Examination of nuclear chirality with a magnetic moment measurement of the I = 9 isomeric state in $^{128}$Cs

International audienceThe g factor of the isomeric I=9+ bandhead of the yrast states in 128Cs is obtained from the time differential perturbed angular distribution measurement performed with the electromagnet at IPN Orsay. An external magnetic field of 2.146 T at the target position was attained with GAMIPE reaction chamber surrounded by four high-purity germanium detectors, of which two were low-energy photon spectrometer type. The results are in accordance with πh11/2⊗νh−111/2I=9+ bandhead assignment and are discussed in the context of chiral interpretation of the 128Cs nucleus as a composition of the odd proton, odd neutron, and even-even core with their angular momentum vectors. The obtained g-factor value was compared with predictions of the particle-rotor model. The experimental g factor corresponds to the nonchiral geometry of the isomeric bandhead. This observation indicates the existence of the chiral critical frequency in 128Cs and may explain the absence of the chiral doublet members for I