Branching Points on the Path of the Slow Neutron-Capture Process

  • Maria LugaroEmail author
  • Alessandro Chieffi
Part of the Astrophysics and Space Science Library book series (ASSL, volume 453)


We supplement this book, and in particular the discussion of stellar nucleosynthesis presented in Chap.  3, with a list of the unstable isotopes at which branching points become relevant in the s-process reaction chain in AGB stars. For sake of clarity and a better understanding it is advisable to go through the list with a chart of the nuclides at hand. For each branching point a brief description of its operation and its relevance in the study of the s process in AGB stars is presented. The 21 branching points highlighted by a star symbol next to their atomic mass are those that Käppeler et al. (2011) considered as interesting candidates for future Time-Of-Flight (TOF) measurements of their neutron-capture cross sections. All listed isotopes suffer β decay, unless specified otherwise. It should also be noted that usually in s-process conditions nuclear energy metastable levels higher than the ground state are not populated, thus the effect of these states does not need to be included in the study of branching points, except for the special cases reported in the list (see also Ward 1977).


  1. Abbondanno U, Aerts G, Alvarez-Velarde F, Álvarez-Pol H, Andriamonje S, Andrzejewski J, Badurek G, Baumann P, Bečvář F, Benlliure J, Berthoumieux E, Calviño F, Cano-Ott D, Capote R, Cennini P, Chepel V, Chiaveri E, Colonna N, Cortes G, Cortina D, Couture A, Cox J, Dababneh S, Dahlfors M, David S, Dolfini R, Domingo-Pardo C, Duran I, Embid-Segura M, Ferrant L, Ferrari A, Ferreira-Marques R, Frais-Koelbl H, Furman W, Goncalves I, Gallino R, Gonzalez-Romero E, Goverdovski A, Gramegna F, Griesmayer E, Gunsing F, Haas B, Haight R, Heil M, Herrera-Martinez A, Isaev S, Jericha E, Käppeler F, Kadi Y, Karadimos D, Kerveno M, Ketlerov V, Koehler P, Konovalov V, Krtička M, Lamboudis C, Leeb H, Lindote A, Lopes I, Lozano M, Lukic S, Marganiec J, Marrone S, Martinez-Val J, Mastinu P, Mengoni A, Milazzo PM, Molina-Coballes A, Moreau C, Mosconi M, Neves F, Oberhummer H, O’Brien S, Pancin J, Papaevangelou T, Paradela C, Pavlik A, Pavlopoulos P, Perlado JM, Perrot L, Pignatari M, Plag R, Plompen A, Plukis A, Poch A, Policarpo A, Pretel C, Quesada J, Raman S, Rapp W, Rauscher T, Reifarth R, Rosetti M, Rubbia C, Rudolf G, Rullhusen P, Salgado J, Soares JC, Stephan C, Tagliente G, Tain J, Tassan-Got L, Tavora L, Terlizzi R, Vannini G, Vaz P, Ventura A, Villamarin D, Vincente MC, Vlachoudis V, Voss F, Wendler H, Wiescher M, Wisshak K (2004) Neutron capture cross section measurement of 151Sm at the CERN neutron time of flight facility (n_TOF). Phys Rev Lett 93(16):161103. ADSCrossRefGoogle Scholar
  2. Abia C, Busso M, Gallino R, Domínguez I, Straniero O, Isern J (2001) The 85Kr s-process branching and the mass of carbon stars. Astrophys J 559:1117–1134., arXiv:astro-ph/0105486ADSCrossRefGoogle Scholar
  3. Ávila JN, Lugaro M, Ireland TR, Gyngard F, Zinner E, Cristallo S, Holden P, Buntain J, Amari S, Karakas A (2012) Tungsten isotopic compositions in stardust SiC grains from the Murchison meteorite: constraints on the s-process in the Hf-Ta-W-Re-Os Region. Astrophys J 744:49., 1110.4763ADSCrossRefGoogle Scholar
