An isotopic-independent highly accurate potential energy surface for CO2 isotopologues and an initial (C16O2)-C-12 infrared line list

作者：Huang Xinchuan; Schwenke David W; Tashkun Sergey A; Lee Timothy J^*

来源：Journal of Chemical Physics, 2012, 136(12): 124311.

DOI：10.1063/1.3697540

An isotopic-independent, highly accurate potential energy surface (PES) has been determined for CO2 by refining a purely ab initio PES with selected, purely experimentally determined rovibrational energy levels. The purely ab initio PES is denoted Ames-0, while the refined PES is denoted Ames-1. Detailed tests are performed to demonstrate the spectroscopic accuracy of the Ames-1 PES. It is shown that Ames-1 yields sigma(rms) (root-mean-squares error) = 0.0156 cm(-1) for 6873 J = 0-117 (CO2)-C-12-O-16 experimental energy levels, even though less than 500 (CO2)-C-12-O-16 energy levels were included in the refinement procedure. It is also demonstrated that, without any additional refinement, Ames-1 yields very good agreement for isotopologues. Specifically, for the (CO2)-C-12-O-16 and (CO2)-C-13-O-16 isotopologues, spectroscopic constants G(nu) computed from Ames-1 are within +/- 0.01 and 0.02 cm(-1) of reliable experimentally derived values, while for the (OCO)-O-16-C-12-O-18, (OCO)-O-16-C-12-O-17, (OCO)-O-16-C-13-O-18, (OCO)-O-16-C-13-O-17, (CO2)-C-12-O-18, (OCO)-O-17-C-12-O-18, (CO2)-C-12-O-17, (CO2)-C-13-O-18, (CO2)-C-13-O-17, (OCO)-O-17-C-13-O-18, and (CO2)-C-14-O-16 isotopologues, the differences are between +/- 0.10 and 0.15 cm(-1). To our knowledge, this is the first time a polyatomic PES has been refined using such high J values, and this has led to new challenges in the refinement procedure. An initial high quality, purely ab initio dipole moment surface (DMS) is constructed and used to generate a 296 K line list. For most bands, experimental IR intensities are well reproduced for (CO2)-C-12-O-16 using Ames-1 and the DMS. For more than 80% of the bands, the experimental intensities are reproduced with sigma(rms)(Delta I) < 20% or srms(Delta I/delta(obs)) < 5. A few exceptions are analyzed and discussed. Directions for future improvements are discussed, though it is concluded that the current Ames-1 and the DMS should be useful in analyzing and assigning high-resolution laboratory or astronomical spectra.

• 出版日期2012-3-28