Alpha, beta and gamma decay

Alpha Particles and Alpha Decay


Alpha particles are helium nuclei of nuclear origin. It carries 2 unit positive charge and its mass is about four times the mass of hydrogen atom.

Phenomenon of emission of an α particles from a nucleus is called alpha decay

Example: 92U238 →90Th234 + 2He4 + Q

Here, Q = (mX ‒ mY ‒ mHec2


ZXA → z ‒ 2YA ‒ 4 + 2He4 + Q

Beta Particles and Beta Decay

Beta particles are fast moving electrons of nuclear origin. A nucleus that decays spontaneously by emitting an electron or a positron is said to undergo beta decay.

In β‒ decay, an electron an electron is emitted by the nucleus.

Example: 15P32 → 16S32 + e + antineutrino

In βdecay, a positron is emitted by the nucleus.

Example: 11Na22 → e + Neutrino

In beta-minus decay, a neutron transforms into a proton within the nucleus according to, n → p + e + antineutrino

Whereas in beta-plus decay, a proton transforms into neutron (inside the nucleus) by, p → p + e+ + neutrino

Gamma Radiations and Gamma decay

There are energy levels in a nucleus, just like there are energy levels in atoms. When a nucleus is in an excited state, it can make a transition to a lower energy state by the emission of electromagnetic radiation. As the energy differences between levels in a nucleus are of the order of MeV, the photons emitted by the nuclei have MeV energies and are called gamma rays

Energy Level Diagram Showing Emission of Gamma Rays

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