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: The ${}^{12}\mathrm{C}(\alpha ,\gamma ){}^{16}\mathrm{O}$reaction, determining the survival of carbon in red giants, is of interest for nuclear reaction theory and nuclear astrophysics. A specific feature of the ${}^{16}\mathrm{O}$nuclear structure is the presence of two subthreshold bound states, (6.92 MeV, $2^{+}$) and (7.12 MeV, $1^{-}$), that dominate the behavior of the low-energy $S$factor. The strength of these subthreshold states is determined by their asymptotic normalization coefficients (ANCs), which need to be known with high accuracy. : The objective of this research is to examine how the subthreshold and ground-state ANCs impact the low-energy $S$factor, especially at the key astrophysical energy of $300\mathrm{keV}$. The $S$factors are calculated within the framework of the $R$-matrix method using the code. Our total $S$factor takes into account the $E1$and $E2$transitions to the ground state of ${}^{16}\mathrm{O}$including the interference of the subthreshold and higher resonances, which also interfere with the corresponding direct captures, and cascade radiative captures to the ground state of ${}^{16}\mathrm{O}$through four subthreshold states: $0_2^{+},3^{-},2^{+}$, and $1^{-}$. To evaluate the impact of subthreshold ANCs on the low-energy $S$factor, we employ two sets of the ANCs. The first selection, which offers higher ANC values, is attained through the extrapolation process [Blokhintsev , ]. The set with low ANC values was employed by deBoer []. A detailed comparison of the $S$factors at the most effective astrophysical energy of 300 keV is provided, along with an investigation into how the ground-state ANC affects this $S$factor. : The contribution to the total $E1$and $E2S$factors from the corresponding subthreshold resonances at $300\mathrm{keV}$are $(71–74)\%$and $(102–103)\%$, respectively. The correlation of the uncertainties of the subthreshold ANCs with the $E1$and $E2S\left(300\mathrm{keV}\right)$factors is found. The $E1$transition of the subthreshold resonance $1^{-}$does not depend on the ground-state ANC but interferes constructively with a broad $(9.585\mathrm{MeV};1^{-})$resonance giving (for the present subthreshold ANC) an additional $26\%$contribution to the total $E1S\left(300\mathrm{keV}\right)$factor. Interference of the $E2$transition through the subthreshold resonance $2^{+}$with direct capture is almost negligible for small ground-state ANC of $58{\mathrm{fm}}^{-1/2}$. However, its interference with direct capture for higher ground-state ANC of $337{\mathrm{fm}}^{-1/2}$is significant and destructive, contributing $-27\%$. The low-energy $S_{E2}\left(300\mathrm{keV}\right)$factor experiences a smaller increase when both subthfreshold and the ground-state ANCs rise together due to their anticorrelation, compared to when only the subthreshold ANCs increase. Published by the American Physical Society2024 

The Black Hills, in western South Dakota and eastern Wyoming, were formed by Laramide orogeny deformation that was focused on a Precambrian suture along the eastern margin of the Wyoming Craton. Uplift of the Black Hills primarily took place by the development of monoclines on the eastern and western flanks of the Black Hills: west-vergent monoclines in the west and east-vergent monoclines in the east. Although the exhumed metamorphic core of the Black Hills contains abundant Precambrian structures that could have been reactivated during the Laramide orogeny, it remains unclear if the monoclines formed above reactivated basement structures. We present new balanced cross section modeling focused on the White Gates monocline along the eastern margin of the Black Hills to test whether it records reactivation of Precambrian basement structures. To better determine the geometry of the White Gates Monocline, we collected 22 bedding attitude measurements from the upper Deadwood and the Pahasapa formations along an 1,723-meter-long transect across the strike of the fold axis. We forward modeled monocline development related to slip on blind thrusts in three dip orientations: 30° (Andersonian thrust fault), 45° (maximum resolved shear stress), and 70° (orientation of nearby basement fabrics). Preliminary model results reveal that the 70° fault dip angle produces fold geometries most consistent with the geometry of the White Gate monocline. This result suggests that the reactivation of Precambrian fabrics during the Laramide orogeny influenced the formation of the White Gates monocline. Elsewhere in the Precambrian core of the Black Hills, conjugate thrust faults inferred to be Laramide age clearly cross-cut basement fabrics, which suggests that the role of structural reactivation in Laramide deformation varies spatially throughout the Black Hills. 

Here we report on the direct measurement of the resonance strengths of the $E_{\mathrm{R}}^{\mathrm{lab}}=647\mathrm{keV}$and 1842 keV resonances in the ${}^{40}\mathrm{Ca}(p,\gamma ){}^{41}\mathrm{Sc}$reaction. At novae temperatures, $0.2<T_9<0.7$, the ${}^{40}\mathrm{Ca}(p,\gamma ){}^{41}\mathrm{Sc}$reaction is governed by the low energy resonance at $E_{\mathrm{R}}^{\mathrm{lab}}=647\mathrm{keV}$, whereas the $E_{\mathrm{R}}^{\mathrm{lab}}=1842\mathrm{keV}$resonance serves as a normalization standard for nuclear reaction experiments within the astrophysically relevant energy range. For the $E_{\mathrm{R}}^{\mathrm{lab}}=647\mathrm{keV}$resonance, we obtain a resonance strength $\omega \gamma =(2.51\pm 0.{09}_{\mathrm{stat}}\pm 0.{22}_{\mathrm{syst}})\mathrm{meV}$, with an uncertainty a factor of 2.5 smaller than the previous direct measurement value. For the $E_{\mathrm{R}}^{\mathrm{lab}}=1842\mathrm{keV}$resonance, we obtain a resonance strength $\omega \gamma =(0.148\pm 0.{006}_{\mathrm{stat}}\pm 0.{013}_{\mathrm{syst}})\mathrm{eV}$, which is consistent with previous studies but deviates by $2\sigma$from the most recent measurement. Our results suggest ${}^{40}\mathrm{Ca}$to be a strong waiting point in the nucleosynthesis path of oxygen-neon (ONe) novae. Published by the American Physical Society2025 

Abstract The interplay and correlation between the $$^{22}$$ 22 Ne $$(\alpha ,\gamma )^{26}$$ ( α , γ ) 26 Mg and the competing $$^{22}$$ 22 Ne $$(\alpha ,n)^{25}$$ ( α , n ) 25 Mg reaction plays an important role for the interpretation of the $$^{22}$$ 22 Ne $$(\alpha ,n)^{25}$$ ( α , n ) 25 Mg reaction as a neutron source in the s - and n -processes. This paper provides a summary and new data on the $$\alpha $$ α -cluster and single-particle structure of the compound nucleus $$^{26}$$ 26 Mg and the impact on the reaction rate of these two competing processes in stellar helium burning environments.