Single-atom decay chains

A typical decay chain of with daughter decays illustrating the method of identification of a new species by single-atom decay sequences (Miinzenberg et al. 1981a). Note that lifetimes of the individual nuclei fluctuate according to the "rules" of exponential distribution (seeO Sect. 9.4.4 in Chap. 9, Vol. 1)... 

Smalley and co-workers have probed intramolecular vibrational relaxation by viewing the yields and the time-dependence of the fluorescence from Sj in alkylated benzenes. They focus attention on those ring modes whose vibrational frequencies are unshifted by alkylation these are vibrations with nodes at the alkylated ring carbon atom. The absorption lines are sharp, but as the alkyl chain is lengthened, the emission spectrum develops a broad relaxed component, while the intensity of the sharp unrelaxed resonance fluorescence diminishes in intensity as the intensity of the relaxed spectrum increases. The time-dependence of the relaxed and unrelaxed emission is found to be a single exponential decay, so unfortunately, the rapid intramolecular dephasing decay has not yet been followed. 

Seaborgium (Z = 106) cannot be produced directly in " Ca-induced reactions, as it would require a radon target. The 1.9-min isotope Sg occurs in the decay chains arising from Cn and Fl, best produced in the reaction " Pu(" Ca,3n) [316]. The a-decay branch of the intermediate nuclide Ds is only 10%, so the effective production cross section is reduced from 4 pb to 0.4 pb. The 0.4-s isotope Sg is the decay daughter of Hs produced in the Ra( Ca,4n) reaction [133]. A single atom of Sg has been reported in the Fl decay chain, with a decay time of 2 min [353]. The nuclides produced in the " Cm( Ne,5n)... 

Meitnerium (Z = 109) has been produced only indirectly in Ca-induced reactions. A single atom of 8-s Mt has been observed as a member of the 17 decay chain, produced in the Bk(" Ca,3n) reaction [356, 357]. The isotopes... 

Darmstadtium (Z = 110) has been produced only indirectly in " Ca-induced reactions, though neutron-deficient isotopes could arise in irradiations of thorium targets. A single atom of Ds has been reported in the decay chain of F1, with a decay interval of 8 ms [353]. The 13-s SF isotope Ds is the terminal member (see Hs, above) of the F1 decay chain, produced in the " Pu(" Ca,3n) reaction [331, 349, 358-361]. It is the only known Ds isotope that is appropriate for radiochemical studies. The 0.2-s isotope Ds is a member of the F1 decay chain, best produced in the " PuC Ca,3n) reaction [316]. 

Several radionuclides, radioactive isotopes that decay to noble gases, are listed in Table 1. In a radioactive decay, the radioactive isotope is referred to as the parenf isotope, while the decay product, the noble gas isotope, is referred to as the daughter isotope. In some cases listed, there is more than one mode of decay possible. In other cases, a single decay starts a chain that will ultimately produce several noble gas atoms. To take both into account, the yield (the number of noble gas atoms produced for each parent atom) is also given. Finally, radionuclides that fission may produce any of the several different isotopes of Xe in a characteristic spectrum (Table 2). All of the systems listed, with the exception of the decay of U and Th to Xe, have been exploited in extraterrestrial samples at one time or another. 

We are mainly concerned with the product Xj (produced at rate k), which is assumed to be radioactive, decaying in a single step or via a chain of decays to a final stable nuclide. The number of radioactive product atoms N of Xj present at any time t is the difference betwe the total number of product atoms formed and the number of radioactive decays that have occurred in time d/. This leads to the difierential equation... 

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