“…Such calibrations of NaI(Tl) scintillators are usually assumed to mean that q does not depend on the energy of the recoil ion E r (i.e., ∂q/∂E r = 0, see Refs. 7,12). Actually, while this conclusion does not follow from anything else, it is buttressed by the observation that the light energy yield of an inorganic scintillator (for NaI(Tl) it amounts to about 15% 1 ) depends only weakly on electron energy, varying by less than 20% from 5 to 1000 keV, 1,13,14 just as the light energy yield for heavy particles with E > 1 MeV.…”