ExoMol line lists XXIV: A new hot line list for silicon monohydride, SiH

TL;DR

This paper presents a comprehensive and accurate hot line list for silicon monohydride (SiH), including multiple isotopologues, to aid astrophysical spectral analysis of cool stars and exoplanet atmospheres.

Contribution

The authors developed a new, extensive line list for SiH with refined potential energy curves and over 1.7 million transitions, covering high temperatures relevant to astrophysics.

Findings

Line list includes 11,785 rovibronic states and 1,724,841 transitions.

Spectra simulated with the line list match experimental data.

Applicable to temperatures up to ~5000 K for astrophysical observations.

Abstract

SiH has long been observed in the spectrum of our Sun and other cool stars. Computed line lists for the main isotopologues of silicon monohydride, $^{28}$SiH, $^{29}$SiH, $^{30}$SiH and $^{28}$SiD are presented. These line lists consider rotation-vibration transitions within the ground $X$ $^{2}\Pi$ electronic state as well as transitions to the low-lying $A$ $^{2}\Delta$ and $a$ $^{4}\Sigma^-$ states. Ab initio potential energy (PECs) and dipole moment curves (DMCs) along with spin-orbit and electronic-angular-momentum couplings between them are calculated using the MRCI level of theory with the MOLPRO package. The PEC for the ground X $^2\Pi$ state is refined to available experimental data with a typical accuracy of around 0.01 cm$^{-1}$ or better. The $^{28}$SiH line list includes 11,785 rovibronic states and 1,724,841 transitions with associated Einstein-A coefficients for angular momentum $J$ up to $82.5$ and covering wavenumbers up to 31340 cm$^{-1}$ ($\lambda$ $<$ 0.319 $\mu$m). Spectra are simulated using the new line list and comparisons made with various experimental spectra. These line lists are applicable up to temperatures of ~5000 K, making them relevant to astrophysical objects such as exoplanetary atmospheres and cool stars and opening up the possibility of detection in the interstellar medium. These line lists are available at the ExoMol www.exomol.com and CDS database websites.