Novel Raman Spectroscopy Method for Solutions in Uniform, High-Strength Electric Field.

A novel method of measuring the influence of high electric fields on the Raman scattering of fluids is introduced, which can help understand various interactions of a fluid with the high electric field. The microfluidic chip can impose highly controlled, uniform electric fields across the measurement volume with blocked electrodes, eliminating spurious reactions at the electrode surface. The developed methodology and the experimental setup are utilized to examine the effect of the electric field on three of the stretching vibrations of ethanol in water-ethanol mixtures with varying concentrations of ethanol and effective electric fields up to 1.0MV/m. The increase in the electric field is seen to broadly decrease the intensity of Raman scattering due to a decrease in the polarizability of the ethanol molecules. Although this effect is uniform for all water-ethanol mixtures, it reduces in mixtures with high weight-fractions of water because of the already reduced polarizability of an ethanol molecule due to hydrogen bonding. The combined effect of hydrogen bonding and increase in temperature due to the alternating high electric field even results in an increase in the magnitude of peak intensity for relatively low-weight fractions of ethanol.