The g-factors of the intra-band states 12, 13, 14, 15 in a magnetic-rotational band built on the 11 state in 82Rb are measured for the first time by using a transient magnetic field-ion implantation perturbed angular distribution (TMF-IMPAD) method. The magnetic-rotational band in 82Rb is populated by the 60Ni(27Al,4pn)82Rb reaction, and the time-integral Larmor precessions are measured after recoil implantation into a polarized Fe foil. The calculation of g-factors is also carried out in terms of a semi-classical model of independent particle angular momentum coupling on the basis of the four-quasiparticle configuration π(g9/2)2 ⊗ π(p3/2, f5/2) ⊗ ν (g9/2). The measured and calculated g-factors are in good agreement with each other. The g-factors and deduced shear angles decrease with the increase of spin along the band. This clearly illustrates the shear effect of a step-by-step alignment of the valence protons and neutrons in magnetic rotation. The semi-classical calculation also shows that the alignment of the valence neutron angular momentum is faster than that of the valence protons, which results in a decrease of g-factors with increasing spin. The present results provide solid evidence of the shear mechanism of magnetic rotation.
The lifetimes of excited states in the yrast band of 176Os have been measured up to I = 20ħ level using the Doppler shift attenuation method. The high-spin states of 176Os were populated via fusion evaporation reaction 152Sm(28Si,4n)176Os at a beam energy of 140 MeV. The results support an X(5) structure for 176Os at low spin. This structure disappears at high spin and shows a symmetry rotor character. The shape change of 176Os is similar to that of 178Os.
Temperature dependence of nuclear decays in metallic environments is a controversial issue. We measured the temperature dependence of the β+-decay half-life of22Na implanted into the metal host of palladium. It is found that the β+ -decay half-life of22Na in the metal Pd cooled to T = 15 K is shorter by 0.46(14)% than that at room temperature. The result is consistent in sign with, but clearly smaller than, the estimated one by the Debye model.
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