  Brown & Mallik 2008 and the Brown et al. 2010 corrigendum of it presented
expressions for non-thermal recombination (NTR) in the collisionally thin- and
thick-target regimes, claiming that the process could account for a substantial
part of hard X-ray continuum in solar flares usually attributed entirely to
thermal and non-thermal bremsstrahlung (NTB). However, we have found the
thick-target expression to become unphysical for low cut-offs in the injected
electron energy spectrum. We trace this to an error in the derivation, derive a
corrected version which is real-valued and continuous for all photon energies
and cut-offs, and show that, for thick targets, Brown et al. over-estimated NTR
emission at small photon energies. The regime of small cut-offs and large
spectral indices involve large (reducing) correction factors but in some other
thick-target parameter regimes NTR/NTB can still be of order unity. We comment
on the importance of these results to flare and to microflare modeling and
spectral fitting. An empirical fit to our results shows that the peak NTR
contribution comprises over half the hard X-ray signal if delta > 6 (E_0c/4
keV)^(0.4).
