First Measurement of the g Factor in the Chiral Band: The Case of the Cs128 Isomeric State

Abstract

The g factor of the 56 ns half-life isomeric state in ^{128}Cs has been measured using the time-differential perturbed angular distribution method. This state is the bandhead of the positive-parity chiral rotational band, which emerges when an unpaired proton, an unpaired neutron hole, and an even-even core are coupled such that their angular momentum vectors are aplanar (chiral configuration). g-factor measurements can give important information on the relative orientation of the three angular momentum vectors. The measured g factor g=+0.59(1) shows that there is an important contribution of the core rotation in the total angular momentum of the isomeric state. Moreover, a quantitative theoretical analysis supports the conclusion that the three angular momentum vectors lie almost in one plane, which suggests that the chiral configuration in ^{128}Cs demonstrated in previous works by characteristic patterns of electromagnetic transitions appears only above some value of the total nuclear spin.

Reexamining nuclear chiral geometry from the orientation of the angular momentum

“…[2][3][4][5][6][7][8]. With the prediction [9] and confirmation [10] of multiple chiral doublets (Mχ D) in a single nucleus, the investigation of chirality continues to be one of the hottest topics in nuclear physics [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29].…”

“…[41][42][43]); (4) the orientation parameter of the system (e.g., in Refs. [23,41,42]); and (5) the distributions of the tilted angles of the angular momentum in the intrinsic frame (azimuthal plot) (e.g., in Refs. [39,40]).…”

“…It is known now that chiral rotation (or static chirality) can exist only above a certain critical frequency [23,31,32,44]. Namely, at low spin the chiral vibrations, understood as the oscillation of the total angular momentum between the left-and the right-handed configurations in the body-fixed frame, exists.…”

“…A dashed-dotted line is plotted to label this position. Note that the spin region (8 I < 13h) from the bandhead to the kink are usually called the chiral vibration region, which in fact is a planar rotation [1,23,31,32].…”

Multiple chiral doublet bands with octupole correlations in reflection-asymmetric triaxial particle rotor model

“…For the yrast band with negative parity, the configuration is found to be πg 9/2 ⊗ νf 5/2 . Further support for this subtle change in configuration for the negative-parity doublet bands may be obtained from future microscopic calculations and experimental results, for example, the three-dimensional TAC-CDFT [24] including the octupole deformation or the measurement of the g factor in the chiral bands [58].…”