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Ahn DS, Amano J, Baba H, Fukuda N, Geissel H, Inabe N, Ishikawa S, Iwasa N, Komatsubara T, Kubo T, Kusaka K, Morrissey DJ, Nakamura T, Ohtake M, Otsu H, Sakakibara T, Sato H, Sherrill BM, Shimizu Y, Sumikama T, Suzuki H, Takeda H, Tarasov OB, Ueno H, Yanagisawa Y, Yoshida K. Discovery of ^{39}Na. Phys Rev Lett 2022; 129:212502. [PMID: 36461972 DOI: 10.1103/physrevlett.129.212502] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Revised: 09/08/2022] [Accepted: 09/14/2022] [Indexed: 06/17/2023]
Abstract
The new isotope ^{39}Na, the most neutron-rich sodium nucleus observed so far, was discovered at the RIKEN Nishina Center Radioactive Isotope Beam Factory using the projectile fragmentation of an intense ^{48}Ca beam at 345 MeV/nucleon on a beryllium target. Projectile fragments were separated and identified in flight with the large-acceptance two-stage separator BigRIPS. Nine ^{39}Na events have been unambiguously observed in this work and clearly establish the particle stability of ^{39}Na. Furthermore, the lack of observation of ^{35,36}Ne isotopes in this experiment significantly improves the overall confidence that ^{34}Ne is the neutron dripline nucleus of neon. These results provide new key information to understand nuclear binding and nuclear structure under extremely neutron-rich conditions. The newly established stability of ^{39}Na has a significant impact on nuclear models and theories predicting the neutron dripline and also provides a key to understanding the nuclear shell property of ^{39}Na at the neutron number N=28, which is normally a magic number.
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Affiliation(s)
- D S Ahn
- RIKEN Nishina Center for Accelerator-Based Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - J Amano
- Department of Physics, Rikkyo University, 3-34-1 Nishi-Ikebukuro, Toshima, Tokyo 171-8501, Japan
| | - H Baba
- RIKEN Nishina Center for Accelerator-Based Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - N Fukuda
- RIKEN Nishina Center for Accelerator-Based Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - H Geissel
- GSI, Helmholtzzentrum für Schwerionenforschung GmbH, Planckstraße 1, 64291 Darmstadt, Germany
| | - N Inabe
- RIKEN Nishina Center for Accelerator-Based Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - S Ishikawa
- Department of Physics, Tohoku University, 6-3, Aramaki Aza-Aoba, Aoba-ku, Sendai, Miyagi 980-8578, Japan
| | - N Iwasa
- Department of Physics, Tohoku University, 6-3, Aramaki Aza-Aoba, Aoba-ku, Sendai, Miyagi 980-8578, Japan
| | - T Komatsubara
- RIKEN Nishina Center for Accelerator-Based Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - T Kubo
- RIKEN Nishina Center for Accelerator-Based Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - K Kusaka
- RIKEN Nishina Center for Accelerator-Based Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - D J Morrissey
- National Superconducting Cyclotron Laboratory, Michigan State University, 640 South Shaw Lane, East Lansing, Michigan 48824, USA
| | - T Nakamura
- Department of Physics, Tokyo Institute of Technology, 2-12-1 O-Okayama, Meguro, Tokyo 152-8551, Japan
| | - M Ohtake
- RIKEN Nishina Center for Accelerator-Based Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - H Otsu
- RIKEN Nishina Center for Accelerator-Based Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - T Sakakibara
- Department of Physics, Tohoku University, 6-3, Aramaki Aza-Aoba, Aoba-ku, Sendai, Miyagi 980-8578, Japan
| | - H Sato
- RIKEN Nishina Center for Accelerator-Based Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - B M Sherrill
- National Superconducting Cyclotron Laboratory, Michigan State University, 640 South Shaw Lane, East Lansing, Michigan 48824, USA
| | - Y Shimizu
- RIKEN Nishina Center for Accelerator-Based Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - T Sumikama
- RIKEN Nishina Center for Accelerator-Based Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - H Suzuki
- RIKEN Nishina Center for Accelerator-Based Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - H Takeda
