D.M. Headly

A smoothly terminating rotational band in 64Zn

A rotational band has been discovered in the nucleus 64Zn; it extends from spin (12ℏ) to spin (24ℏ), and exhibits strong dipole transitions between its signature partners. In our interpretation, 64Zn takes on triaxial deformation (e∼0.3γ∼30°) at intermediate spin when an f7/2 proton is promoted across the spherical shell-gap at Z=28 to the g9/2 orbital. The situation is parallel to that occurring in the smooth terminating bands in the Sn and Sb isotopes at the Z=50 shell-gap. The band in 64Zn is the first example of a collective band approaching termination in the mass A∼60 region.

Core polarization by an intruder orbital in81Sr

Abstract A strongly deformed rotational band in 81 Sr has been studied up to a spin of312ℏ using the reaction 55 Mn( 29 Si, p2p) 81 Sr at95.2MeV. Lifetime measurements using the Doppler shift attenuation method imply an average quadruple moment of±3.5 (6) eb, corresponding to an axial deformation ofs 2 ≅0.4. These results have been interpreted as core polarization by the[431]12 + Nilsson orbital.

High-spin states and rotational coexistence in 25Mg

New high spin states in 25Mg have been located above the neutron threshold using the 12C(14N, pγ)25Mg reaction at E=23.5 MeV. The members of the ground state rotational band (Kπ=52+ have been tentatively identified up to 152+. The yrast 152+ (not a member of the ground state band) and 172+ states have also been tentatively assigned. These results support the interpretation of the new 172+ state and the previously known yrast 132+ state as fully aligned prolate configurations, i.e., prolate particle-hole states with K=I and γ=-120°.