Triaxiality in Er isotopes in the framework of IBM-1

Abstract The nuclear structure in the even–even 160-180 Er chain of isotopes is investigated by means of a mean-field-derived IBM-1 Hamiltonian with an intrinsic triaxial deformation derived from fermionic proxy-SU(3) irreducible representations (irreps). Energy levels and B ( E 2) transition strengths are calculated and compared to experimental data, where available. It is shown that the inclusion of an intrinsic triaxial deformation, stemming from the proxy-SU(3) irreps, leads to a significantly improved agreement between theoretical predictions and experimental data, compared to the axially symmetric case. The results are also compared to recent triaxial projected shell model (TPSM) and Monte Carlo Shell Model (MCSM) predictions, showing an overall good agreement, further pointing toward the preponderance of triaxiality throughout the nuclear chart.