Evidence of chiral bands in even-even nuclei

Abstract

Evidence for chiral doublet bands has been observed for the first time in the even-even nucleus 136 Nd. One chiral band was firmly established. Four other candidates for chiral bands were also identified, which can contribute to the realization of the multiple pairs of chiral doublet bands (Mχ D) phenomenon. The observed bands are investigated by the constrained and tilted axis cranking covariant density functional theory (TAC-CDFT). Possible configurations have been explored. The experimental energy spectra, angular momenta, and B(M1)/B(E2) values for the assigned configurations are globally reproduced by TAC-CDFT. Calculated results support the chiral interpretation of the observed bands, which correspond to shapes with maximum triaxiality induced by different multiquasiparticle configurations in 136 Nd.

Evolution from γ -soft to stable triaxiality in Nd136 as a prerequisite of chirality

“…Comparing with neighboring oddodd and odd-A nuclei, higher excitation energies are therefore needed to populate chiral bands in even-even nuclei, and high efficiency arrays are needed, since much lower intensities are expected due to the competition from various configurations comprising at least four unpaired nucleons. The first observation of chiral bands in even-even nuclei was reported very recently in 136 Nd [9] and discussed using the multi-j shell particle-rotor model in Ref. [10].…”

“…Partial results of this work on the newly observed chiral bands were reported in Ref. [9]. Sections II and III contain the description of the experiment and the data analysis.…”

Chirality of Nd135 reexamined: Evidence for multiple chiral doublet bands

“…Three-quasiparticle chiral bands have been observed at medium spins in nuclei of the A ≈ 130 mass region ( 133 La [8], 133 Ce [9], 135 Nd [10], 137 Nd [11]) and in nuclei of the A ≈ 100 mass region ( 103 Rh [12], 105 Rh [13,14], 111,113 Rh [15], 105 Ag [16], 107 Ag [17]). Very recently, four-and six-quasiparticle chiral bands have also been observed in even-even nuclei of the A ≈ 130 mass region ( 136 Nd [18] and 138 Nd [19]). In most nuclei only one chiral doublet was observed, but in a limited subset of chiral nuclei two or more chiral doublets were observed ( 78 Br [20], 103 Rh [12], 105 Rh [13], 133 Ce [9], 136 Nd [18], 195 Tl [21], and possibly 107 Ag [22]), exhibiting the exotic phenomenon of multiple chiral doublet bands (MχD) [23][24][25][26][27][28][29][30][31].…”

“…In most nuclei only one chiral doublet was observed, but in a limited subset of chiral nuclei two or more chiral doublets were observed ( 78 Br [20], 103 Rh [12], 105 Rh [13], 133 Ce [9], 136 Nd [18], 195 Tl [21], and possibly 107 Ag [22]), exhibiting the exotic phenomenon of multiple chiral doublet bands (MχD) [23][24][25][26][27][28][29][30][31]. In the even-even nucleus 136 Nd, the record of five nearly degenerate band pairs were identified, with properties in agreement with chiral interpretation within the tilted axis cranking constrained density functional theory (TAC-CDFT) framework [18], which were also successfully described in detail as chiral doublets in the framework of the multi-j shell particle rotor model (PRM) [31]. An alternative formalism predicting a new type of chiralitiy, different from that existing in odd-odd and odd-even nuclei, based on the generalized coherent state model, was also proposed and applied to the even-even nucleus 138 Nd [32,33].…”

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].…”