Comment on "Structure effects in the $^{15}$N(n,$\gamma$)$^{16}$N radiative capture reaction from the Coulomb dissociation of $^{16}$N"

TL;DR

This paper critiques a recent study claiming Coulomb dissociation can determine the $^{15}$N(n,$ extgamma$)$^{16}$N cross section, arguing that it cannot due to the dominance of excited state branchings not accessible in Coulomb dissociation.

Contribution

It clarifies that Coulomb dissociation experiments are insufficient to constrain the capture cross section because of the complex branching ratios and provides a critical comparison with direct capture model predictions.

Findings

Coulomb dissociation cannot constrain the capture cross section due to excited state dominance.

The predicted ground state branching ratio is much lower than direct capture models.

The energy dependence of the branching ratio deviates from expectations for p-wave capture.

Abstract

In their recent study Neelam, Shubhchintak, and Chatterjee have claimed that "it would certainly be useful to perform a Coulomb dissociation experiment to find the low energy capture cross section for the reaction" $^{15}$N(n,$\gamma$)$^{16}$N. However, it is obvious that a Coulomb dissociation experiment cannot constrain this capture cross section because the dominating branchings of the capture reaction lead to excited states in $^{16}$N which do not contribute in a Coulomb dissociation experiment. An estimate of the total $^{15}$N(n,$\gamma$)$^{16}$N cross section from Coulomb dissociation of $^{16}$N requires a precise knowledge of the $\gamma$-ray branchings in the capture reaction. Surprisingly, the calculation of Neelam, Shubhchintak, and Chatterjee predicts a strongly energy-dependent ground state branching of the order of 0.05\% to 0.6\% at energies between 100 and 500 keV which is almost 2 orders of magnitude below calculations in the direct capture model. Additionally, this calculation of Neelam, Shubhchintak, and Chatterjee deviates significantly from the expected energy dependence for $p$-wave capture.