title: Observation of fractional Stokes-Einstein behavior in the simplest hydrogen-bonded liquid.
abstract: Quasielastic neutron scattering has been used to investigate the single-particle dynamics of hydrogen fluoride across its entire liquid range at ambient pressure. For T>230 K, translational diffusion obeys the celebrated Stokes-Einstein relation, in agreement with nuclear magnetic resonance studies. At lower temperatures, we find significant deviations from the above behavior in the form of a power law with exponent xi=-0.71+/-0.05. More striking than the above is a complete breakdown of the Debye-Stokes-Einstein relation for rotational diffusion. Our findings provide the first experimental verification of fractional Stokes-Einstein behavior in a hydrogen-bonded liquid, in agreement with recent computer simulations [S. R. Becker, Phys. Rev. Lett. 97, 055901 (2006)10.1103/PhysRevLett.97.055901].
authors.affiliation: ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX, United Kingdom. F.Fernandez-Alonso@rl.ac.uk
authors.forename: F
authors.initials: F
authors.lastname: Fernandez-Alonso
authors.forename: F J
authors.initials: FJ
authors.lastname: Bermejo
authors.forename: S E
authors.initials: SE
authors.lastname: McLain
authors.forename: J F C
authors.initials: JF
authors.lastname: Turner
authors.forename: J J
authors.initials: JJ
authors.lastname: Molaison
authors.forename: K W
authors.initials: KW
authors.lastname: Herwig
mesh_terms: D055598:Chemical Phenomena; D002627:Chemistry, Physical; D004058:Diffusion; D004735:Energy Transfer; D006860:Hydrogen Bonding; D021241:Spectrometry, Mass, Electrospray Ionization; D013696:Temperature