[itex]R_\infty[/itex] is calculated assuming a fixed nucleus (thus assuming an infinite mass), while [itex]R_\mathrm{H}[/itex] is calculated for an actual proton that can move (thus in the center-of-mass frame).What is the difference between R∞ and R[itex]_{H}[/itex]? Physically and mathematically.
Thanks