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Tf, Wang; Kuhnert, A.; Ja, Becker; Henry, E. A.; Sw, Yates; Brinkman, M. J.; Cizewski, J. A.; Fa, Azaiez; Deleplanque, M. A.; Rm, Diamond; Draper, J. E.; Wh, Kelly; Körten, W.; Macchiavelli, A. O.; Rubel, E.; Stephens, F. S.

doi:10.1103/physrevc.43.r2465

Cited by 25 publications

(10 citation statements)

References 13 publications

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“…These data confirmed and extended the known yrast SD band in 196Pb [5][6][7], but no further bands could be identified -probably because of the lank of clean coincidence gates. In the second step the threeand (unpacked) higher-fold events (94.5.…”

Section: Pacssupporting

confidence: 89%

A pair of excited superdeformed bands in196Pb

Severen

Körten

Hübel

et al. 1995

Z. Physik A - Hadrons and Nuclei

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Abstract. Two excited superdeformed bands have been found in ~96Pb using the GASP 7-ray spectrometer array. They are signature-partner bands with a small signature splitting developing at higher frequencies, similar to bands 2 and 3 in the isotone 194Hg. The bands are probably built on an excited neutron configuration. They show an unusual incremental alignment of 1/2 h with respect to the a94Pb core. 21.10.-k; 23.20.-v; 27.80.+w The region of nuclei with mass numbers around A = 190 is now a well established area of superdeformation with about 50 superdeformed (SD) rotational bands known [1]. However, as long as the connections of the bands to the normal-deformed states are missing, no direct spin determination is possible and configuration assignments depend on a detailed study of the systematic properties of yrast and excited SD bands. In this work we report on the observation of the first two excited SD bands in 196pb. This nucleus is the isotone of 194Hg where two excited SD bands have been known [2-4] for some time. PACS:High-spin states in 196pb were populated in the reaction 17~176 at a beam energy of 143 MeV at the LNL XTU tandem accelerator. Gamma-ray coincidences were measured using the GASP array of 40 Compton-suppressed Ge detectors and an inner ball of 80 BGO scintillation counters. The target consisted of a stack of two selfsupporting foils of l~~ (enrichment 97%) with a thickness of 750 #g/cm 2 each. A total of about 109 two-and higher-fold coincidence events were recorded.In the first step of the off-line analysis all coincidences were unpacked into two-fold events and sorted into a two-dimensional En-E ~ matrix. These data confirmed and extended the known yrast SD band in 196Pb [5][6][7], but no further bands could be identified -probably because of the lank of clean coincidence gates. In the second step the threeand (unpacked) higher-fold events (94.5. 106 ) were sorted into a three-dimensional matrix of the "),-ray energies (E~-En-E ~ cube) and double-gated coincidence spectra were analysed. The search for new bands was guided by the dynamic moments of inertia of known SD bands in this region. In that way we could exclude that known bands in neighbouring nuclei are present in our data within the statistical limits. But when the starting energies of the bands were allowed to vary, two new bands were found that have moments of inertia which are similar to the yrast SD band in 194pb [8,9]. One of the new bands has transition energies close to those of one of the bands in 195T1 [10]. In our experiment, however, that nucleus is hardly produced at all.The three bands in 196pb are shown in Fig. 1. All combinations of clean double-gated spectra have been added. The two new bands have intensities of about 35% of that of the yrast SD band. The assignment of the new bands to 196pb is still somewhat tentative since the coincidences with the low-lying transitions are not conclusive. However, as we do not observe any of the known SD bands, in particular in a95pb or 193Hg which are the other nuclei populat...

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Section: Pacssupporting

confidence: 89%

A pair of excited superdeformed bands in196Pb

Severen

Körten

Hübel

et al. 1995

Z. Physik A - Hadrons and Nuclei

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“…The present work was also able to unambiguously verify the assignment of the previously reported SD band in 198 Pb [16,17]. Thus it has been possible to extend the region of known SD bands in the lead isotopes.…”

