Berlin 2001 – wissenschaftliches Programm
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CPP: Chemische Physik und Polymerphysik
CPP 9: New Methods
CPP 9.3: Vortrag
Mittwoch, 4. April 2001, 16:25–16:45, 112
Vibrational sum-frequency generation spectroscopy in chiral media — •Karl-Heinz Ernst1, Mikhail Belkin2, Timofei Kulakov2, Li Yan3, and Yuen-Ron Shen2 — 1Swiss Federal Institute for Materials Research, EMPA Duebendorf — 2Department of Physics, University of California, Berkeley, USA — 3Department of Electrical Engineering, University of Maryland, College Park, USA
The absence of inversion symmetry allows sum-frequency generation (SFG) in isotropic chiral media. SFG vibrational spectra obtained from a number of chiral liquids will be presented. Using an input/output polarisation combination that probes only the chiral elements of the second-order nonlinear susceptibility, the optically active SF-resonant signals of C-H stretch vibrations in the 2800/cm to 3100/cm range are observed. A linear dichroism, resulted from the interplay of the chiral and achiral elements of the second order susceptibility tensor is also observed for R- and S- limonene. By symmetry, only the purely electric dipole allowed transitions contribute to the chiral signal from the bulk. However, the signal is small, because the antisymmetric part of the nonresonant Raman transition involved in the SFG process is usually weak. The microscopic origin of the chirality appearing in the vibrational SFG will be discussed. This work was supported by the US-Department of Energy (DOE).