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.
Bibliographical noteFunding Information:
This work has been supported by funding through the Deutsche Forschungsgemeinschaft (SFB 357 “Molekulare Mechanismen unimolekularer Prozesse”), the European Office for Aerospace Research (EOARD Grant No. FA 8655-03-1-3034) and the United States Air Force Office of Scientific Research (Project 2303 EP4). T.M.M. is under contract (FA8718-04-C0006) to the Institute for Scientific Research of Boston College.
- Collisional stabilization
- Pressure dependence
- Temperature dependence
- Unimolecular dissociation