Rubidium ion hydration in ambient and supercritical water

Journal Article · Thu Aug 01 04:00:00 EDT 1996 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.472089· OSTI ID:288748

Fulton, J L; Pfund, D M; Wallen, S L ^[1]; Newville, M; Stern, E A; Ma, Y ^[2]

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1. Material and Chemical Sciences Department, Pacific Northwest National Laboratory, Richland, Washington 99352 (United States)
2. Department of Physics, Box 351560, University of Washington, Seattle, Washington 98195 (United States)

X-ray absorption fine structure (XAFS) measurements and analyses are presented for Rb{sup +} in supercritical water solutions. The structure of the first hydration shell at ambient conditions is compared to that in the supercritical region at a temperature of 424{degree}C and pressures from 382 to 633 bar. For all reported studies, RbBr at a concentration of 0.5 molal was used. XAFS results show that there is a well-defined hydration shell around the cation even at 424{degree}C but at these high temperatures the extent of hydration of the Rb cation is reduced by about 40{percent}. A slight contraction of this first shell distance by about 0.10 A is also observed under supercritical conditions. The reduction in the number of water-ion bonds is analogous to the reduction in the amount of water{endash}water hydrogen bonding that has been observed by others under supercritical conditions. The reduction in waters-of-hydration under supercritical conditions may also be in part due to formation of contact-ion pairs. {copyright} {ital 1996 American Institute of Physics.}

• Research Organization: Pacific Northwest National Laboratory
• DOE Contract Number: AC06-76RL01830
• OSTI ID: 288748
• Journal Information: Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 6 Vol. 105; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

40 CHEMISTRY
AQUEOUS SOLUTIONS
ELECTRONIC STRUCTURE
FINE STRUCTURE
HYDRATION
HYDROGEN BONDS
RUBIDIUM IONS
SUPERCRITICAL STATE
X-RAY ABSORPTION ANALYSIS
X-RAY SPECTROSCOPY