Fernandez-Alonso F, Bermejo F J, McLain S E, Turner J F C, Molaison J J, Herwig K W
ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX, United Kingdom.
Phys Rev Lett. 2007 Feb 16;98(7):077801. doi: 10.1103/PhysRevLett.98.077801. Epub 2007 Feb 14.
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].
准弹性中子散射已被用于研究常压下氟化氢在其整个液相范围内的单粒子动力学。对于T>230 K，平动扩散遵循著名的斯托克斯-爱因斯坦关系，这与核磁共振研究结果一致。在较低温度下，我们发现上述行为存在显著偏差，表现为指数为xi=-0.71±0.05的幂律形式。比上述情况更引人注目的是，德拜-斯托克斯-爱因斯坦转动扩散关系完全失效。我们的研究结果首次通过实验验证了氢键液体中的分数斯托克斯-爱因斯坦行为，这与最近的计算机模拟结果一致 [S. R. 贝克尔，《物理评论快报》97, 055901 (2006)10.1103/PhysRevLett.97.055901]。
