Abstract

Ultrafast studies of molecular relaxation in the bulk have been of great value in revealing the dynamics of fundamental chemical and physical events. However, our knowledge of these processes at interfaces is still in its infancy. The present contribution focuses on the interfacial nature of one of the simplest chemical reactions; molecular isomerization. The interface is a unique environment, of interest in its own right, providing a further test of our understanding of elementary molecular processes. Time resolved second harmonic generation, by avoiding the complications of bulk contributions, enables surface species to be probed directly and on an ultrafast timescale¹,² Our results on the barrierless isomerization of an organic dye indicate novel and unanticipated behavior: a very large change in relaxation rates, differing by an order of magnitude from those in the bulk and surprisingly similar rates at very different interfaces, namely the air/liquid, liquid/liquid and liquid/solid interfaces.

© 1994 Optical Society of America