Identification of Key Astrophysical Resonances Relevant for theAl26g(p,γ)Si27

Abstract

A gamma-ray spectroscopy study of ;{26g}Al+p resonant states in 27Si is presented. Excitation energies were measured with improved precision and first spin-parity assignments made for excited states in 27Si above the proton threshold. The results indicate the presence of low-lying resonances with l_{p}=0 and l_{p}=2 captures that could strongly influence the ;{26g}Al(p,gamma)27Si reaction rate at low stellar temperatures, found in low-mass asymptotic giant branch (AGB), intermediate-mass AGB, super AGB, and Wolf-Rayet stars.

Simultaneous measurement ofβ-delayed proton andγdecay ofP27

“…A new partial-decay scheme for 27 P was created using the results of this study, combined with relevant information from Refs. [9,10], and can be seen in Fig. 7.…”

“…Previously observed γ rays from 27 Si [9,10] were identified in the β-delayed spectrum as well as several newly observed γ rays, which are shown in Fig. 6.…”

“…An experiment done at Argonne National Laboratory (ANL) using the ATLAS accelerator and the Gammasphere array [8] to investigate 27 Si provided information on important resonant energies for both 26 Al g (p,γ) 27 Si and 26 Al m (p,γ) 27 Si [9,10]. New levels in 27 Si were identified, energy values for previously observed levels were obtained with greater precision and spin and parity values for most levels were assigned.…”

“…New levels in 27 Si were identified, energy values for previously observed levels were obtained with greater precision and spin and parity values for most levels were assigned. Two resonant energies not observed in [9,10] due to spin and parity selection rules are 485 keV and 632 keV, relating to the 8176(3)-keV and 8318(3)-keV levels in 27 Si respectively. Both are tentatively assigned a (1/2 or 3/2) + value [7].…”

A new study of 25Mg $(\alpha, n)$ 28Si angular distributions at $E_{\alpha} =3-5$ MeV

“…This reaction has been precisely studied by the LUNA experiment [13] thanks to its underground location [14,15] 28 Si. The first reaction has been recently studied [16] while on the others there are still some discussions. Their impact on the 26 Al production during C/Ne explosive burning in massive stars has been recently studied and detailed comparisons between data and models have been performed finding strong discrepancies ( [17,18] and reference therein).…”