Knowledge Bank

Helium Cluster Isolation Spectroscopy as a method of investigating molecular aggregates offers the advantages of extremely low temperatures (0.37 K), control of aggregation, and very weak solvent perturbation effects. Perylene, a molecule comprised of five benzene rings, is a model compound to study the effect of molecular aggregation (e.g., excitation transfer and proximity effects) in a class of molecules which have been frequently investigated in the solid state and in thin films. So far we have measured the monomer spectrum, resolving its vibronic structure up to $1500cm-1$ in the $S1$ electronic state. The average shift of the bands is approximately $+47cm-1$ while their zero phonon lines vary in both width and structure, the former reaching values as low as several GHz. We are presently searching for the dimer spectrum.