Formation times of anthracene (hatched) and pyrene (gray) dimers for the northern equatorial belt considering initial mole fraction in the 2 × 10^-11 − 2 × 10^-9 interval. The calculations are performed for altitudes for which the association is faster than dissociation for the same range of initial mole fractions. The lines represent the photo-evaporation times for anthracene (solid red line) and pyrene (dotted blue line) dimers.