Identify the chemical species responsible for negative-ion signals in CF4

Determine whether the negative-ion carriers produced by dissociative electron attachment in CF4 are F−, CF3−, or other chemical species by obtaining mass-identified measurements that resolve the ambiguity in their exact chemical nature.

Background

The study observes delayed scintillation signals attributed to negative ions formed when electrons undergo dissociative electron attachment in CF4. The measured reduced mobilities are compatible with reported values for both CF3− and F−, but mobility alone does not uniquely identify the carrier.

The paper states that prior measurements were not mass-identified and that contamination, cluster formation, or competing processes may affect the mobility. Consequently, the exact chemical identity of the negative ions remains unresolved.

References

Reduced mobilities measured in this work were in the range of 0.6-1.2~cm$2$V${-1}$cm${-1}$ across the pressures studied. These values agree with the limited range of literature values for CF$_3-$ and F$-$ ion mobilities in CF$_4$ gas mixtures. This arrival time peak has been nominally associated with F$-$ in previous work. However, comparison was difficult as the published values of 0.99-1.15 and 1.46-1.71~cm$2$V${-1}$cm${-1}$ are not mass-identified and ambiguity exists over their exact chemical nature.

— Operation of a negative ion gas time projection chamber without electronegative fill gases  (2609.09843 - McKie et al., 9 Sep 2026) in Section "Signal analysis and results," subsection "Time distribution"