Henning Schmidt
Stockholm University

Abstract: Molecular physics studies with the DESIREE storage ring

The Double ElectroStatic Ion-Ring ExpEriment, DESIREE¹, at Stockholm University is a facility consisting of two 8.7 m circumference electrostatic storage rings for 10 – 100 keV ion beams enclosed in a cryogenic vacuum chamber with temperature T=13 K and residual-gas density of n=10³ per cm³.

DESIREE combines long-time storage of keV ion beams with the use of two electrostatic storage rings with a common straight section for merging positively and negatively charged beams. This arrangement offers ideal conditions for studies of mutual neutralization between ions in well-defined initial quantum states².

We will discuss results of spontaneous cooling experiments³ and techniques to actively modify the initial states of the ions⁴, and we will show examples of mutual-neutralization experiments with atomic, small molecular, and complex molecular ions where the evolution of the initial-state distribution during storage is shown to influence the mutual-neutralization process directly⁵. The molecular ions considered are varying in complexity from  diatomic anions⁶ to fullerenes⁷ and polycyclic aromatic hydrocarbons⁸.

Complex dynamics in MN for polyatomics⁹ complicates the identification of specific reactions and underscores the importance of new detector technologies to identify the neutral particles through the amount of kinetic energy dissipated, which is proportional to their masses. A solution based on Metallic Magnetic Calorimetry is discussed.

References
1. HT Schmidt et al, Rev Sci Instrum 84, 055115 (2013)
2. RD Thomas  et al, Rev Sci Instrum 82, 065112 (2011)
3. MH Stockett et al, Nature Communications 14, 395 (2023)
4. R Poulose et al, Physical Review A 113, 042819 (2026)
5. M Poline et al, Nature Communications 16, 8528 (2025)
6. HT Schmidt et al, Physical Review Letters 119, 073001 (2017)
7. M Gatchell et al, Astronomy&Astrophysics  693, A43 (2025)
8. M Gatchell et al, Nature Communications  12, 6466 (2021)
9. A Bogot et al, Science 383, 285 (2024)
 

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