Abstract
We report on laser spectroscopic measurements on ${\mathrm{Li}}^{+}$ ions in the experimental storage ring ESR at the GSI Helmholtz Centre for Heavy Ion Research. Driving the $2s\text{ }{^{3}S}_{1}(F=3/2)\ensuremath{\leftrightarrow}2p\text{ }{^{3}P}_{2}(F=5/2)\ensuremath{\leftrightarrow}2s\text{ }{^{3}S}_{1}(F=5/2)$ $\mathrm{\ensuremath{\Lambda}}$-transition in $^{7}{\mathrm{Li}}^{+}$ with two superimposed laser beams it was found that the use of circularly polarized light leads to a disappearance of the resonance structure in the fluorescence signal. This can be explained by optical pumping into a dark state of polarized ions. We present a detailed theoretical analysis of this process that supports the interpretation of optical pumping and demonstrates that the polarization induced by the laser light must then be at least partially maintained during the round trip of the ions in the storage ring. Such polarized ion beams in storage rings will provide opportunities for new experiments, especially on parity violation.
Highlights
For many years, beams of spin–polarized particles, ions, and atoms have attracted considerable interest both in fundamental and applied science [1,2,3,4]
7Liþ ions in the metastable 2 3S1 level were produced in a Penning ion source (PIG) source, accelerated in the universal linear accelerator (UNILAC) to an energy of 8 MeV/u and injected into the heavy-ion-synchrotron (SIS) for further acceleration to 58 MeV/u corresponding to a velocity of β 1⁄4 υ=c 1⁄4 0.338, (γ 1⁄4 1.0625)
We have shown in our theoretical analysis that optical pumping in the 2s 3S1ðF1 1⁄4 3=2Þ ↔ 2p 3P2ðF3 1⁄4 5=2Þ ↔
Summary
Beams of spin–polarized particles, ions, and atoms have attracted considerable interest both in fundamental and applied science [1,2,3,4]. We contrast the theoretical results with a measurement of the steady-state fluorescence intensity from a stored ion beam subjected to this laser excitation, which show a significant dependence on the laser polarization Within this framework, we conclude that the observations may indicate a preservation of the hyperfine polarization over a considerable number of round trips. The experimental results were obtained within an experiment to test time dilation in special relativity with Liþ ions stored in the experimental storage ring (ESR) This experiment probed the fluorescence yield from a three-state, Λtype resonance 2s 3S1ðF 1⁄4 3=2Þ ↔ 2p 3P2ðF 1⁄4 5=2Þ ↔ 2s 3S1ðF 1⁄4 5=2Þ in counterpropagating laser beams along the ion direction. The model calculations are adapted to the parameters of the ESR experiment
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