<p>Motivated by recent experimental discoveries [Phys. Lett. B <b>847</b>, 138310 (2023)&#xa0;and Phys. Rev. Lett. <b>132</b>, 072502 (2024)], two-quasiparticle <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\(K^\pi =8^+\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msup> <mi>K</mi> <mi>π</mi> </msup> <mo>=</mo> <msup> <mn>8</mn> <mo>+</mo> </msup> </mrow> </math></EquationSource> </InlineEquation> isomeric structure (related to the neutron <InlineEquation ID="IEq5"> <EquationSource Format="TEX">\(h_{9/2}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>h</mi> <mrow> <mn>9</mn> <mo stretchy="false">/</mo> <mn>2</mn> </mrow> </msub> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq6"> <EquationSource Format="TEX">\(f_{7/2}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>f</mi> <mrow> <mn>7</mn> <mo stretchy="false">/</mo> <mn>2</mn> </mrow> </msub> </math></EquationSource> </InlineEquation> orbitals) in <InlineEquation ID="IEq7"> <EquationSource Format="TEX">\(^{160}_{76}\)</EquationSource> <EquationSource Format="MATHML"><math> <mmultiscripts> <mrow /> <mn>76</mn> <mn>160</mn> </mmultiscripts> </math></EquationSource> </InlineEquation>Os<InlineEquation ID="IEq8"> <EquationSource Format="TEX">\(_{84}\)</EquationSource> <EquationSource Format="MATHML"><math> <mmultiscripts> <mrow /> <mn>84</mn> <mrow /> </mmultiscripts> </math></EquationSource> </InlineEquation>, which lies at the two-proton drip line, has been investigated by means of configuration-constrained potential-energy-surface calculations. Calculated results indicate that, for such an isomer, the excitation energy can be well reproduced and its oblate shape can be enhanced by the polarization effects of the two high-<i>K</i> orbitals. Comparing with experimental data, two sets of the widely used Woods-Saxon parameters, especially the spin-orbit coupling strengths, are evaluated and discussed. It is found that, considering the uncertainty of the spin-orbit coupling strength, the energy crossing or inversion of the <InlineEquation ID="IEq9"> <EquationSource Format="TEX">\(h_{9/2}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>h</mi> <mrow> <mn>9</mn> <mo stretchy="false">/</mo> <mn>2</mn> </mrow> </msub> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq10"> <EquationSource Format="TEX">\(f_{7/2}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>f</mi> <mrow> <mn>7</mn> <mo stretchy="false">/</mo> <mn>2</mn> </mrow> </msub> </math></EquationSource> </InlineEquation> neutron orbitals can occur, which may lead to three kinds of different evolution trends of two-quasiparticle excitation energies with the changing quadrupole deformation <InlineEquation ID="IEq11"> <EquationSource Format="TEX">\(\beta _2\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>β</mi> <mn>2</mn> </msub> </math></EquationSource> </InlineEquation>. With decreasing spin-orbit coupling strength, the structure of the <InlineEquation ID="IEq12"> <EquationSource Format="TEX">\(K^\pi =8^+\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msup> <mi>K</mi> <mi>π</mi> </msup> <mo>=</mo> <msup> <mn>8</mn> <mo>+</mo> </msup> </mrow> </math></EquationSource> </InlineEquation> isomeric state evolves from <InlineEquation ID="IEq13"> <EquationSource Format="TEX">\(\nu h_{9/2}f_{7/2}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>ν</mi> <msub> <mi>h</mi> <mrow> <mn>9</mn> <mo stretchy="false">/</mo> <mn>2</mn> </mrow> </msub> <msub> <mi>f</mi> <mrow> <mn>7</mn> <mo stretchy="false">/</mo> <mn>2</mn> </mrow> </msub> </mrow> </math></EquationSource> </InlineEquation> (<InlineEquation ID="IEq14"> <EquationSource Format="TEX">\(\nu 9/2^-[505] \otimes 7/2^-[503]\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>ν</mi> <mn>9</mn> <mo stretchy="false">/</mo> <msup> <mn>2</mn> <mo>-</mo> </msup> <mrow> <mo stretchy="false">[</mo> <mn>505</mn> <mo stretchy="false">]</mo> </mrow> <mo>⊗</mo> <mn>7</mn> <mo stretchy="false">/</mo> <msup> <mn>2</mn> <mo>-</mo> </msup> <mrow> <mo stretchy="false">[</mo> <mn>503</mn> <mo stretchy="false">]</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation>) to the mixing of <InlineEquation ID="IEq15"> <EquationSource Format="TEX">\(\nu h_{9/2}f_{7/2}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>ν</mi> <msub> <mi>h</mi> <mrow> <mn>9</mn> <mo stretchy="false">/</mo> <mn>2</mn> </mrow> </msub> <msub> <mi>f</mi> <mrow> <mn>7</mn> <mo stretchy="false">/</mo> <mn>2</mn> </mrow> </msub> </mrow> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq16"> <EquationSource Format="TEX">\(\nu h_{9/2}^2\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>ν</mi> <msubsup> <mi>h</mi> <mrow> <mn>9</mn> <mo stretchy="false">/</mo> <mn>2</mn> </mrow> <mn>2</mn> </msubsup> </mrow> </math></EquationSource> </InlineEquation> (<InlineEquation ID="IEq17"> <EquationSource Format="TEX">\(\nu 9/2^-[505] \otimes 7/2^-[514]\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>ν</mi> <mn>9</mn> <mo stretchy="false">/</mo> <msup> <mn>2</mn> <mo>-</mo> </msup> <mrow> <mo stretchy="false">[</mo> <mn>505</mn> <mo stretchy="false">]</mo> </mrow> <mo>⊗</mo> <mn>7</mn> <mo stretchy="false">/</mo> <msup> <mn>2</mn> <mo>-</mo> </msup> <mrow> <mo stretchy="false">[</mo> <mn>514</mn> <mo stretchy="false">]</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation>) to <InlineEquation ID="IEq18"> <EquationSource Format="TEX">\(\nu h_{9/2}^2\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>ν</mi> <msubsup> <mi>h</mi> <mrow> <mn>9</mn> <mo stretchy="false">/</mo> <mn>2</mn> </mrow> <mn>2</mn> </msubsup> </mrow> </math></EquationSource> </InlineEquation>, indicating that its structural probe remains still of interest and an arbitrary assignment may be risky. The related theoretical calculations and experimental evidence, e.g., on the transition properties, are desirable. In addition, similar to that in superheavy nuclei, it is suggested that the stability inversion between high-<i>K</i> isomeric states and ground states might occur in this proton drip-line mass region, e.g., in the hitherto unknown nucleus <InlineEquation ID="IEq19"> <EquationSource Format="TEX">\(^{162}_{78}\)</EquationSource> <EquationSource Format="MATHML"><math> <mmultiscripts> <mrow /> <mn>78</mn> <mn>162</mn> </mmultiscripts> </math></EquationSource> </InlineEquation>Pt<InlineEquation ID="IEq20"> <EquationSource Format="TEX">\(_{84}\)</EquationSource> <EquationSource Format="MATHML"><math> <mmultiscripts> <mrow /> <mn>84</mn> <mrow /> </mmultiscripts> </math></EquationSource> </InlineEquation>.</p>

