https://scholars.lib.ntu.edu.tw/handle/123456789/575797
標題: | Probing BrCl from photodissociation of CH2BrCl and CHBr2Cl at 248 nm using cavity ring-down spectroscopy | 作者: | Muthiah B Kasai T Lin K.-C. KING-CHUEN LIN |
關鍵字: | Absorption spectroscopy; Chlorine compounds; Light measurement; Photodissociation; Photolysis; Potential energy; Quantum chemistry; Rate constants; Branching ratio; Cavity ring down spectroscopies; Cavity ring-down; Dissociation pathways; Rotational lines; Transition state; Vibrational levels; Wavelength ranges; Bromine compounds; ab initio calculation; absorption spectroscopy; article; cavity ring down spectroscopy; conformational transition; dissociation; halogenation; photolysis; quantum yield; rate constant; simulation | 公開日期: | 2021 | 卷: | 23 | 期: | 10 | 起(迄)頁: | 6098-6106 | 來源出版物: | Physical Chemistry Chemical Physics | 摘要: | Photodissociation of di- and tri-halogenated methanes including CH2BrCl and CHBr2Cl at 248 nm was investigated using cavity ringdown absorption spectroscopy (CRDS). The spectra of the BrCl(v′′ = 2, 3) and Br2(v′′ = 1, 2) fragments were probed over the wavelength range of 594.5-596 nm in the B3Π+0u← X1Σ+gand B3Π (0+) ← X1Σ+transitions, respectively. Their corresponding spectra were simulated for assignment of rotational lines at a given vibrational level. The quantum yields for Br2eliminated from CHBr2Cl and BrCl from CH2BrCl were determined to be 0.048 ± 0.018 and 0.037 ± 0.014, respectively. The photodissociation of CHBr2Cl yielded only the Br2fragment, but not the BrCl fragment in the experiments. Anab initiotheoretical method based on the CCSD(T)//B3LYP/6-311g(d,p) level was employed to evaluate the potential energy surface for the dissociation pathways to produce Br2and BrCl from CHBr2Cl, which encountered a transition state barrier of 445 and 484 kJ mol?1, respectively. The corresponding RRKM rate constants were calculated to show that the branching ratio of (Br2/BrCl) is ?20. The BrCl spectrum is expected to be obscured by the much larger Br2spectrum, explaining why BrCl fragments cannot be detected in the photolysis of CHBr2Cl. ? the Owner Societies 2021. |
URI: | https://www.scopus.com/inward/record.uri?eid=2-s2.0-85102968925&doi=10.1039%2fd0cp06350a&partnerID=40&md5=3712b8125fa5ff4dd977be538d2a3647 https://scholars.lib.ntu.edu.tw/handle/123456789/575797 |
ISSN: | 14639076 | DOI: | 10.1039/d0cp06350a |
顯示於: | 化學系 |
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