THz Time-Domain Spectroscopy of Mixed CO2-CH3OH Interstellar Ice Analogs

TL;DR

This study uses THz time-domain spectroscopy to analyze the structural and compositional properties of interstellar ice analogs containing CO2 and CH3OH, revealing insights into their physical state and potential astronomical detection.

Contribution

It demonstrates the effectiveness of THz spectroscopy in characterizing interstellar ice analogs, highlighting its ability to determine structure, segregation, and thermal history of the ices.

Findings

THz spectroscopy distinguishes crystalline and amorphous ice structures.

It reveals the degree of segregation of CO2 and CH3OH within the ice.

THz transitions can be useful for astronomical detection of interstellar ices.

Abstract

The icy mantles of interstellar dust grains are the birthplaces of the primordial prebiotic molecular inventory that may eventually seed nascent solar systems and the planets and planetesimals that form therein. Here, we present a study of two of the most abundant species in these ices after water: carbon dioxide (CO2) and methanol (CH3OH) using TeraHertz (THz) time-domain spectroscopy and mid-infrared spectroscopy. We study pure and mixed-ices of these species, and demonstrate the power of the THz region of the spectrum to elucidate the long-range structure (i.e. crystalline versus amorphous) of the ice, the degree of segregation of these species within the ice, and the thermal history of the species within the ice. Finally, we comment on the utility of the THz transitions arising from these ices for use in astronomical observations of interstellar ices.