Infrared Q-branch anomalies on cooling small OCS (pH2)n clusters from 0.38 K to 0.15 KS. Grebenev, B. G. Sartakov, J. P. Toennies and A. F. Vilesov
Max-Planck-Institut für Dynamik und Selbstorganisation - Bunsenstraße 10, 37073 Göttingen, Germany, EU
received 26 May 2008; accepted in final form 25 July 2008; published September 2008
published online 12 September 2008
Infrared spectra of OCS molecules with 8 n 16 attached para-hydrogen (pH2) molecules inside pure 4He droplets at 0.38 K and in mixed 4He/3He droplets at 0.15 K are compared with the same-sized oD2 clusters. In the pH2 clusters the Q-branch is observed at 0.38 K, except for n = 12, but disappears for n 11 on cooling to 0.15 K, whereas it is present in all the oD2 clusters. The high axial symmetry of the pH2 clusters at 0.15 K is consistent with the onset of microscopic superfluidity resulting predominantly from exchanges accompanying the hindered rotations of two or more rings.
67.90.+z - Other topics in quantum fluids and solids.
36.40.Mr - Spectroscopy and geometrical structure of clusters.
33.20.Ea - Infrared spectra.
© EPLA 2008