A decay parents

More satisfactory results have come from a Pu source which decays by a-emission directly to the Mbssbauer level [4]. An a-decay parent had been previously used in Np work (see below) but the change in the lifetime of the Mbssbauer level from 63 ns in Np to 0-23 ns in gave rise to fears... 

For Np the p, the and the a decay parents are all available. The p source activity (45 d has never been used since it is difficult to produce. Originally... 

The above decay equations apply to the simple case of a radionucHde that is decaying without being replenished. There are many cases in which a nucHde is both being produced and decaying at the same time. One example is the case where one radioactive nucHde is produced by the decay of another nucHde (see Tables 1 and 2). If there are (0) atoms of nucHde 1, the parent, having decay constant A, decays to nucHde 2, the daughter, having decay constant X, then at t = 0 there are (0) such atoms present. Then... 

OC-Decay. In a-decay the parent atom of atomic number Z and mass M emits an a-particle, a He nucleus having Z = 2 and A = 4 and becomes an atom having atomic number Z — 2 and mass A — 4. From the conservation of energy, the energy of the a-particle is... 

Parent Cluster Daughter Cluster decay a-Decay 1 /2 cluster / l/2 d... 

The equation for the decay of a nucleus (parent nucleus - daughter nucleus + radiation) has exactly the same form as a unimolecular elementary reaction (Section 13.7), with an unstable nucleus taking the place of a reactant molecule. This type of decay is expected for a process that does not depend on any external factors but only on the instability of the nucleus. The rate of nuclear decay depends only on the identity of the isotope, not on its chemical form or temperature. 

SRPAC is a scattering variant of time-differential perturbed angular correlation (TDPAC). In TDPAC, an intermediate nuclear level is populated from above after the decay of a radioactive parent. If this nuclear level exhibits hyperfine... 

Calorimetry. Radioactive decay produces heat and the rate of heat production can be used to calculate half-life. If the heat production from a known quantity of a pure parent, P, is measured by calorimetry, and the energy released by each decay is also known, the half-life can be calculated in a manner similar to that of the specific activity approach. Calorimetry has been widely used to assess half-lives and works particularly well for pure a-emitters (Attree et al. 1962). As with the specific activity approach, calibration of the measurement technique and purity of the nuclide are the two biggest problems to overcome. Calorimetry provides the best estimates of the half lives of several U-series nuclides including Pa, Ra, Ac, and °Po (Holden 1990). 

The equation for the growth of a stable daughter from a radioactive parent can be easily derived from Equation (9.6) above, which is the familiar radioactive decay curve. We can write that ... 

Let us consider now species 1 and 2 linked in a decay chain with the parent nuclide 1 being longer-lived than the daughter nuclide 2 (i.e.. A, < A2). After a relatively short time, the terms exp(-A2f) and exp(—A2O become negligible with respect to exp(—Ajf). As a result, equation 11.28 is reduced to... 

Figure 11,8 Composite decay curves for (A) mixtures of independently decaying species, (B) transient equilibrium, (C) secular equilibrium, and (D) nonequilibrium, a composite decay curve b decay curve of longer-lived component (A) and parent radio nuclide (B, C, D) c decay curve of short-lived radionuclide (A) and daughter radionuclide (B, C, D) d daughter radioativity in a pure parent fraction (B, C, D) e total daughter radioactivity in a parent-plus-daughter fraction (B). In all cases, the detection coefficients of the various species are assumed to be identical. From Nuclear and Radiochemistry, G. Friedlander and J. W. Kennedy, Copyright 1956 by John Wiley and Sons. Reprinted by permission of John Wiley and Sons Ltd.

In the environment, thorium and its compounds do not degrade or mineralize like many organic compounds, but instead speciate into different chemical compounds and form radioactive decay products. Analytical methods for the quantification of radioactive decay products, such as radium, radon, polonium and lead are available. However, the decay products of thorium are rarely analyzed in environmental samples. Since radon-220 (thoron, a decay product of thorium-232) is a gas, determination of thoron decay products in some environmental samples may be simpler, and their concentrations may be used as an indirect measure of the parent compound in the environment if a secular equilibrium is reached between thorium-232 and all its decay products. There are few analytical methods that will allow quantification of the speciation products formed as a result of environmental interactions of thorium (e.g., formation of complex). A knowledge of the environmental transformation processes of thorium and the compounds formed as a result is important in the understanding of their transport in environmental media. For example, in aquatic media, formation of soluble complexes will increase thorium mobility, whereas formation of insoluble species will enhance its incorporation into the sediment and limit its mobility. 

