Integrated molar absorptivity of mid- and far-infrared spectra of glycine and other selected amino acids

TL;DR

This study measures the molar absorptivity and integrated molar absorptivity of five amino acids in mid- and far-infrared spectra across various temperatures to aid astrochemical identification and abundance estimation.

Contribution

It provides new infrared spectral data, temperature-dependent wavelength shifts, and equations to estimate molecular temperature and abundance in space environments.

Findings

Determined molar extinction coefficients for amino acids.

Recorded temperature-dependent infrared spectra.

Derived equations relating wavelength shifts to temperature.

Abstract

A selection of five proteinogenic amino acids, namely glycine, isoleucine, phenylalanine, tyrosine and tryptophan were studied in the mid-infrared and in the far-infrared with the purpose to facilitate the search and identification of these astrobiological and astrochemical relevant molecules in space environments. The molar extinction coefficients ({\epsilon}) of all mid- and far-infrared bands were determined as well as the integrated molar absorptivities ({\psi}). The mid-infrared spectra of the five selected amino acids were recorded also at three different temperatures from -180{\deg}C to ambient temperature to +200{\deg}C. We measure the wavelength shift of the infrared bands caused by temperature and, for the most relevant or temperature-sensitive infrared bands, a series of linear equations were determined relating wavelength position with temperature. Such equations may provide estimates of the temperature of these molecules once detected in astrophysical objects and with the reported values of {\epsilon} and {\psi}, it will be possible to estimate the relative abundance of these molecules in space environments.