January 2023 - Ifeffit - millenia.cars.aps.anl.gov

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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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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Re: [Ifeffit] Ifeffit Digest, Vol 239, Issue 1 - Cr K-edge spectrum of Cr3C2
by Paktunc, Dogan 07 Jan '23

07 Jan '23

Anna - Please find attached the Cr K-edge spectrum of Cr3C2. It is based on 3 spectra collected at 20BM (APS, PNC-CAT). It has not yet been published but it was referenced to as "ferrochrome" in the following publication: Berryman & Paktunc (2022) Cr(VI) formation in ferrochrome-smelter dusts. J.Hazardous Mat. https://doi.org/10.1016/j.jhazmat.2021.126873 Dogan Dogan Paktunc, PhD Senior Research Scientist - CanmetMINING Natural Resources Canada / Government of Canada 555 Booth Street Ottawa, Ontario, K1A 0G1 Canada Chercheur principal - MINESCanmet Ressources naturelles Canada / Gouvernement du Canada 555 Rue, rue Booth Ottawa, Ontario, K1A 0G1 Canada Cell: (343) 543-9864 dogan.paktunc(a)nrcan-rncan.gc.ca -----Original Message----- From: Ifeffit <ifeffit-bounces(a)millenia.cars.aps.anl.gov> On Behalf Of ifeffit-request(a)millenia.cars.aps.anl.gov Sent: January 6, 2023 13:00 To: ifeffit(a)millenia.cars.aps.anl.gov Subject: Ifeffit Digest, Vol 239, Issue 1 ***Caution - email originated from outside of NRCan. Read the warning below / Attention- Ce courriel provient de l'extérieur des RNCan. Voir la mise en garde ci-dessous*** Send Ifeffit mailing list submissions to ifeffit(a)millenia.cars.aps.anl.gov To subscribe or unsubscribe via the World Wide Web, visit https://can01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fmillenia.c… or, via email, send a message with subject or body 'help' to ifeffit-request(a)millenia.cars.aps.anl.gov You can reach the person managing the list at ifeffit-owner(a)millenia.cars.aps.anl.gov When replying, please edit your Subject line so it is more specific than "Re: Contents of Ifeffit digest..." Today's Topics: 1. Cr3C2 chromium carbide spectrum (Wade, Anna) ---------------------------------------------------------------------- Message: 1 Date: Fri, 6 Jan 2023 17:24:45 +0000 From: "Wade, Anna" <Wade.Anna(a)epa.gov> To: "ifeffit(a)millenia.cars.aps.anl.gov" <ifeffit(a)millenia.cars.aps.anl.gov> Subject: [Ifeffit] Cr3C2 chromium carbide spectrum Message-ID: <DM8PR09MB648534519B6B904F100ABF00E7FB9(a)DM8PR09MB6485.namprd09.prod.outlook.com> Content-Type: text/plain; charset="us-ascii" Dear XAFS community, Does anyone have a spectrum of Cr3C2, chromium (II) carbide standard? Thanks in advance. Sincerely, Anna Wade EPA ORISE Postdoctoral Fellow ORD Land Remediation & Tech. Division 5995 Center Hill Ave Cincinnati, OH 45224 p: 513-569-7815

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Cr3C2 chromium carbide spectrum
by Wade, Anna 06 Jan '23

06 Jan '23

Dear XAFS community, Does anyone have a spectrum of Cr3C2, chromium (II) carbide standard? Thanks in advance. Sincerely, Anna Wade EPA ORISE Postdoctoral Fellow ORD Land Remediation & Tech. Division 5995 Center Hill Ave Cincinnati, OH 45224 p: 513-569-7815

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