Element decay properties

Gas-Phase Chemistry of Superheavy Elements Decay properties from physics experiments ... 

The abundance of a trace element is often too small to be accurately quantihed using conventional analytical methods such as ion chromatography or mass spectrometry. It is possible, however, to precisely determine very low concentrations of a constituent by measuring its radioactive decay properties. In order to understand how U-Th series radionuclides can provide such low-level tracer information, a brief review of the basic principles of radioactive decay and the application of these radionuclides as geochronological tools is useful. " The U-Th decay series together consist of 36 radionuclides that are isotopes (same atomic number, Z, different atomic mass, M) of 10 distinct elements (Figure 1). Some of these are very short-lived (tj j 1 -nd are thus not directly useful as marine tracers. It is the other radioisotopes with half-lives greater than 1 day that are most useful and are the focus of this chapter. 

Examples of large-basis shell-model calculations of Gamow-Teller 6-decay properties of specific interest in the astrophysical s-and r- processes are presented. Numerical results are given for i) the GT-matrix elements for the excited state decays of the unstable s-process nucleus "Tc and ii) the GT-strength function for the neutron-rich nucleus 130Cd, which lies on the r-process path. The results are discussed in conjunction with the astrophysics problems. 

In this section, we present results dealing with the discovery of elements 107 to 112 using cold fusion reactions based on lead and bismuth targets. A detailed presentation and discussion of the decay properties of elements 107 to 109 and of elements 110 to 112 was given in previous reviews [15,20,21], Presently known nuclei are shown in the partial chart of nuclides in Figure 2. 

Astatine is a member of the halogen family, elements in Group 17 (VlIA) of the periodic table. It is one of the rarest elements in the universe. Scientists believe that no more than 25 grams exist on Earth s surface. All isotopes of astatine are radioactive and decay into other elements. For this reason, the element s properties are difficult to study. What is known is that it has properties similar to those of the other halogens—fluorine, chlorine, bromine, and iodine. Because it is so rare, it has essentially... 

The period t = 1/fc is sometimes referred to as the natural lifetime of species A. During time t, the concentration of A decreases to He of its original value. A second period, from r = t to f = 2t, produces an equivalent fractional decrease in concentration to 1/e of the value at the beginning of the second interval, which is (1/e) of [AJo- A more familiar example of this property of exponentials is found in the half-life tu2 of radionuclides. During a period t n, half of the atoms in a sample of a radioactive element decay to products a second period of t i2 reduces the amount of the element to one quarter of its original number, and so on for succeeding periods. Regardless of the time interval chosen, equal elapsed times produce equal fractional decreases in reactant concentration for a first-order process. 

Although a richness of information has been obtained, a number of open questions still remain. For elements which were chemically identified, like Rf or Sg, a more detailed study, both theoretical and experimental, should follow. Elements 109, 110 and 111 are still to be studied experimentally the prerequisites for their successful experimental studies should be similar to those of the lighter transactinides. These include the existence of isotopes long enough for chemical studies, knowledge of their nuclear decay properties, so that they can be positively identified, synthesis reactions with the highest possible cross sections and suitable techniques for their separation. For those elements, predictions of the chemical behaviour are a matter of future research. Especially difficult will be the accurate prediction of adsorption of the heaviest elements on various surfaces, or their precipitation from aqueous solutions by determining electrode potentials. For that, further developments in accurate calculational schemes are needed. More sophisticated methods are needed to treat weak interactions, which are important for physisorption processes. 

The radioactive elements were called radioelements. Lacking names for these radioelements, letters such as X, Y, Z, A, B, etc., were added to the symbol for the primary (i.e. parent) element. Thus, UX was produced from the radioactive decay of uranium, ThX from that of thorium, etc. These new radioelements (UX, ThX, etc.) had chemical properties that were different from the original elements, and could be separated from them through chemical processes such as precipitation, volatilization, electrolytic deposition, etc. The radioactive daughter elements decayed further to form still other elements, symbolized as UY, ThA, etc. A typical decay chain could be written Ra - Rn RaA - RaB - , etc. Fig. 1.2. 

In activation analysis advantage is taken of the fact that the decay properties such as the half-life and the mode and energy of radioactive decay of a particular nuclide serve to identify uniquely that nuclide. The analysis is achieved by the formation of radioactivity through irradiation of the sample either by neutrons or charged particles. Neutron irradiation is by far the more common technique, and hence this method is often referred to as neutron activation analysis, NAA. A major advantage in activation analysis is that it can be used for the simultaneous determination of a number of elements and complex samples. If the counting analysis of the sample is conducted with a Ge-detector and a multichannel analyzer, as many as a dozen or more elements can be measured quantitatively and simultaneously (instrumental NAA, or INAA). 

Among the reasons for the controversies over discovery of elements 104 and 105 are their short half-lives and small production rates that made it necessary to study and identify them online at the accelerators where they were produced on the basis of their decay properties rather than on conventional radioanalytical methods. New radioanalytical techniques had to be developed for unequivocally establishing that a new element had, indeed, been produced. 

Odom, R. W., Strathman, M. D., Buttrill, S. E., and Baumann, S. M. 1990. Nondestructive imaging detectors for energetic particle beams. Nucl Instrum Meth B 44(4), 465 172. Oganessian, Y. T. 2001. The synthesis and decay properties of the heaviest elements. Nucl... 

A number of other similar cases were observed in which seemingly new radioactive elements with unique decay patterns were chemically identical to known elements. The recognition that there were identical elements with differing radioactive decay properties was made in 1909 and 1910 by Svedberg and Soddy respectively. Soddy coined the term isotope ( same place, i.e., in the periodic table) in 1913. 

Andres J, Chauvin AS (2012) Lanthanides luminescence applications. In Atwood DA (ed) The rare earth elements—fundamentals and applications. Wiley, Chichester, pp 135-152 Audi G, Bersillon O, Blachot J, Wapstra AH (2003) The NUBASE evaluation of nuclear and decay properties. Nucl Phys A 729 3-128... 

Abstract This chapter reviews the historical perspective of transuranium elements and the recent progress in the production and study of nuclear properties of transuranium nuclei. Exotic decay properties of heavy nuclei are also introduced. Chemical properties of transuranium elements in aqueous and solid states are summarized based on the actinide concept. For new application of studying transuranium elements, an X-ray absorption fine structure (XAFS) method and computational chemistry are surveyed. 

It should be noted that chemical studies of the transactinides have added a new dimension to heavy element research. While in the physics experiments, for example, in recent experiments using electromagnetic separators, the transactinides are implanted into a Si detector (see O Fig. 19.6 in Chap. 19) and thereafter, their radioactive decay and decay properties are registered. In chemistry experiments, the transactinides are transferred into a chemistry apparatus, subsequently chemically manipulated and chemically characterized, before their radioactive decay is registered. 

It is noteworthy that the decay properties of Rf in Fig. 20.39 are consistent with those observed in the decay chains of element 112 (Hofinann et al. 1996) but deviate from... 

The smallest amount of an element that can be determined depends on the specific activity produced and the minimum activity measurable with sufficient precision. From Equation (10) the activity produced and measured per gram of an element can be calculated. However, the minimum activity that can be measured depends not only on the decay properties of the radionuclide and on the counting equipment, but also on the background of the detector or the Compton continuum on which the photopeak must be detected in gamma spectrometry. Thus the detection limit of an element for specific irradiation-counting conditions is not immutable since it deftends on the presence of other radionuclides. 

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