Development of infrared electroabsorption spectroscopy for liquids

An infrared spectroscopic system has been constructed that is specifically designed for electroabsorption measurements of liquids. The system can detect electric-field-induced absorbance changes as small as one part in a million, two orders of magnitude better than the conventional difference spectrum method using FT-IR. Electroabsorption spectra of liquid 1,2-dichloroethane have been measured. The observed absorbance changes have been explained in terms of two dominant mechanisms; the change in the trans-gauche equilibrium, and the orientational polarization of the gauche conformer. It is demonstrated that infrared electroabsorption spectroscopy provides useful information on otherwise inaccessible electric properties of molecules in liquids.