Mean excitation energies of singly charged atomic anions with Z ≤ 18

We present hitherto unknown mean excitation energies of singly charges atomic anions with Z ≤ 18. Most of them are calculated using the random-phase approximation and large basis sets. We have shown that there is a nearly Z-independent, constant ratio between the mean excitation energies of anions and atoms. We have also shown that Bragg's rule may be applied to determine the mean excitation energies of negative ions from mean excitation energies of atoms and cations with the same nuclear charge but a different number of electrons. These relationships were then used to estimate the mean excitation energies of the anions that we could not calculate directly.