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Cavity Ring-Down Absorption Spectroscopy: Optical Characterization of ICl Product in Photodissociation of CH2ICl at 248 nm
The Journal of Physical Chemistry A ( IF 2.7 ) Pub Date : 2018-10-02 00:00:00 , DOI: 10.1021/acs.jpca.8b07012
Denís Paredes-Roibás,Muthiah Balaganesh,Toshio Kasai,José María Gavira-Vallejo,King Chuen Lin

Iodine monochloride (ICl) elimination from one-photon dissociation of CH2ICl at 248 nm is monitored by cavity ring-down absorption spectroscopy (CRDS). The spectrum of ICl is acquired in the transition of B3Π0 ← X1Σ+ and is confirmed to result from a primary photodissociation, that is, CH2ICl + hν → CH2 + ICl. The vibrational population ratio is determined with the aid of spectral simulation to be 1:(0.36 ± 0.10):(0.11 ± 0.05) for the vibrational levels ν = 0, 1, and 2 in the ground electronic state, corresponding to a Boltzmann-like vibrational temperature of 535 ± 69 K. The quantum yield of the ICl molecular channel for the reaction is obtained to be 0.052 ± 0.026 using a relative method in which the scheme CH2Br2 → CH2 + Br2 is adopted as the reference reaction. The ICl product contributed by the secondary collisions is minimized such that its quantum yield obtained is not overestimated. With the aid of the CCSD(T)//B3LYP/MIDI! level of theory, the ICl elimination from CH2ICl is evaluated to follow three pathways via either (1) a three-center transition state or (2) two isomerization transition states. However, the three-center concerted mechanism is verified to be unfavorable.

中文翻译:

腔衰荡吸收光谱:在248 nm CH 2 ICl光解中ICl产物的光学表征

通过腔衰荡吸收光谱法(CRDS)监测从248 nm CH 2 ICl的单光子离解中除去一氯化碘(ICl )。ICl的的频谱在B的过渡获取3 Π 0 ←X 1 Σ +和确认从主光解,即,CH导致2 ICl的+ ħ ν→CH 2+ ICl。借助于频谱模拟,对于处于地面电子状态的振动水平ν= 0、1和2,对应于玻尔兹曼常数,振动人口比率被确定为1:(0.36±0.10):( 0.11±0.05)。例如535±69 K的振动温度。使用相对方案(采用方案CH 2 Br 2 →CH 2 + Br 2作为参考)的相对方法获得的ICl分子通道的量子产率为0.052±0.026。反应。由二次碰撞贡献的ICl产物被最小化,从而不会高估获得的量子产率。借助CCSD(T)// B3LYP / MIDI!理论水平,从CH 2中消除ICl评估IC1通过(1)三中心过渡态或(2)两个异构化过渡态遵循三个途径。但是,三中心协调机制被证明是不利的。
更新日期:2018-10-02
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