Constraining The ²²Mg??,p?²⁵Al Reaction At Stellar Energies Using The ²⁵Al?p,p?²⁵Al Measurement

We performed the measurement of ²⁵Al+p resonant elastic scattering to experimentally examine the ²²Mg??,p?²⁵Al stellar thermonuclear reaction rate in type I x-ray bursts.These bursts?XRBs?are characterized by sudden dramatic increases in X-ray luminosity,and the triple-?reaction,?p-process?the breakout reaction?and rp-process will happen during the bursts.The reaction rates of the?p-process have a direct effect on the rise time of the light curve of XRBs and can even influence its overall shape.Among all the breakout reactions,the ²²Mg??,p?²⁵Al reaction is thought to be the most sensitive one to the burst light curve in the multi-zone x-ray burst model according to Cyburt's calculation.However,very little is known about the compound nucleus ²⁶Si nor the reaction rate itself.As such,the ²²Mg??,p?²⁵Al reaction rate is presently estimated by the Hauser-Feshbach statistical model;Therefore,the studies of this key reaction are of great nuclear astrophysical implication to understand the energy generation and nucleosynthesis in the explosive stellar environments.The experiment was performed using CRIB?CNS Radioactive Ion Beam separator?at the Center for Nuclear Study?CNS?of the University of Tokyo.An 142 MeV ²⁵Al radioactive ion beam was produced and bombarded an 150?m thick?CH₂?_n target.The recoiled light particles were detected with three Micron silicon?E-E telescopes centered at angles of?_lab?0°,22°and 23°with respect to the beam line,respectively.The ²⁵Al+p elastic-scattering excitation functions were reconstructed with a thick-target method and inverse-kinematics technique.13 resonances in ²⁶Si were observed,and their resonant parameters including energy,spin-parity and decay width have been determined through an R-matrix analysis.Six natural-parity states above the?-emission threshold are found,and they will contribute a lot to the reaction rate.The key²²Mg??,p?²⁵Al reaction rates associated with XRBs are determined experimentally for the first time by using the resonant information of the compound nucleus ²⁶Si.