Potential energy surfaces in Coulomb explosion of polyatomic molecules: Benzene and cyclohexane trications and acetylene dication

We report density functional and ab initio calculations of potential energy surfaces (PES) for benzene and cyclohexane trications relevant to the Coulomb explosion mechanisms of C6H6 and C6H12. Numerous isomerization and dissociation mechanisms on these PES have been considered, and the products most favorable thermodynamically and kinetically have been predicted. We also demonstrate applications of RRKM theory to the calculation of product branching ratios in decomposition of multiply charged cations. Significant common features of PES related to Coulomb explosion experiments on hydrocarbon molecules have been described. Calculations along minimal energy reaction paths for some representative isomerization and dissociation channels have been carried out in the presence of strong external electric field for C6H and C2H and the influence of the field on molecular orientation and PES have been analyzed. The results show that proton mobility in nonaromatic hydrocarbon cations is high due to nearly zero barriers for the H+ migrations.