TY  - JOUR
A1  - Niskanen, Johannes
A1  - Sahle, Christoph J.
A1  - Gilmore, Keith
A1  - Uhlig, Frank
A1  - Smiatek, Jens
A1  - Föhlisch, Alexander
T1  - Disentangling structural information from core-level excitation spectra
JF  - Physical review : E, Statistical, nonlinear and soft matter physics
N2  - Core-level spectra of liquids can be difficult to interpret due to the presence of a range of local environments. We present computational methods for investigating core-level spectra based on the idea that both local structural parameters and the x-ray spectra behave as functions of the local atomic configuration around the absorbing site. We identify correlations between structural parameters and spectral intensities in defined regions of interest, using the oxygen K-edge excitation spectrum of liquid water as a test case. Our results show that this kind of analysis can find the main structure-spectral relationships of ice, liquid water, and supercritical water.
Y1  - 2017
U6  - https://doi.org/10.1103/PhysRevE.96.013319
SN  - 2470-0045
SN  - 2470-0053
VL  - 96
PB  - American Physical Society
CY  - College Park
ER  - 
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  - GEN
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
T1  - Reply to Pettersson et al.: Why X-ray spectral features are compatible to continuous distribution models in ambient water
T2  - Proceedings of the National Academy of Sciences of the United States of America
Y1  - 2019
U6  - https://doi.org/10.1073/pnas.1909551116
SN  - 0027-8424
VL  - 116
IS  - 35
SP  - 17158
EP  - 17159
PB  - National Acad. of Sciences
CY  - Washington
ER  -