High-spin states and<i>K</i>-forbidden decay in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi mathvariant="normal">Hf</mml:mi></mml:mrow><mml:mprescripts /><mml:mrow /><mml:mrow><mml:mn>172</mml:mn></mml:mrow><mml:mrow /><mml:mrow /></mml:mmultiscripts></mml:mrow></mml:math>

Cullen, D. M.; Baktash, C.; Fitch, Michael J.; {Frosch}, I; Gray, Robert W.; Johnson, N.R.; Lee, I. Y.; Macchiavelli, A. O.; Reviol, W.; Wang, X.-H.; Yu, C. H.

doi:10.1103/physrevc.52.2415

Cited by 17 publications

(6 citation statements)

References 15 publications

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“…The measured hindrance factor F exp for the 1879-keV E2 transition from the K = 12 isomeric bandhead to the 10 + state of ground state band is 7.3 × 10 5 , three orders of magnitude higher than the calculated value F calc of 2.6 × 10 2 . For the same bandhead configuration in 172 Hf, F calc = 1.0 × 10 5 , which compares well with F exp = 2.1 × 10 5 , using a 1-ns measured upper limit for the state half-life [30]. To highlight the discrepancy, measured versus calculated hindrance factors from I = 2 decays from a selected subset of 4-qp isomers are shown in Fig.…”

Section: Decay Mechanisms Of Multi-qp K Isomerssupporting

confidence: 57%

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High-Kisomers and rotational structures inW174

et al. 2006

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High-spin states in 174 W (Z = 74) have been populated using the reaction 128 Te( 50 Ti, 4n) 174 W at beam energies of 215 and 225 MeV. The Gammasphere array was used to detect the γ rays emitted by the evaporation residues. Four previously known collective band structures have been extended, and 16 new rotational sequences observed. Two are built upon isomeric states, one corresponding to a two-quasiparticle K = 8 isomer, the other to a four-quasiparticle K = 12 isomer, with the latter exhibiting strong K-violating K = 12 decays to the ground state band. Nucleonic configurations for the two-and four-quasiparticle excitations are proposed, and Woods-Saxon cranking calculations are presented to understand the rotational structures. Decay mechanisms of multi-quasiparticle K isomers are discussed in terms of the prevalent phenomenological models, with special emphasis on γ -tunneling calculations. Surprisingly, the latter underpredict the decay hindrance for the K = 12 isomer by three orders of magnitude, unlike all other isomer decays in this mass region.

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Section: Decay Mechanisms Of Multi-qp K Isomerssupporting

confidence: 57%

“…A band somewhat similar in its decay properties to band 9 is observed in the neighboring even-even isotone 172 Hf, labeled band 5 in Ref. [30]. In both cases, out-of-band transitions to the yrast band are observed over an extended region of spin.…”

Section: Bands 9 To 13mentioning

confidence: 62%

High-Kisomers and rotational structures inW174

et al. 2006

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“…A later experiment studied this mediating state in more detail [23] and described a mechanism by which significant mixing in the wavefunction between high-and low-K components played the important role. Other K-mixed states at energies from 2 -3 MeV were found in nearby isotopes [23,24] to facilitate some isomer decays, leading to halflives that were much shorter than expected. The key point is that these isomers lay above the mediating states and could therefore decay through them spontaneously.…”

Section: Development Of Systematicsmentioning

confidence: 82%

An experimental perspective on triggered gamma emission from nuclear isomers

Carroll

2004

Laser Phys. Lett.

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The study of triggered depopulation of nuclear isomers, with accompanying gamma emission, is a rapidlychanging field that is only now attaining some degree of maturity. Because isomer decays via electromagnetic transitions are strongly inhibited, the interaction of these levels with externallyproduced photons provides an important probe of nuclear structure. Also, since some isomers may store large amounts of energy for long times, a number of applications have been proposed, including the creation of a gamma-ray laser. Early experiments conclusively demonstrated triggering of the 10 15 -year isomer of 180 Ta, but even a partial correlation of the effect with known levels could only be obtained recently. Investigations of triggering for the 31-year isomer of 178 Hf were initially guided just by systematics and experiments are characterized by considerable controversy. Against this background, the field of triggered gamma emission is entering a new phase in which improved level data allow targeting of specific potentially-useful transitions. This paper summarizes the current state-of-the-art and discusses the changing nature of the field.

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“…The problem of the decay of K isomers and the associated K selection rule and its violation in deformed nuclei have been subjects of much discussion. Many cases of K violating gamma-ray transitions are known experimentally [1][2][3][4][5][6]. No consistent explanation is available for the finite but retarded transitions from K isomers to lower K bands seen experimentally.…”

Section: Introductionmentioning

confidence: 99%

“…No consistent explanation is available for the finite but retarded transitions from K isomers to lower K bands seen experimentally. The rotational model forbids such transitions (the Kselection rule) [7,8] and in many discussions various ad hoc assumptions are made to explain the violation of K selection rule [4]. But a proper quantitative understanding of the mechanism of the K-selection rule violation in the framework of nucleon-nucleon residual interaction is still lacking.…”

Section: Introductionmentioning

confidence: 99%

Microscopic study of K-Selection Rule Violation in $^{182}$W K=10$^+$ Isomer Decay

Praharaj,

Bhoi,

Naik

et al. 2019

Preprint

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In this paper we study the microscopic mechanism for the retarded decay of K-isomers to lower K bands. We do angular momentum projection from suitable intrinsic states. The retardation arises from poor overlap between the low K and high K bands in the integral over Euler angles. Deformed HF and angular momentum projection calculations are done for the decay of the K = 10 + isomer band to the ground band of 182 W . K-mixing is unimportant and the K quantum numbers of the bands are quite good. There is significant difference in the reduced matrix elements of transition operators in our formalism and that in the rotational model. Angular momentum projection gives J-selection rule but there is no K selection rule for reduced matrix elements of electromagnetic multipole operators. Thus, E2 and M1 transitions from the K isomer to the ground band of 182 W are finite but retarded in angular momentum projection theory, as in experiments. This provides a theoretical basis for the study of K-isomers and their decay modes. Quantitative results are presented. The microscopic model gives J-selection rule and angular momentum conservation for combined matter and radiation systems.

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High-spin states andK-forbidden decay inHf172

Cited by 17 publications

References 15 publications

High-Kisomers and rotational structures inW174

High-Kisomers and rotational structures inW174

An experimental perspective on triggered gamma emission from nuclear isomers

Microscopic study of K-Selection Rule Violation in $^{182}$W K=10$^+$ Isomer Decay

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