The effective optical path length, however, was found to be 5.3 ± 0.2 mm, notably larger than the geometric average path length of 2.0 mm. Employing this effective optical path length, an initial absorbed photon fraction of ~0.98 can be derived, intrinsically resulting from the close agreement between the experimentally determined minimum and simulated photon flux (Figure ). Absorption of the majority of photons gives a markedly enhanced conversion rate and, in comparison to the microcapillary reactor (Figure ), a lower fraction of photons transmitted. This further underscores the criticality of basing conclusions on accurate presumptions when interpreting data.