Determination of cluster binding energy from evaporative lifetime and average kinetic energy release: Application to (CO2)+ n and Ar+ n clusters

The binding of a molecule within a cluster may be determined within the context of a simple statistical model from the measurements of cluster evaporative lifetime and average kinetic energy release. If the final product density of states is approximated by a Kassel distribution, the expression for lifetime can be inverted to give the binding energy. Stringent demands are placed upon the accurate determination of kinetic energy release, but only moderate demands are placed upon the accuracy of the lifetime or model parameters. The method is illustrated with positively charged carbon dioxide and argon clusters. Binding energy determinations agree with previous results that CO2 molecules are bound within the cluster with an average of 156±26 meV. The binding energy for Ar atoms decreases, from 150 meV within clusters of size 6, to 60 meV for clusters of size 22. The ±16% average error for the argon clusters represents mostly the uncertainty in the kinetic energy measurements.