Calculation of differential and total neutron cross sections in superfluid helium 4 / Berechnung von differentiellen und totalen Neutronenwirkungsquerschnitten in supraflüssigem Helium 4.

Abstract

A calculation of the differential neutron cross sections per unit intervals of energy and solid angle as well as the total neutron scattering cross sections in superfluid helium 4 at a temperature of about 1 K and saturated vapor pressure is presented. One-phonon and multiphonon down-scattering processes are considered. An equation for the cross section per unit interval of energy is derived and applied to neutrons with initial energies of 1.02x10 -3 and 2.23x100 -3 eV. Around these initial neutron energies, the neutrons are scattered down to less than 10 -5 eV by one-phonon and multiphonon transitions. Upscattering is neglected.