ABSTRACT
In this chapter we start with a brief discussion of units and with some remarks on the structure of f N electron configurations. The particular emphasis is on the calculation of the low lying states of f 6 configuration as realized in neutral samarium, (Sm I ), and in triply ionized europium, (EuI V or Eu3+). Special attention is paid to the ground multiplet 7 F . In the search for the explanation of its structure, a detailed account and calculation of the Zeeman effect with particular emphasis on the two lowest levels, 7 F0 and 7 F1, of the f 6 configuration for both weak and strong magnetic fields in the presence of magnetic hyperfine interactions are given.
