Photodissociation dynamics of CO 2 + hv → CO(X 1 Σ + ) + O( 1 D 2 ) via the 3P 1 Π u state

• Published in: The Journal of chemical physics 2022-02, Vol.156 (5), p.054302
• Main Authors: Zhang, Su'e, Wu, Yucheng, Zhang, Zhaoxue, Luo, Zijie, Zhao, Yarui, Li, Zhenxing, Chang, Yao, Yang, Jiayue, Wu, Guorong, Zhang, Weiqing, Yu, Shengrui, Yuan, Kaijun, Yang, Xueming
• Format: Article
• Language: English
• ISSN: 1089-7690

The vacuum ultraviolet (VUV) photodissociation of CO is important to understand the primary photochemical processes of CO induced by solar VUV excitation in the Earth's atmosphere. Here, we report a detailed study of vibrational-state-specific photodissociation dynamics of the CO(X Σ ) + O( D ) channel via the 3P Π state by using the time-sliced velocity-mapped ion imaging apparatus combined with the single VUV photoionization detection scheme. By recording the sliced images of the O( D ) photoproducts formed by VUV photoexcitation of CO to the individual vibrational structure of the 3P Π state, both the vibrational state distributions of the counterpart CO(X Σ ) photoproducts and the vibrational-state-specific product anisotropy parameters (β) are determined. The experimental results show that photodissociation of CO at 108.22, 107.50, 106.10, and 104.76 nm yields less anisotropic (β > 0) and inverted distributed CO(X Σ , v) photoproducts. The possible dissociation mechanism for the CO(X Σ ) + O( D ) channel may involve the non-adiabatic transition of excited CO from the initially prepared state to the 3 A' state with potential energy barriers. While at 108.82 and 107.35 nm, the vibrational distributions are found to have the population peaked at a low vibrational state, and the anisotropy parameters turn out to be negative. Such variation indicates the possibility of another non-adiabatic dissociation pathway that may involve Coriolis-type coupling to the low-lying dissociative state. These observations show sclear evidence of the influence of the initially vibrational excitations on the photodissociation dynamics of CO via the 3P Π state.