|Excited-state dynamics which occur in van der Waals clusters of aromatic molecules are briefly summarized in the first part of this seminar. Typical examples are the charge transfer reactions in electron donor-acceptor systems and excimer formation in homogeneous clusters of aromatic molecules. It is demonstrated that these excited-state reactions are strongly dependent on the excitation energy and cluster size, which are explained by geometry-controlled processes.
The second part is concerned with the structures and excited-state dynamics of the DNA bases and their hydrated clusters in the gas phase. The laser desorption method which we have developed to produce these species under isolated conditions is introduced. By employing this technique combined with the supersonic jet spectroscopy, we have examined the tautomerization, base pairing, and hydration behavior of guanines and adenines.