Inelastic scattering

In particle physics and chemistry, inelastic scattering is a fundamental scattering process in which the kinetic energy of an incident particle is not conserved. In this scattering process, the energy of the incident particle is lost or gained.

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When an electron is the incident particle, the probability of inelastic scattering, depending on the energy of the incident electron, is usually smaller than that of elastic scattering. Thus in the case of gas electron diffraction, reflection high energy electron diffraction (RHEED), and transmission electron diffraction, because the energy of the incident electron is high, the contribution of inelastic electron scattering can be ignored.

When a photon is the incident particle, the inelastic scattering process is called Raman scattering. In this scattering process, the incident photon interacts with matter (gas, liquid, and solid) and the frequency of the photon is shifted to blue or red. The blue shift can be observed when the internal energy of the matter is transferred to the photon; this process is called anti-Stokes Raman scattering. The red shift can be observed when the partial energy of the photon is changed to the internal energy of the interacting matter; this process is called Stokes Raman scattering.

Inelastic scattering is seen in the interaction between an electron and a photon. When a high energy photon collides with a free electron and transfers energy, the process is called Compton scattering. Furthermore, when an electron with relativistic energy collides with an infrared or visible photon, the electron gives energy to the photon; this process is called inverse-Compton scattering.

Inelastic scattering is common in molecular collisions. Any collision which leads to a chemical reaction will be inelastic, but the term inelastic scattering is reserved for those collisions which do not result in reactions.^[1] There is a transfer of energy between the translational mode (kinetic energy) and rotational and vibrational modes.

References

1. ^ International Union of Pure and Applied Chemistry. "inelastic scattering". Compendium of Chemical Terminology Internet edition.