A re-examination of the band structure of²²³Ra and reflection asymmetry in this nucleus

Abstract

A thorough examination of the level structure of 223Ra provides evidence that leads to an extensive re-evaluation of spin assignments and hence band structure. Altogether six bands corresponding to three parity-coupled pairs are identified and the interpretation of the data suggests that this N = 135 nucleus may possess an octupole deformation.Results from a-y and y-y directional correlations and y-ray directional distribution measurements were combined and, together with internal conversion coefficient (ICC) data, give unique spin-parity assignments to most levels. A continuously purified source was used to make unambiguous y-ray assignments. Level half-lives were obtained from recoil distance and Doppler methods.The results show that the ground state is 3/2+. Parity doublets were identified as {3/2+(0 keV), 3/2-(50.1 keV)}, {1/2+(286.1 keV), 1/2-(350.5 keV)} and {5/2+(324.8 keV), 5/2-(369.3 keV)}. The multipole mixing ratios of many of the stronger y-ray transitions were determined and also the amplitudes and relative phases of the angular momentum components carried by the a decays.The band structure is interpreted within the framework of calculations using the Strutinski shell-correction method with a single-particle level scheme obtained with a Woods-Saxon mean field. The minimisation procedure for the total energy is achieved in a multideformation space including higher-order multipolarity deformations up to I. = 7. The importance of higher-order multipolarity deformation parameters is underlined.

Ra223levels fed in theFrAbdul-Hadi1, Barci2, Weiss3 et al. 1993Phys. Rev. C15050View full textAdd to dashboardCite

“…18, and 236.05 keV with a branching ratio I286/I256 good agreement with that obtained in the Th o. '-decay study [15]. The 334.27+0.06 keV (I"=-', +) level was RaLEVELSFEDINTHE FrPDECAY 107 previously known from the Fr decay study [4].…”

“…The bandhead of the K =-', band at 50.09+0.02 keV depopulates by two y transitions of 50.10 and 20.27 keV, also observed in the Th a-decay study [15]. The re- constancy correlates well with a Ra static octupole deformation, since the logft values are expected to have rather close values for transition to different members of a spin-parity doublet (PD).…”

“…(2) 876.5 (10) 892 (3) 897.5(20) 908 (2) 0.70 (15) 749.2(1) 754. 1(2) 0.40 (8) 757.7(1) 763.1(2) 0.80 (16) 773.5 (4) 12.3(12) 776.3(1) 781.5(2) 0.70 (15) 787.7 (5) 0.40 (6) Only seen in coincidence experiments.…”

“…The lower state is the I = -, ' level at 329.80+0.05 keV; the I = -, ' bandhead state, identified at 350.48 keV, in Th a decay [3,15], is tentatively suggested to be fed by Fr p decay to account for the 350.50 keV y line seen in single y-ray spectra, for which a careful analysis allowed its differentiation from the ' Pb background line; the 299.95 keV y transition, supposed to depopulate it to the 50.1 keV level, was mainly placed between the 329~8 and 29.78 keV states. The 376.…”

“…II A), was fixed in front of the 40% HPGe detector and counted for 60 s at fixed intervals of 120 s. The counting rate was followed for ten half-lives, and the analysis was performed either on the total y spectra or on the 236. [15] were used; for other cases, ICC values were deduced by interpolation from the theoretical values of Rosel et al [16]. In the absence of experimental data concerning the p feeding of Ra (g.s.…”