Chemistry of TMC-1 with multiply deuterated species and spin chemistry of H2, H2+, H3+ and their isotopologues

TL;DR

This study develops a comprehensive chemical network for multiply deuterated species and spin chemistry, applying it to TMC-1 to improve understanding of deuterium fractionation and predict observable deuterated molecules.

Contribution

It introduces the first publicly available chemical network for multiply deuterated species with spin chemistry integrated into the NAUTILUS code, enhancing astrochemical modeling accuracy.

Findings

D/H ratios in TMC-1 match model predictions

Inclusion of deuteration alters non-deuterated species abundances

List of potential observable deuterated species in TMC-1

Abstract

Deuterated species are unique and powerful tools in astronomy since they can probe the physical conditions, chemistry, and ionization level of various astrophysical media. Recent observations of several deuterated species along with some of their spin isomeric forms have rekindled the interest for more accurate studies on deuterium fractionation. This paper presents the first publicly available chemical network of multiply deuterated species along with spin chemistry implemented on the latest state-of-the-art gas-grain chemical code `NAUTILUS'. D/H ratios for all deuterated species observed at different positions of TMC-1 are compared with the results of our model, which considers multiply deuterated species along with the spin chemistry of light hydrogen bearing species H2, H2+, H3+ and their isotopologues. We also show the differences in the modeled abundances of non-deuterated species after the inclusion of deuteration and spin chemistry in the model. Finally, we present a list of potentially observable deuterated species in TMC-1 awaiting detection.