Ultrafast dissociation features in RIXS spectra of the water molecule
Vinicius Vaz, Da Cruz
Rafael C. Couto
Journal Name:Physical Chemistry Chemical Physics
Journal Quartile in Scopus:Q1
Journal Quartile in Web of Science:Q1
Bibliographic Citation:Emelie, Ertan. Ultrafast dissociation features in RIXS spectra of the water molecule [Текст] / Ertan Emelie, Savchenko Viktoriia, Ignatova Nina, Da Cruz Vinicius Vaz, Rafael C. Couto, Eckert Sebastian, Fondell Mattis, Dantz Marcus, Kennedy Brian, Schmitt Thorsten, Pietzsch Annette, Fohlisch Alexander, Faris Gel’mukhanov, Odelius Michael, Kimberg Victor // Physical Chemistry Chemical Physics. — 2018. — № 20. — С. 14384--14397
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 |1sO^-1 4a1^1>. 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 |1b1^-1 4a1^1> 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.