We investigate the Coulomb dipole excitation (CDE) of neutron-rich carbon isotopes, focusing on <InlineEquation ID="IEq1"> <EquationSource Format="TEX">$^{15}$</EquationSource> <EquationSource Format="MATHML"><math> <mmultiscripts> <mrow /> <mrow /> <mn>15</mn> </mmultiscripts> </math></EquationSource> </InlineEquation>C and <InlineEquation ID="IEq2"> <EquationSource Format="TEX">$^{19}$</EquationSource> <EquationSource Format="MATHML"><math> <mmultiscripts> <mrow /> <mrow /> <mn>19</mn> </mmultiscripts> </math></EquationSource> </InlineEquation>C, which consist of a core nucleus and one valence neutron. The Coulomb dipole strength distribution <InlineEquation ID="IEq3"> <EquationSource Format="TEX">$dB (E1) / dE_{\text {x}}$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>d</mi> <mi>B</mi> <mrow> <mo stretchy="false">(</mo> <mi>E</mi> <mn>1</mn> <mo stretchy="false">)</mo> </mrow> <mo stretchy="false">/</mo> <mi>d</mi> <msub> <mi>E</mi> <mtext>x</mtext> </msub> </mrow> </math></EquationSource> </InlineEquation> is extracted from experimental Coulomb dissociation cross sections using both general and relativistic calculations of virtual photon numbers. Despite similar beam energies, the dissociation cross section of <InlineEquation ID="IEq4"> <EquationSource Format="TEX">$^{19}$</EquationSource> <EquationSource Format="MATHML"><math> <mmultiscripts> <mrow /> <mrow /> <mn>19</mn> </mmultiscripts> </math></EquationSource> </InlineEquation>C + Pb is significantly larger than that of <InlineEquation ID="IEq5"> <EquationSource Format="TEX">$^{15}$</EquationSource> <EquationSource Format="MATHML"><math> <mmultiscripts> <mrow /> <mrow /> <mn>15</mn> </mmultiscripts> </math></EquationSource> </InlineEquation>C + Pb, reflecting their difference in neutron separation energy. We also compute theoretical strength distributions using a simple model involving the spectroscopic factor S and the potential radius <InlineEquation ID="IEq6"> <EquationSource Format="TEX">$r_{0}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>r</mi> <mn>0</mn> </msub> </math></EquationSource> </InlineEquation>, achieving good agreement with the experimental data. The extracted parameters (S, <InlineEquation ID="IEq7"> <EquationSource Format="TEX">$r_{0}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>r</mi> <mn>0</mn> </msub> </math></EquationSource> </InlineEquation>) are reasonable within physical expectations. This study confirms the importance of low neutron separation energy in enhancing Coulomb breakup reaction and provides a useful framework for understanding dipole excitation mechanisms in weakly bound neutron-rich nuclei. In particular, the Coulomb dipole excitation (CDE) potential, which incorporates the Coulomb dipole strength distribution, plays a crucial role in describing the Coulomb breakup of weakly bound neutron-rich nuclei.

Coulomb dipole strength distribution of neutron-rich carbon isotopes

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发表日期：

2025年9月29日

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Ki-Seok Choi,
W. Y. So

摘要

We investigate the Coulomb dipole excitation (CDE) of neutron-rich carbon isotopes, focusing on $^{15}$ $^{15}$ C and $^{19}$ $^{19}$ C, which consist of a core nucleus and one valence neutron. The Coulomb dipole strength distribution $dB (E1) / dE_{\text {x}}$ $d B (E 1) / d E_{x}$ is extracted from experimental Coulomb dissociation cross sections using both general and relativistic calculations of virtual photon numbers. Despite similar beam energies, the dissociation cross section of $^{19}$ $^{19}$ C + Pb is significantly larger than that of $^{15}$ $^{15}$ C + Pb, reflecting their difference in neutron separation energy. We also compute theoretical strength distributions using a simple model involving the spectroscopic factor S and the potential radius $r_{0}$ $r_{0}$ , achieving good agreement with the experimental data. The extracted parameters (S, $r_{0}$ $r_{0}$ ) are reasonable within physical expectations. This study confirms the importance of low neutron separation energy in enhancing Coulomb breakup reaction and provides a useful framework for understanding dipole excitation mechanisms in weakly bound neutron-rich nuclei. In particular, the Coulomb dipole excitation (CDE) potential, which incorporates the Coulomb dipole strength distribution, plays a crucial role in describing the Coulomb breakup of weakly bound neutron-rich nuclei.