On the two first excited K = 0 bands in 238U and 240Pu

Hoogduin, J.M.; Ditzel, E.; Bałanda, A.; Boer, F.W.N. de; Bokemeyer, H.; Gerl, J.; Heyde, K.; Klinken, J. van; Krasznahorkay, A.; Salabura, P.; Wollersheim, H. J.

doi:10.1016/0370-2693(96)00798-8

Cited by 13 publications

(8 citation statements)

References 13 publications

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“…The J π = 6 + assignment to the state at 1375.0(6) keV proposed in Ref. [52] by means of the K π = 0 + 3 , J π = 6 + → K π = 0 + 1 , J π = 6 + decay observed in electron conversion, is confirmed by our (p, t) study. Furthermore, it is also recognized as a rotational bandmember of the K π = 0 + 3 band at 1090.3(1) keV, see Table III. 1559.0 keV: The state at an energy of 1559.0(1) keV could not be assigned to any rotational band.…”

Section: Kevsupporting

confidence: 89%

High-resolution (p,t) study of low-spin states in Pu240 : Octupole excitations, α
Spieker
¹
,
Pascu
²
,
Bucurescu
³

et al. 2018
Phys. Rev. C
22
1
15
0
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Background: Many nuclear-structure features have been observed in the actinides during the last decades. Especially the octupole degree of freedom has been discussed lately after the successful measurement of the B E3; 0 + 1 → 3 − 1 reduced transition strength in 224 Ra. Recent results stemming from γ-spectroscopy experiments and high-resolution (p, t) experiments suggested, that strong octupole correlations might be observed for some positive-parity states of actinide nuclei. Purpose: This work completes a series of (p, t) experiments on actinide nuclei by adding the data on 240 Pu. The (p, t) experiments allow to study low-spin states up to J π = 6 + . Besides two-nucleon transfer cross sections, spin and parity can be assigned to excited states by measuring angular distributions, and several rotational bands are recognized based on these assignments. Methods: A high-resolution (p,t) experiment at Ep= 24 MeV was performed to populate lowspin states in the actinide nucleus 240 Pu. The Q3D magnetic spectrograph of the Maier-Leibnitz Laboratory (MLL) in Munich (Germany) was used to identify the ejected tritons via dE/E particle identification with its focal-plane detection system. Angular distributions were measured at nine different Q3D angles to assign spin and parity to the excited states based on a comparison with coupled-channels DWBA calculations. Results: In total, 209 states have been excited in 240 Pu up to an excitation energy of 3 MeV. Many previously known states have also been observed and their spin-parity assignments were confirmed. However, many of the populated states have been seen for the first time, e.g., 15 new and firmly assigned J π = 0 + states. In addition, all low-spin one-octupole phonon excitations, i.e. K π = 0 − , 1 − , 2 − , 3 − , could be observed and a new candidate for the K = 3 projection is proposed. Furthermore, the double-octupole or α-cluster structure of the 0 + 2 state in 240 Pu has been studied in more detail. It is shown that the 0 + 2 state in 230 Th has a distinctly different structure. In addition, strongly excited 1 − states have been observed at 1.5 MeV and 1.8 MeV in 240 Pu. The present study suggests that similar states might be observed in 230 Th. Conclusions: At least two different and distinct structures for J π = 0 + states are present in the actinides. These are pairing states and states with enhanced octupole correlations. We have shown that it is crucial to consider negative-parity single-particle states being admixed to some K π = 0 + 2 rotational bands to understand the α-decay hindrance factors and enhanced E1-decay rates. Based on our analysis, we have identified the double-octupole or α-cluster K π = 0 + candidates from 224 Ra to 240 Pu.

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Section: Kevsupporting

confidence: 89%

High-resolution (p,t) study of low-spin states in Pu240 : Octupole excitations, α
Spieker
¹
,
Pascu
²
,
Bucurescu
³

et al. 2018
Phys. Rev. C
22
1
15
0
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“…The E1 transitions linking Bands 3 and 2 are similar in character to those linking Bands 2 and 1: within the same spin range the B(E1)/B(E2) branching ratios between out-of-band and in-band transitions for the former are of the same magnitude within errors than those observed for the latter (and the associated D 0 moments are large). Note that this result provides an explanation for the findings of Hoogduin et al [22] who reported that, while in neighboring even nuclei strong E0 transitions link the first excited even-spin, positive-parity band to the yrast states, none was found for the band based on the 861-keV 0 + 2 level of 240 Pu. Rather, in this case strong E0 deexcitation is associated with a rotational sequence built on the 1091-keV 0 + 3 state not observed in the present measurements.…”

supporting

confidence: 65%

Structure ofPu240: Evidence for Octupole Phonon Condensation?

et al. 2009

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The expanded level structure of 240Pu available from the present study highlights the role of strong octupole correlations in this nucleus. In addition to a delayed alignment in the yrast band, the observations include the presence of both I(+)-->(I-1)(-) and I(-)-->(I-1)(+)E1 transitions linking states of the yrast and negative-parity bands at high spin and the presence of an additional even-spin, positive-parity band deexciting exclusively to the negative-parity sequence. The observations appear to be consistent with expectations based on the recently proposed concept of octupole phonon condensation.

