Kärnmättnad

Kärnmättnad, often translated as nuclear saturation, is a concept in nuclear physics describing a fundamental property of atomic nuclei. It refers to the observation that the binding energy per nucleon (proton or neutron) in a nucleus reaches a maximum and then levels off for nuclei heavier than a certain size. This suggests that each nucleon interacts with only a limited number of its neighbors, rather than with all other nucleons in the nucleus.

This limited range of the nuclear force is a key aspect of kärnmättnad. The strong nuclear force, which binds nucleons together, is very powerful but only acts over very short distances, roughly the size of a nucleus. As a nucleus grows larger, nucleons in the interior are effectively surrounded by other nucleons and experience the full attractive force. However, nucleons on the surface have fewer neighbors to interact with, leading to a lower binding energy per nucleon for very heavy nuclei compared to those in the middle of the binding energy curve.

The phenomenon of kärnmättnad explains why very large nuclei tend to be unstable. If the attractive force is not strong enough to hold all the nucleons together against the repulsive electrostatic force between protons, the nucleus can undergo fission. The concept is crucial for understanding nuclear stability, the process of nuclear fission, and the behavior of nuclear matter. It is a cornerstone of the liquid drop model of the nucleus, which uses this saturation property to explain nuclear binding energies.