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Liotta, Roberto
Publications (6 of 6) Show all publications
Qi, C., Liotta, R. & Wyss, R. A. (2019). Recent developments in radioactive charged-particle emissions and related phenomena. Progress in Particle and Nuclear Physics, 105, 214-251
Open this publication in new window or tab >>Recent developments in radioactive charged-particle emissions and related phenomena
2019 (English)In: Progress in Particle and Nuclear Physics, ISSN 0146-6410, E-ISSN 1873-2224, Vol. 105, p. 214-251Article, review/survey (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Alpha decay, Charged-particle emission, Formation probability, Nuclear structure, Pairing
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-246494 (URN)10.1016/j.ppnp.2018.11.003 (DOI)000461538400006 ()2-s2.0-85058194997 (Scopus ID)
Note

QC 20190320

Available from: 2019-03-20 Created: 2019-03-20 Last updated: 2019-04-05Bibliographically approved
Assie, M., Dasso, C. H., Liotta, R., Macchiavelli, A. O. & Vitturi, A. (2019). The Giant Pairing Vibration in heavy nuclei Present status and future studies. European Physical Journal A, 55(12), Article ID 245.
Open this publication in new window or tab >>The Giant Pairing Vibration in heavy nuclei Present status and future studies
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2019 (English)In: European Physical Journal A, ISSN 1434-6001, E-ISSN 1434-601X, Vol. 55, no 12, article id 245Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
SPRINGER, 2019
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-266281 (URN)10.1140/epja/i2019-12829-8 (DOI)000500788700002 ()2-s2.0-85075910852 (Scopus ID)
Note

QC 20200108

Available from: 2020-01-08 Created: 2020-01-08 Last updated: 2020-01-08Bibliographically approved
Bhagwat, A. & Liotta, R. (2018). Cluster emission from superheavy nuclei. European Physical Journal A, 54(11), Article ID 200.
Open this publication in new window or tab >>Cluster emission from superheavy nuclei
2018 (English)In: European Physical Journal A, ISSN 1434-6001, E-ISSN 1434-601X, Vol. 54, no 11, article id 200Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
SPRINGER, 2018
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-239991 (URN)10.1140/epja/i2018-12628-9 (DOI)000451191100001 ()2-s2.0-85073994118 (Scopus ID)
Note

QC 20181211

Available from: 2018-12-11 Created: 2018-12-11 Last updated: 2020-03-09Bibliographically approved
Cederwall, B., Doncel, M., Aktas, Ö., Ertoprak, A., Liotta, R., Qi, C., . . . Valiente-Dobon, J. J. (2018). Lifetime Measurements of Excited States in Pt-172 and the Variation of Quadrupole Transition Strength with Angular Momentum. Physical Review Letters, 121(2), Article ID 022502.
Open this publication in new window or tab >>Lifetime Measurements of Excited States in Pt-172 and the Variation of Quadrupole Transition Strength with Angular Momentum
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2018 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 121, no 2, article id 022502Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
American Physical Society, 2018
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-232610 (URN)10.1103/PhysRevLett.121.022502 (DOI)000438041900004 ()30085703 (PubMedID)2-s2.0-85049933566 (Scopus ID)
Funder
Swedish Research Council, 621-2014-5558 621-2014-5558EU, FP7, Seventh Framework Programme, 262010 ENSAR
Note

QC 20180801

Available from: 2018-08-01 Created: 2018-08-01 Last updated: 2020-03-09Bibliographically approved
Bhagwat, A. & Liotta, R. (2017). Cluster decay in the superallowed alpha decay region. Physical Review C: Covering Nuclear Physics, 96(3), Article ID 031302.
Open this publication in new window or tab >>Cluster decay in the superallowed alpha decay region
2017 (English)In: Physical Review C: Covering Nuclear Physics, ISSN 2469-9985, E-ISSN 2469-9993, Vol. 96, no 3, article id 031302Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2017
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-215450 (URN)10.1103/PhysRevC.96.031302 (DOI)000411079600001 ()2-s2.0-85029894954 (Scopus ID)
Note

QC 20171019

Available from: 2017-10-19 Created: 2017-10-19 Last updated: 2017-11-29Bibliographically approved
Liotta, R. (2010). MULTISTEP SHELL MODEL METHOD IN THE COMPLEX ENERGY PLANE. In: Bai, HB Meng, J Zhao, EG Zhou, SG (Ed.), NUCLEAR STRUCTURE IN CHINA 2010: . Paper presented at 13th National Conference on Nuclear in China; Chi Feng Univ, Chi Feng, PEOPLES R CHINA; JUL 24-30, 2010 (pp. 88-95). WORLD SCIENTIFIC PUBL CO PTE LTD
Open this publication in new window or tab >>MULTISTEP SHELL MODEL METHOD IN THE COMPLEX ENERGY PLANE
2010 (English)In: NUCLEAR STRUCTURE IN CHINA 2010 / [ed] Bai, HB Meng, J Zhao, EG Zhou, SG, WORLD SCIENTIFIC PUBL CO PTE LTD , 2010, p. 88-95Conference paper, Published paper (Refereed)
Abstract [en]

We have adopted the multistep shell model in the complex energy plane to study excitations occurring in the continuum part of the nuclear spectrum. In this method of solving the shell model equations one proceeds in several steps. In each step one constructs building blocks to be used in future steps. We applied this formalism to analyze the unbound nucleus Li-12. In this case the excitations correspond to the motion of three particles partitioned as the product of a one-particle and two-particle systems.

Place, publisher, year, edition, pages
WORLD SCIENTIFIC PUBL CO PTE LTD, 2010
Keywords
Shell mode, continuum, drip line, complex energy plane
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-271106 (URN)000394395400015 ()
Conference
13th National Conference on Nuclear in China; Chi Feng Univ, Chi Feng, PEOPLES R CHINA; JUL 24-30, 2010
Note

QC 20200317

Available from: 2020-03-17 Created: 2020-03-17 Last updated: 2020-03-17Bibliographically approved
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