across the 300 eV to 10 keV energy range. In particular, the optimized SSPA, employing a dispersion coefficient of 0.4167, yielded relative deviations within 3% of the FPA results, confirming its practical utility. This lecture also provides a detailed explanation of the Mathematica implementation of the SSPA-based IMFP calculation, including procedures for dispersion parameter optimization. These descriptions aim to ensure reproducibility and facilitate further applications in surface electron spectroscopy.

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LaB₆ has a low work function and is used as a thermionic cathode, but further work function reduction and maintenance of the low work function state are needed. In this study, graphene and hexagonal boron nitride (hBN) were coated on the surface of LaB₆ by a wet transfer method, and the work function change was investigated by photoelectron emission microscopy and synchrotron radiation XPS. The DFT calculations also showed a decrease in the work function. On the other hand, the work function increased for graphene. This is due to the dipole effect at the interface, where the outward dipole forms in hBN and the work function decreases, while in graphene the work function increases due to the inward dipole.

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This article is about the lecture given as an introduction to the theme lectures "Probing depth of XAFS" at 63rd SASJ meeting. In the first half, the principle of the basic measurement modes in X-ray absorption fine structure (XAFS) spectroscopy, i.e., transmission, fluorescence yield, and electron yield, are described. Especially, the thickness effect (self-absorption effect) in fluorescence yield mode is explained in detail by use of a simple mathematical model. In the second half, the probing depths of partial fluorescence yield and Auger electron yield are estimated by similar models, and the previously reported values of probing depth of total electron yield were compiled into a graph.

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We have involved in analyzing the surface chemical state of contact lenses by analysis techniques using quantum beams, such as synchrotron radiation and neutron sources. In this process, we have realized the importance of clarifying the analysis depth of each of these analysis techniques and the effectiveness of making use of the difference in the analysis depth among these techniques in the surface analysis of contact lenses. In this article, we report about our research on the analysis depth of the hard X-ray photoelectron spectroscopy (HAXPES) for the contact lens materials, and about the analysis of contact lens surfaces by X-ray absorption fine structure (XAFS) spectroscopy using surface-sensitive conversion electron yield (CEY) and bulk-sensitive partial fluorescence yield (PFY) modes, which have been performed at several experimental facilities.

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