Pressure dependence of elementary excitations in normal liquid helium-3

The neutron scattering function for liquid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ at 120 mK and pressures of 9, 0.5, 1, and 2 MPa has been determined for wave vectors in the range 3 ${\mathrm{nm}}^{\mathrm{-}1}$<Q<20 ${\mathrm{nm}}^{\mathrm{-}1}$. This represents the first experimental information on the density dependence of the zero-sound frequency and damping at finite wave vectors, and should serve as a useful test of theories on excitations in neutral Fermi liquids. The results are in qualitative agreement with extensions of the Landau Fermi-liquid thoery to finite wave vectors.