Superdeformation in194Pb

Theine, K.; Hannachi, F.; Willsau, P.; Hübel, H.; Mehta, D.; Schmitz, W.; Yang, Chunxiang; Fossan, D. B.; Grawe, H.; Kluge, H.; Maier, K. H.

doi:10.1007/bf01904169

Cited by 21 publications

(25 citation statements)

References 7 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[21). In this nucleus a SD band of 14 transitions with energies of 169, 213, 256, 298, 340, 380,419,458, 496, 533, 568, 603, 637 and (673) keV has been observed [3][4][5]. The lifetimes of the SD states are expected to lie in the range of a fraction of a picosecond to several picoseconds; we therefore have applied the Doppler-shift attenuation method (DSAM) for our measurement.…”

mentioning

confidence: 92%

Transition quadrupole moments of superdeformed states in194Pb

Willsau

Hübel

Körten

et al. 1992

Z. Physik A - Hadrons and Nuclei

Self Cite

View full text Add to dashboard Cite

Lifetimes of superdeformed states in 194pbwere measured by the Doppler-shift attenuation method. Quadrupo]e moments around 20 eb, that are constant over the observed frequency range, are derived. The results rule out large centrifugal stretching effects.Superdeformed rotational bands have recently been discovered in several nuclei in the mass 190 region. Most of these bands show surprisingly similar moments of inertia d (2) and some of them even have "identical" 7-ray energies. The dynamic moments of inertia show a rise of about 40% over the observed frequency range of the SD bands. This rise may be caused by a deformation increase with increasing frequency (centrifugal stretching) or by rotation alignment and pairing effects. Alignment would require the presence of pair correlations in the SD states but these pair correlations would gradually be quenched by the alignment of quasiparticles, and the combined effect would lead to the increase of the dynamic moments of inertia. Up to now only one experiment has been performed in the mass-190 region that addresses this question: a measurement of lifetimes of SD states in 19~1tg from which transition quadrupole moments of individual states were deduced [1]. The results show a rather constant quadrupole moment of about 19 eb which confirms the large deformation (axis ratio ~ 1.65/1) but rules out a drastic deformation change within the SD band of 192Hg.In this work we report on a lifetime measurement of SD states in 194ph (for a preliminary report see ref. [21). In this nucleus a SD band of 14 transitions with energies of 169, 213, 256, 298, 340, 380,419,458, 496, 533, 568, 603, 637 and (673) keV has been observed [3][4][5]. The lifetimes of the SD states are expected to lie in the range of a fraction of a picosecond to several picoseconds; we therefore have applied the Doppler-shift attenuation method (DSAM) for our measurement. High-spin states in 194pb were populated in the 15~ reaction at 205 MeV. The 4sca beam was provided by the 88-inch cyclotron at the Lawrence Berkeley Laboratory. A 1.1 mg/cm 2 thick metallic Sm foil, enriched in '5~ on a 10 mg/cm 2 Au backing was used as a target. Gamma-ray coincidences were measured with the HERA spectrometer array, consisting of 20 Compton-suppressed Ge detectors and an inner BGO ball of 32 elements which was used as a sum-energy and multiplicity filter. The analysis was based on a total of 200 x 106 events with the requirement of at least 2 Oe and 7 BOO detectors firing and a minimum sum energy of 2.2 MeV.The events were sorted into 77-coincidence matrices, with either the forward (37 ~ ) or the backward (153 ~ ) detectors on the projection axis and any detector on the gate axis. The low-energy 7-rays up to the 340 keV transition were all emitted after the recoihng nuclei had come to rest in the Au backing. Therefore, the 7-ray peaks show no Dopplerbroadening and narrow coincidence gates could be set on these transitions. The resulting coincidence spectra showed Doppler-shifted line shapes for the 7-ray transiti...

show abstract

mentioning

confidence: 92%

Transition quadrupole moments of superdeformed states in194Pb

Willsau

Hübel

Körten

et al. 1992

Z. Physik A - Hadrons and Nuclei

Self Cite

View full text Add to dashboard Cite

show abstract

“…The mean-field approach was exclusively applied [3] to the early studies of SD states known before 2000 [4], such as in the A 80 (e.g., 84 Zr 44 [5]), A 150 (e.g., 152 Dy 86 [6]), and A 190 (e.g., 194 Hg 114 [7]) mass regions. The main reason is that nuclei in these SD archipelagoes belong to heavy-and mediumweight classes.…”

Section: Introductionmentioning

confidence: 99%

Description of superdeformed bands in lightN=Znuclei using the cranked Hartree-Fock-Bogoliubov method

2007

Phys. Rev. C

View full text Add to dashboard Cite

Superdeformed states in light N = Z nuclei are studied by means of the self-consistent cranking calculation (i.e., the P+QQ model based on the cranked Hartree-Fock-Bogoliubov method). Analyses are given for two typical cases of superdeformed bands in the A 40 mass region, that is, bands where backbending is absent ( 40 Ca) or present ( 36 Ar). Investigations are carried out particularly for the following points: cross-shell excitations in the sd and pf shells; the role of the g 9/2 and d 5/2 orbitals; the effect of nuclear pairing; and the interplay between triaxiality and band termination.

show abstract

“…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].…”

mentioning

confidence: 88%

A pair of excited superdeformed bands in196Pb

Severen

Körten

Hübel

et al. 1995

Z. Physik A - Hadrons and Nuclei

Self Cite

View full text Add to dashboard Cite

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...

show abstract

Superdeformation in194Pb

Cited by 21 publications

References 7 publications

Transition quadrupole moments of superdeformed states in194Pb

Transition quadrupole moments of superdeformed states in194Pb

Description of superdeformed bands in lightN=Znuclei using the cranked Hartree-Fock-Bogoliubov method

A pair of excited superdeformed bands in196Pb

Contact Info

Product

Resources

About