Section: Pacssupporting

confidence: 83%

Superdeformed bands and ‘shears’ bands in 197Pb and 198Pb

et al. 1997

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Excited states in 197 Pb and 198 Pb, produced in the 186 W ( 18 O,xn) reaction, were studied using the EUROGAM phase 2 γ ray spectrometer array. Two new superdeformed bands have been observed in 197 Pb, and the existence of a superdeformed band in 198 Pb has been confirmed. The increased statistics provided by the latest generation of arrays has resulted in the reordering of some of the previous known cascades of magnetic dipole transitions, with the first observation of the extremely weak E2 crossover transitions.High spin states in 197 Pb and 198 Pb nuclei [1,2] were produced in the 7n and 6n channels of the 186 W ( 18 O,xn) reaction at nominal laboratory bombarding energies of 110 and 115 MeV. Gamma rays were detected with the EUROGAM phase 2 spectrometer [3], with approximately 1.2 × 10 9 events collected in which at least four γ rays were in prompt time coincidence. The data were unpacked using the technique of Beausang et al. [4] and sorted into RADWARE format [5] cubes.Two new superdeformed (SD) bands, which were observed with an intensity of ∼ 0.2% and 0.1%, respectively, of the 197 Pb reaction channel, have been assigned to this nucleus as they were found to be in coincidence with lead x rays and several low-lying states [6]. These bands are seen more strongly in the 115 MeV than the 110 MeV data set, where the production of 198 Pb dominates. They are believed to be signature partner bands as crosstalk has been observed: lower band members from band 2 are seen in coincidence with band 1, and vice versa, with an intensity that decreases as the rotational frequency increases.The dynamic moments of inertia (J (2) = dI/dω) for the two bands in 197 Pb follow very closely those of bands 1 and 2 in 195 Pb [7], and a pair of similar bands have been reported in 193 Pb [8]. These bands are thought to be based upon the odd neutron occupying either the favoured or unfavouredsignature Present address: Department of Physics and Astronomy, McMaster University, Hamilton, ON L8S 4M1, CanadaFig. 1.Triple-gated quadruples spectra of the two SD bands in 197 Pb, with gates set on all the known transitions in the band. Insets show the relative transition intensities, corrected for E2 internal conversion, as a percentage of the largest peak intensity in the band. Also shown is the 1005 keV γ ray from 197 Pb components of an N=7 neutron intruder orbital. The expected alignment [9, 10] of j 15/2 neutrons is then prevented by Pauli blocking, producing a relatively constant J (2) . However, because there is less fission competition in the 197 Pb system, the new bands are observed to extend to higher rotational fre-

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“…As a result of the analysis of these data, two sequences of 7 rays, with properties characteristic of SD bands of this mass region, have been observed. One of the bands corresponds to the known SD sequence in~Pb [8,18,19]. The lowest seven transitions of the other band correspond closely in energy to those of a very weak cascade which has been previously assigned to~@ sPb [19].…”

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confidence: 86%

Superdeformation in the Pb nuclei and the evolution of the dynamic moments of inertia

et al. 1994

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Two weakly populated rotational bands with energy spacings characteristic of superdeformation (SD) have been found in the W( O,zn) reaction at a beam energy of E = 113 MeV. One of the bands corresponds to the known sequence in Pb, the other to an extremely weak cascade previously assigned to Pb. Both bands have been extended to higher frequency. The behavior of the dynamic moments of inertia for the known SD bands in the Pb nuclei are discussed. Deformation and pairing self-consistent cranked Woods-Saxon calculations of the 9 moments of inertia for bands in the even-even isotopes Pb are presented. PACS number(s): 27.80.+w, 23.20.Lv, 21.10.Re, 21.60.Ev Superdeformation (SD) in the A 190 region is well established experimentally with over 30 SD bands identified in the Hg, Tl, and Pb nuclei [1]. These observations con6rm the various theoretical predictions of superdeformation for these nuclei [2 -5], and have extended the study of nuclei under the extreme conditions of large deformation and high angular momentum.The dynamic moment of inertia, 9(2l (dI/der 4/b, E~), and the quadrupole moment are the two quantities most readily deduced from experiment and compared with theory. Plots of the 9( ) moments of inertia for many of the bands in the A 190 region show a steady rise with increasing rotational frequency cu. The quadrupole moments of states in several bands have been established through lifetime measurements [6 -12]. The results con6rm the superdeformed nature of the structures and also show that the deformation remains constant over all the in-band states down the cascade to the point at which the levels depopulate to states in the normal-deformed well. This indicates that the rise in 9( ) is not due to centrifugal stretching, which would lead to a change in deformation over the band. Instead, the behavior of the dynamic moments of inertia seems to be connected with the gradual alignment of pairs of nucleons occupying specific high-N intruder orbitals (namely, jizi2 neutrons and iisi2 protons) under the in8uence of weak pairing correlations. *Permanent address: Institute for Atomic Physics, Tandem Laboratory, Bucharest -Magurele R -79600, Romania.Although theory seems able to qualitatively describe the evolution of the 9( ) moments of inertia rather well, severe de6ciencies remain. For example, it has been predicted that for iso isiHg [13] a downturn in 9(il should occur at high &equency after all the quasiparticle align. -ments have taken place -this feature has not been observed. However, a recent investigation [14] reports a possible Battening of the 9( ) at the highest rotational frequencies for the SD band in Hg. For i94' 96Pb calculations suggest that a downturn of G( ) should take place at the point where the j&5i2 quasineutron alignment has Gnished, and before the alignment of the i&3y2 quasiprotons becomes signi6cant. No such effect is observed in the data. These features suggest that the crossings may be delayed in frequency and that more sophisticated calculations, which include effects such as higher...

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Superdeformation inPb198,196

Cited by 25 publications

References 13 publications

A pair of excited superdeformed bands in196Pb

A pair of excited superdeformed bands in196Pb

Superdeformed bands and ‘shears’ bands in 197Pb and 198Pb

Superdeformation in the Pb nuclei and the evolution of the dynamic moments of inertia

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