Product energy and angular momentum partitioning in the unimolecular dissociation of aluminum clusters

A previous classical trajectory simulation showed that the unimolecular decompositions of Al-6 and A(13) are intrinsically RRKM. In the work presented here, this study is further analyzed to determine the Al-5 + Al and Al-12 + Al product energy distributions, which are compared with the predictions of statistical theories. Orbiting transition state/phase space theory (OTS/PST) gives distributions in excellent agreement with the trajectory results. Assuming a loose, product-like transition state gives a lower average product translational energy, <E-t> than what is found with the orbiting transition state. Including anharmonicity, in the calculation of the product vibrational density of states, increases the energy partitioned to product vibration. The Engelking model for cluster decomposition overestimates <E-t>. One Klots model gives an inaccurate <E-t>, but a second model more firmly rooted in phase space theory performs quite well. The Engelking model, for deducing the cluster dissociation energy from the measured <E-t>, does not give accurate results for Al-6 and Al-13 dissociation.