Excitation energies of levels in 23Na, 24Mg and 26Mg

Probing astrophysically important states in theMg26nucleus to study neutron sources for thesprocess

“…A number of scattering and transfer measurements ( [50], [51], [52], [42], [53], [54] and [55]) have been performed to investigate the level structure of 26 Mg above the α-threshold. 26 Mg by Longland et al [55] and deBoer et al [58] and 26 Mg(γ, n) 25 Mg measurement by deBoer et al [59].…”

Photoexcitation of astrophysically important states inMg26. II. Ground-state-transition partial widths

“…While 13 C(α,n) 16 O is considered to be the chief source of neutrons in the main s-process, 22 Ne(α,n) 25 Mg may also have a dominant role. As a main source of neutrons for the s-process the uncertainty in the 22 Ne(α,n) 25 Mg reaction rate as well as the competing reaction 22 Ne(α,γ ) 26 Mg have a significant effect on heavy-element production [5][6][7]. The critical-temperature region of this reaction in the s-process sites described above is approximately 0.3 GK.…”

“…It was proposed [2] that the 22 Ne(α,n) 25 Mg reaction could be a suitable mechanism for neutron production. In stellar environments, 22 Ne can be produced by the reaction chain 14 N(α,γ ) 18 F(β + ) 18 O(α,γ ) 22 Ne where 14 N is one of the main products of the CNO cycle. Using the temperature and density requirements necessary for α capture onto 22 Ne, two astrophysical sites have been proposed for the s-process.…”

“…In stellar environments, 22 Ne can be produced by the reaction chain 14 N(α,γ ) 18 F(β + ) 18 O(α,γ ) 22 Ne where 14 N is one of the main products of the CNO cycle. Using the temperature and density requirements necessary for α capture onto 22 Ne, two astrophysical sites have been proposed for the s-process. Light s-process elements (∼50 > A > ∼100) are thought to be created in massive stars (M > ∼10 M ) during their core helium burning phase [3].…”

The6Li(22Ne,26Mg)d α-transfer experiment for the study of low-energy resonances in22Ne(α,γ)26Mg

“…The reaction also acts as a secondary neutron source during the s process in low-mass asymptotic giant branch (AGB) stars during which roughly half the abundances of nuclides in the A=90-209 range are thought to be synthesized [2]. A variety of attempts to experimentally determine the rate for this reaction at the Gamow window corresponding to s process temperatures (T = 0.2-0.3 GK) have been made either through direct 22 Ne(α,n) 25 Mg measurements [e.g., [3][4][5][6] or indirectly via 26 Mg(γ,n) 25 Mg [7], 25 Mg(n,γ) 26 Mg [8], 26 Mg(γ,γ') 26 Mg [9], 26 Mg(p,p'γ) 26 Mg [10], and 22 Ne( 6 Li,d) 26 Mg reactions [11,12]. However, direct measurements have been hindered by the small cross section due to the Coulomb barrier and the resonances at E α < 830 keV have not been identified with this method.…”