| 1. |
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| 2. |
- Assie, M., et al.
(författare)
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The Giant Pairing Vibration in heavy nuclei Present status and future studies
- 2019
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Ingår i: European Physical Journal A. - : SPRINGER. - 1434-6001 .- 1434-601X. ; 55:12
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Tidskriftsartikel (refereegranskat)abstract
- The Giant Pairing Vibration, a two-nucleon collective mode originating from the second shell above the Fermi surface, has long been predicted and expected to be strongly populated in two-nucleon transfer reactions with cross sections similar to those of the low-lying Pairing Vibration. Recent experiments have provided evidence for this mode in C-14,C- 15 but, despite sensitive studies, it has not been definitively identified in Sn or Pb nuclei where pairing correlations are known to play a crucial role near their ground states. In this paper we review the basic theoretical concepts of this "elusive" state and the status of experimental searches in heavy nuclei. We discuss the hindrance effects due to Q-value mismatch and the use of weakly-bound projectiles as a way to overcome the limitations of the (p,t) reactions. We also discuss the role of the continuum and conclude with some possible future developments.
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| 3. |
- Bhagwat, Ameeya, et al.
(författare)
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Cluster decay in the superallowed alpha decay region
- 2017
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Ingår i: Physical Review C. - : AMER PHYSICAL SOC. - 2469-9985 .- 2469-9993. ; 96:3
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Tidskriftsartikel (refereegranskat)abstract
- The emissions of a particles and protons are the dominant decay channels in the neutron-deficient nuclei corresponding to the sdg major shell. The possibility of cluster emission is explored here. It is shown that the cluster decay mode has a small yet sizable branching ratio.
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| 4. |
- Bhagwat, A., et al.
(författare)
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Cluster emission from superheavy nuclei
- 2018
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Ingår i: European Physical Journal A. - : SPRINGER. - 1434-6001 .- 1434-601X. ; 54:11
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Tidskriftsartikel (refereegranskat)abstract
- The process leading to cluster emission from superheavy nuclei in the range 100 122 has been systematically investigated. This topic is of importance because it opens up the possibility of identifying superheavy elements through deposition of clusters in the detection system. In this paper we evaluate the cluster decay half lives by considering the cluster as a particle. The motion of this particle in the field induced by the daughter nucleus is determined by solving the corresponding Schrodinger equation imposing outgoing boundary conditions (Gamow state). The corresponding Wood-Saxon potential is fitted to obtain the energies provided by a mass formula that has been established recently to have a very high degree of precision. The resulting expression for the decay width is exact, i.e. no approximation besides the assumption of a preformed cluster is introduced. It is found that the heavy cluster emission probability in the superheavy region is much smaller than the corresponding a emission probability.
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| 5. |
- Bhagwat, Ameeya, et al.
(författare)
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Consistent description of the cluster-decay phenomenon in transactinide nuclei
- 2015
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Ingår i: Physical Review C. Nuclear Physics. - : American Physical Society. - 0556-2813 .- 1089-490X. ; 92:4
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Tidskriftsartikel (refereegranskat)abstract
- Systematic investigation of the known even-even transactinide cluster emitters has been carried out by considering the cluster as a point particle and using the exact quantum mechanical treatment of the decay process. It is shown that the cluster decay phenomenon can be described reasonably well using a simple Woods-Saxon mean field. Sensitivity of the half-lives on various aspects of the mean field has been investigated in detail.
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| 6. |
- Cederwall, Bo, 1964-, et al.
(författare)
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Lifetime Measurements of Excited States in Pt-172 and the Variation of Quadrupole Transition Strength with Angular Momentum
- 2018
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Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 121:2
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Tidskriftsartikel (refereegranskat)abstract
- Lifetimes of the first excited 2(+) and 4(+) states in the extremely neutron -deficient nuclide Pt-172 have been measured for the first time using the recoil-distance Doppler shift and recoil-decay tagging techniques. An unusually low value of the ratio B(E2: 4(1)(+) -> 2(1)(+)/B(E2: 2(1)(+) -> 0(gs)(+)) = 0.55(19) was found, similar to a handful of other such anomalous cases observed in the entire Segre chart. The observation adds to a cluster of a few extremely neutron -deficient nuclides of the heavy transition metals with neutron numbers N approximate to 90-94 featuring the effect. No theoretical model calculations reported to date have been able to explain the anomalously low B(E2: 4(1)(+) -> 2(1)(+)/B(E2: 2(1)(+) -> 0(gs)(+)) ratios observed in these cases. Such low values cannot, e.g., be explained within the framework of the geometrical collective model or by algebraic approaches within the interacting boson model framework. It is proposed that the group of B(E2: 4(1)(+) -> 2(1)(+)/B(E2: 2(1)(+) -> 0(gs)(+)) ratios in the extremely neutron-deficient even-even W, Os, and Pt nuclei around neutron numbers N approximate to 90-94 reveal a quantum phase transition from a seniority-conserving structure to a collective regime as a function of neutron number. Although a system governed by seniority symmetry is the only theoretical framework for which such an effect may naturally occur, the phenomenon is highly unexpected for these nuclei that are not situated near closed shells.
