Observed column densities of C₃ (filled symbols) and C₂ (open symbols) versus projected nucleocentric distance for comet Hale-Bopp on Dec. 19/20, 1997, according to H05. Solid black lines show the best fits obtained in his work, using the reaction network of H05. The dashed line shows the C₂ and C₃ column density profiles for a C₂H₆ production rate that has been raised by a factor of 10 relative to the best-fit result, the dashed-dotted line for an increase by a factor of 100 (for a change by a factor of 10 no difference can be seen for C₃). The red lines are the corresponding column density profiles obtained for the production rates of H05.