Solvation and vibrational effects on proton tunnelling in clusters

Abstract

Recent experiments indicate that excited-state proton transfer in ROH(NH₃)_n clusters (where ROH is 1-naphthol or phenol) occurs by a tunnelling mechanism. A theoretical framework for describing the role of solvent and vibrations on proton tunnelling rates is discussed. Two previous models of proton tunnelling in clusters are examined; one based on a solvent-independent bound–continuum potential and the other on a solvent-activated bound–bound potential. In this work we extend the latter model to incorporate coupling of the proton to reactant and product vibrations. All three models are compared to experimental tunnelling rates in clusters and their attributes discussed.