Finite nuclear size corrections to the recoil effect in hydrogenlike   ions
  The finite nuclear size corrections to the relativistic recoil effect in H-like ions are calculated within the Breit approximation. The calculations are performed for the $1s$, $2s$, and $2p_{1/2}$ states in the range $Z =$ 1-110. The obtained results are compared with previous evaluations of this effect. It is found that for heavy ions the previously neglected corrections amount to about 20% of the total nuclear size contribution to the recoil effect calculated within the Breit approximation. 
I. A. Aleksandrov, A. A. Shchepetnov, D. A. Glazov and V. M. Shabaev
physics.atom-ph