singlet–triplet crossing
Point of intersection between the potential energy surfaces of states of different multiplicity.
The intersection belongs to a (\(3\ N-7\))-dimensional subspace of the (\(3\ N-6\))-dimensional nuclear coordinate space and therefore appears as a line on a two-dimensional energy surface (\(N\) is the number of nuclei). In this case the @[email protected] is one-dimensional and is defined by the @[email protected] difference vector \(x_{1}\).
PAC, 2007, 79, 293. (Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)) on page 421 [Terms] [Paper]