Beta-plus

Neutrino (V)—A neutral particle of infinitesimally small rest mass emitted during beta plus or beta minus decay. This particle accounts for conservation of energy in beta plus and beta minus decays. It plays no role in damage from radiation. 

The second type of decay, called beta decay (fi decay), comes in three forms, termed beta-plus, beta-minus, and electron capture. All three involve emission or capture of an electron or a positron (a pcirticle with the tiny mass of an electron but with a positive chcirge), and all three also change the atomic number of the daughter atom. 

Beta-plus In beta-plus decay, a proton in the nucleus decays into a neutron, a positron ( Je), and a tiny, weakly interacting pcirticle called a neutrino (v). This decay decreases the atomic number by 1. The mass number, however, does not change. Both protons and neutrons cire nucleons (pcirticles in the nucleus), after all, each contributing 1 atomic mass unit. The general pattern of beta-plus decay is shown here ... 

Beta-minus Beta-minus decay essentially mirrors beta-plus decay. A neutron converts into a proton, emitting an electron and an anftneutrino (which has the same symbol as a neutrino except for the line on top). Particle and antiparticle pairs such as neutrinos and antineutrinos are a complicated physics topic, so we ll keep it basic here by saying that a neutrino and an antineutrino would annihilate one another if they ever touched, but they re otherwise very similar. Again, the mass number remains the same after decay because the number of nucleons remains the same. However, the atomic number increases by 1 because the number of protons increases by 1 ... 

Ga (half-life, 68.3 min (3+ (beta plus), 88% E(3+ maximum, 1.900 keV) is obtained in 0.5 mL of 0.5 N HC1 from a 68Ge/68Ga radionuclide generator developed by the Radiochemistry Department of the German Cancer Research Center. 

Positron emission—A proton turns into a neutron plus a positively charged electron known as a positron or beta-plus particle. As with electron emission there s another particle included this time a neutrino instead of an antineutrino. An isotope of fluorine decays into oxygen as follows ... 

Positron—The positron (sometimes called a beta plus particle ) has the same mass as the electron, but has the opposite charge. 

Beta Plus. [Van Den Bergh Foods] Hydrog. soybean oil, sodium stearoyl lactylate, ethoxylated mono and (figlycerides, bu lhydroquinone fluid shortening for breads. 

Fig. 10-7. Composition and power emission from irradiated U fuel, (o) Power emission. Basis 1 beta particle of 0.35 Mev per disintegration 0.5 gamma photon of 0.7 Mev per disintegration beta power == gamma power = one-half total power, (b) Curie emission, (c) Fractional curie emission all beta emitters (except where noted y, meaning beta plus gamma emission). Key to curves on (c) (1) Te-129Y ...

Beta-plus (/S" ) particle n. A radioactive einis-sion particle) consisting of a positron e. 

Radionuclides are, by definition, unstable and decay by one, or more, of the decay modes alpha, beta-minus, beta-plus, electron capture or spontaneous fission. Although strictly speaking a de-excitation rather than a nuclear decay process, we can include isomeric transition in that list from the mathematical point of view. The amount of a radionuclide in a sample is expressed in Becquerels -numerically equal to the rate of disintegration - the number of disintegrations per second. We refer to this amount as the activity of the sample. Because this amount will change with time we must always specify at what time the activity was measured. 

Positron emission can be thought of as a type of beta emission. It is sometimes referred to as beta-plus emission. 

Note that the first product is also a hydrogen nucleus, but one that contains a neutron as well as a proton and therefore has a mass number of 2. Recall that species that have the same atomic number but different mass numbers are isotopes.The second product is a positron, sometimes referred to as a beta—plus particle. A positron has the same mass as an electron but the opposite charge. The symbol for a particle other than an element... 

In Section 10.1, we discussed the simplest fusion reaction [Equation (10.1)] in which a beta-plus particle—that is, a positron (+i )—is a product. Other common nuclear and subnuclear particles are given in Table 10.1. Having discussed the discovery and some of the chemistry of deuterium and tritium, we are now ready to take a closer look at nuclear processes, particularly those related to hydrogen. 

Note that the nuclear reaction is balanced, as previously described. It turns out that there are two types of beta decay, beta-plus decay (which produces a positron) and beta-minus decay (which produces an ordinary electron). Note, however, that this electron, although indistinguishable from any other electron, is the product of the decay, or the falling apart, of a nucleus. Beta-minus and beta-plus decays are denoted by placing a )8 or a over the arrow. Tritium decays by beta-minus decay, as shown in Equation (10.16) ... 

An example of an isotope that decays by beta-plus emission is boron-8, the longest-lived radioactive isotope of boron. The reaction for its decay is represented in Equation (10.17) ... 

The half-lives of uranium-238 with respect to alpha decay, tritium with respect to beta-minus decay, and boron-8 with respect to beta-plus decay are 4.51 X 10 (4.51 billion) years, 12.3 years, and 0.77 years, respectively. 

Potassium-40 decays via both beta-minus and beta-plus emission. Write a nuclear equation for each process. 

The longest-lived radioactive isotope of oxygen is 0, which decays via beta-plus emission with a half-life of 124 s. Write a nuclear equation for this decay process. 

Other applications of these elements take advantage of their nuclear properties. For example, one prevalent method of establishing the age of early humanoids is the potassium-argon dating procedure developed in the 1950s. Potassium-40 has a half-life of 1.3 billion years and decays by either beta-minus or beta-plus emission, as shown in Equations (12.22) and (12.23) ... 

Note that argon is in significantly greater supply than the others. Why should this be The answer lies in the amount of argon-40 produced by the beta-plus decay of potassium-40. Recall (see p. 343) that this decay scheme has been employed to indirectly determine the age of various hominids like the Australopithecus afarensis called Lucy. Although argon gas remains trapped in some rock samples and is therefore useful for chronometric determinations, most of it escapes into the open atmosphere. 

Beta-plus (P+) Particle n A radioactive emission (particle) consisting of a positron jC. 

Neutrinos are created in nuclear processes and in various elementary particle interactions. The most familiar process is nuclear beta-decay, in which an unstable nucleus simultaneously emits an electron (beta-ray) and a neutrino. This process may be visualized as an unstable nucleus radiating its energy by creating a pair of leptons a neutrino and an electron. It is referred to as beta-minus decay when an electron (e ) is emitted with an antineutrino Ve) or beta-plus decay when a positron (e+) is emitted with a neutrino (Vg). In another beta-decay process, called electron capture, one of the orbital electrons in an atom is absorbed by the nucleus and a neutrino is emitted. Examples of these processes are... 

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