A re-evaluation is made of the k0-factor and related nuclear data for the 555.8 keV gamma-ray of the 104mRh-104Rh mother-daughter pair that are important in neutron activation analysis (NAA). This study considers that the relevant level is also fed by the 4.34 min 104mRh mother (with an absolute gamma-ray emission probability γ2=0.13%) and not only, as assumed in former work, by the 42.3 s 104Rh daughter isotope (with γ3=2.0%). In view of this, generalised equations were developed for both the experimental determination and the analytical use of the k0-factor and of the associated parameters k0(m)/k0(g), Q0(m) and Q0(g) [(m):104mRh; (g): 104Rh], requiring the introduction of the γ2 and γ3 data and also of the 104mRh→104Rh fractional decay factor F2(=0.9987). The experimental determinations were based on irradiations performed in the BR1 reactor in Mol and the WWR-M reactor in Budapest. Furthermore, considering the special formation of the 555.8 keV gamma-ray, the procedure for true-coincidence correction was revised as well. All this led to the compilation and recommendation of a new set of 'k0-NAA' data. Copyright (C) 1999 Elsevier Science Ltd.
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