In the CI method, one writes the many-body wave function Φ CI N (r 1 , r 2 , . . . , r N ) as a linear superposition of Slater determinants Ψ N (r 1 , r 2 , . . . , r N ) that span the many-body Hilbert space and are constructed out of the single-particle spin-isospin-orbitals χ j (r) = φ j (x, y)αζ,