Sum-Frequency Vibrational Spectroscopy on Chiral Liquids: A Novel Technique to Probe Molecular Chirality

Abstract

Optical activity in sum-frequency vibrational spectra has been observed for the first time in chiral liquids. The electric-dipole allowed chiral element of the nonlinear susceptibility appears to be 3 orders of magnitude smaller than typical allowed achiral elements. This is partly because the observed chirality requires a breakdown of the Born-Oppenheimer approximation.

Vibrational spectroscopy for probing molecular-level interactions in organic films mimicking biointerfaces

“…With SFG, conformational changes in lipid chains lead to changes in the ratio of intensities for CH 2 and CH 3 stretches, a much more sensitive and compelling evidence [76]. Detection of molecular chirality is also quite simple and sensitive with SFG [80,124]. Finally, the possibility of SFG imaging of interfaces, with chemical (vibrational spectroscopy) and orientational sensitivities, and good spatial resolution (a few μm) has been demonstrated in the last decade [177,178].…”

“…Finally, for a solution of chiral molecules there is no inversion symmetry, since inversion would change the handedness of the molecules. In this case, the SFG signal may be generated from the bulk solution, up to the coherence length for the particular experimental configurationusually several hundred nm, for the reflection geometry [80].…”

Stereochemical transfer to atmospheric aerosol particles accompanying the oxidation of biogenic volatile organic compounds

“…The tensor was accessed by upconverting the p-polarized infrared light at the filter surface using visible light polarized either +45°o r −45°away from the surface normal and recording the p-polarized component of the vibrational SFG response [Oh-e et al, 2004]. Under this configuration, achiral and racemic systems exhibit no signal difference whereas systems consisting of mixtures of unequal amounts of stereoisomers respond strongly [Belkin et al, 2000;Stokes et al, 2007].…”

Sensitive Chiral Analysis via Microwave Three-Wave Mixing

“…2 Sumfrequency generation (SFG) in the infrared and visible has been observed in samples of chiral molecules in solution. 3 Doubly resonant SFG in both the infrared and microwave regime has been proposed but not observed. 4,5 Our group recently demonstrated enantiomer-sensitive spectroscopy by combining a resonant microwave field with a strong adiabatically switched orthogonal nonresonant (DC) electric field.…”

“…An enantiomer-dependent signal V E will only 3 The corresponding frequencies for 1,3-butanediol are as follows: ν 1 = 15052.2 MHz, |3 13 → |3 21 ; ν 2 = 168.0 MHz, |3 21 → |3 22 ; ν 3 = ν 1 −ν 2 = 14884.2 MHz, |3 22 → |3 13 Figure 2: The experimental apparatus. The cold molecular sample is injected into a cold (5.5 K) cell anchored to a closed cycle pulse tube refrigerator.…”