First composition measurements of positive chemiions in aircraft jet engine exhaust: detection of numerous ion species containing organic compounds

First mass-spectrometric composition measurements with high mass resolution of positive chemiions (CI) were made in the exhaust of an aircraft jet engine at ground level. The ion mass spectrometer used was a quadrupole ion-trap mass spectrometer with a high mass resolution and a large mass range (up to 2000 atomic mass units (amu)). The mass spectrum which extends from 150 to 2000 amu is very crowded showing a mass peak at nearly every mass number m. CI with odd m are much more abundant than CI with even m. Groups of mass peaks separated by 14 amu are clearly noticeable indicating CH2 groups. Probably many of the observed positive CI are protonated massive volatile organic compounds (VOCs). Some of the observed positive CI may also be cluster ions composed of VOCs.