报告人：汤一乔 哈佛大学

报告时间：5月13日上午10:00

报告地点：理科楼三楼报告厅

报告题目：Enhanced enantioselectivity in excitation of chiral molecules by superchiral light

报告摘要：A molecule or larger body is chiral if it cannot be superimposed on its mirror image (enantiomer). Electromagnetic fields may be chiral too, with circularly polarized light (CPL) as the paradigmatic example. We recently introduced a measure of the local degree of chiral dissymmetry in electromagnetic fields suggested the existence of modes more selective than circularly polarized plane waves in preferentially exciting single enantiomers in certain regions of space. By probing induced fluorescence intensity, we demonstrate experimentally an 11-fold enhancement over CPL in discrimination of the enantiomers of a biperylene derivative by precisely sculpted electromagnetic fields. This result, which agrees to within 15% with theoretical predictions, establishes that optical chirality is a fundamental and tunable property of light, with possible applications ranging from plasmonic sensors to absolute asymmetric synthesis. Reference: 1. Yiqiao Tang and Adam E. Cohen, Enhanced enantioselectivity in excitation of chiral molecules by superchiral light, Science, 332, 333, 2011; 2. Yiqiao Tang and Adam E. Cohen, Optical chirality and its interaction with matter, Phys. Rev. Lett., 104, 163901, 2010 (cover story); 3. Yiqiao Tang, Timothy A. Cook and Adam E. Cohen, Limits on fluorescence dtected circular dichroism of single helicene molecules, J. Phys. Chem. A, 113, 6213, 2009; 4. Nan Yang, Yiqiao Tang and Adam E. Cohen, Spectroscopy in sculpted fields, Nano Today, 4, 269, 2009.