title: Revisiting the S1/S0 Degeneracy Space along the Exocyclic Methylene Twist Motion of Fulvene through a Two-Step Procedure.
abstract: We have characterized the degeneracy space (DS) between the ground (S0) state and the first excited (S1) state along the exocyclic methylene twist motion of fulvene, using our calculation strategy, i.e., a two-step procedure with CASSCF. The origin of the "cancellation error" on locating degeneracy points under geometrical constraints is analyzed, leading to a method to assess adequacy of the strategy. According to our estimation, these S1/S0 DPs are optimized for energy within 2.0 × 10(-)(3) Eh Å(-)(1) (the value of root-mean-square). From the obtained S1/S0 DS, we provide some information about the exocyclic methylene rotation by 180(◦).
authors.affiliation: Department of Chemistry, Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8571, Japan.
authors.forename: Masato
authors.initials: M
authors.lastname: Sumita
authors.affiliation: Department of Chemistry, Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8571, Japan.
authors.forename: Kazuya
authors.initials: K
authors.lastname: Saito