Rotation-vibrational line lists for eight isotopologues of carbon monosulphide (CS; 12C32S, 12C33S, 12C34S, 12C36S,13C32S, 13C33S,13C34S, and 13C36S) in their ground electronic state (X1Σ+) are calculated. An empirical potential function with the corrections of Born–Oppenheimer breakdown effects, which are determined by a direct potential fitting approach using over 4300 observed transition frequencies of 12C32S, 12C33S, 12C34S, and 13C32S, is used in line list calculations. The reproduced transition frequencies are within the observation uncertainties for the isotopologues with experimental data. The dipole moment functions are calculated using an ab initio method at a multireference configuration interaction method/cc-pv5z level with a large active space of electronic configuration. The dipole moment at equilibrium nuclear separation is almost identical to the experimental result. The calculated intensities agree excellently with the laboratory observations at 2573 K. The corresponding Einstein A coefficients and oscillator strengths are predicted. Partition functions for temperatures up to 7500 K have been calculated. The line lists can be used for spectroscopic measurements of CS in astronomical environments of various temperatures.

Atomic charges were investigated as functions of detectable atomic and molecular constants at equilibrium structures. It was found based upon the variation idea that atomic charges in highly ionic molecules can be expressed as a function of molecular dipole moments, polarizabilities of free cations, and polarizabilities of free neutral atoms of the corresponding anions. The function can be given in the form of classical Rittner’s relationship ( J. Chem. Phys . 1951 , 19 , 1030). For the ground states of alkali halide molecules, the predicted atomic charges are close to an elementary charge e and the predicted dipole moments are in good agreement with the observed values; for spin-restricted high-ionic systems such as the lowest 9 Σ electronic states of BN, AlN, GaN, BP, AlP, GaP, BAs, AlAs, and GaAs molecules, the predicted atomic charges are also near 1 e and in good agreement with the results of natural population analysis at MRCI/cc-pvqz and HF/6-311+G(3df) levels. Polarizabilities for the lowest quintet states of B – , Al – , Ga – , N + , P + , and As + ions were also obtained based upon high-level ab initio computations. Atomic charges from other related methods are also investigated for comparison. The results demonstrate that high-quality atomic charges can be obtained with detectable variables, such as molecular dipole moment, vibrational frequency, as well as polarizabilities of the related free atoms and ions.