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The Dynamic Response Function chi(T)(Q,t) of Confined Supercooled Water and its Relation to the Dynamic Crossover Phenomenon

Research Area: Uncategorized Year: 2010
Type of Publication: Article
Authors:
Journal: ZEITSCHRIFT FUR PHYSIKALISCHE CHEMIE-INTERNATIONAL JOURNAL OF RESEARCH IN PHYSICAL CHEMISTRY & CHEMICAL PHYSICS Volume: 224
Number: 1-2 Pages: 109-131
ISSN: 0942-9352
Abstract:
We have made a series of Quasi-Elastic Neutron Scattering (QENS) studies of supercooled water confined in 3-D and 1-D geometries, specifically, interstitial water in aged cement paste (3-D)and water confined in MCM-41-S and Double Wall Nano Tube DWNT (1-D). In addition, we also include the cases of hydration water oil protein surface and other biopolymer surfaces (Pseudo 2-D). By analyzing the QENS spectra using Relaxing Cage Model (RCM), we are able to extract accurately the self-intermediate scattering function of hydrogen atoms F(H)(Q,t), at low-Q as a function of temperature T, showing an a-relaxation process at long time. We can then construct the Dynamic Response Function chi(T)(Q,t) = -dF(H)(Q,t)/dT. chi(T)(Q,t) as a function of t at constant Q shows a single peak at the characteristic alpha-relaxation time , the amplitude of which grows as we approach the dynamic crossover temperature T(L) observed before in each of these geometries. However, the peak height of chi(T)(Q,t) decreases after passing the crossover temperature T(L). We make all argument to relate the occurrence of the extremum of the peak height in chi(T) to the existence of the dynamic crossover temperature in each of these cases.
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