$\beta$-decay spectroscopy of the proton drip-line nucleus ${}^{22}\mathrm{Al}$

A detailed $\beta$-decay spectroscopic study of ${}^{22}\mathrm{Al}$ was performed at the Radioactive Ion Beam Line in Lanzhou. With the $\beta \text{−}\gamma$-particle coincidence measurement by a high-resolution DSSD particle detection array and a high efficiency $\gamma$-ray detection array, total eight excited states in ${}^{22}\mathrm{Mg}$ fed by Gamow-Teller transitions was newly identified. The one-proton, two-proton, and $\alpha$ decays of the IAS at 14046(5) keV in ${}^{22}\mathrm{Mg}$, which were partly observed in different experiments before, were identified simultaneously in the present work, providing accurate spectroscopic information about its decay. A more complete $\beta$-decay scheme of ${}^{22}\mathrm{Al}$ was constructed and compared to the shell-model calculations with the USD-type Hamiltonians, USDC and USDB.

Figure 1

Particle identification plot for incoming radioactive ions at RIBLL.

Figure 2

Decay-time spectrum in coincidence with (a) all the subsequent decay products, (b) 1633-keV $\gamma$ ray, and (c) 1887-keV $\gamma$ ray.

Figure 3

The energy spectrum of emitted charged-particle in the $\beta$ decay of ${}^{22}\mathrm{Al}$ measured by DSSD3. Each particle peak from the $\beta$-delayed particle decay of ${}^{22}\mathrm{Al}$ is labeled with a letter p followed by a number. The proton peak at 5808 keV reported in Ref. [11] (labeled with * at corresponding position) was not observed in present work.

Figure 4

Energy spectrum of $\gamma$ rays measured by the $\gamma$-ray detection array in coincidence with ${}^{22}\mathrm{Al}\beta$-decay signals in the DSSD particle detection array.

Figure 5

Coincident $\gamma$-ray spectra gated on the (a) 332-keV $\gamma$ ray and (b) 2062-keV $\gamma$ ray.

Figure 6

The energy spectra of emitted charged-particle in coincidence with the (a) 332-keV $\gamma$ ray, (b) 1384-keV $\gamma$ ray, (c) 1113-keV $\gamma$ ray, (d) 1633-keV $\gamma$ ray, and (e) 1887-keV $\gamma$ ray. For the convenience of comparison, the raw charged-particle spectrum was scaled to match the amplitude of the strongest peak ${\mathrm{p}}_6$ and plotted in Fig. 6 with red line.

Figure 7

Decay scheme for ${}^{22}\mathrm{Al}$. All the energies and intensities labeled in the scheme are deduced from the present work. The energies of the ground states of ${}^{18}\mathrm{Na}, {}^{20}\mathrm{Ne}$, and ${}^{21}\mathrm{Na}$ are labeled by the separation energies of $\alpha$, two-proton, and one-proton, respectively [3]. The peak labels represent that the peaks in Fig. 3 are emitted from corresponding energy levels.

Figure 8

Comparison of the calculated levels with branching ratios with the experimental results of ${}^{22}\mathrm{Al}\beta$ decay measured in the present work. The theoretical and experimental branching ratios are labeled with red color.