Statistical fine structure in the inhomogeneously broadened electronic origin of pentacene in p-terphenyl

Abstract

Recently, the first observation of statistical fine structure on an inhomogeneously broadened absorption profile was reported [W. E. Moerner and T. P. Carter, Phys. Rev. Lett. 5 9, 2705 (1987)] for mixed crystals of pentacene in p‐terphenyl using laser frequency‐modulation spectroscopy. Statistical fine structure is time‐independent structure on the inhomogeneous line caused by statistical variations in the spectral density of absorbers in each frequency interval. In this work, a model and an analysis of statistical fine structure using autocorrelation techniques are presented, and the dependence of the effect for pentacene in p‐terphenyl at 1.4 K on modulating frequency, detection phase, center concentration, and position in the sample is described. Statistical fine structure provides a new method for probing inhomogeneous systems that allows investigation of the underlying probability distribution function and the determination of the homogeneous linewidth. This fine structure also represents a fundamental limit on the detectability of shallow spectral features in inhomogeneously broadened lines.