Asymmetric line shapes of localized optical excitations in condensed systems

Publisher Website
Google Scholar
Abstract
The configuration coordinate model is a useful approximation for describing localized excitations (absorption and emission) in condensed systems. It is frequently applied assuming Gaussian peaks. At ordinary temperatures there are two causes of asymmetric peaks. The problem of small relative displacement along the configuration coordinate has been discussed at length. It results in a high‐energy tail on the absorption peak mirrored by a low‐energy tail for emission. For a number of systems where the relative displacement qo along the configuration coordinate is large, asymmetries are observed which do not fit the above pattern. Jacobs and Thorsley have discussed this case in some detail. It is, however, difficult to use their equations directly to extract configuration coordinate parameters from experimentaly data. Experimentally observed absorption or emission peaks can be fit by a log‐normal distribution function which establishes two parameters, b and E1/2. By an extensive series of numerical calculations based on their equations, we have developed a series of simple equations relating b and E1/2 and configuration coordinate parameters. We present these relationships and discuss briefly their application.