Two-neutron excitations in 26Mg and 30Si

Structure of resonances in the Gamow burning window for theAl25(p,γ)Si26reaction in nov

“…For example, the 30 P(p,γ) 31 S reaction rate needs to be known more precisely to understand the abundances of elements up to Ca in novae ejecta and the 28 Si/ 30 Si abundance ratio in meteoritic inclusions [2]. The 25 Al(p,γ) 26 Si reaction is also important to constrain since it influences the abundance of the cosmic γ-ray emitter 26 Al (t 1/2 = 7.2 x 10 5 yr) injected into the interstellar medium [3]. Most 26 Al material is currently thought to be associated with Wolf-Rayet stars and their subsequent explosions in core collapse supernovae [4].…”

“…The 25 Al(p,γ) 26 Si reaction is also important to constrain since it influences the abundance of the cosmic γ-ray emitter 26 Al (t 1/2 = 7.2 x 10 5 yr) injected into the interstellar medium [3]. Most 26 Al material is currently thought to be associated with Wolf-Rayet stars and their subsequent explosions in core collapse supernovae [4]. However, the high abundances of 26 Al observed relative to 60 Fe, when compared to core collapse supernovae model predictions, suggest that there could be a significant additional contribution from novae [5,6].…”

“…Most 26 Al material is currently thought to be associated with Wolf-Rayet stars and their subsequent explosions in core collapse supernovae [4]. However, the high abundances of 26 Al observed relative to 60 Fe, when compared to core collapse supernovae model predictions, suggest that there could be a significant additional contribution from novae [5,6]. The burning regime in novae occurs at temperatures of ∼0.1-0.4 GK, where the reaction rate is expected to be dominated by resonant reactions on 1 + , 0 + and 3 + states predicted by sd-shell model calculations [7] to be located just above the proton threshold energy of 5513.7(5) keV in 26 Si [8].…”

“…However, the high abundances of 26 Al observed relative to 60 Fe, when compared to core collapse supernovae model predictions, suggest that there could be a significant additional contribution from novae [5,6]. The burning regime in novae occurs at temperatures of ∼0.1-0.4 GK, where the reaction rate is expected to be dominated by resonant reactions on 1 + , 0 + and 3 + states predicted by sd-shell model calculations [7] to be located just above the proton threshold energy of 5513.7(5) keV in 26 Si [8]. Considerable experimental efforts have gone into identifying and locating these resonant states [9][10][11][12][13][14][15][16][17][18][19][20].…”

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A γ-ray spectroscopy study of excited states in 26 Si has been performed using the 24 Mg( 3 He,n) reaction at a beam energy of 10 MeV. In particular, states have been studied above the proton threshold relevant for burning in the 25 Al(p,γ) 26 Si reaction in novae.

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