CH2BrCl在265 nm光解产生的氯甲基自由基的振动内能

利用离子速度影像技术研究了CH2BrCl在265nm附近的激光光解.利用2+1共振增强多光子电离分别获得光解产物Br(2P1/2)和Br(2P3/2)的离子速度图像,从而得出Br(2P1/2)和Br(2P3/2)的速度分布,以及光解碎片的总平动能分布.据此,运用角动量守恒碰撞模型获得了解离氯甲基自由基(·CH2Cl)的振动内能分布.研究结果表明:CH2BrCl+hv→Br(2P1/2)+CH2Cl通道产生的氯甲基自由基中被激发的振动模主要是v4、v3+v4、v2+v4和v2+v6;CH2BrCl+hv→Br(2P3/2)+CH2Cl通道产生的氯甲基自由基中被激发的振动模主要是v2+v6、v1+v3、v2+v5、v2+v3+v5和v1+v5;母体分子CH2BrCl在吸收光解光子后除有v5(CBrstretch)振动模被激发外,还有v7(CH2a-stretch)等其它振动模也被激发.

Vibrational Internal Energy of Chloromethyl Radical Formed by the Photodissociation of CH2BrCl at 265 nm

Photodissociation of CH 2 BrCl was investigated around 265 nm using resonance-enhanced multiphoton ionization technique combined with velocity map ion-imaging detection.The ion images of Br(2 P 1/2)and Br(2 P 3/2)were analyzed to obtain the corresponding velocity distributions and total translational energy distributions.Using an impulsive model invoking angular momentum conservation,the vibrational internal energy distributions of chloromethyl radical(·CH 2 Cl)formed by the photodissociation of CH 2 BrCl,were derived from the total translational energy distributions.In the CH 2 BrCl+hv→Br(2 P 1/2)+CH 2 Cl channel,v 4,v 3+ v 4,v 2+ v 4 and v 2+ v 6 vibrational modes were found to be excited in the radical;while in the CH 2 BrCl+hv→ Br(2 P 3/2)+CH 2 Cl channel,the excited vibrational modes were v 2 +v 6,v 1 +v 3,v 2 +v 5,v 2 +v 3 +v 5,and v 1 +v 5.The results further implied that,following absorption of one photon by the parent molecule CH 2 BrCl,other vibrational modes besides v 5(CBr stretch)mode,such as v 7(CH 2 a-stretch)mode,are excited in the parent molecule.