Exotic Bonding Regimes Uncovered in Excited States

다국어 초록 (Multilingual Abstract)

Real‐space tools were employed to show that the chemical bonding scenario used routinely to understand ground states lacks the necessary flexibility in excited states. It is shown that, even for two‐center, two‐electron bonds, the real‐space bond orders have exotic values that have never been reported. The nature of these situations was uncovered by using electron‐counting techniques that provide an appealing statistical interpretation of bonding descriptors, together with simple physical models. Bond orders greater than one as well as negative bond orders for a single bonding electron pair emerge in situations in which the electrons in the pair show a gregarious (bosonic) instead of the usual lonely (fermionic) behavior. In the first case the gregarious pair is intra‐atomic, whereas the coupling is interatomic in the second. A number of examples are used to substantiate these claims.
Real‐space tools were employed to show that the chemical bonding scenario used routinely to understand ground states lacks the required flexibility for excited states. Real‐space bond orders can have previously unreported exotic values, and bond orders greater than one and negative bond orders for a single electron pair emerge in situations in which the electrons in a bonding pair show a gregarious (bosonic) instead of the usual lonely (fermionic) behavior (see figure).