title: Relationship between photoisomerization path and intersection space in a retinal chromophore model.
abstract: A low-lying segment of the intersection space (IS) between the excited-state and the ground-state energy surfaces of a retinal chromophore model has been mapped using ab initio CASSCF computations. Analysis of the structural relationship between the computed IS cross-section and the excited state Z --> E isomerization path shows that these are remarkably close both in energy and in structure. Indeed, the IS segment and the Z --> E path remain roughly parallel and merge only when the double bond reaches a 70 degree twisting. This finding supports the idea that, in certain chromophores, a more extended segment of IS, and not a single conical intersection, contributes to the decay to the ground state.
authors.affiliation: Dipartimento di Chimica, Università degli Studi di Siena, via Aldo Moro, Siena 53100, Italy.
authors.forename: Annapaola
authors.initials: A
authors.lastname: Migani
authors.forename: Michael A
authors.initials: MA
authors.lastname: Robb
authors.forename: Massimo
authors.initials: M
authors.lastname: Olivucci
mesh_terms: D007536:Isomerism; D008956:Models, Chemical; D010777:Photochemistry; D012172:Retinaldehyde / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D012172:Retinaldehyde