Alpha decay in electron surrounding
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EI Theory
Alpha Decay in Electron Surrounding S. Yu. Igashov1) and Yu. M. Tchuvil’sky2) Received January 14, 2013
Abstract—The influence of atomic electron shells on the constant of alpha decay of heavy and mediummass nuclei was considered in detail. A method for simultaneously taking into account the change in the potential-barrier shape and the effect of reflection of a diverging Coulomb wave in the classically allowed region was developed. The ratios of decay probabilities per unit time for a bare nucleus and the respective neutral atom were found for some alpha-decaying isotopes. DOI: 10.1134/S1063778813120090
1. INTRODUCTION The transmutation of long-lived radioactive isotopes is one of the pressing problems in nuclearphysics applications. Methods that could exert an effect on radioactive materials have been developed along various lines of research. A wide variety of such methods is not exhausted by schemes that employ beams of neutrons, protons, and other particles; also, there are methods that do not involve beams and whose basic idea consists in affecting the decay process by changing environmental conditions. So far, searches for possible ways to implement this idea in practice have not led to considerable advances. Nevertheless, some interesting results concerning the effect on the probabilities of beta decay accompanied by a low energy deposition were obtained in [1, 2]. This was attained by ionizing atoms. A substantial decrease in the lifetime of a low-lying excited state in the case where the energy of the respective transition is nearly coincident with the energy of an allowed transition of the same multipolarity in the electron shell is yet another interesting effect [3, 4]. It is noteworthy that conditions under which the rate of these processes becomes higher arise very rarely. The alpha-decay process seems less sensitive to such external effects because of a high value (about 20 MeV) of the potential-barrier height, which is an energy characteristic of this process. This is the reason why the alpha-decay process attracts less attention in what is concerned with acting on it via affecting the electron shell. Nevertheless, the problem of exerting an effect on α decay did not escape the view of researchers, and the studies reported in [5, 6] 1)
All-Russia Research Institute of Automatics (FSUE VNIIA), Sushchevskaya ul. 22, Moscow, 127055 Russia. 2) Skobeltsyn Institute of Nuclear Physics, Moscow State University, Moscow, 119991 Russia.
are evidence of this. Moreover, interesting results were obtained in [7]. It should be recalled that the alpha-decay width of 212 Po was found there to take different values upon implanting the primary source of 220 Rn into lead and nickel. The measured ratio of decay constants for nuclei implanted into these host materials proved to be 0.2%, its confidence level being 95%. Thus, it is of great interest to study theoretically the effect of the ambient medium on the alpha-decay rate. In the course of the present investigation, we have calculated the ratio of the decay width for
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