TY  - JOUR
A1  - Niskanen, Johannes
A1  - Fondell, Mattis
A1  - Sahle, Christoph J.
A1  - Eckert, Sebastian
A1  - Jay, Raphael Martin
A1  - Gilmore, Keith
A1  - Pietzsch, Annette
A1  - Dantz, Marcus
A1  - Lu, Xingye
A1  - McNally, Daniel E.
A1  - Schmitt, Thorsten
A1  - Vaz da Cruz, Vinicius
A1  - Kimberg, Victor
A1  - Föhlisch, Alexander
A1  - Gel’mukhanov, Faris
T1  - Compatibility of quantitative X-ray spectroscopy with continuous distribution models of water at ambient conditions
JF  - Proceedings of the National Academy of Sciences of the United States of America
N2  - The phase diagram of water harbors controversial views on underlying structural properties of its constituting molecular moieties, its fluctuating hydrogen-bonding network, as well as pair-correlation functions. In this work, long energy-range detection of the X-ray absorption allows us to unambiguously calibrate the spectra for water gas, liquid, and ice by the experimental atomic ionization cross-section. In liquid water, we extract the mean value of 1.74 +/- 2.1% donated and accepted hydrogen bonds per molecule, pointing to a continuous-distribution model. In addition, resonant inelastic X-ray scattering with unprecedented energy resolution also supports continuous distribution of molecular neighborhoods within liquid water, as do X-ray emission spectra once the femtosecond scattering duration and proton dynamics in resonant X-ray-matter interaction are taken into account. Thus, X-ray spectra of liquid water in ambient conditions can be understood without a two-structure model, whereas the occurrence of nanoscale-length correlations within the continuous distribution remains open.
KW  - structure of water
KW  - X-ray spectroscopy
KW  - continuous distribution model
Y1  - 2019
U6  - https://doi.org/10.1073/pnas.1815701116
SN  - 0027-8424
VL  - 116
IS  - 10
SP  - 4058
EP  - 4063
PB  - National Acad. of Sciences
CY  - Washington
ER  - 
TY  - JOUR
A1  - Vaz da Cruz, Vinícius
A1  - Ignatova, Nina
A1  - Couto, Rafael
A1  - Fedotov, Daniil
A1  - Rehn, Dirk R.
A1  - Savchenko, Viktoriia
A1  - Norman, Patrick
A1  - Ågren, Hans
A1  - Polyutov, Sergey
A1  - Niskanen, Johannes
A1  - Eckert, Sebastian
A1  - Jay, Raphael Martin
A1  - Fondell, Mattis
A1  - Schmitt, Thorsten
A1  - Pietzsch, Annette
A1  - Föhlisch, Alexander
A1  - Odelius, Michael
A1  - Kimberg, Victor
A1  - Gel’mukhanov, Faris
T1  - Nuclear dynamics in resonant inelastic X-ray scattering and X-ray absorption of methanol
JF  - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr
N2  - We report on a combined theoretical and experimental study of core-excitation spectra of gas and liquid phase methanol as obtained with the use of X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS). The electronic transitions are studied with computational methods that include strict and extended second-order algebraic diagrammatic construction [ADC(2) and ADC(2)-x], restricted active space second-order perturbation theory, and time-dependent density functional theory-providing a complete assignment of the near oxygen K-edge XAS. We show that multimode nuclear dynamics is of crucial importance for explaining the available experimental XAS and RIXS spectra. The multimode nuclear motion was considered in a recently developed "mixed representation" where dissociative states and highly excited vibrational modes are accurately treated with a time-dependent wave packet technique, while the remaining active vibrational modes are described using Franck-Condon amplitudes. Particular attention is paid to the polarization dependence of RIXS and the effects of the isotopic substitution on the RIXS profile in the case of dissociative core-excited states. Our approach predicts the splitting of the 2a RIXS peak to be due to an interplay between molecular and pseudo-atomic features arising in the course of transitions between dissociative core- and valence-excited states. The dynamical nature of the splitting of the 2a peak in RIXS of liquid methanol near pre-edge core excitation is shown. The theoretical results are in good agreement with our liquid phase measurements and gas phase experimental data available from the literature. (C) 2019 Author(s).
Y1  - 2019
U6  - https://doi.org/10.1063/1.5092174
SN  - 0021-9606
SN  - 1089-7690
VL  - 150
IS  - 23
PB  - American Institute of Physics
CY  - Melville
ER  -