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[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

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Adopted values for the reduced electric quadrupole transition probability, B(E2)↑, from the ground state to the first-excited 2+ state of even–even nuclides are given in Table I. Values of τ, the mean life of the 2+ state; E, the energy; and β, the quadrupole deformation parameter, are also listed there. The ratio of β to the value expected from the single-particle model is presented. The intrinsic quadrupole moment, Q0, is deduced from the B(E2)↑ value. The product E×B(E2)↑ is expressed as a percentage of the energy-weighted total and isoscalar E2 sum-rule strengths.

Table II presents the data on which Table I is based, namely the experimental results for B(E2)↑ values with quoted uncertainties. Information is also given on the quantity measured and the method used. The literature has been covered to November 2000.

The adopted B(E2)↑ values are compared in Table III with the values given by systematics and by various theoretical models. Predictions of unmeasured B(E2)↑ values are also given in Table III.

Transition probability from the ground to the first-excited 2^+ state of even-even nuclides

Microwave photonics with superconducting quantum circuits

In view of the fact that $\ensuremath{\alpha}$ decay and cluster radioactivity are physically analogical processes, we propose a general formula of half-lives and decay energies for $\ensuremath{\alpha}$ decay and cluster radioactivity. This new formula is directly deduced from the WKB barrier penetration probability with some approximations. It is not only simple in form and easy to see the physical meanings but also shows excellent agreement with the experimental values. Moreover, the difference between two sets of parameters to separately describe $\ensuremath{\alpha}$ decay and cluster radioactivity is small. Therefore, we use only one set of adjustable parameters to simultaneously describe the $\ensuremath{\alpha}$ decay and cluster radioactivity data for even-even nuclei. The results are also satisfactory. This indicates that this formula successfully combines the phenomenological laws of $\ensuremath{\alpha}$ decay and cluster radioactivity. We expect it to be a significant step toward a unified phenomenological law of $\ensuremath{\alpha}$ decay and cluster radioactivity.

Unified formula of half-lives for α decay and cluster radioactivity

Experimental data of complex cluster radioactivity $(^{14}\mathrm{C}\text{--}^{34}\mathrm{Si})$ are systematically analyzed and investigated with different models. The half-lives of cluster radioactivity are well reproduced by a new formula between half-lives and decay energies and by a microscopic density-dependent cluster model with the renormalized M3Y nucleon-nucleon interaction. The formula can be considered as a natural extension of both the Geiger-Nuttall law and the Viola-Seaborg formula from simple $\ensuremath{\alpha}$ decay to complex cluster radioactivity where different kinds of clusters are emitted. It is useful for experimentalists to analyze the data of cluster radioactivity. A new linear relationship between the decay energy of cluster radioactivity and the number of $\ensuremath{\alpha}$ particles in the cluster is found where the increase of decay energy for an extra $\ensuremath{\alpha}$ particle is between 15 and 17 MeV. The possible physics behind this new linear relationship is discussed.

New perspective on complex cluster radioactivity of heavy nuclei

A global calculation of favored \ensuremath{\alpha}-decay half-lives of both even-$A$ and odd-$A$ deformed nuclei is carried out in the framework of a deformed version of the density-dependent cluster model (DDCM). The influence of nuclear deformation on \ensuremath{\alpha}-decay half-lives is taken into account in the deformed DDCM. The microscopic potential between the spherical \ensuremath{\alpha} particle and the deformed daughter nucleus is evaluated numerically from the double-folding model by the multipole expansion method. The deformation and orientation dependence of the \ensuremath{\alpha}-core potential is analyzed and discussed. The formulas of the deformed DDCM are presented in detail, and a large number of numerical calculations of medium and heavy nuclei with available data are completed. The total number of \ensuremath{\alpha} emitters calculated in this article is 485, and this covers the nuclei with $Z=52\text{\ensuremath{-}}110$. This is a complete study of \ensuremath{\alpha}-decay half-lives on both even-$A$ and odd-$A$ nuclei with deformed microscopic potentials. The numerical results obtained by the deformed DDCM are in good agreement with the experimental data.

Global calculation of α-decay half-lives with a deformed density-dependent cluster model

The masses of 31 neutron-rich nuclei in the range A = 29-47 have been measured. The precision of 19 masses has been significantly improved and 12 masses were measured for the first time. The neutron-rich Cl, S, and P isotopes are seen to exhibit a change in shell structure around N = 28. Comparison with shell model and relativistic mean field calculations demonstrate that the observed effects arise from deformed prolate ground state configurations associated with shape coexistence. Evidence for shape coexistence is provided by the observation of an isomer in 43S.

Shape coexistence and the N = 28 shell closure far from stability

We systematically investigate the {alpha}-decay and spontaneous fission half-lives for heavy and superheavy nuclei with proton number Z{>=}90. The {alpha}-decay half-lives are obtained by the deformed version of the density-dependent cluster model (DDCM). In the DDCM, the microscopic potential between the {alpha} particle and the daughter nucleus is evaluated numerically from the double-folding model with the M3Y interaction. The influence of the core deformation on the double-folding potential is also properly taken into account by the multipole expansion method. The spontaneous fission half-lives of nuclei from {sup 232}Th to {sup 286}114 are calculated with the parabolic potential approximation by taking nuclear structure effects into account. The agreement between theoretical results and the newly observed data is satisfactory for both {alpha} emitters and spontaneous fission nuclei. The competition between {alpha} decay and spontaneous fission is analyzed in detail and the branching ratios of these two decay modes are predicted for the unknown cases.

Zhongzhou Ren

Papers

Unified formula of half-lives for α decay and cluster radioactivity

New perspective on complex cluster radioactivity of heavy nuclei

Global calculation of α-decay half-lives with a deformed density-dependent cluster model

Shape coexistence and the N = 28 shell closure far from stability

Competition between α decay and spontaneous fission for heavy and superheavy nuclei