Beta-particle radiation

[1123581321]

Hi,

 

Was wondering with the emission of beta particle radiation - so either an electron or positron, since a positron is the anti-partner of the electron, how can it be emitted from a (normal) matter atom...?

 

Thanks.

[swansont]

A neutron in a nucleus may be in an energy level where it is energetically favorable to change into a proton in order to occupy a lower energy level. There is an interaction involving the weak nuclear force which allows this to happen— an electron and antineutrino are emitted; within the neutron, a down quark is converted to an up quark. Since the neutron is more massive than a proton, this is possible for a free neutron.

 

Similarly, a proton can convert to a neutron, but only within a nucleus which has an excess of protons. In this case a positron and neutrino are emitted, and the resulting neutron occupies a lower energy state than the original proton did.