Diabatic crossing of chiral “twins” in the odd-oddAg106nucleus: A theoretical perspective

Abstract

A systematic study of both the observed positive-parity magnetic rotation band and the negative-parity $\mathrm{\ensuremath{\Delta}}I=1$ doublet bands in an odd-odd $^{106}\mathrm{Ag}$ nucleus is carried out. The negative-parity doublet bands depict some unusual features that have not been observed in any isotope in the mass $A=100$ region. For instance, (i) the moment of inertia of the partner band is quite different from that of the yrast band, and (ii) these bands cross each other at an angular momentum of $I=14\ensuremath{\hbar}$. Also, the observed significantly large but constant $B(M1)$ transitions confirm that the strong $M1$ transitions are being reinforced by the contributions from collective rotation. To explain these features, a collective model has been developed whose kinetic and potential energies are extracted from the tilted-axis cranking model. Instead of the triaxial parameter $\ensuremath{\gamma}$, a second-order phase transition is found to be responsible for the spontaneous breakdown of chiral symmetry. Analytical solution of the Schr\odinger equation has generated a doublet nondegenerate eigenvalue spectrum. The ensuing model results based on the two-quasiparticle configuration $\ensuremath{\pi}{g}_{\frac{9}{2}}\ensuremath{\bigotimes}\ensuremath{\nu}{h}_{\frac{11}{2}}$ exhibit similarities with many observed features of the negative-parity doublet bands and hence confirm their chiral character. The cranking mass parameter in kinetic energy plays an important role in diabatic crossing between these emerged chiral twin bands.