The accurate transition dipole moment and line intensities of NO(X2П) based on averaged quadratic coupled-cluster calculations

Abstract

For NO(X2П), the vibrational dipole moments calculated using previous accurate ab initio electric dipole moment functions (EDMFs) are not consistent with experiments, especially for high-overtone bands 3–0, 4–0, 21–17, 5–0, 6–0, and 7–0. Moreover, the band intensities of the current HITRAN database agree only roughly with recent experimental results for high-overtone bands 3–0, 4–0, and 5–0. Thus, further theoretical calculation is necessary. We adopt the highly accurate multi-reference averaged quadratic coupled-cluster (MR-AQCC) approach and four different basis sets to investigate the potential-energy curves (PECs) and EDMFs of NO(X2П). The PECs and EDMFs obtained using the aug-cc-pV6Z basis set agree well with Rydberg–Klein–Rees (RKR) potential and experimental EDMFs. They are used to deduce the vibrational dipole moments and Herman–Wallis factors, which are further be utilized to evaluate line intensities and band intensities. Both the calculated transition dipole moments and the calculated band intensities are in remarkably better agreement with the experimental results for high-overtone bands. The Herman–Wallis factors of band 7–0 are also fairly consistent between experiment and our result. We expect that these reliable and accurate theoretical results will be helpful in producing accurate theoretical predictions concerning the spectroscopic characteristics and the analysis of some experimentally measured properties of NO(X2П).