Nuclear astrophysics with radioactive ions at FAIR

The nucleosynthesis of elements beyond iron is dominated by neutron captures in the s and r processes. However, 32 stable, proton-rich isotopes cannot be formed during those processes, because they are shielded from the s-process flow and r-process, β-decay chains. These nuclei are attributed to the p and rp process. For all those processes, current research in nuclear astrophysics addresses the need for more precise reaction data involving radioactive isotopes. Depending on the particular reaction, direct or inverse kinematics, forward or time-reversed direction are investigated to determine or at least to constrain the desired reaction cross sections. The Facility for Antiproton and Ion Research (FAIR) will offer unique, unprecedented opportunities to investigate many of the important reactions. The high yield of radioactive isotopes, even far away from the valley of stability, allows the investigation of isotopes involved in processes as exotic as the r or rp processes

Photo-response of the

The electric E1 and magnetic M1 dipole responses of the $$N=Z$$ nucleus $$^{24}$$Mg were investigated in an inelastic photon scattering experiment. The 13.0 MeV electrons, which were used to produce the unpolarised bremsstrahlung in the entrance channel of the $$^{24}$$Mg($$\gamma ,\gamma ^{\prime }$$) reaction, were delivered by the ELBE accelerator of the Helmholtz-Zentrum Dresden-Rossendorf. The collimated bremsstrahlung photons excited one $$J^{\pi }=1^-$$, four $$J^{\pi }=1^+$$, and six $$J^{\pi }=2^+$$ states in $$^{24}$$Mg. De-excitation $$\gamma$$ rays were detected using the four high-purity germanium detectors of the $$\gamma$$ELBE setup, which is dedicated to nuclear resonance fluorescence experiments. In the energy region up to 13.0 MeV a total $$B(M1)\uparrow = 2.7(3)~\mu _N^2$$ is observed, but this $$N=Z$$ nucleus exhibits only marginal E1 strength of less than $$\sum B(E1)\uparrow \le 0.61 \times 10^{-3}$$ e$$^2 \,$$fm$$^2$$. The $$B(\varPi 1, 1^{\pi }_i \rightarrow 2^+_1)/B(\varPi 1, 1^{\pi }_i \rightarrow 0^+_{gs})$$ branching ratios in combination with the expected results from the Alaga rules demonstrate that K is a good approximative quantum number for $$^{24}$$Mg. The use of the known $$\rho ^2(E0, 0^+_2 \rightarrow 0^+_{gs})$$ strength and the measured $$B(M1, 1^+ \rightarrow 0^+_2)/B(M1, 1^+ \rightarrow 0^+_{gs})$$ branching ratio of the 10.712 MeV $$1^+$$ level allows, in a two-state mixing model, an extraction of the difference $$\varDelta \beta _2^2$$ between the prolate ground-state structure and shape-coexisting superdeformed structure built upon the 6432-keV $$0^+_2$$ level

Nuclear astrophysics with radioactive ions at FAIR

The nucleosynthesis of elements beyond iron is dominated by neutron captures in the s and r processes. However, 32 stable, proton-rich isotopes cannot be formed during those processes, because they are shielded from the s-process flow and r-process beta-decay chains. These nuclei are attributed to the p and rp process. For all those processes, current research in nuclear astrophysics addresses the need for more precise reaction data involving radioactive isotopes. Depending on the particular reaction, direct or inverse kinematics, forward or time-reversed direction are investigated to determine or at least to constrain the desired reaction cross sections. The Facility for Antiproton and Ion Research (FAIR) will offer unique, unprecedented opportunities to investigate many of the important reactions. The high yield of radioactive isotopes, even far away from the valley of stability, allows the investigation of isotopes involved in processes as exotic as the r or rp processes