Inhomogeneous broadening of electronic spectra at liquid interfaces

Molecular dynamics simulations of the electronic spectrum of a chromophore at the liquid/vapor interface of a non-polar solvent are used to investigate the factors that contribute to the spectral linewidth in the limit of inhomogeneous broadening. The interface spectra are broader than in the bulk due to an increase in heterogeneity on the scale of a single solvation shell and, to a greater degree, due to the spectral shift across the entire interface region. Insight into the broadening mechanism is obtained by considering the temperature effect and by calculating the spectra in layers defined both relative to the simulation box and relative to the intrinsic interface.