EC-31. A versatile chemical ionization mass spectrometer for stratospheric research

We developed of a chemical ionization mass spectrometer with a new ion source specifically designed for in situ measurements of trace gases in the upper troposphere and lower stratosphere. The ion source utilizes a commercially available photoionization krypton lamp, primarily emitting photons in the vacuum ultraviolet (VUV) region at wavelengths of 124 and 117 nm (corresponding to energies of 10 and 10.6 eV, respectively), coupled to a commercially available Vocus proton transfer reaction mass spectrometer (Vocus PTR). The VUV ion source can produce both negative and positive reagent ions; however, we primarily focused on generating iodide anions (I−). In this operating mode, the instrument was successfully deployed onboard NASA's WB-57 high altitude research aircraft in February 2022 for the first time.