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Title: Resonant x-ray emission spectroscopy of liquid water: novel instrumentation, high resolution, and the"map" approach

Abstract

Techniques to study the electronic structure of liquids are rare. Most recently, resonant x-ray emission spectroscopy (XES) has been shown to be an extremely versatile spectroscopy to study both occupied and unoccupied electronic states for liquids in thermodynamic equilibrium. However, XES requires high-brilliance soft x-ray synchrotron radiation and poses significant technical challenges to maintain a liquid sample in an ultra-high vacuum environment. Our group has therefore developed and constructed a novel experimental setup for the study of liquids, with the long-term goal of investigating the electronic structure of biological systems in aqueous environments. We have developed a flow-through liquid cell in which the liquid is separated from vacuum by a thin Si3N4 or SiC window and which allows a precise control of temperature. This approach has significant advantages compared to static liquids cells used in the past. Furthermore, we have designed a dedicated high-transmission, high-resolution soft x-ray spectrometer. The high transmission makes it possible to measure complete resonant XES"maps" in less than an hour, giving unprecedented detailed insight into the electronic structure of the investigated sample. Using this new equipment we have investigated the electronic structure of liquid water. Furthermore, our XES spectra and maps give information about ultra-fast dissociationmore » on the timescale of the O 1s core hole lifetime, which is strongly affected by the initial state hydrogen bonding configuration.« less

Authors:
; ; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
Advanced Light Source Division
OSTI Identifier:
971354
Report Number(s):
LBNL-2309E
Journal ID: ISSN 0368-2048; JESRAW; TRN: US1001166
DOE Contract Number:
DE-AC02-05CH11231
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Electron Spectroscopy and Related Phenomena; Related Information: Journal Publication Date: March 2009 online
Country of Publication:
United States
Language:
English
Subject:
36; BONDING; CONFIGURATION; DISSOCIATION; ELECTRONIC STRUCTURE; EMISSION SPECTROSCOPY; HYDROGEN; LIFETIME; RESOLUTION; SPECTRA; SPECTROSCOPY; SYNCHROTRON RADIATION; THERMODYNAMICS; WATER; WINDOWS; X-RAY SPECTROMETERS; water, RIXS, x-ray emission

