IOP Publishing, Journal of Physics: Conference Series, (548), p. 012017, 2014
DOI: 10.1088/1742-6596/548/1/012017
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The recording of Raman spectra for many molecules in air at room temperature is difficult or impossible as a result of sample degradation which is due to a combination of laser heating and oxidation. Often nitrogen gas is applied over the sample in an attempt to reduce oxidation. Also, the samples are sometimes cooled to reduce ro-vibrational "hot bands" and enhance the spectra. We have found great utility in recording Raman spectroscopy of samples under liquid nitrogen, a technique we call RUN. The RUN spectra show much higher resolution as a result of ro-vibrational cooling and in some cases cooling produces only the lowest energy conformer of the molecular ensemble further simplifying the spectra. A very sharp Raman peak at 2327.0 cm−1, due to liquid nitrogen, also serves as a convenient wavelength calibration. We also demonstrate the ability to clearly delineate the lattice modes for naphthalene and benzene crystals.