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.