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 parameters (oven temperature, inert gas pressure, inert gas type) are discussed in this report. Measurements of the mass-dependent velocity distributions of the clusters emitted by the source are presented and compared to a simple model calculation. The clusters are mass-analyzed with a time-of-flight mass spectrometer and detected by a multi-channel plate. The dependence of the detectability of large clusters on the acceleration voltage is investigated.