Detection of massive negative chemiions in the exhaust plume of a jet aircraft in flight

Gaseous negative ions were mass spectrometrically measured in the exhaust p lume of a jet aircraft in flight. Using a quadrupole mass spectrometer oper ated in a high-pass mode, it was found that by far most of the ions had mas s numbers > 450 amu (atomic mass units) and number densities which markedly exceeded the number densities of ambient atmospheric ions. The latter were observed outside the exhaust plume and had mostly mass numbers < 200 amu. Both their large numbers and large concentrations strongly suggest that the massive ions observed inside the plume are chemiions which were produced b y the jet engines. The low fuel sulfur content (22 mu g/g) suggests that th e massive ions consist at least partly of species other than sulfuric acid. By interaction with exhaust gases these chemiions experienced rapid chemic al transformation and growth in the early exhaust plume already at plume ag es < 0.4 s.