It is shown that the drastic distinction in the rotational structure of molecules in the He4 and He3 liquids observed in [1] is due to the difference in the spectral density of excitations regardless of the hydrodynamic properties. The large width of rotational levels in the He3 is determined by particle-hole excitations whereas the small density of phonon excitations results only in the small broadening of levels in the He4.
@article{arxiv.cond-mat/9906220,
title = {The Rotational Structure of Molecules In the Quantum He4 and He3 Liquids},
author = {V. S. Babichenko and Yu. Kagan},
journal= {arXiv preprint arXiv:cond-mat/9906220},
year = {2009}
}