which is a space of functions antisymmetric separately in arguments of Ψ A and Ψ B , respectively. Functions of symmetry like ψ (0) are integrated in the product Hilbert space H A ⊗ H B . However, when using the second quantization approach this translates into the product F A ⊗ F B of Fock spaces F A and F B corresponding to the respective monomers A and B.