The Triaxially Deformed Critical Point Symmetry For The Odd-odd Nuclear Systems

Shape phase transitions in nuclei have attracted a lot of attention in the past two decades.In particular,critical point symmetries proposed by Iachello provide new ways to analytically or semi-analytically describe nuclear shape phase transitions based on collective models.The critical point symmetries have been further extended to the odd-mass nuclei with triaxial deformations.In this work,a critical point symmetry for odd-odd nuclei called CT(4)is proposed through coupling a single neutron and proton to the triaxial critical point symmetry T(4)used to describe even-even nuclei with rigidly triaxial deformations.The new model has been solved in a numerical way under the strong-coupling basis.By comparing to the original T(4)model as well as the particle-rotor model,it is shown that the CT(4)critical point symmetry can offer a reasonable description of the collective rotational structures in the transitional oddodd nuclei with triaxial deformations.In addition,the model validity of CT(4)in describing the data for odd-odd nuclei has been further examined through applying the model to analyze the chiral bands in the typical odd-odd nucleus with triaxial deformation,and some schemes are also suggested to improve the present model.