Photochemistry of carbon dioxide from first principles: Application to photoabsorption of hot CO2

- A computational framework is developed for the UV light induced photodynamics of CO2.
- Temperature and wavelength dependent absorption spectra are found for λ ≤ 250 nm and T ≤ 2500 K.
- The results overlap well with existing experimental findings.
- The framework allows extensions to dissociation and photoemission yields of CO2.

This paper analyzes the temperature dependence of the absorption spectrum of carbon dioxide in the wavelength range λ ≤ 250 nm by means of a first principles model. The model combines the high level ab initio potential energy surfaces of four excited electronic states and their coordinate dependent transition dipole moment vectors with quantum mechanical calculations of the photodissociation dynamics and the absorption spectra corresponding to excitations from many initial rovibrational states of the parent CO2. The calculations demonstrate that photodynamics from first principles can be realized for CO2 with high accuracy: The absorption cross section can be reliably calculated for λ ≤ 250 nm and T ≤ 2500 K and used for modeling the one-step photolytic reduction of CO2 to CO. An ab initio-based estimate of the contribution of low lying triplet states to the optical absorption of hot CO2 is also given.

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