Lang, Elmar and Lüdemann, Hans-Dietrich
Pressure and temperature dependence of the longitudinal proton relaxation times in supercooled water to -87°C and 2500 bar.
The Journal of Chemical Physics = J. Chem. Phys. 67 (7), pp. 718-723.
Other URL: http://link.aip.org/link/JCPSA6/v67/i2/p718/s1
The longitudinal proton relaxation times T1 of the water protons have been determined at 100.1 MHz in the temperature range from +20 to −87 °C and up to pressures of 2500 bar. At temperatures below +10 °C, the T1 isotherms exhibit a maximum at pressures between 1.5 and 2 kbar. While at +10 and 0 °C, T1 rises by ∼10% from its atmospheric pressure value, this maximum becomes much more pronounced between −20 and −45 °C. In this region application of pressure increases T1 by ∼100%. The isobars at 2 kbar and above run through a minimum at −76 °C, indicating that at this temperature ωτϑ?1 and that the proton relaxation rate cannot be described by the extreme narrowing condition below ∼−40 °C. The experimental T1 data and the τϑ values derived at 2 kbar could be treated by a sum of two exponentials. While the smaller activation energies derived from this fit of 3.44±0.17 kcal mole−1 is independent of pressure, the higher activation energy decreases from 13±0.65 kcal mole−1 at atmospheric pressure to 9.3±0.5 kcal mole−1 around 1 kbar and then remains independent of pressure to 2.5 kbar. The data are qualitatively discussed in terms of a random hydrogen‐bond network.
|Institutions:|| Biology, Preclinical Medicine > Institut für Biophysik und physikalische Biochemie > Prof. Dr. Elmar Lang|
|Keywords:||MOLECULAR MOTION, HYDROGEN BONDS, REORIENTATION, QUADRUPOLE INTERACTIONS, SUPERCOOLED LIQUIDS, LIQUIDS, WATER, SPIN−LATTICE RELAXATION, OXYGEN 17, HIGH PRESSURE, ISOTOPE EFFECTS, LATTICE VIBRATIONS, RELAXATION TIME, METASTABLE STATES, NMR SPECTRA|
|Subjects:||500 Science > 570 Life sciences|
|Created at the University of Regensburg:||Unknown|
|Deposited On:||22 Oct 2010 08:12|
|Last Modified:||22 Nov 2012 09:42|