IONIZATION-POTENTIALS AND EXCITATION-ENERGIES OF THE ALKALI-METAL ATOMS BY THE RELATIVISTIC COUPLED-CLUSTER METHOD

Ground- and excited-state energies, as well as ionization potentials a nd electron affinities, are calculated for all the alkali-metal atoms Li-Fr by the relativistic Fock-space coupled-cluster method. The coupl ed-cluster singles and doubles approximation, which includes single an d double virtual excitations in a self-consistent manner, is implement ed. The no-pair Dirac-Coulomb-Breit Hamiltonian is taken as the starti ng point. Rather extensive basis sets of balanced Gaussian spinors are used to span the atomic orbitals. The average error for the ionizatio n potentials is 0.09% and for excitation energies 0.2%. Electron affin ities are less accurate, particularly for the heavier atoms, with erro rs of 4-9% for K, Rb, and Cs.