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“…A suppression by a factor of 5 was estimated in Ref. [30]. The present IBM calculation predicts a factor of 13.…”

supporting

confidence: 51%

“…The first excited J π = 0 + 2 (K π = 0 + 2 ) state, which is the candidate for the double-octupole 0 + state [10], is identified at an excitation energy of 861.2(1) keV, while the second excited J π = 0 + 3 state is observed at an excitation energy of 1090.3(1) keV in the present experiment. The latter was proposed to be a candidate for the β-vibrational bandhead [30]. Both spin-parity assignments…”

mentioning

confidence: 99%

Possible experimental signature of octupole correlations in the 02+states of the actinides

et al. 2013

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J π = 0 + states have been investigated in the actinide nucleus 240 Pu up to an excitation energy of 3 MeV with a high-resolution (p,t) experiment at Ep= 24 MeV. To test the recently proposed J π = 0 + 2 double-octupole structure, the phenomenological approach of the spdf-interacting boson model has been chosen. In addition, the total 0 + strength distribution and the 0 + strength fragmentation have been compared to the model predictions as well as to the previously studied (p,t) reactions in the actinides. The results suggest that the structure of the 0 + 2 states in the actinides might be more complex than the usually discussed pairing isomers. Instead, the octupole degree of freedom might contribute significantly. The signature of two close-lying 0 + states below the 2-quasiparticle energy is presented as a possible manifestation of strong octupole correlations in the structure of the 0 + 2 states in the actinides.The nature of the first excited2 ) states in the even-even actinides has been controversially discussed for decades. Extensive experimental studies had shown an asymmetry between the population in (p,t) and (t,p) reactions [1][2][3]. While large (p,t) cross sections were observed (σ 0/σ gs < 2%) were seen in the studies of Casten et al. [3]. Ragnarsson and Broglia proposed to interpret these states as pairing isomers having a smaller neutron pairing gap ∆ n than the ground state itself [4,5]. These isomers should be present in the case of an inhomogeneity of weakly coupled prolate and oblate levels around the Fermi surface for comparable monopole and quadrupole pairing strengths. The experimental signature of these pairing isomers would be large (p,t) cross sections and almost vanishing (t,p) cross sections [4]. Furthermore, Rij and Kahana predicted a negligible population of these states in single-neutron transfer reactions [5]. However, in 240 Pu a strong (d,p) population of the 0 + 2 state (σ 0 + 2 /σ gs ≈ 18%) was observed [6]. In addition to the peculiar situation of an inhomogeneous distribution of oblate and prolate single-particle orbitals around the Fermi surface, the octupole degree of freedom contributes significantly to the low-energy spectrum of the actinide nuclei [7,8]. The enhanced octupole collectivity, which has been observed in several experimental and theoretical studies, has been mainly attributed to the strong octupole interaction involving unique neutron and proton single-particle orbitals differing by ∆j = ∆l = 3. These are the j 15/2 and g 9/2 orbitals (N ∼ 134) for the neutrons, and the i 13/2 and f 7/2 orbitals (Z ∼ 88) in the case of the protons. One of the most striking signatures of * spieker@ikp.uni-koeln.de; Member of the Bonn-Cologne Gradu- ). In the even-even Pu isotopes the strongest octupole correlations have been found for 240 Pu by means of an alternating-parity band at high spins (J ∼ 20) [12]. Using two-center octupole wave functions in the framework of supersymmetric quantum mechanics, Refs. [13,14] explained the experimental data as a second-order phase tran...

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On the two first excited K = 0 bands in 238U and 240Pu

Cited by 13 publications

References 13 publications

High-resolution (p,t) study of low-spin states in Pu240 : Octupole excitations, α
Spieker
¹
,
Pascu
²
,
Bucurescu
³

et al. 2018
Phys. Rev. C
22
1
15
0
View full text Add to dashboard Cite

High-resolution (p,t) study of low-spin states in Pu240 : Octupole excitations, α
Spieker
¹
,
Pascu
²
,
Bucurescu
³

et al. 2018
Phys. Rev. C
22
1
15
0
View full text Add to dashboard Cite

Structure ofPu240: Evidence for Octupole Phonon Condensation?

Possible experimental signature of octupole correlations in the 02+states of the actinides

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On the two first excited K = 0 bands in 238U and 240Pu

Cited by 13 publications

References 13 publications

High-resolution (p,t) study of low-spin states in Pu240 : Octupole excitations, αSpieker1, Pascu2, Bucurescu3 et al. 2018Phys. Rev. C221150View full textAdd to dashboardCite

High-resolution (p,t) study of low-spin states in Pu240 : Octupole excitations, αSpieker1, Pascu2, Bucurescu3 et al. 2018Phys. Rev. C221150View full textAdd to dashboardCite

Structure ofPu240: Evidence for Octupole Phonon Condensation?

Possible experimental signature of octupole correlations in the 02+states of the actinides

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Product

Resources

About

High-resolution (p,t) study of low-spin states in Pu240 : Octupole excitations, α
Spieker
¹
,
Pascu
²
,
Bucurescu
³

et al. 2018
Phys. Rev. C
22
1
15
0
View full text Add to dashboard Cite

High-resolution (p,t) study of low-spin states in Pu240 : Octupole excitations, α
Spieker
¹
,
Pascu
²
,
Bucurescu
³

et al. 2018
Phys. Rev. C
22
1
15
0
View full text Add to dashboard Cite