Cluster radioactivity

Spontaneous emission of particles heavier than a particles is called cluster radioactivity. Theoretical calculations, published since 1980, showed that spontaneous fragmentation of nuclei with atomic numbers Z > 40 by emission of cluster nuclei, such as Li, Be, 20-2S]qg jg energetically possible... 

FIGURE 8.10 Cluster radioactivity of actinide nuclei. By emission of C,. .. big leaps in... 

The thus obtained fission half lives are depicted in the lower part of Figure 8.11. Their distribution as a function of the fragment mass A2 resembles quite well the asymmetric mass distribution. Cluster radioactive decays correspond to the broad peaks around A2 = 20, 30 (200, 210). The confrontation of the calculated fission half lives with experiments is depicted in Figure 8.12. One notices "nearly quantitative" agreement over 20 orders of magnitude, which is—for an ab-initio calculation—remarkable ... 

Poenaru, D.N. and Greiner W. 2011. Cluster radioactivity. In Beck, C. (Ed.). Clusters in Nuclei I, Lecture Notes in Physics 818. Springer, Berlin, Germany, Chapter 1, pp. 1-56. 

Half-lives for proton emission, ot decay, cluster radioactivity, and cold fission processes have been calculated in the framework of an effective liquid drop model by Duarte et al. (2002). The comparison with experimental data shows that the model is very efficient to describe these different decay processes in a unified theoretical framework. 

In the following, exotic nuclear decay modes of heavy nuclei, cluster radioactivities, delayed fission, and spontaneous fission (SF) together with the recent progress on deformation paths toward fission are briefly introduced. 

A summary of cluster radioactivities experimental Q-values, half-lives, Ti/2, and half-lives relative to those of the a decay in terms of the logarithm of T-i/ ITa... 

There are four modes of radioactive decay that are common and that are exhibited by the decay of naturally occurring radionucHdes. These four are a-decay, j3 -decay, electron capture and j3 -decay, and isomeric or y-decay. In the first three of these, the atom is changed from one chemical element to another in the fourth, the atom is unchanged. In addition, there are three modes of decay that occur almost exclusively in synthetic radionucHdes. These are spontaneous fission, delayed-proton emission, and delayed-neutron emission. Lasdy, there are two exotic, and very long-Hved, decay modes. These are cluster emission and double P-decay. In all of these processes, the energy, spin and parity, nucleon number, and lepton number are conserved. Methods of measuring the associated radiations are discussed in Reference 2 specific methods for y-rays are discussed in Reference 1. 

Table 10. Exotic Radioactive Decay and Emissions of Clusters...

Experiments with radioactive cluster compounds ( Au) allowed precise analyses of the particles distribution in the cells. In case of melanoma BLM it was found that 57.5% of the radioactive gold was in the cytoplasma... 

The cell surface contains antigens, which are referred to as CD, which stands for cluster of differentiation. The antibodies are produced against a specific antigen. When administered, usually by an intravenous injection, the antibody binds to the antigen, which may trigger the immune system to result in cell death through complement-mediated cellular toxicity, or the antigen-antibody cell complex may be internalized to the cancer cell, which results in cell death. Monoclonal antibodies also may carry radioactivity, sometimes referred to as hot antibodies, and may be referred to as radioimmunotherapy, so the radioactivity is delivered to the cancer cell. Antibodies that contain no radioactivity are referred to as cold antibodies. 

Metal-metal (M-M) bonds, first noted in the early sixties, occur in several thousand transition-metal compounds [1]. Complex technetium compounds and compounds with M-M bonds (clusters) have been studied more extensively than many other classes of inorganic compounds. Increasing interest in technetium compounds is due to the practical uses of the "mTc isotope, which ranks first among radioactive isotopes used in nuclear medicine diagnostics [2-4]. On the other hand, technetium clusters are an interesting object for theoretical studies, because until recently, they were the only compounds in which the presence of these anomalous chemical bonds was thought possible. 

A model has been developed to calculate the size distributions of the short lived decay products of radon in the indoor environment. In addition to the classical processes like attachment, plate out and ventilation, clustering of condensable species around the radioactive ions, and the neutralization of these ions by recombination and charge transfer are also taken into account. Some examples are presented showing that the latter processes may affect considerably the appearance and amount of the so called unattached fraction, as well as the equilibrium factor. 

Radioactive lateling of this cluster and neutron activation analysis of the g)ld enabled us to determine the extent of Nnding of the cluster to the particles. The results of both analytical methods show that a spacer of minimum length of about 10 A between the -SH group of a ribosomal protein and the N-atom on the cluster is n ed for significant binding. Preliminary experiments indicate that the producte of the derivatization reaction with SOS particles can be crystallized. 

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