The growth of small tellurium clusters in helium and the influence of a met
al impurity (dysprosium atoms) on the cluster size distribution are investi
gated in a double laser vaporization source. A model describing the role of
the carrier gas as collision partner is presented, emphasizing the crucial
influence of the gas pressure on cluster formation. Changes in cluster rea
ctivity due to dysprosium addition are discussed in terms of ionic structur
es Dy3+(Te-N)(3-) containing a radical electron.