${}^{\mathbf{26}}$Si excited states via one-neutron removal from a ${}^{\mathbf{27}}$Si radioactive ion beam

A study of ${}^{26}$Si states by neutron removal from a fast radioactive beam of ${}^{27}$Si has been performed. A beam of ${}^{27}$Si of energy 84.3 MeV/nucleon impinged on a polypropylene foil (C${}_3$H${}_6$) of 180 mg/cm${}^2$ thickness. Deexcitation $\gamma$ rays were detected with a highly segmented germanium detector array, in coincidence with the ${}^{26}$Si recoils, and the corresponding ${}^{26}$Si level energies were determined. In comparing our results to two previous $\gamma$-ray spectroscopic studies of ${}^{26}$Si level structures, we find good agreement with a recent measurement of the ${}^{12}$C(${}^{16}$O,$2n\gamma$)${}^{26}$Si reaction. Our results support the use of excitation energies from that study in helping determine the important resonance energies for the thermonuclear ${}^{25}$Al($p,\gamma$)${}^{26}$Si reaction rate. We do not observe a bound state at 4093 keV reported in an earlier study of the ${}^{24}$Mg(${}^3$He,$n\gamma$)${}^{26}$Si reaction.

Figure 1

Two-dimensional histogram of $\Delta E$ vs time of flight through the S800 for ions detected at the S800 focal plane, following interactions with the polypropelene target. The ${}^{26}$Si recoils of interest and other strong particle groups are indicated.

Figure 2

Doppler corrected $\gamma$-ray spectrum. The gamma transition energies are labeled with units of keV (see text for discussion).