Characterize electron-ionization signatures of radical species

Determine whether radical species in comet 67P/Churyumov-Gerasimenko produce strong molecular-ion signals under the 45 eV electron-ionization conditions of the ROSINA Double Focusing Mass Spectrometer, thereby establishing how reliably such radicals can be identified or constrained in the cometary coma.

Background

The paper notes that radical species may contribute to residual signals in the DFMS spectrum, particularly because hydrogen-deficient species are common in interstellar environments. However, most radicals lack reference mass spectra, and the deconvolution method requires a detectable molecular-ion signal for an unambiguous identification. Without laboratory fragmentation data, the authors cannot determine whether radicals would generate sufficiently strong molecular ions or whether they could remain hidden among fragment signals.

References

For most radical species no reference mass spectra are available and we do not know whether or not these species yield strong M signals.

— Nitrogen- and nitrogen-oxygen-bearing organic molecules in comet 67P/Churyumov-Gerasimenko: An untargeted investigation  (2608.24235 - Hänni et al., 25 Aug 2026) in Section 5.1, “General interpretation and caveats”