Laser Raman and infrared spectra of tartaric acid crystals

A systematic analysis of the IR and Raman spectra of tartaric acid (TA) [HOOC(CHOH) 2 COOH], based on standard frequency correlations, deuteration shift and typical characteristics (with respect to intensity and width) of bands due to different modes, is reported. Almost all the vibrational modes of TA appear with two or more split components. The doublet structure of the ν CH , ν CO and δ modes arises mainly owing to crystallographically distinguishable sites for two identical oscillators. The splitting of other modes [viz. ν CO , β CH , ν , ν and τ COOH ] originates from differences in the crystallographic fields around the two identical oscillators and resonance interactions between such oscillators. The doublet of δ arises mainly from resonance interactions between two identical oscillators of two identical groups in TA.