Evidence against the wobbling nature of low-spin bands in $^{135}$Pr

TL;DR

This study challenges the wobbling interpretation of low-spin bands in $^{135}$Pr by showing their electromagnetic transitions are predominantly magnetic, aligning instead with a quasiparticle-plus-triaxial-rotor model.

Contribution

The paper provides experimental evidence against the wobbling nature of certain nuclear bands in $^{135}$Pr, supporting a re-alignment model instead.

Findings

Transition mixing ratios indicate dominant M1 character.

Experimental data contradict wobbling band predictions.

Results align with quasiparticle-plus-triaxial-rotor model.

Abstract

The electromagnetic character of the $\Delta I=1$ transitions connecting the one- to zero-phonon and the two- to one-phonon wobbling bands should be dominated by an $E2$ component, due to the collective motion of the entire nuclear charge. In the present work it is shown, based on combined angular correlation and linear polarization measurements, that the mixing ratios of all analyzed connecting transitions between low-lying bands in $^{135}$Pr interpreted as zero-, one-, and two-phonon wobbling bands, have absolute values smaller than one. This indicates predominant $M1$ magnetic character, which is incompatible with the proposed wobbling nature. All experimental observables are instead in good agreement with quasiparticle-plus-triaxial-rotor model calculations, which describe the bands as resulting from a rapid re-alignment of the total angular momentum from the short to the intermediate nuclear axis.