# How can we have Inelastic scattering?

## Main Question or Discussion Point

Inelastic scattering is the scattering event in which heat is produced. But we know that heat is also due to particles' vibration. Therefore when the vibration is made in target by incident particle, the target would vibrate (in other words, phonons or heat are produced). Thus heat is a type of vibration. So what is the difference between elastic and inelastic scatterings?

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jfizzix
Gold Member
The difference is in whether or not the translational kinetic energy of the scattered particles in conserved. If it is elastic scattering, the kinetic energy of the scattered particles will be the same as that of the incident particles. If not, then the collisions are inelastic.

jfizzix
Gold Member
total energy is always conserved though.

Andy Resnick
Inelastic scattering is the scattering event in which heat is produced. <snip>
Not always: kinetic energy can also be converted into changes of 'internal' energy (vibrational, rotational, electronic, spin) states. This is how He-Ne lasers work, for example.

Ok,thank you very much, But how about inelastic collision? According to the fact that heat is anyhow a type of vibration how can we have inelastic collision?

This internal vibrations are excluded from the computation of the translational kinetic energy of the object as a whole which uses the speed of the center of mass, not the speed of each individual particle. That part of the kinetic energy belongs with the internal energy (thermal energy).

This internal vibrations are excluded from the computation of the translational kinetic energy of the object as a whole which uses the speed of the center of mass, not the speed of each individual particle. That part of the kinetic energy belongs with the internal energy (thermal energy).
By this you mean that: If we have two single particles (such as electron), we would only have elastic collision and inelastic collision is not possible. Ok?

Yes, except that if the energy of the collision is high enough, you would start producing new particles by pair-production and that process would consume part of the kinetic energy, than you would have inelastic collision between electrons.

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