On the negative vertical detachment energies of , and

We have, from a method based on a simple correction to Koopmans’ theorem, calculated the vertical electron detachment energies of SO 4 2 - , SO 4 2 - ( H 2 O ) and SeO 4 2 - to be −1.45 eV, −0.48 eV, and −0.79 eV, respectively. These values are in good agreement with previously published values. The method avoids the basis set breakdown problem encountered for the calculation of energies of electronically unbound systems since it only relies on the calculation of HOMO and LUMO energies (both being negative) and detachment energies (positive) of the corresponding monoanions.