High resolution Raman study of the two-roton bound state

Abstract

A high resolution study has been made of the two-roton Raman scattering from liquid 4He at T=0.6K and SVP. This experiment shows conclusively that roton-roton interactions are necessary to explain the spectrum. From the shape of the two-roton peak the two-roton binding energy is estimated to be 0.22+or-0.07K. An intrinsic zero temperature linewidth of the pair equal to 0.11+or-0.01K has been found.