Alpha-Particle Bombardment of Magnesium Isotopes

Energy levels in three aluminum isotopes have been observed with alpha-particle bombardment of magnesium isotope targets. Protons from the reaction were observed with a proportional counter. By using an aluminum foil changer before the counter and recording only those protons near the end of their range, an energy resolution from 4 to 8% was obtained in the various runs. The ground-state $Q$ values were calculated by comparison to the ${\mathrm{Mg}}^{24}(\alpha , p){\mathrm{Al}}^{27}$ ground-state group using the known $Q$ value for the inverse reaction. The ground-state $Q$ values were found to be -1.29±0.04 Mev for ${\mathrm{Mg}}^{25}(\alpha , p){\mathrm{Al}}^{28}$, and -2.90±0.04 Mev for ${\mathrm{Mg}}^{26}(\alpha , p){\mathrm{Al}}^{29}$. Proton groups were found corresponding to excited states in ${\mathrm{Al}}^{27}$ at 0.85, 1.06, 2.17, and 2.64 Mev; in ${\mathrm{Al}}^{28}$ at 1.00, 1.57, 2.18, 2.54, and 2.96 Mev; in ${\mathrm{Al}}^{29}$ at 1.69 Mev. The mass value of ${\mathrm{Al}}^{29}$ was calculated to be 28.98972±0.00006 amu.