Accurate theoretical characterization of MgS: rovibrational line intensities and absorption cross-sections for...

The electronic structure, spectroscopic constants, and transition parameters of the diatomic molecule Magnesium monosulfide (MgS) were investigated using high-level multi-reference configuration interaction calculations with the Davidson correction (MRCI+Q) and a consistent basis set for both Mg and S atoms. Potential energy curves and dipole moment functions were computed, allowing for accurate predictions of rovibrational energy levels. Key transition properties, including radiative lifetimes and Franck-Condon factors, were evaluated for transitions within the ground electronic state and the first excited singlet state. For the ground-state X¹Σ⁺ rovibrational transitions in the infrared region, the line intensity distribution is dominated by Δv = 0 transitions, with peak intensities reaching 1.83 × 10^-20cm/molecule. The A¹Π - X¹Σ⁺ electronic absorption cross-section reaches a maximum of 2.258 × 10^-17 cm²/molecule in the 2-0 band at T = 50 K and P = 1 bar. These results provide benchmark spectroscopic data for the detection of MgS in cold molecular clouds and enhance the spectral database required for astrophysical modeling and astronomical observations.