Collisional stabilization of highly vibrationally excited o-, m- and p-xylene ions (C₈H₁₀⁺) from 300-900 K and 1-250 Torr

Branching ratios for the reactions of O₂⁺ with all three xylene isomers have been measured as a function of temperature over a wide range (300-900 K) at a fixed number density (1.45 × 10¹⁶ molecule cm^-3 of helium) and for m-xylene over an extended buffer gas pressure (50-250 Torr of nitrogen) and temperature (473-623 K) range. Rate constants measured under selected conditions indicate that the reactions proceed at the collisional rate. Two main products were observed in each reaction: the stabilized parent ion, C₈H₁₀⁺ (S) and a dissociative charge transfer product, C₇H₇⁺ (D). The ratio of S/D was found to vary significantly with both temperature and pressure. At high pressure very little dissociation occurred. Results of statistical modeling similar to that used in our studies of n-alkylbenzenes represent the data well.