A new potential energy surface and rovibrational spectra of the CO–CO2 complex: Dependence on the antisymmetric stretching vibration of CO2

Abstract

We present a new ab initio five-dimensional potential energy surface for the CO-CO2 complex containing the Q3 normal mode for the ν3 asymmetric stretching vibration of the CO2 unit. The potential was calculated by supermolecular approach at the CCSD(T)-F12 level with aug-cc-pVTZ basis set plus midpoint bond functions. Two vibrationally averaged four-dimensional potentials for CO-CO2 with CO2 in the ground and ν3 excited states were generated by the integration of the five-dimensional potential over the Q3 intramolecular coordinate. Each potential displays a T-shaped global minimum with the C end in the CO unit pointing toward the C atom in the CO2 unit and a T-shaped local minimum but with the CO monomer rotated by 180º. The rovibrational bound states and energy levels for the CO-CO2 dimer were obtained employing the radial discrete variable representation (DVR)/angular finite basis representation (FBR) method in conjunction with the Lanczos algorithm. The vibrational ground and some lower excited states for CO-CO2 are localized around the global minimum because of the higher potential barriers. The band origin is blueshifted by 0.2089 cm-1 for CO-CO2 in the CO2 ν3 range, which is consistent with the experimental result of 0.211 cm-1. The geared bending vibrational frequencies for CO-CO2 are 24.7101 and 24.5549 cm-1 at the ground and ν3 excited states of CO2, respectively. The predicted rovibrational frequencies as well as spectral constants coincide with the available observations, and these parameters show the CO-CO2 complex is a nearly prolate asymmetric rotor.

A New Ab Initio Potential Energy Surface and Rovibrational Spectra for the CO–N2O Complex

“…For the radial R part, the sine-DVR approach was employed, and 60 sine-DVR grid points were chosen. In case of the angular part, the parity-adapted rotational basis function was utilized which was expressed as the following equation , .25ex2ex | j 1 , j 2 , m , K ; J M P false⟩ = false( 2 + 2 δ K 0 δ m 0 false) − 1 / 2 × [ D M K J Y j 1 m false( θ 1 , ϕ false) normalΘ j 2 , K − m false( θ 2 false) + ( − 1 ) J + P D M − K J Y j 1 − m false( θ 1 , ϕ false) normalΘ j 2 , m − K false( θ 2 false) false] where D MK J serves as the normalized rotation function. Y j 1 m and Θ j 2 , K – m are separately the spherical harmonic function and the related Legendre polynomials.…”

“…For the radial R part, the sine-DVR 41 approach was employed, and 60 sine-DVR grid points were chosen. In case of the angular part, the parity-adapted rotational basis function was utilized which was expressed as the following equation 42,43 The…”

“…For the radial R part, the sine-DVR approach was employed, and 60 sine-DVR grid points were chosen. In case of the angular part, the parity-adapted rotational basis function was utilized which was expressed as the following equation , where D MK J serves as the normalized rotation function. Y j 1 m and Θ j 2 , K – m are separately the spherical harmonic function and the related Legendre polynomials.…”