Speaker
Description
nvestigating Branching Points and Isomeric Influences in the s-Process
near A ∼ 180
Shrikant Thorat1,2, Sutanu Bhattacharya3, B. Maheshwari4, A.K.Jain1,5, A. Goel1, and R. Palit2
1Amity Institute of Nuclear Science & Technology, Amity University Uttar Pradesh, Noida, India
2Department of Nuclear and Atomic Physics, Tata Institute of Fundamental Research, Mumbai, India
3Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem-91904, Israel
4Grand Acc´el´erateur National d’Ions Lourds, CEA/DSM-CNRS/IN2P3, Bvd Henri Becquerel, BP55027, F-14076,
Caen, France
5Department of Physics, Indian Institute of Technology Roorkee, Roorkee-247667, India
Abstract
The slow neutron capture process (s-process) near A ∼ 180 plays a critical role in stellar nucleosynthe-
sis, with isomeric states significantly influencing nuclear reaction pathways[1]. These states, characterized
by their unique decay properties and long half-lives, act as branching points that redirect the nucle-
osynthetic flow under stellar conditions. In particular, isomeric states allow for neutron capture over
extended timescales, thereby modifying isotopic abundances and affecting the relative ratios of heavy
elements. Moreover, the presence of isomers in nuclei such as 176Lu, 186Re, and 192Ir introduces addi-
tional pathways[2], which are sensitive to the temperature and neutron density of the stellar environment.
Understanding these mechanisms is crucial for accurate modeling of nucleosynthesis in asymptotic giant
branch (AGB) stars and other astrophysical sites[3].
Our study focuses on calculating the effective thermalization temperature formalism to analyze the
astrophysical importance of long-lived isomeric states[4, 5], such as 176Lu (7−, 122.845 keV, T1/2 = 3.67
h), 186Re (8+, 148.3 keV, T1/2 = 2.0 × 105 yr), and 192Ir (11−, 168.1 keV, T1/2 = 241 yr)[6]. These nuclei
serve as branching points within the s-process due to their long half-lives and distinct spin states, which
impact neutron capture and decay chains. By integrating these isomeric states into computational nuclear
networks, we aim to resolve discrepancies in abundance predictions for elements in this mass region. This
study underscores the necessity of precise nuclear data for isomers in the A ∼ 180 region to refine stellar
models and improve our understanding of heavy-element synthesis in the universe.
References
[1] E. M. Burbidge, G. Burbidge, W. Fowler, F. Hoyle, Rev. Mod.phys., 29 (1957) 547.
[2] A. K. Jain, B. Maheshwari, A. Goel, Nuclear Isomers: A Primer, Springer Nature (2021) ;Nuclear
Isomers, Ed: P.M.Walker, A.K. Jain, B. Maheshwari, EPJ-ST 233, No. 5, (2024).
[3] F. K¨appeler, R. Gallino, S. Bisterzo, & Aoki, W. Rev. Mod. Phys., 83 (2011) 157.
[4] S.S.Gupta, B.S. Meyer, Physical Review C, 64 (2001) 025805.
[5] R. A. Ward, W.A. Fowler, Astrophys. J. 238 (1980) 266.
[6] G. W. Misch, S.K. Ghorui, P. Banerjee, Y. Sun, M.R. Mumpower, Astrophys. J. Suppl. Ser. 252
(2020) 2.
