Photochemical Hole Burning and Debye-Waller Factor in Polyvinylalcohol doped with Ionic Porphyrins

Photochemical holes can be burned at relatively high temperatures in the Qx band of a free base porphyrin with ionic substituents when the molecule is dispersed in polyvinylalcohol (PVA) [1-2]. This characteristics of the porphyrin-PVA system is due to the facts that the Debye-Waller factor is relatively large [3] and the thermally activated backward reaction is small [4], Figure 1(a) shows one of such porphyrin molecules, TCPP(Na). The large Debye-Waller factor in porphyrin-PVA system is a direct consequence of a high mean phonon frequency. The typical phonon energy of the porphyrin-PVA system, which was determined as the energy deference between the zero-phonon hole and the bottom of the side hole, is as large as 25 cm–1. According to ref. 3, the Debye-Waller factor f(T) of porphyrin-PVA system is well represented by one-phonon approximation.