title: Full configuration interaction calculations of the second hyperpolarizabilities of the H4 model compound: summation-over-states analysis and interplay with diradical characters.
abstract: The second hyperpolarizability (γ) of the one-dimensional H(4) model compound has been calculated at the full configuration interaction level to describe its relationships with the diradical characters y(i) [the occupation numbers of the lowest unoccupied natural orbital (LUNO) + i] and the geometry. It is found that the system with intermediate y(0) ( = 0.527) and small y(1) ( = 0.178) exhibits the largest γ value [enhanced by a factor of 9 compared to that of a nearly closed-shell H(4) analog (y(0) = 0.099, y(1) = 0.029)], where both the outer H-H distances are slightly larger than the inner one. These results provide a molecular design guideline for enhancing and controlling the third-order nonlinear optical properties of singlet multiradical linear molecular systems such as multiradical organic aggregates, supermolecular systems, and extended metal atom chains.
authors.affiliation: Department of Materials Engineering Science, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan. mnaka@cheng.es.osaka-u.ac.jp
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Nakano
authors.forename: Takuya
authors.initials: T
authors.lastname: Minami
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Fukui
authors.forename: Ryohei
authors.initials: R
authors.lastname: Kishi
authors.forename: Yasuteru
authors.initials: Y
authors.lastname: Shigeta
authors.forename: Benoît
authors.initials: B
authors.lastname: Champagne