Translational energy release: Experiment and theory. H2 elimination reactions of small gas phase ions, and correspondence to HH bond activation

All unimolecular decompositions are accompanied by a specific translational energy release. Translational energy release distributions can be precisely measured with a magnetic sector mass spectrometer. The experimental methods used for this purpose are described. The precise amount of translational energy released in the common centre of mass formed in a fragmentation reaction is a direct outcome of the detailed reaction dynamics of the system. It is described how recent development in reaction trajectory calculations with ab initio quantum chemical potential energy functions can be used to calculate translational energy release. The shape of a potential energy surface, and in particular the barrier height, are important for how much energy is released. In this review a much studied reaction type, H2 eliminations is reviewed. The reviewer has carefully examined the individual reactions in order to reveal the electronic factors that determine the shape of the potential energy profile. It turns out that frontier orbital theory provides a simple and solid theoretical framework.