On the free rotation of a molecule embedded in helium-4 clusters
  The fact, that $^4$He atoms on different concentric circular paths around the axis of a quantum vortex move with identically equal angular momentum, which represents an important aspect of superfluidity of He-II, has been used to discover a model which can explain the {\it typical nature} of experimentally observed $N$ (number of $^4He$ atoms) dependence of the rotational constant ($B$) of the rotor part of a cluster M:He$_N$. It reveals how exactly superfluidity is related to the said dependence of $B$ on $N$. We believe that this model, when used with simulation techniques, would render results that would agree closely with experiments. 
Yatendra S. Jain and Samrat Dey
cond-mat.other