Beta plus decay neutrino plus#

In most practically interesting cases, single beta decay is energetically forbidden for such nuclei, because when β and ββ decays are both allowed, the probability of β decay is (usually) much higher, preventing investigations of very rare ββ decays. Some nuclei can undergo double beta decay (ββ decay) where the charge of the nucleus changes by two units.

Beta plus decay neutrino plus#

One example is 40K, which undergoes all three types of beta decay (beta minus, beta plus and electron capture) with half life of 1.277×10 9 years. In nature, most isotopes are beta stable, but a few exceptions exist with half-lives so long that they have not had enough time to decay since the moment of their nucleosynthesis. It should be noted, that a beta-stable nucleus may undergo other kinds of radioactive decay ( alpha decay, for example). Among them, several nuclides (at least one) are beta stable, because they present local minima of the mass excess: if such a nucleus has ( A, Z) numbers, the neighbour nuclei ( A, Z−1) and ( A, Z+1) have higher mass excess and can beta decay into ( A, Z), but not vice versa. Thus the set of all nuclides with the same A can be introduced these isobaric nuclides may turn into each other via beta decay. For example:īeta decay does not change the number of nucleons A in the nucleus but changes only its charge Z. If the proton and neutron are part of an atomic nucleus, these decay processes transmute one chemical element into another. In all the cases where β + decay is allowed energetically (and the proton is a part of a nucleus with electron shells), it is accompanied by the electron capture process, when an atomic electron is captured by a nucleus with the emission of a neutrino:īut if the energy difference between initial and final states is low (less than 2 m e c 2), then β + decay is not energetically possible, and electron capture is the sole decay mode. The difference between these energies goes into the reaction of converting a proton into a neutron, a positron and a neutrino and into the kinetic energy of these particles. Beta plus decay can only happen inside nuclei when the absolute value of the binding energy of the daughter nucleus is higher than that of the mother nucleus.

So, unlike beta minus decay, beta plus decay cannot occur in isolation, because it requires energy, the mass of the neutron being greater than the mass of the proton. In β + decay, energy is used to convert a proton into a neutron, a positron ( e + ) and a neutrino ( ν e): In β − decay, the weak interaction converts a neutron ( n 0) into a proton ( p +) while emitting an electron ( e −) and an anti-neutrino ( ):Īt the fundamental level (as depicted in the Feynman diagram below), this is due to the conversion of a down quark to an up quark by emission of a W - boson the W - boson subsequently decays into an electron and an anti-neutrino. In the case of electron emission, it is referred to as 'beta minus' (β −), while in the case of a positron emission as 'beta plus' (β +). In nuclear physics, beta decay is a type of radioactive decay in which a beta particle (an electron or a positron) is emitted.