Microscopic Investigation Of Magnetic Rotations In Mass Number A～190 Region

In the 1990s,a rotation mode,which is obviously different from the traditional electric multipole rotation,was proposed,called”magnetic rotation”.Clark and others experimentally measured the lifetime of¹⁹⁸Pb and¹⁹⁹Pb,and proved the existence of magnetic rotation bands for the first time.Experimentally,magnetic rotation bands have been observed in A～60,80,110,140 and 190 mass regions and over 200 candidate magnetic rotation bands have been identified in over 100 nuclides.The A～190 region has always been a hot region in the study of magnetic rotation.The number of protons in this nuclear region is around Z=82,and it is easy to form a nearly spherical shape.High-j h_9/2and i_13/2proton particles and i_13/2neutron holes play an important role in the magnetic rotation bands.A number of magnetic rotation bands were discovered in Pb（Z=83）isotopes where the coupling between theπ[h_9/2i_13/2]_K=11proton particles and theνi_13/2^-nneutron holes.A series of M1 bands have also been observed in the neighboring Bi（Z=83）isotopes,however,both experimental and theoretical discussions on magnetic rotation are scarce.In this paper,the characteristics of the magnetic rotation bands in^191-202Pb are studied firstly,and the experimental characteristics such as energy level structure,moment of inertia and electromagnetic transition properties are systematically studied.Then the possible mag-netic rotation bands in²⁰²Pb are described microscopically by using the tilted axis cranking covariant density functional theory（TAC-CDFT）based on point-coupling interaction,the ex-istence of the shears mechanism is supported.In addition,for the neighboring Bi isotopes,the two neutron-rich²⁰²Bi and²⁰³Bi,which are most likely to form magnetic rotation bands and have been discussed least,are selected for discussion.The configurations of the four magnetic dipole bands observed in^202,203Bi are suggested by the systematic comparison with Pb isotopes,including moment of inertia and energy level system,and the spin of band head is suggested.Four magnetic dipole bands in^202,203Bi have been studied microscopically and self-consistent by the tilted axis cranking covariant density functional theory.Physical quantities including energy spectrum,total angular momentum,deformation parameters and M1 and E2 transitions have been calculated,and the dependence of proton angular momenta and neutron angular mo-menta on rotational frequency is discussed.This work supports²⁰²Bi and²⁰³Bi as magnetic rotation candidates.