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Ultrafast dissociation features in RIXS spectra of the water molecule

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Author Ertan Emelie, Savchenko Viktoriia, Ignatova Nina, Vaz da Cruz Vinícius, Couto Rafael C., Eckert Sebastian, Fondell Mattis, Dantz Marcus, Kennedy Brian, Schmitt Thorsten, Pietzsch Annette, Föhlisch Alexander, Gel'mukhanov Faris, Odelius Michael, Kimberg Victor,
Project Coupled spin, charge and orbital dynamics of low-dimensional cuprates
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Original article (peer-reviewed)

Journal Physical Chemistry Chemical Physics
Volume (Issue) 20(21)
Page(s) 14384 - 14397
Title of proceedings Physical Chemistry Chemical Physics
DOI 10.1039/c8cp01807c

Open Access

URL http://doi.org/10.1039/C8CP01807C
Type of Open Access Publisher (Gold Open Access)

Abstract

In this combined theoretical and experimental study we report on an analysis of the resonant inelastic X-ray scattering (RIXS) spectra of gas phase water via the lowest dissociative core-excited state |1s−1O4a11〉. We focus on the spectral feature near the dissociation limit of the electronic ground state. We show that the narrow atomic-like peak consists of the overlapping contribution from the RIXS channels back to the ground state and to the first valence excited state |1b−114a11〉 of the molecule. The spectral feature has signatures of ultrafast dissociation (UFD) in the core-excited state, as we show by means of ab initio calculations and time-dependent nuclear wave packet simulations. We show that the electronically elastic RIXS channel gives substantial contribution to the atomic-like resonance due to the strong bond length dependence of the magnitude and orientation of the transition dipole moment. By studying the RIXS for an excitation energy scan over the core-excited state resonance, we can understand and single out the molecular and atomic-like contributions in the decay to the lowest valence-excited state. Our study is complemented by a theoretical discussion of RIXS in the case of isotopically substituted water (HDO and D2O) where the nuclear dynamics is significantly affected by the heavier fragments' mass.
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