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110 results on '"Mertzimekis, Theo J."'

1. Revisiting the nuclear magnetic octupole moment

Author

Bofos, Stavros and Mertzimekis, Theo J.

Subjects
Nuclear Theory, Nuclear Experiment
Abstract

The nuclear magnetic octupole moment is revisited as a potentially useful observable for nuclear structure studies. The magnetic octupole moment, $\Omega$, is examined in terms of the nuclear collective model including weak and strong coupling. Single-particle formulation is additionally considered in the overall comparison of theoretical predictions with available experimental data. Mirror nuclei symmetry is examined in terms of the magnetic octupole moment isoscalar and isovector terms. A full list of predictions for $\Omega$ of odd-proton and odd-neutron nuclei in medium-heavy mass regimes of the nuclear chart is produced aiming at providing starting values for future experimental endeavors., Comment: Accepted for publication in Atomic Data Nuclear Data Tables (27 pages, 2 figures, 5 tables)

Published
2024

2. Mean-field derived IBM-1 Hamiltonian with intrinsic triaxial deformation

Author

Vasileiou, Polytimos, Bonatsos, Dennis, and Mertzimekis, Theo J.

Subjects
Nuclear Theory
Abstract

An interacting-boson-model-1 (IBM-1) Hamiltonian, derived from self-consistent mean-field calculations using a Skyrme energy density functional is employed for the study of energy spectra and $B(E2)$ transition strengths in the even-even $^{162-184}\mathrm{Hf}$ and $^{168-186}\mathrm{W}$. An intrinsic triaxial deformation, derived from fermionic proxy-SU(3) irreps, is incorporated into the IBM-1 potential energy curve, which is subsequently mapped to the fermionic one, in order to derive the parameters of the IBM-1 Hamiltonian. It is shown that the inclusion of the intrinsic triaxial deformation derived from the proxy-SU(3) irreps leads to a significantly improved agreement between the theoretical predictions and experimental data for the low-lying quadrupole bands in the examined isotopes, without the need of higher-order terms in the IBM-1 Hamiltonian. The calculated $B(E2)$ transition strengths are also improved, compared to the axially symmetric case. The recently suggested preponderance of triaxial deformation over extended regions of the nuclear chart is obtained as a by-product. Future potential improvements and extensions to this mapping approach are also discussed., Comment: 20 pages, 9 figures. Accepted for publication to Phys. Rev. C

Published
2024

3. Isomeric Lifetime Measurement in the Neutron-rich 189Ta

Author

Alhomaidhi Sultan, Sahin Elif, Werner Volker, Jolie Jan, Regan Patrick, Pietralla Norbert, Gerl Jürgen, Górska Magdalena, Benzoni Giovanna, Mistry Andrew K., Hubbard Nicolas, Aggez Guler, Albers Helena M., Arici Tugba, Armstrong Michael, Banerjee Akashrup, Das Biswarup, Davinson Thomas, Hall Oscar, Kojouharov Ivan, Koseoglou Pavlos, Mikolajczuk Michal, Podolyák Zsolt, Polettini Marta, Rudigier Matthias, Schaffner Henning, Wollersheim Hans-Jürgen, Yaneva Aleksandrina, Boutachkov Plamen, Dickel Timo, Haettner Emma, Heggen Henning, Hornung Christine, Knöbel Ronja, Kostyleva Daria, Kurz Nikolaus, Kuzminchuk Natalia, Mukha Ivan, Pietri Stephane, Plaß Wolfgang, Scheidenberger Christoph, Tanaka Yoshiki, Weick Helmut, Ahmed Usama, Aktas Özge, Algora Alejandro, Appleton Corrigan, Blazhev Andrey, Bruce Alison, Cederwall Bo, Chishti Muhammad M. R., Cortes Martha L., Crespi Fabio, Dobon Jose J., Doncel Maria, Ertoprak Aysegül, Esmaylzadeh Arwin, Expósito Marcos L., Fraile Luis M., García Jaime B., Gottardo Andrea, Ha Jeongsu, Jazrawi Shaheen, John Philipp R., Jones Calum, Karayonchev Vasil, Kern Ralph, Knafla Lukas, Kosir Gregor, Lozeva Radomira, Mengoni Daniele, Mertzimekis Theo J., Million Bénédicte, Morales Anabel, Murias Javier R., Orrigo Sonja E. A., Pellumaj Julgen, Pelonis Stefanos, Petrović Jana, Pigliapoco Sara, Quintana Begoña, Recchia Francesco, Rezynkina Kseniia, Sexton Lewis, Singh Nara, Söderström Pär-Anders, Sood Arshiya, Vasileiou Polytimos, Vesic Jelena, Wiederhold Johannes, zhang guangxin, Zidarova Radostina, and Zyriliou Aikaterini

