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Guo M, Braun A, Sokaras D, Kroll T. Iron Kβ X-ray Emission Spectroscopy: The Origin of Spectral Features from Atomic to Molecular Systems Using Multi-configurational Calculations. J Phys Chem A 2024; 128:1260-1273. [PMID: 38329897 DOI: 10.1021/acs.jpca.3c07949] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/10/2024]
Abstract
Kβ X-ray emission spectroscopy (XES) is widely used to fingerprint the local spin of transition-metal ions, including in pump-probe experiments, to identify excited states or in chemical and biological reactions to characterize short-lived intermediates. In this study, the spectra of ferrous and ferric complexes for various spin states were measured experimentally and described theoretically through restricted active space (RAS) calculations including dynamic correlations. Through the RAS calculations from simple atomic models to complex molecular systems, spectral effects such as the exchange interactions, crystal-field strength, and covalent orbital mixing were evaluated and discussed. The calculations find that only the spectral features of low-spin cases show a dependence on the crystal-field strength, particularly for ferrous low spin. The effect of the covalent orbital mixing strength on the first moment of the Kβ1,3 main line and the Kβ1,3-Kβ' energy splitting is quantitatively described. Clear relationships are found within a given nominal spin but less between different spin states, which calls for careful selection of reference spectra in future experiments. This study further advances our understanding of the correlation between changes in experimental spectral features and their corresponding electronic structure information.
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Affiliation(s)
- Meiyuan Guo
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
| | - Augustin Braun
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Dimosthenis Sokaras
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
| | - Thomas Kroll
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
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Huyke DA, Ramachandran A, Ramirez-Neri O, Guerrero-Cruz JA, Gee LB, Braun A, Sokaras D, Garcia-Estrada B, Solomon EI, Hedman B, Delgado-Jaime MU, DePonte DP, Kroll T, Santiago JG. Millisecond timescale reactions observed via X-ray spectroscopy in a 3D microfabricated fused silica mixer. Corrigendum. JOURNAL OF SYNCHROTRON RADIATION 2022; 29:930. [PMID: 35511027 PMCID: PMC9070710 DOI: 10.1107/s1600577522002806] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
A figure in the article by Huyke et al. [(2021), J. Synchrotron Rad. 28, 1100-1113] is corrected.
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Affiliation(s)
| | | | | | | | | | | | - Dimosthenis Sokaras
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA 94025, USA
| | | | - Edward I. Solomon
- Stanford University, Stanford, CA 94305, USA
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA 94025, USA
| | - Britt Hedman
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA 94025, USA
| | | | - Daniel P. DePonte
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA 94025, USA
| | - Thomas Kroll
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA 94025, USA
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Brenker J, Henzler K, Borca CN, Huthwelker T, Alan T. X-ray compatible microfluidics for in situ studies of chemical state, transport and reaction of light elements in an aqueous environment using synchrotron radiation. LAB ON A CHIP 2022; 22:1214-1230. [PMID: 35170605 DOI: 10.1039/d1lc00996f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
This paper presents an X-ray compatible microfluidic platform for in situ characterization of chemical reactions at synchrotron light sources. We demonstrate easy to implement techniques to probe reacting solutions as they first come into contact, and study the very first milliseconds of their reaction in real-time through X-ray absorption spectroscopy (XAS). The devices use polydimethylsiloxane (PDMS) microfluidic channels sandwiched between ultrathin, X-ray transparent silicon nitride observation windows and rigid substrates. The new approach has three key advantages: i) owing to the assembly techniques employed, the devices are suitable for both high energy and tender (1-5 keV) X-rays; ii) they can operate in a vacuum environment (a must for low energy X-rays) and iii) they are robust enough to survive a full 8 hour shift of continuous scanning with a micro-focused beam, providing higher spatial and thus greater time resolution than previous studies. The combination of these opens new opportunities for in situ studies. This has so far not been possible with Kapton or glass-based flow cells due to increased attenuation of the low energy beam passing through these materials. The devices provide a well-defined mixing region to collect spatial maps of spatially stable concentration profiles, and XAS point spectra to elucidate the chemical structure and characterize the chemical reactions. The versatility of the approach is demonstrated through in situ XAS measurements on the mixing of two reactants in a microfluidic laminar flow device, as well as a segmented droplet based system for time resolved analysis.
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Affiliation(s)
- Jason Brenker
- Department of Mechanical and Aerospace Engineering, Monash University, Clayton, Australia.
| | - Katja Henzler
- Paul Scherrer Institute, Swiss Light Source, Villigen, Switzerland.
| | - Camelia N Borca
- Paul Scherrer Institute, Swiss Light Source, Villigen, Switzerland.
| | | | - Tuncay Alan
- Department of Mechanical and Aerospace Engineering, Monash University, Clayton, Australia.
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