Lifetime measurements in 
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Aprahamian, A.; Lesher, S. R.; Casarella, Clark; Börner, Hans G.; Jentschel, M.

doi:10.1103/physrevc.95.024329

Cited by 8 publications

(4 citation statements)

References 56 publications

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“…These studies and others [30,32] on the nature of K π = 0 + bands in deformed nuclei predict widely varying levels of collectivity depopulating the first excited 0 + states [1].…”

Section: Introductionmentioning

confidence: 74%

Lifetime measurements in Gd156

et al. 2018

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Background: The nature of low-lying oscillations or excitations around the equilibrium deformed nuclear shape remains an open question in nuclear structure. The question revolves around the possible degrees of freedom in deformed nuclei. Rotational motion is an expected feature of deformed nuclei, the open challenge is whether the "granularity" of nuclei allows single or multiple quanta of vibrational oscillations or excitations superimposed on the equilibrium deformed shape of the nucleus. Special emphasis is placed on the K π = 0 + , β vibration whose existence is open to debate some forty years after Bohr-Mottelson-Rainwater's Nobel prize for connecting nucleon motion to the emergence of collectivity. Purpose: The 156 Gd nucleus is an excellent test case for the search of the predicted oscillations since it has one of the most developed level schemes up to 2.35 MeV and it lies in the well deformed rare-earth region of the chart of nuclides. This nucleus has previously been studied by (n, γ), (n, e −), (e,e), (p, p), (d, p), and (d, t) reactions with six known excited K π = 0 + bands. We measured level lifetimes of 156 Gd in order to determine the nature of the low-lying excited bands. Method: Lifetimes of excited states in the 156 Gd nucleus were measured following neutron capture using the grid technique at the Institut Laue-Langevin (ILL) in Grenoble, France. Results: Twelve level lifetimes were measured from four excitation bands in the 156 Gd nucleus including the lifetimes of three of the K π = 0 + bands. Conclusions: There are two K π = 0 + bands in this nucleus connected to the ground state band. Transitions from the K π = 0 + 2 band at 1049.5 keV to the ground state band are more collective than the ones from the K π = 0 + 3 band at 1168.2 keV. The moments of inertia of the various K π = 0 + , the K π = 2 + , and the K π = 4 + bands show that all the bands except the K π = 0 + 3 band at 1168.2 keV have nearly identical moments of inertia with the ground state band pointing to the fact that all of the bands discussed here with the exception of this indicating K π = 0 + 3 band seem to be collective excitations built on the ground state. This result is consistent with various theoretical predictions. B(E2) calculations for transitions from the K π = 2 + band to the ground state band supports the assignment of this band as the γ band. Also, the K π = 0 + 4 and the K π = 4 + 1 bands at 1715.2 keV and 1510.6 keV, respectively, are shown to be strongly connected to the K π = 2 + γ band presenting evidence for the observation of a second set of two-phonon γγ vibrational excitations albeit with greatly varying degrees of anharmonicity in comparison to the case of 166 Er.

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“…These studies and others [30,32] on the nature of K π = 0 + bands in deformed nuclei predict widely varying levels of collectivity depopulating the first excited 0 + states [1].…”

Section: Introductionmentioning

confidence: 74%

Lifetime measurements in Gd156

et al. 2018

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“…The low-lying states of 160 Gd were studied with the (n, n γ) reaction at the University of Kentucky Accelerator Laboratory (UKAL) with monoenergetic neutrons produced by the 3 H(p, n) 3 He reaction. The scattering sample was 29.456 g of 98.12% enriched 160 Gd 2 O 3 contained in a thin-walled polyethylene cylinder 3.1 cm in height and 2.3 cm in diameter.…”

Section: Methodsmentioning

confidence: 99%

“…γ vibrations seem to be well characterized as the first K π = 2 + bands and exhibit a systematic behavior across the region of deformed nuclei with typical B(E2; 2 + γ → 0 + gs ) values of a few Weisskopf units (W.u.). In contrast, the β vibrations do not exhibit these systematic characteristics as the B(E2) values of transitions de-exciting the first excited K π = 0 + band vary greatly throughout the deformed region [1][2][3]. The question regarding the viability of the β-vibrations in deformed nuclei remains open to debate [4][5][6][7][8][9].…”

Section: Introductionmentioning

confidence: 99%

Lifetime measurements of low-spin negative-parity levels in Gd160

et al. 2017

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160 Gd(n, n γ) experiments were performed with accelerator-produced monoenergetic neutrons. Excitation functions at neutron energies from 1.5 to 2.8 MeV aided in the placement of γ rays in the level scheme and angular distributions at three neutron energies resulted in the determination of twenty eight excited-level lifetimes or limits in 160 Gd, including the lifetimes of several negativeparity levels attributed to octupole vibrations.

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“…Perhaps the most resounding criticism of labeling the first excited K=0 + excitations as a "β" vibration built on the intrinsic ground state deformation, come from the coexistence approaches claiming that the first excited K=0 + band is in fact the minimum for a competing shape and therefore coexisting minimum in the potential. Other approaches include calculations using a five dimensional collective Hamiltonian for the quadrupole vibrational and rotational degrees of freedom where instead of solving a potential in β and γ, potential energy surfaces are calculated using Relativistic Mean Field theory [3][4][5][6]. In this approach, the first excited K π =0 + excitation often ends up being a mixture of many coexisting shapes.…”

Section: Introductionmentioning

confidence: 99%

Low lying oscillations of deformed nuclei

Aprahamian

Lesher

2018

EPJ Web Conf.

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Low-lying oscillations of the intrinsic deformed shape of a nucleus remain an open challenge in nuclear structure. The question or challenge revolves around the viability of single or multiple quanta of vibrational excitations superimposed on the equilibrium, deformed shape of a nucleus. The K=2 or “γ” vibrations are fairly widespread and nominally conform to expectations whereas the existence of the K=0 or “β” vibrational excitation is yet to be distinguished from other possible origins including the coexistence of other potential minima.

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Lifetime measurements in Dy162

Cited by 8 publications

References 56 publications

Lifetime measurements in Gd156

Lifetime measurements in Gd156

Lifetime measurements of low-spin negative-parity levels in Gd160

Low lying oscillations of deformed nuclei

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