Measurement of the ${}^{25}\mathrm{Al}(d,n){}^{26}\mathrm{Si}$ reaction and impact on the ${}^{25}\mathrm{Al}(p,\gamma ){}^{26}\mathrm{Si}$ reaction rate

The ${}^{25}\mathrm{Al}(p,\gamma ){}^{26}\mathrm{Si}$ reaction is part of a reaction network with impact on the observed galactic ${}^{26}\mathrm{Al}$ abundance. A new determination of the proton strength of the lowest $\ell =0$ proton resonance in ${}^{26}\mathrm{Si}$ is required to more precisely calculate the thermal reaction rate. To this end, the ${}^{25}\mathrm{Al}(d,n){}^{26}\mathrm{Si}$ proton-transfer reaction is measured in inverse kinematics using an in-flight radioactive beam at the RESOLUT facility. Excitation energies of the lowest ${}^{26}\mathrm{Si}$ proton resonances are measured and cross sections are determined for the lowest $\ell =0$ resonance associated with the $3_3^{+}$ state at 5.92(2) MeV. Coupled reaction channels calculations using fresco are performed to extract the $\ell =0$ spectroscopic factor for the $3_3^{+}$ state. The proton width for the $3_3^{+}$ state in ${}^{26}\mathrm{Si}$ is determined to be ${\mathrm{\Gamma }}_p=2.19\left(45\right)$ eV and the $(p,\gamma )$ resonance strength for the $3_3^{+}$ state is extracted as 0.026(10) eV. This resonance dominates the ${}^{25}\mathrm{Al}(p,\gamma ){}^{26}\mathrm{Si}$ reaction rate above 0.2 GK.

Figure 1

Secondary beam composition measured in the gas ionization chamber. Particles are identified through the correlation between the energy loss measured in the 80 mm region ($y$ axis) and the residual energy deposited in the 200 mm region ($x$ axis) of the ion chamber.

Figure 2

Schematic representation of the experimental setup including the target ladder, silicon telescope and position sensitive ion chamber.

Figure 3

Excitation energy spectrum of ${}^{26}\mathrm{Si}$. The secondary $x$ axis represents the associated center-of-mass proton resonance energies. The state of interest for astrophysical environments is the $3_3^{+}$ at 5.92 MeV.

Figure 4

(a) Correlation between the ${}^{25}\mathrm{Al}+p$ sum-energy and neutron-emission angle extracted from the Monte Carlo simulation based on the ($d,n$) angular distribution from CRC theory (see text). (b) The 5.92 MeV $3_3^{+}$ experimental ${}^{25}\mathrm{Al}+p$ sum-energy distribution compared to the results of the Monte Carlo simulation. Shown for comparison is the experimental and simulated ${}^{25}\mathrm{Al}$ beam energy profile.

Figure 5

Reaction cross sections from the CRC calculation (see text) in relation to the $C^2{S}_{l=0}$ spectroscopic factor. The values and error limits for the experimental cross section and the mirror-nucleus spectroscopic factors by Hamill et al. [18] are marked. The blue line represents the cross section calculated while scaling the $C^2{S}_{l=0}$ and $C^2{S}_{l=2}$ proportionally.

Figure 6

Thermal rate for the ${}^{25}\mathrm{Al}(p,\gamma ){}^{26}\mathrm{Si}$ reaction. The total rate is separated into direct capture (gold) and three individual resonance contributions, $1_1^{+}$ (red), $0_4^{+}$ (light blue), and $3_3^{+}$ (dark blue).

Figure 7

Ratio of reaction rates for different rates reported in JINA's REACLIB database [37] relative to the current work.