PHOTOCHEMICAL HOLE BURNING (PHB) OF TETRAPHENYLPORPHIN IN POLY(ETHYLENE-TEREPHTHALATE)

The efficiency of hole formation, PHI, the energy difference between a zero-phonon hole peak and a pseudo-side hole peak, E(s), and the thermal stability of holes burnt at 4.2 K with a 0.1-2.0 mW cm-2 Ar+-laser-pumped ring dye laser at about 647 nm were studied for tetraphenylporphin (TPP) in poly(ethylene terephthalate) (PET) films. The value of PHI was 5.4 x 10(-4) and 6.2 x 10(-4) for TPP in undrawn and five-times drawn PET film, respectively, while the annealing of the drawn film at 220-degrees-C resulted in a marked decrease in PHI probably due to the aggregation of TPP molecules. The phonon frequency measured as E(s) from the hole profiles of TPP in PET films was about 11-12 cm-1 (similar to the E(s) for polystyrene), and a small increase in E(s) was observed by five-times drawing the PET film, reflecting the increased order in the amorphous region of the PET film. The thermal stability of holes burnt at 4.2 K measured with hole recovery at 4.2 K after cyclic standing of the sample at 30, 50 and 80 K was markedly improved by the five-fold drawing of the PET film. The structural relaxation process affecting the spectral diffusion of PHB holes seemed to be of very local character in the vicinity of PHB molecules in the amorphous region of PET films.