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Selective gating to vibrational modes through resonant X-ray scattering
KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.ORCID iD: 0000-0003-4020-0923
KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

AbstractIn this study we use the gas-phase water to demonstrate how dierent intermediate core-excitedstates in ultra-high resolution resonant inelastic X-ray scattering (RIXS) may act as selective gatesto specic vibrational modes by means of spatially selective nuclear dynamics in the core-excitedstate. The alignment of the wave packet along the OH bonds and between the bonds for the |1a1-14a11>  and |1a1-12b21> states, respectively, allows to probe vibrational states aligned preferen-tially along these directions. The combination of experiment with state-of-the-art ab initio calcula-tions allows to explain this selectivity and observed propensity rule with a detailed analysis of thepotential energy surfaces (PESs) of the ground and core-excited states and by making use of thetime-dependent wave packet picture. We show that the RIXS technique makes it possible to probeextended regions of the ground state PES along each internal degree of freedom and to study theregime of normal-to-local mode transitions for symmetric molecules A2B. In particular, the abilityto visualize the transition from the normal to the local mode regimes by means of RIXS may beimportant for mapping chemical reactions.

Keyword [en]
water, resonant elastic x-ray scattering, vibrational modes, RIXS
National Category
Atom and Molecular Physics and Optics
Research subject
Theoretical Chemistry and Biology
Identifiers
URN: urn:nbn:se:kth:diva-187011OAI: oai:DiVA.org:kth-187011DiVA: diva2:928528
Funder
Knut and Alice Wallenberg Foundation, KAW-2013.0020
Note

QCR 20160517

Available from: 2016-05-16 Created: 2016-05-16 Last updated: 2016-05-17Bibliographically 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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