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In physics, an absorption edge (also known as an absorption discontinuity or absorption limit) is a sharp discontinuity in the absorption spectrum of a substance. These discontinuities occur at wavelengths where the energy of an absorbed photon corresponds to an electronic transition or ionization potential .
The Urbach Energy, or Urbach Edge, is a parameter typically denoted , with dimensions of energy, used to quantify energetic disorder in the band edges of a semiconductor. It is evaluated by fitting the absorption coefficient as a function of energy to an exponential function.
Karl W. Böer observed first the shift of the optical absorption edge with electric fields [1] during the discovery of high-field domains [2] and named this the Franz-effect. [3] A few months later, when the English translation of the Keldysh paper became available, he corrected this to the Franz–Keldysh effect. [4]
In the solid-state physics of semiconductors, the Urbach tail is an exponential part in the energy spectrum of the absorption coefficient. This tail appears near the optical band edge in amorphous , disordered and crystalline materials.
One of the most accurate theories of semiconductor absorption and photoluminescence is provided by the SBEs and SLEs, respectively. Both of them are systematically derived starting from the many-body/quantum-optical system Hamiltonian and fully describe the resulting quantum dynamics of optical and quantum-optical observables such as optical polarization (SBEs) and photoluminescence intensity ...
Metal K-edge spectroscopy is a spectroscopic technique used to study the electronic structures of transition metal atoms and complexes.This method measures X-ray absorption caused by the excitation of a 1s electron to valence bound states localized on the metal, which creates a characteristic absorption peak called the K-edge.
Typically, a Tauc plot shows the quantity hν (the photon energy) on the abscissa (x-coordinate) and the quantity (αhν) 1/2 on the ordinate (y-coordinate), where α is the absorption coefficient of the material. Thus, extrapolating this linear region to the abscissa yields the energy of the optical bandgap of the amorphous material.
The optical absorption spectrum of a solid is most straightforwardly calculated from the electronic band structure using Fermi's Golden Rule where the relevant matrix element to be evaluated is the dipole operator where is the vector potential and is the momentum operator.