PRODUCING AND DETECTING VERY LARGE CLUSTERS

The cluster source we use, a low pressure, rare gas condensation cell, is capable of producing clusters containing more than 45 000 atoms or having masses exceeding 2 500000 amu. Details of this source and the dependence of the cluster size distribution on adjustable working para meters (oven temperature, inert gas pressure, inert gas type) are disc ussed in this report. Measurements of the mass-dependent velocity dist ributions of the clusters emitted by the source are presented and comp ared to a simple model calculation. The clusters are mass-analyzed wit h a time-of-flight mass spectrometer and detected by a multi-channel p late. The dependence of the detectability of large clusters on the acc eleration voltage is investigated.