I. INTRODUCTION Carboxylic dimers, linked by two hydrogen bonds, are model systems for the study of the potential function and the dynamics of protons involved in hydrogen bonds. There exist two distinct tautomer forms, separated by a poten— ttwihaoell plborwaortrotineemr,tpreawrnhastifucehrre inabtleoernhcgaovnitovhueerrthybdyrsougacehncosnybcsoetnretdmesd.s, characterized by the condition that thermally activated barrier crossing no longer dominates the interconversion process, is of particular interest regarding the transition to quantum transport by tunneling. Tunneling tends to delocalize the protons over the two potential wells. A condensed phase environment, on the other hand, differentiates the two wells and tends to localize the protons such that at low temperatures only the most stable tautomer form exists. We have shown 1,2 that the optical spectra of dyes are sensitive to the proton structure of the environment and can be used to access the dynamics of these systems at very low temperatures (see Fig.l). For example, measurements of the fluorescence de— cay following site specific excitation yielded *This research was supported by a grant from the Division of Materials Research (DMR-85-O774O) and by the United States Army Research Office (Durham);
