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Zr K edge EXAFS analysis of amorphous materials
by Angshuman Gupta 12 Feb '23

12 Feb '23

Dear everyone, I am working on alumina based amorphous materials containing ZrO2. I am interested in finding the bond length between Zr and O atoms and coordination number (N). Zr K edge spectra were collected at room temperature at 300K along with Zr foil as reference. Extracted So2 from reference (Zr foil) spectra was used to find N in the amorphous material. Local environment around Zr was modelled with harmonic and quasi harmonic models using a third cumulant of the distributions. Theoretical spectra fit well using quasi-harmonic models with large bond length (2.21 A) while harmonic models without third cumulants do not fit the spectra properly and calculating higher N value with 2.16 A as Zr-O bond length. I will be thankful if you kindly let me know what else we can do to improve the fitting and get some meaningful outcome. Any relevant journal articles are also helpful. I have attached the Artemis files. Thanking you Angshuman Gupta PhD research scholar IIT Bombay, Mumbai

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Parameters for parent function in wavelet transform analysis
by Scott Calvin 09 Feb '23

09 Feb '23

Hi all, I’ve never actually tried wavelet transform analysis before, so I’m trying to understand it better, but there’s one aspect that’s puzzling me: The Morlet wavelet has two parameters, eta and sigma. Eta controls how fast it wiggles, and sigma how quickly the function dies out. (Essentially, it’s like the basis function for a Fourier transform multiplied by a Gaussian envelope.) In wavelet analysis we pick a parent function, which is often a Morlet wavelet with particular values of eta and sigma that we have chosen. We then create a set of child functions from the parent function by shifting and dilating the function in k-space. Each child function is then used as a basis function for a transform of chi(k) calculated by integrating over a range of k-values, much like what is done to calculate a Fourier transform. Since the Morlet wavelet is localized in k-space, and the child functions are shifted to focus on different regions of k-space, our wavelet transform produces plots which are a function of k. But since dilating the parent function by different amounts yields child functions with different frequencies, the plots are also a function of R. Therefore the result is a two-dimensional (k and R) contour plot. So far, so good. But what I’m wondering about is the effect of the initial choice of eta and sigma for the parent function. The dimensionless product of eta and sigma has a clear effect. If (eta)(sigma) is small, the parent function will not have very many oscillations of significant size; it it’s large, it will have a lot of oscillations. So if we want good resolution in R (and thus relatively poor resolution in k), we want a big value of (eta)(sigma). In the limit as (eta)(sigma) becomes arbitrarily large, we recover the Fourier transform. If we want good resolution in k, we use a small value for (eta)(sigma). In the limit as (eta)(sigma) becomes arbitrarily small we recover chi(k). That still makes sense to me! But what difference do sigma and eta make individually? In other words, how is sigma = 0.5 and eta = 10.0 different from sigma = 1.0 and eta = 5.0? Since we end up creating child functions that dilate the parent function anyway, I can’t see that it should have any effect at all. And if those two parameters don’t make an independent effect, why do we pretend there are two independent-looking parameters? I’ve seen at least one early paper that suggests choosing eta so that it’s close to the path length you’re most interested in probing, but I can’t see how that actually makes any difference, given the dilation. I expect there’s a good chance I’m missing something obvious, or have a fundamental misunderstanding of part of the process, and look forward to learning more! Best, Scott Calvin Lehman College of the City University of New York

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Upcoming symposium on spectroscopy at large-scale facilities
by Dugan Hayes 08 Feb '23

08 Feb '23

Dear colleagues, The 76th International Symposium on Molecular Spectroscopy to be held June 19-23, 2023 at the University of Illinois Urbana-Champaign is now open for registration. The conference is highly student-oriented, aiming to give any student the opportunity to give an oral contribution. Each year, the ISMS spotlights topics of special interest in mini-symposia, typically lasting three or four half-day sessions. This year, Renske van der Veen, Joost Bakker, and I are organizing a mini-symposium entitled “Spectroscopy at Large-Scale Facilities: from Steady-State to Ultrafast.” The aim is to showcase how spectroscopy at large-scale facilities is practiced and what types of scientific questions can be addressed using the unique capabilities such facilities provide. Below is a short description of the mini-symposium, and more information on ISMS is available at the conference website: https://isms.illinois.edu/ The deadline for abstract submission is *March 1st*. We hope you would be willing to bring ISMS, and in particular our mini-symposium, to the attention of your Ph.D. students and postdocs - and of course urge them to come! Please also pass this announcement along to any other group leaders at your institute and beyond who may be interested. Regards, Dugan Hayes (University of Rhode Island) Joost Bakker (Radboud University, HFML-FELIX) Renske van der Veen (Helmholtz-Zentrum Berlin, BESSY) --------------------------------------------------------- *Spectroscopy at Large-Scale Facilities: from Steady-State to Ultrafast* The general topic of the symposium is IR/XUV/X-ray spectroscopy at synchrotrons and free-electron lasers, applied to, but not limited to the following topics: - Ion/gas-phase/cluster chemistry - Astro- and atmospheric chemistry - Molecules for catalysis and solar energy - Reaction dynamics - Photophysics of organic molecules and transition-metal complexes Symposium description: Large-scale facilities offer unique capabilities for spectroscopic investigations of, e.g., dilute solution-phase samples, clusters, or time-resolved molecular dynamics. With the recent advent of free-electron laser (FEL) facilities, yet a new era of molecular spectroscopy has begun. The goal of this symposium is to bring together the lab-based molecular spectroscopy community (historically largely represented at ISMS) with people from recently emerged fields such as (ultrafast) IR/XUV/X-ray spectroscopy at synchrotrons and FEL facilities. -- Dugan Hayes Assistant Professor | Department of Chemistry | University of Rhode Island Beaupre 374E | 140 Flagg Road | Kingston, RI 02881 (401) 874-5516 | (*he/him*) http://www.chm.uri.edu/hayesgroup/

