Terahertz spectroscopic investigation of D- and DL-tartaric acid

The terahertz (THz) absorbance spectra of two tartaric acid isomers (D- and DL-tartaric acid) were determined using terahertz time-domain spectroscopy (THz-TDS) in the range of 0.2-2.0 THz. Significant differences between D-and DL-tartaric acid have been found in their THz characteristic absorption peaks. To simulate their THz spectra, theoretical calculations on isolated-molecule and unit cell of these two tartaric acids were performed, and the computed THz spectra were in accordance with the experimental THz spectra. Moreover, the positions and types of intermolecular interactions in tartaric acids are visualized by using the reduced density gradient (RDG) analysis. Results show that THz absorbance spectra of the two isomers are highly sensitive to the molecular structures including the subtle difference of functional groups and chemical bonds, and the THz-TDS can be used as an effective means for molecular identification in the fields of biology, medicine, and pharmacy.