Landau–Zener model
Within the Born–Oppenheimer approximation, a semi-classical model for the @[email protected], \(P\), of hopping from one @[email protected] to another of the same or different multiplicity \[P=\exp (- \frac{4\ \pi ^{2}\ \varepsilon_{12}^{2}}{h\ \nu\ |s_{1}-s_{2}|})\] where \(ɛ_{12}\) is the potential energy gap between the two electronic states at a @[email protected] point, \(|s_{1}- s_{2}|\) is the difference in slopes between the intersecting potential energy curves at this point and \(\nu\) is the nuclear relative velocity with which the system passes the point of closest approach.
The original formalism only considered states of the same spin multiplicity.
PAC, 2007, 79, 293. (Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)) on page 362 [Terms] [Paper]