Rotating mirror device for nonresonant laser Raman difference spectroscopy

A novel sample switching device for laser Raman difference spectroscopy (LRDS) has been designed for use with nonresonant samples. The device utilizes a single motor driven rotating mirror, fabricated by diamond turning techniques, which switches both exciting and scattered light 60 times per second. Electronic timing signals are obtained to gate photon counting pulses into separate scalers. The use of fixed capillary sample cells allows for the first time in LRDS the examination of fibers, single crystals, and liquid samples of 10-μl volume and improved access to samples for thermostating, etc. Alignment of the optics is described. Proper operation of the system is illustrated by examination of pyridine and pyridine-d₅. Comparing spectra of the neat liquids and a mixture of them gives examples of a frequency shift of <1 cm^-1, a width change, and other bands with no changes. Advantages, limitations, and future extensions of the instrument are described.