MRCI study on potential energy curves, spectroscopic parameters and rovibrational energy levels of CS(X1Σ+) molecule

Using the highly accurate valence internally contracted multireference configuration interaction (MRCI) approach in combination with several groups of correlation-consistent basis sets, this paper investigates the potential energy curves (PECs), spectroscopic parameters and vibrational manifolds including rovibrational levels and transition lines of the CS(X1Σ+) molecule. The PECs are fitted to the Murrell-Sorbie function form, which are used to accurately reproduce the spectroscopic parameters (D0, ωeχe, αe and Be). By comparison with the available experiments, the PEC obtained at the basis sets, aug-cc-pCV5Z for C and cc-pV5Z for S, is selected to investigate the spectroscopic parameters and rovibrational energy levels. The present D0, De, Re, ωe, ωeχe, αe and Be are of 7.2646 eV, 7.3436 eV, 0.15403 nm, 1278.00 cm−1, 6.4924 cm−1, 0.005837 cm−1 and 0.8144 cm−1, respectively, which almost perfectly conform to the available measurements. With the interaction potential obtained at the basis sets, aug-cc-pCV5Z for C and cc-pV5Z for S, by numerically solving the radial Schrödinger equation of nuclear motion, a total of 82 vibrational states is predicted when the rotational quantum number J equals zero. The complete vibrational levels, classical turning points, inertial rotation and centrifugal distortion constants are determined when J = 0, which are in excellent agreement with the available experiments. The rovibrational energy levels of the CS(X1Σ+) molecule are calculated until J = 30. According to the rovibrational levels, a number of transition lines for the CS(X1Σ+) molecule are evaluated, which agree well with the available experimental observations.