A time-resolved emission technique was employed to study the photoprotolytic cycle of two photoacids 2-naphtol-6-sulfonate (2N6S) and 2-naphtol-6,8-disulfonate (2N68DS) in ice in the presence of a low concentration of a weak base fluoride ion. We found that an additional proton-transfer process occurs in ice doped with F- ions. This reaction takes place between a mobile L-defect (created by static F- ions) and the photoacid. We used a diffusion assisted reaction model, based on the Debye-Smoluchowski equation, to account for the direct reaction of the L-defect with the excited photoacid.