title: Supercooled water escaping from metastability.
abstract: The return of supercooled water to a stable equilibrium condition is an irreversible process which, in large enough samples, takes place adiabatically. We investigated this phenomenon in water by fast imaging techniques. As water freezes, large energy and density fluctuations promote the spatial coexistence of solid and liquid phases at different temperatures. Upon synchronously monitoring the time evolution of the local temperature, we observed a sharp dynamic transition between a fast and a slow decay regime at about 266.6 K. We construe the observed phenomenon in terms of the temperature dependence of heat transfers from solid and liquid volumes already at their bulk coexistence temperature towards adjacent still supercooled liquid regions. These findings can be justified by observing that convective motions induced by thermal gradients in a supercooled liquid near coexistence are rapidly suppressed as the nucleated solid fraction overcomes, at low enough temperatures, a characteristic percolation threshold.
authors.affiliation: CNR-IPCF, Viale Ferdinando Stagno d'Alcontres 37, 98158 Messina, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Aliotta
authors.affiliation: Università degli Studi di Messina, Dipartimento di Fisica e di Scienze della Terra, Contrada Papardo, 98166 Messina, Italy.
authors.forename: Paolo V
authors.initials: PV
authors.lastname: Giaquinta
authors.affiliation: CNR-IPCF, Viale Ferdinando Stagno d'Alcontres 37, 98158 Messina, Italy.
authors.forename: Rosina C
authors.initials: RC
authors.lastname: Ponterio
authors.affiliation: 1] CNR-IPCF, Viale Ferdinando Stagno d'Alcontres 37, 98158 Messina, Italy [2] Università degli Studi di Messina, Dipartimento di Fisica e di Scienze della Terra, Contrada Papardo, 98166 Messina, Italy.
authors.forename: Santi
authors.initials: S
authors.lastname: Prestipino
authors.affiliation: CNR-IPCF, Viale Ferdinando Stagno d'Alcontres 37, 98158 Messina, Italy.
authors.forename: Franz
authors.initials: F
authors.lastname: Saija
authors.affiliation: CNR-IPCF, Viale Ferdinando Stagno d'Alcontres 37, 98158 Messina, Italy.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Salvato
authors.affiliation: CNR-IPCF, Viale Ferdinando Stagno d'Alcontres 37, 98158 Messina, Italy.
authors.forename: Cirino
authors.initials: C
authors.lastname: Vasi