title: Origin of the enhancement of the second hyperpolarizability of singlet diradical systems with intermediate diradical character.
abstract: The origin of the diradical character dependence of the second hyperpolarizability (gamma) of neutral singlet diradical systems is clarified based on the perturbation formula of gamma using the simplest diradical molecular model with different diradical characters, i.e., H2 under bond dissociation. The enhancement of gamma in the intermediate diradical character region turns out to originate from the increasing magnitude of the transition moment between the first and second excited states and the decrease of that between the ground and first excited states, respectively, with the increase in diradical character. This feature confirms that open-shell singlet conjugated molecules with intermediate diradical characters constitute a new class of third-order nonlinear optical systems, whose gamma values can be controlled by the diradical character in addition to the conjugation length.
authors.affiliation: mnaka@cheng.es.osaka-u.ac.jpDepartment of Materials Engineering Science, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan.
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Nakano
authors.forename: Ryohei
authors.initials: R
authors.lastname: Kishi
authors.forename: Suguru
authors.initials: S
authors.lastname: Ohta
authors.forename: Akihito
authors.initials: A
authors.lastname: Takebe
authors.forename: Hideaki
authors.initials: H
authors.lastname: Takahashi
authors.forename: Shin-ichi
authors.initials: S
authors.lastname: Furukawa
authors.forename: Takashi
authors.initials: T
authors.lastname: Kubo
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Morita
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Nakasuji
authors.forename: Kizashi
authors.initials: K
authors.lastname: Yamaguchi
authors.forename: Kenji
authors.initials: K
authors.lastname: Kamada
authors.forename: Koji
authors.initials: K
authors.lastname: Ohta
authors.forename: Benoît
authors.initials: B
authors.lastname: Champagne
authors.forename: Edith
authors.initials: E
authors.lastname: Botek