Internal conversion of nuclear transition in the 235mU–C60−nXn molecules and related compounds

Abstract

The internal conversion of nuclear transition in the 235 U atom is considered. The low-energy γ−quanta (E γ ≈ 76.8 eV ) are emitted during the E3−transition from the excited state (I = ( 1 2 ) + ) of the 235 U nucleus to its ground state (I = ( 7 2 ) − ). The decay rate of this 235m U isomer (E ≈ 76.8 eV ) noticeably depends upon the chemical composition and actual physical conditions (i.e. temperature T and pressure p). By varying such a composition and physical conditions one can change the life-time of the 235m U isomer to relatively large/small values. A specific attention is given to the fullerene molecules containing the central 235 U atom. It is shown that the decay rate λ of the 235m U isomer in the 235m U @C 60−n X n molecules and related compounds can differ significantly from the values obtained for isolated 235 U atoms. Some applications of this effect are considered.As is well known the rate of nuclear reactions and processes is usually independent of the chemical background and physical conditions. In particular, the transition rate between two arbitrary nuclear states cannot depend upon the chemical environment and temperature (or pressure) of the considered experimental sample. However, in some cases the nuclear transition energies can be relatively small. If such an energy is comparable to the energy of corresponding atomic levels, then the nuclear transition can proceed by conversion of the emitted γ−quanta into electron shells of the considered atom (Akhiezer and Beresteskii (1965) [1]). Obviously, the most interesting case is the conversion of nuclear transition to the outer electron shells of atoms. In these cases one can change, in principle, the observed nuclear conversion rate by varying the chemical environment and/or physical conditions. Such a situation can be found in some heavy atoms, e.g., in the 235 U atom.This effect was already experimentally demonstrated for the 235m U-isomer (Mévergnies (1969), (1972), Zhudov et al (1979) [16], [17], [21]). The 235m U-isomer (E ≈ 76.8 eV ±0.5 eV (Zhudov et al [21])) is extensively produced by α-decay of 239 P u in the core of nuclear warheads and reactors. This isomer is the first excited state (I = ( 1 2 ) + ) of the 235 U nucleus which is only ≈ 76.8 eV above its ground state (I = ( 7 2 ) − ). The corresponding (nuclear) E3−transition to the ground state of the 235 U nucleus (Grechukhin and Soldatov (1976) [6]) usually proceeds as an internal conversion of the nuclear transition to the outer electron shells (i.e. to the 5f 5/2 , 5f 7/2 , 6s 1/2 , 6p 1/2 , 6p 3/2 , 6d 3/2 , 6d 5/2 , 7s 1/2 shells) of the 235 U atom. The half-life of the 235m U isomer is ≈ 26 min (Zhudov et al (1979) [21]). In earlier experiments the nuclei of 235m U-isomer were implanted (Mévergnies (1969) [16]) into various metallic foils. The considered cases (Mévergnies (1969) [16]) included the Au, P t, Cu, Ni, V foils. The decay rate λ of the 235m U isomer was measured in each of these cases. The maximal deviation between the results obtained with different metals was fou...

Accurate computations of bound state properties in three- and four-electron atomic systems in the basis of multi-dimensional gaussoids

“…It is interesting to note that analogous result (3 % -6 % differences as maximum) can be predicted for other nuclear processes which are influenced by variations in the chemical enviroment, e.g., for the excitation of the 235 U nucleus which also depends upon chemical enviroment [22] - [25]. It is well known (see, e.g., [24]) that the 235 U nucleus has an excited state with the energy ≈ 75 -77 eV .…”

“…In general, such an excited state arises after excitation of a single electron from the 1s 2 2s 2 electron configuration, which correspond to the ground state, or 'core', for short. It is clear that the It is interesting to note that analogous result (3 % -6 % differences as maximum) can be predicted for other nuclear processes which are influenced by variations in the chemical enviroment, e.g., for the excitation of the 235 U nucleus which also depends upon chemical enviroment [22] - [25]. It is well known (see, e.g., [24]) that the of the atomic nucleus and electron (with index i).…”

“…In Eq. (1) and everywhere below in this work we shall assume that (ij) = (ji) = (12), (13), (14), (15), (23), (24), (25), (34), (35) and (45), for four-electron atomic systems and particle 5 means the atomic nucleus. Analogously, for three-electron atomic systems we have (ij) = (ji) = (12), (13), (14), (23), (24) and (34), where particle 4 is the atomic nucleus.…”

Properties of negatively charged lithium ions and evaluation of the half-life of ${}^{7}$Be atom(s)

“…It is interesting to note that analogous result (3 % -6 % differences as maximum) can be predicted for other nuclear processes which are influenced by variations in the chemical enviroment, e.g., for the excitation of the 235 U nucleus which also depends upon chemical enviroment [15] - [18]. It is well known (see, e.g., [17]) that the 235 U nucleus has an excited state with the energy ≈ 75 -77 eV .…”