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Anomalously strong two-electron one-photon X-ray decay transitions in CO caused by avoided crossing
KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. Univ Fed Goias, Brazil.ORCID iD: 0000-0003-4020-0923
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2016 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 6, 20947Article in journal (Refereed) PublishedText
Abstract [en]

The unique opportunity to study and control electron-nuclear quantum dynamics in coupled potentials offered by the resonant inelastic X-ray scattering (RIXS) technique is utilized to unravel an anomalously strong two-electron one-photon transition from core-excited to Rydberg final states in the CO molecule. High-resolution RIXS measurements of CO in the energy region of 12-14 eV are presented and analyzed by means of quantum simulations using the wave packet propagation formalism and ab initio calculations of potential energy curves and transition dipole moments. The very good overall agreement between the experimental results and the theoretical predictions allows an in-depth interpretation of the salient spectral features in terms of Coulomb mixing of "dark" with "bright" final states leading to an effective two-electron one-photon transition. The present work illustrates that the improved spectral resolution of RIXS spectra achievable today may call for more advanced theories than what has been used in the past.

Place, publisher, year, edition, pages
Nature Publishing Group, 2016. Vol. 6, 20947
National Category
Engineering and Technology Atom and Molecular Physics and Optics
Identifiers
URN: urn:nbn:se:kth:diva-183187DOI: 10.1038/srep20947ISI: 000369829300001PubMedID: 26860458ScopusID: 2-s2.0-84957534824OAI: oai:DiVA.org:kth-183187DiVA: diva2:908940
Funder
Swedish National Infrastructure for Computing (SNIC), SNIC 2015/1-69; SNIC 023/07-18Swedish Research CouncilKnut and Alice Wallenberg Foundation, KAW-2013.0020
Note

QC 20160303

Available from: 2016-03-03 Created: 2016-03-03 Last updated: 2016-09-21Bibliographically approved
In thesis
1. Coupled electron-nuclear dynamics in inelastic X-ray scattering
Open this publication in new window or tab >>Coupled electron-nuclear dynamics in inelastic X-ray scattering
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This Thesis is devoted to theoretical and experimental studies of resonant inelastic X-ray scattering (RIXS) of carbon monoxide and water molecules. Using state-of-the-art ab initio electronic structure calculations and a time-dependent wave packet formalism, we make a complete analysis of the experimental RIXS spectra of the two molecular systems. In the CO RIXS analysis, we are able to reproduce the RIXS experiment with an excellent accuracy. Interference between different RIXS channels corresponding to the scattering via orthogonal molecular orbitals in the core-excited state of CO is described. We show the complete breakdown of the Born-Oppenheimer approximation in the region where forbidden final Rydberg states are mixed with a valence allowed final state. Here we explain the formation of a spectral feature which was attributed to a single state in previous studies. Moreover, through an experimental-theoretical combination, we improve the minimum of the valence E’Π excited state potential, along with the coupling constant between two Rydberg states. We developed a new theoretical approach to describe triatomic molecules through the wave packet propagation formalism to study the water system, which reproduces with high accuracy the vibrational structure of the high-resolution experimental quasi-elastic RIXS spectra. We demonstrate that due to the vibrational mode coupling and anharmonicity of the ground and core-excited potential energy surfaces, different core-excited states in RIXS can be used as gates to probe different vibrational dynamics and to map the ground state potential. Isotopic substitution is investigated by theoretical simulations and important dynamical features are discussed, especially for the dissociative core-excited state, where a so-called “atomic” peak is formed. We show the strong potential of high-resolution RIXS experiments combined with high-level theoretical simulations for advanced studies of highly excited molecular states.

Place, publisher, year, edition, pages
Stockholm, Sweden: KTH Royal Institute of Technology, 2016. 87 p.
Series
TRITA-BIO-Report, ISSN 1654-2312 ; 2016:10
Keyword
X-ray spectroscopy, resonant inelastic X-ray scattering, water, carbon monoxide
National Category
Theoretical Chemistry
Research subject
Theoretical Chemistry and Biology
Identifiers
urn:nbn:se:kth:diva-186530 (URN)978-91-7595-988-7 (ISBN)
Public defence
2016-06-08, FB53, AlbaNova University Center, Roslagstullsbacken 21, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
Knut and Alice Wallenberg Foundation, KAW-2013.0020
Note

QC 20160516

Available from: 2016-05-16 Created: 2016-05-12 Last updated: 2016-05-16Bibliographically approved

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