Background: Halo structure is an interesting exotic configuration developed in some light weakly bound nuclei, where a valence particle orbits a nuclear core. Signatures of halo structure can be observed in the angular distributions of the elastic scattering induced by these nuclei at energies around the Coulomb barrier. There are some well-studied reactions with neutron-rich halo nuclei, such as ${}^6\mathrm{He}$ and ${}^{11}\mathrm{Li}$. However, the information is scarce on the proton-rich side. Recent works confirm the halo structure in the ${}^8\mathrm{B}$ nuclei but still lack more experimental studies for other proton-halo candidates, such as ${}^{12}\mathrm{N}$ and ${}^{17}\mathrm{F}$.

Purpose: In this work, we report experimental data for the elastic scattering of ${}^{12}\mathrm{N}$ on ${}^{197}\mathrm{Au}$ target at $E_{\text{lab}}=70$ MeV. The ${}^{12}\mathrm{N}$ is a proton-rich nucleus with proton separation energy $S_p=600$ keV, which is higher than the ${}^8\mathrm{B}$ ($S_p=137$ keV) and almost the same as the ${}^{17}\mathrm{F}$ ($S_p=601$ keV).

Methods: Data were obtained at the Cyclotron Institute of Texas A&M University where the ${}^{12}\mathrm{N}$ radioactive beam was produced by the momentum achromatic recoil spectrometer. The calculation of the optical model was used to fit the measured angular distribution for the elastic scattering and to obtain the reaction cross section ${\sigma }_R$. We also performed continuum discretized coupled-channel calculations to compare with the experimental data.

Results: The angular distribution of the elastic cross sections exhibits a suppression of the Fresnel peak. From the fitting of the optical model, we obtain the total reaction cross section, ${\sigma }_R=1269\pm 41$ mb. The agreement between the CDCC calculation and the experimental elastic scattering data is limited and the breakdown does not exhaust the measured ${\sigma }_R$.

Conclusions: The resulting reduced reaction cross section ${\sigma }_{\text{Red}}$ for ${}^{12}\mathrm{N}+{}^{197}\mathrm{Au}$ is large and comparable to the one obtained for the ${}^8\mathrm{B}+{}^{208}\mathrm{Pb}$ system. This suggests a strong decoupling of the valence proton from the core because of the low binding energy and a dynamic polarization effect. More research is required to estimate the contribution of core excitation.

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• Elastic scattering reactions
• Low & intermediate energy heavy-ion reactions
• Nuclear reactions
• Optical, coupled-channel & distorted wave models