Experimental Evidence for Shape Coexistence in 97Sr59 and Implications for the Structure of the Odd-Odd Isotone 98Y

Lhersonneau, G.; Kratz, K. L.; Ohm, H.; Pfeiffer, B.; Sistemich, K.

doi:10.1007/978-3-642-73958-3_8

Cited by 3 publications

(3 citation statements)

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“…A convincing experimental proof of shape coexistence in 978r would be the observation of a rotational band. (Part of the results of this work have been presented previously [7][8][9][10]). …”

Section: Introductionmentioning

confidence: 95%

Structure of theN=59 nucleus97Sr: coexistence of spherical and deformed states

Lhersonneau

Pfeiffer

Kratz

et al. 1990

Z. Physik A - Atomic Nuclei

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A band with a rotational pattern based on a state at 585.1 keV has been identified in the N= 59 neutron-rich nucleus 97St. Its properties lead to the [422] 3/2 Nilssonorbital assignment for the band head. There is evidence for a second band with the head at 644.7 keV and the configuration [-541] 3/2. Since the ground state and the lowest excited levels are spherical, shape coexistence is established for 97Sr. A deformed nature of several levels at 500-600 keV results also from QRPA-model calculations. The structure of the low-lying spherical levels has been studied in the frame of the IBF model. The results of the present investigations lead to a better understanding of the N= 59 isotones which constitute the link between the spherical and deformed nuclei at A ~ 100 as a species with shape coexistence but without any indications of particular softness.

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Section: Introductionmentioning

confidence: 95%

Structure of theN=59 nucleus97Sr: coexistence of spherical and deformed states

Lhersonneau

Pfeiffer

Kratz

et al. 1990

Z. Physik A - Atomic Nuclei

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“…Surely also the rapid change of the quasiparticle pattern [12] contributes. An interesting aspect is the occurence of shape coexistence in N= 59 isotones like 978r [46,47]. In 1~ no rotational structures have been observed as yet, see also [14].…”

Section: Resultsmentioning

confidence: 96%

Structure of the Triplet of low-lying states in101Mo

Seyfarth

Güven

Kardon

et al. 1991

Z. Physik A - Hadrons and Nuclei

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The properties of the triplet of low-lying states in l~ have been studied through spectroscopy of the y radiation following thermal neutron capture in ~~176 and fldecay of ~~ and through a measurement of the proton angular distributions in the ~~176 reaction with 14 MeV deuteron energy. The half-lives of the 13.5 keV state and the 57.0 keV 5/2 + state have been measured as 226 (7) and 133(7)ns, respectively. These values and the quadrupole/dipole mixing ratios of the 13.5 keV and 43.5 keV transitions yield spin and parity 3/2 + for the 13.5 keV level. The E2 components in the 13.5 (3/2 + ~1/2 +) and 43.5keV (5/2+--+3/2 +) transitions are "( 8.10 -4 and 54(9)%, respectively. The possibility of an additional state near to the 57.0 keV level is discussed. IBFM/PTQM calculations, taking into consideration the transitional character of the l~176 boson core, account for the electromagnetic-transition and transfer-reaction pattern of the triplet of states.

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“…This results from conversion measurements of the 44.3 keV and 59.7 keV transitions to the positive-parity levels at 600.5 and 585.1 keV (see Fig. 3 in [3]), from which in both cases El multipolarity rather than M1 is deduced [12]. As for the level at 600.5 keV, the experimental log(ft)=5.…”

mentioning

confidence: 98%

Shape coexistence in theN=59 isotone97Sr

Lhersonneau

Pfeiffer

Kratz

et al. 1988

Z. Physik A - Atomic Nuclei

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Experimental evidence for shape coexistence in the N=59 isotone 97Sr is presented. The ground state and the lowest excited levels are confirmed to be spherical. At 585.1 keV, a K=3/2 rotational band built on the v[422 3/2] Nilsson configuration has been identified. Nilsson orbital assignments for three further levels of deformed origin are proposed. The results are compared to RPA shell-model predictions.For the 38Sr, 3gY and 4oZr nuclei near A=IO0, a sudden onset of strong deformation at N=60 has been observed, whereas the lighter isotopes up to N=58 keep a spherical shape [1]. This raises the question about the nature of the N=59 intermediate nuclei. The striking similarities between the lowest excited levels in the N=59 isotones 97Sr and 99Zr on the one hand, and the spherical N=57 isotones 95Sr and 97Zr on the other hand [2][3][4] suggest sphericity for the low-excitation region of 97Sr. Recent Laser-spectroscopic measurements have furthermore shown that ~TSr has a groundstate (g.s.) spin of I=1/2 which has been interpreted as a vsl/2 shell-model state [5]. On the other hand, quasi-particle RPA calculations [6] have shown that the overall shape of the GamowTeller (GT) strength function of ~TSr could only be reproduced when strong prolate deformation was assumed [7]. Therefore, we have carefully reinvestigated the level scheme of 97Sr in order to search for a possible rotational band as a clear signature of deformation, and with this of shape coexistence in this N=59 isotone.The isotope 97Sr was produced as ~-decay daughter of 97Rb at the on-line mass separator OSTIS [8] at the ILL Grenoble. Singles and ~-~-t coincidence spectra have been recorded. Conversion coefficients were determined by the fluorescence method. For the lifetime measurements the centroid-shift method was used [9].According to the recent spin determination [5], to the GT-decay properties of 97Sr to 97y, and to our shell-model calculations [6,7], the J==1/2 § g.s. of 97Sr is associated to the spherical (~2~ 0.05) neutron configuration (gT/2)zsl/2. This assignment, together with the known multipolarities of the ~-transitions [3], allows to deduce J~= 3/2 + , respectively 7/2 + for the first two excited states at 167 and 308 keV (see Fig. I). These levels have a character quite similar to the corresponding ones in the spherical N=57 isotopes 95 97 Sr and Zr. With this interpretation, the isomeric character (t~/2=170 ns) of the g7/2 state at 308 keV results from the E2 deexcitation to the first excited level with a transition rate close to the single-particle value, and is not associated with the ~ [404 9/2] intruder as proposed in [10]. Thus, the lowest levels of 97Sr have spherical character.In contrast, the levels at 585.1 and 687.1 keV [3] together with the new level at 822.4 keV (see Fig. 1) are proposed to form a rotational band. The first two states are populated in ~-decay of the ~[431 3/2] g.s. of 97Rb with log(ft)=5.6, each, allowing I n= (i/2-5/2) + for both of them. Selection rules for ~-transitions further limit the sp...

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Experimental Evidence for Shape Coexistence in 97Sr59 and Implications for the Structure of the Odd-Odd Isotone 98Y

Cited by 3 publications

References 10 publications

Structure of theN=59 nucleus97Sr: coexistence of spherical and deformed states

Structure of theN=59 nucleus97Sr: coexistence of spherical and deformed states

Structure of the Triplet of low-lying states in101Mo

Shape coexistence in theN=59 isotone97Sr

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