Accurate Semi-Empirical Potential Energy Function, Ro-Vibrational Spectrum and the Effect of Temperature and Pressure for ¹²C ¹⁶O

With the rapid development of high-supersonic aircraft, non-contact diagnosis technology, etc,more molecular bands are excited, and the demand for rovibrational spectrum data under high temperature and high pressure has increased dramatically. In addition, with the rapid improvement of the cavity ring-down spectroscopy (CRDS), and the tunable semiconductor laser absorption spectrum technology (TDLAS) with high sensitivity, the research on the corresponding spectrum are promoted further accordingly. CO, an important product of high-temperature combustion, is the first to be investigated. In this paper, firstly, the local discrete potential energy points near the molecular equilibrium internuclear separation were obtained employing the Rydberg-Klein-Rees (RKR) method, with the use of spectral parameters of the (CO)-C-12-O-16 on the ground state (vibrational quantum number nu<41) determined by the experimental. Then it is fitted to more than ten common analytical potential functions, and it is shown that the SPF and Morse functions have good fitting accuracy, but they are still unreasonable on the long-range part. Because of this, the dissociation energy from the experiment is adopted for revising the long-range part, and a new, semi-empirical, global potential function named Revised-Morse was constructed, which not only could accurately reproduce the known vibrational levels but reasonably predict the unknown high vibrational levels with accurate dissociation limit. The multi-reference configuration interaction method (MRCI) was used confirmed its rationality. The levels with high nu calculated in this paper agree with the result from the literature. Secondly, the electronic dipole moment surfaces (DMs) of (CO)-C-12-O-16 on the ground state at vibrational quantum number nu<63 under three kinds of electric fields were obtained using the multi-reference averaged coupled-pair functional (ACPF) theory combined with differential technology. Based on the above Revised-Morse potential function and DMs, the vibrational and transition levels up to the dissociation limit, and the transition moment, line strength, Einstein coefficient and intensity at room temperature with nu<63 were obtained by solving the one-dimensional Schrodinger equation, meanwhile, the spectral constants such as radiation lifetime and centrifugal distortion were also obtained. The calculated values are almost completely consistent with the results from the HITRAN. This paper not only reproduces the known spectral bands perfectly but also predicts hundreds of thousands of new spectral lines and some new spectral parameters, which can provide a reference for spectral detection. To establish the temperature measurement model based on (CO)-C-12-O-16, the partition function of temperature below 9 000 K was further investigated, and the rovibrational spectra at different temperatures were simulated. The variation of the spectral line with temperature was illustrated by the line spectrogram below 20 000 cm(-1) (logarithmic coordinate) and nu(0-1) band (linear coordinate). Several possible temperature measurement model schemes are proposed. Finally, the influence of pressure on the rovibrational line is discussed.