Vibrational spectroscopy of sulfur hexafluoride attached to helium clusters

We have built an apparatus capable of attaching a molecule to a liquid-helium cluster and obtaining its infrared spectrum. Clusters made of a few thousand atoms and containing an SF₆ molecule show two absorptions located at 945. 8 and 946. 1 cm^-1 which indicate that the guest molecule is located near the surface of the cluster. If the cluster contains two SF₆ molecules, the spectrum obtained is that of a slightly perturbed SF₆ dimer.