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X-ray scattering and spectroscopy of supercooled water and ice
Stockholm University, Faculty of Science, Department of Physics. (Chemical Physics)ORCID iD: 0000-0003-2793-5052
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis presents experimental studies of water and ice at near-atmospheric pressures using intense x-rays only accessible at synchrotrons and free-electron lasers. In particular, it focuses on the deeply supercooled, metastable state and its implications on ice nucleation.

The local structure of the liquid phase was studied by x-ray scattering over a wide temperature range extending from 339 K down to 227 K. In order to be able to study the deeply supercooled liquid, micron-sized water droplets were evaporatively cooled in vacuum and probed by ultrashort x-ray pulses. This is to date the lowest temperature at which measurements of the structure have been performed on bulk liquid water cooled from room temperature. Upon deep supercooling, the structure evolved toward that of a low-density liquid with local tetrahedral coordination. At ~230 K, where the low-density liquid structure started to dominate, the number of droplets containing ice nuclei increased rapidly. The estimated nucleation rate suggests that there is a “fragile-to-strong” transition in the dynamics of the liquid below 230 K, and its implications on water structure are discussed.

Similarly, the electronic structure of deeply supercooled water was studied by x-ray emission spectroscopy down to 222 K, but the spectral changes expected from the structural transformation remained absent and explanations are discussed. At high fluence, the non-linear dependence of the x-ray emission yield indicated that there were high valence hole densities created during the x-ray pulse length due to Auger cascades, resulting in reabsorption of the x-ray emission.

Finally, the hydrogen-bonded network in water was studied by x-ray absorption spectroscopy and compared to various ices. It was found that the pre-edge absorption cross-section, which is associated with distorted hydrogen bonds, could be minimized for crystalline ice grown on a hydrophobic BaF2(111) surface with low concentration of nucleation centers.

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm Univeristy , 2014. , 148 p.
Keyword [en]
supercooled water, ice, x-ray scattering, x-ray spectroscopy, free-electron laser
National Category
Physical Chemistry
Research subject
Chemical Physics
Identifiers
URN: urn:nbn:se:su:diva-103009ISBN: 978–91–7447–902–7 OAI: oai:DiVA.org:su-103009DiVA: diva2:714287
Public defence
2014-05-30, FA32, AlbaNova Universitetscentrum, Roslagstullsbacken 21, Stockholm, 10:15 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 3: Manuscript. Paper 4: Manuscript. Paper 5: Manuscript. Paper 6: Manuscript.

Available from: 2014-05-08 Created: 2014-04-26 Last updated: 2015-09-18Bibliographically approved
List of papers
1. Wide-angle X-ray diffraction and molecular dynamics study of medium-range order in ambient and hot water
Open this publication in new window or tab >>Wide-angle X-ray diffraction and molecular dynamics study of medium-range order in ambient and hot water
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2011 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 13, no 44, 19997-20007 p.Article in journal (Refereed) Published
Abstract [en]

We have developed wide-angle X-ray diffraction measurements with high energy-resolution and accuracy to study water structure at three different temperatures (7, 25 and 66 degrees C) under normal pressure. Using a spherically curved Ge crystal an energy resolution better than 15 eV has been achieved which eliminates influence from Compton scattering. The high quality of the data allows for a reliable Fourier transform of the experimental data resolving shell structure out to similar to 12 angstrom, i.e. 5 hydration shells. Large-scale molecular dynamics (MD) simulations using the TIP4P/2005 force-field reproduce excellently the experimental shell-structure in the range 4-12 angstrom although less agreement is seen for the first peak in the intermolecular pair-correlation function (PCF). The Shiratani-Sasai Local Structure Index [J. Chem. Phys. 104, 7671 (1996)] identifies a tetrahedral minority giving the intermediate-range oscillations in the O-O PCF and a disordered majority providing a more featureless background in this range. The current study supports the proposal that the structure of liquid water, even at high temperatures, can be described in terms of a two-state fluctuation model involving local structures related to the high-density and low-density forms of liquid water postulated in the liquid-liquid phase transition hypothesis.

National Category
Physical Chemistry Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:su:diva-71018 (URN)10.1039/c1cp22804h (DOI)000296383100038 ()
Note
8Available from: 2012-01-25 Created: 2012-01-25 Last updated: 2014-04-28Bibliographically approved
2. Experimental Observation of Bulk Liquid Water Structure in “No-man’s Land”
Open this publication in new window or tab >>Experimental Observation of Bulk Liquid Water Structure in “No-man’s Land”
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(English)Manuscript (preprint) (Other academic)
Keyword
supercooled water, x-ray scattering, free-electron laser
National Category
Physical Chemistry
Research subject
Chemical Physics
Identifiers
urn:nbn:se:su:diva-103003 (URN)
Available from: 2014-04-25 Created: 2014-04-25 Last updated: 2014-07-31
3. Anomalous Behavior of the Homogeneous Ice Nucleation Rate in No-Man's Land
Open this publication in new window or tab >>Anomalous Behavior of the Homogeneous Ice Nucleation Rate in No-Man's Land
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2015 (English)In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 6, no 14, 2826-2832 p.Article in journal (Refereed) Published
Abstract [en]

