COLD METAL-CLUSTERS - HELIUM DROPLETS AS A NANOSCALE CRYOSTAT

In this Letter we study the formation of metal clusters of silver, ind ium, and europium embedded in helium droplets and present spectroscopi c (UV) evidence that, contrary to common belief, metal atoms can be st able inside helium droplets. Our method provides a beam of metal clust ers up to 2000 amu with a precisely known temperature of 0.37 K, 2 ord ers of magnitude lower than previously achieved for free metal cluster s. This dramatic decrease in temperature is important for high resolut ion spectroscopic experiments and opens the door to beam studies of su perconducting metal clusters.