title: Evidence of the existence of the low-density liquid phase in supercooled, confined water.
abstract: By confining water in a nanoporous structure so narrow that the liquid could not freeze, it is possible to study properties of this previously undescribed system well below its homogeneous nucleation temperature TH = 231 K. Using this trick, we were able to study, by means of a Fourier transform infrared spectroscopy, vibrational spectra (HOH bending and OH-stretching modes) of deeply supercooled water in the temperature range 183 < T < 273 K. We observed, upon decreasing temperature, the building up of a new population of hydrogen-bonded oscillators centered around 3,120 cm(-1), the contribution of which progressively dominates the spectra as one enters into the deeply supercooled regime. We determined that the fractional weight of this spectral component reaches 50% just at the temperature, TL approximately 225 K, where the confined water shows a fragile-to-strong dynamic cross-over phenomenon [Ito, K., Moynihan, C. T., Angell, C. A. (1999) Nature 398:492-494]. Furthermore, the fact that the corresponding OH stretching spectral peak position of the low-density-amorphous solid water occurs exactly at 3,120 cm(-1) [Sivakumar, T. C., Rice, S. A., Sceats, M. G. (1978) J. Chem. Phys. 69:3468-3476.] strongly suggests that these oscillators originate from existence of the low-density-liquid phase derived from the occurrence of the first-order liquid-liquid (LL) phase transition and the associated LL critical point in supercooled water proposed earlier by a computer molecular dynamics simulation [Poole, P. H., Sciortino, F., Essmann, U., Stanley, H. E. (1992) Nature 360:324-328].
authors.affiliation: Dipartimento di Fisica and Consorzio Nazionale Interuniversitario per le Scienze Fisiche della Materia, Universitá di Messina, C. da Papardo, S. ta Sperone 31, 98166 Messina, Italy. francesco.mallamace@unime.it
authors.forename: Francesco
authors.initials: F
authors.lastname: Mallamace
authors.forename: Matteo
authors.initials: M
authors.lastname: Broccio
authors.forename: Carmelo
authors.initials: C
authors.lastname: Corsaro
authors.forename: Antonio
authors.initials: A
authors.lastname: Faraone
authors.forename: Domenico
authors.initials: D
authors.lastname: Majolino
authors.forename: Valentina
authors.initials: V
authors.lastname: Venuti
authors.forename: Li
authors.initials: L
authors.lastname: Liu
authors.forename: Chung-Yuan
authors.initials: CY
authors.lastname: Mou
authors.forename: Sow-Hsin
authors.initials: SH
authors.lastname: Chen