Subjects
Physics, QC1-999
Abstract

Isomeric states of the neutron-rich isotope 18973Ta116 were populated via fragmentation of a primary beam of 208Pb ions at 1 GeV/u impinging on a 9Be target at GSI, Darmstadt, Germany. The isotopes of interest were separated, identified and delivered to the DESPEC setup. Two isomers were deduced in 189Ta116 and their lifetimes were measured based on the γ-ray time distributions.

Published
2023
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5. Radiative proton–capture reactions with 112,114Cd at astrophysically important energies

Author

Vasileiou Polytimos, Mertzimekis Theo J., Chalil Achment, Fakiola Christina, Karakasis Ioannis, Kotsovolou Anastasia, Pelonis Stefanos, and Zyriliou Aikaterini

Subjects
Physics, QC1-999
Abstract

The reaction network in the neutron-deficient part of the nuclear chart around A ≈ 100 contains several nuclei of importance to astrophysical processes, such as the p–process. This work reports on the results from recent experimental studies of the radiative proton–capture reactions 112,114Cd(p, γ)113,115 In. Experimental cross sections for the reactions have been measured for proton beam energies residing inside the respective Gamow windows for each reaction, using isotopically enriched 112Cd and 114Cd targets. Two different techniques, the in–beam γ–ray spectroscopy and the activation method have been implemented, where the latter is considered mandatory to account for the presence of low–lying isomers in 113In (E ≈ 392 keV, t1/2 ≈ 100 min), and 115In (E ≈ 336 keV, t1/2 ≈ 4.5 h). Following the measurement of the cross sections, the astrophysical S factors have been subsequently

Published
2022
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10. Experimental Study of the Nuclear Structure of 180Hf: Preliminary results

Author

Vasileiou, Polytimos, primary, Mertzimekis, Theo J., additional, Chalil, Achment, additional, Zyriliou, Aikaterini, additional, Pelonis, Stefanos, additional, Lagaki, Varvara, additional, Siltzovalis, Georgios, additional, Efstathiou, Margarita, additional, Koseoglu, Pavlos, additional, Bonatsos, Dennis, additional, Martinou, Andriana, additional, Minkov, Nikolay, additional, Marginean, Nicolae, additional, Mihai, Constantin, additional, Florea, Nicoleta, additional, Ujeniuc, Sorin, additional, Tuturica, Andrei, additional, Costache, Cristian, additional, Mihai, Radu, additional, Stan, Lucian, additional, Filipescu, Dan, additional, Toma, Sebastian, additional, Gheorghe, Ioana, additional, Dinescu, Irina, additional, Ionescu, Alina, additional, Stoica, Liviu, additional, Calinescu, Stefana, additional, Oprea, Andreea, additional, Stoica, Alexandru, additional, Sotty, Christophe, additional, Clisu, Cristina, additional, Nita, Cristina, additional, and Neascu, Catalin, additional

Published
2022
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11. Nuclear Structure Investigations in Yb isotopes

