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Photodissociation of 2-Bromobutane at ~265 nm by Ion-velocity Map Imaging Technique
Dan-na Zhou, Rui Mao, Li-min Zhang, Qun Zhang, Yang Chen*
Hefei National Laboratory for Physical Sciences at the Microscale and Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China
Abstract:
The photodissociation dynamics of 2-bromobutane has been investigated at 264.77 and 264.86 nm by ion-velocity map imaging technique coupled with resonance-enhanced multi-photon ionization. The speed and angular distributions have been derived from the velocity map images of Br and Br*. The speed distributions of Br and Br* atoms in the photodis-sociation of 2-bromobutane at ~265 nm can be fitted using only one Gaussian function indicating that bromine fragments were produced via direct dissociation of C-Br bond. The contributions of the excited 3Q0, 3Q1, and 1Q1 states to the products (Br and Br*) were discussed. It is found that the nonadiabatic 1Q13Q0 transition plays an important role for Br photofragment in the dissociation of 2-C4H9Br at ~265 nm. Relative quantum yield of 0.621 for Br(2P3/2) at ~265 nm in the photodissociation of 2-bromobutane is derived. By comparing the photodissociation of 2-C4H9Br at ~265 nm and that that at ~234 nm, the anisotropy parameter β(Br) and β(Br*), and relative quantum yield ?(Br) decrease with increasing wavelength, the probability of curve crossing between 3Q0 and 1Q1 decreases with increasing laser wavelength.
Key words:  Ion-velocity imaging, Photodissociation, 2-Bromobutane
FundProject:
2-溴丁烷在约265 nm光解离的离子速度成像
周丹娜, 茆锐, 张立敏*, 张群*, 陈旸*
中国科学技术大学合肥微尺度物质科学国家实验室(筹),化学物理系,合肥230026
摘要:
用离子速度成像结合共振增强多光子电离技术研究了2-溴丁烷分子在264.77和264.86 nm(约265 nm)的光解离动力学.从获得的离子速度图像确定了光解产物Br和Br*碎片的速度分布和角度分布.其速度分布可以由一个窄的高斯分布拟合得到,它对应于沿着C-Br伸缩模式的直接解离.2-溴丁烷在约265nm的光解离中1Q13Q0的非绝热跃迁在Br离子碎片的产生中起到非常重要的作用, 确定Br(2P3/2)的相对量子产额为0.621.通过约265和约234 nm处2-溴丁烷光解的比较发现,各向异性参数和相对量子产率随着波长增加而下降,3Q01Q1态势能面交叉几率随着波长增加而降低
关键词:  2-溴丁烷,离子速度成像,光解离
DOI:10.1088/1674-0068/25/04/373-378
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