Electronic, rovibrational, and translational energy effects in ion-alkylbenzene charge-transfer reactions

Rate constants and branching fractions are reported for the reactions of NO +, Xe-2(+), O-2(+), Xe+(P-2(3/2)), and Kr+(P-2(3/2)) with toluene, ethylben zene, and n-propylbenzene. Ions with recombination energies ranging from 9. 26 eV (NO+) to 14.00 eV (Kr+) are studied at 300 K in a variable temperatur e-selected ion flow tube (VT-SIFT) yielding information regarding the role of electronic energy in these reactions. The reactions of NO+ and O-2(+) ha ve been studied between 300 and 500 K in the VT-SIFT and between 500 and 14 00 K in a high-temperature flowing afterglow (HTFA) apparatus to investigat e the role of rovibrational energy. The effect of translational energy in t hese reactions has been investigated with a guided-ion beam (GIB) apparatus using a high-temperature octopole (HT8P) operating under single collision conditions. In the GIB-HT8P experiments, the center-of-mass collision energ y was varied from ca. 0.1 to 7 eV for reactions of NO+ and O-2(+). and the target gas temperature was varied between 300 and 800 K. All reactions are Found to proceed near the capture rate at all temperatures studied. The rea ctions proceed primarily by nondissociative and dissociative charge transfe r except for the reaction involving NO+, where the dissociation products ob served in the HTFA experiments at high temperature are attributed to therma l decomposition of the charge-transfer product ions. Generally, electronic and vibrational energy are both very effective in promoting dissociation wh ile translational energy is found to be less effective.