Have we seen first optical pumping in a storage ring?

This question is investigated in our paper published today in Physical Review Accelerators and Beams.
We study optical pumping in the ESR using a rate equation approach to explain the disappearance of an optical resonance in Li⁺ when changing for linear to circular polarized light. We come to the conclusion that this disappearance cannot be explained without assuming that the created polarization must at least partially survive a revolution in the storage ring. This is a strong motivation for further investigations at CRYRING@ESR, where we hope to observe similar effects with Mg⁺ ions and to study them in detail.
The paper is open access and can be accessed here.