Pauli postulated the existence of new particle, “Neutrino”
as early as in 1930. According to Pauli, an additional particle called a
neutrino denoted by ‘ν’ is emitted in process of β-decay.
This particle according to Pauli, carries away an amount of energy
equal to difference between the observed energy for a β-particle and maximum
energy of continuous beta spectrum. The principle of conservation of energy is
thus satisfied.
To satisfy Principle of Conservation of Angular Momentum, Neutrino
must be assigned following properties
i) It must have zero charge; because in a β-decay process the
charge is conserved without neutrino. Also if Neutrino is charged, it would
produce ionization which certainly could have been detected. Zero charge in
turn implies negligible magnetic moment.
ii) It must have zero or almost zero mass: the mass-energy balance
of β-decay processes shows that neutrino rest mass is negligible.
iii) It must have a spin of ½: This will satisfy Law of
Conservation of Angular Momentum in β-decay process. Further Neutrino must
be a Fermion, so that nuclear
statistical requirements are fulfilled.
iv) A neutrino has an antiparticle called anti-neutrino which has
zero rest mass, zero charge and spin-1/2.
