Proton disintegration

Atoms with the same number of protons but a different number of neutrons are called isotopes. To identify an isotope we use the symbol E, where E is the element s atomic symbol, Z is the element s atomic number (which is the number of protons), and A is the element s atomic mass number (which is the sum of the number of protons and neutrons). Although isotopes of a given element have the same chemical properties, their nuclear properties are different. The most important difference between isotopes is their stability. The nuclear configuration of a stable isotope remains constant with time. Unstable isotopes, however, spontaneously disintegrate, emitting radioactive particles as they transform into a more stable form. 

We can use Fig. 17.13 to predict the type of disintegration that a radioactive nuclide is likely to undergo. Nuclei that lie above the band of stability are neutron rich they have a high proportion of neutrons. These nuclei tend to decay in such a way that the final n/p ratio is closer to that found in the band of stability. For example, a l4C nucleus can reach a more stable state by ejecting a (3 particle, which reduces the n/p ratio as a result of the conversion of a neutron into a proton (Fig. 17.15) ... 

Blackett discovered that the process was not one of disintegration, but one of integration only two tracks were seen after the interaction occurred, meaning that the alpha particle was absorbed as the proton was ejected. The resulting nucleus was a heavy isotope of oxygen. 

Since all Rutherford could know from his scintillation experiments was that alpha particles infrequently caused nitrogen nuclei to emit protons—he could not see the actual interaction—he had assumed it was a disintegration process. Only the cloud chamber could provide a visual representation of the transmutation process itself and give physicists the chance to discover the intricacies of the exchange. 

Conversely, nuclei that contain an excess of protons undergo proton to neutron transition with the emission of a positively charged beta particle known as a positron Q8+) and with the reduction of the atomic number by one. A positron has only a very short existence, combining immediately with an electron of a nearby atom. The two particles disintegrate in the process with the emission of two gamma rays, e.g. 

Francium occurs as a result of the disintegration of actinium. Francium is found in uranium minerals, and can be made artificially by bombarding thorium with protons. It is the most unstable of the first 101 elements. 

In physics, speculative ideas often begin to seem much more reasonable when there is a theory to explain them. In 1933 Fermi advanced just such a theory, proposing that the electron and the neutrino were spontaneously created at the moment that a radioactive disintegration took place. At the same time, one of the neutrons in the nucleus was changed into a proton. Fermi showed that electron-neutrino production could be explained if one assumed the existence of a new force (now called the weak force). He concluded that the mass of the neutrino was probably near zero. This would explain why it hadn t been detected. 

Nuclei lying above the belt of stability are richer in neutrons and hence they disintegrate is such a manner that one of their neutrons is converted into a protons i.e.,... 

The nuclei lying below the zone of stability are deficient in neutrons and hence disintegrate in such a way that one of their protons is converted into a neutrons. The conversion of a proton into a neutron can be done by any of the following two ways... 

Other nuclei having higher number of protons or neutrons disintegrate by (a). 

Background Radiation amount of natural radiation detected in the absence of nonnatural radioactive sources Base a substance that yields hydroxide ions in solution or accepts protons Becquerel SI unit for activity equal to one disintegration per second, abbreviated Bq... 

Gamma-ray from disintegration of beryllium by Deuterons and Protons) 3) K. Lark-Horowitz et al, PhysRev 48, 100(1935) (Gamma rays from nitrogen bombarded with Deuterons) 4) R.G. Herb et al, PhysRev 51, 691—98(1937) (Gamma rays from light... 

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