Terahertz spectroscopy of solid serine and cysteine

Terahertz (THz) absorption spectra of the similarly structured amino acids l-serine and l-cysteine in the solid phase at 77 and 298 K are reported and compared to isolated molecule and solid-state infrared vibrational spectral calculations using empirical force field and density functional theory. These comparisons suggest that many higher frequency internal modes can readily be assigned but lowest frequency intermolecular and phonon modes can adequately be understood with more advanced solid-state theory using currently available potential functions.