Effect of pseudo-phonon side hole in laser-induced hole filling

Multiple hole-burning processes have been studied in a photon-gated donor-acceptor electron-transfer system. Zinc-tetraphenylbenzoporphyrin (Zn-TPBP) and zinc-tetraphenyl(4-phenyl-acetylamino)benzotribenzobenzoporphyrin (Zn-TPBTP) were used together as the electron donors, while phydroxybenzaldhyde (PHBA) was the electron acceptor, and they are doped in the matrix poly(methyl)methacrylate (PMMA). It is more effective to form multiple holes from the shorter wavelength side to the longer side in such a system than the other way round. This wavelength-dependent phenomenon of laser-induced hole filling is mainly due to the effect of the pseudo-phonon side band, which leads to a smaller absorption loss at the zero-phonon holes previously burned, but to a larger absorption loss in the region that was not previously burned. Then, the previously burned holes, especially those holes located at the longer wavelength side of the new burning hole, seem to be filled. A theoretical simulation based on this assumption shows fairly good agreement with the experimental results.