Comment on "Collision strength and effective collision strength for Ba~XLVIII" by Mohan et al. [Can. J. Phys. 95 (2017) 173]

Abstract

In a recent paper, Mohan et al. [Can. J. Phys. {\bf 95} (2017) 173] have reported results for collision strengths ($\Omega$) and effective collision strengths ($\Upsilon$) for transitions from the ground to higher 51 excited levels of F-like Ba~XLVIII. For the calculations of $\Omega$, the Dirac atomic $R$-matrix code (DARC) and the flexible atomic code (FAC) have been adopted, in order to facilitate a direct comparison. However, for the subsequent calculations of $\Upsilon$, DARC alone has been employed. In this comment, we demonstrate that while their limited results for $\Omega$ are comparatively reliable, for $\Upsilon$ are not, particularly for the allowed transitions and at lower temperatures. Apart from the non expected behaviour, their $\Upsilon$ values are overestimated for several transitions, by about a factor of two.