The ion pair production has been studied for the gases N2and O2, excited by 400 eV electrons. For the detection of the ions, a channel electron multiplier and a quadrupole mass spectrometer were operated in coincidence. The ion energy was measured by the timehyphen;ofhyphen;flight method. We found groups of ion pairs with kinetic energies of 7.8, 10.6, and 15.0 eV for nitrogen and of 7.6, 10.6, and 16.8 eV for oxygen. From our data, we conclude that about half of all ions with kinetic energies higher than 2 eV originate from ion pair production. The process N3+2rarr;N2++N+was observed. The N+energy distribution starting at about 8 eV passes through a broad maximum at about 16 eV.
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