Terahertz Spectroscopy and Density Functional Theory Calculations of dl-Norleucine and dl-Methionine.

We present terahertz (THz) measurements and density functional theory (DFT) calculations of two amino acid crystals: dl-norleucine and dl-methionine. Their molecular structures are very similar and therefore also their crystal structures. We report the absorption spectra for both amino acids, which have a strong resonance at 1.