Mode Specific Vibrational Predissociation Dynamics in Fragile Molecules

State resolved vibrational dynamics in weakly bound complexes is investigated via high resolution IR absorption spectroscopy in a slit supersonic jet expansion. The tunable frequency near IR source can readily excite the high frequency intramolecular vibrations of the subunits, as well as the low frequency, intermolecular vibrations via combination band excitations built on the high frequency modes. These upper state energies lie far above the van der Waals binding energy limit, and yet predissociate typically on the nsec time scale or longer (i.e. many millions of vibrational periods). This exceptional metastability in such small systems is highly non-statistical, and proves to be a rich arena of vibrational mode mixing and mode-specific predissociation behavior. We select recent examples from our group effort to illustrate these concepts.