where Ψ N and Ψ N -1 are the solution of the electronic Schrödinger equation for a cation (one unpaired electron) and a dication (closed-shell), respectively. The pair of states with Dyson orbitals localized outside of the bond area are likely to have diagonal FCFs. The idea of rational engineering of OCCs by seeking molecules with localized atomic-like transitions was first described in a break-through paper by Isaev and Berger 36 , who also proposed several promising candidates. Their strategy has been later successfully exploited in laser-cooling of polyatomic neutral molecules . Following this strategy, more polyatomic molecules were proposed as prospective candidates for laser cooling .