Preferred Label : conical intersection;
IUPAC definition : Point of crossing between two electronic states of the same spin multiplicity (most
commonly singlets or triplets).;
Scope note : from a mechanistic point of view, conical intersections often provide the channel
mediating radiationless deactivation and photochemical reaction.; in a polyatomic molecule two potential energy surfaces are allowed to cross along
a (3n - 8)-dimensional subspace of the (3n - 6)-dimensional nuclear coordinate space
(the intersection space) even if they have the same spatial/spin symmetry (n is the
number of nuclei). each point of the intersection space corresponds to a conical intersection.
if the energy is plotted against two special internal geometrical coordinates, x1
and x2, which define the so-called branching plane, the potential energy surface would
have the form of a double cone in the region surrounding the degeneracy. in the remaining
(3n - 8) directions, the energies of the ground and excited state remain degenerate;
movement in the branching plane lifts the degeneracy.;
Origin ID : CT07347;
See also
Point of crossing between two electronic states of the same spin multiplicity (most
commonly singlets or triplets).
