“…They constitute points of degeneracy between two (or more) PES and facilitate a rapid radiationless decay to the lower lying state. With the ongoing development of computational methods, the search in the degeneracy space, called the intersection space (IS), for energetically low lying crossings has become possible. ,− Studies by Bernardi, Garavelli, Olivucci, and Robb revealed that a number of minimum energy CoIn are characterized by common two-, three-, and four-center patterns. ,, The fundamental work of Michl and Bonačić-Koutecký shed light on the electronic structure of the IS , between GS and ES in linear conjugated systems. The torsional deformation about a double bond leads to the degeneracy of the π and π* orbitals and to the formation of an S 1 /S 0 avoided crossing (Figure a).…”