Evidence for a spin-aligned neutron-proton paired phase from the level structure of 92Pd

B. Cederwall, F. Ghazi Moradi, T. Bäck, A. Johnson, J. Blomqvist, E. Clément, G. De France, R. Wadsworth, K. Andgren, K. Lagergren, A. Dijon, G. Jaworski, R. Liotta, C. Qi, B. Nyakó, J. Nyberg, M. Palacz, H. Al-Azri, A. Algora, G. De AngelisA. Atax̧, S. Bhattacharyya, T. Brock, J. R. Brown, P. Davies, A. Di Nitto, Zs. S. Dombrádi, A. Gadea, J. Gál, B. Hadinia, F. Johnston-Theasby, P. Joshi, K. Juhász, R. Julin, A. Jungclaus, G. Kalinka, S. O. Kara, A. Khaplanov, J. Kownacki, G. La Rana, S. M. Lenzi, J. Molnár, R. Moro, D. R. Napoli, B. S Nara Singh, A. Persson, F. Recchia, M. Sandzelius, J. N. Scheurer, G. Sletten, D. Sohler, P. A. Söderström, M. J. Taylor, J. Tímár, J. J. Valiente-Dón, E. Vardaci, S. Williams

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Abstract

Shell structure and magic numbers in atomic nuclei were generally explained by pioneering work that introduced a strong spin-orbit interaction to the nuclear shell model potential. However, knowledge of nuclear forces and the mechanisms governing the structure of nuclei, in particular far from stability, is still incomplete. In nuclei with equal neutron and proton numbers (N = Z), enhanced correlations arise between neutrons and protons (two distinct types of fermions) that occupy orbitals with the same quantum numbers. Such correlations have been predicted to favour an unusual type of nuclear superfluidity, termed isoscalar neutron-proton pairing, in addition to normal isovector pairing. Despite many experimental efforts, these predictions have not been confirmed. Here we report the experimental observation of excited states in the N = Z = 46 nucleus 92 Pd. Gamma rays emitted following the 58 Ni(36 Ar,2n) 92 Pd fusion-evaporation reaction were identified using a combination of state-of-the-art high-resolution β 3-ray, charged-particle and neutron detector systems. Our results reveal evidence for a spin-aligned, isoscalar neutron-proton coupling scheme, different from the previous prediction. We suggest that this coupling scheme replaces normal superfluidity (characterized by seniority coupling) in the ground and low-lying excited states of the heaviest N = Z nuclei. Such strong, isoscalar neutron-proton correlations would have a considerable impact on the nuclear level structure and possibly influence the dynamics of rapid proton capture in stellar nucleosynthesis.

Original languageEnglish
Pages (from-to)68-71
Number of pages4
JournalNature
Volume469
Issue number7328
DOIs
Publication statusPublished - Jan 6 2011

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Neutrons
Protons
Gamma Rays
Orbit
Observation

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Cederwall, B., Moradi, F. G., Bäck, T., Johnson, A., Blomqvist, J., Clément, E., ... Williams, S. (2011). Evidence for a spin-aligned neutron-proton paired phase from the level structure of 92Pd. Nature, 469(7328), 68-71. https://doi.org/10.1038/nature09644

Evidence for a spin-aligned neutron-proton paired phase from the level structure of 92Pd. / Cederwall, B.; Moradi, F. Ghazi; Bäck, T.; Johnson, A.; Blomqvist, J.; Clément, E.; De France, G.; Wadsworth, R.; Andgren, K.; Lagergren, K.; Dijon, A.; Jaworski, G.; Liotta, R.; Qi, C.; Nyakó, B.; Nyberg, J.; Palacz, M.; Al-Azri, H.; Algora, A.; De Angelis, G.; Atax̧, A.; Bhattacharyya, S.; Brock, T.; Brown, J. R.; Davies, P.; Di Nitto, A.; Dombrádi, Zs. S.; Gadea, A.; Gál, J.; Hadinia, B.; Johnston-Theasby, F.; Joshi, P.; Juhász, K.; Julin, R.; Jungclaus, A.; Kalinka, G.; Kara, S. O.; Khaplanov, A.; Kownacki, J.; La Rana, G.; Lenzi, S. M.; Molnár, J.; Moro, R.; Napoli, D. R.; Singh, B. S Nara; Persson, A.; Recchia, F.; Sandzelius, M.; Scheurer, J. N.; Sletten, G.; Sohler, D.; Söderström, P. A.; Taylor, M. J.; Tímár, J.; Valiente-Dón, J. J.; Vardaci, E.; Williams, S.

In: Nature, Vol. 469, No. 7328, 06.01.2011, p. 68-71.

