氯碘甲烷在A带的光解动力学(英文)

Photodissociation Dynamics of Chloroiodomethane in the A-Band

利用离子速度影像方法结合共振增强多光子电离(REMPI)技术研究了氯碘甲烷在A带的光解机理.从266和277nm的I*(5p2P1/2)和I(5p2P3/2)离子速度影像获得了碎片的平动能分布和角度分布.I和I*的平动能分布呈单高斯型,可用软自由基近似来解释.I和I*是在排斥的势能面上直接解离产生的.实验得到的各向异性参数β证实分子受激发后主要产生3Q0态,并且3Q0和1Q1态之间存在非绝热转移.波长越短,这种非绝热转移越强.在235nm附近,Cl和Cl*各向同性的离子影像说明氯原子来自于CH2ICl的二次解离过程,即CH2ICl先解离产生CH2Cl自由基,自由基再解离产生氯原子.

The photodissociation dynamics of chloroiodomethane in the A-band has been investigated by ion velocity imaging coupled with a resonance enhanced multiphoton ionization （REMPI） scheme. Translational energies and angular distributions of the corresponding photofragments were obtained by detecting ion images of I^＊（5p^2p1/2） and I （5p^2P3/2） at 266 and 277 rim. Single-peaked Gaussian translational energy distributions were found for I and I^＊ and could be interpreted in terms of the soft radical approximation. The formation of I and I^＊ took place via a fast direct dissociation process on a repulsive potential energy surface. The obtained anisotropy parameter β proved that the existence of a nonadiabatic transition between the ：^3Q0 and ^1Q1 states, and excitation at these wavelengths was predominated to the^ 3Q0 state. The nonadiabatic transition between the ^3Q0 and ^1Q1 states is stronger at shorter wavelengths. Around 235 nm, the isotropic Cl and Cl^＊ ion images suggest that the observed chlorine atoms come from the secondary UV photodissociation of CH2Cl radicals which are initially produced by the photodissociation of CH2ICl.