Schematic Diagram (IMAGE) National Institute for Materials Science, Japan Caption (A) proton tunneling through the barrier (quantum). (B) proton transfer via the transition state (classical); In the electrochemical system the relative contribution of the two mechanisms can be tuned by the applied potential. Credit NIMS Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.