Volume 91, Number 6, September 2010
|Number of page(s)||6|
|Section||Condensed Matter: Structural, Mechanical and Thermal Properties|
|Published online||11 October 2010|
Localized diffusive motion on two different time scales in solid alkane nanoparticles
Department of Physics and Astronomy and University of Missouri Research Reactor, University of Missouri Columbia, MO 65211, USA
2 Spallation Neutron Source, Oak Ridge National Laboratory - Oak Ridge, TN 37831, USA
3 Center for Neutron Research, National Institute of Standards and Technology - Gaithersburg, MD 20899-6102, USA
4 Department of Materials Science and Engineering, University of Maryland - College Park, MD 20742, USA
5 Facultad de Física, Pontificia Universidad Católica de Chile - Santiago, Chile
Accepted: 3 September 2010
High-energy-resolution quasielastic neutron scattering on three complementary spectrometers has been used to investigate molecular diffusive motion in solid nano- to bulk-sized particles of the alkane n-C32H66. The crystalline-to-plastic and plastic-to-fluid phase transition temperatures are observed to decrease as the particle size decreases. In all samples, localized molecular diffusive motion in the plastic phase occurs on two different time scales: a “fast” motion corresponding to uniaxial rotation about the long molecular axis; and a “slow” motion attributed to conformational changes of the molecule. Contrary to the conventional interpretation in bulk alkanes, the fast uniaxial rotation begins in the low-temperature crystalline phase.
PACS: 66.30.hp – Molecular crystals / 78.70.Nx – Neutron inelastic scattering / 33.15.Mt – Rotation, vibration, and vibration-rotation constants
© EPLA, 2010
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