Beta-plus decay can only happen inside nuclei when the absolute value of the binding energy of the daughter nucleus is greater than that of the parent nucleus, i . e ., the daughter nucleus is a lower-energy state.
12.
A strong shell effect can be seen : as a rule the shortest value of the half-life is obtained when the daughter nucleus has a magic number of neutrons ( N d = 126 ) and / or protons ( Z d = 82 ).
13.
In 1882 Flemming observed the longitudinal splitting of chromosomes in the dividing nucleus and concluded that each daughter nucleus received half of each of the chromosomes of the mother nucleus : then by the early 20th century it was found that the number of chromosomes in a given species is constant.
14.
The consequence of these two effects is that much of the beta feeding to the higher energy levels of the daughter nucleus is not detected, so less ?I i is subtracted from the I T, and the energy levels are incorrectly assigned more I ? than they really have:
15.
In some cases, the gamma emission spectrum of the daughter nucleus is quite simple, ( e . g . / ) while in other cases, such as with ( / and / ), the gamma emission spectrum is complex, revealing that a series of nuclear energy levels exist.
16.
However, decay cannot occur in an isolated proton because it requires energy due to the mass of the neutron being greater than the mass of the proton . decay can only happen inside nuclei when the daughter nucleus has a greater binding energy ( and therefore a lower total energy ) than the mother nucleus.
17.
Thus, the only type of nuclei that are longer lived and undergo proton or neutron emission are in the class of beta-delayed decays, where first the isospin of one nucleon is reversed ( proton to neutron or vice versa ) via beta-decay, and then if the particle separation energy is non-positive, the daughter nucleus will undergo particle decay.
18.
In nuclear fission events the nuclei may break into any combination of lighter nuclei, but the most common event is not fission to equal mass nuclei of about mass 120; the most common event ( depending on isotope and process ) is a slightly unequal fission in which one daughter nucleus has a mass of about 90 to 100 "'u "'and the other the remaining 130 to 140 "'u " '.