Author

Zyriliou, Aikaterini, primary, Mertzimekis, Theo J., additional, Chalil, Achment, additional, Vasileiou, Polytimos, additional, Pelonis, Stefanos, additional, Efstathiou, Margarita, additional, Stan, Lucian, additional, Turturica, Andrei, additional, Costache, Cristian, additional, Mihai, Radu, additional, Borcea, Ruxandra, additional, Ujeniuc, Sorin, additional, Toma, Sebastian, additional, Clisu, Cristina, additional, Oprea, Andreea, additional, Ionescu, Alina, additional, Gheorghe, Ioana, additional, Boromiza, Marian, additional, Mihai, Constantin, additional, Sotty, Christophe, additional, Nita, Christina, additional, Marginean, Nicolae, additional, Marginean, Raluca, additional, Florea, Nicoleta, additional, Dinescu, Irina, additional, Bucurescu, Dorel, additional, Filipescu, Dan, additional, Lica, Razvan, additional, Stroe, Lucian, additional, and Suvaila, Rares, additional

Published
2022
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13. A study of the nuclear structure in even–even Hf isotopes

Author

Vasileiou, Polytimos, Mertzimekis, Theo J., Zyriliou, Aikaterini, Mavrommatis, Eirini, Bonatsos, Dennis, Karakatsanis, K. E., Martinou, Andriana, Peroulis, Spyros, Chalil, A., Marginean, Nicu, Mihai, C., Florea, Nicoleta, Nita, Christina, and Turturica, Andrej

Abstract

Poster presented in Euroschool on Exotic Beams - La Rábida 2022, 11-17 September 2022, La Rábida, Spain

Published
2022
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14. Gamma spectroscopy of even even Ytterbium isotopes.pdf

Author

Efstathiou, Margarita, Karadimas, Angelos, Zyriliou, Aikaterini, Vasileiou, Polytimos, Mertzimekis, Theo J., Khaliel, Ahmed, Pelonis, Stefanos, Stan, Lucian, Turturica, Andrei, Costache, Christian, Radu, Mihai, Borcea, Ruxandra, Ujeniuc, Sorin, Toma, Sebastian, Clisu, Christina, Oprea, Andreea, Ionescu, Alina, Gheorghe, Ioana, Boromizav, M., Mihai, Constantin, Nita, Cristina, Marginean, Nicolae, Marginean, R., Florea, N., Dinescu, Irina, Bucurescu, D., Filipescu, Dan, Lica, R., Stroe, L., and Suvaila, R.

Abstract

30th Symposium of the Hellenic Nuclear Physics Society (HNPS-2022), 7-8 October 2022, Ioannina, Greece

Published
2022
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15. Nuclear structure investigations of even–even Hf isotopes

Author

Vasileiou, Polytimos, Mertzimekis, Theo J., Zyriliou, Aikaterini, Mavrommatis, Eirini, Pelonis, Stefanos, Karakatsanis, K. E., Martinou, Andriana, Peroulis, Spyros, Chalil, A., Marginean, Nicu, Mihai, C., Florea, Nicoleta, Nita, Cristina, and Turturica, Andrej

Abstract

Poster presented in Shapes and Symmetries in Nuclei : From Experiment to Theory 2022 (SSNET’22), 30 May - 3 June 2022, Orsay, France

Published
2022
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17. Nuclear structure study of even-even Yb isotopes

Author

Zyriliou, Aikaterini, Mertzimekis, Theo J., Chalil, A., Vasileiou, Polytimos, Mavrommatis, Eirini, Bonatsos, Dennis, Martinou, Andriana, Peroulis, Spyros, and Nikolay, Minkov

Abstract

Poster in Euroschool on Exotic Beams 2021, 11-17 September 2021, KU Leuven, Belgium

Published
2022
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19. A study of the nuclear structure in the even-even Yb isotopes

Author

Zyriliou, Aikaterini, primary, Mertzimekis, Theo J., additional, Chalil, Achment, additional, Vasileiou, Polytimos, additional, Mavrommatis, Eirini, additional, Bonatsos, Dennis, additional, Martinou, Andriana, additional, Peroulis, Spyros, additional, and Minkov, Nikolay, additional

Published
2022
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21. A new online database of nuclear electromagnetic moments

Author

Mertzimekis Theo J.

