The Effect of the Motion of the Nucleus on the Spectra of Li I and Li II

The wave equation for a system of $N$ electrons (mass $m$) and one nucleus (mass $M$) is set up and solved approximately. If $W\left(m\right)\mathrm{}$ are the energy levels for $M=\infty$, the energy levels for finite $M$ are $\left(\frac{\mu W\left(m\right)\mathrm{}}{m}\right)+\Delta W$, where $\mu =\frac{\mathrm{mM}}{\mathrm{}(m+M)\mathrm{}}$ and $\Delta W$ is calculable.