Photodisintegration in a core-collapse supernova undoes hundreds of thousands of years of nuclear fusion by splitting the iron nuclei into helium nuclei and neutrons.

Photodisintegration occurs when a high-energy photon is absorbed by an atomic nucleus. The nucleus splits to form lighter elements, releasing a neutron, proton or alpha particle in the process.

During the core-collapse of a supernova, photodisintegration undoes hundreds of thousands of years of nuclear fusion by splitting the iron nuclei into helium nuclei and neutrons.

γ + ⁵⁶Fe → 13⁴He + 4n

These helium nuclei are in turn split into protons and neutrons, the basic building blocks of elements, also through photodisintegration.

γ + ⁴He → 2p⁺ + 2n