Hello. I was wondering why on an XPS graph (with # emitted electrons vs the binding energy) why there seems to be emitted electrons that don't correspond exactly to an electron energy shell level.
This wikipedia article has some neat images I refer to:
https://en.wikipedia.org/wiki/X-ray_photoelectron_spectroscopy
In the second image labelled "XPS physics - the photoelectric effect*.",* you see a graph with peaks corresponding to particular electron shells, but there's also "mounds" that these peaks rest on.
I was really curious why the mounds seemed to go up and down. Do these mounds correspond to auger electron emissions (i.e "leftover" energy is going into these electrons after a higher energy electron is released and the core shell is filled again?)
Thanks for any response to my perhaps naive question!
https://preview.redd.it/lbsbbgampem41.jpg?width=700&format=pjpg&auto=webp&s=cd06cb5255966c5d90fdfc93b1148c932bbdb223
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Advancement in technology and accuracy, highly reliable x-ray photoelectron spectroscopes and easy availability should drive business growth. Furthermore, introduction of numerous hyphenated technologies by most of the companies to address complex analytical applications should accelerate demand for x-ray photoelectron spectroscopy. The lack of technical labour force and growing competition from advanced technologies may restrain x-ray photoelectron spectroscopy market growth.
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Government initiatives such as "Drug Safety Information Survey" organized by Health Canada and "Safe Use Initiative" by FDA are raising awareness regarding medical R&D, this will offer producers with lucrative growth opportunities over the forecast timeframe.
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Contamination detection is the fastest growing use due to growing demand from semiconductors, pharmaceutical, biotechnology and electronic industry. The growth is attributed due to increase
... keep reading on reddit ➡There may be several answers, but generally? And what elements are used to create this source? Thanks.
Hello, I have no idea on how to do this problem. I'd really appreciate someone showing me how to do this, you can change the element/numbers. Thanks in advance.
Here's what's being asked -
Using photoelectron spectroscopy, the ionization energy of the least tightly bound valence electron on Cl was determined to be 13.0 eV.
Calculate the Zeffective for this electron
Journal of the American Chemical SocietyDOI: 10.1021/jacs.0c06508
https://ift.tt/3hsAGz5
The needed improvements in the activity and stability of Fe/N/C‐based electrocatalysts for the reduction of oxygen or carbon dioxide require a better understanding of their active sites’ structure and electronic properties. To this end, herein we have applied ex situ and in situ X‐ray emission spectroscopy to track the potential‐induced changes in the average spin state of these materials’ molecular Fe‐N x sites.
Abstract
The commercial success of the electrochemical energy conversion technologies required for the decarbonization of the energy sector requires the replacement of the noble metal‐based electrocatalysts currently used in (co‐)electrolyzers and fuel cells with inexpensive, platinum‐group metal‐free analogs. Among these, Fe/N/C‐type catalysts display promising performances for the reduction of O2 or CO2, but their insufficient activity and stability jeopardize their implementation in such devices. To circumvent these issues, a better understanding of the local geometric and electronic structure of their catalytic active sites under reaction conditions is needed. Herein we shed light on the electronic structure of the molecular sites in two Fe/N/C catalysts by probing their average spin state with X‐ray emission spectroscopy (XES). Chiefly, our in situ XES measurements reveal for the first time the existence of reversible, potential‐induced spin state changes in these materials.
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Assigning transition‐metal physical oxidation states is a major goal of X‐ray spectroscopy. However, competing influences of covalency and d‐count on Kβ XES spectra often make assignments ambiguous. It is now shown that resonant Kβ X‐ray emission spectroscopy (RXES) yields unambiguous oxidation‐state determinations for iron monomers, dimers, cubanes, and metalloenzymes.
