What occurs during the annihilation reaction of a positron?

During the annihilation reaction of a positron, the process is characterized by the interaction between the positron and an electron. When a positron, which is the antimatter counterpart of the electron, encounters an electron, they experience annihilation. This interaction leads to the conversion of their mass into energy, as dictated by Einstein's equation, E=mc².

In this process, both the positron and the electron effectively combine, resulting in the release of energy in the form of photons, typically two gamma rays. These photons are emitted in opposite directions, which is a key principle utilized in positron emission tomography (PET) for imaging. The likelihood that this annihilation will occur increases significantly when the positron slows down in proximity to the electron, allowing for this critical interaction to take place.

The other options do not accurately describe the annihilation reaction. A positron is not absorbed by the nucleus, nor does it split into neutrons, nor is there a transformation into photons without the combination with an electron. It is the combination with an electron that leads to the emission of photons, reinforcing the correct response regarding what happens during the annihilation process.