Left panel: density (red) and temperature (blue) structure in the IRAS16293 source model in stages 1 and 2 (see Sect. 5 for details). Middle panel: modeled beam-convolved molecular column densities (solid lines, labeled in the plot) as functions of time in stage 2. Dashed lines represent the observed values, omitting error bars for clarity. Right panel: modeled D/H ratios (solid lines, labeled in the plot) as functions of time in stage 2. Here, the NH₂ and ND₂ abundances have been summed over the ortho and para forms. Dashed lines represent the observed values, for which the error bars have again been omitted.