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| 7. |
- Delion, D. S., et al.
(författare)
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A simple approach to alpha-decay fine structure
- 2016
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Ingår i: Journal of Physics G. - : Institute of Physics Publishing (IOPP). - 0954-3899 .- 1361-6471. ; 43:9
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Tidskriftsartikel (refereegranskat)abstract
- We propose a simple method to evaluate alpha-transition rates to low-lying excited states in even-even nuclei. For this a realistic alpha-daughter doublefolding interaction is approximated by a parabola in the region where the decay process takes place. This allows us to evaluate the penetration probability analytically. The main experimental features of branching ratios to excited states are reproduced by this simple approach.
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| 8. |
- Delion, D. S., et al.
(författare)
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Exact estimate of the alpha-decay rate and semiclassical approach in deformed nuclei
- 2015
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Ingår i: Physical Review C. Nuclear Physics. - : American Physical Society. - 0556-2813 .- 1089-490X. ; 92:5
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Tidskriftsartikel (refereegranskat)abstract
- We compare the quantum mechanical procedures to estimate the total alpha-decay width from deformed nuclei in the laboratory and intrinsic systems of coordinates. Our analysis shows that the total half-life estimated in the intrinsic frame by neglecting the rotational motion of the core (adiabatic approach) is one order of magnitude smaller at beta(2) = 0.3 than the corresponding value in the spherical case. A similar calculation in the laboratory system of coordinates by considering the core motion (giving the correct theoretical estimate) predicts a reduction by only a factor of 2. The widely used "angular WKB" (Wentzel-Kramers-Brillouin) semiclassical procedure provides decay widths which are comparable to the adiabatic approach. We propose a new and very simple semiclassical "angular momentum WKB" procedure to evaluate the decay width in deformed nuclei. It provides decay widths very close to the ones obtained by the exact laboratory coupling channels procedure.
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| 9. |
- Patial, Monika, et al.
(författare)
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Microscopic description of superallowed alpha-decay transitions
- 2016
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Ingår i: PHYSICAL REVIEW C. - : American Physical Society. - 2469-9985. ; 93:5
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Tidskriftsartikel (refereegranskat)abstract
- It was recently found that the formation probabilities of alpha particles in Te isotopes are larger than the corresponding probabilities in Po isotopes. We have done a full microscopic calculation within the framework of the multistep shell model to analyze in detail the formation probabilities and subsequent decays of alpha particles from Po-212 and Te-104. We have also calculated the spectra of these two decaying nuclei and found that the tentatively assigned spin (18(+)) at 2.922 MeV in Po-212 (National Nuclear Data Center, www.nndc.bnl.gov) is predicted to be a state 16(+). We also present for the first time the full energy spectrum of Te-104. The evaluated formation amplitudes in both nuclei show that in Te-104 there is indeed a superallowed alpha-decay transition.
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| 10. |
- Qi, Chong, 1983-, et al.
(författare)
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Recent developments in radioactive charged-particle emissions and related phenomena
- 2019
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Ingår i: Progress in Particle and Nuclear Physics. - : Elsevier. - 0146-6410 .- 1873-2224. ; 105, s. 214-251
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Forskningsöversikt (refereegranskat)abstract
- The advent and intensive use of new detector technologies as well as radioactive ion beam facilities have opened up possibilities to investigate alpha, proton and cluster decays of highly unstable nuclei. This article provides a review of the current status of our understanding of clustering and the corresponding radioactive particle decay process in atomic nuclei. We put alpha decay in the context of charged-particle emissions which also include one- and two-proton emissions as well as heavy cluster decay. The experimental as well as the theoretical advances achieved recently in these fields are presented. Emphasis is given to the recent discoveries of charged-particle decays from proton-rich nuclei around the proton drip line. Those decay measurements have shown to provide an important probe for studying the structure of the nuclei involved. Developments on the theoretical side in nuclear many-body theories and supercomputing facilities have also made substantial progress, enabling one to study the nuclear clusterization and decays within a microscopic and consistent framework. We report on properties induced by the nuclear interaction acting in the nuclear medium, like the pairing interaction, which have been uncovered by studying the microscopic structure of clusters. The competition between cluster formations as compared to the corresponding alpha-particle formation are included. In the review we also describe the search for super-heavy nuclei connected by chains of alpha and other radioactive particle decays.
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