Nuclear Gamma-Rays from Low Energy Proton Bombardment of Sodium, Magnesium, and Aluminum

Gamma-rays produced by the resonance capture of 200-415-kev protons in sodium, magnesium, and aluminum have been investigated with a single crystal NaI(Tl) scintillation spectrometer. Excited states in ${\mathrm{Mg}}^{24}$, ${\mathrm{Al}}^{25}$, ${\mathrm{Al}}^{27}$, and ${\mathrm{Si}}^{28}$ with energies above the ground state of 12 Mev, 2.5 Mev, 8.6 Mev, and 12 Mev, respectively, were found to decay by cascade gamma-emission. Direct transitions to the ground state of ${\mathrm{Mg}}^{24}$, ${\mathrm{Al}}^{27}$, and ${\mathrm{Si}}^{28}$ were not observed. Observed pulse-height distributions, location of observed peaks, identifiable gamma-rays and their relative intensities are given. Decay schemes are proposed to account for the observed gamma-rays of ${\mathrm{Al}}^{27}$, ${\mathrm{Si}}^{28}$, and ${\mathrm{Al}}^{25}$. They are found to involve energy levels which are in general agreement with levels found in ($d, n$) and ($p, p$) scattering experiments; in the case of ${\mathrm{Al}}^{25}$, with levels found in the mirror nucleus ${\mathrm{Mg}}^{25}$. An estimate is made of the absolute proton capture probability in the targets used.