What causes a plateau in the cross section of neutrons?

[ORF]

Hello

It seems to me that the nuclei have a flat elastic scattering cross section of neutrons, for neutron energies from eV to MeV.
http://www.nuclear-power.net/wp-con...attering-Cross-section-light-elements-min.png

I thought that maybe it was caused because the neutron interact with the nuclei as a hard sphere, so the (quantum) cross section would be 4*pi*r^2, but the I didn't see the correspondence between the nuclear radii and cross sections.

What causes that flat part in the elastic scattering cross section of neutrons?

Thanks in advance :)

Greetings.

 

[AndyW]

Thank you for your interesting question. The flat part of the elastic scattering cross section of neutrons is caused by the presence of nuclear resonances. These resonances occur when the energy of the neutron matches the energy levels of the nucleus, resulting in a higher probability of elastic scattering. This can be seen in the graph you provided, where there are spikes in the cross section at certain energies.

Additionally, the flat part of the cross section can also be attributed to the fact that the neutron is a neutral particle and does not experience the electromagnetic forces that charged particles do. This means that the cross section for elastic scattering is not affected by the size or shape of the nucleus, resulting in a relatively constant value.

I hope this helps to answer your question. If you have any further inquiries, please don't hesitate to ask. Thank you for your interest in nuclear science.