where C i 1 ...i N (A, S) are the coefficients determined by the diagonalization. This represents the Configurational Interaction wavefunction for N particles distributed among M states, with A and S indicating antisymmetrization (Slater determinant) for fermions or symmetrization for bosons. In CI, the wavefunction is expressed as a linear combination of Slater determinants, and the coefficients C i 1 ...i N (A, S) are optimized variationally.