Abstract
Measurements of negative chemiions (CI) emitted by a jet engine at the ground were made with an ion trap mass spectrometer. The new instrument offered a high-mass resolution, which led to a first unambiguous identification of negative CI formed by a jet engine. The observed ions are HSO 4 −(H 2SO 4) a clusters proved by an isotope study. From the mass spectra an efficiency ε for fuel sulfur conversion to S VI of 2%±0.8 could be inferred. In addition thermodynamic properties of the observed cluster ions were inferred from measured ion abundance ratios. An effective free energy Δ G a−1, a 0=−14 kcal/mol was calculated (for a=3) and an enthalpy of Δ H a−1, a 0=−24 (for a=3) kcal/mol was estimated. This indicates a low stability of HSO 4 −(H 2SO 4) a ( a⩾3) cluster ions against thermal detachment of H 2SO 4 at the high temperatures of our experiment. However the low temperatures at cruise altitudes around 10–12 km lead to high H 2SO 4/H 2O supersaturation and therefore a rapid growth of HSO 4 −(H 2SO 4) a cluster ions seems to be possible which is not hindered by thermal H 2SO 4 detachment.
Published Version
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