title: Kramers-Kronig relation between nonlinear absorption and refraction of C(60) and C(70).
abstract: Using the Z-scan technique with 532 nm 16 picosecond laser pulses, we observe reverse saturable absorption and positive nonlinear refraction of toluene solutions of both C(60) and C(70). By deducting the positive Kerr nonlinear refraction of the solvent, we notice that the solute molecules contribute to nonlinear refraction of opposite signs: positive for C(60) and negative for C(70). Attributing nonlinear absorption and refraction of both solutes to cascading one-photon excitations, we illustrate that they satisfy the Kramers-Kronig relation. Accordingly, we attest the signs and magnitudes of nonlinear refraction for both solutes at 532 nm by Kramers-Kronig transform of the corresponding nonlinear absorption spectra.
authors.affiliation: Department of Physics, National Chung Cheng University, Min-Hsiung, Chia-Yi 621, Taiwan.
authors.forename: Chen-Cheng
authors.initials: CC
authors.lastname: Wu
authors.forename: Tai-Min
authors.initials: TM
authors.lastname: Liu
authors.forename: Tai-Ying
authors.initials: TY
authors.lastname: Wei
authors.forename: Li
authors.initials: L
authors.lastname: Xin
authors.forename: Yi-Ci
authors.initials: YC
authors.lastname: Li
authors.forename: Li-Shu
authors.initials: LS
authors.lastname: Lee
authors.forename: Che-Kai
authors.initials: CK
authors.lastname: Chang
authors.forename: Jaw-Luen
authors.initials: JL
authors.lastname: Tang
authors.forename: Sidney S
authors.initials: SS
authors.lastname: Yang
authors.forename: Tai-Huei
authors.initials: TH
authors.lastname: Wei