Level spin for superdeformed nuclei near<i>A</i>=194

Becker, J. A.; Henry, E. A.; Kuhnert, A.; Tf, Wang; Yates, S. W.; Diamond, R. M.; Stephens, F. S.; Draper, J. E.; Körten, W.; Deleplanque, M. A.; Macchiavelli, A. O.; Azaiez, F.; Kelly, W.H.; Cizewski, J. A.; Brinkman, M. J.

doi:10.1103/physrevc.46.889

Cited by 78 publications

(26 citation statements)

References 20 publications

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“…Pair correlations which are present in SD bands in the A 190 region [20] lead to K 0 for the ground band. The spins for band 1 are in agreement with those derived [24] from a fit of ᑣ ͑2͒ vshv and an extrapolation to zero frequency.…”

Section: (A)] the Highenergy Lines [Insupporting

confidence: 82%

Excitation Energies and Spins of a Superdeformed Band in194Hgfrom One-Step Discrete Decays to the Yrast Line

Khoo¹,

Carpenter²,

Lauritsen³

et al. 1996

Phys. Rev. Lett.

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151

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Discrete g rays directly connecting states of a superdeformed (SD) band in 194 Hg to the yrast states have been discovered. Thus, the excitation energies and spins of all members of the lowest SD band are established for the first time, together with their likely parity. The SD band decays from its 10 1 and 12 1 states, which lie 4204.8 and 4407.4 keV above the normal-deformed yrast states of the same spins.Superdeformation has been a central focus in the study of nuclear structure. Long cascades of rotational transitions between superdeformed (SD) states have been observed in nuclei with mass ϳ130, 150, 190 [1,2], and 80 [3]. While the rotational transitions have been easy to detect with modern Ge arrays, it has been much harder to localize the SD bands (in excitation energy and spin) and to link them to the normal-deformed (ND) yrast states. For example, in the mass 150 and 190 regions, the intraband transitions of more than 100 SD bands have been found; yet, despite many attempts, there is no band for which the exact excitation energies, spins, and parity have been conclusively determined. The location of a SD band in 143 Eu was proposed [4], based on a twophoton sum-peak technique. However, the low statistics of the peaks suggest that confirmation is needed, and their placements in the level scheme require substantiation by coincidence relationships. In contrast, in the mass 130 region, some strongly deformed bands lie only ϳ0.8 MeV above the ND yrast states and it has then been possible to identify many of the decay pathways between the SD and less deformed ND states [5]. Therefore, one of the most pressing challenges in the study of superdeformation in the A 150 and 190 regions is the accurate determination of the excitation energies, spins, and parities of the parent levels of the known SD band transitions.The SD bands in these regions are especially interesting because they lie at high energy, yet they are isolated in a well-defined minimum (false vacuum) at the point where they decay out to the ND states in the true vacuum. The decay is believed to occur when a SD level, embedded in a sea of hot ND states, acquires a small component of a hot compound state, and decays through this component [6]. This description is supported by the measured g decay spectrum, which has a statistical quasicontinuous character [7], and by its agreement with a calculation of the statistical spectrum [8]. From the measured decay spectrum, Henry et al. [7] deduced that the SD state of 192 Hg lies 4.3 6 0.9 MeV above the ND yrast line at the point of decay. A similar value is expected in 194 Hg since its quasicontinuous spectrum [9] is almost identical to that in 192 Hg.Decay from SD bands and from resonant thermalneutron capture both represent statistical deexcitation of narrow highly excited states. The g decay spectra contain sharp high-energy primary g rays (from decays to low-lying states) and low-energy secondary g rays (from subsequent transitions between the low-lying states), in addition to the quasicontinuous componen...

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Section: (A)] the Highenergy Lines [Insupporting

confidence: 82%

Excitation Energies and Spins of a Superdeformed Band in194Hgfrom One-Step Discrete Decays to the Yrast Line

Khoo¹,

Carpenter²,

Lauritsen³

et al. 1996

Phys. Rev. Lett.

Self Cite

151

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“…A refined comparison between the experimental results and predictions from theory is based on the kinetic moment of inertia J kin (MoI), which is deduced from the transition energies E γ of the ground-state rotational band [24][25][26]: [11] or based on γ γ -coincidence relationships. Tentative assignments are given in brackets.…”

Section: Discussionmentioning

confidence: 99%

Spectroscopy of the neutron-rich actinide nucleusU240following multinucleon-transfer reactions