- RIKEN Nishina Center for Accelerator-Based Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - O B Tarasov
- National Superconducting Cyclotron Laboratory, Michigan State University, 640 South Shaw Lane, East Lansing, Michigan 48824, USA
| | - H Ueno
- RIKEN Nishina Center for Accelerator-Based Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Y Yanagisawa
- RIKEN Nishina Center for Accelerator-Based Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - K Yoshida
- RIKEN Nishina Center for Accelerator-Based Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
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Tsunoda N, Otsuka T, Takayanagi K, Shimizu N, Suzuki T, Utsuno Y, Yoshida S, Ueno H. The impact of nuclear shape on the emergence of the neutron dripline. Nature 2020; 587:66-71. [PMID: 33149291 DOI: 10.1038/s41586-020-2848-x] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2019] [Accepted: 09/03/2020] [Indexed: 11/08/2022]
Abstract
Atomic nuclei are composed of a certain number of protons Z and neutrons N. A natural question is how large Z and N can be. The study of superheavy elements explores the large Z limit1,2, and we are still looking for a comprehensive theoretical explanation of the largest possible N for a given Z-the existence limit for the neutron-rich isotopes of a given atomic species, known as the neutron dripline3. The neutron dripline of oxygen (Z = 8) can be understood theoretically as the result of single nucleons filling single-particle orbits confined by a mean potential, and experiments confirm this interpretation. However, recent experiments on heavier elements are at odds with this description. Here we show that the neutron dripline from fluorine (Z = 9) to magnesium (Z = 12) can be predicted using a mechanism that goes beyond the single-particle picture: as the number of neutrons increases, the nuclear shape assumes an increasingly ellipsoidal deformation, leading to a higher binding energy. The saturation of this effect (when the nucleus cannot be further deformed) yields the neutron dripline: beyond this maximum N, the isotope is unbound and further neutrons 'drip' out when added. Our calculations are based on a recently developed effective nucleon-nucleon interaction4, for which large-scale eigenvalue problems are solved using configuration-interaction simulations. The results obtained show good agreement with experiments, even for excitation energies of low-lying states, up to the nucleus of magnesium-40 (which has 28 neutrons). The proposed mechanism for the formation of the neutron dripline has the potential to stimulate further thinking in the field towards explaining nucleosynthesis with neutron-rich nuclei.
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Ahn DS, Fukuda N, Geissel H, Inabe N, Iwasa N, Kubo T, Kusaka K, Morrissey DJ, Murai D, Nakamura T, Ohtake M, Otsu H, Sato H, Sherrill BM, Shimizu Y, Suzuki H, Takeda H, Tarasov OB, Ueno H, Yanagisawa Y, Yoshida K. Location of the Neutron Dripline at Fluorine and Neon. Phys Rev Lett 2019; 123:212501. [PMID: 31809143 DOI: 10.1103/physrevlett.123.212501] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2019] [Indexed: 06/10/2023]
Abstract
A search for the heaviest isotopes of fluorine, neon, and sodium was conducted by fragmentation of an intense ^{48}Ca beam at 345 MeV/nucleon with a 20-mm-thick beryllium target and identification of isotopes in the large-acceptance separator BigRIPS at the RIKEN Radioactive Isotope Beam Factory. No events were observed for ^{32,33}F, ^{35,36}Ne, and ^{38}Na and only one event for ^{39}Na after extensive running. Comparison with predicted yields excludes the existence of bound states of these unobserved isotopes with high confidence levels. The present work indicates that ^{31}F and ^{34}Ne are the heaviest bound isotopes of fluorine and neon, respectively. The neutron dripline has thus been experimentally confirmed up to neon for the first time since ^{24}O was confirmed to be the dripline nucleus nearly 20 years ago. These data provide new keys to understanding the nuclear stability at extremely neutron-rich conditions.
