Search for Interstellar Adenine

TL;DR

This study investigates the chemical pathways for interstellar adenine formation, highlighting the most dominant precursors and providing spectral data to aid future observational detection in space.

Contribution

It introduces new formation pathways for adenine in interstellar medium and assesses their significance using a comprehensive chemical model.

Findings

The new pathways significantly contribute to adenine formation.

Two precursors, C3NH and HNCNH, are key targets for observations.

Spectral data for adenine and precursors are provided.

Abstract

It is long debated if pre-biotic molecules are indeed present in the interstellar medium. Despite substantial works pointing to their existence, pre-biotic molecules are yet to be discovered with a complete confidence. In this paper, our main aim is to study the chemical evolution of interstellar adenine under various circumstances. We prepare a large gas-grain chemical network by considering various pathways for the formation of adenine. Majumdar et al. (2012) proposed that in the absence of adenine detection, one could try to trace two precursors of adenine, namely, HCCN and NH_2CN. Recently Merz et al. (2014), proposed another route for the formation of adenine in interstellar condition. They proposed two more precursor molecules. But it was not verified by any accurate gas-grain chemical model. Neither was it known if the production rate would be high or low. Our paper fills this important gap. We include this new pathways to find that the contribution through this pathways for the formation of Adenine is the most dominant one in the context of interstellar medium. We propose that observers may look for the two precursors (C_3NH and HNCNH) in the interstellar media which are equally important for predicting abundances of adenine. We perform quantum chemical calculations to find out spectral properties of adenine and its two new precursor molecules in infrared, ultraviolet and sub-millimeter region. Our present study would be useful for predicting abundance of adenine.