Computational study of the ro-vibrational spectrum of CO–CO2

• Published in: The Journal of chemical physics Vol. 151; no. 8; pp. 084307 - 84317
• Main Authors: Castro-Juárez, Eduardo, Wang, Xiao-Gang, Carrington, Tucker, Quintas-Sánchez, Ernesto, Dawes, Richard
• Format: Journal Article
• Language: English
• Published: Melville American Institute of Physics 28.08.2019
• Subjects: Algorithms; Carbon dioxide; Carbon monoxide; Dimers; Energy levels; Isomers; Potential energy; Rotational states; T shape; Vibrational states; Wave functions
• ISSN: 0021-9606; 1089-7690; 1089-7690
• DOI: 10.1063/1.5119762

An accurate ab initio ground-state intermolecular potential energy surface (PES) was determined for the CO–CO2 van der Waals dimer. The Lanczos algorithm was used to compute rovibrational energies on this PES. For both the C-in and O-in T-shaped isomers, the fundamental transition frequencies agree well with previous experimental results. We confirm that the in-plane states previously observed are geared states. In addition, we have computed and assigned many other vibrational states. The rotational constants we determine from J = 1 energy levels agree well with their experimental counterparts. Planar and out-of-plane cuts of some of the wavefunctions we compute are quite different, indicating strong coupling between the bend and torsional modes. Because the stable isomers are T-shaped, vibration along the out-of-plane coordinates is very floppy. In CO–CO2, when the molecule is out-of-plane, interconversion of the isomers is possible, but the barrier height is higher than the in-plane geared barrier height.