User:Marseglia/sandbox

Nella meccanica quantistica e nella chimica quantistica, il fenomeno dell avoided crossing (sometimes called intended crossing or non-crossing, anticrossing) is defined as the case when the eigenvalues of a Hermitian matrix representing an observable for a system and depending on N continuous real parameters cannot cross (that is, two or more eigenvalues cannot become equal in value) except at a manifold of N-2 dimensions. In the case of a diatomic molecule (one parameter, which describes the bond length), this means that the eigenvalues do not cross. In the case of a triatomic molecule, this means that the eigenvalues can intersect only at a point (see conical intersection).