Eg. Myers et al., Lamb shift, fine structure and hyperfine structure in helium-like ions by fast-beam laser spectroscopy, HYPER INTER, 127(1-4), 2000, pp. 323-328
Using Doppler-tuned fast-beam laser spectroscopy with a continuous-wave CO2
laser the following energy intervals in helium-like ions have been measure
d: 1s2s S-1(0)-1s2p P-3(1,F), P-3(0) in N-14,15(5+); 1s2p P-3(2,F)-1s2p P-3
(1,F)' in F-19(7+); and 1s2p P-3(0)-1s2p P-3(1) in Mg-24(10+). The results
test modern relativistic and QED atomic theory.