In solid state physics and physical chemistry, the fine electronic structure of an atom or ion is the structure of the energy levels induced by intrinsic interactions between spin and electron magnetic moments (LS coupling and jj coupling) of electrons and external interactions of electrons with the electric field potential of lattice surroundings in crystal.
Interactions of electrostatic potential with many-electron states of atoms/ions are most commonly described in crystal field theory. The term "fine electronic structure" means the existence of a structure close lying many-electron energy states, derived from the abolition of degenerate electronic configurations of a paramagnetic atom or ion. The fine electronic structure is formed from the atomic term structure and multiplet structure under the influence of multipolar electrostatic interactions which further energy levels splitting – Stark effect.
Depending on the accounting methodology of calculating, the fine electronic structure is carried out on the basis of many-electron wave functions written by components of the quantum numbers of full moment of the electron subshell (J) or spin and orbit moment component separately (L and S).
It means, interactions of electrons from unclosed electronic subshell (p, d or f) with Crystal electric Field can be describe by Hamiltonian matrix with elements: |J, Jz >, or | L, S. Lz, Sz >. The fine electronic structure of ion/atom in solid material is fundamental for understanding of single ionic properties of materials with localized magnetic moments.
In solid state physics in a non-zero temperature of the states of fine electronic structure determines the magnetic properties (single-ionic magnetic anisotropy, magnetic susceptibility as a function of temperature) and thermodynamic (Schottky-type specific heat, entropy etc.). The fine electronic structure calculations has been developed for the vast group of solid compounds containing transition metals and rare earth elements [5] (group of 3d, 4d, 4f and 5f). In solid state physics, the fine electron structure is shaped by crystalline field whose effect is described using the multipolar operators defined in the convention, B. G. Wybourne'a or Stevens. Both conventions are consistent, providing a Crystal field parameters Bmn, Bkq and Amn. The fine electronic structure in the material containing paramagnetic ions determines single ionic anisotropy of material and has a basic knowledge about the behavior of atoms or ions in a solid material at low to medium temperatures.