Evidence of two distinct local structures of water from ambient to supercooled conditions

Year: 2013

Authors: Taschin A., Bartolini P., Eramo R., Righini R., Torre R.

Autors Affiliation: European Lab for Non-Linear Spectroscopy (LENS), Univ. di Firenze, via N. Carrara 1, Sesto Fiorentino, I-50019 Firenze, Italy; Istituto Nazionale Ottica, CNR, Largo Fermi 6, I-50125 Firenze, Italy; Dip. di Chimica, Univ. di Firenze, via Della Lastruccia 13, Sesto Fiorentino, I-50019 Firenze, Italy; Dip. di Fisica e Astronomia, Univ. di Firenze, via G. Sansone 1, Sesto Fiorentino, I-50019 Firenze, Italy

Abstract: The liquid and supercooled states of water show a series of anomalies whose nature is debated. A key role is attributed to the formation of structural aggregates induced by critical phenomena occurring deep in the supercooled region; the nature of the water anomalies and of the hidden critical processes remains elusive. Here we report a time-resolved optical Kerr effect investigation of the vibrational dynamics and relaxation processes in supercooled bulk water. The experiment measures the water intermolecular vibrations and the structural relaxation process in an extended temperature range, and with unprecedented data quality. A mode-coupling analysis of the experimental data enables to characterize the intermolecular vibrational modes and their interplay with the structural relaxation process. The results bring evidence of the coexistence of two local configurations, which are interpreted as high-density and low-density water forms, with an increasing weight of the latter at low temperatures.


Volume: 4      Pages from: 2401  to: 2401

More Information: The research has been performed at LENS. This work was supported by the REGIONE TOSCANA POR-CRO-FSE 2007-2013 by the EC COST Action MP0902-COINAPO and by the PRIN 2010/2011N.2010ERFKXL. We thank A. Marcelli for helpful discussion. We acknowledge M. De Pas, A. Montori and M. Giuntini for providing their continuous assistance in the set-up of the electronics. We also thank R. Ballerini and A. Hajeb for the accurate mechanical realizations.
KeyWords: Cooling water; Water, cooling; Density; Low temperature; Molecular analysis; Vibration, ambient air; Article; Hydrodynamics; Spectroscopy; Temperature; Vibration; Water sampling; Water structure; Femtosecond optical Kerr; Mode-coupling theory; Frequency Raman-spectroscopy; Time-resolved spectroscopy; Glass-forming liquid
DOI: 10.1038/ncomms3401

Citations: 147
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