Engineering topics

Tobin, J. G. (ORCID:0000000322943301)

Publications and source records attributed to Tobin, J. G. (ORCID:0000000322943301).

3 records

DOE OSTI2025

The importance of electron scattering in the analysis of actinide X-ray spectroscopy

Abstract Manifestations of electron scattering in X-ray spectroscopy have been evident for decades. Here, it will be shown that the proper interpretation of variants of X-ray Absorption Spectroscopy (XAS) of actinide materials must include an accurate treatment of features caused by electron scattering, i.e., EXAFS or Extended X-ray Absorption Fine Structure. These EXAFS features can be of such low energy that they are within ten to twenty electron volts of the Unoccupied Density of States (UDOS), immediately above the Fermi Energy or Band Gap. The adaption of simple models using the FEFF simulation program will be presented, including the demonstration of the robust nature of the results from different models. Graphical abstract

Tobin, J. G. (ORCID:0000000322943301)↗

DOE OSTI2021

The Limitations of 5f Delocalization and Dispersion

Delocalization in the 5f states of the actinides is an important phenomenon, but poorly quantified. Here, the fundamental limitations of 5f dispersion measurements using angle and momentum resolved variants of photoelectron spectroscopy will be discussed. A novel approach will be suggested, based on a theoretical projection, which should circumvent these limitations: M4,5 X-ray emission spectroscopy. This analysis will utilize the case study of U metal, which can be considered to be the paramount example of 5f dispersion.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Towards the Quantification of 5f Delocalization

By using M4,5 X-ray Emission Spectroscopy (XES) in the tender X-ray regime, it is possible to quantify 5f delocalization in the actinides. Previous analyses, utilizing the Branching Ratio (BR) in the N4,5 X-ray Absorption Spectroscopy (XAS), could not discriminate between the cases of localized n = 2 and delocalized n = 3, in uranium materials, where n is the number of 5f electrons on the U entity. Here, it is shown that, by employing the ubiquitous 6p → 3d XES as a point of normalization, the localized n = 2 and delocalized n = 3 cases can be easily distinguished and quantified.

36 MATERIALS SCIENCE↗