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Low frequency Raman spectroscopy is a highly sensitive and non-destructive technique used to investigate the vibrational and rotational modes of biological and non-biological materials. The Raman spectra measured provide information about the chemical structure and nature of these materials. In this study, we present the design and construction of a low frequency Raman spectroscopy system that is able to measure signals <10 cm-1 to <400 cm-1. The system consisted of a 514.5nm monochromatic laser directed through a polarizing beam cube and half waveplate to adjust the intensity of the beam. The beam was expanded and reflected off a 514.5 nm high pass filter before passing through a 50x Mitutoyo objective, which focuses it onto the sample. The back scattered light was recollimated through the objective. The high pass filter and three 514.5 nm Bragg filters were used to reduce the Rayleigh signal. The remaining Raman signal was focused into a Shamrock 303i spectrometer with a cooled ANDOR CCD camera. Using high dynamic range data acquisition with background subtraction, this system allowed low frequency Raman spectroscopy of reduced cytochrome C, bovine serum albumin, microtubules and collagen in solution. The system has the advantage of enabling the measurement of the low frequency Raman signal without sacrificing the ability to perform traditional Raman spectroscopy.
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