Lifetime measurement of candidate chiral doublet bands in theRh103,104isotopes with the recoil-distance Doppler-shift method in inverse kinematics

Abstract

Lifetimes of chiral candidate structures in 103,104 Rh were measured using the recoil distance Doppler-shift method. The Gammasphere detector array was used in conjunction with the Cologne plunger device. Excited states of 103,104 Rh were populated by the 11 B( 96 Zr, 4n) 103 Rh and 11 B( 96 Zr, 3n) 104 Rh fusion-evaporation reactions in inverse kinematics. Three and five lifetimes of levels belonging to the proposed chiral doublet bands are measured in 103 Rh and 104 Rh, respectively. The previously observed even-odd spin dependence of the B(M1)/B(E2) values is caused by the variation in the B(E2) values, whereas the B(M1) values decrease as a function of spin.Nuclear chirality is the most recently recognized form of spontaneous symmetry breaking in nuclei [1]. Mutually orthogonal coupling of three angular momenta results in the formation of either left-or right-handed geometry in the bodyfixed frame and leads to a doubling of states in the laboratory frame. The two systems are related via time reversal rather than parity transformation, thereby making nuclear chirality unique among other chiralities observed in a wide scale range of nature from elementary particles to biological systems such as human hands. In nuclei, stable triaxial deformation is essential for the mutual perpendicular coupling of the angular momenta involved.Nearly degenerate pairs of I = 1 rotational bands, which are interpreted as a manifestation of chirality, are observed systematically in several odd-odd and in a few odd-A nuclei in the mass A ∼ 130 [2-9] and the A ∼ 100 [10-14] regions. In these odd-odd nuclei, three angular momenta are provided by the valence proton, valence neutron, and the core rotation that align along the respective three principal axes of the triaxially deformed core to minimize the energy of the nuclear system. In odd-A nuclei, chiral bands are built on the three quasiparticle configuration in which a broken pair of nucleons provides one of the three angular momenta.Observation of chiral doublet bands demands an experimental verification of identical properties between the doublet members. Therefore, two experimental criteria must * tomokazu@rcnp.osaka-u.ac.be fulfilled; (i) the observation of nearly degenerate I = 1 bands built on the same single-particle configuration and (ii) identical electromagnetic properties, namely similar B(E2) and B(M1) values of in-band and interband transitions. In addition, as a consistency check for the perpendicular coupling of single particle angular momenta and the core rotation, constancy of S(I ) = [E(I ) − E(I − 1)]/2I as a function of spin, is expected. Early studies have concentrated on the criterion (i) and identified the chiral doublet candidates. However, the more stringent test (ii) has been pursued with lifetime measurements of 134 pr [15], 132 La, 128 Cs [16], and 135 Nd [17] in the mass A ∼ 130 region. The results for 134 Pr, of which the doublet structures exhibit the best overall energy degeneracy, revealed similar B(M1) values, but 2-3 times larger B(E2) values for...

High-spin structure of104Pd

“…Recently, a study of the chiral doublet bands in 103 Rh has shown that the energy separation of these structures depends mainly on the core properties and, to a lesser extent, on the valence quasiparticle coupling [6]. However, the chiral interpretation in the A = 130 region has been questioned due to lifetime measurements [7,8], and it could not be confirmed by lifetime experiments in the nuclei 103 Rh and 104 Rh [9]. In this respect, it is important to understand the necessary conditions leading to the emergence of chiral geometry, one of which is the shape of the corresponding even-even core.…”

New candidate chiral nucleus in the A≈80 mass region: Br473582

“…Based on constrained triaxial covariant density functional theory (CDFT) calculations [2], it has been suggested that multiple chiral doublet (Mχ D) bands can exist in a single nucleus [3][4][5][6][7][8]. To date, the chiral doublet bands, including Mχ D bands, have been reported in more than 40 nuclei in the A ≈ 80 [9,10], 100 [11][12][13][14][15][16][17][18], 130 [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35], and 190 [36][37][38][39][40][41][42] mass regions. For details, see recent reviews [43][44][45][46][47][48][49] or data tables [50].…”

Recent progress in multiple chiral doublet bands *

“…To test the theoretical prediction of chirality in atomic nuclei, significant effort has been devoted to further exploring this interesting phenomenon. Thus far, such chiral doublet bands have been reported in the 80 [2][3][4], 100 [5][6][7][8][9][10][11][12], 130 [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29], and 190 [30][31][32][33][34][35][36] mass regions of the nuclear chart. For details, see recent reviews on nuclear chirality and related topics [37][38][39][40][41][42][43][44][45] or data tables [46].…”