Anharmonicity-driven redshift and broadening of sharp terahertz features of α-glycine single crystal from 20 K to 300 K: Theory and experiment

Authors

Jackson Allen, University of WollongongFollow
Thomas Sanders, University of WollongongFollow
Josip Horvat, University of WollongongFollow
R A. Lewis, University of WollongongFollow

RIS ID

145044

Publication Details

Allen, J., Sanders, T., Horvat, J. & Lewis, R. (2021). Anharmonicity-driven redshift and broadening of sharp terahertz features of α-glycine single crystal from 20 K to 300 K: Theory and experiment. Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy, 244

Abstract

© 2020 Elsevier B.V. For the first time, large single crystals of the simplest amino acid, glycine, have been used to determine the temperature dependence of its terahertz spectrum. High-quality spectra with very sharp absorption features are observed at cryogenic temperatures. The α-glycine structure and the purity of the crystals were verified via Raman spectroscopy and X-ray diffraction. Spectral redshift with increasing temperature was observed for all absorption bands in the terahertz region (10–250 cm−1, or 1–8 THz) over the temperature range of 20–300 K. X-ray diffraction revealed expansion in all planes of the crystal lattice over the same temperature range. A Bose-Einstein distribution was used to model the frequency position shift of the two lowest-energy fundamental modes at 50 cm−1 and 69 cm−1. On this basis, we attribute the observed redshift and broadening with increasing temperature to the anharmonic potential associated with the phonon bath.