MRCI study on potential energy curves, spectroscopic parameters and rovibrational energy levels of CS(X 1Σ +) molecule

Abstract

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(X 1Σ +) molecule. The PECs are fitted to the Murrell–Sorbie function form, which are used to accurately reproduce the spectroscopic parameters ( D 0, ω eχ e , α e and B e ). 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 D 0, D e , R e , ω e , ω eχ e , α e and B e 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(X 1Σ +) molecule are calculated until J = 30. According to the rovibrational levels, a number of transition lines for the CS(X 1Σ +) molecule are evaluated, which agree well with the available experimental observations.