Ab initioMRCI + Q study on potential energy curves and spectroscopic parameters of low-lying electronic states of CS⁺

Abstract

Carbon monosulfide molecular ion (CS+), which plays an important role in various research fields, has long been attracting much interest. Because of the unstable and transient nature of CS+, its electronic states have not been well investigated. In this paper, the electronic states of CS+ are studied by employing the internally contracted multireference configuration interaction method, and taking into account relativistic effects (scalar plus spin—orbit coupling). The spin—orbit coupling effects are considered via the state-interacting method with the full Breit—Pauli Hamiltonian. The potential energy curves of 18 Λ—S states correlated with the two lowest dissociation limits of CS+ molecular ion are calculated, and those of 10 lowest Ω states generated from the 6 lowest Λ—S states are also worked out. The spectroscopic constants of the bound states are evaluated, and they are in good agreement with available experimental results and theoretical values. With the aid of analysis of Λ—S composition of Ω states at different bond lengths, the avoided crossing phenomena in the electronic states of CS+ are illuminated. Finally, the single ionization spectra of CS (X1Σ+) populating the CS+(X2Σ+1/2, A2Π3/2, A2Π1/2, and B2Σ+1/2) states are simulated. The vertical ionization potentials for X2Σ+1/2, A2Π3/2, A2Π1/2, and B2Σ+1/2 states are calculated to be 11.257, 12.787, 12.827, and 15.860 eV, respectively, which are accurate compared with previous experimental results, within an error margin of 0.08 eV∼0.2 eV.

Potential energy curves, transition dipole moments, and radiative lifetimes of KBe molecule

“…In this work, we have carried out the multi-reference configuration interaction (MRCI) [26,27] computations on three 2 Σ + , two 4 Π, and three 4 Σ + states of KBe molecule based on inner shell electron correlations. At the present time, Li, [28] Zhu, [29] Wang, [30] Liu, [31] and Xing [32] have adopted the MRCI method to calculate the ground and low-lying states of CS + , AsO + , P 2 , GeO, and CF + , and the obtained results conform to the experimental values. No experimental data have yet been found in the literature for these states, and our main goal is to provide accurate spectroscopic parameters for these states.…”

Accurate <em>ab initio</em>-based potential energy curve and spectroscopic properties of NO(X²Π) via extrapolation to the complete basis set limit

“…As reference of the wave function we can using the full valence complete-active-space self-consistent field(CASSCF) [16], applied to many diatomic [17,18]. The MRCI(Q) method is one of the most approaches and quantum chemistry program packages.…”

Accurate ab initio -based analytical potential energy function for S 2 (ã 1 Δ g ) via extrapolation to the complete basis set limit

“…All electronic structure calculations have been carried out at the MRCI(Q) level [20] using the full valence completeactive-space self-consistent field (CASSCF) [25] wave function as the reference, which has recently been applied to many diatomic molecules. [26][27][28] The AVXZ (X = T, Q, 5, 6) basis sets of Dunning [21,22] have been employed, and the calculations are carried out employing the MOLPRO 2012 package. [29] In the calculation, C 2v point group symmetry is adopted, which holds four irreducible representations, namely, A1, B1, B2, and A2.…”