Cascade fission

A new feature, on which the laser electrodispersion method is based, consists in that the process of cascade fission terminates after the daughter drops reach a nanometer size. As charged drops immersed in plasma become smaller, the electric field on their surface increases, which results in a dramatic increase in the field emission of electrons. After the size of the daughter drops decreases to several nanometers, the flow of electrons emerging from the drop surface starts to exceed that coming in from the plasma. In this case, the drops discharge and become stable, so that the fission terminates. Thus, fission of micrometer and submicrometer drops in the laser torch plasma yields a tremendous number of nanometer drops with narrow size dispersion and a small amount of residues of maternal drops that had not enough time for total fission. 

Fig. 15.1. Scheme of the cascade fission of a charged liquid drop. 

Ternary fission into three fragments of similar mass may proceed in two different ways (Fig. 8.18) (a) is a sequence of two binary fissions, also called cascade fission, whereas (b) illustrates a true ternary fission.. Theoretical considerations lead to the conclusion that, in general, cascade fission is more probable, with the exception of ternary fission at low Z /A values and at low excitation energies. 

Figure 8.18. The two different modes of fission into three fragments (schematic) (a) cascade fission (b) true ternary fission.

Laser electrodispersion (LED) method makes possible to fabricate dense nanostmctured catalysts with unique catalytic properties. In contrast to earlier laser ablation techniques, where nanoparticles were synthesized from vaporized matter, LED is based on the cascade fission of hquid metalhc drops. Fabricated catalysts consist of ensembles of nanoparticles that are uniform in size and shape, amorphous and stable to coagulatioa The catalytic activity of these self-assembled Pt, Ni, Pd, Au and Cu catalysts with extremely low metal content (<10 mass.%) in hydrogenation and hydrodechlorination is several orders of magnitude higher compared to that for separated metal clusters, highly loaded metal films and supported catalysts prepared by usual methods. 

Keywords laser electrodispersion, cascade fission of microdrops, amorphous... 

The elder model of ion formation, the charged-residue model (CRM), assumes the complete desolvation of ions by successive loss of all solvent molecules from droplets that are sufficiently small to contain just one analyte molecule in the end of a cascade of Coulomb fissions. [9,42,84] The charges (protons) of this ultimate droplet are then transferred onto the molecule. This would allow that even large protein molecules can form singly charged ions, and indeed, CRM is supported by this fact. [23]... 

KRU81]). The B strength function for nuclei along the decay back paths [coupled with neutron separation energies (Sn), fission barrier heights (Bf) and B"decay Q-values (Qg)] determines the amount of B delayed fission and neutron emission that occurs during the cascade back to the B stability line. 

Plutonium purification proceeds by reducing the aqueous phase pH that oxidizes the plutonium to Pu" +, which then extracts into the TBP phase. Impurities stay in the aqueous phase. The TBP phase strip-ping/extraction cycle is repeated to complete the plutonium purification. The uranium is purified using the same TBP/nitric acid extraction/stripping cycle. Careful control of the each element s oxidation state in the extraction cascade produces the plant-scale separations of uranium from plutonium of 10 . Fission product decontamination factor was 10. The plutonium and uranium recovery is about 99.9% with 95% of the nitric acid values and 99.7 /o of the organic solvent recycled. ... 

Nishi, K., Yoshida, M., Fujiwara, D., Nishikawa, M., Horinouchi, S., Beppu, T. (1994). Leptomycin B targets a regulatory cascade of ciml, a fission yeast nuclear protein, involved in control of higher order chromosome structure and gene expression. 

The subject of high energy fission has been reviewed by Spence and Ford . High energy fission is pictured as following a cascade process which has left... 

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