Cl2Elimination in 248 nm Photolysis of (COCl)2Probed with Cavity Ring-Down Absorption Spectroscopy.
Cavity ring-down absorption spectroscopy (CRDS) is employed to investigate one-photon dissociation of (COCl)2at 248 nm obtaining a primary Cl2elimination channel. A ratio of vibrational population is estimated to be 1:(0.12 ± 0.03):(0.011 ± 0.003) for the v = 0, 1, and 2 levels. The quantum yield of Cl2molecular channel is obtained to be 0.8 ± 0.4 initiated from the X̃1Agground state surface (COCl)2via internal conversion. The obtained total quantum yield is attributed to both primary ((COCl)2+ hν → 2CO + Cl2) and secondary reactions (dominated by Cl + COCl → Cl2+ CO). The former is estimated to share a yield of >0.14, while the latter contributes up to 0.66. The photodissociation pathway to the molecular products is calculated to proceed via a four-center transition state (TS) from which Cl2is eliminated synchronously. Installation of the mirrors with reflectivity of 99.995% in the CRDS apparatus prolongs the ring-down time to 70 μs, thus allowing for the contribution from 17% up to 66% of the total Cl2yield from secondary reaction depending on the reaction temperature. Despite uncertainty in determining the product yield, the primary Cl2dissociation channel eliminated from (COCl)2is observed for the first time.
Department of Chemistry, National Taiwan University, and Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 106, Taiwan.
Ting-Kang
TK
Huang
Department of Chemistry, National Taiwan University, and Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 106, Taiwan.
Bo-Jung
BJ
Chen
Department of Chemistry, National Taiwan University, and Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 106, Taiwan.
King-Chuen
http://orcid.org/0000-0002-4933-7566
KC
Lin
Department of Chemistry, National Dong Hwa University , Shoufeng, Hualien 974, Taiwan.
Lin
L
Lin
Department of Chemistry, National Dong Hwa University , Shoufeng, Hualien 974, Taiwan.
Bing-Jian
BJ
Sun
Department of Chemistry, National Dong Hwa University , Shoufeng, Hualien 974, Taiwan.
A H H
AHH
Chang