Probing astrophysically important states in Mg nucleus to study neutron sources for the -Process
R. Talwar🇺🇸 · T. Adachi🇯🇵 · G. P. A. Berg🇺🇸 · L. Bin🇯🇵 · S. Bisterzo🇮🇹 · M. Couder🇺🇸 · R. J. deBoer🇺🇸 · X. Fang🇺🇸 · H. Fujita🇯🇵 · Y. Fujita🇯🇵 · J. Gorres🇺🇸 · K. Hatanaka🇯🇵 and 11 other authors
The Ne(,n)Mg reaction is the dominant neutron source for the slow neutron capture process (-process) in massive stars and contributes, together with the C(,n)O, to the production of neutrons for the -process in Asymptotic Giant Branch (AGB) stars. However, the reaction is endothermic and competes directly with the Ne(Mg radiative capture. The uncertainties for both reactions are large owing to the uncertainty in the level structure of Mg near the alpha and neutron separation energies. These uncertainties are affecting the s-process nucleosynthesis calculations in theoretical stellar models. Indirect studies in the past have been successful in determining the energies, -ray and neutron widths of the Mg states in the energy region of interest. But, the high Coulomb barrier hinders a direct measurement of the resonance strengths, which are determined by the -widths for these states. The goal of the present experiments is to identify the critical resonance states and to precisely measure the -widths by transfer techniques . Hence, the -inelastic scattering and -transfer measurements were performed on a solid Mg target and a Ne gas target, respectively, using the Grand Raiden Spectrometer at RCNP, Osaka, Japan. Six levels (E = 10717 keV , 10822 keV, 10951 keV, 11085 keV, 11167 keV and 11317 keV) have been observed above the -threshold in the region of interest (10.61 - 11.32 MeV). The rates are dominated in both reaction channels by the resonance contributions of the states at E = 10951, 11167 and 11317 keV. The E =11167 keV has the most appreciable impact on the () rate and therefore plays an important role for the prediction of the neutron production in s-process environments.