Structure, dynamics, and the electronic absorption of benzene–argon clusters

We present a new method for calculating cluster absorption spectra using classical molecular dynamics and simulated annealing techniques. We then apply this method to benzene–Ar clusters. Cluster absorption spectra are shown to be dominated by an inhomogeneous distribution of isomer absorptions. The absorption spectrum of each isomer, however, results from the interplay of structure, fluctuations, and dynamics. We find that accompanying the solid to liquid transition, there is a spectroscopic transition from a periodic to a decaying autocorrelation function of the electronic energy gap. Benzene–Ar clusters are found to undergo transitions from a solid to a 2D liquid to a 3D liquid as the number of Ar atoms is increased from 1 to 21 at 20 K.