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In physics, absorption cross-section is a measure of the probability of an absorption process. More generally, the term cross-section is used in physics to quantify the probability of a certain particle-particle interaction, e.g., scattering , electromagnetic absorption , etc. (Note that light in this context is described as consisting of ...
Schematic of energy levels involved in two photons absorption. In atomic physics, two-photon absorption (TPA or 2PA), also called two-photon excitation or non-linear absorption, is the simultaneous absorption of two photons of identical or different frequencies in order to excite an atom or a molecule from one state (usually the ground state), via a virtual energy level, to a higher energy ...
The oscillator strength is defined by the following relation to the cross section for absorption: [19] = =, where e {\displaystyle e} is the electron charge, m e {\displaystyle m_{e}} is the electron mass, and ϕ ν {\displaystyle \phi _{\nu }} and ϕ ω {\displaystyle \phi _{\omega }} are normalized distribution functions in frequency and ...
Klein–Nishina distribution of scattering-angle cross sections over a range of commonly encountered energies. Electron-photon scattering cross section In particle physics , the Klein–Nishina formula gives the differential cross section (i.e. the "likelihood" and angular distribution) of photons scattered from a single free electron ...
The dominant physical process in x-ray absorption is one where the absorbed photon ejects a core photoelectron from the absorbing atom, leaving behind a core hole. [1] The ejected photoelectron's energy will be equal to that of the absorbed photon minus the binding energy of the initial core state. The atom with the core hole is now excited and ...
In physics, the cross section is a measure of the probability that a specific process will take place in a collision of two particles. For example, the Rutherford cross-section is a measure of probability that an alpha particle will be deflected by a given angle during an interaction with an atomic nucleus.
The oscillator strength for any transition between ground and excited state depends on these coefficients. The absorption cross-section (σ λ) is empirically determined from this oscillator strength and the broadening of the absorption/emission line by collisions, the Doppler effect and the uncertainty principle.
X-ray absorption spectroscopy (XAS) is a widely used technique for determining the local geometric and/or electronic structure of matter. [1] The experiment is usually performed at synchrotron radiation facilities, which provide intense and tunable X-ray beams. Samples can be in the gas phase, solutions, or solids. [2]