      delta E_Lint =          E[A.B]-(E[A]+E[B]) = -0.234 eV
      delta E_exciton =       E[exciton]-E[A.B]  = +5.332 eV 
delta delta E_superexchange = E[SE]-E[exciton]   = -2.335 eV
delta delta E_OCD =           E[es]-E[SE]        = +0.154 eV
