Study of the chemical evolution and spectral signatures of some interstellar precursor molecules of adenine, glycine alanine

TL;DR

This study uses quantum chemical calculations and simulations to analyze the spectral signatures and chemical evolution of interstellar precursor molecules of adenine, glycine, and alanine, considering gas and ice phases.

Contribution

It provides detailed spectral data and abundance predictions for pre-biotic molecules in interstellar environments, including effects of ice composition and phase.

Findings

Significant spectral differences between gas and ice phases.

Ice composition influences vibrational and electronic spectra.

Predicted abundances vary with cloud physical properties.

Abstract

We carry out a quantum chemical calculation to obtain the infrared and electronic absorption spectra of several complex molecules of the interstellar medium (ISM). These molecules are the precursors of adenine, glycine & alanine. They could be produced in the gas phase as well as in the ice phase. We carried out a hydro-chemical simulation to predict the abundances of these species in the gas as well as in the ice phase. Gas and grains are assumed to be interacting through the accretion of various species from the gas phase on to the grain surface and desorption (thermal evaporation and photo-evaporation) from the grain surface to the gas phase. Depending on the physical properties of the cloud, the calculated abundances varies. The influence of ice on vibrational frequencies of different pre-biotic molecules was obtained using Polarizable Continuum Model (PCM) model with the integral equation formalism variant (IEFPCM) as default SCRF method with a dielectric constant of 78.5. Time dependent density functional theory (TDDFT) is used to study the electronic absorption spectrum of complex molecules which are biologically important such as, formamide and precursors of adenine, alanine and glycine. We notice a significant difference between the spectra of the gas and ice phase (water ice). The ice could be mixed instead of simple water ice. We have varied the ice composition to find out the effects of solvent on the spectrum. We expect that our study could set the guidelines for observing the precursor of some bio-molecules in the interstellar space.