Electron-vibron coupling in halogenated acenaphthenequinone upon O <i>K</i>-edge soft x-ray absorption

Schmidt, Norman Anja; Clark, Timothy; Urquhart, Stephen G.; Fink, R.

doi:10.1063/1.3646732

Cited by 7 publications

(5 citation statements)

References 27 publications

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“…Comparison of excitation energies (ω ex ) of the spectroscopic bright excited states of ANQ (O 1s), thymine (N 1s and O 1s), and the allyl radical (C 1s) calculated using CVS-(U)ADC(2)-x 24,25 and CVS-(U)ADC (3,2) in combination with the 6-311++G** basis set with experimental data. 35,43,87 δ(3-2x) describes the differences of excitation energies between CVS-ADC(2)-x and CVS-ADC(3,2), δ(3-Expt.) describes the differences of excitation energies between CVS-ADC(3,2) and experimental values, and δ(2x-Expt.)…”

Section: Discussionmentioning

confidence: 99%

Analysis and comparison of CVS-ADC approaches up to third order for the calculation of core-excited states

Wenzel

Holzer

Wormit

et al. 2015

The Journal of Chemical Physics

127

196

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The extended second order algebraic-diagrammatic construction (ADC(2)-x) scheme for the polarization operator in combination with core-valence separation (CVS) approximation is well known to be a powerful quantum chemical method for the calculation of core-excited states and the description of X-ray absorption spectra. For the first time, the implementation and results of the third order approach CVS-ADC(3) are reported. Therefore, the CVS approximation has been applied to the ADC(3) working equations and the resulting terms have been implemented efficiently in the adcman program. By treating the α and β spins separately from each other, the unrestricted variant CVS-UADC(3) for the treatment of open-shell systems has been implemented as well. The performance and accuracy of the CVS-ADC(3) method are demonstrated with respect to a set of small and middle-sized organic molecules. Therefore, the results obtained at the CVS-ADC(3) level are compared with CVS-ADC(2)-x values as well as experimental data by calculating complete basis set limits. The influence of basis sets is further investigated by employing a large set of different basis sets. Besides the accuracy of core-excitation energies and oscillator strengths, the importance of cartesian basis functions and the treatment of orbital relaxation effects are analyzed in this work as well as computational timings. It turns out that at the CVS-ADC(3) level, the results are not further improved compared to CVS-ADC(2)-x and experimental data, because the fortuitous error compensation inherent in the CVS-ADC(2)-x approach is broken. While CVS-ADC(3) overestimates the core excitation energies on average by 0.61% ± 0.31%, CVS-ADC(2)-x provides an averaged underestimation of -0.22% ± 0.12%. Eventually, the best agreement with experiments can be achieved using the CVS-ADC(2)-x method in combination with a diffuse cartesian basis set at least at the triple-ζ level.

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Section: Discussionmentioning

confidence: 99%

Analysis and comparison of CVS-ADC approaches up to third order for the calculation of core-excited states

Wenzel

Holzer

Wormit

et al. 2015

The Journal of Chemical Physics

127

196

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“…The most prominent difference between theory and experiment is the missing shoulder in the high energy flank of the lowest excitation peak. In previous experiments additonal fine structures have been observed in high resolution NEXAFS spectra which were identified as coupling of the electronic transitions to various vibronic excitations [50,51]. These features have only been observed in gas phase C K-edge NEXAFS spectra of small aromatic hydrocarbons or in O K-edge NEXAFS spectra of substituted aromatic molecules, which suggests an efficient coupling to C=O stretching mode, while they have not been observed in any C K-edge NEXAFS data of condensed aromatic molecules.…”

Section: Resultsmentioning

confidence: 99%

Analysis of the near-edge X-ray-absorption fine-structure of anthracene: A combined theoretical and experimental study

Klues

Hermann

Witte

2014

The Journal of Chemical Physics

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The near-edge fine structure of the carbon K-edge absorption spectrum of anthracene was measured and theoretically analyzed by DFT calculations implemented in the StoBe code. It is demonstrated that the consideration of electronic relaxation of excited states around localized core holes yields a significant improvement of the calculated excitation energies and reproduces the experimentally observed fine structure well. The detailed analysis of excitation spectra calculated for each symmetry inequivalent excitation center allows in particular to examine the influence of chemical shifts and core hole effects on the excitation energies. Moreover, the visualization of final states explains the large variations in the oscillator strength of various transitions as well as the nature of Rydberg-states that exhibit a notable density of states below the ionization potentials.

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“…It is already the case in organic molecules, the vibronic fine structure of which can be observed in XANES or NEXAFS (Near-Edge Xray Absorption Fine Structure) spectra. For instance in the last ten years, XANES spectroscopy has revealed the vibronic structure of naphtalene, 5 biphenyl 6 and even larger molecules such as NTCDA 7 at the C K-edge, the vibronic structure of acetonitrile 8 and acrylonitrile 9 at the N K-edge, and more recently the one of halogenated acenaphthenequinone 10 at the O K-edge. The vibronic component of the lowest core-excited state of OH and OD was observed at the O K-edge as well.…”

Section: Introduction and State Of The Artmentioning

confidence: 99%

Experimental evidence of thermal fluctuations on the x-ray absorption near-edge structure at the aluminumKedge

et al. 2012

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After a review of temperature-dependent experimental x-ray absorption near-edge structure (XANES) and related theoretical developments, we present the Al K-edge XANES spectra of corundum and beryl for temperature ranging from 300K to 930K. These experimental results provide a first evidence of the role of thermal fluctuation in XANES at the Al K-edge especially in the preedge region. The study is carried out by polarized XANES measurements of single crystals. For any orientation of the sample with respect to the x-ray beam, the pre-edge peak grows and shifts to lower energy with temperature. In addition temperature induces modifications in the position and intensities of the main XANES features. First-principles DFT calculations are performed for both compounds. They show that the pre-edge peak originates from forbidden 1s→3s transitions induced by vibrations. Three existing theoretical models are used to take vibrations into account in the absorption cross section calculations: i) an average of the XANES spectra over the thermal displacements of the absorbing atom around its equilibrium position, ii) a method based on the crude Born-Oppenheimer approximation where only the initial state is averaged over thermal displacements, iii) a convolution of the spectra obtained for the atoms at the equilibrium positions with an approximate phonon spectral function. The theoretical spectra so obtained permit to qualitatively understand the origin of the spectral modifications induced by temperature. However the correct treatment of thermal fluctuation in XANES spectroscopy requires more sophisticated theoretical tools.

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Electron-vibron coupling in halogenated acenaphthenequinone upon O K-edge soft x-ray absorption

Cited by 7 publications

References 27 publications

Analysis and comparison of CVS-ADC approaches up to third order for the calculation of core-excited states

Analysis and comparison of CVS-ADC approaches up to third order for the calculation of core-excited states

Analysis of the near-edge X-ray-absorption fine-structure of anthracene: A combined theoretical and experimental study

Experimental evidence of thermal fluctuations on the x-ray absorption near-edge structure at the aluminumKedge

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