Astrophysics with Radioactive Isotopes

Deep underground laboratory measurement of 13C(α,n)16O in the Gamow windows of the s- and i-processes

Not scheduled

20m

Oral Presentation

Speaker

Weiping Lin (Institute of Nuclear Science and Technology, Sichuan University)

Description

The 13C(α,n)16O reaction is the main neutron source for the slow neutron capture process (s-process) in the Asymptotic Giant Branch (AGB) stars [1] and for the intermediate process (i-process) [2]. It is activated at the temperature around T = 0.1 GK [3,4] and 0.2 GK [2], which correspond to the Gamow windows of Ecm = 0.15 – 0.3 MeV and 0.2 – 0.54 MeV, for the s- and i-processes, respectively. Due to the vast cosmic background, direct measurements at the ground laboratories stopped at energies above Ecm = 0.27 MeV [5], unable to effectively constrain the crucial threshold state and provide a reliable extrapolation down to stellar energies. Besides that, the extrapolation accuracy is further limited by large discrepancies among those measurements [6,7]. We performed the first consistent direct measurement in the range of Ecm = 0.24 – 1.9 MeV using the accelerators at the China Jinping Underground Laboratory (CJPL) and Sichuan University. Our measurement covers almost the entire i-process Gamow window in which the large uncertainty of the previous experiments has been reduced from 60% down to 15%, eliminates the large systematic uncertainty in the extrapolation arising from the inconsistency of existing data sets, and provides a more reliable reaction rate for the studies of the s- and i-processes along with the first direct evidence for the near-threshold state.

References:
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[3] R. Gallino, C. Arlandini, M. Busso, M. Lugaro, C. Travaglio, O. Straniero, A. Chieffi, and M. Limongi, The Astrophysical Journal 497, 388 (1998).
[4] S. Bisterzo, C. Travaglio, M. Wiescher, F. Käppeler, and R. Gallino, The Astrophysical Journal 835, 97 (2017).
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[6] R. J. deBoer, C. R. Brune, M. Febrarro, J. Görres, I. J. Thompson, and M. Wiescher, Phys. Rev. C 101, 045802 (2020).
[7] D. Brown, M. Chadwick, R. Capote et al., Nuclear Data Sheets 148, 1 (2018), special Issue on Nuclear Reaction Data.