Hyper-Raman spectroscopy of polar liquids excited at 1064 nm: Acetone, acetonitrile, chloroform, and dimethyl sulfoxide.

Abstract

Hyper-Raman (HR) spectra of polar liquids are reported. Acetone, acetonitrile, chloroform, and dimethyl sulfoxide in the liquid phase were measured by using a picosecond laser whose wavelength is 1064 nm and repetition rate is 200 kHz. HR spectra with a high signal to noise ratio were obtained without the surface enhancement or the electronic resonance effect. Due to the improvement of the sensitivity, many vibrational bands were first observed in HR spectroscopy. The peak frequencies, relative intensities, band assignments, including symmetry species, and depolarization ratios are examined. All IR active vibrational modes well separated were, indeed, observed in HR spectra following the selection rule, whereas HR spectra show not only similarity but also difference in relative signal intensities compared with IR spectra. This work demonstrates the possibility of HR spectra in the liquid phase and suggests further research on molecular structures by HR spectroscopy.