Parent nuclides

The nuclear y-resonance effect in ° Ni was first observed in 1960 by Obenshain and Wegener [2]. However, the practical application to the study of nickel compounds was hampered for several years by (1) the lack of a suitable single-line source, (2) the poor resolution of the overlapping broad hyperfine lines due to the short excited state lifetime, and (3) the difficulties in producing and handling the short-lived Mossbauer sources containing the Co and Cu parent nuclides, respectively. 

Single-line sources are now available which cut down the number of resonance lines in a spectrum and thereby reduce the resolution problems considerably. Since many laboratories have access to electron and ion accelerators to produce the parent nuclides Co and Cu, the major experimental obstacles to Ni spectroscopy have been overcome and a good deal of successful work has been performed in recent years. Moreover, the development of synchrotron radiation instead of conventional Mossbauer sources is of additional advantage for future Mossbauer applications (see below). 

The sources used in Ni Mossbauer work mainly contain Co as the parent nuclide of Ni in a few cases, Cu sources have also been used. Although the half-life of Co is relatively short (99 m), this nuclide is much superior to Cu because it decays via P emission directly to the 67.4 keV Mossbauer level (Fig. 7.2) whereas Cu ti/2 = 3.32 h) decays in a complex way with only about 2.4% populating the 67.4 keV level. There are a number of nuclear reactions leading to Co [4] the most popular ones are Ni(y, p) Co with the bremsstrahlung (about 100 MeV) from an electron accelerator, or Ni(p, a) Co via proton irradiation of Ni in a cyclotron. 

The source preparation for tungsten Mossbauer spectroscopy is in general cumbersome, apart from the production of a, the parent nuclide of The first... 

The two Mossbauer levels of Pt, 99 keV and 130 keV, are populated by either EC of Au(fi/2 = 183 days) or isomeric transition of Pt(fi/2 = 4.1 days). Only a few authors, e.g., [323, 324] reported on the use of Pt, which is produced by thermal neutron activation of " Pt via " Pt(n, y) Pt. The source used in the early measurements by Harris et al. [322, 325] was carrier-free Au diffused into platinum metal. Walcher [326] irradiated natural platinum metal with deuterons to obtain the parent nuclide Au by (d, xn) reactions. After the decay of short-lived isotopes, especially Au(fi/2 = 6.18 days), Au was extracted with ethyl acetate, and the Au/Pt source prepared by induction melting. Buym and Grodzins [323] made use of (a, xn) reactions when bombarding natural iridium with... 

MeV a-particles and used the Au/Ir source after annealing without any further chemical or physical treatment. Commercially available sources are produced via Pt(p, n) Au. The most popular source matrix into which Au is diffused is platinum metal although it has the disadvantage of being a resonant matrix - natural platinum contains 33.6% of Pt. Using copper and iridium foils as host matrices for the Au parent nuclide, Buym et al. [327] observed natural line widths and reasonable resonance absorption of a few percent at 4.2 K. 

T = [(N2) - (N2)] / X2 [(N2) - (Ni)] or T = [(N2/Ni) -(N2/Ni)] / X2 [(N2/N1) - 1], where parentheses denote activities or activity ratios (note that (Ni) = (Ni) because of the long half-life of the parent nuclide and the absence of crystal fractionation). If the (N2/N1) ratio is known, then the residence time can be calculated from the measurement of the (N2/N1) ratio in lavas erupted from the central conduit. An eccentric eruption, whose magma has bypassed the reservoir, may provide a value for the (N2/N1) ratio. 

Since Ra and " Ra are both produced by recoil from the host mineral, it might be assumed that the production rates are equal. However, the relative recoil rates can be adjusted by considering that the parent nuclides near the mineral surface may not be in secular equilibrium due to ejection losses i.e., the activity of Th may be lower than that of Th due to recoil into groundwater of the intermediate nuclide Ra. Krisnaswami et al. (1982) calculated that the recoil rate of " Ra is 70% that of Ra if radionuclides are depleted along the decay chain in this way. 

U/ 32jj activity ratio of -0.8 (equivalent to a Th/U weight ratio of 3.8), and this is often taken to represent that of the host rocks in the absence of direct measurements, although this can of course be substantially different in rocks such as limestones or other sedimentary deposits. If it is assumed that the groundwater profile is in steady state, that weathering and precipitation are not important for these nuclides, and that the parent nuclides ojh and have similar behaviors, then the corresponding terms in... 

Isotope distribution among the different phases of water are generally assumed to mostly depend on the behavior of their respective parent nuclides, in particular on their sorption/solubility properties. For instance, according to Sarin et al. (1990), covariation between ratios and Th/U ratios in Himalayan rivers reflect the preferential... 

IB 58Ni has a mass number of 58 and an atomic number of 28. A positron has a mass number of 0 and an effective atomic number of +1. Emission of a positron has the seeming effect of transforming a proton into a neutron. The parent nuclide must be copper-58. 

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... 

In the above radioactive decays, a parent nuclide shakes itself to become another nuclide or two nuclides. A unidirectional arrow indicates that there is no reverse reaction or if there is any reverse reaction, it is not considered. He produced by the homogeneous reaction (radioactive decay) may subsequently escape into another phase, which would be another kinetic process. 

If a reaction is a one-step reaction, that is, if it occurs on the molecular level as it is written, then the reaction is called an elementary reaction. In an elementary reaction, either the particles collide to produce the product, or a single particle shakes itself to become something different. For example, Reactions 1-1 and 1-2 occur at the atomic scale as they are written. That is, a parent nuclide shakes itself to become a more stable daughter nuclide (or two daughter nuclides). 

Radiation damage to life depends on whether the radioactive parent nuclides are already in the human hody or outside the human hody. If the radioactive nuclides are inside the human body, the damage effect is similar to that on crystal stmctures more massive particles are more damaging. For radioactive nuclides not inside the human body, the more massive particles cannot penetrate much distance, and could be stopped by cloth or paper, and hence do not cause much damage to life tissues. The less massive P-particles and y-rays are much more penetrating and can hence deliver energy to life tissues. 

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