Mean kinetic energy and fnal state effects in liquid hydrogens from inelastic neutron scattering

We have measured, using the TOSCA spectrometer at ISIS, the neutron scattering spectrum of liquid para-hydrogen (T=19.3 K and n=25.4 nm-3 ) and liquid ortho-deuterium (T=21.3 K and n=25.2 nm-3). From the high-energy region of the spectrum, namely 40 meV<1 eV, where the incoherent approximation for the center-of-mass motion applies, we have been able to extract the translational mean kinetic energy,which, as expected, turns out to be rather different from the classical values.However, significant deviations from the impulse approximation havebeen detected and the inclusion of some correction terms (accounting forthe so-called final state effects) had to be accomplished in order to accuratelydescribe the experimental spectra. The comparison of the presentmean kinetic energy values with the available experimental and simulateddata in the literature is quite good and confirms the excellent performancesof TOSCA in the spectroscopic analysis of the condensed phases of liquidhydrogens.