A new determination of the roton energy in superfluid liquid helium

Abstract
The energies of excitations in the region of the minimum in the dispersion curve for superfluid liquid 4He have been determined at SVP and T=0.75K using neutron inelastic scattering. The value of Delta /k is 8.618+or-0.009K. Comparison with recent Raman-scattering measurements gives a value of the roton-roton binding energy of 0.027+or-0.04K at Q=0.