Superfluid response in OCS(H2)5 and OCS(D2)5

We analyze the structure and exchange permutation properties of complexes of a linear OCS molecule with molecular para-hydrogen, OCS(H-2)(5), and with ortho-deuterium, OCS(D-2)(5), using path integral calculations over a range of temperatures. These show that the H-2 (D-2) molecules constitute a single ring of localized density around the axis of the OCS molecule that has complete superfluid response to rotations around the molecular axis below T similar to 1 (0.6) K. This unusual combination of properties is shown to account for anomalies in recent spectroscopic measurements of these complexes.