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.