Persistent Spectral Hole-Burning in the Absorption Spectra of Porphyrin Derivatives without C₂ Symmetry Vertical to Molecular Plane

Abstract

NTT Opto-Electronics Laboratories; Tokai-mura, N a ka-gun, I b a r a ki-ken 319-11 Japan In order to secure the storage density of PSHB memory by avoiding the las e r induced hole filling, we have investigated the hole-burning characteristics of a poly(methyl met h a c rylate)(PMMA) doped with chlorine derivatives that are less symmetric than tetraph e n y lporphyrin.
The absorption spectra of chlorin e6 trimethyl ester (Che₆TME) doped PMMA before and after hole-burning did not overlap. Since laser induced hole filling only occurs when t h e spectra overlap, it can be avoided by using Che6TME/PMMA. We found that the use of dye molecules without C₂ axis perpendicular to molecular plane, such as Che₆TME, ca n prevent laser induced hole filling which is enebitable in C₂ symmetric H₂ porphyrin derivatives.
Also in the systems we used here, we found that the energy transfer between guest molecules is negligible only at concentrations of less than 10-3 M. From fluorescence lifetime and other measurements, we have also noticed that decay processes as lfuore scence, internal conversion and inter system crossing compete with PSHB.