Search for the isovector monopole resonance via the $^{28}$Si($^{10}$Be,$^{10}$B+$\gamma$)$^{28}$Al reaction

The isovector giant monopole resonance (IVGMR) is a fundamental mode of collective oscillation in which the neutron and proton fluids in a nucleus radially expand and contract in an out-of-phase manner. Observation of the IVGMR has been difficult due to the lack of a probe that will excite only its non-spin-flip ($\Delta S=0$) transitions. The IVGMR's spin-transfer ($\Delta S=1$) counterpart, the isovector spin giant monopole resonance, is much more strongly excited at bombarding energies higher than 60 MeV/$u$. By way of the ($^{10}$Be,$^{10}$B+$\gamma$) charge-exchange reaction, the selectivity for the excitation of the IVGMR can be gained. In this probe, the superallowed Fermi transition $^{10}$Be($0^{+}$,g.s.)$\rightarrow$$^{10}$B($0_{1}^{+}$,1.74 MeV,$T=1$) allows a nearly pure isolation of the $\Delta S=0$ component by detecting the 1022 keV gamma rays from the deexcitation of the $^{10}$B. We measured the double differential cross sections for the $^{28}$Si($^{10}$Be,$^{10}$B+$\gamma$) reaction at 100 MeV/$u$ using the large acceptance S800 Spectrometer at the National Superconducting Cyclotron Laboratory with the GRETINA array detecting the gamma rays emitted from the $^{10}$B ejectile. In this presentation, we will report preliminary reults of the IVGMR in $^{28}$Al.