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Affiliation(s)
- D S Ahn
- RIKEN Nishina Center for Accelerator-Based Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - N Fukuda
- RIKEN Nishina Center for Accelerator-Based Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - H Geissel
- GSI, Helmholtzzentrum für Schwerionenforschung GmbH, Planckstraße 1, 64291 Darmstadt, Germany
| | - N Inabe
- RIKEN Nishina Center for Accelerator-Based Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - N Iwasa
- Department of Physics, Tohoku University, 6-3, Aramaki Aza-Aoba, Aoba-ku, Sendai, Miyagi 980-8578, Japan
| | - T Kubo
- RIKEN Nishina Center for Accelerator-Based Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - K Kusaka
- RIKEN Nishina Center for Accelerator-Based Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - D J Morrissey
- National Superconducting Cyclotron Laboratory, Michigan State University, 640 South Shaw Lane, East Lansing, Michigan 48824, USA
| | - D Murai
- Department of Physics, Rikkyo University, 3-34-1 Nishi-Ikebukuro, Toshima, Tokyo 171-8501, Japan
| | - T Nakamura
- Department of Physics, Tokyo Institute of Technology, 2-12-1 O-Okayama, Meguro, Tokyo 152-8551, Japan
| | - M Ohtake
- RIKEN Nishina Center for Accelerator-Based Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - H Otsu
- RIKEN Nishina Center for Accelerator-Based Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - H Sato
- RIKEN Nishina Center for Accelerator-Based Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - B M Sherrill
- National Superconducting Cyclotron Laboratory, Michigan State University, 640 South Shaw Lane, East Lansing, Michigan 48824, USA
| | - Y Shimizu
- RIKEN Nishina Center for Accelerator-Based Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - H Suzuki
- RIKEN Nishina Center for Accelerator-Based Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - H Takeda
- RIKEN Nishina Center for Accelerator-Based Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - O B Tarasov
- National Superconducting Cyclotron Laboratory, Michigan State University, 640 South Shaw Lane, East Lansing, Michigan 48824, USA
| | - H Ueno
- RIKEN Nishina Center for Accelerator-Based Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Y Yanagisawa
- RIKEN Nishina Center for Accelerator-Based Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - K Yoshida
- RIKEN Nishina Center for Accelerator-Based Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
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4
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Lunderberg E, DeYoung PA, Kohley Z, Attanayake H, Baumann T, Bazin D, Christian G, Divaratne D, Grimes SM, Haagsma A, Finck JE, Frank N, Luther B, Mosby S, Nagi T, Peaslee GF, Schiller A, Snyder J, Spyrou A, Strongman MJ, Thoennessen M. Evidence for the ground-state resonance of 26O. Phys Rev Lett 2012; 108:142503. [PMID: 22540789 DOI: 10.1103/physrevlett.108.142503] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2011] [Indexed: 05/31/2023]
Abstract
Evidence for the ground state of the neutron-unbound nucleus (26)O was observed for the first time in the single proton-knockout reaction from a 82 MeV/u (27)F beam. Neutrons were measured in coincidence with (24)O fragments. (26)O was determined to be unbound by 150(-150)(+50) keV from the observation of low-energy neutrons. This result agrees with recent shell-model calculations based on microscopic two- and three-nucleon forces.
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Affiliation(s)
- E Lunderberg
- Department of Physics, Hope College, Holland, Michigan 49423, USA
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5
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Abstract
Invariant mass measurements and breakup reactions of neutron-rich nuclei have been instrumental in the study of nuclear structure effects at the limit of nuclear existence. The measurements of neutron-unbound states rely on the detection of neutrons in coincidence with fragments at energies between 100 and 1000 MeV/u. Charged particle and γ-ray coincidence measurements yield additional information. The production and detection methods for these experiments and examples of results in light nuclei are presented. Future opportunities with new facilities and the development of new detectors are described.
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Affiliation(s)
- T Baumann
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824-1321, USA.
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6
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Christian G, Frank N, Ash S, Baumann T, Bazin D, Brown J, DeYoung PA, Finck JE, Gade A, Grinyer GF, Grovom A, Hinnefeld JD, Lunderberg EM, Luther B, Mosby M, Mosby S, Nagi T, Peaslee GF, Rogers WF, Smith JK, Snyder J, Spyrou A, Strongman MJ, Thoennessen M, Warren M, Weisshaar D, Wersal A. Exploring the low-Z shore of the island of inversion at n=19. Phys Rev Lett 2012; 108:032501. [PMID: 22400733 DOI: 10.1103/physrevlett.108.032501] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2011] [Indexed: 05/31/2023]
Abstract
The technique of invariant mass spectroscopy has been used to measure, for the first time, the ground state energy of neutron-unbound (28)F, determined to be a resonance in the (27)F+n continuum at 220(50) keV. States in (28)F were populated by the reactions of a 62 MeV/u (29)Ne beam impinging on a 288 mg/cm(2) beryllium target. The measured (28)F ground state energy is in good agreement with USDA/USDB shell model predictions, indicating that pf shell intruder configurations play only a small role in the ground state structure of (28)F and establishing a low-Z boundary of the island of inversion for N=19 isotones.
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Affiliation(s)
- G Christian
- Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA.
