Emitting nuclei

Fame G (1986) Principles of Isotope Geology, Second Edition. John Wiley and Sons, New York Fleischer RL, Raabe OG (1975) Recoiling alpha-emitting nuclei. Mechanisms for uranium-series disequilibrium. Geochim Cosmochim Acta 42 973-978 Goldstein SJ, Murrell MT, Williams RW (1993) Pa and h chronology of mid-ocean ridge basalts. Earth Planet Sci Lett 115 151-159... 

Application of these formulas show that the ranges of decay a particles in solids are very short. A sheet of paper will stop the a particles from most radioactive sources. a-Emitting nuclei are not external radiation hazards, but, because of their high LET, they do represent significant inhalation or ingestion hazards. 

Fleischer R. L. and Raabe O. G. (1978) Recoiling alpha-emitting nuclei—mechanisms for uranium series disequilibrium. Geochim. Cosmochim. Acta 42, 973-978. 

RiON and Telegdi [26] to measure the lifetimes of gamma emitting nuclei. Lifetimes between 2.5 X10" sec and 8x10" sec have been so determined. 

Recently Dasgupta-Schubert and Reyes (2007) proposed a new generalized liquid- drop a-decay formula, which was based on experimental data of 373 a-emitting nuclei. According to this formula... 

Before the discovery of the Mossbauer effeci some successful experiments on nuclear resonance absorption in the gas phase had been carried out utilizing the Doppler effeci. High velocities were required (w 10 -10 ms" ). This could be achieved either by mounting a source of emitting nuclei on a high speed rotor or by heating the source and the absorber, so that some overlap of the lines could take place. 

Fig. 11 Fluorescence of pollen grain from Hippeastrum hybridum stained with azulene 10-5 (left, bright lightening of cell wall and less intensive emitted nucleus in centre) or pollen tube stained with colchicine 1CT7 M (right, lightening parts of pollen tube may be tubulinbinding sites).

The generally smooth variation of Qa with Z, A of the emitting nucleus and the two-body nature of a decay can be used to deduce masses of unknown nuclei. One tool in this effort is the concept of closed decay cycles (Fig. 7.3). Consider the a and (3 decays connecting j7Np,, 721 Am, 1 Pu, and IpU. By conservation of energy, one can state that the sum of the decay energies around the cycle connecting these nuclei must be zero (within experimental uncertainty). In those cases where experimental data or reliable estimates are available for three branches of the cycle, the fourth can be calculated by difference. 

Thus, the nucleus is not an effective antenna due to its small size compared to the wavelength of the radiation, y Rays are in the long wavelength limit and are not very sensitive to the detailed internal structure of the emitting nucleus. 

So we see that the rates depend very strongly on the energy of the photon and on the size (mass number) of the emitting nucleus. If we consider the specific hypothetical case of a 1-MeV transition in a medium mass nucleus, A = 100, the ratio of transition rates is... 

In 1958, Rudolph Mossbauer (1) discovered that y-ray emission without loss of energy from recoil of the nucleus could be achieved by incorporating the emitting nucleus in a crystal lattice. The phenomenon is known as the "Mossbauer effect. ... 

From these equations we can calculate the kinetic energy of the Th daughter to be 0.072 MeV, while that of the a-particle is 4.202 MeV. Because of the large mass differmce between the a-emitting nucleus and the helium atom, almost all of the energy is carried away with the a-particle. 

It should be pointed out that although the jS particle is an electron, the emitting nucleus does not contain electrons. As we shall see later in this chapter, a given quantity of... 

It should be noted that a different value of X belongs to each different value of Ea- Thus the effective A (as well as the effective T1/2) for an a-emitting nucleus is determined by the sum of partial decay constants XA,-. (Note that this is a special type of branching decay consisting of a branches only.)... 

However, this simple picture holds only for the hypothetical case in which the two nuclei are in the same chemical surroundings and are held in fixed positions. In reality, the emitted 7 photon has momentum E lc, which leads to recoil of the emitting nucleus due to conservation of momentum. 

Gamma rays are electromagnetic radiation similar to x-rays, though more energetic. Since the energy of gamma radiation is often a well-defined property of the emitting nucleus, it may be used in some cases for the qualitative and quantitative analysis of radionuclides. 

All elements of atomic number greater than 83 exhibit radioactive decay K, Rb, Ir and a few other light elements emit p particles. The heavy elements decay through various isotopes until a stable nucleus is reached. Known half-lives range from seconds to 10 years. 

The decay of radioisotopes iavolves both the decay modes of the nucleus and the associated radiations that are emitted from the nucleus. In addition, the resulting excitation of the atomic electrons, the deexcitation of the atom, and the radiations associated with these processes all play a role. Some of the atomic processes, such as the emission of K x-rays, are inherently independent of the nuclear processes that cause them. There are others, such as internal conversion, where the nuclear and atomic processes are closely related. 

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