where Ẽn = E + + ε + i is the nonstationary energy of the n-electron system constructed by reattaching the n th -electron to the selfconsistently optimized orbitals of the core ion. The energy of the core-ionized state is E + , the core-hole orbital i has energy ε + i , F + ab are elements of the virtual-virtual block of the n-1-electron Fock matrix, (ia|ib) is an exchange integral in Mulliken notation, C HF is the coefficient of exact Hartree-Fock (HF) exchange, and