1. Contributions from the Department of Chemistry, Vanderbilt University, 7330 Stevenson Center, Station B 351822, Nashville, Tennessee 37235-1822, Vanderbilt Interdisciplinary Program in Materials Science, 2301 Vanderbilt Place, VU Station B 350106, Nashville, Tennessee 37235-0106, and Department of Physics and Astronomy, Vanderbilt University, 6301 Stevenson Center, 1807 Station B, Nashville, Tennessee 37235-1807