Ab initio/RRKM study of dissociation mechanism of C/sub 6/H/sub 6//sup 3+/: A view on Coulomb explosion of benzene

Density functional B3LYP/6-31G(d,p) calculations have been performed in order to investigate isomerization and dissociation of benzene trication, which are relevant to the Coulomb explosion mechanism of benzene. The results demonstrate that the benzene-like isomer of C/sub 6/H/sub 6//sup 3+/ can decompose through various pathways leading to distinct fragmentation products. RRKM calculations of rate constants for individual reaction steps assuming that the initial internal energy of the trication is 110 kcal/mol and solving kinetic master equations to obtain relative branching ratios show that H/sub 2/CCCH/sup 2+/ + H/sub 2/CCCH/sup +/ are the dominant products (81.5%) followed by C/sub 2/H/sub 3//sup +/ + C/sub 4/H/sub 3//sup 2+/ (13.2%) and the other minor products include CH/sub 3//sup +/ + H/sub 2/CCCCCH/sub 2//sup +/ (2.6%), C/sub 2/H/sub 4//sup 2+/ + H/sub 2/CCCC+ (1.1%), H/sub 2/CCCH/sup 2+/ + c-C/sub 3/H/sub 3//sup +/ (0.55%), C/sub 2/H/sub 2//sup +/ + c-C/sub 4/H/sub 4//sup 2+/ (0.49%), C/sub 2/H/sub 4//sup +/ + HCCCCH/sup 2+/ (0.20%), and CH/sub 2//sup +/ + H/sub 2/CCCHCCH/sup 2+/ (0.14%). The fragments are expected to be produced with high translational energy due to high Coulomb repulsion energy barriers. We consider implications of the C/sub 6/He/sub 6//sup 3+/ potential energy surface and decomposition mechanism to the Coulomb explosion of benzene.