Rydberg states of helium: Nuclear-recoil corrections

The nuclear-recoil terms contributing to the fine-structure splitting of 1sNL Rydberg states of helium are calculated. A great simplification resulting from the use of nonsymmetric Jacobi coordinates makes it possible to write the corrections to all terms in the asymptotic optical potential without additional computation. The isotope shifts between ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ and ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ are displayed and evaluated.