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.
@article{arxiv.1009.0634,
title = {Theoretical analysis of neutron and X-ray scattering data on He-3},
author = {Eckhard Krotscheck and Martin Panholzer},
journal= {arXiv preprint arXiv:1009.0634},
year = {2015}
}