Raman Optical Activity, Spectrometers

Advances in instrumentation over the past decade have led to decisive progress in the routine measurement of Raman optical activity. The optical creation of a virtual enantiomer, in conjunction with scrambling of components of linear polarization in the exciting and scattered light without degrading its circular content, has solved the problem of deterministic offsets. Spectrographs based on planar holographic grating technology and light collection optics capable of filling their large etendue (the amount of light that an optical system is capable of collecting), combined with multichannel detection with backthinned CCDs, have reduced the shot noise problem to an extent where the possible use of transform spectroscopy, providing Jacquinot throughput and Fellget multiplexing gain simultaneously, is unlikely to provide an improvement for visible light. Flicker noise has been reduced in collinear scattering by the simultaneous detection of right and left circularly polarized light. Problems remain due to spontaneous Raman scattering's low dynamic range and due to fluorescence for excitation at visible wavelengths.