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7
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Abstract
The limit of neutron-rich nuclei, the neutron drip line, evolves regularly from light to medium-mass nuclei except for a striking anomaly in the oxygen isotopes. This anomaly is not reproduced in shell-model calculations derived from microscopic two-nucleon forces. Here, we present the first microscopic explanation of the oxygen anomaly based on three-nucleon forces that have been established in few-body systems. This leads to repulsive contributions to the interactions among excess neutrons that change the location of the neutron drip line from (28)O to the experimentally observed (24)O. Since the mechanism is robust and general, our findings impact the prediction of the most neutron-rich nuclei and the synthesis of heavy elements in neutron-rich environments.
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Affiliation(s)
- Takaharu Otsuka
- Department of Physics, University of Tokyo, Hongo, Tokyo 113-0033, Japan
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8
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Tarasov OB, Morrissey DJ, Amthor AM, Baumann T, Bazin D, Gade A, Ginter TN, Hausmann M, Inabe N, Kubo T, Nettleton A, Pereira J, Portillo M, Sherrill BM, Stolz A, Thoennessen M. Evidence for a change in the nuclear mass surface with the discovery of the most neutron-rich nuclei with 17<or=Z<or=25. Phys Rev Lett 2009; 102:142501. [PMID: 19392430 DOI: 10.1103/physrevlett.102.142501] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2009] [Indexed: 05/27/2023]
Abstract
The results of measurements of the production of neutron-rich nuclei by the fragmentation of a 76Ge beam are presented. The cross sections were measured for a large range of nuclei including 15 new isotopes that are the most neutron-rich nuclides of the elements chlorine to manganese (50Cl, 53Ar, ;{55,56}K, ;{57,58}Ca, ;{59,60,61}Sc, ;{62,63}Ti, ;{65,66}V, 68Cr, 70Mn). The enhanced cross sections of several new nuclei relative to a simple thermal evaporation framework, previously shown to describe similar production cross sections, indicates that nuclei in the region around 62Ti might be more stable than predicted by current mass models and could be an indication of a new island of inversion similar to that centered on 31Na.
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Affiliation(s)
- O B Tarasov
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
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9
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Hoffman CR, Baumann T, Bazin D, Brown J, Christian G, DeYoung PA, Finck JE, Frank N, Hinnefeld J, Howes R, Mears P, Mosby E, Mosby S, Reith J, Rizzo B, Rogers WF, Peaslee G, Peters WA, Schiller A, Scott MJ, Tabor SL, Thoennessen M, Voss PJ, Williams T. Determination of the N=16 shell closure at the oxygen drip line. Phys Rev Lett 2008; 100:152502. [PMID: 18518100 DOI: 10.1103/physrevlett.100.152502] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2007] [Indexed: 05/26/2023]
Abstract
The neutron unbound ground state of (25)O (Z=8, N=17) was observed for the first time in a proton knockout reaction from a (26)F beam. A single resonance was found in the invariant mass spectrum corresponding to a neutron decay energy of 770_+20(-10) keV with a total width of 172(30) keV. The N=16 shell gap was established to be 4.86(13) MeV by the energy difference between the nu1s(1/2) and nu0d(3/2) orbitals. The neutron separation energies for (25)O agree with the calculations of the universal sd shell model interaction. This interaction incorrectly predicts an (26)O ground state that is bound to two-neutron decay by 1 MeV, leading to a discrepancy between the theoretical calculations and experiment as to the particle stability of (26)O. The observed decay width was found to be on the order of a factor of 2 larger than the calculated single-particle width using a Woods-Saxon potential.
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Affiliation(s)
- C R Hoffman
- Department of Physics, Florida State University, Tallahassee, FL 32303, USA.
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10
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Morrissey DJ. Projectile Fragmentation Studies with the Most Exotic Nuclei. The Nucleus 2000. [DOI: 10.1007/978-1-4615-4257-5_43] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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12
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Kryger RA, Azhari A, Brown J, Caggiano J, Hellström M, Kelley JH, Sherrill BM, Steiner M, Thoennessen M. Upper limit of the lifetime of 16B. Phys Rev C Nucl Phys 1996; 53:1971-1973. [PMID: 9971157 DOI: 10.1103/physrevc.53.1971] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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13
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Pfaff R, Morrissey DJ, Benenson W, Fauerbach M, Hellström M, Powell CF, Sherrill BM, Steiner M, Winger JA. Fragmentation of 78Kr projectiles. Phys Rev C Nucl Phys 1996; 53:1753-1758. [PMID: 9971126 DOI: 10.1103/physrevc.53.1753] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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