Rydberg constant
= Rydberg constant
{c}
{title2=$R_\infty$}
{wiki}
The inverse-length constant in the infinite-nuclear-mass hydrogenic spectrum, $R_\infty=m_ee^4/[8\epsilon_0^2h^3c]$. A nucleus of finite mass replaces it by $R_M=R_\infty\mu/m_e$, where $\mu$ is the electron-nucleus <reduced mass>. Some spectroscopic fits call $Z^2R_M$ an effective Rydberg constant; the charge-inclusive and reduced-mass-only conventions must be distinguished.