Theory of the n=2 levels in muonic helium-3 ions

Understand

The present knowledge of Lamb shift, fine-, and hyperfine structure of the 2S and 2P states in muonic helium-3 ions is reviewed in anticipation of the results of a first measurement of several $\mathrm{2S\rightarrow2P}$ transition frequencies in the muonic helium-3 ion, $\mathrm{\mu^3He^+}$.

• This ion is the bound state of a single negative muon $\mu^-$ and a bare helium-3 nucleus (helion), $\mathrm{^3He^{++}}$.
• A term-by-term comparison of all available sources, including new, updated, and so far unpublished calculations, reveals reliable values and uncertainties of the QED and nuclear structure-dependent contributions to the Lamb shift and the hyperfine splitting.
• These values are essential for the determination of the helion rms charge radius and the nuclear structure effects to the hyperfine splitting in $\mathrm{\mu^3He^+}$.