Ground state proton dynamics in stable phases of water

The proton momentum distribution, n(p), and the mean kinetic energy, 〈 E K 〉 , of water are intimately connected to the nuclear quantum effects associated to the equilibrium ground state of water. The physical quantities have been studied via Deep Inelastic Neutron Scattering experiments performed at the ISIS neutron source, in the temperature range 300 K ⩽ T ⩽ 673 K . The Compton lineshape analysis provides values of the proton mean kinetic energy 〈 E K 〉 which are constantly in excess of the classical values as T increases. From the analysis of n(p) the effective proton potentials are derived. The equilibrium dynamics of H-bonded protons is discussed.