  4. Ávila JN, Ireland TR, Lugaro M, Gyngard F, Zinner E, Cristallo S, Holden P, Rauscher T (2013) Europium s-process signature at close-to-solar metallicity in stardust SiC grains from asymptotic giant branch stars. Astrophys J 768:L18., 1303.5932ADSCrossRefGoogle Scholar
  5. Brandon AD, Humayun M, Puchtel IS, Leya I, Zolensky M (2005) Osmium isotope evidence for an s-Process carrier in primitive chondrites. Science 309:1233–1236. ADSCrossRefGoogle Scholar
  6. Clayton DD, Rassbach ME (1967) Termination of the s-PROCESS. Astrophys J 148:69. ADSCrossRefGoogle Scholar
  7. Gallino R, Busso M, Lugaro M (1997) Neutron capture nucleosynthesis in AGB stars. In: Bernatowicz TJ, Zinner E (eds) American Institute of Physics conference series, vol 402, pp 115–153.
  8. Heil M, Winckler N, Dababneh S, Käppeler F, Wisshak K, Bisterzo S, Gallino R, Davis AM, Rauscher T (2008) 176Lu/176Hf: a sensitive test of s-Process temperature and neutron density in AGB stars. Astrophys J 673:434–444. ADSCrossRefGoogle Scholar
  9. Humayun M, Brandon AD (2007) s-Process implications from osmium isotope anomalies in chondrites. Astrophys J 664:L59–L62. ADSCrossRefGoogle Scholar
  10. Jaag S, Käppeler F (1995) Stellar (n,γ) cross section of the unstable isotope 155Eu. Phys Rev C 51:3465–3471. ADSCrossRefGoogle Scholar
  11. Käppeler F, Arlandini C, Heil M, Voss F, Wisshak K, Reifarth R, Straniero O, Gallino R, Masera S, Travaglio C (2004) Stellar neutron capture on \(^{180 }_{ }\)Tam. II. Defining the s-process contribution to nature’s rarest isotope. Phys Rev C 69(5):055802.
  12. Käppeler F, Gallino R, Bisterzo S, Aoki W (2011) The s process: nuclear physics, stellar models, and observations. Rev Mod Phys 83:157–194., 1012.5218ADSCrossRefGoogle Scholar
  13. Klay N, Käppeler F (1988) β-decay rate of 79mSe and its consequences for the s-process temperature. Phys Rev C 38:295–306. ADSCrossRefGoogle Scholar
  14. Lambert DL, Smith VV, Busso M, Gallino R, Straniero O (1995) The chemical composition of red giants. IV. The neutron density at the s-Process site. Astrophys J 450:302. ADSCrossRefGoogle Scholar
  15. Lugaro M, Davis AM, Gallino R, Pellin MJ, Straniero O, Käppeler F (2003) Isotopic compositions of strontium, zirconium, molybdenum, and barium in single Presolar SiC grains and asymptotic giant branch stars. Astrophys J 593:486–508. ADSCrossRefGoogle Scholar
  16. Lugaro M, Tagliente G, Karakas AI, Milazzo PM, Käppeler F, Davis AM, Savina MR (2014) The impact of updated Zr neutron-capture cross sections and new asymptotic giant branch models on our understanding of the S process and the origin of stardust. Astrophys J 780:95., 1311.2660ADSCrossRefGoogle Scholar
  17. Macklin RL (1985a) Neutron capture measurements on fission product107Pd. Nucl Sci Eng 89:79CrossRefGoogle Scholar
  18. Macklin RL (1985b) Neutron capture measurements on radioactive Zr-93. Astrophys Space Sci 115:71–83. ADSCrossRefGoogle Scholar
  19. Mauersberger R, Ott U, Henkel C, Cernicharo J, Gallino R (2004) The abundance of 36S in IRC+10216 and its production in the Galaxy. Astron Astrophys 426:219–227., arXiv:astro-ph/0407003ADSCrossRefGoogle Scholar
  20. Mohr P, Shizuma T, Ueda H, Goko S, Makinaga A, Hara KY, Hayakawa T, Lui Y, Ohgaki H, Utsunomiya H (2004) s-process branching at \(^{185}_{ }\)W revised. Phys Rev C 69(3):032801., arXiv:astro-ph/0409642
  21. Mohr P, Bisterzo S, Gallino R, Käppeler F, Kneissl U, Winckler N (2009) Properties of the 5 state at 839 keV in Lu176 and the s-process branching at A=176. Phys Rev C 79(4):045804., 0903.3897
