Excited-state magnetic moments of the magnesium isotopes

Transient field(TF) is an effective magnetic field acting on ions passing through ferromagneticfoils. Because of large TF strengthsa large number of nuclear magnetic moments have been measured for short-lifetime excited states onstable nuclei. Such measurements have been carried out using stable-ion beams at velocities vvo，因为the velocity dependence of the TF strength b_ <TF> is well known in this region，where Z and vo denote the atomic number and the Bohr velocity. Taking into account the fact thatradioactive-isotope beams produced in the projective -fragmentation reaction have high velocities v【greater than or equal】Z^ vo，it is important to determine the velocity dependence of b_ <TF> at a velocity of approximately Z^ . voor higher. From measurements using E=135 MeV ^<22>Ne and ^<24>Mg beams obtained From the K=70 RIKENAVF cyclotron and the targets consisting of two layers, Au and Gd，we have determined preliminary values of b_ <TF> strengths. Their values were smaller than theexpected strengths from those determined in the lower velocity区域. Theoretically，a sharp decrease in TF strength was predicted at velocities v【greater than or equal】Z^ vo. Theobtained strengths, however，are much larger than this prediction. It rather supports a recent model，with which a rather constant or even increasing trend of b_ <TF> strength is predicted at velocitiesv【greater than or equal】Z^ vo. Moreover，this observation is in agreement with other measurements obtained at similar velocities. thisfinding allows us to measure the excited-state magnetic moments of unstable nuclei produced in theprojectile-fragmentation reactions。

Transient field(TF) is an effective magnetic field acting on ions passing through ferromagnetic foils. Because of large TF strengths, a large number of nuclear magnetic moments have been measured for short-lifetime excited states on stable nuclei. Such measurements have been carried out using stable-ion beams at velocities v << Z^・ vo, since the velocity dependence of the TF strength B_<TF> is well known in this region, where Z and vo denote the atomic number and the Bohr velocity. Taking into account the fact that radioactive-isotope beams produced in the projectile-fragmentation reaction have high velocities v 【greater than or equal】 Z^・ vo, it is important to determine the velocity dependence of B_<TF> at a velocity of approximately Z^・ vo or higher. From measurements using E=135 MeV ^<22>Ne and ^<24>Mg beams obtained from the K=70 RIKEN AVF cyclotron and the targets consisting of two layers, Au and Gd, we have determined preliminary values of B_<TF> strengths. Their values were smaller than the expected strengths from those determined in the lower velocity region. Theoretically, a sharp decrease in TF strength was predicted at velocities v【greater than or equal】Z^・ vo. The obtained strengths, however, are much larger than this prediction. It rather supports a recent model, with which a rather constant or even increasing trend of B_<TF> strength is predicted at velocities v【greater than or equal】Z^・ vo. Moreover, this observation is in agreement with other measurements obtained at similar velocities. This finding allows us to measure the excited-state magnetic moments of unstable nuclei produced in the projectile-fragmentation reactions.