PHYSICAL REVIEW A
We calculate the two-photon exchange correction to the Lamb shift in muonic He-3 ions within the dispersion relations framework. Part of the effort entailed making analytic fits to the electron-He-3 quasielastic scattering data set, for purposes of doing the dispersion integrals. Our result is that the energy of the 2S state is shifted downwards by two-photon exchange effects by 15.14(49) meV,
Carlson, Carl E.; Gorchtein, Mikhail; and Vanderhaeghen, Marc, Two- photon exchange correction to 2S-2P splitting in muonic He-3 ions (2018). PHYSICAL REVIEW A, 95(1).