  22. Patronis N, Dababneh S, Assimakopoulos PA, Gallino R, Heil M, Käppeler F, Karamanis D, Koehler PE, Mengoni A, Plag R (2004) Neutron capture studies on unstable 135Cs for nucleosynthesis and transmutation. Phys Rev C 69(2):025803. ADSCrossRefGoogle Scholar
  23. Ratzel U, Arlandini C, Käppeler F, Couture A, Wiescher M, Reifarth R, Gallino R, Mengoni A, Travaglio C (2004) Nucleosynthesis at the termination point of the s process. Phys Rev C 70(6):065803. ADSCrossRefGoogle Scholar
  24. Rauscher T (2012) Formalism for inclusion of measured reaction cross sections in stellar rates including uncertainties and its application to neutron capture in the s-process. Astrophys J 755:L10., 1207.1664ADSCrossRefGoogle Scholar
  25. Reifarth R, Arlandini C, Heil M, Käppeler F, Sedyshev PV, Mengoni A, Herman M, Rauscher T, Gallino R, Travaglio C (2003) Stellar neutron capture on promethium: implications for the s-Process neutron density. Astrophys J 582:1251–1262. ADSCrossRefGoogle Scholar
  26. Reifarth R, Käppeler F, Voss F, Wisshak K, Gallino R, Pignatari M, Straniero O (2004) 128Xe and 130Xe: testing He-Shell burning in asymptotic giant branch stars. Astrophys J 614:363–370., arXiv:astro-ph/0405065ADSCrossRefGoogle Scholar
  27. Sonnabend K, Mengoni A, Mohr P, Rauscher T, Vogt K, Zilges A (2003) Determination of the (n, γ) reaction rate of unstable 185W in the astrophysical s-process via its inverse reaction. Nucl Phys A 718:533–535. ADSCrossRefGoogle Scholar
  28. Takahashi K, Yokoi K (1987) Beta-decay rates of highly ionized heavy atoms in stellar interiors. Atom Data Nucl Data Tables 36:375. ADSCrossRefGoogle Scholar
  29. Toukan KA, Kaeppeler F (1990) The stellar neutron capture cross sections of Zr-94 and Zr-96. Astrophys J 348:357–362. ADSCrossRefGoogle Scholar
  30. van Raai MA, Lugaro M, Karakas AI, García-Hernández DA, Yong D (2012) Rubidium, zirconium, and lithium production in intermediate-mass asymptotic giant branch stars. Astron Astrophys 540:A44., 1202.2620ADSCrossRefGoogle Scholar
  31. Vockenhuber C, Dillmann I, Heil M, Käppeler F, Winckler N, Kutschera W, Wallner A, Bichler M, Dababneh S, Bisterzo S, Gallino R (2007) Stellar (n,γ) cross sections of Hf174 and radioactive Hf182. Phys Rev C 75(1):015804. ADSCrossRefGoogle Scholar
  32. Ward RA (1977) The importance of long-lived isomeric states in s-Process branching. Astrophys J 216:540–547ADSGoogle Scholar
  33. Wisshak K, Voss F, Käppeler F, Krtička M, Raman S, Mengoni A, Gallino R (2006) Stellar neutron capture cross section of the unstable s-process branching point 151Sm. Phys Rev C 73(1):015802. ADSCrossRefGoogle Scholar
  34. Yan SQ, Li ZH, Wang YB, Nishio K, Lugaro M, Karakas AI, Makii H, Mohr P, Su J, Li YJ, Nishinaka I, Hirose K, Han YL, Orlandi R, Shen YP, Guo B, Zeng S, Lian G, Chen YS, Liu WP (2017) The 95Zr(n, γ)96Zr cross section from the surrogate ratio method and its effect on s-process nucleosynthesis. Astrophys J 848:98., 1709.04635ADSCrossRefGoogle Scholar
  35. Yin QZ, Lee CTA, Ott U (2006) Signatures of the s-Process in presolar silicon carbide grains: barium through hafnium. Astrophys J 647:676–684. ADSCrossRefGoogle Scholar

Copyright information

© The Author(s) 2018

Authors and Affiliations

  1. 1.Monash Centre for AstrophysicsMonash UniversityClayton, VICAustralia
  2. 2.Konkoly Observatory, Research Centre for Astronomy and Earth SciencesHungarian Academy of SciencesBudapestHungary
  3. 3.Istituto Nazionale Astronomia Fisica INAFRomaItaly

Personalised recommendations