A Superfluid Hydrodynamic Model for the Enhanced Moments of Inertia of Molecules in Liquid

We present a superfluid hydrodynamic model for the increase in moment of inertia, ∆I, of molecules rotating in liquid He. The static inhomogeneous He density around each molecule (calculated using the Orsay–Paris liquid He density functional) is assumed to adiabatically follow the rotation of the molecule. We find that the ∆I values created by the viscousless and irrotational flow are in good agreement with the observed increases for several molecules [OCS, (HCN)2, HCCCN, and HCCCH3]. For HCN and HCCH, our model substantially overestimates ∆I. This is likely to result from a (partial) breakdown of the adiabatic following approximation. 67.40.Yv,67.40.Hf,67.40.Bz,33.20.Sn Typeset using REVTEX