ALTERNATIVE DESIGN FOR IMPROVED FT-IR/VCD CAPABILITIES

A Bomem MB100-based vibrational circular dichroism (VCD) spectrometer suitable for chiroptical studies in the infrared region is described. The optical layout utilizes the spectrometer's external collimated beam. Standard VCD optics consisting of a KRS-5 polarizer and a ZnSe photoelastic modulator are mounted on an optical breadboard. A ZnSe meniscus lens focuses the beam on a small-area MCT detector. Several optical designs were examined to find the optimal positions of the optical elements. The experiments aimed to improve the energy throughput, minimize polarization artifacts, and increase signal-to-noise ratio to such an extent that single-enantiomer VCD spectra could be recorded routinely and dependably. Examples are presented illustrating the high-performance characteristics of the instrument.