Second Order in Mass Ratio Radiative-Recoil Corrections to Hyperfine   Splitting in Muonium
  Radiative-recoil corrections to hyperfine splitting in muonium of orders $\alpha(Z\alpha)(m/M)^2E_F$ and $(Z^2\alpha)(Z\alpha)(m/M)^2E_F$ are calculated. These corrections are of the second order in the small electron-muon mass ratio. An analytic expression $[(-6 \ln2- \frac{3}{4})\alpha (Z\alpha) - \frac{17}{12} (Z^2 \alpha) (Z\alpha)](\frac{m}{M})^2 E_F$ is obtained. Numerically the correction is equal to $-0.0351\:\mbox{kHz}$ and is of the same order of magnitude as the expected accuracy of the current Los Alamos experiment to measure the hyperfine splitting. 
Michael I. Eides (Petersburg Nuclear Physics Institute, Russia, and   Pennsylvania State University, USA), Howard Grotch (Pe...