ExoMol molecular line lists X: The spectrum of sodium hydride

TL;DR

This paper provides comprehensive and accurate molecular line lists for sodium hydride and its isotopologue NaD, covering a wide range of states and suitable for high-temperature astrophysical environments.

Contribution

It introduces new high-quality ab initio dipole moment curves and complete line lists for NaH and NaD, enhancing spectral modeling for astrophysical studies.

Findings

Line lists cover all relevant ro-vibrational states

NaH A-X band shows a broad absorption feature at 385 nm

Suitable for temperatures up to 7000 K

Abstract

Accurate and complete rotational, rotational-vibrational and rotational-vibrational-electronic line lists are calculated for sodium hydride: both the NaH and NaD isotopologues are considered. These line lists cover all ro-vibrational states of the ground ($X$~$^1\Sigma^+$) and first excited ($A$~$^1\Sigma^+$) electronic states. The calculations use available spectroscopically-determined potential energy curves and new high-quality, \textit{ab initio} dipole moment curves. Partition functions for both isotopologues are calculated and the effect of quasibound states is considered. The resulting line lists are suitable for temperatures up to about 7000~K and are designed for studies of exoplanet atmospheres, brown dwarfs and cool stars. In particular, the NaH $A-X$ band is found to show a broad absorption feature at about 385 nm which should provide a signature for the molecule. All partition functions, lines and transitions are available as Supplementary Information to this article and at \url{www.exomol.com}.