X-ray Spectroscopic Measurement of Photoelectron Inelastic Mean Free Paths in Molybdenum

Abstract

The electron inelastic mean free path (IMFP) of molybdenum is determined experimentally over an energy range of 1−120 eV using analysis of X-ray absorption fine structure (XAFS). This new approach enables accurate measurements of IMFPs in this energy range where direct measurements are often difficult and highly uncertain, and provides a means for studying materials inaccessible through current alternate techniques. This approach can also be used to determine localized IMFPs within complex molecular systems, enabling detailed study of surfaces and nanoenvironments. This information is important for diverse applications in physical chemistry including electron microscopy, spectroscopy, and diffraction (low-energy electron diffraction (LEED) and electron energy loss spectroscopy (EELS) in particular). Here we reveal the accuracy achievable using experimental data of high statistical precision, and critically evaluate the form of the IMFP in the asymptotic region in the low energy limit.

Theoretical and experimental developments in the determination of electron energy loss functions and inelastic mean free paths in elemental solids and binary compounds

“…Results are compared with recent high profile x-ray measurements of the inelastic mean free path in copper [7] and molybdenum [8]. Agreement with experiment is found to significantly increase below 50 eV, and be consistent with previous treatments at higher energies.…”

Full-potential theoretical investigations of electron inelastic mean free paths and extended x-ray absorption fine structure in molybdenum

“…We then apply the same approach to the optical ELF from DFT (dot-dashed blue curve), before finally including Mermin terms into our representation, as described (dashed red curve). Also shown for comparison is a recent measurement of the electron IMFP for molybdenum determined via analysis of the XAFS measurements of de Jonge et al [22]. The experimental curve represents the IMFP values best used to achieve maximum agreement between XAFS theory and experiment, with respect to the oscillatory part of the absorption spectrum.…”

Unveiling the principle descriptor for predicting the electron inelastic mean free path based on a machine learning framework

“…The electron inelastic mean free path (IMFP) [1,2], which describes the mean distance an electron travels through a solid before losing energy, is of fundamental importance to electron-based surface analysis techniques, such as scanning electron microscopy, X-ray photoelectron spectroscopy, and Auger electron spectroscopy [2][3][4][5][6][7]. With a dielectric formalism, the IMFP can be calculated by various algorithms, such as Penn algorithm [8,9], Mermin algorithm [10][11][12][13][14][15] and ex-Mermin algorithm [16].…”