Farbstoffzentren

Farbstoffzentren, also known as color centers or F-centers in German literature, are point defects in crystal lattices that absorb and emit light, giving the otherwise transparent crystal a color. These defects typically arise when an anion vacancy is occupied by an electron. The electron, trapped in the vacancy, can absorb photons of specific wavelengths, causing it to transition to a higher energy level. When the electron returns to its ground state, it emits a photon, which can be in the visible spectrum, thus imparting color to the material.

The simplest and most common type of farbstoffzentrum is the F-center, which consists of a single electron trapped in an anion vacancy. Other types of color centers exist, involving more complex arrangements of vacancies, interstitials, or impurity atoms, along with trapped electrons or holes. For example, M-centers are formed by two adjacent anion vacancies, each occupied by an electron.

Farbstoffzentren are often created by irradiation with high-energy particles like X-rays, gamma rays, or electron beams, which can knock atoms out of their lattice positions, creating vacancies. They can also be formed by non-stoichiometry during crystal growth or by diffusion of impurities. The study of farbstoffzentren is important in materials science and solid-state physics, as they influence the optical and electrical properties of crystals. They are relevant in fields such as laser technology, dosimetry, and as models for understanding defect behavior in ionic solids.