Elastic scattering of Al-25 + p to explore the resonance structure in Si-26

Abstract

Background: The properties of resonances in Si-26 are important to better constrain the Al-25(p,gamma)Si-26 reaction rate relevant to the synthesis of galactic Al-26(gs) and energy generation in explosive stellar environment at higher temperature. Purpose: Al-25 + p elastic scattering was measured to further constrain and investigate disagreements in resonance parameters for the high-lying excited states of Si-26 with high statistics and without background contamination within the target. Methods: The experiment was performed by bombarding a thick H-2 target with an Al-25 radioactive ion beam. The resonances at excitation energies of 6.6-8.3 MeV in the Si-26 compound nucleus were studied at the low-energy radioactive-ion beam facility CRIB (Center for Nuclear Study Radioactive Ion Beam separator) at the University of Tokyo. Results: Six resonant states were observed and their resonance parameters were extracted by an R-matrix analysis. Our resonance parameters for two levels are in good agreement with the results of previous studies, while for four others, excitation energy, proton partial width, and spin-parity assignment disagree with the results of recent study via elastic scattering of Al-25 + p. Conclusion: The parameters of resonant states in Si-26 determined in the present work for the Al-25(p,gamma)Si-26 reaction rate are consistent with that of the previous result, solving spin-parity assignment discrepancies between experiments, relevant at higher temperatures.