Electron–phonon coupling in amorphous organic host materials as investigated by photochemical hole burning

Abstract

The absorption line shapes of photochemical holes of quinizarin in alcohol glasses have been investigated and special attention is given to a detailed analysis of the experimentally observed, intense phonon sidebands at the low energy side of the zero phonon hole. An analytical expression for the shape of these photochemical holes was derived which can be integrated for short burning times. Computer modeling was performed to describe the line shape function in both the short and long burning time limit. These calculations show that there are two contributions to the observed phonon sidebands: One which is due to phonon induced photochemistry and has its maximum on the low energy side of the zero phonon hole and one which is due to zero phonon photochemistry at the laser frequency and has its maximum on the high energy side. It is shown that the various line shape contributions to the photochemical hole have a different burning time behavior. A remarkable feature is that the low energy ’’pseudo-phonon wing’’ dominates the direct phonon wing under all experimentally achievable conditions.