Laser-Induced Population Transfer and Ion Dynamics of 25Mg+ ions at CRYRING@ESRONLINE ONLY

We have performed laser spectroscopy on 25Mg+ ions stored in CRYRING@ESR to investigate a possible production of polarized ion beams by optical pumping. Hints of such an effect were previously observed during a time dilation experiment with 7Li+ ions at the ESR [1]. At CRYRING, we employed a similar collinear/anticollinear laser spectroscopy scheme to perform Λ-type optical-optical double resonance (OODR) spectroscopy. The 25Mg+ beam was produced by the electron cyclotron resonance ion source (ECRIS) of the local injector of CRYRING. Subsequently, the ions were bunched, accelerated up to 155 keV/u and prepared by electron cooling.

During the experiment, we observed a fast laser-induced population transfer between the hyperfine ground states F=3 and F=2 in 25Mg+. This population transfer was enhanced by the mixing of different velocity classes caused by synchrotron oscillations. Additionally, we observed a re-excitation of the synchrotron oscillation when the electron beam axis was shifted horizontally against the ion beam axis by as little as 1 mm. This can be explained by the dispersive coupling of the longitudinal and transverse motion of the ions in the electron cooler section. In the ultra-low energy regime of CRYRING, where the potential well of the electron space charge is comparatively deep, this effect is particularly pronounced.

In this talk, I will present the current status of the experiment and discuss the different dynamic effects on the atomic state populations and the ions velocity distribution. Our findings are not only relevant for future laser spectroscopic investigations, but also to understand the complex dynamics of ions in electron-cooled storage rings. I will conclude with perspectives for future laser spectroscopy experiments at CRYRING.

[1] W. Nörtershäuser et al., Physical Review Accelerators and Beams 24, 024701 (2021)