DESIREE: A tool for cooling and colliding oppositely charged ions

by Henning Zettergren (Università di Stoccolma)

Tuesday 14 Apr 2026, 16:00 → 18:00 Europe/Rome

Aula Conversi (Dipartimento di Fisica-Ed. G.Marconi)

Department of Physics, Stockholm University, SE-10691, Stockholm, Sweden

Low-energy ion–pair collisions are expected to play a decisive role in the chemistry of dilute

environments where anions, rather than electrons, act as the primary negative charge carriers [1].

Under such conditions, reactions can occur that are prohibited for neutral molecules at thermal

energies. This is due to the Coulomb driven acceleration between the oppositely charged ions,

allowing for unique bond forming reactions, growth of new species, or formation of energetic neutrals

with velocities well above the thermal ones. Consequently, these reactions may be crucial for the

chemical evolution of molecules in, e.g., the interstellar medium and planetary atmospheres.

The cryogenically cooled ion beam storage ring facility DESIREE (Double ElectroStatic Ion Ring

ExpEriment) is uniquely designed for studies of collisions between oppositely charged ions prepared

in well-defined or narrow ranges of quantum states and with fine-control of the collision energy down

to the sub-electronvolt regime [2,3]. Furthermore, the excellent vacuum conditions allow studies of

inherent properties and the dynamics of atomic, molecular, and cluster ions on timescales exceeding

minutes and in unprecedented detail.

In this talk, I will highlight recent DESIREE results, including high-precision measurements of

electron affinities [4,5] and studies of molecular stability and competing relaxation pathways explored

in previously inaccessible time domains [6-9]. I will also present studies of mutual neutralization

reactions involving atoms [10], small di- and tri-atomic molecular systems [11-14], and complex

molecules such as polycyclic aromatic hydrocarbons (PAHs) and fullerenes [15]. These results are

important for improving the accuracy of models describing chemical processes in, e.g., planetary

atmospheres and a range of astrophysical environments.

 

References

[1] T. J. Millar, C Walsh, & T. A. Field, Chem. Rev. 117, 1765 (2017)

[2] R. D. Thomas et al, Review Scientific Instruments 82, 0655112 (2011).

[3] H. T. Schmidt et al, Review Scientific Instruments 84, 055115 (2013).

[4] J. E. N. Navarrete, et al, Physical Review Letters. 135, 213001 (2025).

[5] M. K. Kristiansson et al, Nature Communications 13, 5906 (2022).

[6] J. N. Bull et al. Physical Review Letters 134, 228002 (2025).

[7] P K Najeeb et al. Physical Review Letters 131, 113003 (2023).

[8] M. Stockett et al, Nature Communications. 14 395 (2023).

[9] M. Gatchell et al, Nature Communications 12, 6646 (2021).

[10] See e.g. J. Grumer et al, Physical Review Letters 128, 033401 (2022) and references therein.

[11] A. Bogot et al, Nature Chemistry 17, 541 (2025).

[12] M. Poline et al, Nature Communications. 16, 8528 (2025).

[13] M. Poline et al, Physical Review Letters 132, 023001 (2024).

[14] A. Bogot et al, Science 383, 285-289 (2024).

[15] M. Gatchell et al, Astronomy & Astrophysics 694, A43 (2025).