Isolated one-phonon mixed-symmetry 2+ state of the radioactive neutron-rich nuclide 132Te

TL;DR

This study identifies and characterizes the mixed-symmetry 2+ state in the radioactive isotope 132Te using lifetime measurements and shell-model calculations, revealing its properties and behavior near shell closures.

Contribution

First unambiguous identification of the mixed-symmetry 2+ state in 132Te through combined experimental and theoretical analysis.

Findings

Large B(M1) transition strength confirms the mixed-symmetry state.

Energy and B(M1) strength decrease near the Z=50 shell closure.

Results agree with shell-model predictions.

Abstract

The $M1$ transition strengths between excited $2^+$ states of the neutron-rich, radioactive nuclide $^{132}$Te have been studied through direct lifetime measurements using the Doppler-shift attenuation method in a two-neutron transfer reaction on a $^{130}$Te target. An unambiguous identification of the lowest-lying mixed-symmetry $2^+$ state has been achieved on the basis of the large $B(M1;2^+_2\rightarrow2^+_1$)=0.18(2) $\mu_\mathrm{N}^2$ transition strength, in agreement with shell-model calculations. Results are compared to the shell model, and the analysis of both, data and calculations, unambiguously identifies the second-excited $2^+$ state of $^{132}$Te as the one-quadrupole phonon mixed-symmetry state of this isotope. A lowering of the energy and $B(M1;2^+_\mathrm{ms}\rightarrow 2^+_1)$ strength within the $N$=80 isotones toward the $Z$=50 shell closure is observed, which goes alongside with the lowering of the $E2$ collectivity approaching the magic proton shell.