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

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 $B(M1;2_2^{+}\to 2_1^{+}$)=0.18(2) $\hat{I}{¼}_{\mathrm{N}}^2$ 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 $B(M1;2_{\mathrm{ms}}^{+}\to 2_1^{+})$ 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.