Birkenbach¹,

Vogt²,

Geibel³

et al. 2015

Phys. Rev. C

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Background: Nuclear structure information for the neutron-rich actinide nuclei is important since it is the benchmark for theoretical models that provide predictions for the heaviest nuclei. Purpose: γ -ray spectroscopy of neutron-rich heavy nuclei in the actinide region. Method: Multinucleon-transfer reactions in 70 Zn + 238 U and 136 Xe + 238 U have been measured in two experiments performed at the INFN Legnaro, Italy. In the 70 Zn experiment the high-resolution HPGe Clover Array (CLARA) coupled to the magnetic spectrometer PRISMA was employed. In the 136 Xe experiment the high-resolution Advanced Gamma Tracking Array (AGATA) was used in combination with PRISMA and the Detector Array for Multinucleon Transfer Ejectiles (DANTE). Results: The ground-state band (g.s. band) of 240 U was measured up to the 20 + level and a tentative assignment was made up to the (24 + ) level. Results from γ γ coincidence and from particle coincidence analyses are shown. Moments of inertia (MoI) show a clear upbend. Evidence for an extended first negative-parity band of 240 U is found. Conclusions: A detailed comparison with latest calculations shows best agreement with cranked relativistic Hartree-Bogoliubov (CRHB) calculations for the g.s. band properties. The negative-parity band shows the characteristics of a K π = 0 − band based on an octupole vibration.

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“…The empirical formula I(I + 1) expansion [1] and the a[pl + b(I + 1) -1] approximation [3] have been used successfully to determine the spins of the SD bands in the A 190 region. However, when they are applied to A 150 region, the quality of the Gt to the observed energies is good but insensitive to spin assignment.…”

mentioning

confidence: 99%

Cranking Bohr-Mottelson Hamiltonian applied to superdeformed bands in theA∼150 region

Fang

1995

Phys. Rev. C

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The superdeformed bands in the A 150 region are studied with the cranking Bohr-Mottelson Hamiltonian proposed by us. The transition energies can be represented satisfactorily and the level spins are extracted. The validity of our formulas and the reliability of the spin determinations are discussed.PACS number(s): 21.10. Re, 21.60.Ev, 27.60. +j, 27.70.+q The superdeformed (SD) bands in the A 190 region have been well studied and several models have been proposed for their spin determinations with similar results [1 -5]. In contrast to the A 190 region, the SD bands in the A 150 region have higher spins and their spin determinations are more difficult. The empirical formula I(I + 1) expansion [1] and the a[pl + b(I + 1) -1] approximation [3] have been used successfully to determine the spins of the SD bands in the A 190 region. However, when they are applied to A150 region, the quality of the Gt to the observed energies is good but insensitive to spin assignment. In the Harris cu expansion method, another difficulty is encountered in the A 150 region, as will be discussed in this paper. Cheng-Li Wu et al. [6] have pointed out that any theoretical spin determination must be model dependent and the present status of the models is not accurate enough to make a reliable spin determination. Hence, it is worthwhile to develop more reliable models which may contribute towards the spin determination and the nuclear structure studies of the SD states, especially for I the A 150 region. Recently, we have developed a nuclear rotationvibration model based on the cranking Bohr-Mottelson (BM) Hamiltonian [7]. The model has been successfully applied to the normally deformed bands [7] and the SD bands in the A 190 region [5]. As commented in our former papers [5,7], it is a well-founded model with physically significant parameters. In [7,5], we have given the cranking BM Hamiltonian for the normally deformed states and the SD states in the A 190 region. The SD bands in the A 150 region have higher rotational frequencies, hence next order (fourth-order) perturbation should be considered in the derivation of the BM Hamiltonian &om the cranked shell model [8]. The fourth-order perturbation term can be approximately written as Daz~, where ao is the quadrupole deformation parameter,~is the rotational frequency, and D is the coefficient of the fourth-order perturbation term. Then the cranking BM Hamiltonian is written as H' = --, --Bt(3ap + 2a2)u) + Dao~+ E(ap, a2), 2Bo Oao 4B2 &a2 E(ao, a2) = U(ao) + 2 C2a2 (2) Hence, the ao-dependent part of the effective potential can be written as where E(ap, a2) is the static collective potential; ap and a2 are the quadrupole deformation parameters; and Bo, Bt, and B2 are the mass parameters [7,5]. The superdeformed states of the nuclei in the A 150 region are mainly axisymmetrical deformations [ll]. In this case, E(ap, a2) is assumed separable [5,7]: V(ap,~) = U(ap) -2Bicu ao+ D~a o .For the SD band to exist, we shall assume V(ap, ur) has a clear minimum at a certain ao value which depends slight...

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Level spin for superdeformed nuclei nearA=194

Cited by 78 publications

References 20 publications

Excitation Energies and Spins of a Superdeformed Band in194Hgfrom One-Step Discrete Decays to the Yrast Line

Excitation Energies and Spins of a Superdeformed Band in194Hgfrom One-Step Discrete Decays to the Yrast Line

Spectroscopy of the neutron-rich actinide nucleusU240following multinucleon-transfer reactions

Cranking Bohr-Mottelson Hamiltonian applied to superdeformed bands in theA∼150 region

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