We present an analysis of ice nucleation kinetics from near-ambient pressure water as temperature decreases below the homogeneous limit T-H by cooling micrometer-sized droplets (microdroplets) evaporatively at 10(3)-10(4) K/s and probing the structure ultrafast using femtosecond pulses from the Linac Coherent Light Source (LCLS) free-electron X-ray laser. Below 232 K, we observed a slower nucleation rate increase with decreasing temperature than anticipated from previous measurements, which we suggest is due to the rapid decrease in water's diffusivity. This is consistent with earlier findings that microdroplets do not crystallize at <227 K, but vitrify at cooling rates of 10(6)-10(7) K/s. We also hypothesize that the slower increase in the nucleation rate is connected with the proposed fragile-to-strong transition anomaly in water.

National Category
Chemical Sciences Nano Technology Physical Sciences
Research subject
Theoretical Physics
Identifiers
urn:nbn:se:su:diva-119545 (URN)10.1021/acs.jpclett.5b01164 (DOI)000358339600028 ()
Available from: 2015-08-20 Created: 2015-08-17 Last updated: 2015-09-18Bibliographically approved
4. Comparison of x-ray absorption spectra between water and ice: new ice data with low pre-edge absorption cross-section
Open this publication in new window or tab >>Comparison of x-ray absorption spectra between water and ice: new ice data with low pre-edge absorption cross-section
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(English)Manuscript (preprint) (Other academic)
Keyword
x-ray absorption spectroscopy, water, ice, principal component analysis
National Category
Physical Chemistry
Research subject
Chemical Physics
Identifiers
urn:nbn:se:su:diva-103006 (URN)
Available from: 2014-04-25 Created: 2014-04-25 Last updated: 2014-04-30Bibliographically approved
5. Reabsorption of Soft X-Ray Emission at High X-Ray Free-Electron Laser Fluences
Open this publication in new window or tab >>Reabsorption of Soft X-Ray Emission at High X-Ray Free-Electron Laser Fluences
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2014 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 113, no 15, 153002- p.Article in journal (Refereed) Published
Abstract [en]

We report on oxygen K-edge soft x-ray emission spectroscopy from a liquid water jet at the Linac Coherent Light Source. We observe significant changes in the spectral content when tuning over a wide range of incident x-ray fluences. In addition the total emission yield decreases at high fluences. These modifications result from reabsorption of x-ray emission by valence-excited molecules generated by the Auger cascade. Our observations have major implications for future x-ray emission studies at intense x-ray sources. We highlight the importance of the x-ray pulse length with respect to the core-hole lifetime.

National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-110198 (URN)10.1103/PhysRevLett.113.153002 (DOI)000344245600005 ()
Note

AuthorCount:24;

Available from: 2014-12-09 Created: 2014-12-08 Last updated: 2015-09-18Bibliographically approved
6. X-ray emission spectroscopy of bulk liquid water in no-man's land
Open this publication in new window or tab >>X-ray emission spectroscopy of bulk liquid water in no-man's land
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2015 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 142, no 4, 044505Article in journal (Refereed) Published
Abstract [en]

The structure of bulk liquid water was recently probed by x-ray scattering below the temperature limit of homogeneous nucleation (T-H) of similar to 232 K [J. A. Sellberg et al., Nature 510, 381-384 (2014)]. Here, we utilize a similar approach to study the structure of bulk liquid water below T-H using oxygen K-edge x-ray emission spectroscopy (XES). Based on previous XES experiments [T. Tokushima et al., Chem. Phys. Lett. 460, 387-400 (2008)] at higher temperatures, we expected the ratio of the 1b(1)' and 1b(1) peaks associated with the lone-pair orbital in water to change strongly upon deep supercooling as the coordination of the hydrogen (H-) bonds becomes tetrahedral. In contrast, we observed only minor changes in the lone-pair spectral region, challenging an interpretation in terms of two interconverting species. A number of alternative hypotheses to explain the results are put forward and discussed. Although the spectra can be explained by various contributions from these hypotheses, we here emphasize the interpretation that the line shape of each component changes dramatically when approaching lower temperatures, where, in particular, the peak assigned to the proposed disordered component would become more symmetrical as vibrational interference becomes more important.

National Category
Physical Sciences Chemical Sciences
Identifiers
urn:nbn:se:su:diva-115298 (URN)10.1063/1.4905603 (DOI)000349018100034 ()25637993 (PubMedID)
Note

AuthorCount:26;

Available from: 2015-04-01 Created: 2015-03-18 Last updated: 2015-09-18Bibliographically approved

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