XAFS Journal Club

Modern electronic structure theory and computational methods now permit efficient calculations of ground state properties, as exemplified by the tabulation of many-thousands of structures in the Materials Project . Complementary advances in the theory of excited states have led to efficient methods for calculations of x-ray and electron spectroscopies, e.g., using the real-space Green's multiple […]

The presentation will be a collection of thoughts that I find interesting for the experimentalist employing hard X-ray photon-in/photon-out spectroscopy with a wavelength dispersive instrument. I would like to draw the attention to some experimental aspects and will give hopefully useful advice that may be considered for the experimental protocol. Furthermore, I will present the […]

The new painting materials used by the Impressionists, Fauvists, and Expressionists were critical components of their break with traditional modes of representation. These artists heavily exploited the synthetic organic and inorganic pigments that were newly available as a result of the industrial revolution. However, the bright and novel hues that made their way onto these […]

Presented will be a discussion of efforts to employ a wavelet transform (WT) analysis towards the quantitative structural determination of discrete molecular systems using an EXAFS analysis. Unlike a transition Fourier transform (FT) analysis, a WT analysis yields a 2D plot in both k- and R-space. Thus, information contained in k-space that can be lost […]

Great strides have been made over the past decade in the theory and calculation of X-ray and related spectra. Some advances involve predictions of material properties such as structure or dynamics in order to make a prediction more complete, thus requiring less input, or otherwise reducing the number of free parameters required to fit to […]

The oxidation state of the solid Earth influences, to a first order, the structure of the planet and the chemistry of rocks, ores and volcanic gases; mass transfer of oxygen between terrestrial reservoirs enables a habitable world. Fe K-edge XANES spectroscopy shows magmas erupted from continental crust, formed at subduction zones, are more oxidized than […]

Lunar apatites contain hundreds to thousands of parts per million of sulfur. This is puzzling because lunar basalts are thought to form in low oxygen fugacity (fO2) conditions where sulfur can only exist in its reduced form (S2–), a substitution not previously observed in natural apatite. We present measurements of the oxidation state of S […]

After decades of relative silence, lab-based spectroscopy has made a comeback in recent years. Modern spectrometers have energy resolution comparable to synchrotron XAS beamlines and have performances demonstrated in dozens of recent publications. Here, I will briefly summarize the various technical approaches before focusing on examples for XAFS and XES in the hard and tender […]

The halogens chlorine and bromine have high electron affinities and exist in seawater mainly as chloride and bromide anions, which have generally been considered unreactive in the environment. Using Cl and Br K-edge XANES spectroscopy, we have measured high concentrations of organo-chlorine and -bromine in naturally degraded particulate organic matter (POM) from oceanic sediment traps. […]

Introduction to ELI-Beamlines – a new user facility in the heart of Europe. Status and prospective of ELI X-ray spectroscopy end-station <span data-sheets-value="{"1":2,"2":"Improved access to state-of-the-art facilities is a key element to groundbreaking advances in science. One such facility is the Extreme Light Infrastructure (ELI); a pan-European project of which one pillar (ELI-Beamlines) is located […]

Tracking the structure of functional nanomaterials (e.g., metal catalysts) remains a challenge due to the paucity of experimental techniques that can provide atomic-level information for metal species in harsh conditions, often required for studying chemical transformations. Here we report on the use of X-ray absorption spectroscopy (XANES and EXAFS) and supervised machine learning (SML) for […]