-------------------------------------------------------------------- COLLOQUIUM OF THE COMPUTATIONAL MATERIALS SCIENCE CENTER AND THE SCHOOL OF PHYSICS, ASTRONOMY AND COMPUTATIONAL SCIENCES (CSI 898-Sec 001) -------------------------------------------------------------------- Chiral Selectivity and Surface Enhancement of Raman Optical Activity Bruce R. Johnson Department of Chemistry, Rice University, Houston, TX & National Science Foundation, Arlington VA Theoretical investigations are made to support the development of Surface-Enhanced Raman Optical Activity (SEROA) as a vibrational spectroscopy sensitive to molecular chirality. Ordinary Raman Optical Activity (ROA) has grown into such a tool, useful in identifiying secondary and tertiary folding structures in proteins, but handicapped by extremely small signal intensities. Exploratory experiments taking advantage of the order-of-magnitude signal enhancements for molecules near plasmonic metal nanoparticles have in turn been handicapped by uncertainty in interpretation. Here a chiroptical model is used in conjunction with extended Mie scattering theory and higher molecular multipole theory to examine in detail SEROA for molecules moving near spherical gold and silver nanoparticles. The strong non-uniform local field enhancement due to surface Plasmon excitation is found to generally interfere with selectivity of the spectroscopy for chiral molecules. It is shown, however, that specific experimental polarization strategies and detection geometries are predicted to lead to both surface enhancement and chiral selectivity. This shows that there are at least some experimental configurations where intensity differences measured in SEROA can be interpreted essentially as they are in ROA. Monday, February 7, 2011 4:30 pm Room 301, Research I, Fairfax Campus Refreshments will be served at 4:15 PM. ---------------------------------------------------------------------- Find the schedule at http://cmasc.gmu.edu/seminar/schedule.html