Temperature-dependent terahertz spectroscopy of l-phenylalanine

J L Allen; T J Sanders; R Plathe; D Appadoo; J Horvat; R A Lewis

doi:10.1016/j.saa.2021.119922

Temperature-dependent terahertz spectroscopy of l-phenylalanine

Spectrochim Acta A Mol Biomol Spectrosc. 2021 Nov 5:260:119922. doi: 10.1016/j.saa.2021.119922. Epub 2021 May 8.

Authors

J L Allen¹, T J Sanders², R Plathe³, D Appadoo³, J Horvat², R A Lewis²

Affiliations

¹ Institute for Superconducting and Electronic Materials and School of Physics, University of Wollongong, NSW 2522, Australia. Electronic address: ja846@uowmail.edu.au.
² Institute for Superconducting and Electronic Materials and School of Physics, University of Wollongong, NSW 2522, Australia.
³ Australian Synchrotron, Australian Nuclear Science and Technology Organisation, 800 Blackburn Rd Clayton, VIC 3168, Australia.

PMID: 34058666
DOI: 10.1016/j.saa.2021.119922

Abstract

Undiluted l-phenylalanine has been cooled to 6K and its transmission spectrum obtained under terahertz radiation from a synchrotron source. Three distinct absorption bands are evident: at 1.37, 2.14, and 2.32THz. Each of these tracks to lower frequency ("redshifts") as the temperature is increased from 6 to 250K. The observed shifts are in the range of 0.1-0.2THz. The form of the temperature dependence is well accounted for by a Bose-Einstein model, from which the zero-temperature frequency of each mode and the characteristic temperature of the associated phonon bath may be estimated. At 6K a fourth band is evident, at 2.65THz. However, the depth of this, touching the noise floor, coupled with the increasing opacity of the sample with temperature for frequencies beyond 2.5THz, makes it difficult to track. The frequencies of all four modes are in good accord with and thus confirm a previous calculation.

Keywords: Amino acid; Bose-Einstein; Redshift; THz; Terahertz; l-phenylalanine.

MeSH terms

Phenylalanine
Temperature
Terahertz Spectroscopy*

Substances

Phenylalanine