Collision statistics of clusters: from Poisson model to Poisson mixtures

Clusters traverse a gas and collide with gas particles.The gas particles are absorbed, and the clusters become hosts. Ifthe clusters are size-selected, the number of guests will be Poissondistributed. We review this by showcasing four laboratory proceduresthat all rely on the validity of the Poisson model. The effects of astatistical distribution of the clusters' sizes in a beam ofclusters are discussed. We derive the average collision rates.Additionally, we present Poisson mixture models that also involvestandard deviations. We derive the collision statistics for commonsize distributions of hosts and also for some generalizationsthereof. The models can be applied to large noble gas clusterstraversing doping gas. While outlining how to fit a generalizedPoisson to the statistics, we still find even these Poisson modelsto be often insufficient.