Alpha-decay energies

The effects of a rather distinct deformed shell at = 152 were clearly seen as early as 1954 in the alpha-decay energies of isotopes of californium, einsteinium, and fermium. In fact, a number of authors have suggested that the entire transuranium region is stabilized by shell effects with an influence that increases markedly with atomic number. Thus the effects of shell substmcture lead to an increase in spontaneous fission half-Hves of up to about 15 orders of magnitude for the heavy transuranium elements, the heaviest of which would otherwise have half-Hves of the order of those for a compound nucleus (lO " s or less) and not of milliseconds or longer, as found experimentally. This gives hope for the synthesis and identification of several elements beyond the present heaviest (element 109) and suggest that the peninsula of nuclei with measurable half-Hves may extend up to the island of stabiHty at Z = 114 andA = 184. 

Alpha-decay energies are most precisely measured in magnetic spectrometers. From (2.5) and (2.10) it is calculated that... 

Alpha-decay energies. The a-decay energies of some nuclei around N = 126 are shown in Fig. 2.33. There is a sharp change in the systematic trend at the magic number 126. 

Several different approaches to find a reasonable value for can be found in the literature. One approach by Taagepera and Nurmia [68], valid for even-even nuclei, gives a semiempirical relationship between the half-life in years, the atomic number of the daughter Z and the alpha decay energy in MeV (Eq. 31). 

The metal has a silvery appearance and takes on a yellow tarnish when slightly oxidized. It is chemically reactive. A relatively large piece of plutonium is warm to the touch because of the energy given off in alpha decay. Larger pieces will produce enough heat to boil water. The metal readily dissolves in concentrated hydrochloric acid, hydroiodic acid, or perchloric acid. The metal exhibits six allotropic modifications having various crystalline structures. The densities of these vary from 16.00 to 19.86 g/cms. 

Alpha carbon atoms, 348 Alpha decay, 417, 443 Alpha particle, 417 scattering, 245 Aluminum boiling point, 365 compounds, 102 heat of vaporization, 365 hydration energy, 368 hydroxide, 371 ionization energies, 269, 374 metallic solid, 365 occurrence, 373 properties, 101 preparation, 238. 373 reducing agent, 367 Alums, 403 Americium... 

Alpha decay is characterized by the emission of an alpha particle from the parent nucleus. In this process, energy is released in the form of kinetic energy of the escaping alpha particle and the recoiling daughter nucleus. For example ... 

Alpha decay leads to a decrease of the atomic number by two units, Z — Z — 2, and causes an expansion of the electron shell, as illustrated in Fig. 9.5 for the a decay of radioisotopes of Bi. EHffercnccs in the binding energies arc marked for electrons in the inner shells. Furthermore, there arc two surplus electrons after a decay. However, in the case of a decay the excitation effects due to the change of the atomic number are relatively small compared with the recoil effects that have been discussed in the previous section, with the result that the recoil effects dominate. 

The Working Level (WL) is equal to any combination of the short-lived decay products of Rn in I L of air resulting in the ultimate emission by them of 1.3 x 10 MeV of alpha-particle energy (obtained from 9800 Rn atoms or about 0.5 pCi/L). Equivalent uranium (eU) is U concentration estimated from the Bi concentration (usually determined by gamma-ray spectrometry) assuming secular equilibrium. 

Calculate the energy change in the alpha decay of one °Rn nucleus, in million electron volts and in joules. 

Write balanced nuclear equations for beta decay, positron emission, electron capture, and alpha decay processes and calculate the maximum kinetic energies of particles emitted (Section 19.2, Problems 7-18). 

The nuclide Pu undergoes alpha decay with a half-life of 2.411 X 10 years. An atomic energy worker breathes in 5.0 X 10 " g (5.0 fig) of Pu, which lodges permanently in a lung. 

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