1) Could you explain the significance of your article to the non-specialist?

The relaxation time of water is related to diffusion coefficient by the Stokes-Einstein equation, and to the viscosity by the Maxwell relation. Its high viscosity of 10^12 Poise at 136 K gives a temperature at which water has the consistency of a soft toffee, and can be deformed and shaped like a glass object. It also gives a upper temperature limit for storage of biological materials, and prevention of their spoilage by slow chemical reactions and by crystallization. Its relaxation time at 136 K has resolved the issue in disfavour of a much discussed inference that there are two states of liquid water, and that there is a liquid-liquid transition between them (Physics Today, 2003, June, p.40). 

Since the temperature range of existence of noncrystalline solids is important in a variety of disciplines, the method used here would be useful for characterizing a long-ignored, technologically useful class of high-enthalpy amorphous solids (J. Phys. Chem. B, 2003, 107, 9063). 

2) What has motivated you to conduct this work?

In several papers (Science, 2001, 294, 2335, Nature, 2004, 427, 717; Phys. Rev. Lett. 2004, 93, 215703) and a report (Physics Today, 2003, June, p.40), a comparison of the properties of amorphous solid water with unrelated substances had led to the conclusion that water remains a rigid solid up to a temperature of 165 K or 180 K. On the contrary, a number of earlier studies of water itself had demonstrated that it remains solid up to 136 K and rapidly crystallize to cubic ice on further heating into 150-160 K range. 

Our main motive was to clarify this issue by directly determining the relaxation time of water. 

3) Where do you see this work developing in the future?

Existence of viscous state of liquid water at such low temperatures and its crystallization to cubic ice gives us a limit up to which vitrified water can be heated without crystallizing to a bulkier phase of cubic ice. Its presence as frost on interstellar dust and its presence in comets is believed to have a role in the planetary activity. It is likely that the use of its viscosity can be made in cryopreservation technology. 

The novel method developed for determining the dielectric relaxation time would be used by us and others in future, by using computerized fast measurements of dielectric loss of thin films, for those viscous liquids that rapidly crystallize on heating. This would lead to an estimate of their viscosity and self diffusion coefficient, and a difference in the behaviour of glasses that have to be made by procedures other than the usual supercooling of liquids. 

The need for subtracting the background dielectric loss from the relaxational loss spectra before analysing the spectra (not discussed in this paper) requires that earlier analyses of the relaxational features of supercooled liquids be reconsidered. This may reveal that some of the relaxation features attributed to molecular processes may be an artifact of the background loss. 

4) Are there any particular challenges facing future research in this area?

Vitrification of biological fluids remains a challenge. Hyperquenching of ultrasonic nebulized liquid as micron size droplets, which has been used for vitrifying water, can be useful for that purpose as well as for vitrifying other substances of technical importance. There is a need for computer simulation of water's diffusion coefficient and for reconciling the viscosity of water of ca, 10^12 Poise with the conjectured states of two liquid waters, one of density 20% higher than the other.