Shape coexistence and mixing of low-lying 0+ states in 96Sr

Abstract

The low energy excited 0 + 2,3 states in 96 Sr are amongst the most prominent examples of shape coexistence across the nuclear landscape. In this work, the neutron [2s 1/2 ] 2 content of the 0 + 1,2,3 states in 96 Sr was determined by means of the d( 95 Sr,p) transfer reaction at the TRIUMF-ISAC2 facility using the SHARC and TIGRESS arrays. Spectroscopic factors of 0.19(3) and 0.22 (3) were extracted for the 96 Sr ground and 1229 keV 0 + states, respectively, by fitting the experimental angular distributions to DWBA reaction model calculations. A detailed analysis of the γ-decay of the isomeric 0 + 3 state was used to determine a spectroscopic factor of 0.33(13). The experimental results are compared to shell model calculations, which predict negligible spectroscopic strength for the excited 0 + states in 96 Sr. The strengths of the excited 0 + 2,3 states were also analyzed within a two-level mixing model and are consistent with a mixing strength of a 2 =0.40(14) and a difference in intrinsic deformations of |∆β| = 0.31(3). These results suggest coexistence of three different configurations in 96 Sr and strong shape mixing of the two excited 0 + states.

Single-particle structure in neutron-rich Sr isotopes approaching the N=60 shape transition

“…The 213 keV state is almost exclusively populated directly, a small contribution of indirect feeding from above is observed in the γ -gated excitation energy spectrum. Note that this state is isomeric with a half-life of T 1/2 = 4.3(1) ns [16], therefore the efficiency for detecting this transition in the present experiment is much reduced, similar to the case of the decay of the 0 + 2 state in 96 Sr [7]. No evidence for the population of the 986 keV J π = (9/2 + ) state was found.…”

“…Details of the beam production can be found in Refs. [7,10]. The postaccelerated beams were impinging upon ≈0.5 mg/cm 2 , CD 2 deuterated polyethylene targets (>90% deuterium/hydrogen ratio) at the center of the SHARC/TIGRESS setup.…”

“…This corresponds to the removal of a 3s 1/2 neutron from the J π = 1/2 + ground state of 95 Sr. The spectroscopic factors amount to C 2 S = 0.336 (7) for the peak-fit method, and 0.314 (7) for the subtraction method. This value for the spectroscopic factor agrees very well with the one obtained for the 2 H( 94 Sr, p) 95 Sr reaction measured within the same campaign (C 2 S = 0.41(9) [10]).…”

“…In 96 Sr the excited 0 + states are connected by a very strong electromagnetic transition matrix element [6]. A measurement of the (d, p) transfer reaction cross section from the ground state of 95 Sr to the 0 + states of 96 Sr showed that the excited 0 + states can be understood resulting from the strong mixing of two configurations with very different deformation [7].…”

Single-particle and collective structures in neutron-rich Sr isotopes

“…[7] and apply it to study the Sr isotopes, both even and odd between the N = 50 and N = 58. Stimulated by the wealth of new data in this region [13][14][15][16][17][18], the calculations of low-energy spectra, transition rates and spectroscopic factors are performed and discussed. The approach from Ref.…”