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Probing the two-quasiparticle \(K^{\pi} =8^{+}\) isomeric structure and enhanced stability in proton-drip-line nuclei

  • Zhen-Zhen Zhang,
  • Hua-Lei Wang,
  • Kui Xiao,
  • Min-Liang Liu

摘要

Motivated by recent experimental discoveries [Phys. Lett. B 847, 138310 (2023) and Phys. Rev. Lett. 132, 072502 (2024)], two-quasiparticle \(K^\pi =8^+\) K π = 8 + isomeric structure (related to the neutron \(h_{9/2}\) h 9 / 2 and \(f_{7/2}\) f 7 / 2 orbitals) in \(^{160}_{76}\) 76 160 Os \(_{84}\) 84 , which lies at the two-proton drip line, has been investigated by means of configuration-constrained potential-energy-surface calculations. Calculated results indicate that, for such an isomer, the excitation energy can be well reproduced and its oblate shape can be enhanced by the polarization effects of the two high-K orbitals. Comparing with experimental data, two sets of the widely used Woods-Saxon parameters, especially the spin-orbit coupling strengths, are evaluated and discussed. It is found that, considering the uncertainty of the spin-orbit coupling strength, the energy crossing or inversion of the \(h_{9/2}\) h 9 / 2 and \(f_{7/2}\) f 7 / 2 neutron orbitals can occur, which may lead to three kinds of different evolution trends of two-quasiparticle excitation energies with the changing quadrupole deformation \(\beta _2\) β 2 . With decreasing spin-orbit coupling strength, the structure of the \(K^\pi =8^+\) K π = 8 + isomeric state evolves from \(\nu h_{9/2}f_{7/2}\) ν h 9 / 2 f 7 / 2 ( \(\nu 9/2^-[505] \otimes 7/2^-[503]\) ν 9 / 2 - [ 505 ] 7 / 2 - [ 503 ] ) to the mixing of \(\nu h_{9/2}f_{7/2}\) ν h 9 / 2 f 7 / 2 and \(\nu h_{9/2}^2\) ν h 9 / 2 2 ( \(\nu 9/2^-[505] \otimes 7/2^-[514]\) ν 9 / 2 - [ 505 ] 7 / 2 - [ 514 ] ) to \(\nu h_{9/2}^2\) ν h 9 / 2 2 , indicating that its structural probe remains still of interest and an arbitrary assignment may be risky. The related theoretical calculations and experimental evidence, e.g., on the transition properties, are desirable. In addition, similar to that in superheavy nuclei, it is suggested that the stability inversion between high-K isomeric states and ground states might occur in this proton drip-line mass region, e.g., in the hitherto unknown nucleus \(^{162}_{78}\) 78 162 Pt \(_{84}\) 84 .