13.2.3 - 13.2.4

13.2.3
The nucleus, as a quantum system contains discrete energy levels. Alpha particles have discrete energies along with the gamma ray spectra. Quantum energy being emitted from both are quantized and discrete, only having certain values, and showing that the nucleus itself has discrete nuclear energy levels.

13.2.4
The beta energy spectra is continuous and was not understood before the postulation of the neutrino. As scientists were investigating they discovered that the beta particles had three times less emissions than what was predicted, undermining the basic principles of physics (conservation of energy.) This led to the postulation of the Neutrino. A particle that was almost undetectable and that carried away the missing kinetic energy and momentum present in the reaction. It is neutral with a minute mass, travelling at the speed of light.

During positron decay a proton contained within the nucleus decays into both a neutron and a positron, which are then emitted. Due to neutrinos and anti-neutrinos, the beta emissions form a continuous spectra.