Studies of Er ionization energy

This work is aimed at the multiconfigurational Hartree-Fock calculations of the Er ionization energy. Authors have used the ATSP MCHF version in which there are new codes for calculation of spin-angular parts written on the basis of the methodology Gaigalas, Rudzikas and Froese Fischer, based on the second quantization in coupled tensorial form, the angular momentum theory in 3 spaces (orbital, spin and quasispin) and graphical technique of spin-angular ntegrations. They allow the study of configurations with open f-shells without any restrictions and lead to fairly accurate values of spectroscopic data.