Alternating parity bands and octupole effects in 221Th and 223Th★

Dahlinger, M.; Kankeleit, E.; Habs, D.; Schwalm, D.; Schwartz, B.; Simon, R. S.; Burrows, J D; Butler, P. A.

doi:10.1016/0375-9474(88)90076-0

Cited by 88 publications

(68 citation statements)

References 36 publications

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“…3 are relevant for the modification of the yrast sequence at medium spin with respect to Ref. [12], and for its extension towards the highest spins observed. Here, the gating transitions are chosen to be those of E1 character, which compete favorably for strength with the bypassing E2 γ rays.…”

Section: Yrast Octupole Sequence: Inmentioning

confidence: 67%

“…In the light actinide nuclei, parity-doublet sequences are reported for 219 Th [6], 223 Th [12], 225 Th [13], and for some of the corresponding Ra isotones such as 221 Ra [14], and these band structures are all consistent with a K ≥ 3/2 assignment. Parity-doublet sequences are notably absent in 221 Th [12] and 219 Ra [15]. These nuclei have yrast sequences that are assigned K = 1/2 [16].…”

Section: Introductionmentioning

confidence: 83%

“…The latter transition has been misplaced in the level scheme of Ref. [12]: it cannot be placed in the yrast sequence. The spectrum gated by the 486-keV transition [ Fig.…”

Section: Yrast Octupole Sequence: Inmentioning

confidence: 99%

“…Studies of 221 Th and other light Th nuclei with spectroscopic methods have traditionally been performed with an additional "filter" device, in order to separate the γ rays emitted by the evaporation-residue (ER) nuclei from those of the dominant fission products and from other sources of background [12]. This approach has been chosen in the present study as well.…”

Section: Introductionmentioning

confidence: 99%

“…The yrast octupole sequence has been modified, as compared to Ref. [12], and has been extended up to spin-parity 39/2 + and 37/2 − . Here, the alternating-parity structure appears to be cut off, but an additional transition is present.…”

Section: Introductionmentioning

confidence: 99%

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Characterization of octupole-type structures inTh221

et al. 2014

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A detailed level scheme for 221 Th has been established in an experiment using the 18 O + 207 Pb reaction at 96 MeV. The evaporation residues from this fissile system were selected with the HERCULES detector array and residue-gated γ rays were measured with Gammasphere. Three band structures of interlinked, alternating-parity levels are observed, two of which are non-yrast. In addition, several high-lying excitations are found. The yrast band is seen up to spin-parity 37/2 − and 39/2 + , beyond which a high-spin feeding transition is observed. The non-yrast sequences are interpreted as parity-doublet structures, based on a configuration similar to that of the yrast band in 223 Th (K = 5/2). The key properties of even-odd nuclei in this mass region [B(E1)/B(E2) and B(M 1)/B(E2) ratios, spin alignments, parity splittings] are reviewed.

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Section: Yrast Octupole Sequence: Inmentioning

confidence: 67%

Section: Introductionmentioning

confidence: 83%

“…The latter transition has been misplaced in the level scheme of Ref. [12]: it cannot be placed in the yrast sequence. The spectrum gated by the 486-keV transition [ Fig.…”

Section: Yrast Octupole Sequence: Inmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Characterization of octupole-type structures inTh221

et al. 2014

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Panoramic New Vistas of Nuclei in and Near Their Ground States

Hamilton

1992

Nuclear Shapes and Nuclear Structure at Low Excitation Energies

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Reflection-Asymmetric Shapes in Nuclei

Ahmad¹,

Carpenter²,

Emling

et al. 1990

Exotic Nuclear Spectroscopy

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Soon after the collective nuclear model [1,2] was established, low-lying negative parity states were observed [3] in even-even Ra and Th nuclei from alpha-particle spectroscopic studies. These negative parity levels formed a rotational band with spin sequence 1, 3, 5, and K quantum number 0. Since these states had energies much lower than the expected two quasi-particle states, these were interpreted as octupole vibrations about a spheroidal equilibrium shape. Ever since the discovery of the octupole vibrations, scientists have been thinking about the possibility of octupole deformations in nuclei, that is, nuclei with octupole equilibrium shape. These octupole shapes are symmetric about the Z axis but reflection asymmetric about the XY plane and resemble a Pear.• --. w i : , . £ ,,,.,.. -, ' ; ,.,,_• , T he submitted manutcnpt has been authored bv a contractor of the U. S. Government under contract Na. W-31-109-ENG-3S. Accordingly, the U. S. Government retains a nonexclusive, royalty-free license \n publish or reproduce the published form of this contribution, or allow others to do so, for IK S. Government purposes. MASTERThe octupole deformation or octupole vibration is produced by the long range octupole-octupole correlations. These correlations depend on the r 3 Y3*r^Y3 matrix elements between single particle states with A2. = Aj -3 and the energy difference between them. A look at the shell states ( Fig. 1 with the binding energy of ~10 MeV due to the quadrupole deformation (Fig. 2).It is well known that the rotation of symmetric and asymmetric molecules generate different rotational bands. In the case of the former, the band has 0 + , 2 + , 4 + --level sequence and the latter has 0 + , 1", 2 + , 3", --sequence.Thus the rotation of reflection symmetric and reflection asymmetric nuclei will produce different spectra and these can be used as signature of octupole shape. OCTUPOLE DEFORMATION THE ACTINIDE REGIONIn odd mass nuclei, the two members of the parity doublet have very similar wave functions except the parity. Thus one would expect similar properties for both bands. The data on odd mass nuclei in the mass 224 region can be summarized as follows:1. Parity doublets have been observed in several odd-mass Ra, Ac and Pa nuclei [12][13][14][15]. An example [14] is shown in Fig. 4. The members of the doublets are connected by fast El transitions [15].The B(E1) values in these nuclei are larger than l.OxlO" 3 Weisskopf units (see Fig. 5).3. Alpha decay rates are enhanced to the parity doublet partner of the favored band.4. Coriolis matrix elements and Ml transition rates are attenuated.5. Octupole deformation has also been found at moderate spins [16] in 221 Th and 223 Th.In even-even nuclei, levels with alternating parity have been observed in several Ra and Th nuclei. In general, these are connected by fast El transitions. OCTUPOLE DEFORMATION IN N-88, Z-56 NUCLEIAs shown in Fig. 1, octupole correlations are also expected in the Z~56, N~8Snuclei. However, in these nuclei, spacings for the A2. = 3, Aj =3 le...

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Alternating parity bands and octupole effects in 221Th and 223Th★

Cited by 88 publications

References 36 publications

Characterization of octupole-type structures inTh221

Characterization of octupole-type structures inTh221

Panoramic New Vistas of Nuclei in and Near Their Ground States

Reflection-Asymmetric Shapes in Nuclei

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