Abstract
The lineshapes of spectroscopic transitions offer windows into the local environment of a system. Here, we present a novel approach for connecting the lineshape of a molecular exciton to finite-temperature lattice vibrations. Our results are based upon an exact, self-consistent treatment of a continuous model in which thermal effects are introduced as fluctuations about the zero-temperature localized soliton state. Two parameters enter our model: the exciton band-width \((J)\) and the exciton reorganization energy \(\mu\). Our model bridges the strongly localized limit where the exciton homogeneous line width is observed to be independent of temperature and the molecular aggregate limit in which the line width increases linearly in temperature.