Dissociation dynamics of molecular ions in very high charge states

Abstract

An attempt is made to relate the dissociation dynamics of highly charged molecular ions (possessing charges in excess of 2+) to molecular structure. High-level, ab initio configuration-interaction calculations are carried out of the potential energy functions of N:+, for q = 2-12, and predictions are made of the values of the kinetic energies released upon unimolecular dissociation of such ions. The calculated values are found to be significantly lower than those expected from simple Coulombic considerations. Electron density distributions of highly charged molecules are calculated and, on the basis of these, a long-lived state of a diatomic tri-cation, CS3+, is predicted. Mass spectrometric evidence is produced which confirms these predictions.

Chapter 9. Physical-chemical aspects of mass spectrometry

“…~~ It is capable of measuring lifetimes of specific quantum states of species such as CO", SH2+ and N, with up to 12 charges. 85 The kinetic energy release for CS3+ is lower than a simple Coulomb explosion model would predict. The kinetic energy release is, however, in agreement with the structure and charge distribution of a long-lived excited state obtained from high level ab initio calculations, including configuration interaction.…”

Coulombic and non-Coulombic fragmentation of highly charged benzene

“…It is against the backdrop of such observations that there has been continuing discussion in the literature on non-Coulombic pathways to the dissociation of molecules in very high charge states. Much of the work on studies of dissociation pathways that do not follow the expectations of Coulomb's law has also relied on high-level, ab initio, molecular orbital methods to calculate potential energy functions of various electronic states of molecular species in charge states from 2+ to fully stripped (Mathur et al 1993, 1995, Safvan and Mathur 1994, Safvan et al 1993. The parameter of utility in such computations is the energy difference between the vertically accessible (Franck-Condon) parts of such potential energy surfaces and various dissociation limits.…”