The $^{22}$Ne(α,γ)$^{26}$Mg and $^{22}$Ne(α,n)$^{25}$Mg reactions play an important role in astrophysics because they have significant influence on the neutron flux during the weak branch of the s-process. We constrain the astrophysical rates for these reactions by measuring partial α-widths of resonances in $^{26}$Mg located in the Gamow window for the <math><mmultiscripts><mrow><mi>Ne</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>22</mn></mrow></mmultiscripts><mo>+</mo><mi>α</mi></math> capture. These resonances were populated using $^{22}$Ne($^{6}$Li,d)$^{26}$Mg and $^{22}$Ne($^{7}$Li,t)$^{26}$Mg reactions at energies near the Coulomb barrier. At these low energies α-transfer reactions favor population of low spin states and the extracted partial α-widths for the observed resonances exhibit only minor dependence on the model parameters. The astrophysical rates for both the $^{22}$Ne(α,γ)$^{26}$Mg and the $^{22}$Ne(α,n)$^{25}$Mg reactions are shown to be significantly different than the previously suggested values.

United States

H. Jayatissa

G.V. Rogachev

V.Z. Goldberg

E. Koshchiy

G. Christian

J. Hooker

S. Ota

B.T. Roeder

A. Saastamoinen

Italy

O. Trippella

S. Upadhyayula

E. Uberseder

Constraining the Ne( , ) Mg and Ne( ,n) Mg reaction rates using sub-Coulomb -transfer Reactions

The structure of exotic nucleus 10 N was studied using 9 C+p resonance scattering. Two ℓ=0 resonances were found to be the lowest states in 10 N. The ground state of 10 N is unbound with respect to proton decay by 2.2(2) or 1.9(2) MeV depending on the 2− or 1− spin-parity assignment, and the first excited state is unbound by 2.8(2) MeV.

C. Hunt

C. Magana

Structure of 10 N in 9 C+p resonance scattering

The level structure of the very neutron rich and unbound 9 He nucleus has been the subject of significant experimental and theoretical study. Many recent works have claimed that the two lowest energy 9 He states exist with spins Jπ=1/2+ and Jπ=1/2− and widths on the order of 100–200 keV. These findings cannot be reconciled with our contemporary understanding of nuclear structure. The present work is the first high-resolution study with low statistical uncertainty of the relevant excitation energy range in the 8 He+n system, performed via a search for the T=5/2 isobaric analog states in 9 Li populated through 8 He+p elastic scattering. The present data show no indication of any narrow structures. Instead, we find evidence for a broad Jπ=1/2+ state in 9 He located approximately 3 MeV above the neutron decay threshold.

Canada

M. Alcorta

G. Chubarian

B. Davids

China

C. Fu

D. Melconian

R.E. Tribble

Nuclear structure beyond the neutron drip line: The lowest energy states in 9 He via their T = 5/2 isobaric analogs in 9 Li