Radial profiles of gaseous fractional abundances of H₂O, O₂, O, OH, HCO⁺, and CH₃OH in the NGC 1333-IRAS 4A envelope models, with X-ray luminosities between L_X = 10³⁰ and 10³¹ erg s⁻¹. The line color gradually changes from yellow to orange, red, and brown as the value of L_X increases. In the top left panel, the observational best-fit H₂O gas abundance profile obtained in van Dishoeck et al. (2021) is overplotted; in the top right panel, the three model O₂ gas abundance profiles obtained in Yıldız et al. (2013) are overplotted (see Fig. 10).