Regensburg 2013 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe
DY: Fachverband Dynamik und Statistische Physik
DY 10: Glasses (joint session DY/DF/CPP)
DY 10.3: Vortrag
Dienstag, 12. März 2013, 10:00–10:15, H46
Deuteron-NMR investigation on the dynamics of supercooled, confined water — •Matthias Sattig and Michael Vogel — TU Darmstadt, Institut für Festkörperphysik
The dynamical behaviour of water in the regime of the supercooled liquid is a topic of large interest. In particular, the existence of a fragile-to-strong transition (FST) at T=225K related to the transition between two distinct phases of liquid water is controversially discussed [1]. Due to crystallization the temperature range proposed for the FST is hardly accessible in bulk water. Therefore, we confine heavy water to narrow pores in the mesoporous sillicate MCM-41. This suppresses the freezing of a substantial fraction of water, enabling direct investigation of the interesting temperatures. Deuteron-NMR methods are utilised to determain the rotational correlation times τ of water on time scales from ns up to s. The spin-lattice-relaxation time T1 exhibits a typical minimum at about T=230K. Above this minimum the correlation times follow a Vogel-Fulcher-Tammann law. Below the minimum, two relaxation processes could be observed. The low-temperature processes show a different temperature dependence, where the curves τ(T) of all processes intersect at about T=230K. A comparison with literature data [2] from neutron scattering and dielectric spectroscopy gives rise to the idea that the observed crossover is due to this intersection of processes rather than to a FST. To test this idea studies on water confined to MCM-41 with different pore sizes and fillings are in progress.
[1] Mishima; Nature, Vol. 396, 329(1998) [2] Hedström; EPJST 141, 53(2007)