Raman scattering signatures of the unusual vibronic interaction of molecules in liquid helium-3

Light scattering in quantum liquid helium-3 may involve a unique mechanism - the creation and annihilation of atom excitations across the Fermi level. The density of states of particle-hole excitations in the low-energy limit is strongly enhanced as compared to that of collective excitations of phonons in helium-3. This makes possible to directly observe Fermi excitations in the resonant Raman scattering (RRS) by 3He droplets doped by impurity molecules. The RRS spectra essentially depend on the excitation frequency. In case of excitation in the anti-Stokes side of absorption the first order RRS is directly determined by the particle-hole excitations in the vicinity of the impurity molecule and the contribution of phonons mainly given by the localized spherical vibration. The calculations are made for a 3He droplet doped by a glyoxal molecule.