Subjects
Physics, QC1-999
Abstract

Nuclear electromagnetic (EM) moments, i.e., the magnetic dipole and the electric quadrupole moments, provide important information of nuclear structure. As in other types of experimental data available to the community, measurements of nuclear EM moments have been organized systematically in compilations since the dawn of nuclear science. However, the wealth of recent moments measurements with radioactive beams, as well as earlier existing measurements, lack an online, easy-to-access, systematically organized presence to disseminate information to researchers. In addition, available printed compilations suffer a rather long life cycle, being left behind experimental measurements published in journals or elsewhere. A new, online database (http://magneticmoments.info) focusing on nuclear EM moments has been recently developed to disseminate experimental data to the community. The database includes non–evaluated experimental data of nuclear EM moments, giving strong emphasis on frequent updates (life cycle is 3 months) and direct connection to the sources via DOI and NSR hyperlinks. It has been recently integrated in IAEA LiveChart [1], but can also be found as a standalone webapp [2]. A detailed review of the database features, as well as plans for further development and expansion in the near future is discussed.

Published
2017
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22. Nuclear structure and decay data evaluation in Europe

Author

Negret Alexandru, Balabanski Dimiter, Dimitriou Paraskevi, Elekes Zoltan, Mertzimekis Theo J., Pascu Sorin, and Timar Janos

Subjects
Physics, QC1-999
Abstract

Nuclear Structure and Decay Data (NSDD) activities in Europe include mass-chain and individual nuclei evaluations as well as horizontal evaluations and compilations, data dissemination and educational activities. As such they are essential for a large range of applications from energy, environmental, and medical to basic research in nuclear structure and reactions, all of which are intensively pursued in Europe. Although the NSDD evaluation groups in Europe form part of the international network of NSDD evaluators, which is coordinated by the International Atomic Energy Agency, they are faced with some very distinct challenges. We shortly present the NSDD Data Centre at IFIN-HH, Bucharest and discuss possible actions to improve the situation for the entire European NSDD evaluation effort.

Published
2017
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24. Spectroscopic studies in $^{152-154}$Gd

Author

Pelonis, Stefanos, Mertzimekis, Theo J., Khaliel, Ahmed, Crespi, Fabio C.L., Bracco, Angela, Zagoraios, Georgios, Papaioannou, Dimitrios, Florea, Nicoleta, Marginean, Nicu, Stan, Lucian, and Turturica, Andrej

Subjects
ComputingMethodologies_GENERAL
Abstract

Poster presented at ANPC2021

Published
2021
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25. The Hydrothermal Vent Field at the Eastern Edge of the Hellenic Volcanic Arc: The Avyssos Caldera (Nisyros)

Author

Dura, Ana Mertzimekis, Theo J. Nomikou, Paraskevi Gondikas, Andreas Gomez Miguez, Martin Manuel Bakalis, Evangelos and Zerbetto, Francesco

Abstract

Almost three-quarters of known volcanic activity on Earth occurs in underwater locations. The presence of active hydrothermal vent fields in such environments is a potential natural hazard for the environment, society, and economy. Despite its importance for risk assessment and risk mitigation, the monitoring of volcanic activity is impeded by the remoteness and the extreme conditions of many underwater volcanoes. The morphology and the activity of the submarine caldera, Avyssos, at the northern part of Nisyros volcano in the South Aegean Sea (Greece), were studied using a remotely operated underwater vehicle. The recorded time series of temperature and conductivity over the submarine volcano have been analyzed in terms of the Generalized Moments Method. This type of analysis can be used as an indicator for the state of activity of a submarine volcano. Here, we expand the work conducted for the first time in 2018. We present the findings of the geological exploration and the mathematical analysis, obtained from the data collected in October 2010. The temperature and conductivity time series show minor fluctuations in a rather stable environment. Based on these results, the impact of developing appropriate mechanisms and policies to avoid the associated natural hazard is expected to be important.

