Mechanism Of Antimagnetic Rotation In Odd-A¹⁰⁹Cd

The rotational band has become one of the most important phenomena in atomic nuclei over the past decades. In general, rotational bands are built on intrinsic states violating rotational symmetry and exist in nuclei with substantial quadrupole deformation. However, over the past several years, people have discovered a new kind of rotation bands with strong magnetic dipole (Ml) and very weak E2transitions in nearly spherical nuclei. Frauendorf et al. suggested calling this new rotational mode "magnetic rotation". In analogy with ferromagnet and antiferromagnet, Frauendorf predicted another kind of rotational mode in nuclei as "antimagnetic rotation":in specific nearly spherical nuclei, the protons (neutrons) angular momentum vectors are aligned back to back in opposite directions and are nearly perpendicular to the total angular momentum vectors of neutrons (protons) at the beginning frequency. As the rotational frequency increases, the vectors of the proton (neutron) holes align toward the vector of neutrons (protons), and the direction of the total angular momentum is almost unchanged. Since the prediction of antimagnetic rotation in nuclei, this interesting phenomenon has attracted lots of attention.In this work, we used the tilted axis cranking model based on covariant density functional theory to investigate the negative-parity yrast sequence in109Cd. The energy spectra, the relation between spin and rotational frequency, deformation parameters and reduced E2transition probabilities are calculated, which are in good agreement with available data. The orientation of angular momentum is also extracted and discussed in detail. By investigating microscopically the orientation of angular momentum and the contributions of AMR and core to the total angular momentum, we find that109Cd should be a critical transitional nucleus between the antimagnetic and core rotation.