crystallin
; water
; article
; diffusion coefficient
; dilution
; electron spin resonance
; low temperature
; priority journal
; thermodynamics
; viscosity
; water temperature
; Electron Spin Resonance Spectroscopy
; Molecular Probes
; Phase Transition
; Temperature
; Thermodynamics
; Viscosity
; Water
英文摘要:
Using electron spin resonance spectroscopy (ESR), we measure the rotational mobility of probe molecules highly diluted in deeply supercooled bulk water and negligibly constrained by the possible ice fraction. The mobility increases above the putative glass transition temperature of water, T g = 136 K, and smoothly connects to the thermodynamically stable region by traversing the so called "no man's land" (the range 150-235 K), where it is believed that the homogeneous nucleation of ice suppresses the liquid water. Two coexisting fractions of the probe molecules are evidenced. The 2 fractions exhibit different mobility and fragility; the slower one is thermally activated (low fragility) and is larger at low temperatures below a fragile-to-strong dynamic cross-over at ≈225 K. The reorientation of the probe molecules decouples from the viscosity below ≈225 K. The translational diffusion of water exhibits a corresponding decoupling at the same temperature [Chen S-H, et al. (2006) The violation of the Stokes-Einstein relation in supercooled water. Proc Natl Acad Sci USA 103:12974-12978]. The present findings are consistent with key issues concerning both the statics and the dynamics of supercooled water, namely the large structural fluctuations [Poole PH, Sciortino F, Essmann U, Stanley HE (1992) Phase behavior of metastable water. Nature 360:324-328] and the fragile-to-strong dynamic cross-over at ≈228 K [Ito K, Moynihan CT, Angell CA (1999) Thermodynamic determination of fragility in liquids and a fragile-tostrong liquid transition in water.
Banerjee, D., Department of Physics, Indian Institute of Science, Bangalore 560 012, India; Bhat, S.N., Department of Physics, Indian Institute of Science, Bangalore 560 012, India; Bhat, S.V., Department of Physics, Indian Institute of Science, Bangalore 560 012, India; Leporini, D., Dipartimento di Fisica Enrico Fermi, Università di Pisa, Largo B. Pontecorvo 3, I-56127 Pisa, Italy, SOFT-National Institute for the Physics of Matter-Consiglio Nazionale Delle Ricerche, Largo B. Pontecorvo 3, I-56127 Pisa, Italy
Recommended Citation:
Banerjee D.,Bhat S.N.,Bhat S.V.,et al. ESR evidence for 2 coexisting liquid phases in deeply supercooled bulk water[J]. Proceedings of the National Academy of Sciences of the United States of America,2009-01-01,106(28)