Schematic representation of the experimental setup for (a) VCD and (b) vibrational ORD measurements. (c) Both measurements can equally be performed with the PEM placed behind the sample (see text for details).
Enhancement of VCD signal , measured between two crossed polarizers, as a function of PEM retardation (red line). The enhancement factor is equal to the ellipticity of the electric field, indicated in black. The blue line shows the scaling of the signal that would be measured without a second polarizer.
(a) CH-stretch absorption of dissolved in (sample thickness ). (b) VCD signal, recorded with the dispersive VCD spectrometer using alternatingly left and right handed circular polarized laser pulses (PEM retardation ). (c) Same VCD spectrum recorded with a second polarizer placed between sample and detector. (d) Enhanced VCD data recorded using elliptical pulses (PEM retardation ). The noise level is indicated by the gray lines, which show the difference between two consecutive sets of scans of 200 s each.
Asymmetric stretch of azide bound to myoglobin in phosphate buffer (sample thickness ). (a) Absorption and (b) enhanced VCD signal recorded with elliptical polarized pulses. The PEM retardation was set to , corresponding to an enhancement factor of 5.
CH stretch vibrations of limonene dissolved in (sample thickness ). (a) Absorption and (b) vibrational ORD signal of R- and S-forms (blue and red) recorded with a polarizer inclination of 5°. The difference between the two enantiomer spectra is shown at the bottom (measurement time 13 min for each enantiomer and the solvent background). Solid squares: polarization modulation before the sample, wire-grid polarizers; solid lines: polarization modulation after the sample, calcite polarizers.
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