Collision between photon and atom

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Photon absorption is primarily considered an inelastic process, as it involves the transfer of energy from the photon to the atom, resulting in a change in the atom's energy state. Under resonant conditions, the absorption can be viewed as elastic scattering, depending on the decay channels of the excited electron. The definition of elastic collisions implies that the total energy remains constant, which does not hold true for photon absorption. If a photon is absorbed and another photon of the same energy is emitted immediately, the overall process may be regarded as elastic. Ultimately, the classification of photon absorption depends on the specific conditions and context of the interaction.
kmarinas86
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Is photon absorption an elastic or inelastic collision? neither?
 
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Under resonant conditions you can look at the absorption process as an elastic scattering event and as an inelastic one while off resonance. On resonance it also dependends on what decay channels the excited electron has.
 
kmarinas86 said:
Is photon absorption an elastic or inelastic collision? neither?
The term "elastic collision" usually refers to a two-body scattering where each body has the same final energy in the center of mass system as its initial energy. With this definition, absorption is an inelastic process.
 
kmarinas86 said:
Is photon absorption an elastic or inelastic collision? neither?
If the photon is "absorbed" it means that its energy is totally or partially transferred to the absorbing system, so the process it's inelastic by definition. However, if another photon of the same energy is emitted immediately after the absorption, the overall process can be considered as elastic.
 

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