Determination of the $^{36}$Mg($n,\gamma$)$^{37}$Mg reaction rate from Coulomb dissociation of $^{37}$Mg

TL;DR

This study calculates the $^{36}$Mg(n,γ)$^{37}$Mg reaction rate using Coulomb dissociation data and extended theoretical models, showing it dominates over competing processes at relevant astrophysical temperatures.

Contribution

The paper introduces a method to determine the $^{36}$Mg(n,γ)$^{37}$Mg reaction rate from Coulomb dissociation data, including projectile deformation effects, providing new insights into astrophysical nucleosynthesis.

Findings

The $^{36}$Mg(n,γ)$^{37}$Mg reaction rate exceeds the $^{36}$Mg(α,n)$^{39}$Si rate up to T_9=1.0.

Projectile deformation effects increase the ($n, ext{γ}$) reaction rate.

The ($n, ext{γ}$) process likely dominates the $r$-process flow at $^{36}$Mg.

Abstract

We use the Coulomb dissociation (CD) method to calculate the rate of the $^{36}$Mg(${n,\gamma}$)$^{37}$Mg radiative capture reaction. The CD cross sections of the $^{37}$Mg nucleus on a $^{208}$Pb target at the beam energy of 244 MeV/nucleon, for which new experimental data have recently become available, were calculated within the framework of a finite range distorted wave Born approximation theory that is extended to include the projectile deformation effects. Invoking the principle of detailed balance, these cross sections are used to determine the excitation function and subsequently the rate of the $^{36}$Mg($n,\gamma$)$^{37}$Mg reaction. We compare these rates to those of the $^{36}$Mg($\alpha,n$)$^{39}$Si reaction calculated within a Hauser-Feshbach model. We find that for $T_9$ as large as up to 1.0 (in units of 10$^9$ K) the $^{36}$Mg($n,\gamma$)$^{37}$Mg reaction is much faster than the $^{36}$Mg($\alpha,n$)$^{39}$Si one. The inclusion of the effects of $^{37}$Mg projectile deformation in the breakup calculations, enhances the ($n,\gamma$) reaction rate even further. Therefore, it is highly unlikely that the $(n,\gamma)$ $\beta$-decay $r$-process flow will be broken at the $^{36}$Mg isotope by the $\alpha$-process.