International Conference on Exotic Atoms and Related Topics and conference on Low Energy Antiprotons (EXA/LEAP 2024)

Towards laser cooling of negative molecular ions

27 Aug 2024, 17:30

2h

Aula (Vienna)

Poster

Speaker

Matthias Germann (CERN)

Description

The AEgIS experiment at CERN's Antiproton Decelerator aims at measuring the gravitational acceleration $\overline{\text{g}}$ of antihydrogen ($\overline{\text{H}}$) with high precision [1, 2]. A key limitation in these measurements is the $\overline{\text{H}}$ temperature: The thermal motion of the $\overline{\text{H}}$ atoms blurs their free-fall trajectories and thus limits the achievable $\overline{\text{g}}$ precision.

The temperature of antihydrogen, which is formed at AEgIS in a laser-induced charge transfer reaction between positronium and antiprotons ($\overline{\text{p}}$), is dominated by the temperature of the antiproton precursors. With the current passive cooling scheme, the achievable $\overline{\text{p}}$ temperature is limited to at best tens (but to date a few hundred) kelvin.

Sympathetic cooling of antiprotons through thermalization with co-trapped laser-cooled ions would enable achieving temperatures in the mK range. However, to avoid annihilation, the co-trapped coolant ions must be negatively charged.

The Borealis project at AEgIS aims at realizing Doppler laser cooling of a negative ion. In particular, the diatomic molecular C${}_2^{-}$ ion, a well-suited anion species for laser cooling [3], has been produced, mass-selected and stored in a linear Paul trap [4]. Currently, the capture efficiency of the trap and the lifetime of trapped C${}_2^{-}$ ions are improved and preparations for preliminary in-beam spectroscopic studies are underway.

[1] G. Drobychev et al., Proposal for the AEGIS experiment at the CERN antiproton decelerator, CERN-SPSC-2007-017, SPSC-P-334.
[2] R. Caravita et al., AEgIS/AD-6 annual report 2023, CERN-SPSC-2023-003, SPSC-SR-321.
[3] P. Yzombard et al., Laser Cooling of Molecular Anions, Phys. Rev. Lett. 114, 213001 (2015).
[4] A. Hinterberger et al., Trapping of C${}_2^{-}$ in a digital ion trap, J. Phys. B: At. Mol. Opt. Phys. 52, 225003 (2019).