Abstract
The ability of resonant X‐ray emission spectroscopy (XES) to recover physical oxidation state information, which may often be ambiguous in conventional X‐ray spectroscopy, is demonstrated. By combining Kβ XES with resonant excitation in the XAS pre‐edge region, resonant Kβ XES (or 1s3p RXES) data are obtained, which probe the 3d n+1 final‐state configuration. Comparison of the non‐resonant and resonant XES for a series of high‐spin ferrous and ferric complexes shows that oxidation state assignments that were previously unclear are now easily made. The present study spans iron tetrachlorides, iron sulfur clusters, and the MoFe protein of nitrogenase. While 1s3p RXES studies have previously been reported, to our knowledge, 1s3p RXES has not been previously utilized to resolve questions of metal valency in highly covalent systems. As such, the approach presented herein provides chemists with means to more rigorously and quantitatively address challenging electronic‐structure questions.
https://ift.tt/3lHHuf8
The link between the high‐valent structure of P2‐type sodium layered transition metal oxides and the redox properties involving oxygen redox is demonstrated. By substituting Fe with Cu and Ni from P2‐Na0.67Mn0.5Fe0.5O2, the antisite‐vacancy defect formation is controlled during desodiation of the positive electrodes. Ligand to metal charge transfer and the O 2p state near the Fermi level evoke and stabilize oxygen redox from the electrodes.
Abstract
We investigate high‐valent oxygen redox in the positive Na‐ion electrode P2‐Na0.67−x [Fe0.5Mn0.5]O2 (NMF) where Fe is partially substituted with Cu (P2‐Na0.67−x [Mn0.66Fe0.20Cu0.14]O2, NMFC) or Ni (P2‐Na0.67−x [Mn0.65Fe0.20Ni0.15]O2, NMFN). From combined analysis of resonant inelastic X‐ray scattering and X‐ray near‐edge structure with electrochemical voltage hysteresis and X‐ray pair distribution function profiles, we correlate structural disorder with high‐valent oxygen redox and its improvement by Ni or Cu substitution. Density of states calculations elaborate considerable anionic redox in NMF and NMFC without the widely accepted requirement of an A‐O‐A′ local configuration in the pristine materials (where A=Na and A′=Li, Mg, vacancy, etc.). We also show that the Jahn–Teller nature of Fe4+ and the stabilization mechanism of anionic redox could determine the extent of structural disorder in the materials. These findings shed light on the design principles in TM and anion redox for positive electrodes to improve the performance of Na‐ion batteries.
https://ift.tt/3dkX64x
A three‐dimensional view of chemical heterogeneities in defect‐engineered HKUST‐1 metal–organic framework (MOF) crystals is presented. Cryo‐full‐field XANES computed tomography was used to visualize the presence and distribution of a second coordination polymer of reduced copper coordination within defect‐engineered HKUST‐1 crystals. Observations encourage a revisitation of the structure‐property relationships of defect‐engineered MOFs.
Abstract
The introduction of structural defects in metal–organic frameworks (MOFs), often achieved through the fractional use of defective linkers, is emerging as a means to refine the properties of existing MOFs. These linkers, missing coordination fragments, create unsaturated framework nodes that may alter the properties of the MOF. A property‐targeted utilization of this approach demands an understanding of the structure of the defect‐engineered MOF. We demonstrate that full‐field X‐ray absorption near‐edge structure computed tomography can help to improve our understanding. This was demonstrated by visualizing the chemical heterogeneity found in defect‐engineered HKUST‐1 MOF crystals. A non‐uniform incorporation and zonation of the defective linker was discovered, leading to the presence of clusters of a second coordination polymer within HKUST‐1. The former is suggested to be responsible, in part, for altered MOF properties; thereby, advocating for a spatio‐chemically resolved characterization of MOFs.
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From my understanding, the fermi level of a metal at room temperature indicates an energy level at which 50% of electrons exist above, and 50% exist below. Why then, is the fermi level in UPS spectra of metals observed as a distinct cutoff point? It seems like it should be continuous.
This is my understanding of it: A light (of energy hv) is shined onto a sample of gaseous atoms, which will absorb a certain amount of light (the ionization energy). The difference between the inputted light energy hv and the ionization energy is the kinetic energy that will be released with the electrons.
What I'm not as sure of: Scientists control the voltage of the analyzer (charged magnetic plates?) until the electrons hit the detector and they can measure the kinetic energy of the electrons. This would mean that in the formula hv=IE+KE, they know hv initially (since they control the amount of light?), they test for KE, and they calculate IE... Is this correct?
Edit: saw "photoelectron count rate" on the y-axis of a graph and KE (ev) on the x-axis and now I'm more confused- this means that they control the KE, but how does the # e-/sec give the IE of the gaseous atom?
