Effects of atomic electrons on nuclear stability and radioactive decay

Despite the energy-space-time scale of nuclear processes considerably differs from that of atomic ones, a lot of experimental evidences for a strong effect of atomic electrons on nuclear processes is documented. In the present paper we analyze how the change of atomic electronic states may influence the rate of nuclear decay and the condition of nuclear stability, and how it may redistribute the channels of nuclear decay. The changes of atomic electronic states may be caused by application of a strong magnetic field. It is known that under full ionization of the atom the bound-state β-decay (i.e. when β-electron does not escape from the atom and occupies the bound atomic state) appears to be energetically preferable in contrast to the case of β-decay of the neutral atom. Our analysis of the database of nuclear masses gives the following conclusion: a number of nuclei are found, which are stable in the neutral atom and should be unstable with respect to bound-state β-decay if the nucleus is bare (i.e. under full ionization of the atom): 163Dy, 193Ir, 205Tl. Under high degree of atom's ionization, the β-stability threshold moves towards larger values of Z, i.e. towards decreasing the neutron/proton ratio in the nucleus. We show that the clearance of electron atomic states in a certain number of atoms whose nucleus emits the delayed neutron may increase the fraction of delayed neutrons. It is also shown, that while considering the nuclear processes - both known and novel ones - which proceed with participation of weak interactions, one has to take into account the mass of electron in spite of its smallness in comparison with the nuclear binding energy. Within the frame of the respectively enhanced accuracy, it is shown that the necessary and sufficient condition of nuclear stability with respect to β-decay and K-capture appears to be the minimum of the mass defect on isobars, that not always coincides with the widespread condition of the minimum of nuclear mass. The major conclusion of the paper is that the potentiality of a hypothetical collective process of low-energy nuclear transformations is shown to be compatible with the known fundamental conservation laws. This claim is suggested by our successful attempt for a phenomenological description of such a process - first of all, by a number of successful qualitative predictions verified by the experiment. Specifically, comparison of the results of our modeling with respective experimental data shows that the known fundamental conservation laws allow the existence of a hypothetical collective process of low-energy nuclear transformations, which may manifest itself in the following way. This process may proceed at small input/output energies per participating atom, namely those of the scale of chemical energies. The final ensembles of chemical elements with values of energy closest to that of the initial ensemble appear to consist of stable isotopes, if the initial ensemble consists of stable isotopes as well. In other words, the success of the proposed phenomenological model may be considered as an indirect evidence for probable collective nature of a hypothetical process of nuclear transformation and, probable importance of weak interactions in describing the above process (more precisely - the importance of proton-neutron transformations due to the known fundamental interactions, namely, weak interaction, or some unknown ones). Elaboration of the proposed model, even without specification of the mechanism of transformation, will allow making preliminary estimates of the expected production of elements from the given input elements, and what is even more important, estimating the relevant input elements to produce requested output elements. (authors)