High-accuracy transmission and fluorescence XAFS of zinc at 10 K, 50 K, 100 K and 150 K using the hybrid technique

Abstract

The most accurate measurements of the mass attenuation coefficient for metals at low temperature for the zinc K-edge from 9.5 keV to 11.5 keV at temperatures of 10 K, 50 K, 100 K and 150 K using the hybrid technique are reported. This is the first time transition metal X-ray absorption fine structure (XAFS) has been studied using the hybrid technique and at low temperatures. This is also the first hybrid-like experiment at the Australian Synchrotron. The measured transmission and fluorescence XAFS spectra are compared and benchmarked against each other with detailed systematic analyses. A recent method for modelling self-absorption in fluorescence has been adapted and applied to a solid sample. The XAFS spectra are analysed using eFEFFIT to provide a robust measurement of the evolution of nanostructure, including such properties as net thermal expansion and mean-square relative displacement. This work investigates crystal dynamics, nanostructural evolution and the results of using the Debye and Einstein models to determine atomic positions. Accuracies achieved, when compared with the literature, exceed those achieved by both relative and differential XAFS, and represent a state-of-the-art for future structural investigations. Bond length uncertainties are of the order of 20–40 fm.

Inversion model for extracting chemically resolved depth profiles across liquid interfaces of various configurations from XPS data: PROPHESY

“…However, the uniform light assumption does not hinder the reconstruction process as long as the spot size is comparable with or larger than the diameter of the sample. Under these conditions the model assuming uniform illumination is equivalent to the model including the beam profile (Ozon et al, 2023b). Furthermore, the source is supposed to be perfectly linearly polarized; however, this assumption depends on the quality of the source.…”

“…molecules), which is another source of uncertainty. These modeling errors can be lumped together in the multiplicative factor of the model equation ( 23) which can be estimated as a whole from raw data (Ozon et al, 2023b). Hence, the asymmetry coefficient and oscillation of the photoionization cross-section do not need to be known for practical application of the reconstruction profile.…”

“…We model the PE J(, K e ) [electron s À1 ] signal emerging from the sample and reaching the aperture of a spectrometer using the model from Ozon et al (2023b),…”

“…where () [m À2 ] is the alignment parameter (Ozon et al, 2023b), F() [photon s À1 ] is the total photon flux at frequency [s À1 ], (, K e ) [m 2 eV À1 ] is the photoionization crosssection density for a photoelectron with kinetic energy K e [eV] (Toffoli et al, 2007;Nicolas & Miron, 2012;Ohno & van Riessen, 2003) and (M) [m À3 ] is the concentration of the target orbital at the location M in the sample volume V . The attenuation of the PE signal is modeled with the exponential term.…”

“…The noise level can be determined from the spectra, e.g. using the left singular vector of the model to project the data onto (Ozon et al, 2023b). The normalized measurement operator for the mth peak and all photon energies…”