1. Laboratory for Molecular Interfacial Interactions, Code 6920, Center for Bio/Molecular Science and Engineering, Naval Research Laboratory, Washington, D.C. 20375, Chemistry Division, Code 6120, Naval Research Laboratory, Washington, D.C. 20375, Physical Sciences S&T Division, Office of Naval Research, 800 N. Quincy Street, Arlington, Virginia 22217, and Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831