The dissociative recombination rate coefficient for NO+ has been measured at 300 K using a flowing afterglow Langmuir probe-mass spectrometer apparatus. A value of (4±1) × 10-7 cm3 s-1 has been found for ground electronic and vibrational state ions produced from the parent NO gas. Ions produced from a N2:O2 mixture which are in a wide range of vibrationally excited states display a smaller recombination rate of (1.6±0.5) × 10-7 cm3 s-1.

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Absolute rate coefficients for electron attachment to methyl iodide have been measured under thermal equilibrium conditions between 48 and 300 K. The temperature dependence of our results at low temperatures is found to differ from recent results taken using the laser photoionization attachment (LPA) method. Tentative explanations including possible effects due to electron attachment to clusters are suggested.

The recombination of electrons with cyclic ions produced via ion-molecule reactions between atomic precursor ions and methyl-substituted benzene ring compounds ͑toluene, ortho-, and para-xylene and mesitylene͒ has been studied at 300 K using a flowing afterglow Langmuir probe-mass spectrometer apparatus. Differing amounts of energy can be deposited into the daughter ions depending upon which atomic precursor is used. It has been found that same-mass daughter ions formed from different precursors displayed different recombination rate coefficients indicating that different isomeric forms were reacting. In particular, the benzene ring of the toluene cation expands to a seven-membered ring following isomerization to the cycloheptatriene form. H atom abstraction allows two different isomeric daughter ions to be formed that do not interconvert and that display different recombination rates. A similar behavior was observed for the xylenes and for mesitylene. All recombination rates lie in the range from 10 Ϫ7 to 10 Ϫ6 cm 3 s Ϫ1 and display no apparent relation with size nor with the aromaticity of the ions.