Speaker
Description
The formation and breakage of molecular bonds is at the core of understanding and controlling chemical reactions that determine our life, quality of terrestrial environment as well as evolution of the universe. Depending on the nature of the colliding species different chemical reactions can occur.
In particular, when two molecular ions interact, this can lead to the charge transfer from an anion to a cation, resulting in their mutual neutralisation (MN). Depending on the collision energy this process may lead to the formation of molecular bonds and new species, or to the separation of the two neutral species that are electronically excited. When one of the species is a polyatomic molecule, it can also be ro-vibrationally excited and undergo molecular dissociation as result of internal conversion from an electronic excited state or from head-on collisions (nuclear stopping).
In this work we took advantage of the unique opportunity offered by the cryogenic double electrostatic ion beam storage ring facility DESIREE [1-6] to study mutual neutralization reactions in ~100 meV collisions between pyrimidine cations and atomic anions. In these experiments we performed both two- and three-particle coincidence measurements to explore the charge transfer process at relatively large (oxygen anion) and short (chlorine anion) distances, as well as the following pyrimidine molecule fragmentation. These experiments, supported by Landau-Zener model calculations as well as molecular dynamics simulation, will provide fundamental understanding of biomolecular interactions in relatively complex systems.
References
[1] R. D. Thomas et al, Review Scientific Instruments 82, 0655112 (2011).
[2] H. T. Schmidt et al, Review Scientific Instruments 84, 055115 (2013).
[3] See e.g. J. Grumer et al, Physical Review Letters 128, 033401 (2022) and references therein.
[4] M. Poline et al, Physical Review Letters 132, 023001 (2024).
[5] A. Bogot et al, Science 383, 285-289 (2024).
[6] M. Gatchell et al, Astronomy & Astrophysics 694, A43 (2025).
Acknowledgments
This work is supported by Italian Ministry of Foreign Affairs and International Cooperation”, grant number PGR02090; PNRR-IR project EuPRAXIA Advanced Photon Sources—EuAPS (CUP I93C21000160006, IR0000030); COST Action CA20129 "Multiscale Irradiation and Chemistry Driven Processes and Related Technologies" (MultIChem).