Research output: Contribution to journalArticle

Cederwall, B, Moradi, FG, Bäck, T, Johnson, A, Blomqvist, J, Clément, E, De France, G, Wadsworth, R, Andgren, K, Lagergren, K, Dijon, A, Jaworski, G, Liotta, R, Qi, C, Nyakó, B, Nyberg, J, Palacz, M, Al-Azri, H, Algora, A, De Angelis, G, Atax̧, A, Bhattacharyya, S, Brock, T, Brown, JR, Davies, P, Di Nitto, A, Dombrádi, ZS, Gadea, A, Gál, J, Hadinia, B, Johnston-Theasby, F, Joshi, P, Juhász, K, Julin, R, Jungclaus, A, Kalinka, G, Kara, SO, Khaplanov, A, Kownacki, J, La Rana, G, Lenzi, SM, Molnár, J, Moro, R, Napoli, DR, Singh, BSN, Persson, A, Recchia, F, Sandzelius, M, Scheurer, JN, Sletten, G, Sohler, D, Söderström, PA, Taylor, MJ, Tímár, J, Valiente-Dón, JJ, Vardaci, E & Williams, S 2011, 'Evidence for a spin-aligned neutron-proton paired phase from the level structure of 92Pd', Nature, vol. 469, no. 7328, pp. 68-71. https://doi.org/10.1038/nature09644
Cederwall B, Moradi FG, Bäck T, Johnson A, Blomqvist J, Clément E et al. Evidence for a spin-aligned neutron-proton paired phase from the level structure of 92Pd. Nature. 2011 Jan 6;469(7328):68-71. https://doi.org/10.1038/nature09644
Cederwall, B. ; Moradi, F. Ghazi ; Bäck, T. ; Johnson, A. ; Blomqvist, J. ; Clément, E. ; De France, G. ; Wadsworth, R. ; Andgren, K. ; Lagergren, K. ; Dijon, A. ; Jaworski, G. ; Liotta, R. ; Qi, C. ; Nyakó, B. ; Nyberg, J. ; Palacz, M. ; Al-Azri, H. ; Algora, A. ; De Angelis, G. ; Atax̧, A. ; Bhattacharyya, S. ; Brock, T. ; Brown, J. R. ; Davies, P. ; Di Nitto, A. ; Dombrádi, Zs. S. ; Gadea, A. ; Gál, J. ; Hadinia, B. ; Johnston-Theasby, F. ; Joshi, P. ; Juhász, K. ; Julin, R. ; Jungclaus, A. ; Kalinka, G. ; Kara, S. O. ; Khaplanov, A. ; Kownacki, J. ; La Rana, G. ; Lenzi, S. M. ; Molnár, J. ; Moro, R. ; Napoli, D. R. ; Singh, B. S Nara ; Persson, A. ; Recchia, F. ; Sandzelius, M. ; Scheurer, J. N. ; Sletten, G. ; Sohler, D. ; Söderström, P. A. ; Taylor, M. J. ; Tímár, J. ; Valiente-Dón, J. J. ; Vardaci, E. ; Williams, S. / Evidence for a spin-aligned neutron-proton paired phase from the level structure of 92Pd. In: Nature. 2011 ; Vol. 469, No. 7328. pp. 68-71.
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abstract = "Shell structure and magic numbers in atomic nuclei were generally explained by pioneering work that introduced a strong spin-orbit interaction to the nuclear shell model potential. However, knowledge of nuclear forces and the mechanisms governing the structure of nuclei, in particular far from stability, is still incomplete. In nuclei with equal neutron and proton numbers (N = Z), enhanced correlations arise between neutrons and protons (two distinct types of fermions) that occupy orbitals with the same quantum numbers. Such correlations have been predicted to favour an unusual type of nuclear superfluidity, termed isoscalar neutron-proton pairing, in addition to normal isovector pairing. Despite many experimental efforts, these predictions have not been confirmed. Here we report the experimental observation of excited states in the N = Z = 46 nucleus 92 Pd. Gamma rays emitted following the 58 Ni(36 Ar,2n) 92 Pd fusion-evaporation reaction were identified using a combination of state-of-the-art high-resolution β 3-ray, charged-particle and neutron detector systems. Our results reveal evidence for a spin-aligned, isoscalar neutron-proton coupling scheme, different from the previous prediction. We suggest that this coupling scheme replaces normal superfluidity (characterized by seniority coupling) in the ground and low-lying excited states of the heaviest N = Z nuclei. Such strong, isoscalar neutron-proton correlations would have a considerable impact on the nuclear level structure and possibly influence the dynamics of rapid proton capture in stellar nucleosynthesis.",
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T1 - Evidence for a spin-aligned neutron-proton paired phase from the level structure of 92Pd

AU - Cederwall, B.

