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

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.M. Nyako, J. Nyberg, M. Palacz, H. Al-Azri, A. Algora, G. de Angelis & 37 others A. Ataç, S. Bhattacharyya, T. Brock, J.R. Brown, P. Davies, A. Di Nitto, Zs. 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. Timár, J.J. Valiente-Dobón, E. Vardaci, S. Williams

Research output: Contribution to journalLetter

Abstract

Shell structure and magic numbers in atomic nuclei were generally explained by pioneering work1 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 pairing2,3,4,5,6, 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 92Pd. Gamma rays emitted following the 58Ni(36Ar,2n)92Pd fusion–evaporation reaction were identified using a combination of state-of-the-art high-resolution γ-ray, charged-particle and neutron detector systems. Our results reveal evidence for a spin-aligned, isoscalar neutron–proton coupling scheme, different from the previous prediction2,3,4,5,6. We suggest that this coupling scheme replaces normal superfluidity (characterized by seniority coupling7,8) 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 - 6 Jan 2011
Externally publishedYes

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neutrons
nuclei
protons
superfluidity
neutron counters
radiation counters
nuclear fusion
quantum numbers
excitation
rays
charged particles
fermions
gamma rays
orbitals
high resolution
predictions

Keywords

  • atomica and molecular physics

Cite this

Cederwall, B., Ghazi Moradi, F., 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 Pd-92. Nature, 469(7328), 68-71. https://doi.org/10.1038/nature09644
Cederwall, B. ; Ghazi Moradi, F. ; 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. ; Nyako, B.M. ; Nyberg, J. ; Palacz, M. ; Al-Azri, H. ; Algora, A. ; de Angelis, G. ; Ataç, A. ; Bhattacharyya, S. ; Brock, T. ; Brown, J.R. ; 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, S.O. ; Khaplanov, A. ; Kownacki, J. ; La Rana, G. ; Lenzi, S.M. ; Molnár, J. ; Moro, R. ; Napoli, D.R. ; Nara Singh, B.S. ; Persson, A. ; Recchia, F. ; Sandzelius, M. ; Scheurer, J.-N. ; Sletten, G. ; Sohler, D. ; Söderström, P.-A. ; Taylor, M.J. ; Timár, J. ; Valiente-Dobón, J.J. ; Vardaci, E. ; Williams, S. / Evidence for a spin-aligned neutron-proton paired phase from the level structure of Pd-92. 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 work1 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 pairing2,3,4,5,6, 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 92Pd. Gamma rays emitted following the 58Ni(36Ar,2n)92Pd fusion–evaporation reaction were identified using a combination of state-of-the-art high-resolution γ-ray, charged-particle and neutron detector systems. Our results reveal evidence for a spin-aligned, isoscalar neutron–proton coupling scheme, different from the previous prediction2,3,4,5,6. We suggest that this coupling scheme replaces normal superfluidity (characterized by seniority coupling7,8) 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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Cederwall, B, Ghazi Moradi, F, 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, Nyako, BM, Nyberg, J, Palacz, M, Al-Azri, H, Algora, A, de Angelis, G, Ataç, A, Bhattacharyya, S, Brock, T, Brown, JR, Davies, P, Di Nitto, A, Dombrádi, Z, 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, Nara Singh, BS, Persson, A, Recchia, F, Sandzelius, M, Scheurer, J-N, Sletten, G, Sohler, D, Söderström, P-A, Taylor, MJ, Timár, J, Valiente-Dobón, JJ, Vardaci, E & Williams, S 2011, 'Evidence for a spin-aligned neutron-proton paired phase from the level structure of Pd-92' Nature, vol. 469, no. 7328, pp. 68-71. https://doi.org/10.1038/nature09644

Evidence for a spin-aligned neutron-proton paired phase from the level structure of Pd-92. / Cederwall, B.; Ghazi Moradi, F.; 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.; Nyako, B.M.; Nyberg, J.; Palacz, M.; Al-Azri, H.; Algora, A.; de Angelis, G.; Ataç, A.; Bhattacharyya, S.; Brock, T.; Brown, J.R.; 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, S.O.; Khaplanov, A.; Kownacki, J.; La Rana, G.; Lenzi, S.M.; Molnár, J.; Moro, R.; Napoli, D.R.; Nara Singh, B.S.; Persson, A.; Recchia, F.; Sandzelius, M.; Scheurer, J.-N.; Sletten, G.; Sohler, D.; Söderström, P.-A.; Taylor, M.J.; Timár, J.; Valiente-Dobón, J.J.; Vardaci, E.; Williams, S.

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

Research output: Contribution to journalLetter

TY - JOUR

T1 - Evidence for a spin-aligned neutron-proton paired phase from the level structure of Pd-92

AU - Cederwall, B.

AU - Ghazi Moradi, F.

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 - Nyako, B.M.

AU - Nyberg, J.

AU - Palacz, M.

AU - Al-Azri, H.

AU - Algora, A.

AU - de Angelis, G.

AU - Ataç, A.

AU - Bhattacharyya, S.

AU - Brock, T.

AU - Brown, J.R.

AU - Davies, P.

AU - Di Nitto, A.

AU - Dombrádi, Zs.

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 - Nara Singh, B.S.

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 - Timár, J.

AU - Valiente-Dobón, 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 work1 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 pairing2,3,4,5,6, 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 92Pd. Gamma rays emitted following the 58Ni(36Ar,2n)92Pd fusion–evaporation reaction were identified using a combination of state-of-the-art high-resolution γ-ray, charged-particle and neutron detector systems. Our results reveal evidence for a spin-aligned, isoscalar neutron–proton coupling scheme, different from the previous prediction2,3,4,5,6. We suggest that this coupling scheme replaces normal superfluidity (characterized by seniority coupling7,8) 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 work1 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 pairing2,3,4,5,6, 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 92Pd. Gamma rays emitted following the 58Ni(36Ar,2n)92Pd fusion–evaporation reaction were identified using a combination of state-of-the-art high-resolution γ-ray, charged-particle and neutron detector systems. Our results reveal evidence for a spin-aligned, isoscalar neutron–proton coupling scheme, different from the previous prediction2,3,4,5,6. We suggest that this coupling scheme replaces normal superfluidity (characterized by seniority coupling7,8) 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.

KW - atomica and molecular physics

U2 - 10.1038/nature09644

DO - 10.1038/nature09644

M3 - Letter

VL - 469

SP - 68

EP - 71

JO - Nature

JF - Nature

SN - 1476-4687

IS - 7328

ER -

Cederwall B, Ghazi Moradi F, Bäck T, Johnson A, Blomqvist J, Clément E et al. Evidence for a spin-aligned neutron-proton paired phase from the level structure of Pd-92. Nature. 2011 Jan 6;469(7328):68-71. https://doi.org/10.1038/nature09644