There is an old video that was on YouTube of an MIT professor explaining PES and it's since been removed. It was a great explanation and now it's gone! All I remember is that he had about 9 chalkboards going at once, moving them up and down, and he draw a picture of the PES device. I'd love to have this file.
Assigning transition‐metal physical oxidation states is a major goal of X‐ray spectroscopy. However, competing influences of covalency and d‐count on Kβ XES spectra often make assignments ambiguous. It is now shown that resonant Kβ X‐ray emission spectroscopy (RXES) yields unambiguous oxidation‐state determinations for iron monomers, dimers, cubanes, and metalloenzymes.
Abstract
The ability of resonant X‐ray emission spectroscopy (XES) to recover physical oxidation state information, which may often be ambiguous in conventional X‐ray spectroscopy, is demonstrated. By combining Kβ XES with resonant excitation in the XAS pre‐edge region, resonant Kβ XES (or 1s3p RXES) data are obtained, which probe the 3d n+1 final‐state configuration. Comparison of the non‐resonant and resonant XES for a series of high‐spin ferrous and ferric complexes shows that oxidation state assignments that were previously unclear are now easily made. The present study spans iron tetrachlorides, iron sulfur clusters, and the MoFe protein of nitrogenase. While 1s3p RXES studies have previously been reported, to our knowledge, 1s3p RXES has not been previously utilized to resolve questions of metal valency in highly covalent systems. As such, the approach presented herein provides chemists with means to more rigorously and quantitatively address challenging electronic‐structure questions.
https://ift.tt/3lHHuf8
Assigning transition‐metal physical oxidation states is a major goal of X‐ray spectroscopy. However, competing influences of covalency and d‐count on Kβ XES spectra often make assignments ambiguous. It is now shown that resonant Kβ X‐ray emission spectroscopy (RXES) yields unambiguous oxidation‐state determinations for iron monomers, dimers, cubanes, and metalloenzymes.
Abstract
The ability of resonant X‐ray emission spectroscopy (XES) to recover physical oxidation state information, which may often be ambiguous in conventional X‐ray spectroscopy, is demonstrated. By combining Kβ XES with resonant excitation in the XAS pre‐edge region, resonant Kβ XES (or 1s3p RXES) data are obtained, which probe the 3d n+1 final‐state configuration. Comparison of the non‐resonant and resonant XES for a series of high‐spin ferrous and ferric complexes shows that oxidation state assignments that were previously unclear are now easily made. The present study spans iron tetrachlorides, iron sulfur clusters, and the MoFe protein of nitrogenase. While 1s3p RXES studies have previously been reported, to our knowledge, 1s3p RXES has not been previously utilized to resolve questions of metal valency in highly covalent systems. As such, the approach presented herein provides chemists with means to more rigorously and quantitatively address challenging electronic‐structure questions.
https://ift.tt/3lHHuf8
Assigning transition‐metal physical oxidation states is a major goal of X‐ray spectroscopy. However, competing influences of covalency and d‐count on Kβ XES spectra often make assignments ambiguous. It is now shown that resonant Kβ X‐ray emission spectroscopy (RXES) yields unambiguous oxidation‐state determinations for iron monomers, dimers, cubanes, and metalloenzymes.
Abstract
The ability of resonant X‐ray emission spectroscopy (XES) to recover physical oxidation state information, which may often be ambiguous in conventional X‐ray spectroscopy, is demonstrated. By combining Kβ XES with resonant excitation in the XAS pre‐edge region, resonant Kβ XES (or 1s3p RXES) data are obtained, which probe the 3d n+1 final‐state configuration. Comparison of the non‐resonant and resonant XES for a series of high‐spin ferrous and ferric complexes shows that oxidation state assignments that were previously unclear are now easily made. The present study spans iron tetrachlorides, iron sulfur clusters, and the MoFe protein of nitrogenase. While 1s3p RXES studies have previously been reported, to our knowledge, 1s3p RXES has not been previously utilized to resolve questions of metal valency in highly covalent systems. As such, the approach presented herein provides chemists with means to more rigorously and quantitatively address challenging electronic‐structure questions.
https://ift.tt/3lHHuf8
