Vibrationally resolved NEXAFS at C and N K-edges of pyridine, 2-fluoropyridine and 2,6-difluoropyridine: A combined experimental and theoretical assessment
| Autor: | Marcello Coreno, Alberto Baiardi, Vincenzo Barone, Mauro Stener, Gustavo Adolfo Cardenas Jimenez, Cesare Grazioli, Monica de Simone, Giovanna Fronzoni, Marco Mendolicchio |
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| Přispěvatelé: | Baiardi, Alberto, Mendolicchio, Marco, Barone, Vincenzo, Fronzoni, Giovanna, Cardenas Jimenez, Gustavo Adolfo, Stener, Mauro, Grazioli, Cesare, De Simone, Monica, Coreno, Marcello, Cardenas, GUSTAVO ADOLFO |
| Jazyk: | angličtina |
| Rok vydání: | 2015 |
| Předmět: |
Physics
pyridine Physics and Astronomy (all) Physical and Theoretical Chemistry Extended X-ray absorption fine structure Absorption spectroscopy Gaussian General Physics and Astronomy C K-edge Molecular physics Spectral line NEXAFS core electron symbols.namesake Quantum mechanics symbols Gaussian function Density functional theory vibration Scaling Basis set |
| Zdroj: | The Journal of chemical physics 143 (2015): 204102-1–204102-12. doi:10.1063/1.4935715 info:cnr-pdr/source/autori:Baiardi, Alberto%2F1; Mendolicchio, Marco%2F1; Barone, Vincenzo%2F1; Fronzoni, Giovanna%2F2; Cardenas Jimenez%2F2, Gustavo Adolfo%2F2; Stener, Mauro%2F2; Grazioli, Cesare%2F2,3; de Simone, Monica%2F3; Coreno, Marcello%2F4/titolo:Vibrationally resolved NEXAFS at C and N K-edges of pyridine, 2-fluoropyridine and 2,6-difluoropyridine: A combined experimental and theoretical assessment./doi:10.1063%2F1.4935715/rivista:The Journal of chemical physics/anno:2015/pagina_da:204102-1/pagina_a:204102-12/intervallo_pagine:204102-1–204102-12/volume:143 |
| DOI: | 10.1063/1.4935715 |
| Popis: | In the present work, the near edge X-ray absorption spectroscopy (NEXAFS) spectra at both C and N K-edges of pyridine, 2-fluoropyridine, and 2,6-difluoropyridine have been studied both experimentally and theoretically. From an electronic point of view, both transition potential density functional theory and time-dependent density functional theory approaches lead to reliable results provided that suitable basis sets and density functionals are employed. In this connection, the global hybrid B3LYP functional in conjunction with the EPR-III basis set appears particularly suitable after constant scaling of the band positions. For the N K-edge, vertical energies obtained at these levels and broadened by symmetric Gaussian distributions provide spectra in reasonable agreement with the experiment. Vibronic contributions further modulate the band-shapes leading to a better agreement with the experimental results, but are not strictly necessary for semi-quantitative investigations. On the other hand, vibronic contributions are responsible for strong intensity redistribution in the NEXAFS C K-edge spectra, and their inclusion is thus mandatory for a proper description of experiments. In this connection, the simple vertical gradient model is particularly appealing in view of its sufficient reliability and low computational cost. For more quantitative results, the more refined vertical Hessian approach can be employed, and its effectiveness has been improved thanks to a new least-squares fitting approach. |
| Databáze: | OpenAIRE |
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