Radiation, beta

As already mentioned in section 6.1, the interaction of p radiation with matter is much weaker than that of a radiation. Whereas a 3 MeV a particle has a range of about 1.7 cm in air and produces several thousand ion pairs per millimetre, a p particle of the same energy covers a distance of about 10 m in air and produces only about 4 ion pairs per millimetre. On the other hand, the electrons are markedly deflected by collisions with other electrons, in contrast to the heavy a. particles, and they therefore exhibit a zig2ag course. 

The absorption of the p particles of by aluminium is plotted in Fig. 6.7. The form of the absorption curve is due to the continuous energy distribution of the P particles and the scattering of the p radiation in the absorber. At the end of the absorption curve a nearly constant intensity of bremsstrahlung (X rays) is observed. By extrapolation of the absorption curve the maximum range Rmax of the P particles can be found. In practice, this extrapolation is carried out by subtraction of the bremsstrahlung and extension of the curve to 10 /q (Fig. 6.7). 

Absorption curves of P and P radiation are very similar. By use of the calibration curve in Fig. 6.8 the maximum energy E,aax of P particles can be determined from their maximum range i max- 

Conversion electrons are monoenergetic and exhibit a nearly linear absorption curve (Fig. 6.9), if their energy is 0.2 MeV. At energies 0.2 MeV the absorption curve deviates more or less from linearity. To obtain the effective range of conversion electrons, the linear part of the absorption curve is extrapolated to the intensity 7 = 0. 

Beta radiation interacts with matter in three different ways  

Beta decay is denoted by the symbol p, (Greek beta) and it s symbolized as e. In many ways, p radiation is the opposite to a radiation. 

P radiation is usually just the emission of an electron, and so it s negatively charged whereas a particles are positively charged however, there s one form of P decay known as p decay, or sometimes positron decay, where a radionuclide emits a positively charged electron known as positron. A 

For example, thorium-234 (90 protons) undergo P decay to render proactinium-234 (91 protons) and an electron. 

In this equation, you can see that P decay has the net effect of changing a neutron into a proton. It s important to remember that this P particle isn t an electron from the atom, but rather formed from the nuclei s neutron when it decayed. A neutron is approximately 1.675 x 10 kg, whereas a proton is only 1.673 x 10 kg, which helps explains how both an electron and a neutron can appear from p decay. 

Another form of p decay includes positron emission, where the nucleus expels positively charged positrons. For example, positron emission from a sodium nucleus looks like this  

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The most widely used experimental method for determining surface excess quantities at the liquid-vapor interface makes use of radioactive tracers. The solute to be studied is labeled with a radioisotope that emits weak beta radiation, such as H, C, or One places a detector close to the surface of the solution and measures the intensity of beta radiation. Since the penetration range of such beta emitters is small (a ut 30 mg/cm for C, with most of the adsorption occurring in the first two-tenths of the range), the measured radioactivity corresponds to the surface region plus only a thin layer of solution (about 0.06 mm for C and even less for H). 

Attenuation of Provides short- or long-term TWA (e.g. up beta radiation to 8 hr, depending on model) of dust or Direct reading fume mass concentration. 

Beta radiation Electron emission from unstable nuclei, 26,30,528 Binary molecular compound, 41-42,190 Binding energy Energy equivalent of the mass defect measure of nuclear stability, 522,523 Bismuth (m) sulfide, 540 Blassie, Michael, 629 Blind staggers, 574 Blister copper, 539 Blood alcohol concentrations, 43t Body-centered cubic cell (BCC) A cubic unit cell with an atom at each comer and one at the center, 246 Bohrmodd Model of the hydrogen atom... 

Benztriazole, derivatives 281 ff 2-(2-Hydroxy-5-niethylphenyl)- 282 2-(2-Hydroxy-3-(l -methylpropyl)-5-tert-butylphenyl- 283 Berberine reagent 44,213 Beryllium cations 144,145,311,312 Besthorn s hydrazone reagent 347 Beta-blockers 74, 299, 301, 426—428 Beta-fronts 126 Beta-radiation 12 Betulae, Extr. 279 Betulic acid 59... 

Alpha and beta radiation, on the other hand, are particles that possess mass and charge. If we set the weight of a hydrogen atom as 1 and the charge on its ion as +1, then the table below gives the corresponding properties of the radioactive emissions known in the early twentieth century. 

A Alpha radiation B Beta radiation C Gamma radiation D Delta radiation... 

Beta radiation is a stream of negatively charged particles, known as beta particles, which have the same mass and electric charge as the electrons. Beta radiation travels in the air longer distances than alpha... 

Radioactive isotopes that decay by the emission of alpha or beta radiation undergo a change in the nature of their nuclei and are converted into isotopes of other elements. The emission of gamma rays, on the other hand, does not change the nature of the nuclei of the radioisotopes from which the rays are emitted. Gamma rays are a form of dissipation of nuclear energy. 

Radiocarbon Counting of beta radiation or amount of carbon-14 Organic matter Textbox 52... 

Methodology of Radiocarbon Dating. The natural concentration of radiocarbon in materials on earth is extremely low add to this the fact that the beta radiation emitted by radiocarbon is very weak, and the conclusion is that the measurement of natural levels of radiocarbon is a rather difficult task. Indeed, very elaborate physical and chemical procedures are required to obtain accurate radiocarbon measurements and dates. 

An older and long-established technique, radiocarbon decay counting, also known as the "conventional" method of radiocarbon dating, is based on detecting and counting the amount of beta radiation emitted in unit time by radiocarbon atoms in a sample of known weight. 

A long time (usually several hours) is required for counting the beta radiation emitted by the disintegrating radiocarbon. 

A nucleus that has an excess of neutrons will undergo neutron to proton transition, a process that may restore the N P ratio but that requires the loss of an electron to convert the neutron to a positively charged proton, and as a result the atomic number increases by one. The particle emitted is a high speed electron known as a negation (P ) and the atom is said to emit beta radiation, e.g. 

Weak beta radiation and alpha particles often cannot penetrate the covering material but the use of a scintillant, which, together with the sample, will dissolve in a suitable solvent, enables a similar technique to be used. Liquid scintillation counters usually consist of two light-shielded photomultiplier... 

The resistance to gamma radiation is excellent without significant degradation after more than 1000 Mrad, exceeding even the behaviour of polystyrene. With alpha and beta radiations, resistance would be higher than 10 000 Mrad. 

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