Infrared Spectra of Solid-State Ethanolamine: Laboratory Data in Support of JWST Observations

TL;DR

This study provides laboratory infrared spectra and band strengths of solid ethanolamine ice, supporting JWST observations and aiding in the detection of this molecule in interstellar ices.

Contribution

It offers the first estimation of infrared band strengths and phase transition temperature of solid ethanolamine ice through experimental methods.

Findings

Infrared band strength of ethanolamine ice is approximately 1×10⁻¹⁷ cm molecule⁻¹.

Ethanolamine ice transitions occur between 175 and 185 K.

Multilayer desorption energy of ethanolamine ice is 0.61 eV.

Abstract

Ethanolamine (NH$_2$CH$_2$CH$_2$OH, EA) has been identified in the gas phase of the ISM within molecular clouds. Although EA has not been directly observed in the molecular ice phase, a solid state formation mechanism has been proposed. However, the current literature lacks an estimation of the infrared band strengths of EA ices. We conducted an experimental investigation of solid EA ice at low temperatures to ascertain its infrared band strengths, phase transition temperature, and multilayer binding energy. The commonly used laser interferometry method was not applied. Infrared band strengths were determined using three distinct methods. The obtained lab spectrum of EA was compared with the publicly available MIRI MRS James Webb Space Telescope observations toward a low mass protostar. The phase transition temperature for EA ice falls within the range of 175 to 185 K. Among the discussed methods, the simple pressure gauge method provides a reasonable estimate of band strength. We derive a band strength value of about $1\times10^{-17}$ cm molecule$^{-1}$ for the NH$_2$ bending mode in the EA molecules. Additionally, temperature-programmed desorption analysis yielded a multilayer desorption energy of 0.61$\pm$0.01 eV. By comparing the laboratory data documented in this study with the JWST spectrum of the low mass protostar IRAS 2A, an upper-limit for the EA ice abundances was derived.