Comparative quadrupole moments of triaxial superdeformed states in 163, 164, 165Lu

Schönwaßer, G.; Hübel, H.; Hagemann, G.B.; Amro, H.; Clark, R. M.; Cromaz, M.; Diamond, R. M.; Fallon, P.; Herskind, B.; Lane, G. J.; Ma, Wenlong; Macchiavelli, A. O.; Ødegård, S. W.; Sletten, G.; Ward, D. R.; Wilson, J. N.

doi:10.1140/epja/i2002-10097-5

Cited by 38 publications

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“…These two moments are directly related to the in-band and out-of-band B(E2) values of the wobbling band [7], the measurements of which can uniquely determine the moments as has actually been done in the case of the Lu isotopes [21,22]. In place of the two moments, equivalent two quantities, the magnitude of moments Q and the triaxiality parameter γ are usually used:…”

Section: A Basic Definition Based On the Intrinsic Quadrupole Momentsmentioning

confidence: 99%

“…The measurements of both the branching ratio and the life time have been done for some TSD bands [21,22] recently, so that one can study B(E2) out and B(E2) in separately. However, their ratio is directly connected to the triaxial deformation in the high-spin wobbling phonon treatment of the rotor model [7], which gives, in good approximation,…”

Section: B(e2) Ratio Of the Wobbling Bandmentioning

confidence: 99%

“…In order to pin down how much the TSD nucleus deforms triaxially, it is crucial to measure the E2 transition probabilities. The measurements of the B(E2) [21,22] of not only in-band (intraband), but also out-of-band (interband) transitions of the states in the yrast TSD band and those in the excited wobbling band are necessary to obtain the information about the triaxial deformation. The detailed study using the particle-rotor model [8,23,24], with an odd i 13/2 proton coupled to the triaxial rotor, which is suitable for the description of odd Lu TSD bands, revealed that the observed ratio of the out-of-band to the in-band B(E2)'s, B(E2) out /B(E2) in , is consistent with the triaxiality parameter γ ≈ +20 • .…”

Section: Introductionmentioning

confidence: 99%

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Parametrizations of triaxial deformation andE2transitions of the wobbling band

2008

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There are various different definitions for the triaxial deformation parameter "γ ". It is pointed out that the parameter conventionally used in the Nilsson (or Woods-Saxon) potential, γ (pot:Nils) [or γ (pot:WS)], is not appropriate for representing the triaxiality γ defined in terms of the intrinsic quadrupole moments. The difference between the two can be as large as a factor two in the case of the triaxial superdeformed bands recently observed in Hf and Lu nuclei, i.e., γ (pot:Nils) ≈ 20 • corresponds to γ ≈ 10 • . In our previous work, we studied the wobbling excitations in Lu nuclei using the microscopic framework of the cranked Nilsson mean-field and the random phase approximation. The most serious problem was that the calculated B(E2) value is about factor two too small. It is shown that the origin of this underestimate can mainly be attributed to the small triaxial deformation parameter γ ≈ 10 • that corresponds to γ (pot:Nils) ≈ 20 • . If the same triaxial deformation parameter is used as in the analysis of the particle-rotor model, γ ≈ 20 • , the calculated B(E2) gives correct magnitude of the experimental data.

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Section: A Basic Definition Based On the Intrinsic Quadrupole Momentsmentioning

confidence: 99%

Section: B(e2) Ratio Of the Wobbling Bandmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Parametrizations of triaxial deformation andE2transitions of the wobbling band

2008

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“…Very similar B͑E2͒ strengths for the in-band transitions are expected, as the wobbling bands are built on the same intrinsic structure. Measurements have been attempted in 163 Lu [13][14][15], but only for the yrast band and the different experiments are not in agreement.…”

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Quadrupole moments of wobbling excitations inLu163

et al. 2004

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Lifetimes of states in the triaxial strongly deformed bands of 163 Lu have been measured with the Gammasphere spectrometer using the Doppler-shift attenuation method. The bands have been interpreted as wobblingphonon excitations from the characteristic electromagnetic properties of the transitions connecting the bands. Quadrupole moments are extracted for the zero-phonon yrast band and, for the first time, for the one-phonon wobbling band. The very similar results found for the two bands suggest a similar intrinsic structure and support the wobbling interpretation. While the in-band quadrupole moments for the bands show a decreasing trend towards higher spin, the ratio of the interband to the in-band transition strengths remains constant. Both features can be understood by a small increase in triaxiality towards higher spin. Such a change in triaxiality is also found in cranking calculations, to which the experimental results are compared.

