Gamma decay.

Gamma decay

A nucleus can exist in states whose energies are higher than that of its ground state, as an atom can. An excited nucleus is denoted by an asterisk on its usual symbol. The excited nucleus return to its ground state by emitting photon whose energy corresponds to the energy difference between initial and final states in the transition involved. The photons emitted by the nucleus have energy in the range of several MeV and is traditionally called gamma decay.

Unlike, alpha decay and beta decay, the parent nucleus does not undergo any physical change in the process, daughter and parent nuclei are the same. Most of the time, gamma decay occurs after the radioactive nuclei have undergone an alpha or a beta decay. The alpha and beta decays leave the daughter nuclei in an excited state. From the excited state, the daughter nuclei can get back to the ground state by emitting one or more high energy gamma rays.

The relationship between decay and energy level is shown in figure below

Beta decay and Gamma decay.

Thus gamma decay is the emission of electromagnetic radiation of an extremely high frequency i.e. very high energy, giving out excess energy in order to stabilize the unstable nucleus.

As an alternative to gamma decay, an excited nucleus can return to its ground state by losing the excitation energy to an atomic electron nearby and this process is known as internal conversion.

The excited nucleus have short half life but some of them have long half life as long as several hours.

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