Identification of $\gamma$-decaying resonant states in 26Mg and their importance for the astrophysical s process

Lotay, G.; Doherty, D. T.; Seweryniak, D.; Almaraz-Calderon, S.; Carpenter, M. P.; Chiara, C. J.; David, H. M.; Hoffman, C. R.; Janssens, R. V.  F.; Kankainen, A.; Lauritsen, T.; Wilkinson, R.; Woods, P. J.; Zhu, S.

doi:10.1140/epja/i2019-12791-5

Identification of $$\gamma$$-decaying resonant states in ²⁶Mg and their importance for the astrophysical s process

Journal Article · Thu Jul 18 00:00:00 EDT 2019 · European Physical Journal. A

DOI:https://doi.org/10.1140/epja/i2019-12791-5· OSTI ID:1603662

Lotay, G. ^[1]; Doherty, D. T. ^[2]; Seweryniak, D. ^[3]; Almaraz-Calderon, S. ^[4]; Carpenter, M. P. ^[3]; Chiara, C. J. ^[5]; David, H. M. ^[6]; Hoffman, C. R. ^[3]; Janssens, R. V. F. ^[7]; Kankainen, A. ^[8]; Lauritsen, T. ^[3]; Wilkinson, R. ^[2]; Woods, P. J. ^[9]; Zhu, S. ^[3]

Univ. of Surrey, Guildford (United Kingdom); National Physical Lab., Middlesex (United Kingdom)
Univ. of Surrey, Guildford (United Kingdom)
Argonne National Lab. (ANL), Argonne, IL (United States)
Florida State Univ., Tallahassee, FL (United States); Argonne National Lab. (ANL), Argonne, IL (United States)
U.S. Army Research Lab., Adelphi, MD (United States); Argonne National Lab. (ANL), Argonne, IL (United States); Univ. of Maryland, College Park, MD (United States)
GSI Helmholtzzentrum für Schwerionenforschung GmbH, Darmstadt (Germany); Argonne National Lab. (ANL), Argonne, IL (United States)
Univ. of North Carolina, Chapel Hill, NC (United States); Duke Univ., Durham, NC (United States)
Univ. of Jyväskylä (Finland)
Univ. of Edinburgh (United Kingdom)

The ²²Ne(α, n) reaction is expected to provide the dominant neutron source for the weak s process in massive stars and intermediate-mass (IM) Asymptotic Giant Branch (AGB) stars. However, the production of neutrons in such environments is hindered by the competing ²²Ne(α,γ)²⁶Mg reaction. Here, the ¹¹B(¹⁶O,p) fusion-evaporation reaction was used to identify γ-decay transitions from ²²Ne + α resonant states in ²⁶Mg. Spin-parity restrictions have been placed on a number of α-unbound excited states in ²⁶ Mg and their role in the ²²Ne(α,γ)26Mg reaction has been investigated. In particular, a suspected natural-parity resonance at E_c.m. = 557(3) keV, that lies above the neutron threshold in ²⁶Mg, and is known to exhibit a strong α-cluster character, was observed to γ decay. Furthermore, a known resonance at E_c.m.= 466(4) keV has been definitively assigned 2⁺ spin and parity. Consequently, uncertainties in the ²²Ne(α,γ) stellar reaction rate have been reduced by a factor of ~20 for temperatures ~0.2 GK.

View Accepted Manuscript (DOE)

Research Organization:: Argonne National Laboratory (ANL), Argonne, IL (United States); University of North Carolina, Chapel Hill, NC (United States)

Sponsoring Organization:: USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities Division; USDOE Office of Science (SC), Nuclear Physics (NP); USDOE Office of Science (SC), Nuclear Physics (NP), Science and Technologies Facilities Council (STFC-UK)

Grant/Contract Number:: AC02-06CH11357; FG02-94ER40834; FG02-97ER41033

OSTI ID:: 1603662

Alternate ID(s):: OSTI ID: 1659325
OSTI ID: 1659326
OSTI ID: 22830965

Journal Information:: European Physical Journal. A, Journal Name: European Physical Journal. A Journal Issue: 7 Vol. 55; ISSN 1434-6001

Publisher:: SpringerCopyright Statement

Country of Publication:: United States

Language:: English

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