COMPARISON OF STEP-SCAN AND RAPID-SCAN APPROACHES TO THE MEASUREMENT OF MIDINFRARED FOURIER-TRANSFORM VIBRATIONAL CIRCULAR-DICHROISM

We report mid-infrared Fourier transform vibrational circular dichrois m (FT-VCD) spectra obtained by using three different measurement schem es: the traditional sequential rapid-scan method, a ne cr simultaneous rapid-scan method, and the step-scan method, We also provide a descri ption of the optical setup used to obtain the VCD spectra, Using this optical layout, we are able to measure FT-VCD spectra for single enant iomers of the chiral sample with low levels of interfering artifacts a nd for collection times as fast as one minute, For approximately 20 mi n of spectral collection, the three FT-VCD measurements approaches tes ted here yield nearly the same signal quality, The approach with the h ighest quality, by a small margin, was the simultaneous rapid-scan met hod, Next was the sequential rapid-scan approach, followed closely by the step-scan method, VCD spectra and noise curves obtained with these different measurement techniques are presented and compared, and thei r relative advantages and disadvantages are discussed.