Momentum distributions in quantum and nearly classical liquids.

Using high-precision neutron-scattering data, we show that the momentum distribution, n(k), in normal He differs significantly from the classical, Maxwell-Boltzmann distribution while n(k) in liquid neon is Maxwellian. Final-state contributions to the scattering function are also determined from the data. In helium these are most conveniently represented as a final-state broadening function and in neon as additive corrections to the impulse approximation.