Introduction to the Theory of Mass Shifts in Optical Spectra

Abstract

This isotope shift is usually called the normal mass shift; it is also called the Bohr shift or the reduced mass effect. Consider an electron of mass m interacting with a point nucleus of mass M via their mutual electrostatic attraction. In classical mechanics the two particles can be treated as one particle with a reduced mass mM/(M + m) interacting with an infinitely massive particle at rest.