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Free electron attachment to the three different isomers of mononitrotoluene molecules in the gas phase is studied using a crossed electron-molecule beams technique. In contrast to previous studies for a large number of negative ions, the presently measured relative cross section curves are recorded with an electron energy resolution of better than 100 meV. For several product anions including the nitro anion NO(2)-, remarkable differences for the three isomers are observed. In almost all fragment anion efficiency curves, the 2-nitrotoluene exhibits pronounced differences from the two other isomers. In contrast, 3- and 4-nitrotoluene disagree only slightly in a few fragment anions from each other.

In this paper we report the detection and mass analysis of negative ions formed in a negative corona discharge using both dry and ‘wet’ air at pressures between 5 and 27 kPa. The yield of individual ions is strongly affected by trace concentrations of ozone, nitrogen oxides and water vapour. In dry air the dominant ion is CO3−. In presence of water this is converted very efficiently to cluster ions containing one and more water molecules. If ozone and nitrogen oxides are added, or are produced in discharge in sufficient concentrations, NO3− ions and NO3− hydrated clusters are formed. Ozone concentrations greater than 25 ppm are sufficient to completely suppress the appearance of O2− ions and its clusters both in dry and wet air. Such observations allow a comprehensive review of the physical and chemical processes within the discharge. [Copyright &y& Elsevier]

Abstract: Using atmospheric pressure nitrogen corona discharge electron attachment ion mobility spectrometry (APNCD-EA-IMS), the rate constants of electron attachment to 1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, 1,2,4-trichlorobenzene and α,α,α-trichlorotoluene have been determined at ambient temperature as a function of the average electron energy in the range from 0.35 to 0.65eV based on the experimental measurements of the negative ion mobility spectra. The rate constants are in the order of magnitude of ∼10−9 cm3 molecule−1 s−1. The ability of the dichlorobenzene isomers to capture the electrons has been found to decrease following the order of 1,2-chlorobenzene, 1,3-chlorobenzene and 1,4-chlorobenzene, which is different from previously reported results in the literature. For electron attachment to 1,2,4-trichlorobenzene and α,α,α-trichlorotoluene, the experimental measurements show that α,α,α-trichlorotoluene has a higher rate constant than 1,2,4-trichlorobenzene. [Copyright &y& Elsevier]