MOMENTUM DISTRIBUTION OF HE-4 ACROSS THE MELTING TRANSITION

We have measured the momentum distribution of liquid and solid He-4 by means of neutron Compton scattering, using the high energy neutrons o f the pulsed neutron source ISIS. The experiment has been carried out on the isotherm at 4.35 K in the pressure interval between 35 and 500 bars. We have obtained the value of the kinetic energy, as a function of density, at four thermodynamic points in the liquid phase and eleve n thermodynamic points in the solid phase. The data of the present exp eriment extend considerably the previous density range and reveal a ga p in the density behavior crossing the melting transition.