Radial profiles of gaseous fractional abundances of H₂O, O₂, O, and OH in NGC 1333-IRAS 4A envelope models. These profiles are obtained from our test calculations assuming the smaller E_des(j) for atomic oxygen (=800 K) rather than that in our fiducial model (= 1660 K). In the top left panel the observational best-fit H₂O gas abundance profile obtained in van Dishoeck et al. (2021) is overplotted with the black solid line (see also Figs. 10 and H.1). In the top right panel the three model O₂ gas abundance profiles obtained in Yıldız et al. (2013) are overplotted (see also Figs. 10 and H.1).