From Visco-Elasticity Towards Thermal Relaxation: A Neutron Scattering Study ofDensity Fluctuations in Fluid Helium

摘要

The results of neutron scattering experiments on helium at temperatures between 4and 40 K and at number densities between 15 mm and 32 mm (exp -3) are presented. The Young algorithm proved to be useful in explaining static properties and worked for the microscopic dynamical behavior of helium. The halfwidths of the helium spectra are largely determined by the heat mode alone. The minimum value of the halfwidth compares very well with other simple model. The Enskog theory is successful in qualitatively predicting the heat mode and extended sound modes of the helium fluid. The relevance of the mode coupling theory for helium is shown.