AU - Moradi, F. Ghazi

AU - Bäck, T.

AU - Johnson, A.

AU - Blomqvist, J.

AU - Clément, E.

AU - De France, G.

AU - Wadsworth, R.

AU - Andgren, K.

AU - Lagergren, K.

AU - Dijon, A.

AU - Jaworski, G.

AU - Liotta, R.

AU - Qi, C.

AU - Nyakó, B.

AU - Nyberg, J.

AU - Palacz, M.

AU - Al-Azri, H.

AU - Algora, A.

AU - De Angelis, G.

AU - Atax̧, A.

AU - Bhattacharyya, S.

AU - Brock, T.

AU - Brown, J. R.

AU - Davies, P.

AU - Di Nitto, A.

AU - Dombrádi, Zs. S.

AU - Gadea, A.

AU - Gál, J.

AU - Hadinia, B.

AU - Johnston-Theasby, F.

AU - Joshi, P.

AU - Juhász, K.

AU - Julin, R.

AU - Jungclaus, A.

AU - Kalinka, G.

AU - Kara, S. O.

AU - Khaplanov, A.

AU - Kownacki, J.

AU - La Rana, G.

AU - Lenzi, S. M.

AU - Molnár, J.

AU - Moro, R.

AU - Napoli, D. R.

AU - Singh, B. S Nara

AU - Persson, A.

AU - Recchia, F.

AU - Sandzelius, M.

AU - Scheurer, J. N.

AU - Sletten, G.

AU - Sohler, D.

AU - Söderström, P. A.

AU - Taylor, M. J.

AU - Tímár, J.

AU - Valiente-Dón, J. J.

AU - Vardaci, E.

AU - Williams, S.

PY - 2011/1/6

Y1 - 2011/1/6

N2 - Shell structure and magic numbers in atomic nuclei were generally explained by pioneering work that introduced a strong spin-orbit interaction to the nuclear shell model potential. However, knowledge of nuclear forces and the mechanisms governing the structure of nuclei, in particular far from stability, is still incomplete. In nuclei with equal neutron and proton numbers (N = Z), enhanced correlations arise between neutrons and protons (two distinct types of fermions) that occupy orbitals with the same quantum numbers. Such correlations have been predicted to favour an unusual type of nuclear superfluidity, termed isoscalar neutron-proton pairing, in addition to normal isovector pairing. Despite many experimental efforts, these predictions have not been confirmed. Here we report the experimental observation of excited states in the N = Z = 46 nucleus 92 Pd. Gamma rays emitted following the 58 Ni(36 Ar,2n) 92 Pd fusion-evaporation reaction were identified using a combination of state-of-the-art high-resolution β 3-ray, charged-particle and neutron detector systems. Our results reveal evidence for a spin-aligned, isoscalar neutron-proton coupling scheme, different from the previous prediction. We suggest that this coupling scheme replaces normal superfluidity (characterized by seniority coupling) in the ground and low-lying excited states of the heaviest N = Z nuclei. Such strong, isoscalar neutron-proton correlations would have a considerable impact on the nuclear level structure and possibly influence the dynamics of rapid proton capture in stellar nucleosynthesis.

AB - Shell structure and magic numbers in atomic nuclei were generally explained by pioneering work that introduced a strong spin-orbit interaction to the nuclear shell model potential. However, knowledge of nuclear forces and the mechanisms governing the structure of nuclei, in particular far from stability, is still incomplete. In nuclei with equal neutron and proton numbers (N = Z), enhanced correlations arise between neutrons and protons (two distinct types of fermions) that occupy orbitals with the same quantum numbers. Such correlations have been predicted to favour an unusual type of nuclear superfluidity, termed isoscalar neutron-proton pairing, in addition to normal isovector pairing. Despite many experimental efforts, these predictions have not been confirmed. Here we report the experimental observation of excited states in the N = Z = 46 nucleus 92 Pd. Gamma rays emitted following the 58 Ni(36 Ar,2n) 92 Pd fusion-evaporation reaction were identified using a combination of state-of-the-art high-resolution β 3-ray, charged-particle and neutron detector systems. Our results reveal evidence for a spin-aligned, isoscalar neutron-proton coupling scheme, different from the previous prediction. We suggest that this coupling scheme replaces normal superfluidity (characterized by seniority coupling) in the ground and low-lying excited states of the heaviest N = Z nuclei. Such strong, isoscalar neutron-proton correlations would have a considerable impact on the nuclear level structure and possibly influence the dynamics of rapid proton capture in stellar nucleosynthesis.

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