Translational energy release: Experiment and theory. H-2 elimination reactions of small gas phase ions, and correspondence to H-H bond activation

All unimolecular decompositions are accompanied by a specific translational energy release. Translational energy release distributions can be precisel y measured with a magnetic sector mass spectrometer The experimental method s used for this purpose are described. The precise amount of translational energy released in the common centre of mass formed in a fragmentation reac tion is a direct outcome of the detailed reaction dynamics of the system. I t is described how recent development in reaction trajectory calculations w ith ab initio quantum chemical potential energy functions call be used to c alculate translational energy release. The shape of a potential energy surf ace, and in particular the barrier height, are important for how much energ y is released In this review a much studied reaction type, H-2 eliminations is reviewed. The reviewer has carefully examined the individual reactions in order to reveal the electronic factors that determine the shape of the p otential energy profile. It turns out that frontier orbital theory provides a simple and solid theoretical framework. (C) 1999 John Wiley & Sons, Inc. , Mass Spec Rev 18: 285-308, 1999.