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：

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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。