Laboratory investigation of pure and mixed ices of astrochemical relevance via THz and IR spectroscopy

Abstract

In the interstellar medium (ISM), atoms and simple mols. can react on the surface of icy dust grains to form more complex org. species (COMs), such as prebiotic mols. Consequently, the unambiguous identification of COMs in the solid phase in the ISM, as well as the study of the dynamics of interstellar ices, will help unravel the chem. evolution of the universe.THz spectroscopy provides a powerful technique capable of identifying gas phase mols. in the ISM. Thus, lab. data of ices in the THz region of the electromagnetic spectrum have the potential to support the future identification of COMs in the solid phase. In addn. to providing a spectral fingerprint, THz spectroscopy probes the phonon modes of a solid. As such, the absorptions of ices in the THz region give insights into the structural dynamics of species in the solid phase.In this work, spectra of ices of both pure mols. and mixts. were collected in the THz region (0.1 THz - 6 THz, 0.3 cm^(-1) - 200 cm^(-1)) using the Blake Group THz Time-Domain Spectrometer. The spectrometer features an air plasma THz source and electrooptic detection in either ZnTe or GaP. Spectra were simultaneously collected in the mid-IR (500 cm^(-1) - 4000 cm^(-1)) to quant. characterize the ices by using the already published literature in this spectral range. Our work will ultimately become a part of the THz ice-database that we will build to help the identification of solid COMs in the ISM.