On spectral line shifts from analytic fits to the ion-sphere model potential

A simplification of a fit to the free electron potential in ion-sphere models to obtain an analytic formula for level shifts (Li and Rosmej, 2012 [5]) is shown to be inconsistent with the fundamental premise of a neutral ion-cell. On the other hand, the original fit (Rosmej et al., 2011 [4]) avoids the problem and also leads to analytic formulas.