A theory of diffusion-influenced geminate and pseudo-first-order bulk
reactions on fractal structures is presented within the Smoluchowski f
ramework. The formalism is based on the solution of the backward equat
ion for the pair survival probability, generalized to noninteger dimen
sionality using the effective potential approximation. Possible anomal
ous diffusion is taken into account by assuming a new time variable, e
nsuring linear asymptotics of the mean-squared displacement. The resul
ts for both absorbing and radiation inner boundary conditions are deri
ved for noninteracting reactants and compared with those well known fo
r integer dimensions. The asymptotic analysis for arbitrary potential
is also carried out.