Density Dependence of the Interrelation between Single Particle Motion and the Collective Dynamics in Liquid Sodium
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W.-C. Pilgrim
Abstract
Over a wide range of densities we have systematically investigated the single particle motion in liquid sodium in a series of quasielastic neutron scattering experiments. Our experimental results are in excellent agreement with predictions from molecular dynamics simulations and Mode-Coupling-Theory. The results allow to determine the microscopic mechanisms that control the single particle motion on atomic time- and length- scale and to relate these mechanisms to the values of the macroscopic diffusion coefficient at different densities. We can clearly distinguish three different density regimes where respectively three different coupling mechanisms between diffusive motion and collective modes dominate: At high density, particle diffusion is hindered and the main contribution to forward motion of a particle comes from a coupling to longitudinal density modes; however, at slightly reduced density the motion of the particle is coupled to transverse shear modes which cause an enhancement of the diffusive motion and hence of the diffusion coefficient. Only at very low density, the system gradually returns to particle dynamics which is controlled by binary collisions as predicted by simple hard sphere theories.
© 2003 Oldenbourg Wissenschaftsverlag GmbH
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Artikel in diesem Heft
- Phase Separation in Ultracold Boson–Fermion Mixtures under Confinement
- Can Alkali Metal Doped Zeolites be Metallic? – Microwave Conductivity of Rubidium Doped Zeolite Rho
- Density Dependence of the Interrelation between Single Particle Motion and the Collective Dynamics in Liquid Sodium
- Novel Ionization Mechanisms of Molecular Clusters in Ultraintense Laser Fields
- The Chemical Potential of Metal Atoms in Small Particles
- Analysis of Semiconductor Cluster Beam Polarization Taking Small Permanent Dipole Moments into Account
- Prediction of Reduced Falloff Curves for Recombination Reactions at Low Temperatures
- Static and Dynamic Structures of Expanded Fluid Mercury
- Book Reviews
