Dissociation energies of gold clusters AuN+, N=7-27

Unimolecular decay rates and monomer-dimer branching ratios of gold clusters Au-N(+) (N=7-27) have been measured as a function of excitation energy in photodissociation experiments on size-selected clusters stored in a Penning trap. Part of the data set has previously been used to extract model-free values of dissociation energies [Vogel , Phys. Rev. Lett. 87, 013401 (2001)]. Other parts of the data set do not allow this analysis. We use these data to extract tentative dissociation energies, based on the systematics of deviations between an Arrhenius analysis and the model-free values. The observed systematics also allows an estimate of the true frequency factor which often is much higher than the Arrhenius value but in good agreement with the expected detailed balance value. The data are also reanalyzed including radiative cooling which may explain part of the discrepancy between model-free and Arrhenius dissociation-energy values.