Other conditions being equal, the intermediate species with longer half-lives in a decay series have more opportunities to be fractionated from their parents. Hence, in the decay series of two nuclides °Th and Ra have a greater chance to be fractionated. In the decay series, Pa (half-life 32.8 has the greatest chance to be fractionated. In the Th decay series, all the intermediate species have short half-lives (the longest half-life of Intermediates is 5.75 3T for Ra (A, = 0.1205 3 ) and the disturbance of this decay system does not have much utility. That is, the U-series (including U and U series) disequilibrium is much more often applied. Some examples of disturbed decay chain (i.e., fractionation of the intermediate species) are given below ... 

Pa, protactinium, was first identified in 1913 in the decay products of U-238 as the Pa-234 isotope (6.7 h) by Kasimir Fajans and Otto H. Gohring. In 1916, two groups, Otto Hahn and Lisa Meitner, and Frederick Soddy and John A. Cranston, found Pa-231 (10 years) as a decay product of U-235. This isotope is the parent of Ac-227 in the U-235 decay series, hence it was named protactinium (before actinium). Isolation from U extraction sludges yielded over 100 g in 1960. 

Starting with cyclopentanone and a pump pulse delivering two photons at 310 nm, the parent mass at 84 amu grows in intensity and then decays. So does a species at 56 amu, the parent minus CO, with a buildup time of 150 30 fs and a decay time of 700 40 fs. It attains a peak intensity in 300 fs. 

Radioactive decay usually does not immediately lead to a stable end product, but to other unstable nuclei that form a decay series (Kiefer 1990). The most important examples of unstable nuclei are started by very heavy, naturally occurring nuclei. Because the mass number changes only with a decay, all members of a series can be classified according to their mass numbers (see the uranium-238 decay series in Figure 32.2). A total of three natural decay series — formed at the birth of our planet — are named after their parent isotope Th, and (Figure 32.3). Several shorter decay series also exist. For example, Sr decays with a Tb 1/2 of 28 years by [3 emission to °Y, which in turn disintegrates (P emission) with a Tb 1/2 of 64 h to the stable °Zr (Kiefer 1990). Other examples of known radionuclides since the Earth s origin include " °K and Rb. In hazard assessments, all members of a decay series must be considered. 

Equation (8.3) is the basic equation that describes all radioactive decay processes. It gives the number of atoms (N) of a radioactive parent isotope remaining at any time t from a starting number N0 at time t = 0. 

Equation (8.5) gives the number of stable radiogenic daughter atoms ( > ) at any time t formed by decay of a radioactive parent whose initial abundance at / - 0 was N0. 

Substituting Equation (8.6) into (8.7) gives the basic equation that is used to calculate a date for a rock or mineral from the decay of a radioactive parent to a stable daughter ... 

The fact that there were three basic decay processes (and their names) was discovered by Rutherford. He showed that all three processes occur in a sample of decaying natural uranium (and its daughters). The emitted radiations were designated a, (3, and y to denote the penetrating power of the different radiation types. Further research has shown that in a decay, a heavy nucleus spontaneously emits a 4He nucleus (an a particle). The emitted a particles are monoenergetic, and, as a result of the decay, the parent nucleus loses two protons and two neutrons and is transformed into a new nuclide. All nuclei with Z > 83 are unstable with respect to this decay mode. 

Use the one-body theory of a decay to estimate the half-life of 224Ra for decay by emission of a 14C ion or a 4He ion. The measured half-life for the 14C decay mode is 10-9 relative to the 4He decay mode. Estimate the relative preformation factors for the a particle and 14C nucleus in the parent nuclide. 

The general form of (3 decay of a heavy parent nucleus,71Z, can be written as ... 

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