ExoMol line lists -- XLIV. IR and UV line list for silicon monoxide (SiO)

Abstract

A new silicon monoxide ( 28 Si 16 O) line list covering infrared, visible and ultraviolet regions called SiOUVenIR is presented. This line list extends the infrared EBJT ExoMol line list by including vibronic transitions to the A 1 Π and E 1 Σ + electronic states. Strong perturbations to the A 1 Π band system are accurately modelled through the treatment of 6 dark electronic states: C 1 Σ − , D 1 ∆, a 3 Σ + , b 3 Π, e 3 Σ − and d 3 ∆. Along with the X 1 Σ + ground state, these 9 electronic states were used to build a comprehensive spectroscopic model of SiO using a combination of empirical and ab initio curves, including the potential energy (PE), spin-orbit (SO), electronic angular momentum (EAM) and (transition) dipole moment curves. The ab initio PE and coupling curves, computed at the multireference configuration interaction (MRCI) level of theory, were refined by fitting their analytical representations to 2617 experimentally derived SiO energy levels determined from 97 vibronic bands belonging to the X-X, E-X and A-X electronic systems through the MARVEL procedure. 112 observed forbidden transitions from the C-X, D-X, e-X, and d-X bands were assigned using our predictions, and these could be fed back into the MARVEL procedure. The SiOUVenIR line list was computed using published ab initio transition dipole moments for the E-X and A-X bands; the line list is suitable for temperatures up to 10 000 K and for wavelengths longer than 140 nm. SiOUVenIR is available from www.exomol.com and the CDS database.

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“…For the chemistry, we use the molecular line-lists from the Exomol project (Tennyson et al 2016;Chubb et al 2021), HITEMP (Rothman & Gordon 2014) and HITRAN (Gordon et al 2016). In the free retrievals, we consider molecular cross-sections at resolution R=15,000 for H 2 O (Barton et al 2017;Polyansky et al 2018) (Li et al 2019), AlO (Bowesman et al 2021;Patrascu et al 2015), SiO (Barton et al 2013;Yurchenko et al 2021), PH 3 (Sousa-Silva et al 2015), ScH (Lodi et al 2015) and CrH (Bernath 2020). Atomic and ionic species were not included as they do not absorb in the wavelength range considered here.…”