Terminal nuclide

The nuclides of each modular group are spread along 11 festoons that terminate in a radioactive nuclide at each end. Nuclides on the high-ratio side decay by positron emission or electron capture those on the low-ratio side by /3-emission. All nuclides with A > 209 decay by cr-emission. The 81 naturally stable elements have, on average, 3 isotopes each. The predicted 100 elements on the cosmic scale, by the same reckoning, correspond to 300 isotopes. 

Due to the topology of the island, superheavy nuclei should decay by spontaneous fission, either immediately or after a sequence of other decay steps. In a detailed theoretical exploration [12] of the Z-N plane around the island, the longest-lived nuclide again turned out to be Z=110, A=184, decaying with 3xl09 y half-life by a-particle emission to 290108. From there, two subsequent (T-transitions should lead via 290109 to 290110, where the chain should terminate by spontaneous fission with 140 d half-life. The doubly magic 298114, half-life 790 y, should also decay into 290110 by two a-particle emissions via 294l 12 as the intermediate. 

Because the range of nuclidic stability is bounded by fractions that derive from Fibonacci numbers, it probably means that nuclear stability relates directly to the golden mean. To demonstrate this relationship it is noted that the plot of A vs Z, shown in figure 13 for the A(mod4) = 0 series of nuclides, separates into linear sections of constant neutron excess (A — 2Z) and slope 2. Each section terminates at both ends in a radioactive nuclide. The range of stability for each section follows directly from... 

With elements of short half-life, the sensitivity of the method, besides being dependent on the flux and activation cross section, will also depend on the time which must elapse between the termination of activation and the measurement of the activity. With short-lived nuclides this period frequently determines the over-all sensitivity of the method. 

Intensity ratios of photons emitted from some of radioactive nuclides are known to vary with environmental conditions under which the sources are placed. Such phenomena are interesting to frmdamental researchers from the viewpoint of exploring the causes of their occurrence. In the cases of electron capture (EC) and isomeric transition (IT) decays, efforts have been devoted mainly to < Ung the termining factors for changes of photon intensity ratios (K /K, etc.) in detail. 

MAS) is an invaluable approach for observing local silicon environments on the silica surface. H NMR approaches distinguish clustered (hydrogen-bonded) and isolated surface silanols. Correlations between Si and H NMR behaviors in silicas have led to detailed structural models of the silica surface based on intersections of OH-terminated 100 and 111 faces of -cristobalite. Other nuclides (e.g., H, C,... 

Uranium and thorium are not stable they decay mainly by alpha-particle emission to nuclides that themselves are radioactive. Natural uranium is composed of three long-lived isotopes, a smaller proportion of and an even smaller proportion of the decay-series daughter of Natural thorium has one single isotope, Th. Each of these nuchdes decays to an unstable daughter leading, in turn, to a whole series of nuclides that terminate in one or other of the stable isotopes of lead. Under normal circumstances, in a natural material, the U/ U ratio will be fixed and aU nuclides in each of the series will be in equilibrium. 

By the end of 1987 the reactor core was completely assembled with advanced FAs. Loss-of-cladding integrity events virtually terminated resulting in substantial reduction in fission product activity in the reactor gas plenum. The increase of caesium nuclide concentration in the primary system had also stopped. 

Dubnium (Z = 105) cannot be produced directly in " Ca-induced reactions, but long-lived isotopes occur in the decay chains of some of the heavier reaction products. The isotopes Db Ti/2 — 29 h) and Db Tia — 1.2 h) are the terminating SF activities of the decay chains derived from 115 and 115, respectively. These nuclides are produced in Am( Ca,xn) reactions with x = 3 and X = 4, respectively, with corresponding effective production cross sections of 8 pb and 2 pb, [8, 285, 286, 354]. Presently, it cannot be excluded that the SF... 

The isotope that can be produced in the largest quantities is Fm. It is also the nuclide of highest atomic and mass numbers ever isolated from either reactor- or thermonuclear-produced materials. The neutron-production chain essentially terminates at mass 257 owing to the very short half-lives of the heavier isotopes. 

The chain of radioactive decay that begins with continues through a number of steps of a and j8 emission until it eventually terminates with a stable isotope of lead— 82 1. The entire scheme is outlin in Figure 25-2. All naturally occurring radioactive nuclides of high atomic number belong to one of three radioactive decay series the uranium series just described, the thorium series, or the actinium series. (The actinium series actually begins with uranium-235, which was once called actino-uranium.)... 

All naturally occurring radioactive nuclides of high atomic number are members of a radioactive decay series that originates with a long-lived isotope of high atomic number and terminates with a stable isotope, such as o Pb (Fig. 25-2). 

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