The rôle of Slater-determinant MO occupation Λ ↑ , Λ ↓ , excitation operators A † , A, C, etc... , and indices I ↑ , J ↓ , etc... , is to sub-index the 3 important arrays: 1-body SO Hamiltonian, 2-body SO Hamiltonian, and the SO sign-matrix. These sub-indexing arrays must be of data type integers.