In the context of X-ray crystallography, fluorescence occurs when an X-ray photon is absorbed by an atom in the crystal, causing an electron to be excited to a higher energy state. A wavelength-dispersive optical system based on double-curved crystal (DCC) with multiple faces was designed. A Johann-type graphite curved crystal was used to focus the. Fluorescence is a process in which a molecule absorbs energy from an external source, such as X-rays, and then emits energy at a specific wavelength. The Rayleigh effect is present when electrons are strongly bound (inner atomic electrons).