Roton Interactions in Superfluid Helium

The Feynman-Cohen model for rotons is shown to lead to an attractive interaction for two rotons at large distances and a repulsive interaction at short distances. The attractive interaction leads to a bound state of $d$ symmetry in agreement with recent light-scattering data. The scattering of rotons arises from the repulsive interaction, and the experimental data on roton-roton scattering lead to an estimate of the range of repulsive interaction.