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Imaging the [1+1] Two-Photon Dissociation Dynamics of Br2+ in a Cold Ion Beam
Hao Liang, Zheng-fang Zhou, Ze-feng Hua, Yun-xiao Zhao, Shao-wen Feng, Yang Chen*, Dong-feng Zhao*
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 [1+1] two-photon dissociation dynamics of mass-selected 79Br2+ has been studied in acold ion beam using a cryogenic cylindrical ion trap velocity map imaging spectrometer. The quartet 14Σ-u,3/2 state of 79Br2+ is employed as an intermediate state to initiate resonance enhanced two-photon excitation to high-lying dissociative states in the 4.0-5.0 eV energy region above the ground rovibronic state. Total kinetic energy release (TKER) and the twodimensional recoiling velocity distributions of fragmented 79Br+ ions are measured using the technique of DC-slice velocity map imaging. Branching ratios for individual state-resolved product channels are determined from the TKER spectra. The measured photofragment angular distributions indicate that the dissociation of 79Br2+ occurs in dissociative Ω=3/2 state via ΔΩ=0 parallel transition from the 14Σ-u,3/2 intermediate state. Due to the considerable spin-orbit coupling effects in the excited states of 79Br2+, higher-lying dissociative quartet states are likely responsible for the observed photodissociation processes.
Key words:  Photodissociation dynamics, Br2+, Velocity map imaging, Ion trap
FundProject:
Br2+分子离子[1+1]双光子解离动力学
梁 昊, 周郑芳, 华泽丰, 赵云肖, 冯绍文, 陈 旸*, 赵东锋*
中国科学技术大学化学物理系,合肥微尺度物质科学国家研究中心,合肥 230026
摘要:
本文利用最近研制的低温离子阱-离子速度成像谱仪在冷离子束中研究了同位素质量分辨的79Br2+分子离子的[1+1]双光子激光解离动力学. 借助其14Σ-u,3/2态为中间态使79Br2+共振吸收两个光子至4∽5 eV区域的高激发态并发生解离. 利用离子速度成像技术获得了光解产物79Br+的二维速度分布和平动能释放谱. 通过平动能释放谱确定了不同解离能量处量子态分辨的解离产物通道分支比. 光碎片产物的角分布表明79Br2+分子离子的双光子解离是14Σ-u,3/2态的ΔΩ=0平行跃迁至一个Ω=3/2高解离态发生的. 由于分子激发态中的强自旋-轨道耦合作用,高激发的四重态很可能参与到实验观测的光解过程.
关键词:  光解动力学,Br2+,速度成像谱,离子阱
DOI:10.1063/1674-0068/cjcp1904085
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