Knowledge Bank

One-colour resonance enhanced two-photon ionisation (1C-R2PI) spectroscopy has been used to measure the $S1-S0$ electronic spectra of the $-Ar1$ and $-Ar2$ van der Waals clusters of ortho- and meta- difluorobenzene (DFB). The vibrational structure near the $S1-S0$ origin band of the cluster species yields information concerning the van der Waals vibrational motion. Rotational band contours measured for several of these transitions for the $-Ar1$ and $-Ar2$ complexes assist in establishing the cluster geometries. A simple model for the van der Waals motion serves to rationalise our observations. The vibrational predissociation dynamics of the $-Ar1$ clusters have also been examined using dispersed fluorescence spectroscopy.