  Inhomogeneous broadening is well known to hinder individual characteristics
of emitters, supplanting the single-particle properties by their broader
probability distribution. Here, we present an analysis of the emission spectra
of mesoscopic ensembles of inhomogeneously distributed emitters below the
thermodynamic limit (10 - 10^4 emitters). Based on a simple analytical model
and an extensive numerical analysis, we show that the number and individual
linewidths of the emitters can be directly estimated from the ensemble
autocorrelation function in spite of an inhomogeneously broadened emission. As
an application, we analyze the photoluminescence of colloidal nanocrystal
aggregates embedded in a gold shell. Our general method can be applied to a
wide range of mesoscopic many-body systems and could provide new insights into
their first-order coherence properties.