Published
2021

26. Radiative proton–capture reactions with 112,114Cd at astrophysically important energies.

Author

Vasileiou, Polytimos, Mertzimekis, Theo J., Chalil, Achment, Fakiola, Christina, Karakasis, Ioannis, Kotsovolou, Anastasia, Pelonis, Stefanos, and Zyriliou, Aikaterini

Subjects
*PROTONS, *X-ray spectroscopy, *ISOMERS, *MOLECULAR physics, *ISOMERISM
Abstract

The reaction network in the neutron-deficient part of the nuclear chart around A ≈ 100 contains several nuclei of importance to astrophysical processes, such as the p–process. This work reports on the results from recent experimental studies of the radiative proton–capture reactions 112,114Cd(p, γ)113,115 In. Experimental cross sections for the reactions have been measured for proton beam energies residing inside the respective Gamow windows for each reaction, using isotopically enriched 112Cd and 114Cd targets. Two different techniques, the in–beam γ–ray spectroscopy and the activation method have been implemented, where the latter is considered mandatory to account for the presence of low–lying isomers in 113In (E ≈ 392 keV, t1/2 ≈ 100 min), and 115In (E ≈ 336 keV, t1/2 ≈ 4.5 h). Following the measurement of the cross sections, the astrophysical S factors have been subsequently [ABSTRACT FROM AUTHOR]

Published
2022
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37. First radiative proton capture measurements on 107,109-Ag and 112-Cd relevant to the p-process

Author

Psaltis, Athanasios, Khaliel, Ahmed, Eleni-Myrto Assimakopoulou, Aggelos Babounis, Lagaki, Varvara, Kanellakopoulos, Anastasios, Lykiardopoulou, Marilena, Malami, Eleftheria, Psyrra, Ioanna, and Mertzimekis, Theo J.

Abstract

One of the important, but still unsettled topics in Nuclear Astrophysics is the production of the p-nuclei [1,2]. The p-process relies on an extended reaction network, which can be described theoretically by the Hauser-Feshbach statistical model, which in turn relies strongly on experimental data. To provide reliable data for p-nuclei, an experimental campaign at the Tandem Accelerator Laboratory of NCSR "Demokritos'', focusing on measurements of cross-sections in the 107,109Ag(p,γ)108,110Cd [3] and 112Cd(p,γ)113In [4]reactions was carried out. Both reactions were studied using a set of four HPGe detectors via the in-beam γ-ray spectroscopy, while for the latter the activation method was additionally employed to account for the population of a low-lying isomeric state. Total cross sections for proton beam energies lying inside the Gamow window for energies relevant to p-process nucleosynthesis were obtained for the first time. Experimental results are compared to Hauser-Feshbach calculations performed with the latest version of the TALYS code (v1.9) [5]. An overall good agreement has been achieved. These results provide important new input for the theoretical description of the p-process, but additionally for the origin of the cross-point p-nucleus 113In.References[1] M. Arnould and S. Goriely, Phys. Rep. 384, 1 (2003)[2] T. Rauscher et al., Rep. Prog. Phys. 76, 066201 (2013)[3] A. Khaliel et al., Phys. Rev. C 96, 035806 (2017)[4] A. Psaltis et al. (2018), in prep.[5] A. Koning, S. Hilaire and S. Goriely, TALYS-1.9, A Nuclear Reaction Program, NRG-1755 ZG Petten, The Netherlands (2017)Poster presented at the 15th International Symposium on Nuclei in the Cosmos (June 24-29, 2018 Assergi, L'Aquila, Italy)

Published
2018
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47. Nuclear structure and decay data evaluation in Europe

Author

Negret, Alexandru Balabanski, Dimiter Dimitriou, Paraskevi and Elekes, Zoltan Mertzimekis, Theo J. Pascu, Sorin Timar, Janos

Abstract

Nuclear Structure and Decay Data (NSDD) activities in Europe include mass-chain and individual nuclei evaluations as well as horizontal evaluations and compilations, data dissemination and educational activities. As such they are essential for a large range of applications from energy, environmental, and medical to basic research in nuclear structure and reactions, all of which are intensively pursued in Europe. Although the NSDD evaluation groups in Europe form part of the international network of NSDD evaluators, which is coordinated by the International Atomic Energy Agency, they are faced with some very distinct challenges. We shortly present the NSDD Data Centre at IFIN-HH, Bucharest and discuss possible actions to improve the situation for the entire European NSDD evaluation effort.

Published
2017

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