Biomolecular recombination and reciprocity in xerographic photoconductors

An analytic solution for the residual charge on a xerographic photoconductor after flash exposure is made possible by reformulating the recombination equations in terms of local ordering of events. The residual charge R is found to depend only on the applied surface charge, the field dependence of recombination and the initial photogenerated charge. For the Langevin recombination cross-section, R=D 0 exp - beta , where D 0 is the surface charge and beta D 0 is the photogenerated charge. It is demonstrated that an identical response at long and short exposures is sufficient to ensure universal reciprocity.