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“…But perhaps we might gain some perspective by investigating how the quadrupole deformation of the TSD and ND structures evolves with both spin and neutron number in neighboring TSD nuclei. A trend toward smaller deformation with increasing neutron number is observed in the TSD structures in 163,164,165 Lu [15,16]. In contrast, an increase in the deformation of the ND structures with increasing N is expected.…”

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Competing modes of excitations and the decay out of the triaxial strongly deformed well inLu167

Amro

Hagemann²,

et al. 2005

Phys. Rev. C

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An unexpected strong interaction between normal deformed and triaxial strongly deformed levels at high spin, ∼32h, is observed in 167 Lu. This constitutes the first observation of accidental degeneracy, at such high spins, causing cross talk between levels in the normal deformed and in the second potential well in any known mass region. Furthermore, evidence of quasi-particle excitations highly competing with the wobbling excitation mode in a triaxial superdeformed well has been established in 167 Lu.Triaxial strongly deformed (TSD) rotational bands in the mass region around A ∼ 165 have received considerable attention recently. Experimentally, over 30 TSD bands are reported in this mass region in Lu and Hf isotopes [1]. Only a few of these bands are firmly connected to the normal deformed (ND) yrast states. In 163,165,, and possibly 161 Lu [6], wobbling phonon excitations are established. The wobbling mode, uniquely related to the triaxiality of the nuclear system, was identified based on the observed properties of the decay between the bands constituting the family of wobbling phonon excitations. Most recently, a new excited TSD band, which is interpreted as likely to be a multi-quasiparticle excitation, was observed in 163 Lu [7]. The excitation energy of this band is higher than the one-phonon but comparable to the two-phonon wobbling excitation established in this nucleus. Thus, not only shape coexistence between ND and TSD structures but also an interplay of collective and multi-quasiparticle excitations in the TSD well exist.Here we report on the strong interaction between the ND and TSD levels observed in 167 Lu at high spins, ∼32h, in addition to the interaction at lower spin that mediates the main decay out. Such an interaction is at variance with the common observation that the absence of a well-defined barrier between the two wells occurs only at the decay out points (i.e., lowest spins). In addition, we report on the discovery of a new excited TSD band in 167 Lu coexisting and strongly competing with the one-phonon wobbling excitation previously established in this nucleus [5]. The multi-quasiparticle interpretation of this band is based on its observed decay out properties. This interpretation is supported by Cranking calculations with the UC code [8,9].The 123 Sb( 48 Ca,4n) reaction was used to populate states in 167 Lu. The 48 Ca beam at 203 MeV was provided by the 88-inch cyclotron at Lawrence Berkeley National Laboratory. γ -ray coincidences were measured with the Gammasphere array, which, at the time of the experiment, consisted of 100 Compton-suppressed Ge detectors. A total of 2.2 × 10 9 events, requiring five or more Compton-suppressed Ge detectors in prompt coincidence, was collected and used in the off-line analysis. The coincidence events were sorted into a threedimensional histogram (cube) using the Radware software package [10]. The extensive search through the coincidence cube, revealed a third TSD band, TSD3, in addition to the wobbling band built on the πi 13/2 yrast TSD band report...

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Comparative quadrupole moments of triaxial superdeformed states in 163, 164, 165Lu

Cited by 38 publications

References 1 publication

Parametrizations of triaxial deformation andE2transitions of the wobbling band

Parametrizations of triaxial deformation andE2transitions of the wobbling band

Quadrupole moments of wobbling excitations inLu163

Competing modes of excitations and the decay out of the triaxial strongly deformed well inLu167

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