Different mechanism of two-proton emission from proton-rich nuclei $^{23}$Al and $^{22}$Mg

TL;DR

This study investigates the decay mechanisms of two proton-rich nuclei, $^{23}$Al and $^{22}$Mg, revealing distinct two-proton emission processes through momentum and angular distribution measurements.

Contribution

It provides experimental evidence of different two-proton emission mechanisms in $^{23}$Al and $^{22}$Mg, highlighting the presence of diproton emission in $^{22}$Mg and sequential decay in $^{23}$Al.

Findings

Peak in $q_{pp}$ and $ heta_{pp}$ for $^{22}$Mg indicating diproton emission

Absence of such peaks in $^{23}$Al suggesting sequential decay

Different emission mechanisms identified for the two nuclei

Abstract

Two-proton relative momentum ($q_{pp}$) and opening angle ($\theta_{pp}$) distributions from the three-body decay of two excited proton-rich nuclei, namely $^{23}$Al $\rightarrow$ p + p + $^{21}$Na and $^{22}$Mg $\rightarrow$ p + p + $^{20}$Ne, have been measured with the projectile fragment separator (RIPS) at the RIKEN RI Beam Factory. An evident peak at $q_{pp}\sim20$ MeV/c as well as a peak in $\theta_{pp}$ around 30$^\circ$ are seen in the two-proton break-up channel from a highly-excited $^{22}$Mg. In contrast, such peaks are absent for the $^{23}$Al case. It is concluded that the two-proton emission mechanism of excited $^{22}$Mg is quite different from the $^{23}$Al case, with the former having a favorable diproton emission component at a highly excited state and the latter dominated by the sequential decay process.