Unveiling the intruder deformed 0$^+_2$ state in $^{34}$Si

TL;DR

This paper investigates the properties of the 0$^+_2$ state in $^{34}$Si, revealing its energy, half-life, deformation, and mixing characteristics through experimental detection and shell model calculations.

Contribution

The study provides the first detailed characterization of the intruder 0$^+_2$ state in $^{34}$Si, including its energy, decay modes, and deformation, supported by new shell model insights.

Findings

Excitation energy of 2719 keV for 0$^+_2$ state.

Half-life measured as 19.4 ns.

Large deformation parameter of 0.29.

Abstract

The 0$^+_2$ state in $^{34}$Si has been populated at the {\sc Ganil/Lise3} facility through the $\beta$-decay of a newly discovered 1$^+$ isomer in $^{34}$Al of 26(1) ms half-life. The simultaneous detection of $e^+e^-$ pairs allowed the determination of the excitation energy E(0$^+_2$)=2719(3) keV and the half-life T$_{1/2}$=19.4(7) ns, from which an electric monopole strength of $\rho^2$(E0)=13.0(0.9)$\times10^{-3}$ was deduced. The 2$^+_1$ state is observed to decay both to the 0$^+_1$ ground state and to the newly observed 0$^+_2$ state (via a 607(2) keV transition) with a ratio R(2$^+_1$$\rightarrow0^+_1/2^+_1$$\rightarrow0^+_2$)=1380(717). Gathering all information, a weak mixing with the 0$^+_1$ and a large deformation parameter of $\beta$=0.29(4) are found for the 0$^+_2$ state, in good agreement with shell model calculations using a new {\sc sdpf-u-mix} interaction allowing \textit{np-nh} excitations across the N=20 shell gap.