  X-ray scattering experiments on bulk liquid He-3 have indicated the
possibility of the existence of a sharp collective mode at large momentum
transfers. We address this issue within a manifestly microscopic theory of
excitations in a Fermi fluid that can be understood as proper generalization of
the time-honored theory of Jackson, Feenberg, and Campbell of excitations in
He-4. We show that both neutron and X-ray data can be well explained within a
theory where the high momentum excitations lie in fact inside the particle-hole
continuum. "Pair fluctuations" contribute a sharpening of the mode compared to
the random phase approximation (RPA). When the theoretical results are
convoluted with the experimental resolution, the agreement between theory and
X-ray data is quite good.
