(a) Calculated first-order rates for conversion of HF to AlF by reaction with Al, AlOH and AlO; and loss of AlF by photolysis and reaction with H, H₂O and OH. The clustering rate with metallic compounds (blue line, see text for further details) is shown in the region where the temperature is below 500 K. (b) Calculated first-order rates for conversion of HCl to AlCl by reaction with Al, AlOH and AlO; and loss of AlCl by photolysis and reaction with H, H₂O and OH. The red lines show the molecular expansion rate of the outflow at a constant velocity of 16.5 km s⁻¹.