Comment on “Collision strength and effective collision strength for Br XXVII” by Goyal et al. [Can. J. Phys. 95, 1127 (2017)]

Abstract

In a recent paper, Goyal et al. [Can. J. Phys. 95 (2017) 1127] have reported results for collision strengths (Ω) and effective collision strengths (Υ) for transitions among the lowest 52 levels of F-like Br XXVII. For their calculations, they have adopted the Dirac atomic R-matrix code (DARC) and the flexible atomic code (FAC). In this comment we demonstrate that their results for both parameters are erratic, inaccurate, and unreliable.

Comment on “Electron impact excitation and ionization cross section of tungsten ions, W44+” by El-Maaref et al. [J. Quant. Spectrosc. Radiat. Transfer 2019, 224:147]

“…Results of [1] have been multiplied by a factor of ten. of their calculation is very (very) limited and does not even cover the entire thresholds region, (ii) their energy mesh to resolve resonances (0.02 Ryd) is very coarse and will result in overestimation of Υ (see [9] and [10]), a parameter obtained after integration over an electron velocity distribution function, mostly Maxwellian, and required in the analysis or modelling of plasmas (see section 4), and (iii) the results being available for only 49 transitions among the possible 3321 belonging to the 82 levels considered by them, i.e. <1.5%.…”

Radiative rates for E1, E2, M1, and M2 transitions in F-like ions with55≤Z≤73

“…Since such a large difference between any two codes is generally neither noted nor expected, one of the two calculations is actually not correct, as explained in our paper [21]. Therefore, comparison of results with two different codes is only beneficial when both calculations have been performed with great care.…”