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FDMNES Simulation for ZnO
by Chen, Danting 06 Feb '23

06 Feb '23

Dear All, I tried to run some simulations through FDMNES about XANES of ZnO with the absorber of Zn, and there are the results for simulated ZnO (red) compared with the experimental one (Green curve). The white line matches well but the two additional peaks are not shown in the spectrum of simulated ZnO. I attached the input file for FDMNES here. Do you have any idea to improve it? I am quite new to running the simulation and would appreciate if you can give me some directions to modify it. Best Wishes, Danting [cid:image001.png@01D937EA.4B65FBB0]

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FEFF simulation of DFT optimized structure at Fe K-edge
by Harry Zhang 25 Jan '23

25 Jan '23

Dear all, Thank you very much for answering many questions related to XAS! I am working on Fe modified zeolites and trying to simulate the Fe K-edge XANES using DFT optimized structures by FEFF10. I found the shape of simulated results are quite similar to the experimental data. However, there is an around 1.4 eV difference between the edge positions of the experimental data and the simulated results. I have calibrated the experimental spectra using reference sample (Fe foil) measured at the same time at synchrotron. I wonder if there are some methods to calibrate the edge energy of the simulated results. Thanks a lot for your help! Best regards, Harry

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Logical range for Amplitude Reduction Factor in EXAFS fitting results
by Esmael Balaghi 24 Jan '23

24 Jan '23

Dear All, I noticed that some published works have reported extremely large values for the amplitude reduction factor. This seems a bit unusual, as the amplitude reduction factor is typically expected to be in the range of 0 to 1. I am curious to know what could be the reasons behind it to get such large values for the amplitude reduction factor during EXAFS fitting. Thank you in advance for your insights. Esmael

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Yttrium standars for oxidation state
by Otal Eugenio 18 Jan '23

18 Jan '23

Hi all, I need to confirm the oxidation state of Y in a sample. I found some reports about Y(II), does someone have something like it? I was looking in the databases and had no luck. Best regards. (^ㅇᆽㅇ^)(=˃ᆺ˂=)(=🝦 ༝ 🝦=) Eugenio H. OTAL Assistant Professor Dept. of Materials Chemistry Shinshu University 4-17-1 Wakasato, Nagano 380-8553, JAPAN eugenio_otal(a)shinshu-u.ac.jp https://sites.google.com/view/zettsu-laboratory/news-updates

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FEFF10 simulation of Pt alloy
by Andy Zhang 16 Jan '23

16 Jan '23

Dear all, I tried to use FEFF10 to simulate the XANES of Pt alloy (Pt L3 edge), and the simulation results fit the XANES collected using TFY mode. However, the white line intensity of the simulated XANES is much lower than the experiential spectra collected using HERFD mode. I wonder if there is way to fit the HERFD XANES results through simulation (in other words, to increase the white line intensity of the simulated XANES). Thanks a lot in advance! Best, Harry

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Positions posts “PostDoc”, “PhD students” in the field of synchrotron-assisted investigations
by Tetyana MILOJEVIC 12 Jan '23

12 Jan '23

Dear colleagues, we announce several positions in the XAS & X-ray crystallography related fields: https://euraxess.ec.europa.eu/jobs/45514 I also attached here a pdf file of the posts. Could you perhaps spread it among your XAS community via your mailing list? Thank you very much in advance! Kind regards Tetyana Milojevic -- ****************************************** Prof. Milojevic Tetyana, PhD Chair of Exobiology at the University of Orléans CNRS, Centre de Biophysique Moléculaire, UPR 4301  3 Av. de la Recherche Scientifique, CS80054 45071 Orléans Cedex 2, France tel:+33 2 38 25 55 48 tetyana.milojevic(a)cnrs-orleans.fr ******************************************

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Gas-phase time-resolved x-ray photoelectron spectroscopy
by Dooshaye Moonshiram 11 Jan '23

11 Jan '23

Dear Colleagues, We are looking for a postdoctoral appointee funded over 2 years in “Gas-phase time-resolved photoelectron spectroscopy in biological and chemical catalysis” at the Instituto de Ciencia de Materiales de Madrid in collaboration with the small quantum systems (SQS) group at the European XFEL facility. The project description and more details can be found in attached call. Many thanks and Best Regards, Dooshaye Moonshiram Ramon y Cajal Group Leader Instituto de Ciencia de Materiales de Madrid 28049, Spain https://moonshiram.wordpress.com/

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