Statistical Fine Structure of Inhomogeneously Broadened Absorption Lines

Abstract

Using laser frequency-modulation spectroscopy, we have observed statistical fine structure (SFS) in the inhomogeneously broadened optical absorption of pentacene in $p$-terphenyl at liquid-helium temperatures. SFS is time-independent structure on the inhomogeneous line profile caused by statistical variations in the spectral density of absorbers in each frequency interval. The size of the SFS varies as the square root of the number of centers, and the autocorrelation of the SFS yields an estimate of the homogeneous linewidth without the requirement of spectral hole burning or coherent transients.