Citation Formats

Weinhardt, L., Fuchs, O., Blum, M., Bär, M., Weigand, M., Denlinger, J.D., Zubavichus, Y., Zharnikov, M., Grunze, M., Heske, C., and Umbach, E. Resonant x-ray emission spectroscopy of liquid water: novel instrumentation, high resolution, and the"map" approach. United States: N. p., 2008. Web.
Weinhardt, L., Fuchs, O., Blum, M., Bär, M., Weigand, M., Denlinger, J.D., Zubavichus, Y., Zharnikov, M., Grunze, M., Heske, C., & Umbach, E. Resonant x-ray emission spectroscopy of liquid water: novel instrumentation, high resolution, and the"map" approach. United States.
Weinhardt, L., Fuchs, O., Blum, M., Bär, M., Weigand, M., Denlinger, J.D., Zubavichus, Y., Zharnikov, M., Grunze, M., Heske, C., and Umbach, E. 2008. "Resonant x-ray emission spectroscopy of liquid water: novel instrumentation, high resolution, and the"map" approach". United States. doi:. https://www.osti.gov/servlets/purl/971354.
@article{osti_971354,
title = {Resonant x-ray emission spectroscopy of liquid water: novel instrumentation, high resolution, and the"map" approach},
author = {Weinhardt, L. and Fuchs, O. and Blum, M. and Bär, M. and Weigand, M. and Denlinger, J.D. and Zubavichus, Y. and Zharnikov, M. and Grunze, M. and Heske, C. and Umbach, E.},
abstractNote = {Techniques to study the electronic structure of liquids are rare. Most recently, resonant x-ray emission spectroscopy (XES) has been shown to be an extremely versatile spectroscopy to study both occupied and unoccupied electronic states for liquids in thermodynamic equilibrium. However, XES requires high-brilliance soft x-ray synchrotron radiation and poses significant technical challenges to maintain a liquid sample in an ultra-high vacuum environment. Our group has therefore developed and constructed a novel experimental setup for the study of liquids, with the long-term goal of investigating the electronic structure of biological systems in aqueous environments. We have developed a flow-through liquid cell in which the liquid is separated from vacuum by a thin Si3N4 or SiC window and which allows a precise control of temperature. This approach has significant advantages compared to static liquids cells used in the past. Furthermore, we have designed a dedicated high-transmission, high-resolution soft x-ray spectrometer. The high transmission makes it possible to measure complete resonant XES"maps" in less than an hour, giving unprecedented detailed insight into the electronic structure of the investigated sample. Using this new equipment we have investigated the electronic structure of liquid water. Furthermore, our XES spectra and maps give information about ultra-fast dissociation on the timescale of the O 1s core hole lifetime, which is strongly affected by the initial state hydrogen bonding configuration.},
doi = {},
journal = {Journal of Electron Spectroscopy and Related Phenomena},
number = ,
volume = ,
place = {United States},
year = 2008,
month = 6
}
  • In Ref. [1], we present and analyze experimental high resolution x-ray emission spectra (XES) of liquid water which exhibit a splitting of the 1b1 line into two components. We also suggest a qualitative model to explain the experimental spectra which, even though tentative (as clearly stated in the summary of Ref. [1]), is able to explain ALL available experimental data. In the preceding Comment, Pettersson et al. [3]claim that a spectrum with two similarly sharp 1b1 features both from a dissociated product (d2) and from the intact molecule (d1) would be"unphysical and unsubstantiated" since"the path connecting initial and final structure"more » is not taken into account. In the meantime, we have collected new data [2], which further support and strengthen our model.« less
  • High-resolution x-ray absorption and emission spectra ofliquid water exhibit a strong isotope effect. Further, the emissionspectra show a splitting of the 1b1 emission line, a weak temperatureeffect, and a pronounced excitation-energy dependence. They can bedescribed as a superposition of two independent contributions. Bycomparing with gasphase, ice, and NaOH/NaOD, we propose that the twocomponents are governed by the initial state hydrogen bondingconfiguration and ultrafast dissociation on the time scale of the O 1score hole decay.
  • External quantum efficiency (EQE) of photoluminescence as high as 20 percent from isolated ZnO nanowires were measured at room temperature. The EQE was found to be highly dependent on photoexcitation density, which underscores the importance of uniform optical excitation during the EQE measurement. An integrating sphere coupled to a microscopic imaging system was used in this work, which enabled the EQE measurement on isolated ZnO nanowires. The EQE values obtained here are significantly higher than those reported for ZnO materials in forms of bulk, thin films or powders. Additional insight on the radiative extraction factor of one-dimensional nanostructures was gainedmore » by measuring the internal quantum efficiency of individual nanowires. Such quantitative EQE measurements provide a sensitive, noninvasive method to characterize the optical properties of low-dimensional nanostructures and allow tuning of synthesis parameters for optimization of nanoscale materials.« less
  • W415 is a chiral smectic compound with a remarkably weak temperature dependence of its giant electroclinic effect in the liquid crystalline smectic A* phase. Furthermore it possesses a high spontaneous polarization in the smectic C* phase. The origin of this striking electroclinic effect is the co-occurrence of a de Vries-type ordering with a weak first-order tilting transition (see the synchroton X-ray scattering profiles).
  • A novel approach to the application of high-resolution electron-energy-loss spectroscopy to polar materials is demonstrated in this Letter. By using a high-impact-energy beam and an off-specular scattering geometry, losses due to excitation of the adsorbates are observed in the 1000--4000-cm{sup {minus}1} range with little interference from the intense losses due to multiple surface optical phonons (Fuchs-Kliewer modes). Adsorption of water and methanol on ultrathin MgO(100) films on Mo(100) have been studied using this new approach.