title: Determining x-ray nonlinear susceptibility of diamond by the optical Fano effect.
abstract: X-ray nonlinear optics, which has been considered as a scientific frontier to be explored with x-ray free-electron lasers, is accessible with existing synchrotron x-ray sources, revealing its unique features. We demonstrate that x-ray parametric down-conversion is observed indirectly through quantum mechanical interference known as the Fano effect. By introducing a novel concept of photonic discrete levels, we determine the second order nonlinear susceptibility of diamond, and find a strong resonance enhancement at the core absorption edge that presents firm experimental evidence to develop x-ray nonlinear optics.
authors.affiliation: RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148 Japan. tamasaku@riken.jp
authors.forename: Kenji
authors.initials: K
authors.lastname: Tamasaku
authors.forename: Kei
authors.initials: K
authors.lastname: Sawada
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Ishikawa