A new differentially pumped plunger device to measure excited-state lifetimes in proton emitting nuclei

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Lifetime measurements of excited states in 178 Hg have been performed using the 103 Rh(78 Kr, p2n) reaction at a beam energy of 354 MeV. The recoil-decay tagging (RDT) technique was applied to select the 178 Hg nuclei and associate the prompt γ rays with the correlated characteristic ground-state α decay. Lifetimes of the four lowest yrast states of 178 Hg have been determined using the recoil distance Doppler-shift (RDDS) method. The experimental data are compared to theoretical predictions with focus on shape coexistence. The results confirm the shift of the deformed prolate structures to higher lying states but also indicate their increasing deformation with decreasing neutron number.

Section: Methodsmentioning

confidence: 99%

Shape coexistence in Hg178

Müller-Gatermann¹,

Dewald²,

Fransen³

et al. 2019

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“…By using Eq. (1), a lifetime value can be obtained for each target-to-degrader distance, while the final lifetime value is obtained from the weighted average within the sensitive region [13].…”

Section: Excitedmentioning

confidence: 99%

“…The experimentally deduced electromagnetic transition strengths for the low-lying states in the yrast rotational band structure are compared with results from total Routhian surface, semiclassical model, and tilted axis cranking model calculations based on a relativistic mean-field approach. 92 Mo target mounted inside the differential plunger for unbound nuclear states (DPUNS) device [13]. The velocity of the recoiling fusion-evaporation residues, v/c, was 4.4% and 3.4% before and after a 1-mg/cm 2 -thick Mg degrader foil, respectively.…”

Section: Introductionmentioning

confidence: 99%

Lifetime measurements inRe166: Collective versus magnetic rotation

Li¹,

Cederwall²,

Doncel³

et al. 2016

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Lifetimes of excited states in the neutron-deficient odd-odd nucleus 166 Re have been measured for the first time using the recoil distance Doppler-shift method. The measured lifetime for the (8 − ) state; τ = 480 (80) ps, enabled an assessment of the multipolarities of the γ rays depopulating this state. Information on electromagnetic transition strengths were deduced for the γ -ray transitions from the (9 − ), (10 − ), and (11 − ) states, and in the case of the (10 − ) and (11 − ) states limits on the B(M1) and B(E2) strengths were estimated. The results are compared with total Routhian surface predictions and semiclassical calculations. Tilted-axis cranking calculations based on a relativistic mean-field approach (TAC-RMF) have also been performed in order to test the possibility of magnetic rotation in the 166 Re nucleus. While the TAC-RMF calculations predict a quadrupole-deformed nuclear shape with similar β 2 deformation as obtained by using the TRS model, it was found that the experimental electromagnetic transition rates are in better agreement with a collective-rotational description.

“…Proton emission can provide valuable nuclear-structure information and allow sensitive tests of theoretical nuclear models for proton-rich nuclei in the region beyond the drip line [1,2]. Advances in experimental techniques [3,4] and the associated new experimental data can allow extensions to these models to be made [5,6], especially those models which explore the coupling of weakly bound and unbound states to the continuum. Proton emission from 113 Cs was first discovered in 1984 by Faestermann et al [7].…”

Section: Introductionmentioning

confidence: 99%

Deformation of the proton emitterCs113from electromagnetic transition and proton-emission rates

Hodge¹,

Cullen²,

Taylor³

et al. 2016

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The lifetime of the (11/2 +) state in the band above the proton-emitting (3/2 +) state in 113 Cs has been measured to be τ = 24(6) ps from a recoil-decay-tagged differential-plunger experiment. The measured lifetime was used to deduce the deformation of the states using wave functions from a nonadiabatic quasiparticle model to independently calculate both proton-emission and electromagnetic γ-ray transition rates as a function of deformation. The only quadrupole deformation, which was able to reproduce the experimental excitation energies of the states, the electromagnetic decay rate of the (11/2 +) state and the proton-emission rate of the (3/2 +) state, was found to be β 2 = 0.22(6). This deformation is in agreement with the earlier proton emission studies which concluded that 113 Cs was best described as a deformed proton emitter, however, it is now more firmly supported by the present measurement of the electromagnetic transition rate.