How is gamma decay produced?

Hint: There are two methods using which the gamma decay is produced. One is natural decay and the other one is artificial decay. The basic element used in both of the methods to produce gamma decay is the unstable nuclei.

Complete answer:
The source of gamma decay is the unstable atomic nuclei. They continuously emit radiations to get into a stable state. The gamma rays or photons or the packets of the electromagnetic energy of the extremely short wavelength get radiated during the gamma emission or decay. In the process of radiation, the nuclei give off energy.
The unstable nuclei can be the products of alpha or beta decay or of some nuclear process such as neutron capture.
In the case of natural gamma decay, the sources are naturally occurring radioactive elements, whereas, in the case of the artificial production of the gamma decay, the sources are nuclear fusion, nuclear fission, etc. These gamma sources are mostly sealed to prevent the radioactive contamination.
The sources of the gamma rays can be the interaction of the cosmic ray particles with the atmospheric particles.
\[\therefore \]The gamma decay is produced by the emission or the radiation of the gamma rays by the unstable atomic nuclei.

Note:
The gamma decay is a type of radioactive decay. The other types of radioactive decay are alpha and beta decay. In the case of gamma decay, the energy in the form of gamma rays gets emitted, whereas, in the case of alpha and beta decay, both the particles and the energy get emitted.