**Conical Intersection** A conical intersection of two potential energy surfaces is the set of molecular geometry points where the two potential energy surfaces (PESs) intersect; when they are degenerate. A condition is that both PESs are of the same spatial and spin symmetry.

If two PESs are plotted as functions of 2 coordinate, they form a cone centered at the degeneracy point. Hence the name conical intersection.

Synonyms for conical intersection:

molecular funnel

diabolic point

Other related terms:

Seam = the intersection space = geometry points that are degenerate ; have equal energy

Branching space = the dimensions that lift the energy degeneracy of the system

__See also:__ PES: Potential energy surface

http://www.oraxcel.com/cgi-bin/yabb2/YaBB.pl?num=1216671925 __Source:__ http://en.wikipedia.org/wiki/Conical_intersection