Production of 26Al in stellar hydrogen-burning environments: spectroscopic properties of states in 27Si

TL;DR

This study refines the spectroscopic properties of states in 27Si near the proton threshold, crucial for modeling 26Al production in stars, by using a high-resolution transfer reaction to constrain their energies and spin-parities.

Contribution

First transfer reaction measurement to determine Jπ values of 27Si states near 7-8 MeV, improving nuclear data for astrophysical reaction rate calculations.

Findings

Confirmed energies and spin-parities of 27Si states with high precision.

Provided experimental neutron spectroscopic factors aligning with shell-model predictions.

Enhanced understanding of nuclear states relevant for stellar nucleosynthesis.

Abstract

Model predictions of the amount of the radioisotope 26Al produced in hydrogen-burning environments require reliable estimates of the thermonuclear rates for the 26gAl(p,{\gamma})27Si and 26mAl(p,{\gamma})27Si reactions. These rates depend upon the spectroscopic properties of states in 27Si within about 1 MeV of the 26gAl+p threshold (Sp = 7463 keV). We have studied the 28Si(3He,{\alpha})27Si reaction at 25 MeV using a high-resolution quadrupole-dipole-dipole-dipole magnetic spectrograph. For the first time with a transfer reaction, we have constrained J{\pi} values for states in 27Si over Ex = 7.0 - 8.1 MeV through angular distribution measurements. Aside from a few important cases, we generally confirm the energies and spin-parity assignments reported in a recent {\gamma}-ray spectroscopy study. The magnitudes of neutron spectroscopic factors determined from shell-model calculations are in reasonable agreement with our experimental values extracted using this reaction.