Term values of Na-like iron group highly stripped ions using coupled-cluster theory

More accurate term values, a few line strengths and transition probabilities for the E2 transitions of the iron group highly stripped ions Fe XVI, Co XVII and Ni XVIII are reported. We have used the fully relativistic Dirac-Hartree-Fock orbitals to form the Slater determinants to represent different atomic states and included the effect of Coulomb correlation using a fully ab initio all-order many-body coupled-cluster method. In this method, atomic wavefunctions are decomposed in terms of the amplitudes of exciting clusters of a finite number of particles. We have included all the single, double and partially triple excitations from the core in our calculation with a large basis of 98 bound and continuum orbitals within a maximum energy of 500 a.u. chosen through a highly improved methodology. It is found that the percentage errors in term values are highly correlated with the nuclear charges (Z). (author). Letter-to-the-editor