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

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, ²⁸SiH, ²⁹SiH, ³⁰SiH and ²⁸SiD are presented. These line lists consider rotation–vibration transitions within the ground X²Π electronic state as well as transitions to the low-lying A²Δ and a⁴Σ⁻ states. Ab initio potential energy (PECs) and dipole moment curves along with spin–orbit and electronic angular momentum couplings between them are calculated using the multireference configuration interaction level of theory with the MOLPRO package. The PEC for the ground X²Π state is refined to available experimental data with a typical accuracy of around 0.01 cm⁻¹ or better. The ²⁸SiH line list includes 11 785 rovibronic states and 1724 841 transitions with associated Einstein-A coefficients for angular momentum J up to 82.5 and covering wavenumbers up to 31 340 cm⁻¹ (λ < 0.319 μm). 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, called SiGHTLY, are available at the ExoMol (www.exomol.com) and CDS data base websites