kernbarrière

Kernbarriere is a term used in nuclear physics to describe the potential energy barrier that two atomic nuclei must overcome or tunnel through in order to engage in a nuclear reaction, most notably fusion. The barrier arises from the electrostatic repulsion between positively charged nuclei (the Coulomb barrier) at larger separations, combined with the short-range attractive nuclear force that binds nucleons when they come within about 1 femtometer.

Qualitatively, at separations greater than roughly 1 fm, the Coulomb repulsion raises the potential energy; only when the nuclei approach close enough can the strong nuclear force act to fuse or to cause other interactions. The height of the kernbarriere depends on the reacting species; for light nuclei it is of order a few MeV at closest approach, while for heavy nuclei it can reach tens of MeV.

Reactions occur if the incident energy is sufficient to overcome the barrier or if quantum tunneling allows penetration at sub-barrier energies. In astrophysical environments, tunneling (Gamow tunneling) makes fusion possible at stellar temperatures far below the classical barrier height. The barrier strongly influences reaction cross sections and astrophysical S-factors.

Although commonly discussed in the context of fusion, a related concept is the fission barrier, which is the energy barrier that must be overcome for a heavy nucleus to split into lighter fragments. Kernbarriere thus plays a central role in determining the feasibility and rate of nuclear reactions in both laboratory and astrophysical settings.